1e52347bdSJani Nikula acpi= [HW,ACPI,X86,ARM64] 2e52347bdSJani Nikula Advanced Configuration and Power Interface 3e52347bdSJani Nikula Format: { force | on | off | strict | noirq | rsdt | 4e52347bdSJani Nikula copy_dsdt } 5e52347bdSJani Nikula force -- enable ACPI if default was off 6e52347bdSJani Nikula on -- enable ACPI but allow fallback to DT [arm64] 7e52347bdSJani Nikula off -- disable ACPI if default was on 8e52347bdSJani Nikula noirq -- do not use ACPI for IRQ routing 9e52347bdSJani Nikula strict -- Be less tolerant of platforms that are not 10e52347bdSJani Nikula strictly ACPI specification compliant. 11e52347bdSJani Nikula rsdt -- prefer RSDT over (default) XSDT 12e52347bdSJani Nikula copy_dsdt -- copy DSDT to memory 13e52347bdSJani Nikula For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force" 14e52347bdSJani Nikula are available 15e52347bdSJani Nikula 16151f4e2bSMauro Carvalho Chehab See also Documentation/power/runtime_pm.rst, pci=noacpi 17e52347bdSJani Nikula 18e52347bdSJani Nikula acpi_apic_instance= [ACPI, IOAPIC] 19e52347bdSJani Nikula Format: <int> 20e52347bdSJani Nikula 2: use 2nd APIC table, if available 21e52347bdSJani Nikula 1,0: use 1st APIC table 22e52347bdSJani Nikula default: 0 23e52347bdSJani Nikula 24e52347bdSJani Nikula acpi_backlight= [HW,ACPI] 255fd769c2SRandy Dunlap { vendor | video | native | none } 265fd769c2SRandy Dunlap If set to vendor, prefer vendor-specific driver 27e52347bdSJani Nikula (e.g. thinkpad_acpi, sony_acpi, etc.) instead 28e52347bdSJani Nikula of the ACPI video.ko driver. 295fd769c2SRandy Dunlap If set to video, use the ACPI video.ko driver. 305fd769c2SRandy Dunlap If set to native, use the device's native backlight mode. 315fd769c2SRandy Dunlap If set to none, disable the ACPI backlight interface. 32e52347bdSJani Nikula 33e52347bdSJani Nikula acpi_force_32bit_fadt_addr 34e52347bdSJani Nikula force FADT to use 32 bit addresses rather than the 35e52347bdSJani Nikula 64 bit X_* addresses. Some firmware have broken 64 36e52347bdSJani Nikula bit addresses for force ACPI ignore these and use 37e52347bdSJani Nikula the older legacy 32 bit addresses. 38e52347bdSJani Nikula 39e52347bdSJani Nikula acpica_no_return_repair [HW, ACPI] 40e52347bdSJani Nikula Disable AML predefined validation mechanism 41e52347bdSJani Nikula This mechanism can repair the evaluation result to make 42e52347bdSJani Nikula the return objects more ACPI specification compliant. 43e52347bdSJani Nikula This option is useful for developers to identify the 44e52347bdSJani Nikula root cause of an AML interpreter issue when the issue 45e52347bdSJani Nikula has something to do with the repair mechanism. 46e52347bdSJani Nikula 47e52347bdSJani Nikula acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] 48e52347bdSJani Nikula acpi.debug_level= [HW,ACPI,ACPI_DEBUG] 49e52347bdSJani Nikula Format: <int> 50e52347bdSJani Nikula CONFIG_ACPI_DEBUG must be enabled to produce any ACPI 51e52347bdSJani Nikula debug output. Bits in debug_layer correspond to a 52e52347bdSJani Nikula _COMPONENT in an ACPI source file, e.g., 53866d6cdfSRafael J. Wysocki #define _COMPONENT ACPI_EVENTS 54e52347bdSJani Nikula Bits in debug_level correspond to a level in 55e52347bdSJani Nikula ACPI_DEBUG_PRINT statements, e.g., 56e52347bdSJani Nikula ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... 57e52347bdSJani Nikula The debug_level mask defaults to "info". See 58cb1aaebeSMauro Carvalho Chehab Documentation/firmware-guide/acpi/debug.rst for more information about 59e52347bdSJani Nikula debug layers and levels. 60e52347bdSJani Nikula 61e52347bdSJani Nikula Enable processor driver info messages: 62e52347bdSJani Nikula acpi.debug_layer=0x20000000 63e52347bdSJani Nikula Enable AML "Debug" output, i.e., stores to the Debug 64e52347bdSJani Nikula object while interpreting AML: 65e52347bdSJani Nikula acpi.debug_layer=0xffffffff acpi.debug_level=0x2 66e52347bdSJani Nikula Enable all messages related to ACPI hardware: 67e52347bdSJani Nikula acpi.debug_layer=0x2 acpi.debug_level=0xffffffff 68e52347bdSJani Nikula 69e52347bdSJani Nikula Some values produce so much output that the system is 70e52347bdSJani Nikula unusable. The "log_buf_len" parameter may be useful 71e52347bdSJani Nikula if you need to capture more output. 72e52347bdSJani Nikula 73e52347bdSJani Nikula acpi_enforce_resources= [ACPI] 74e52347bdSJani Nikula { strict | lax | no } 75e52347bdSJani Nikula Check for resource conflicts between native drivers 76e52347bdSJani Nikula and ACPI OperationRegions (SystemIO and SystemMemory 77e52347bdSJani Nikula only). IO ports and memory declared in ACPI might be 78e52347bdSJani Nikula used by the ACPI subsystem in arbitrary AML code and 79e52347bdSJani Nikula can interfere with legacy drivers. 80e52347bdSJani Nikula strict (default): access to resources claimed by ACPI 81e52347bdSJani Nikula is denied; legacy drivers trying to access reserved 82e52347bdSJani Nikula resources will fail to bind to device using them. 83e52347bdSJani Nikula lax: access to resources claimed by ACPI is allowed; 84e52347bdSJani Nikula legacy drivers trying to access reserved resources 85e52347bdSJani Nikula will bind successfully but a warning message is logged. 86e52347bdSJani Nikula no: ACPI OperationRegions are not marked as reserved, 87e52347bdSJani Nikula no further checks are performed. 88e52347bdSJani Nikula 89e52347bdSJani Nikula acpi_force_table_verification [HW,ACPI] 90e52347bdSJani Nikula Enable table checksum verification during early stage. 91e52347bdSJani Nikula By default, this is disabled due to x86 early mapping 92e52347bdSJani Nikula size limitation. 93e52347bdSJani Nikula 94e52347bdSJani Nikula acpi_irq_balance [HW,ACPI] 95e52347bdSJani Nikula ACPI will balance active IRQs 96e52347bdSJani Nikula default in APIC mode 97e52347bdSJani Nikula 98e52347bdSJani Nikula acpi_irq_nobalance [HW,ACPI] 99e52347bdSJani Nikula ACPI will not move active IRQs (default) 100e52347bdSJani Nikula default in PIC mode 101e52347bdSJani Nikula 102e52347bdSJani Nikula acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 103e52347bdSJani Nikula Format: <irq>,<irq>... 104e52347bdSJani Nikula 105e52347bdSJani Nikula acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 106e52347bdSJani Nikula use by PCI 107e52347bdSJani Nikula Format: <irq>,<irq>... 108e52347bdSJani Nikula 1099c4aa1eeSLv Zheng acpi_mask_gpe= [HW,ACPI] 1109c4aa1eeSLv Zheng Due to the existence of _Lxx/_Exx, some GPEs triggered 1119c4aa1eeSLv Zheng by unsupported hardware/firmware features can result in 1129c4aa1eeSLv Zheng GPE floodings that cannot be automatically disabled by 1139c4aa1eeSLv Zheng the GPE dispatcher. 1149c4aa1eeSLv Zheng This facility can be used to prevent such uncontrolled 1159c4aa1eeSLv Zheng GPE floodings. 116d3121e64SAndy Shevchenko Format: <byte> or <bitmap-list> 1179c4aa1eeSLv Zheng 118e52347bdSJani Nikula acpi_no_auto_serialize [HW,ACPI] 119e52347bdSJani Nikula Disable auto-serialization of AML methods 120e52347bdSJani Nikula AML control methods that contain the opcodes to create 121e52347bdSJani Nikula named objects will be marked as "Serialized" by the 122e52347bdSJani Nikula auto-serialization feature. 123e52347bdSJani Nikula This feature is enabled by default. 124e52347bdSJani Nikula This option allows to turn off the feature. 125e52347bdSJani Nikula 126e52347bdSJani Nikula acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump 127e52347bdSJani Nikula kernels. 128e52347bdSJani Nikula 129e52347bdSJani Nikula acpi_no_static_ssdt [HW,ACPI] 130e52347bdSJani Nikula Disable installation of static SSDTs at early boot time 131e52347bdSJani Nikula By default, SSDTs contained in the RSDT/XSDT will be 132e52347bdSJani Nikula installed automatically and they will appear under 133e52347bdSJani Nikula /sys/firmware/acpi/tables. 134e52347bdSJani Nikula This option turns off this feature. 135e52347bdSJani Nikula Note that specifying this option does not affect 136e52347bdSJani Nikula dynamic table installation which will install SSDT 137e52347bdSJani Nikula tables to /sys/firmware/acpi/tables/dynamic. 138e52347bdSJani Nikula 1393f9e12e0SJean Delvare acpi_no_watchdog [HW,ACPI,WDT] 1403f9e12e0SJean Delvare Ignore the ACPI-based watchdog interface (WDAT) and let 1413f9e12e0SJean Delvare a native driver control the watchdog device instead. 1423f9e12e0SJean Delvare 143e52347bdSJani Nikula acpi_rsdp= [ACPI,EFI,KEXEC] 144e52347bdSJani Nikula Pass the RSDP address to the kernel, mostly used 145e52347bdSJani Nikula on machines running EFI runtime service to boot the 146e52347bdSJani Nikula second kernel for kdump. 147e52347bdSJani Nikula 148e52347bdSJani Nikula acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 149e52347bdSJani Nikula Format: To spoof as Windows 98: ="Microsoft Windows" 150e52347bdSJani Nikula 151e52347bdSJani Nikula acpi_rev_override [ACPI] Override the _REV object to return 5 (instead 152e52347bdSJani Nikula of 2 which is mandated by ACPI 6) as the supported ACPI 153e52347bdSJani Nikula specification revision (when using this switch, it may 154e52347bdSJani Nikula be necessary to carry out a cold reboot _twice_ in a 155e52347bdSJani Nikula row to make it take effect on the platform firmware). 156e52347bdSJani Nikula 157e52347bdSJani Nikula acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 158e52347bdSJani Nikula acpi_osi="string1" # add string1 159e52347bdSJani Nikula acpi_osi="!string2" # remove string2 160e52347bdSJani Nikula acpi_osi=!* # remove all strings 161e52347bdSJani Nikula acpi_osi=! # disable all built-in OS vendor 162e52347bdSJani Nikula strings 163e52347bdSJani Nikula acpi_osi=!! # enable all built-in OS vendor 164e52347bdSJani Nikula strings 165e52347bdSJani Nikula acpi_osi= # disable all strings 166e52347bdSJani Nikula 167e52347bdSJani Nikula 'acpi_osi=!' can be used in combination with single or 168e52347bdSJani Nikula multiple 'acpi_osi="string1"' to support specific OS 169e52347bdSJani Nikula vendor string(s). Note that such command can only 170e52347bdSJani Nikula affect the default state of the OS vendor strings, thus 171e52347bdSJani Nikula it cannot affect the default state of the feature group 172e52347bdSJani Nikula strings and the current state of the OS vendor strings, 173e52347bdSJani Nikula specifying it multiple times through kernel command line 174e52347bdSJani Nikula is meaningless. This command is useful when one do not 175e52347bdSJani Nikula care about the state of the feature group strings which 176e52347bdSJani Nikula should be controlled by the OSPM. 177e52347bdSJani Nikula Examples: 178e52347bdSJani Nikula 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent 179e52347bdSJani Nikula to 'acpi_osi="Windows 2000" acpi_osi=!', they all 180e52347bdSJani Nikula can make '_OSI("Windows 2000")' TRUE. 181e52347bdSJani Nikula 182e52347bdSJani Nikula 'acpi_osi=' cannot be used in combination with other 183e52347bdSJani Nikula 'acpi_osi=' command lines, the _OSI method will not 184e52347bdSJani Nikula exist in the ACPI namespace. NOTE that such command can 185e52347bdSJani Nikula only affect the _OSI support state, thus specifying it 186e52347bdSJani Nikula multiple times through kernel command line is also 187e52347bdSJani Nikula meaningless. 188e52347bdSJani Nikula Examples: 189e52347bdSJani Nikula 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' 190e52347bdSJani Nikula FALSE. 191e52347bdSJani Nikula 192e52347bdSJani Nikula 'acpi_osi=!*' can be used in combination with single or 193e52347bdSJani Nikula multiple 'acpi_osi="string1"' to support specific 194e52347bdSJani Nikula string(s). Note that such command can affect the 195e52347bdSJani Nikula current state of both the OS vendor strings and the 196e52347bdSJani Nikula feature group strings, thus specifying it multiple times 197e52347bdSJani Nikula through kernel command line is meaningful. But it may 198e52347bdSJani Nikula still not able to affect the final state of a string if 199e52347bdSJani Nikula there are quirks related to this string. This command 200e52347bdSJani Nikula is useful when one want to control the state of the 201e52347bdSJani Nikula feature group strings to debug BIOS issues related to 202e52347bdSJani Nikula the OSPM features. 203e52347bdSJani Nikula Examples: 204e52347bdSJani Nikula 1. 'acpi_osi="Module Device" acpi_osi=!*' can make 205e52347bdSJani Nikula '_OSI("Module Device")' FALSE. 206e52347bdSJani Nikula 2. 'acpi_osi=!* acpi_osi="Module Device"' can make 207e52347bdSJani Nikula '_OSI("Module Device")' TRUE. 208e52347bdSJani Nikula 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is 209e52347bdSJani Nikula equivalent to 210e52347bdSJani Nikula 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' 211e52347bdSJani Nikula and 212e52347bdSJani Nikula 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', 213e52347bdSJani Nikula they all will make '_OSI("Windows 2000")' TRUE. 214e52347bdSJani Nikula 215e52347bdSJani Nikula acpi_pm_good [X86] 216e52347bdSJani Nikula Override the pmtimer bug detection: force the kernel 217e52347bdSJani Nikula to assume that this machine's pmtimer latches its value 218e52347bdSJani Nikula and always returns good values. 219e52347bdSJani Nikula 220e52347bdSJani Nikula acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 221e52347bdSJani Nikula Format: { level | edge | high | low } 222e52347bdSJani Nikula 223e52347bdSJani Nikula acpi_skip_timer_override [HW,ACPI] 224e52347bdSJani Nikula Recognize and ignore IRQ0/pin2 Interrupt Override. 225e52347bdSJani Nikula For broken nForce2 BIOS resulting in XT-PIC timer. 226e52347bdSJani Nikula 227e52347bdSJani Nikula acpi_sleep= [HW,ACPI] Sleep options 228*74d95555SDavid Woodhouse Format: { s3_bios, s3_mode, s3_beep, s4_hwsig, 229*74d95555SDavid Woodhouse s4_nohwsig, old_ordering, nonvs, 230*74d95555SDavid Woodhouse sci_force_enable, nobl } 231151f4e2bSMauro Carvalho Chehab See Documentation/power/video.rst for information on 232e52347bdSJani Nikula s3_bios and s3_mode. 233e52347bdSJani Nikula s3_beep is for debugging; it makes the PC's speaker beep 234e52347bdSJani Nikula as soon as the kernel's real-mode entry point is called. 235*74d95555SDavid Woodhouse s4_hwsig causes the kernel to check the ACPI hardware 236*74d95555SDavid Woodhouse signature during resume from hibernation, and gracefully 237*74d95555SDavid Woodhouse refuse to resume if it has changed. This complies with 238*74d95555SDavid Woodhouse the ACPI specification but not with reality, since 239*74d95555SDavid Woodhouse Windows does not do this and many laptops do change it 240*74d95555SDavid Woodhouse on docking. So the default behaviour is to allow resume 241*74d95555SDavid Woodhouse and simply warn when the signature changes, unless the 242*74d95555SDavid Woodhouse s4_hwsig option is enabled. 243e52347bdSJani Nikula s4_nohwsig prevents ACPI hardware signature from being 244*74d95555SDavid Woodhouse used (or even warned about) during resume. 245e52347bdSJani Nikula old_ordering causes the ACPI 1.0 ordering of the _PTS 246e52347bdSJani Nikula control method, with respect to putting devices into 247e52347bdSJani Nikula low power states, to be enforced (the ACPI 2.0 ordering 248e52347bdSJani Nikula of _PTS is used by default). 249e52347bdSJani Nikula nonvs prevents the kernel from saving/restoring the 250e52347bdSJani Nikula ACPI NVS memory during suspend/hibernation and resume. 251e52347bdSJani Nikula sci_force_enable causes the kernel to set SCI_EN directly 252e52347bdSJani Nikula on resume from S1/S3 (which is against the ACPI spec, 253e52347bdSJani Nikula but some broken systems don't work without it). 25457044031SRafael J. Wysocki nobl causes the internal blacklist of systems known to 25557044031SRafael J. Wysocki behave incorrectly in some ways with respect to system 25657044031SRafael J. Wysocki suspend and resume to be ignored (use wisely). 257e52347bdSJani Nikula 258e52347bdSJani Nikula acpi_use_timer_override [HW,ACPI] 259e52347bdSJani Nikula Use timer override. For some broken Nvidia NF5 boards 260e52347bdSJani Nikula that require a timer override, but don't have HPET 261e52347bdSJani Nikula 262e52347bdSJani Nikula add_efi_memmap [EFI; X86] Include EFI memory map in 263e52347bdSJani Nikula kernel's map of available physical RAM. 264e52347bdSJani Nikula 265e52347bdSJani Nikula agp= [AGP] 266e52347bdSJani Nikula { off | try_unsupported } 267e52347bdSJani Nikula off: disable AGP support 268e52347bdSJani Nikula try_unsupported: try to drive unsupported chipsets 269e52347bdSJani Nikula (may crash computer or cause data corruption) 270e52347bdSJani Nikula 271e52347bdSJani Nikula ALSA [HW,ALSA] 2721ca2c806SMauro Carvalho Chehab See Documentation/sound/alsa-configuration.rst 273e52347bdSJani Nikula 274e52347bdSJani Nikula alignment= [KNL,ARM] 275e52347bdSJani Nikula Allow the default userspace alignment fault handler 276e52347bdSJani Nikula behaviour to be specified. Bit 0 enables warnings, 277e52347bdSJani Nikula bit 1 enables fixups, and bit 2 sends a segfault. 278e52347bdSJani Nikula 279e52347bdSJani Nikula align_va_addr= [X86-64] 280e52347bdSJani Nikula Align virtual addresses by clearing slice [14:12] when 281e52347bdSJani Nikula allocating a VMA at process creation time. This option 282e52347bdSJani Nikula gives you up to 3% performance improvement on AMD F15h 283e52347bdSJani Nikula machines (where it is enabled by default) for a 284e52347bdSJani Nikula CPU-intensive style benchmark, and it can vary highly in 285e52347bdSJani Nikula a microbenchmark depending on workload and compiler. 286e52347bdSJani Nikula 287e52347bdSJani Nikula 32: only for 32-bit processes 288e52347bdSJani Nikula 64: only for 64-bit processes 289e52347bdSJani Nikula on: enable for both 32- and 64-bit processes 290e52347bdSJani Nikula off: disable for both 32- and 64-bit processes 291e52347bdSJani Nikula 292e52347bdSJani Nikula alloc_snapshot [FTRACE] 293e52347bdSJani Nikula Allocate the ftrace snapshot buffer on boot up when the 294e52347bdSJani Nikula main buffer is allocated. This is handy if debugging 295e52347bdSJani Nikula and you need to use tracing_snapshot() on boot up, and 296e52347bdSJani Nikula do not want to use tracing_snapshot_alloc() as it needs 297e52347bdSJani Nikula to be done where GFP_KERNEL allocations are allowed. 298e52347bdSJani Nikula 299ead7de46SWill Deacon allow_mismatched_32bit_el0 [ARM64] 300ead7de46SWill Deacon Allow execve() of 32-bit applications and setting of the 301ead7de46SWill Deacon PER_LINUX32 personality on systems where only a strict 302ead7de46SWill Deacon subset of the CPUs support 32-bit EL0. When this 303ead7de46SWill Deacon parameter is present, the set of CPUs supporting 32-bit 304ead7de46SWill Deacon EL0 is indicated by /sys/devices/system/cpu/aarch32_el0 305ead7de46SWill Deacon and hot-unplug operations may be restricted. 306ead7de46SWill Deacon 307702f4387SWill Deacon See Documentation/arm64/asymmetric-32bit.rst for more 308702f4387SWill Deacon information. 309702f4387SWill Deacon 310e52347bdSJani Nikula amd_iommu= [HW,X86-64] 311e52347bdSJani Nikula Pass parameters to the AMD IOMMU driver in the system. 312e52347bdSJani Nikula Possible values are: 3131d479f16SJohn Garry fullflush - Deprecated, equivalent to iommu.strict=1 314e52347bdSJani Nikula off - do not initialize any AMD IOMMU found in 315e52347bdSJani Nikula the system 316e52347bdSJani Nikula force_isolation - Force device isolation for all 317e52347bdSJani Nikula devices. The IOMMU driver is not 318e52347bdSJani Nikula allowed anymore to lift isolation 319e52347bdSJani Nikula requirements as needed. This option 320e52347bdSJani Nikula does not override iommu=pt 321b1e650dbSJoerg Roedel force_enable - Force enable the IOMMU on platforms known 322b1e650dbSJoerg Roedel to be buggy with IOMMU enabled. Use this 323b1e650dbSJoerg Roedel option with care. 324e52347bdSJani Nikula 325e52347bdSJani Nikula amd_iommu_dump= [HW,X86-64] 326e52347bdSJani Nikula Enable AMD IOMMU driver option to dump the ACPI table 327e52347bdSJani Nikula for AMD IOMMU. With this option enabled, AMD IOMMU 328e52347bdSJani Nikula driver will print ACPI tables for AMD IOMMU during 329e52347bdSJani Nikula IOMMU initialization. 330e52347bdSJani Nikula 331e52347bdSJani Nikula amd_iommu_intr= [HW,X86-64] 332e52347bdSJani Nikula Specifies one of the following AMD IOMMU interrupt 333e52347bdSJani Nikula remapping modes: 334e52347bdSJani Nikula legacy - Use legacy interrupt remapping mode. 335e52347bdSJani Nikula vapic - Use virtual APIC mode, which allows IOMMU 336e52347bdSJani Nikula to inject interrupts directly into guest. 337e52347bdSJani Nikula This mode requires kvm-amd.avic=1. 338e52347bdSJani Nikula (Default when IOMMU HW support is present.) 339e52347bdSJani Nikula 340e52347bdSJani Nikula amijoy.map= [HW,JOY] Amiga joystick support 341e52347bdSJani Nikula Map of devices attached to JOY0DAT and JOY1DAT 342e52347bdSJani Nikula Format: <a>,<b> 3431752118dSTom Saeger See also Documentation/input/joydev/joystick.rst 344e52347bdSJani Nikula 345e52347bdSJani Nikula analog.map= [HW,JOY] Analog joystick and gamepad support 346e52347bdSJani Nikula Specifies type or capabilities of an analog joystick 347e52347bdSJani Nikula connected to one of 16 gameports 348e52347bdSJani Nikula Format: <type1>,<type2>,..<type16> 349e52347bdSJani Nikula 350e52347bdSJani Nikula apc= [HW,SPARC] 351e52347bdSJani Nikula Power management functions (SPARCstation-4/5 + deriv.) 352e52347bdSJani Nikula Format: noidle 353e52347bdSJani Nikula Disable APC CPU standby support. SPARCstation-Fox does 354e52347bdSJani Nikula not play well with APC CPU idle - disable it if you have 355e52347bdSJani Nikula APC and your system crashes randomly. 356e52347bdSJani Nikula 35764e05d11SDou Liyang apic= [APIC,X86] Advanced Programmable Interrupt Controller 358806654a9SWill Deacon Change the output verbosity while booting 359e52347bdSJani Nikula Format: { quiet (default) | verbose | debug } 360e52347bdSJani Nikula Change the amount of debugging information output 361e52347bdSJani Nikula when initialising the APIC and IO-APIC components. 36264e05d11SDou Liyang For X86-32, this can also be used to specify an APIC 36364e05d11SDou Liyang driver name. 36464e05d11SDou Liyang Format: apic=driver_name 36564e05d11SDou Liyang Examples: apic=bigsmp 366e52347bdSJani Nikula 367e52347bdSJani Nikula apic_extnmi= [APIC,X86] External NMI delivery setting 368e52347bdSJani Nikula Format: { bsp (default) | all | none } 369e52347bdSJani Nikula bsp: External NMI is delivered only to CPU 0 370e52347bdSJani Nikula all: External NMIs are broadcast to all CPUs as a 371e52347bdSJani Nikula backup of CPU 0 372e52347bdSJani Nikula none: External NMI is masked for all CPUs. This is 373e52347bdSJani Nikula useful so that a dump capture kernel won't be 374e52347bdSJani Nikula shot down by NMI 375e52347bdSJani Nikula 376e52347bdSJani Nikula autoconf= [IPV6] 37719093313SMauro Carvalho Chehab See Documentation/networking/ipv6.rst. 378e52347bdSJani Nikula 379e52347bdSJani Nikula show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller 380e52347bdSJani Nikula Limit apic dumping. The parameter defines the maximal 381e52347bdSJani Nikula number of local apics being dumped. Also it is possible 382e52347bdSJani Nikula to set it to "all" by meaning -- no limit here. 383e52347bdSJani Nikula Format: { 1 (default) | 2 | ... | all }. 384e52347bdSJani Nikula The parameter valid if only apic=debug or 385e52347bdSJani Nikula apic=verbose is specified. 386e52347bdSJani Nikula Example: apic=debug show_lapic=all 387e52347bdSJani Nikula 388e52347bdSJani Nikula apm= [APM] Advanced Power Management 389e52347bdSJani Nikula See header of arch/x86/kernel/apm_32.c. 390e52347bdSJani Nikula 391e52347bdSJani Nikula arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 392e52347bdSJani Nikula Format: <io>,<irq>,<nodeID> 393e52347bdSJani Nikula 39493ad55b7SMarc Zyngier arm64.nobti [ARM64] Unconditionally disable Branch Target 39593ad55b7SMarc Zyngier Identification support 39693ad55b7SMarc Zyngier 397f8da5752SMarc Zyngier arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication 398f8da5752SMarc Zyngier support 399f8da5752SMarc Zyngier 4007a062ce3SYee Lee arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension 4017a062ce3SYee Lee support 4027a062ce3SYee Lee 403e52347bdSJani Nikula ataflop= [HW,M68k] 404e52347bdSJani Nikula 405e52347bdSJani Nikula atarimouse= [HW,MOUSE] Atari Mouse 406e52347bdSJani Nikula 407e52347bdSJani Nikula atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 408e52347bdSJani Nikula EzKey and similar keyboards 409e52347bdSJani Nikula 410e52347bdSJani Nikula atkbd.reset= [HW] Reset keyboard during initialization 411e52347bdSJani Nikula 412e52347bdSJani Nikula atkbd.set= [HW] Select keyboard code set 413e52347bdSJani Nikula Format: <int> (2 = AT (default), 3 = PS/2) 414e52347bdSJani Nikula 415e52347bdSJani Nikula atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 416e52347bdSJani Nikula keyboards 417e52347bdSJani Nikula 418e52347bdSJani Nikula atkbd.softraw= [HW] Choose between synthetic and real raw mode 419e52347bdSJani Nikula Format: <bool> (0 = real, 1 = synthetic (default)) 420e52347bdSJani Nikula 421e52347bdSJani Nikula atkbd.softrepeat= [HW] 422e52347bdSJani Nikula Use software keyboard repeat 423e52347bdSJani Nikula 424e52347bdSJani Nikula audit= [KNL] Enable the audit sub-system 42511dd2666SGreg Edwards Format: { "0" | "1" | "off" | "on" } 42611dd2666SGreg Edwards 0 | off - kernel audit is disabled and can not be 42711dd2666SGreg Edwards enabled until the next reboot 428e52347bdSJani Nikula unset - kernel audit is initialized but disabled and 429e52347bdSJani Nikula will be fully enabled by the userspace auditd. 43011dd2666SGreg Edwards 1 | on - kernel audit is initialized and partially 43111dd2666SGreg Edwards enabled, storing at most audit_backlog_limit 43211dd2666SGreg Edwards messages in RAM until it is fully enabled by the 43311dd2666SGreg Edwards userspace auditd. 434e52347bdSJani Nikula Default: unset 435e52347bdSJani Nikula 436e52347bdSJani Nikula audit_backlog_limit= [KNL] Set the audit queue size limit. 437e52347bdSJani Nikula Format: <int> (must be >=0) 438e52347bdSJani Nikula Default: 64 439e52347bdSJani Nikula 440e52347bdSJani Nikula bau= [X86_UV] Enable the BAU on SGI UV. The default 441e52347bdSJani Nikula behavior is to disable the BAU (i.e. bau=0). 442e52347bdSJani Nikula Format: { "0" | "1" } 443e52347bdSJani Nikula 0 - Disable the BAU. 444e52347bdSJani Nikula 1 - Enable the BAU. 445e52347bdSJani Nikula unset - Disable the BAU. 446e52347bdSJani Nikula 447e52347bdSJani Nikula baycom_epp= [HW,AX25] 448e52347bdSJani Nikula Format: <io>,<mode> 449e52347bdSJani Nikula 450e52347bdSJani Nikula baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 451e52347bdSJani Nikula Format: <io>,<mode> 452e52347bdSJani Nikula See header of drivers/net/hamradio/baycom_par.c. 453e52347bdSJani Nikula 454e52347bdSJani Nikula baycom_ser_fdx= [HW,AX25] 455e52347bdSJani Nikula BayCom Serial Port AX.25 Modem (Full Duplex Mode) 456e52347bdSJani Nikula Format: <io>,<irq>,<mode>[,<baud>] 457e52347bdSJani Nikula See header of drivers/net/hamradio/baycom_ser_fdx.c. 458e52347bdSJani Nikula 459e52347bdSJani Nikula baycom_ser_hdx= [HW,AX25] 460e52347bdSJani Nikula BayCom Serial Port AX.25 Modem (Half Duplex Mode) 461e52347bdSJani Nikula Format: <io>,<irq>,<mode> 462e52347bdSJani Nikula See header of drivers/net/hamradio/baycom_ser_hdx.c. 463e52347bdSJani Nikula 464e52347bdSJani Nikula blkdevparts= Manual partition parsing of block device(s) for 465e52347bdSJani Nikula embedded devices based on command line input. 466898bd37aSMauro Carvalho Chehab See Documentation/block/cmdline-partition.rst 467e52347bdSJani Nikula 468e52347bdSJani Nikula boot_delay= Milliseconds to delay each printk during boot. 469e52347bdSJani Nikula Values larger than 10 seconds (10000) are changed to 470e52347bdSJani Nikula no delay (0). 471e52347bdSJani Nikula Format: integer 472e52347bdSJani Nikula 4737495e092SSteven Rostedt (VMware) bootconfig [KNL] 4747495e092SSteven Rostedt (VMware) Extended command line options can be added to an initrd 4757495e092SSteven Rostedt (VMware) and this will cause the kernel to look for it. 4767495e092SSteven Rostedt (VMware) 4777495e092SSteven Rostedt (VMware) See Documentation/admin-guide/bootconfig.rst 4787495e092SSteven Rostedt (VMware) 479e52347bdSJani Nikula bert_disable [ACPI] 480e52347bdSJani Nikula Disable BERT OS support on buggy BIOSes. 481e52347bdSJani Nikula 4821ffb8d03SAlex Hung bgrt_disable [ACPI][X86] 4831ffb8d03SAlex Hung Disable BGRT to avoid flickering OEM logo. 4841ffb8d03SAlex Hung 485e52347bdSJani Nikula bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 486e52347bdSJani Nikula bttv.radio= Most important insmod options are available as 487e52347bdSJani Nikula kernel args too. 48832e2eae2SMauro Carvalho Chehab bttv.pll= See Documentation/admin-guide/media/bttv.rst 489e52347bdSJani Nikula bttv.tuner= 490e52347bdSJani Nikula 491e52347bdSJani Nikula bulk_remove=off [PPC] This parameter disables the use of the pSeries 492e52347bdSJani Nikula firmware feature for flushing multiple hpte entries 493e52347bdSJani Nikula at a time. 494e52347bdSJani Nikula 495e52347bdSJani Nikula c101= [NET] Moxa C101 synchronous serial card 496e52347bdSJani Nikula 497e52347bdSJani Nikula cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 498e52347bdSJani Nikula Sometimes CPU hardware bugs make them report the cache 499e52347bdSJani Nikula size incorrectly. The kernel will attempt work arounds 500e52347bdSJani Nikula to fix known problems, but for some CPUs it is not 501e52347bdSJani Nikula possible to determine what the correct size should be. 502e52347bdSJani Nikula This option provides an override for these situations. 503e52347bdSJani Nikula 5043fc46fc9SMartin Kepplinger carrier_timeout= 5053fc46fc9SMartin Kepplinger [NET] Specifies amount of time (in seconds) that 5063fc46fc9SMartin Kepplinger the kernel should wait for a network carrier. By default 5073fc46fc9SMartin Kepplinger it waits 120 seconds. 5083fc46fc9SMartin Kepplinger 509e52347bdSJani Nikula ca_keys= [KEYS] This parameter identifies a specific key(s) on 510e52347bdSJani Nikula the system trusted keyring to be used for certificate 511e52347bdSJani Nikula trust validation. 512e52347bdSJani Nikula format: { id:<keyid> | builtin } 513e52347bdSJani Nikula 514e52347bdSJani Nikula cca= [MIPS] Override the kernel pages' cache coherency 515e52347bdSJani Nikula algorithm. Accepted values range from 0 to 7 516e52347bdSJani Nikula inclusive. See arch/mips/include/asm/pgtable-bits.h 517e52347bdSJani Nikula for platform specific values (SB1, Loongson3 and 518e52347bdSJani Nikula others). 519e52347bdSJani Nikula 520e52347bdSJani Nikula ccw_timeout_log [S390] 5218b4a503dSMauro Carvalho Chehab See Documentation/s390/common_io.rst for details. 522e52347bdSJani Nikula 5233958e2d0SSuren Baghdasaryan cgroup_disable= [KNL] Disable a particular controller or optional feature 5243958e2d0SSuren Baghdasaryan Format: {name of the controller(s) or feature(s) to disable} 525e52347bdSJani Nikula The effects of cgroup_disable=foo are: 526e52347bdSJani Nikula - foo isn't auto-mounted if you mount all cgroups in 527e52347bdSJani Nikula a single hierarchy 528e52347bdSJani Nikula - foo isn't visible as an individually mountable 529e52347bdSJani Nikula subsystem 5303958e2d0SSuren Baghdasaryan - if foo is an optional feature then the feature is 5313958e2d0SSuren Baghdasaryan disabled and corresponding cgroup files are not 5323958e2d0SSuren Baghdasaryan created 533e52347bdSJani Nikula {Currently only "memory" controller deal with this and 534e52347bdSJani Nikula cut the overhead, others just disable the usage. So 535e52347bdSJani Nikula only cgroup_disable=memory is actually worthy} 5363958e2d0SSuren Baghdasaryan Specifying "pressure" disables per-cgroup pressure 5373958e2d0SSuren Baghdasaryan stall information accounting feature 538e52347bdSJani Nikula 5393fc9c12dSTejun Heo cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1 5403fc9c12dSTejun Heo Format: { { controller | "all" | "named" } 5413fc9c12dSTejun Heo [,{ controller | "all" | "named" }...] } 542e52347bdSJani Nikula Like cgroup_disable, but only applies to cgroup v1; 543e52347bdSJani Nikula the blacklisted controllers remain available in cgroup2. 5443fc9c12dSTejun Heo "all" blacklists all controllers and "named" disables 5453fc9c12dSTejun Heo named mounts. Specifying both "all" and "named" disables 5463fc9c12dSTejun Heo all v1 hierarchies. 547e52347bdSJani Nikula 548e52347bdSJani Nikula cgroup.memory= [KNL] Pass options to the cgroup memory controller. 549e52347bdSJani Nikula Format: <string> 550e52347bdSJani Nikula nosocket -- Disable socket memory accounting. 551e52347bdSJani Nikula nokmem -- Disable kernel memory accounting. 552e52347bdSJani Nikula 553e52347bdSJani Nikula checkreqprot [SELINUX] Set initial checkreqprot flag value. 554e52347bdSJani Nikula Format: { "0" | "1" } 555e52347bdSJani Nikula See security/selinux/Kconfig help text. 556e52347bdSJani Nikula 0 -- check protection applied by kernel (includes 557e52347bdSJani Nikula any implied execute protection). 558e52347bdSJani Nikula 1 -- check protection requested by application. 559e52347bdSJani Nikula Default value is set via a kernel config option. 560e52347bdSJani Nikula Value can be changed at runtime via 561d41415ebSStephen Smalley /sys/fs/selinux/checkreqprot. 562e9c38f9fSStephen Smalley Setting checkreqprot to 1 is deprecated. 563e52347bdSJani Nikula 564e52347bdSJani Nikula cio_ignore= [S390] 5658b4a503dSMauro Carvalho Chehab See Documentation/s390/common_io.rst for details. 566e52347bdSJani Nikula clk_ignore_unused 567e52347bdSJani Nikula [CLK] 568e52347bdSJani Nikula Prevents the clock framework from automatically gating 569e52347bdSJani Nikula clocks that have not been explicitly enabled by a Linux 570e52347bdSJani Nikula device driver but are enabled in hardware at reset or 571e52347bdSJani Nikula by the bootloader/firmware. Note that this does not 572e52347bdSJani Nikula force such clocks to be always-on nor does it reserve 573e52347bdSJani Nikula those clocks in any way. This parameter is useful for 574e52347bdSJani Nikula debug and development, but should not be needed on a 575e52347bdSJani Nikula platform with proper driver support. For more 57618bcaa4eSMauro Carvalho Chehab information, see Documentation/driver-api/clk.rst. 577e52347bdSJani Nikula 578e52347bdSJani Nikula clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 579e52347bdSJani Nikula [Deprecated] 580e52347bdSJani Nikula Forces specified clocksource (if available) to be used 581e52347bdSJani Nikula when calculating gettimeofday(). If specified 582e52347bdSJani Nikula clocksource is not available, it defaults to PIT. 583e52347bdSJani Nikula Format: { pit | tsc | cyclone | pmtmr } 584e52347bdSJani Nikula 585e52347bdSJani Nikula clocksource= Override the default clocksource 586e52347bdSJani Nikula Format: <string> 587e52347bdSJani Nikula Override the default clocksource and use the clocksource 588e52347bdSJani Nikula with the name specified. 589e52347bdSJani Nikula Some clocksource names to choose from, depending on 590e52347bdSJani Nikula the platform: 591e52347bdSJani Nikula [all] jiffies (this is the base, fallback clocksource) 592e52347bdSJani Nikula [ACPI] acpi_pm 593e52347bdSJani Nikula [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 594e52347bdSJani Nikula pxa_timer,timer3,32k_counter,timer0_1 595e52347bdSJani Nikula [X86-32] pit,hpet,tsc; 596e52347bdSJani Nikula scx200_hrt on Geode; cyclone on IBM x440 597e52347bdSJani Nikula [MIPS] MIPS 598e52347bdSJani Nikula [PARISC] cr16 599e52347bdSJani Nikula [S390] tod 600e52347bdSJani Nikula [SH] SuperH 601e52347bdSJani Nikula [SPARC64] tick 602e52347bdSJani Nikula [X86-64] hpet,tsc 603e52347bdSJani Nikula 604e52347bdSJani Nikula clocksource.arm_arch_timer.evtstrm= 605e52347bdSJani Nikula [ARM,ARM64] 606e52347bdSJani Nikula Format: <bool> 607e52347bdSJani Nikula Enable/disable the eventstream feature of the ARM 608e52347bdSJani Nikula architected timer so that code using WFE-based polling 609e52347bdSJani Nikula loops can be debugged more effectively on production 610e52347bdSJani Nikula systems. 611e52347bdSJani Nikula 612db3a34e1SPaul E. McKenney clocksource.max_cswd_read_retries= [KNL] 613db3a34e1SPaul E. McKenney Number of clocksource_watchdog() retries due to 614db3a34e1SPaul E. McKenney external delays before the clock will be marked 615db3a34e1SPaul E. McKenney unstable. Defaults to three retries, that is, 616db3a34e1SPaul E. McKenney four attempts to read the clock under test. 617db3a34e1SPaul E. McKenney 618fa218f1cSPaul E. McKenney clocksource.verify_n_cpus= [KNL] 619fa218f1cSPaul E. McKenney Limit the number of CPUs checked for clocksources 620fa218f1cSPaul E. McKenney marked with CLOCK_SOURCE_VERIFY_PERCPU that 621fa218f1cSPaul E. McKenney are marked unstable due to excessive skew. 622fa218f1cSPaul E. McKenney A negative value says to check all CPUs, while 623fa218f1cSPaul E. McKenney zero says not to check any. Values larger than 624fa218f1cSPaul E. McKenney nr_cpu_ids are silently truncated to nr_cpu_ids. 625fa218f1cSPaul E. McKenney The actual CPUs are chosen randomly, with 626fa218f1cSPaul E. McKenney no replacement if the same CPU is chosen twice. 627fa218f1cSPaul E. McKenney 6281253b9b8SPaul E. McKenney clocksource-wdtest.holdoff= [KNL] 6291253b9b8SPaul E. McKenney Set the time in seconds that the clocksource 6301253b9b8SPaul E. McKenney watchdog test waits before commencing its tests. 6311253b9b8SPaul E. McKenney Defaults to zero when built as a module and to 6321253b9b8SPaul E. McKenney 10 seconds when built into the kernel. 6331253b9b8SPaul E. McKenney 6340a4bb5e5SArvind Sankar clearcpuid=BITNUM[,BITNUM...] [X86] 635e52347bdSJani Nikula Disable CPUID feature X for the kernel. See 636e52347bdSJani Nikula arch/x86/include/asm/cpufeatures.h for the valid bit 637e52347bdSJani Nikula numbers. Note the Linux specific bits are not necessarily 638e52347bdSJani Nikula stable over kernel options, but the vendor specific 639e52347bdSJani Nikula ones should be. 640e52347bdSJani Nikula Also note that user programs calling CPUID directly 641e52347bdSJani Nikula or using the feature without checking anything 642e52347bdSJani Nikula will still see it. This just prevents it from 643e52347bdSJani Nikula being used by the kernel or shown in /proc/cpuinfo. 644e52347bdSJani Nikula Also note the kernel might malfunction if you disable 645e52347bdSJani Nikula some critical bits. 646e52347bdSJani Nikula 647e52347bdSJani Nikula cma=nn[MG]@[start[MG][-end[MG]]] 648c372e741STian Tao [KNL,CMA] 649e52347bdSJani Nikula Sets the size of kernel global memory area for 650e52347bdSJani Nikula contiguous memory allocations and optionally the 651e52347bdSJani Nikula placement constraint by the physical address range of 652e52347bdSJani Nikula memory allocations. A value of 0 disables CMA 653e52347bdSJani Nikula altogether. For more information, see 6540b1abd1fSChristoph Hellwig kernel/dma/contiguous.c 655e52347bdSJani Nikula 656b7176c26SBarry Song cma_pernuma=nn[MG] 657bc47190dSRandy Dunlap [ARM64,KNL,CMA] 658b7176c26SBarry Song Sets the size of kernel per-numa memory area for 659b7176c26SBarry Song contiguous memory allocations. A value of 0 disables 660b7176c26SBarry Song per-numa CMA altogether. And If this option is not 661b7176c26SBarry Song specificed, the default value is 0. 662b7176c26SBarry Song With per-numa CMA enabled, DMA users on node nid will 663b7176c26SBarry Song first try to allocate buffer from the pernuma area 664b7176c26SBarry Song which is located in node nid, if the allocation fails, 665b7176c26SBarry Song they will fallback to the global default memory area. 666e52347bdSJani Nikula 667e52347bdSJani Nikula cmo_free_hint= [PPC] Format: { yes | no } 668e52347bdSJani Nikula Specify whether pages are marked as being inactive 669e52347bdSJani Nikula when they are freed. This is used in CMO environments 670e52347bdSJani Nikula to determine OS memory pressure for page stealing by 671e52347bdSJani Nikula a hypervisor. 672e52347bdSJani Nikula Default: yes 673e52347bdSJani Nikula 674e52347bdSJani Nikula coherent_pool=nn[KMG] [ARM,KNL] 675e52347bdSJani Nikula Sets the size of memory pool for coherent, atomic dma 676e52347bdSJani Nikula allocations, by default set to 256K. 677e52347bdSJani Nikula 678e52347bdSJani Nikula com20020= [HW,NET] ARCnet - COM20020 chipset 679e52347bdSJani Nikula Format: 680e52347bdSJani Nikula <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 681e52347bdSJani Nikula 682e52347bdSJani Nikula com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 683e52347bdSJani Nikula Format: <io>[,<irq>] 684e52347bdSJani Nikula 685e52347bdSJani Nikula com90xx= [HW,NET] 686e52347bdSJani Nikula ARCnet - COM90xx chipset (memory-mapped buffers) 687e52347bdSJani Nikula Format: <io>[,<irq>[,<memstart>]] 688e52347bdSJani Nikula 689e52347bdSJani Nikula condev= [HW,S390] console device 690e52347bdSJani Nikula conmode= 691e52347bdSJani Nikula 692e52347bdSJani Nikula console= [KNL] Output console device and options. 693e52347bdSJani Nikula 694e52347bdSJani Nikula tty<n> Use the virtual console device <n>. 695e52347bdSJani Nikula 696e52347bdSJani Nikula ttyS<n>[,options] 697e52347bdSJani Nikula ttyUSB0[,options] 698e52347bdSJani Nikula Use the specified serial port. The options are of 699e52347bdSJani Nikula the form "bbbbpnf", where "bbbb" is the baud rate, 700e52347bdSJani Nikula "p" is parity ("n", "o", or "e"), "n" is number of 701e52347bdSJani Nikula bits, and "f" is flow control ("r" for RTS or 702e52347bdSJani Nikula omit it). Default is "9600n8". 703e52347bdSJani Nikula 704e52347bdSJani Nikula See Documentation/admin-guide/serial-console.rst for more 705e52347bdSJani Nikula information. See 706d9d6ef25SMauro Carvalho Chehab Documentation/networking/netconsole.rst for an 707e52347bdSJani Nikula alternative. 708e52347bdSJani Nikula 709e52347bdSJani Nikula uart[8250],io,<addr>[,options] 710e52347bdSJani Nikula uart[8250],mmio,<addr>[,options] 711e52347bdSJani Nikula uart[8250],mmio16,<addr>[,options] 712e52347bdSJani Nikula uart[8250],mmio32,<addr>[,options] 713e52347bdSJani Nikula uart[8250],0x<addr>[,options] 714e52347bdSJani Nikula Start an early, polled-mode console on the 8250/16550 715e52347bdSJani Nikula UART at the specified I/O port or MMIO address, 716e52347bdSJani Nikula switching to the matching ttyS device later. 717e52347bdSJani Nikula MMIO inter-register address stride is either 8-bit 718e52347bdSJani Nikula (mmio), 16-bit (mmio16), or 32-bit (mmio32). 719e52347bdSJani Nikula If none of [io|mmio|mmio16|mmio32], <addr> is assumed 720e52347bdSJani Nikula to be equivalent to 'mmio'. 'options' are specified in 721e52347bdSJani Nikula the same format described for ttyS above; if unspecified, 722e52347bdSJani Nikula the h/w is not re-initialized. 723e52347bdSJani Nikula 724e52347bdSJani Nikula hvc<n> Use the hypervisor console device <n>. This is for 725e52347bdSJani Nikula both Xen and PowerPC hypervisors. 726e52347bdSJani Nikula 727e52347bdSJani Nikula If the device connected to the port is not a TTY but a braille 728e52347bdSJani Nikula device, prepend "brl," before the device type, for instance 729e52347bdSJani Nikula console=brl,ttyS0 730e52347bdSJani Nikula For now, only VisioBraille is supported. 731e52347bdSJani Nikula 732cca10d58SSergey Senozhatsky console_msg_format= 733cca10d58SSergey Senozhatsky [KNL] Change console messages format 734cca10d58SSergey Senozhatsky default 735cca10d58SSergey Senozhatsky By default we print messages on consoles in 736cca10d58SSergey Senozhatsky "[time stamp] text\n" format (time stamp may not be 737cca10d58SSergey Senozhatsky printed, depending on CONFIG_PRINTK_TIME or 738cca10d58SSergey Senozhatsky `printk_time' param). 739cca10d58SSergey Senozhatsky syslog 740cca10d58SSergey Senozhatsky Switch to syslog format: "<%u>[time stamp] text\n" 741cca10d58SSergey Senozhatsky IOW, each message will have a facility and loglevel 742cca10d58SSergey Senozhatsky prefix. The format is similar to one used by syslog() 743cca10d58SSergey Senozhatsky syscall, or to executing "dmesg -S --raw" or to reading 744cca10d58SSergey Senozhatsky from /proc/kmsg. 745cca10d58SSergey Senozhatsky 746e52347bdSJani Nikula consoleblank= [KNL] The console blank (screen saver) timeout in 747ac0a314cSDaniel Xu seconds. A value of 0 disables the blank timer. 748ac0a314cSDaniel Xu Defaults to 0. 749e52347bdSJani Nikula 750e52347bdSJani Nikula coredump_filter= 751e52347bdSJani Nikula [KNL] Change the default value for 752e52347bdSJani Nikula /proc/<pid>/coredump_filter. 753cd4ca341SJimmy Assarsson See also Documentation/filesystems/proc.rst. 754e52347bdSJani Nikula 75562a31ce1SLeo Yan coresight_cpu_debug.enable 75662a31ce1SLeo Yan [ARM,ARM64] 75762a31ce1SLeo Yan Format: <bool> 75862a31ce1SLeo Yan Enable/disable the CPU sampling based debugging. 75962a31ce1SLeo Yan 0: default value, disable debugging 76062a31ce1SLeo Yan 1: enable debugging at boot time 76162a31ce1SLeo Yan 762e52347bdSJani Nikula cpuidle.off=1 [CPU_IDLE] 763e52347bdSJani Nikula disable the cpuidle sub-system 764e52347bdSJani Nikula 76561cb5758SRafael J. Wysocki cpuidle.governor= 76661cb5758SRafael J. Wysocki [CPU_IDLE] Name of the cpuidle governor to use. 76761cb5758SRafael J. Wysocki 768d82f2692SLen Brown cpufreq.off=1 [CPU_FREQ] 769d82f2692SLen Brown disable the cpufreq sub-system 770d82f2692SLen Brown 7718412b456SQuentin Perret cpufreq.default_governor= 7728412b456SQuentin Perret [CPU_FREQ] Name of the default cpufreq governor or 7738412b456SQuentin Perret policy to use. This governor must be registered in the 7748412b456SQuentin Perret kernel before the cpufreq driver probes. 7758412b456SQuentin Perret 776e52347bdSJani Nikula cpu_init_udelay=N 777e52347bdSJani Nikula [X86] Delay for N microsec between assert and de-assert 778e52347bdSJani Nikula of APIC INIT to start processors. This delay occurs 779e52347bdSJani Nikula on every CPU online, such as boot, and resume from suspend. 780e52347bdSJani Nikula Default: 10000 781e52347bdSJani Nikula 782e52347bdSJani Nikula cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 783e52347bdSJani Nikula Format: 784e52347bdSJani Nikula <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 785e52347bdSJani Nikula 786e52347bdSJani Nikula crashkernel=size[KMG][@offset[KMG]] 787e52347bdSJani Nikula [KNL] Using kexec, Linux can switch to a 'crash kernel' 788e52347bdSJani Nikula upon panic. This parameter reserves the physical 789e52347bdSJani Nikula memory region [offset, offset + size] for that kernel 790e52347bdSJani Nikula image. If '@offset' is omitted, then a suitable offset 791b9ac3849SDave Young is selected automatically. 792be3a5b0eSRandy Dunlap [KNL, X86-64] Select a region under 4G first, and 793b9ac3849SDave Young fall back to reserve region above 4G when '@offset' 794b9ac3849SDave Young hasn't been specified. 795330d4810SMauro Carvalho Chehab See Documentation/admin-guide/kdump/kdump.rst for further details. 796e52347bdSJani Nikula 797e52347bdSJani Nikula crashkernel=range1:size1[,range2:size2,...][@offset] 798e52347bdSJani Nikula [KNL] Same as above, but depends on the memory 799e52347bdSJani Nikula in the running system. The syntax of range is 800e52347bdSJani Nikula start-[end] where start and end are both 801e52347bdSJani Nikula a memory unit (amount[KMG]). See also 802330d4810SMauro Carvalho Chehab Documentation/admin-guide/kdump/kdump.rst for an example. 803e52347bdSJani Nikula 804e52347bdSJani Nikula crashkernel=size[KMG],high 805be3a5b0eSRandy Dunlap [KNL, X86-64] range could be above 4G. Allow kernel 806e52347bdSJani Nikula to allocate physical memory region from top, so could 807e52347bdSJani Nikula be above 4G if system have more than 4G ram installed. 808e52347bdSJani Nikula Otherwise memory region will be allocated below 4G, if 809e52347bdSJani Nikula available. 810e52347bdSJani Nikula It will be ignored if crashkernel=X is specified. 811e52347bdSJani Nikula crashkernel=size[KMG],low 812be3a5b0eSRandy Dunlap [KNL, X86-64] range under 4G. When crashkernel=X,high 813e52347bdSJani Nikula is passed, kernel could allocate physical memory region 814e52347bdSJani Nikula above 4G, that cause second kernel crash on system 815e52347bdSJani Nikula that require some amount of low memory, e.g. swiotlb 816e52347bdSJani Nikula requires at least 64M+32K low memory, also enough extra 817e52347bdSJani Nikula low memory is needed to make sure DMA buffers for 32-bit 818e52347bdSJani Nikula devices won't run out. Kernel would try to allocate at 819e52347bdSJani Nikula at least 256M below 4G automatically. 820e52347bdSJani Nikula This one let user to specify own low range under 4G 821e52347bdSJani Nikula for second kernel instead. 822e52347bdSJani Nikula 0: to disable low allocation. 823e52347bdSJani Nikula It will be ignored when crashkernel=X,high is not used 824e52347bdSJani Nikula or memory reserved is below 4G. 825e52347bdSJani Nikula 826e52347bdSJani Nikula cryptomgr.notests 827e52347bdSJani Nikula [KNL] Disable crypto self-tests 828e52347bdSJani Nikula 829e52347bdSJani Nikula cs89x0_dma= [HW,NET] 830e52347bdSJani Nikula Format: <dma> 831e52347bdSJani Nikula 832e52347bdSJani Nikula cs89x0_media= [HW,NET] 833e52347bdSJani Nikula Format: { rj45 | aui | bnc } 834e52347bdSJani Nikula 8358d0968ccSJuergen Gross csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call 8368d0968ccSJuergen Gross handling. When switched on, additional debug data is 8378d0968ccSJuergen Gross printed to the console in case a hanging CPU is 8388d0968ccSJuergen Gross detected, and that CPU is pinged again in order to try 8398d0968ccSJuergen Gross to resolve the hang situation. 840a5aabaceSJuergen Gross 0: disable csdlock debugging (default) 841a5aabaceSJuergen Gross 1: enable basic csdlock debugging (minor impact) 842a5aabaceSJuergen Gross ext: enable extended csdlock debugging (more impact, 843a5aabaceSJuergen Gross but more data) 8448d0968ccSJuergen Gross 845e52347bdSJani Nikula dasd= [HW,NET] 846e52347bdSJani Nikula See header of drivers/s390/block/dasd_devmap.c. 847e52347bdSJani Nikula 848e52347bdSJani Nikula db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 849e52347bdSJani Nikula (one device per port) 850e52347bdSJani Nikula Format: <port#>,<type> 8511752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 852e52347bdSJani Nikula 853e52347bdSJani Nikula debug [KNL] Enable kernel debugging (events log level). 854e52347bdSJani Nikula 8553672476eSTobin C. Harding debug_boot_weak_hash 8563672476eSTobin C. Harding [KNL] Enable printing [hashed] pointers early in the 8573672476eSTobin C. Harding boot sequence. If enabled, we use a weak hash instead 8583672476eSTobin C. Harding of siphash to hash pointers. Use this option if you are 8593672476eSTobin C. Harding seeing instances of '(___ptrval___)') and need to see a 8603672476eSTobin C. Harding value (hashed pointer) instead. Cryptographically 8613672476eSTobin C. Harding insecure, please do not use on production kernels. 8623672476eSTobin C. Harding 863e52347bdSJani Nikula debug_locks_verbose= 8645831c0f7SPeter Zijlstra [KNL] verbose locking self-tests 8655831c0f7SPeter Zijlstra Format: <int> 866e52347bdSJani Nikula Print debugging info while doing the locking API 867e52347bdSJani Nikula self-tests. 8685831c0f7SPeter Zijlstra Bitmask for the various LOCKTYPE_ tests. Defaults to 0 8695831c0f7SPeter Zijlstra (no extra messages), setting it to -1 (all bits set) 8705831c0f7SPeter Zijlstra will print _a_lot_ more information - normally only 8715831c0f7SPeter Zijlstra useful to lockdep developers. 872e52347bdSJani Nikula 873e52347bdSJani Nikula debug_objects [KNL] Enable object debugging 874e52347bdSJani Nikula 875e52347bdSJani Nikula no_debug_objects 876e52347bdSJani Nikula [KNL] Disable object debugging 877e52347bdSJani Nikula 878e52347bdSJani Nikula debug_guardpage_minorder= 879e52347bdSJani Nikula [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this 880e52347bdSJani Nikula parameter allows control of the order of pages that will 881e52347bdSJani Nikula be intentionally kept free (and hence protected) by the 882e52347bdSJani Nikula buddy allocator. Bigger value increase the probability 883e52347bdSJani Nikula of catching random memory corruption, but reduce the 884e52347bdSJani Nikula amount of memory for normal system use. The maximum 885e52347bdSJani Nikula possible value is MAX_ORDER/2. Setting this parameter 886e52347bdSJani Nikula to 1 or 2 should be enough to identify most random 887e52347bdSJani Nikula memory corruption problems caused by bugs in kernel or 888e52347bdSJani Nikula driver code when a CPU writes to (or reads from) a 889e52347bdSJani Nikula random memory location. Note that there exists a class 890e52347bdSJani Nikula of memory corruptions problems caused by buggy H/W or 891e52347bdSJani Nikula F/W or by drivers badly programing DMA (basically when 892e52347bdSJani Nikula memory is written at bus level and the CPU MMU is 893e52347bdSJani Nikula bypassed) which are not detectable by 894e52347bdSJani Nikula CONFIG_DEBUG_PAGEALLOC, hence this option will not help 895e52347bdSJani Nikula tracking down these problems. 896e52347bdSJani Nikula 897e52347bdSJani Nikula debug_pagealloc= 8983972f6bbSVlastimil Babka [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter 8993972f6bbSVlastimil Babka enables the feature at boot time. By default, it is 9003972f6bbSVlastimil Babka disabled and the system will work mostly the same as a 9013972f6bbSVlastimil Babka kernel built without CONFIG_DEBUG_PAGEALLOC. 9028974558fSVlastimil Babka Note: to get most of debug_pagealloc error reports, it's 9038974558fSVlastimil Babka useful to also enable the page_owner functionality. 904e52347bdSJani Nikula on: enable the feature 905e52347bdSJani Nikula 906a24c6f7bSPeter Enderborg debugfs= [KNL] This parameter enables what is exposed to userspace 907a24c6f7bSPeter Enderborg and debugfs internal clients. 908a24c6f7bSPeter Enderborg Format: { on, no-mount, off } 909a24c6f7bSPeter Enderborg on: All functions are enabled. 910a24c6f7bSPeter Enderborg no-mount: 911a24c6f7bSPeter Enderborg Filesystem is not registered but kernel clients can 912a24c6f7bSPeter Enderborg access APIs and a crashkernel can be used to read 913a24c6f7bSPeter Enderborg its content. There is nothing to mount. 914a24c6f7bSPeter Enderborg off: Filesystem is not registered and clients 915a24c6f7bSPeter Enderborg get a -EPERM as result when trying to register files 916a24c6f7bSPeter Enderborg or directories within debugfs. 917a24c6f7bSPeter Enderborg This is equivalent of the runtime functionality if 918a24c6f7bSPeter Enderborg debugfs was not enabled in the kernel at all. 919a24c6f7bSPeter Enderborg Default value is set in build-time with a kernel configuration. 920a24c6f7bSPeter Enderborg 921e52347bdSJani Nikula debugpat [X86] Enable PAT debugging 922e52347bdSJani Nikula 923e52347bdSJani Nikula decnet.addr= [HW,NET] 924e52347bdSJani Nikula Format: <area>[,<node>] 9259a69fb9cSMauro Carvalho Chehab See also Documentation/networking/decnet.rst. 926e52347bdSJani Nikula 927e52347bdSJani Nikula default_hugepagesz= 928282f4214SMike Kravetz [HW] The size of the default HugeTLB page. This is 929282f4214SMike Kravetz the size represented by the legacy /proc/ hugepages 930282f4214SMike Kravetz APIs. In addition, this is the default hugetlb size 931282f4214SMike Kravetz used for shmget(), mmap() and mounting hugetlbfs 932282f4214SMike Kravetz filesystems. If not specified, defaults to the 933282f4214SMike Kravetz architecture's default huge page size. Huge page 934282f4214SMike Kravetz sizes are architecture dependent. See also 935282f4214SMike Kravetz Documentation/admin-guide/mm/hugetlbpage.rst. 936282f4214SMike Kravetz Format: size[KMG] 937e52347bdSJani Nikula 93825b4e70dSRob Herring deferred_probe_timeout= 93925b4e70dSRob Herring [KNL] Debugging option to set a timeout in seconds for 94025b4e70dSRob Herring deferred probe to give up waiting on dependencies to 94125b4e70dSRob Herring probe. Only specific dependencies (subsystems or 94225b4e70dSRob Herring drivers) that have opted in will be ignored. A timeout of 0 94325b4e70dSRob Herring will timeout at the end of initcalls. This option will also 94425b4e70dSRob Herring dump out devices still on the deferred probe list after 94525b4e70dSRob Herring retrying. 94625b4e70dSRob Herring 947c65e6815SMikhail Zaslonko dfltcc= [HW,S390] 948c65e6815SMikhail Zaslonko Format: { on | off | def_only | inf_only | always } 949c65e6815SMikhail Zaslonko on: s390 zlib hardware support for compression on 950c65e6815SMikhail Zaslonko level 1 and decompression (default) 951c65e6815SMikhail Zaslonko off: No s390 zlib hardware support 952c65e6815SMikhail Zaslonko def_only: s390 zlib hardware support for deflate 953c65e6815SMikhail Zaslonko only (compression on level 1) 954c65e6815SMikhail Zaslonko inf_only: s390 zlib hardware support for inflate 955c65e6815SMikhail Zaslonko only (decompression) 956c65e6815SMikhail Zaslonko always: Same as 'on' but ignores the selected compression 957c65e6815SMikhail Zaslonko level always using hardware support (used for debugging) 958c65e6815SMikhail Zaslonko 959e52347bdSJani Nikula dhash_entries= [KNL] 960e52347bdSJani Nikula Set number of hash buckets for dentry cache. 961e52347bdSJani Nikula 962e52347bdSJani Nikula disable_1tb_segments [PPC] 963e52347bdSJani Nikula Disables the use of 1TB hash page table segments. This 964e52347bdSJani Nikula causes the kernel to fall back to 256MB segments which 965e52347bdSJani Nikula can be useful when debugging issues that require an SLB 966e52347bdSJani Nikula miss to occur. 967e52347bdSJani Nikula 96882a1b8edSNicholas Piggin stress_slb [PPC] 96982a1b8edSNicholas Piggin Limits the number of kernel SLB entries, and flushes 97082a1b8edSNicholas Piggin them frequently to increase the rate of SLB faults 97182a1b8edSNicholas Piggin on kernel addresses. 97282a1b8edSNicholas Piggin 973e52347bdSJani Nikula disable= [IPV6] 97419093313SMauro Carvalho Chehab See Documentation/networking/ipv6.rst. 975e52347bdSJani Nikula 976b5cb15d9SChris von Recklinghausen hardened_usercopy= 977b5cb15d9SChris von Recklinghausen [KNL] Under CONFIG_HARDENED_USERCOPY, whether 978b5cb15d9SChris von Recklinghausen hardening is enabled for this boot. Hardened 979b5cb15d9SChris von Recklinghausen usercopy checking is used to protect the kernel 980b5cb15d9SChris von Recklinghausen from reading or writing beyond known memory 981b5cb15d9SChris von Recklinghausen allocation boundaries as a proactive defense 982b5cb15d9SChris von Recklinghausen against bounds-checking flaws in the kernel's 983b5cb15d9SChris von Recklinghausen copy_to_user()/copy_from_user() interface. 984b5cb15d9SChris von Recklinghausen on Perform hardened usercopy checks (default). 985b5cb15d9SChris von Recklinghausen off Disable hardened usercopy checks. 986b5cb15d9SChris von Recklinghausen 987e52347bdSJani Nikula disable_radix [PPC] 988e52347bdSJani Nikula Disable RADIX MMU mode on POWER9 989e52347bdSJani Nikula 990bf6b7661SAneesh Kumar K.V radix_hcall_invalidate=on [PPC/PSERIES] 991bf6b7661SAneesh Kumar K.V Disable RADIX GTSE feature and use hcall for TLB 992bf6b7661SAneesh Kumar K.V invalidate. 993bf6b7661SAneesh Kumar K.V 9942275d7b5SNicholas Piggin disable_tlbie [PPC] 9952275d7b5SNicholas Piggin Disable TLBIE instruction. Currently does not work 9962275d7b5SNicholas Piggin with KVM, with HASH MMU, or with coherent accelerators. 9972275d7b5SNicholas Piggin 998e52347bdSJani Nikula disable_cpu_apicid= [X86,APIC,SMP] 999e52347bdSJani Nikula Format: <int> 1000e52347bdSJani Nikula The number of initial APIC ID for the 1001e52347bdSJani Nikula corresponding CPU to be disabled at boot, 1002e52347bdSJani Nikula mostly used for the kdump 2nd kernel to 1003e52347bdSJani Nikula disable BSP to wake up multiple CPUs without 1004e52347bdSJani Nikula causing system reset or hang due to sending 1005e52347bdSJani Nikula INIT from AP to BSP. 1006e52347bdSJani Nikula 1007e52347bdSJani Nikula disable_ddw [PPC/PSERIES] 1008255bf90fSRandy Dunlap Disable Dynamic DMA Window support. Use this 1009e52347bdSJani Nikula to workaround buggy firmware. 1010e52347bdSJani Nikula 1011e52347bdSJani Nikula disable_ipv6= [IPV6] 101219093313SMauro Carvalho Chehab See Documentation/networking/ipv6.rst. 1013e52347bdSJani Nikula 1014e52347bdSJani Nikula disable_mtrr_cleanup [X86] 1015e52347bdSJani Nikula The kernel tries to adjust MTRR layout from continuous 1016e52347bdSJani Nikula to discrete, to make X server driver able to add WB 1017e52347bdSJani Nikula entry later. This parameter disables that. 1018e52347bdSJani Nikula 1019e52347bdSJani Nikula disable_mtrr_trim [X86, Intel and AMD only] 1020e52347bdSJani Nikula By default the kernel will trim any uncacheable 1021e52347bdSJani Nikula memory out of your available memory pool based on 1022e52347bdSJani Nikula MTRR settings. This parameter disables that behavior, 1023e52347bdSJani Nikula possibly causing your machine to run very slowly. 1024e52347bdSJani Nikula 1025e52347bdSJani Nikula disable_timer_pin_1 [X86] 1026e52347bdSJani Nikula Disable PIN 1 of APIC timer 1027e52347bdSJani Nikula Can be useful to work around chipset bugs. 1028e52347bdSJani Nikula 1029e52347bdSJani Nikula dis_ucode_ldr [X86] Disable the microcode loader. 1030e52347bdSJani Nikula 1031e52347bdSJani Nikula dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, 1032e52347bdSJani Nikula this option disables the debugging code at boot. 1033e52347bdSJani Nikula 1034e52347bdSJani Nikula dma_debug_entries=<number> 1035e52347bdSJani Nikula This option allows to tune the number of preallocated 1036e52347bdSJani Nikula entries for DMA-API debugging code. One entry is 1037e52347bdSJani Nikula required per DMA-API allocation. Use this if the 1038e52347bdSJani Nikula DMA-API debugging code disables itself because the 1039e52347bdSJani Nikula architectural default is too low. 1040e52347bdSJani Nikula 1041e52347bdSJani Nikula dma_debug_driver=<driver_name> 1042e52347bdSJani Nikula With this option the DMA-API debugging driver 1043e52347bdSJani Nikula filter feature can be enabled at boot time. Just 1044e52347bdSJani Nikula pass the driver to filter for as the parameter. 1045e52347bdSJani Nikula The filter can be disabled or changed to another 1046e52347bdSJani Nikula driver later using sysfs. 1047e52347bdSJani Nikula 10481ea61b68SFeng Tang driver_async_probe= [KNL] 10491ea61b68SFeng Tang List of driver names to be probed asynchronously. 10501ea61b68SFeng Tang Format: <driver_name1>,<driver_name2>... 10511ea61b68SFeng Tang 105253fd40a9SJani Nikula drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] 1053e52347bdSJani Nikula Broken monitors, graphic adapters, KVMs and EDIDless 1054e52347bdSJani Nikula panels may send no or incorrect EDID data sets. 1055e52347bdSJani Nikula This parameter allows to specify an EDID data sets 1056e52347bdSJani Nikula in the /lib/firmware directory that are used instead. 1057e52347bdSJani Nikula Generic built-in EDID data sets are used, if one of 1058e52347bdSJani Nikula edid/1024x768.bin, edid/1280x1024.bin, 1059e52347bdSJani Nikula edid/1680x1050.bin, or edid/1920x1080.bin is given 1060e52347bdSJani Nikula and no file with the same name exists. Details and 1061e52347bdSJani Nikula instructions how to build your own EDID data are 1062cd4ca341SJimmy Assarsson available in Documentation/admin-guide/edid.rst. An EDID 1063e52347bdSJani Nikula data set will only be used for a particular connector, 1064e52347bdSJani Nikula if its name and a colon are prepended to the EDID 1065e52347bdSJani Nikula name. Each connector may use a unique EDID data 1066e52347bdSJani Nikula set by separating the files with a comma. An EDID 1067e52347bdSJani Nikula data set with no connector name will be used for 1068e52347bdSJani Nikula any connectors not explicitly specified. 1069e52347bdSJani Nikula 1070e52347bdSJani Nikula dscc4.setup= [NET] 1071e52347bdSJani Nikula 1072a2b05b7aSNicholas Piggin dt_cpu_ftrs= [PPC] 1073a2b05b7aSNicholas Piggin Format: {"off" | "known"} 1074a2b05b7aSNicholas Piggin Control how the dt_cpu_ftrs device-tree binding is 1075a2b05b7aSNicholas Piggin used for CPU feature discovery and setup (if it 1076a2b05b7aSNicholas Piggin exists). 1077a2b05b7aSNicholas Piggin off: Do not use it, fall back to legacy cpu table. 1078a2b05b7aSNicholas Piggin known: Do not pass through unknown features to guests 1079a2b05b7aSNicholas Piggin or userspace, only those that the kernel is aware of. 1080a2b05b7aSNicholas Piggin 1081e7aa8c2eSLinus Torvalds dump_apple_properties [X86] 1082e7aa8c2eSLinus Torvalds Dump name and content of EFI device properties on 1083e7aa8c2eSLinus Torvalds x86 Macs. Useful for driver authors to determine 1084e7aa8c2eSLinus Torvalds what data is available or for reverse-engineering. 1085e7aa8c2eSLinus Torvalds 1086e52347bdSJani Nikula dyndbg[="val"] [KNL,DYNAMIC_DEBUG] 1087307e3ee9SRandy Dunlap <module>.dyndbg[="val"] 1088e52347bdSJani Nikula Enable debug messages at boot time. See 1089787e3075SSteffen Maier Documentation/admin-guide/dynamic-debug-howto.rst 1090787e3075SSteffen Maier for details. 1091e52347bdSJani Nikula 1092e52347bdSJani Nikula nopku [X86] Disable Memory Protection Keys CPU feature found 1093e52347bdSJani Nikula in some Intel CPUs. 1094e52347bdSJani Nikula 1095307e3ee9SRandy Dunlap <module>.async_probe [KNL] 1096e52347bdSJani Nikula Enable asynchronous probe on this module. 1097e52347bdSJani Nikula 1098e52347bdSJani Nikula early_ioremap_debug [KNL] 1099e52347bdSJani Nikula Enable debug messages in early_ioremap support. This 1100e52347bdSJani Nikula is useful for tracking down temporary early mappings 1101e52347bdSJani Nikula which are not unmapped. 1102e52347bdSJani Nikula 1103e52347bdSJani Nikula earlycon= [KNL] Output early console device and options. 1104e52347bdSJani Nikula 1105e18409c0SChristoph Hellwig When used with no options, the early console is 1106e18409c0SChristoph Hellwig determined by stdout-path property in device tree's 1107e18409c0SChristoph Hellwig chosen node or the ACPI SPCR table if supported by 1108e18409c0SChristoph Hellwig the platform. 1109e52347bdSJani Nikula 1110e52347bdSJani Nikula cdns,<addr>[,options] 1111e52347bdSJani Nikula Start an early, polled-mode console on a Cadence 1112e52347bdSJani Nikula (xuartps) serial port at the specified address. Only 1113e52347bdSJani Nikula supported option is baud rate. If baud rate is not 1114e52347bdSJani Nikula specified, the serial port must already be setup and 1115e52347bdSJani Nikula configured. 1116e52347bdSJani Nikula 1117e52347bdSJani Nikula uart[8250],io,<addr>[,options] 1118e52347bdSJani Nikula uart[8250],mmio,<addr>[,options] 1119e52347bdSJani Nikula uart[8250],mmio32,<addr>[,options] 1120e52347bdSJani Nikula uart[8250],mmio32be,<addr>[,options] 1121e52347bdSJani Nikula uart[8250],0x<addr>[,options] 1122e52347bdSJani Nikula Start an early, polled-mode console on the 8250/16550 1123e52347bdSJani Nikula UART at the specified I/O port or MMIO address. 1124e52347bdSJani Nikula MMIO inter-register address stride is either 8-bit 1125e52347bdSJani Nikula (mmio) or 32-bit (mmio32 or mmio32be). 1126e52347bdSJani Nikula If none of [io|mmio|mmio32|mmio32be], <addr> is assumed 1127e52347bdSJani Nikula to be equivalent to 'mmio'. 'options' are specified 1128e52347bdSJani Nikula in the same format described for "console=ttyS<n>"; if 1129e52347bdSJani Nikula unspecified, the h/w is not initialized. 1130e52347bdSJani Nikula 1131e52347bdSJani Nikula pl011,<addr> 1132e52347bdSJani Nikula pl011,mmio32,<addr> 1133e52347bdSJani Nikula Start an early, polled-mode console on a pl011 serial 1134e52347bdSJani Nikula port at the specified address. The pl011 serial port 1135e52347bdSJani Nikula must already be setup and configured. Options are not 1136e52347bdSJani Nikula yet supported. If 'mmio32' is specified, then only 1137e52347bdSJani Nikula the driver will use only 32-bit accessors to read/write 1138e52347bdSJani Nikula the device registers. 1139e52347bdSJani Nikula 11404bc2bd5aSStafford Horne liteuart,<addr> 11414bc2bd5aSStafford Horne Start an early console on a litex serial port at the 11424bc2bd5aSStafford Horne specified address. The serial port must already be 11434bc2bd5aSStafford Horne setup and configured. Options are not yet supported. 11444bc2bd5aSStafford Horne 1145e52347bdSJani Nikula meson,<addr> 1146e52347bdSJani Nikula Start an early, polled-mode console on a meson serial 1147e52347bdSJani Nikula port at the specified address. The serial port must 1148e52347bdSJani Nikula already be setup and configured. Options are not yet 1149e52347bdSJani Nikula supported. 1150e52347bdSJani Nikula 1151e52347bdSJani Nikula msm_serial,<addr> 1152e52347bdSJani Nikula Start an early, polled-mode console on an msm serial 1153e52347bdSJani Nikula port at the specified address. The serial port 1154e52347bdSJani Nikula must already be setup and configured. Options are not 1155e52347bdSJani Nikula yet supported. 1156e52347bdSJani Nikula 1157e52347bdSJani Nikula msm_serial_dm,<addr> 1158e52347bdSJani Nikula Start an early, polled-mode console on an msm serial 1159e52347bdSJani Nikula dm port at the specified address. The serial port 1160e52347bdSJani Nikula must already be setup and configured. Options are not 1161e52347bdSJani Nikula yet supported. 1162e52347bdSJani Nikula 1163e36361d7SAndreas Färber owl,<addr> 1164e36361d7SAndreas Färber Start an early, polled-mode console on a serial port 1165e36361d7SAndreas Färber of an Actions Semi SoC, such as S500 or S900, at the 1166e36361d7SAndreas Färber specified address. The serial port must already be 1167e36361d7SAndreas Färber setup and configured. Options are not yet supported. 1168e36361d7SAndreas Färber 1169c10b1332SManivannan Sadhasivam rda,<addr> 1170c10b1332SManivannan Sadhasivam Start an early, polled-mode console on a serial port 1171c10b1332SManivannan Sadhasivam of an RDA Micro SoC, such as RDA8810PL, at the 1172c10b1332SManivannan Sadhasivam specified address. The serial port must already be 1173c10b1332SManivannan Sadhasivam setup and configured. Options are not yet supported. 1174c10b1332SManivannan Sadhasivam 117582f12ab3SPalmer Dabbelt sbi 117682f12ab3SPalmer Dabbelt Use RISC-V SBI (Supervisor Binary Interface) for early 117782f12ab3SPalmer Dabbelt console. 117882f12ab3SPalmer Dabbelt 1179e52347bdSJani Nikula smh Use ARM semihosting calls for early console. 1180e52347bdSJani Nikula 1181e52347bdSJani Nikula s3c2410,<addr> 1182e52347bdSJani Nikula s3c2412,<addr> 1183e52347bdSJani Nikula s3c2440,<addr> 1184e52347bdSJani Nikula s3c6400,<addr> 1185e52347bdSJani Nikula s5pv210,<addr> 1186e52347bdSJani Nikula exynos4210,<addr> 1187e52347bdSJani Nikula Use early console provided by serial driver available 1188e52347bdSJani Nikula on Samsung SoCs, requires selecting proper type and 1189e52347bdSJani Nikula a correct base address of the selected UART port. The 1190e52347bdSJani Nikula serial port must already be setup and configured. 1191e52347bdSJani Nikula Options are not yet supported. 1192e52347bdSJani Nikula 1193ec84aa0aSMartin Blumenstingl lantiq,<addr> 1194ec84aa0aSMartin Blumenstingl Start an early, polled-mode console on a lantiq serial 1195ec84aa0aSMartin Blumenstingl (lqasc) port at the specified address. The serial port 1196ec84aa0aSMartin Blumenstingl must already be setup and configured. Options are not 1197ec84aa0aSMartin Blumenstingl yet supported. 1198ec84aa0aSMartin Blumenstingl 1199e52347bdSJani Nikula lpuart,<addr> 1200e52347bdSJani Nikula lpuart32,<addr> 1201e52347bdSJani Nikula Use early console provided by Freescale LP UART driver 1202e52347bdSJani Nikula found on Freescale Vybrid and QorIQ LS1021A processors. 1203e52347bdSJani Nikula A valid base address must be provided, and the serial 1204e52347bdSJani Nikula port must already be setup and configured. 1205e52347bdSJani Nikula 12067fe068dbSJonathan Neuschäfer ec_imx21,<addr> 12077fe068dbSJonathan Neuschäfer ec_imx6q,<addr> 12087fe068dbSJonathan Neuschäfer Start an early, polled-mode, output-only console on the 12097fe068dbSJonathan Neuschäfer Freescale i.MX UART at the specified address. The UART 12107fe068dbSJonathan Neuschäfer must already be setup and configured. 12117fe068dbSJonathan Neuschäfer 1212f7c864e7SAndre Przywara ar3700_uart,<addr> 1213e52347bdSJani Nikula Start an early, polled-mode console on the 1214e52347bdSJani Nikula Armada 3700 serial port at the specified 1215e52347bdSJani Nikula address. The serial port must already be setup 1216e52347bdSJani Nikula and configured. Options are not yet supported. 1217e52347bdSJani Nikula 121843f1831bSKarthikeyan Ramasubramanian qcom_geni,<addr> 121943f1831bSKarthikeyan Ramasubramanian Start an early, polled-mode console on a Qualcomm 122043f1831bSKarthikeyan Ramasubramanian Generic Interface (GENI) based serial port at the 122143f1831bSKarthikeyan Ramasubramanian specified address. The serial port must already be 122243f1831bSKarthikeyan Ramasubramanian setup and configured. Options are not yet supported. 122343f1831bSKarthikeyan Ramasubramanian 122469c1f396SArd Biesheuvel efifb,[options] 122569c1f396SArd Biesheuvel Start an early, unaccelerated console on the EFI 122669c1f396SArd Biesheuvel memory mapped framebuffer (if available). On cache 122769c1f396SArd Biesheuvel coherent non-x86 systems that use system memory for 122869c1f396SArd Biesheuvel the framebuffer, pass the 'ram' option so that it is 122969c1f396SArd Biesheuvel mapped with the correct attributes. 123069c1f396SArd Biesheuvel 123109864c1cSStefan-gabriel Mirea linflex,<addr> 12329905f32aSStefan-Gabriel Mirea Use early console provided by Freescale LINFlexD UART 123309864c1cSStefan-gabriel Mirea serial driver for NXP S32V234 SoCs. A valid base 123409864c1cSStefan-gabriel Mirea address must be provided, and the serial port must 123509864c1cSStefan-gabriel Mirea already be setup and configured. 123609864c1cSStefan-gabriel Mirea 12374ba66a97SArnd Bergmann earlyprintk= [X86,SH,ARM,M68k,S390] 1238e52347bdSJani Nikula earlyprintk=vga 123989175cf7SHeiko Carstens earlyprintk=sclp 1240e52347bdSJani Nikula earlyprintk=xen 1241e52347bdSJani Nikula earlyprintk=serial[,ttySn[,baudrate]] 1242e52347bdSJani Nikula earlyprintk=serial[,0x...[,baudrate]] 1243e52347bdSJani Nikula earlyprintk=ttySn[,baudrate] 1244e52347bdSJani Nikula earlyprintk=dbgp[debugController#] 1245d2266bbfSFeng Tang earlyprintk=pciserial[,force],bus:device.function[,baudrate] 12461b5aeebfSLu Baolu earlyprintk=xdbc[xhciController#] 1247e52347bdSJani Nikula 1248e52347bdSJani Nikula earlyprintk is useful when the kernel crashes before 1249e52347bdSJani Nikula the normal console is initialized. It is not enabled by 1250e52347bdSJani Nikula default because it has some cosmetic problems. 1251e52347bdSJani Nikula 1252e52347bdSJani Nikula Append ",keep" to not disable it when the real console 1253e52347bdSJani Nikula takes over. 1254e52347bdSJani Nikula 1255e52347bdSJani Nikula Only one of vga, efi, serial, or usb debug port can 1256e52347bdSJani Nikula be used at a time. 1257e52347bdSJani Nikula 1258e52347bdSJani Nikula Currently only ttyS0 and ttyS1 may be specified by 1259e52347bdSJani Nikula name. Other I/O ports may be explicitly specified 1260e52347bdSJani Nikula on some architectures (x86 and arm at least) by 1261e52347bdSJani Nikula replacing ttySn with an I/O port address, like this: 1262e52347bdSJani Nikula earlyprintk=serial,0x1008,115200 1263e52347bdSJani Nikula You can find the port for a given device in 1264e52347bdSJani Nikula /proc/tty/driver/serial: 1265e52347bdSJani Nikula 2: uart:ST16650V2 port:00001008 irq:18 ... 1266e52347bdSJani Nikula 1267e52347bdSJani Nikula Interaction with the standard serial driver is not 1268e52347bdSJani Nikula very good. 1269e52347bdSJani Nikula 1270e52347bdSJani Nikula The VGA and EFI output is eventually overwritten by 1271e52347bdSJani Nikula the real console. 1272e52347bdSJani Nikula 127342bc9716SJan Beulich The xen option can only be used in Xen domains. 1274e52347bdSJani Nikula 127589175cf7SHeiko Carstens The sclp output can only be used on s390. 127689175cf7SHeiko Carstens 1277d2266bbfSFeng Tang The optional "force" to "pciserial" enables use of a 1278d2266bbfSFeng Tang PCI device even when its classcode is not of the 1279d2266bbfSFeng Tang UART class. 1280d2266bbfSFeng Tang 1281e52347bdSJani Nikula edac_report= [HW,EDAC] Control how to report EDAC event 1282e52347bdSJani Nikula Format: {"on" | "off" | "force"} 1283e52347bdSJani Nikula on: enable EDAC to report H/W event. May be overridden 1284e52347bdSJani Nikula by other higher priority error reporting module. 1285e52347bdSJani Nikula off: disable H/W event reporting through EDAC. 1286e52347bdSJani Nikula force: enforce the use of EDAC to report H/W event. 1287e52347bdSJani Nikula default: on. 1288e52347bdSJani Nikula 1289e52347bdSJani Nikula ekgdboc= [X86,KGDB] Allow early kernel console debugging 1290e52347bdSJani Nikula ekgdboc=kbd 1291e52347bdSJani Nikula 1292e52347bdSJani Nikula This is designed to be used in conjunction with 1293e52347bdSJani Nikula the boot argument: earlyprintk=vga 1294e52347bdSJani Nikula 1295f71fc3bcSDouglas Anderson This parameter works in place of the kgdboc parameter 1296f71fc3bcSDouglas Anderson but can only be used if the backing tty is available 1297f71fc3bcSDouglas Anderson very early in the boot process. For early debugging 1298f71fc3bcSDouglas Anderson via a serial port see kgdboc_earlycon instead. 1299f71fc3bcSDouglas Anderson 1300e52347bdSJani Nikula edd= [EDD] 1301e52347bdSJani Nikula Format: {"off" | "on" | "skip[mbr]"} 1302e52347bdSJani Nikula 1303e52347bdSJani Nikula efi= [EFI] 1304c03f739fSHeinrich Schuchardt Format: { "debug", "disable_early_pci_dma", 1305c03f739fSHeinrich Schuchardt "nochunk", "noruntime", "nosoftreserve", 1306fb1201aeSArd Biesheuvel "novamap", "no_disable_early_pci_dma" } 1307c03f739fSHeinrich Schuchardt debug: enable misc debug output. 1308c03f739fSHeinrich Schuchardt disable_early_pci_dma: disable the busmaster bit on all 1309c03f739fSHeinrich Schuchardt PCI bridges while in the EFI boot stub. 1310e52347bdSJani Nikula nochunk: disable reading files in "chunks" in the EFI 1311e52347bdSJani Nikula boot stub, as chunking can cause problems with some 1312e52347bdSJani Nikula firmware implementations. 1313e52347bdSJani Nikula noruntime : disable EFI runtime services support 1314b617c526SDan Williams nosoftreserve: The EFI_MEMORY_SP (Specific Purpose) 1315b617c526SDan Williams attribute may cause the kernel to reserve the 1316b617c526SDan Williams memory range for a memory mapping driver to 1317b617c526SDan Williams claim. Specify efi=nosoftreserve to disable this 1318b617c526SDan Williams reservation and treat the memory by its base type 1319b617c526SDan Williams (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM"). 1320c03f739fSHeinrich Schuchardt novamap: do not call SetVirtualAddressMap(). 13214444f854SMatthew Garrett no_disable_early_pci_dma: Leave the busmaster bit set 13224444f854SMatthew Garrett on all PCI bridges while in the EFI boot stub 1323e52347bdSJani Nikula 1324e52347bdSJani Nikula efi_no_storage_paranoia [EFI; X86] 1325e52347bdSJani Nikula Using this parameter you can use more than 50% of 1326e52347bdSJani Nikula your efi variable storage. Use this parameter only if 1327e52347bdSJani Nikula you are really sure that your UEFI does sane gc and 1328e52347bdSJani Nikula fulfills the spec otherwise your board may brick. 1329e52347bdSJani Nikula 1330e52347bdSJani Nikula efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] 1331e52347bdSJani Nikula Add arbitrary attribute to specific memory range by 1332e52347bdSJani Nikula updating original EFI memory map. 1333e52347bdSJani Nikula Region of memory which aa attribute is added to is 1334e52347bdSJani Nikula from ss to ss+nn. 1335199c8471SDan Williams 1336e52347bdSJani Nikula If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 1337e52347bdSJani Nikula is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) 1338e52347bdSJani Nikula attribute is added to range 0x100000000-0x180000000 and 1339e52347bdSJani Nikula 0x10a0000000-0x1120000000. 1340e52347bdSJani Nikula 1341199c8471SDan Williams If efi_fake_mem=8G@9G:0x40000 is specified, the 1342199c8471SDan Williams EFI_MEMORY_SP(0x40000) attribute is added to 1343199c8471SDan Williams range 0x240000000-0x43fffffff. 1344199c8471SDan Williams 1345e52347bdSJani Nikula Using this parameter you can do debugging of EFI memmap 1346199c8471SDan Williams related features. For example, you can do debugging of 1347e52347bdSJani Nikula Address Range Mirroring feature even if your box 1348199c8471SDan Williams doesn't support it, or mark specific memory as 1349199c8471SDan Williams "soft reserved". 1350e52347bdSJani Nikula 1351e52347bdSJani Nikula efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT 1352e52347bdSJani Nikula that is to be dynamically loaded by Linux. If there are 1353e52347bdSJani Nikula multiple variables with the same name but with different 1354e52347bdSJani Nikula vendor GUIDs, all of them will be loaded. See 1355cb1aaebeSMauro Carvalho Chehab Documentation/admin-guide/acpi/ssdt-overlays.rst for details. 1356e52347bdSJani Nikula 1357e52347bdSJani Nikula 1358e52347bdSJani Nikula eisa_irq_edge= [PARISC,HW] 1359e52347bdSJani Nikula See header of drivers/parisc/eisa.c. 1360e52347bdSJani Nikula 1361e52347bdSJani Nikula elanfreq= [X86-32] 1362e52347bdSJani Nikula See comment before function elanfreq_setup() in 1363e52347bdSJani Nikula arch/x86/kernel/cpu/cpufreq/elanfreq.c. 1364e52347bdSJani Nikula 1365e52347bdSJani Nikula elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] 1366e52347bdSJani Nikula Specifies physical address of start of kernel core 1367e52347bdSJani Nikula image elf header and optionally the size. Generally 1368e52347bdSJani Nikula kexec loader will pass this option to capture kernel. 1369330d4810SMauro Carvalho Chehab See Documentation/admin-guide/kdump/kdump.rst for details. 1370e52347bdSJani Nikula 1371e52347bdSJani Nikula enable_mtrr_cleanup [X86] 1372e52347bdSJani Nikula The kernel tries to adjust MTRR layout from continuous 1373e52347bdSJani Nikula to discrete, to make X server driver able to add WB 1374e52347bdSJani Nikula entry later. This parameter enables that. 1375e52347bdSJani Nikula 1376e52347bdSJani Nikula enable_timer_pin_1 [X86] 1377e52347bdSJani Nikula Enable PIN 1 of APIC timer 1378e52347bdSJani Nikula Can be useful to work around chipset bugs 1379e52347bdSJani Nikula (in particular on some ATI chipsets). 1380e52347bdSJani Nikula The kernel tries to set a reasonable default. 1381e52347bdSJani Nikula 1382e52347bdSJani Nikula enforcing [SELINUX] Set initial enforcing status. 1383e52347bdSJani Nikula Format: {"0" | "1"} 1384e52347bdSJani Nikula See security/selinux/Kconfig help text. 1385e52347bdSJani Nikula 0 -- permissive (log only, no denials). 1386e52347bdSJani Nikula 1 -- enforcing (deny and log). 1387e52347bdSJani Nikula Default value is 0. 1388d41415ebSStephen Smalley Value can be changed at runtime via 1389d41415ebSStephen Smalley /sys/fs/selinux/enforce. 1390e52347bdSJani Nikula 1391e52347bdSJani Nikula erst_disable [ACPI] 1392e52347bdSJani Nikula Disable Error Record Serialization Table (ERST) 1393e52347bdSJani Nikula support. 1394e52347bdSJani Nikula 1395e52347bdSJani Nikula ether= [HW,NET] Ethernet cards parameters 1396e52347bdSJani Nikula This option is obsoleted by the "netdev=" option, which 1397e52347bdSJani Nikula has equivalent usage. See its documentation for details. 1398e52347bdSJani Nikula 1399e52347bdSJani Nikula evm= [EVM] 1400e52347bdSJani Nikula Format: { "fix" } 1401e52347bdSJani Nikula Permit 'security.evm' to be updated regardless of 1402e52347bdSJani Nikula current integrity status. 1403e52347bdSJani Nikula 1404e52347bdSJani Nikula failslab= 14052c739cedSAlbert van der Linde fail_usercopy= 1406e52347bdSJani Nikula fail_page_alloc= 1407e52347bdSJani Nikula fail_make_request=[KNL] 1408e52347bdSJani Nikula General fault injection mechanism. 1409e52347bdSJani Nikula Format: <interval>,<probability>,<space>,<times> 1410e52347bdSJani Nikula See also Documentation/fault-injection/. 1411e52347bdSJani Nikula 1412316cdaa1SMahesh Bandewar fb_tunnels= [NET] 1413316cdaa1SMahesh Bandewar Format: { initns | none } 1414316cdaa1SMahesh Bandewar See Documentation/admin-guide/sysctl/net.rst for 1415316cdaa1SMahesh Bandewar fb_tunnels_only_for_init_ns 1416316cdaa1SMahesh Bandewar 1417e52347bdSJani Nikula floppy= [HW] 1418e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/floppy.rst. 1419e52347bdSJani Nikula 1420e52347bdSJani Nikula force_pal_cache_flush 1421e52347bdSJani Nikula [IA-64] Avoid check_sal_cache_flush which may hang on 1422e52347bdSJani Nikula buggy SAL_CACHE_FLUSH implementations. Using this 1423e52347bdSJani Nikula parameter will force ia64_sal_cache_flush to call 1424e52347bdSJani Nikula ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 1425e52347bdSJani Nikula 1426e52347bdSJani Nikula forcepae [X86-32] 1427e52347bdSJani Nikula Forcefully enable Physical Address Extension (PAE). 1428e52347bdSJani Nikula Many Pentium M systems disable PAE but may have a 1429e52347bdSJani Nikula functionally usable PAE implementation. 1430e52347bdSJani Nikula Warning: use of this parameter will taint the kernel 1431e52347bdSJani Nikula and may cause unknown problems. 1432e52347bdSJani Nikula 1433e52347bdSJani Nikula ftrace=[tracer] 1434e52347bdSJani Nikula [FTRACE] will set and start the specified tracer 1435e52347bdSJani Nikula as early as possible in order to facilitate early 1436e52347bdSJani Nikula boot debugging. 1437e52347bdSJani Nikula 1438e52347bdSJani Nikula ftrace_dump_on_oops[=orig_cpu] 1439e52347bdSJani Nikula [FTRACE] will dump the trace buffers on oops. 1440e52347bdSJani Nikula If no parameter is passed, ftrace will dump 1441e52347bdSJani Nikula buffers of all CPUs, but if you pass orig_cpu, it will 1442e52347bdSJani Nikula dump only the buffer of the CPU that triggered the 1443e52347bdSJani Nikula oops. 1444e52347bdSJani Nikula 1445e52347bdSJani Nikula ftrace_filter=[function-list] 1446e52347bdSJani Nikula [FTRACE] Limit the functions traced by the function 144725942e5eSRandy Dunlap tracer at boot up. function-list is a comma-separated 1448e52347bdSJani Nikula list of functions. This list can be changed at run 1449e52347bdSJani Nikula time by the set_ftrace_filter file in the debugfs 1450e52347bdSJani Nikula tracing directory. 1451e52347bdSJani Nikula 1452e52347bdSJani Nikula ftrace_notrace=[function-list] 1453e52347bdSJani Nikula [FTRACE] Do not trace the functions specified in 1454e52347bdSJani Nikula function-list. This list can be changed at run time 1455e52347bdSJani Nikula by the set_ftrace_notrace file in the debugfs 1456e52347bdSJani Nikula tracing directory. 1457e52347bdSJani Nikula 1458e52347bdSJani Nikula ftrace_graph_filter=[function-list] 1459e52347bdSJani Nikula [FTRACE] Limit the top level callers functions traced 1460e52347bdSJani Nikula by the function graph tracer at boot up. 146125942e5eSRandy Dunlap function-list is a comma-separated list of functions 1462e52347bdSJani Nikula that can be changed at run time by the 1463e52347bdSJani Nikula set_graph_function file in the debugfs tracing directory. 1464e52347bdSJani Nikula 1465e52347bdSJani Nikula ftrace_graph_notrace=[function-list] 1466e52347bdSJani Nikula [FTRACE] Do not trace from the functions specified in 146725942e5eSRandy Dunlap function-list. This list is a comma-separated list of 1468e52347bdSJani Nikula functions that can be changed at run time by the 1469e52347bdSJani Nikula set_graph_notrace file in the debugfs tracing directory. 1470e52347bdSJani Nikula 147165a50c65STodd Brandt ftrace_graph_max_depth=<uint> 147265a50c65STodd Brandt [FTRACE] Used with the function graph tracer. This is 147365a50c65STodd Brandt the max depth it will trace into a function. This value 147465a50c65STodd Brandt can be changed at run time by the max_graph_depth file 147565a50c65STodd Brandt in the tracefs tracing directory. default: 0 (no limit) 147665a50c65STodd Brandt 14778375e74fSSaravana Kannan fw_devlink= [KNL] Create device links between consumer and supplier 14788375e74fSSaravana Kannan devices by scanning the firmware to infer the 14798375e74fSSaravana Kannan consumer/supplier relationships. This feature is 14808375e74fSSaravana Kannan especially useful when drivers are loaded as modules as 14818375e74fSSaravana Kannan it ensures proper ordering of tasks like device probing 14828375e74fSSaravana Kannan (suppliers first, then consumers), supplier boot state 14838375e74fSSaravana Kannan clean up (only after all consumers have probed), 14848375e74fSSaravana Kannan suspend/resume & runtime PM (consumers first, then 14858375e74fSSaravana Kannan suppliers). 14868375e74fSSaravana Kannan Format: { off | permissive | on | rpm } 14878375e74fSSaravana Kannan off -- Don't create device links from firmware info. 14888375e74fSSaravana Kannan permissive -- Create device links from firmware info 14898375e74fSSaravana Kannan but use it only for ordering boot state clean 14908375e74fSSaravana Kannan up (sync_state() calls). 14918375e74fSSaravana Kannan on -- Create device links from firmware info and use it 14928375e74fSSaravana Kannan to enforce probe and suspend/resume ordering. 14938375e74fSSaravana Kannan rpm -- Like "on", but also use to order runtime PM. 14948375e74fSSaravana Kannan 149519d0f5f6SSaravana Kannan fw_devlink.strict=<bool> 149619d0f5f6SSaravana Kannan [KNL] Treat all inferred dependencies as mandatory 149719d0f5f6SSaravana Kannan dependencies. This only applies for fw_devlink=on|rpm. 149819d0f5f6SSaravana Kannan Format: <bool> 149919d0f5f6SSaravana Kannan 1500e52347bdSJani Nikula gamecon.map[2|3]= 1501e52347bdSJani Nikula [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 1502e52347bdSJani Nikula support via parallel port (up to 5 devices per port) 1503e52347bdSJani Nikula Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 15041752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 1505e52347bdSJani Nikula 1506e52347bdSJani Nikula gamma= [HW,DRM] 1507e52347bdSJani Nikula 1508be3a5b0eSRandy Dunlap gart_fix_e820= [X86-64] disable the fix e820 for K8 GART 1509e52347bdSJani Nikula Format: off | on 1510e52347bdSJani Nikula default: on 1511e52347bdSJani Nikula 1512e52347bdSJani Nikula gcov_persist= [GCOV] When non-zero (default), profiling data for 1513e52347bdSJani Nikula kernel modules is saved and remains accessible via 1514e52347bdSJani Nikula debugfs, even when the module is unloaded/reloaded. 1515e52347bdSJani Nikula When zero, profiling data is discarded and associated 1516e52347bdSJani Nikula debugfs files are removed at module unload time. 1517e52347bdSJani Nikula 151847512cfdSThomas Gleixner goldfish [X86] Enable the goldfish android emulator platform. 151947512cfdSThomas Gleixner Don't use this when you are not running on the 152047512cfdSThomas Gleixner android emulator 152147512cfdSThomas Gleixner 15223eb52226SAlexander Dahl gpio-mockup.gpio_mockup_ranges 15233eb52226SAlexander Dahl [HW] Sets the ranges of gpiochip of for this device. 15243eb52226SAlexander Dahl Format: <start1>,<end1>,<start2>,<end2>... 15256984a320SAlexander Dahl gpio-mockup.gpio_mockup_named_lines 15266984a320SAlexander Dahl [HW] Let the driver know GPIO lines should be named. 15273eb52226SAlexander Dahl 1528e52347bdSJani Nikula gpt [EFI] Forces disk with valid GPT signature but 1529e52347bdSJani Nikula invalid Protective MBR to be treated as GPT. If the 1530e52347bdSJani Nikula primary GPT is corrupted, it enables the backup/alternate 1531e52347bdSJani Nikula GPT to be used instead. 1532e52347bdSJani Nikula 1533e52347bdSJani Nikula grcan.enable0= [HW] Configuration of physical interface 0. Determines 1534e52347bdSJani Nikula the "Enable 0" bit of the configuration register. 1535e52347bdSJani Nikula Format: 0 | 1 1536e52347bdSJani Nikula Default: 0 1537e52347bdSJani Nikula grcan.enable1= [HW] Configuration of physical interface 1. Determines 1538e52347bdSJani Nikula the "Enable 0" bit of the configuration register. 1539e52347bdSJani Nikula Format: 0 | 1 1540e52347bdSJani Nikula Default: 0 1541e52347bdSJani Nikula grcan.select= [HW] Select which physical interface to use. 1542e52347bdSJani Nikula Format: 0 | 1 1543e52347bdSJani Nikula Default: 0 1544e52347bdSJani Nikula grcan.txsize= [HW] Sets the size of the tx buffer. 1545e52347bdSJani Nikula Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0. 1546e52347bdSJani Nikula Default: 1024 1547e52347bdSJani Nikula grcan.rxsize= [HW] Sets the size of the rx buffer. 1548e52347bdSJani Nikula Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. 1549e52347bdSJani Nikula Default: 1024 1550e52347bdSJani Nikula 1551e52347bdSJani Nikula hardlockup_all_cpu_backtrace= 1552e52347bdSJani Nikula [KNL] Should the hard-lockup detector generate 1553e52347bdSJani Nikula backtraces on all cpus. 1554f117955aSGuilherme G. Piccoli Format: 0 | 1 1555e52347bdSJani Nikula 1556e52347bdSJani Nikula hashdist= [KNL,NUMA] Large hashes allocated during boot 1557e52347bdSJani Nikula are distributed across NUMA nodes. Defaults on 1558e52347bdSJani Nikula for 64-bit NUMA, off otherwise. 1559e52347bdSJani Nikula Format: 0 | 1 (for off | on) 1560e52347bdSJani Nikula 1561e52347bdSJani Nikula hcl= [IA-64] SGI's Hardware Graph compatibility layer 1562e52347bdSJani Nikula 1563e52347bdSJani Nikula hd= [EIDE] (E)IDE hard drive subsystem geometry 1564e52347bdSJani Nikula Format: <cyl>,<head>,<sect> 1565e52347bdSJani Nikula 1566e52347bdSJani Nikula hest_disable [ACPI] 1567e52347bdSJani Nikula Disable Hardware Error Source Table (HEST) support; 1568e52347bdSJani Nikula corresponding firmware-first mode error processing 1569e52347bdSJani Nikula logic will be disabled. 1570e52347bdSJani Nikula 1571e52347bdSJani Nikula highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 1572e52347bdSJani Nikula size of <nn>. This works even on boxes that have no 1573e52347bdSJani Nikula highmem otherwise. This also works to reduce highmem 1574e52347bdSJani Nikula size on bigger boxes. 1575e52347bdSJani Nikula 1576e52347bdSJani Nikula highres= [KNL] Enable/disable high resolution timer mode. 1577e52347bdSJani Nikula Valid parameters: "on", "off" 1578e52347bdSJani Nikula Default: "on" 1579e52347bdSJani Nikula 1580e52347bdSJani Nikula hlt [BUGS=ARM,SH] 1581e52347bdSJani Nikula 1582e52347bdSJani Nikula hpet= [X86-32,HPET] option to control HPET usage 1583e52347bdSJani Nikula Format: { enable (default) | disable | force | 1584e52347bdSJani Nikula verbose } 1585e52347bdSJani Nikula disable: disable HPET and use PIT instead 1586e52347bdSJani Nikula force: allow force enabled of undocumented chips (ICH4, 1587e52347bdSJani Nikula VIA, nVidia) 1588e52347bdSJani Nikula verbose: show contents of HPET registers during setup 1589e52347bdSJani Nikula 1590e52347bdSJani Nikula hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET 1591e52347bdSJani Nikula registers. Default set by CONFIG_HPET_MMAP_DEFAULT. 1592e52347bdSJani Nikula 1593bc47190dSRandy Dunlap hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation 159438e719abSBaolin Wang of gigantic hugepages. Or using node format, the size 159538e719abSBaolin Wang of a CMA area per node can be specified. 159638e719abSBaolin Wang Format: nn[KMGTPE] or (node format) 159738e719abSBaolin Wang <node>:nn[KMGTPE][,<node>:nn[KMGTPE]] 1598cf11e85fSRoman Gushchin 1599bc47190dSRandy Dunlap Reserve a CMA area of given size and allocate gigantic 1600bc47190dSRandy Dunlap hugepages using the CMA allocator. If enabled, the 1601cf11e85fSRoman Gushchin boot-time allocation of gigantic hugepages is skipped. 1602cf11e85fSRoman Gushchin 1603282f4214SMike Kravetz hugepages= [HW] Number of HugeTLB pages to allocate at boot. 1604282f4214SMike Kravetz If this follows hugepagesz (below), it specifies 1605282f4214SMike Kravetz the number of pages of hugepagesz to be allocated. 1606282f4214SMike Kravetz If this is the first HugeTLB parameter on the command 1607282f4214SMike Kravetz line, it specifies the number of pages to allocate for 1608b5389086SZhenguo Yao the default huge page size. If using node format, the 1609b5389086SZhenguo Yao number of pages to allocate per-node can be specified. 1610b5389086SZhenguo Yao See also Documentation/admin-guide/mm/hugetlbpage.rst. 1611b5389086SZhenguo Yao Format: <integer> or (node format) 1612b5389086SZhenguo Yao <node>:<integer>[,<node>:<integer>] 1613282f4214SMike Kravetz 1614282f4214SMike Kravetz hugepagesz= 1615282f4214SMike Kravetz [HW] The size of the HugeTLB pages. This is used in 1616282f4214SMike Kravetz conjunction with hugepages (above) to allocate huge 1617282f4214SMike Kravetz pages of a specific size at boot. The pair 1618282f4214SMike Kravetz hugepagesz=X hugepages=Y can be specified once for 1619282f4214SMike Kravetz each supported huge page size. Huge page sizes are 1620282f4214SMike Kravetz architecture dependent. See also 1621282f4214SMike Kravetz Documentation/admin-guide/mm/hugetlbpage.rst. 1622282f4214SMike Kravetz Format: size[KMG] 1623e52347bdSJani Nikula 1624e9fdff87SMuchun Song hugetlb_free_vmemmap= 1625e9fdff87SMuchun Song [KNL] Reguires CONFIG_HUGETLB_PAGE_FREE_VMEMMAP 1626e9fdff87SMuchun Song enabled. 1627e9fdff87SMuchun Song Allows heavy hugetlb users to free up some more 1628e9fdff87SMuchun Song memory (6 * PAGE_SIZE for each 2MB hugetlb page). 1629e9fdff87SMuchun Song Format: { on | off (default) } 1630e9fdff87SMuchun Song 1631e9fdff87SMuchun Song on: enable the feature 1632e9fdff87SMuchun Song off: disable the feature 1633e9fdff87SMuchun Song 1634e6d41f12SMuchun Song Built with CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON=y, 1635e6d41f12SMuchun Song the default is on. 1636e6d41f12SMuchun Song 16374bab4964SMuchun Song This is not compatible with memory_hotplug.memmap_on_memory. 16384bab4964SMuchun Song If both parameters are enabled, hugetlb_free_vmemmap takes 16394bab4964SMuchun Song precedence over memory_hotplug.memmap_on_memory. 16404bab4964SMuchun Song 1641a49d9c0aSOmar Sandoval hung_task_panic= 1642a49d9c0aSOmar Sandoval [KNL] Should the hung task detector generate panics. 1643f117955aSGuilherme G. Piccoli Format: 0 | 1 1644a49d9c0aSOmar Sandoval 1645b467f3efSVlastimil Babka A value of 1 instructs the kernel to panic when a 1646a49d9c0aSOmar Sandoval hung task is detected. The default value is controlled 1647a49d9c0aSOmar Sandoval by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time 1648a49d9c0aSOmar Sandoval option. The value selected by this boot parameter can 1649a49d9c0aSOmar Sandoval be changed later by the kernel.hung_task_panic sysctl. 1650a49d9c0aSOmar Sandoval 1651e52347bdSJani Nikula hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) 1652e52347bdSJani Nikula terminal devices. Valid values: 0..8 1653e52347bdSJani Nikula hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. 1654e52347bdSJani Nikula If specified, z/VM IUCV HVC accepts connections 1655e52347bdSJani Nikula from listed z/VM user IDs only. 16563a025de6SYi Sun 16573a025de6SYi Sun hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations 16583a025de6SYi Sun which allow the hypervisor to 'idle' the 16593a025de6SYi Sun guest on lock contention. 16603a025de6SYi Sun 1661e52347bdSJani Nikula keep_bootcon [KNL] 1662e52347bdSJani Nikula Do not unregister boot console at start. This is only 1663e52347bdSJani Nikula useful for debugging when something happens in the window 1664e52347bdSJani Nikula between unregistering the boot console and initializing 1665e52347bdSJani Nikula the real console. 1666e52347bdSJani Nikula 1667e52347bdSJani Nikula i2c_bus= [HW] Override the default board specific I2C bus speed 1668e52347bdSJani Nikula or register an additional I2C bus that is not 1669e52347bdSJani Nikula registered from board initialization code. 1670e52347bdSJani Nikula Format: 1671e52347bdSJani Nikula <bus_id>,<clkrate> 1672e52347bdSJani Nikula 1673e52347bdSJani Nikula i8042.debug [HW] Toggle i8042 debug mode 1674e52347bdSJani Nikula i8042.unmask_kbd_data 1675e52347bdSJani Nikula [HW] Enable printing of interrupt data from the KBD port 1676e52347bdSJani Nikula (disabled by default, and as a pre-condition 1677e52347bdSJani Nikula requires that i8042.debug=1 be enabled) 1678e52347bdSJani Nikula i8042.direct [HW] Put keyboard port into non-translated mode 1679e52347bdSJani Nikula i8042.dumbkbd [HW] Pretend that controller can only read data from 1680e52347bdSJani Nikula keyboard and cannot control its state 1681e52347bdSJani Nikula (Don't attempt to blink the leds) 1682e52347bdSJani Nikula i8042.noaux [HW] Don't check for auxiliary (== mouse) port 1683e52347bdSJani Nikula i8042.nokbd [HW] Don't check/create keyboard port 1684e52347bdSJani Nikula i8042.noloop [HW] Disable the AUX Loopback command while probing 1685e52347bdSJani Nikula for the AUX port 1686e52347bdSJani Nikula i8042.nomux [HW] Don't check presence of an active multiplexing 1687e52347bdSJani Nikula controller 1688e52347bdSJani Nikula i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 1689e52347bdSJani Nikula controllers 1690e52347bdSJani Nikula i8042.notimeout [HW] Ignore timeout condition signalled by controller 1691e52347bdSJani Nikula i8042.reset [HW] Reset the controller during init, cleanup and 1692e52347bdSJani Nikula suspend-to-ram transitions, only during s2r 1693e52347bdSJani Nikula transitions, or never reset 1694e52347bdSJani Nikula Format: { 1 | Y | y | 0 | N | n } 1695e52347bdSJani Nikula 1, Y, y: always reset controller 1696e52347bdSJani Nikula 0, N, n: don't ever reset controller 1697e52347bdSJani Nikula Default: only on s2r transitions on x86; most other 1698e52347bdSJani Nikula architectures force reset to be always executed 1699e52347bdSJani Nikula i8042.unlock [HW] Unlock (ignore) the keylock 1700e52347bdSJani Nikula i8042.kbdreset [HW] Reset device connected to KBD port 1701e52347bdSJani Nikula 1702e52347bdSJani Nikula i810= [HW,DRM] 1703e52347bdSJani Nikula 1704e52347bdSJani Nikula i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 1705e52347bdSJani Nikula indicates that the driver is running on unsupported 1706e52347bdSJani Nikula hardware. 1707e52347bdSJani Nikula i8k.force [HW] Activate i8k driver even if SMM BIOS signature 1708e52347bdSJani Nikula does not match list of supported models. 1709e52347bdSJani Nikula i8k.power_status 1710e52347bdSJani Nikula [HW] Report power status in /proc/i8k 1711e52347bdSJani Nikula (disabled by default) 1712e52347bdSJani Nikula i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 1713e52347bdSJani Nikula capability is set. 1714e52347bdSJani Nikula 1715e52347bdSJani Nikula i915.invert_brightness= 1716e52347bdSJani Nikula [DRM] Invert the sense of the variable that is used to 1717e52347bdSJani Nikula set the brightness of the panel backlight. Normally a 1718e52347bdSJani Nikula brightness value of 0 indicates backlight switched off, 1719e52347bdSJani Nikula and the maximum of the brightness value sets the backlight 1720e52347bdSJani Nikula to maximum brightness. If this parameter is set to 0 1721e52347bdSJani Nikula (default) and the machine requires it, or this parameter 1722e52347bdSJani Nikula is set to 1, a brightness value of 0 sets the backlight 1723e52347bdSJani Nikula to maximum brightness, and the maximum of the brightness 1724e52347bdSJani Nikula value switches the backlight off. 1725e52347bdSJani Nikula -1 -- never invert brightness 1726e52347bdSJani Nikula 0 -- machine default 1727e52347bdSJani Nikula 1 -- force brightness inversion 1728e52347bdSJani Nikula 1729e52347bdSJani Nikula icn= [HW,ISDN] 1730e52347bdSJani Nikula Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 1731e52347bdSJani Nikula 1732e52347bdSJani Nikula ide-core.nodma= [HW] (E)IDE subsystem 1733e52347bdSJani Nikula Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc 1734e52347bdSJani Nikula .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr 1735e52347bdSJani Nikula .cdrom .chs .ignore_cable are additional options 1736d7b461c5SMauro Carvalho Chehab See Documentation/ide/ide.rst. 1737e52347bdSJani Nikula 1738e52347bdSJani Nikula ide-generic.probe-mask= [HW] (E)IDE subsystem 1739e52347bdSJani Nikula Format: <int> 1740e52347bdSJani Nikula Probe mask for legacy ISA IDE ports. Depending on 1741e52347bdSJani Nikula platform up to 6 ports are supported, enabled by 1742e52347bdSJani Nikula setting corresponding bits in the mask to 1. The 1743e52347bdSJani Nikula default value is 0x0, which has a special meaning. 1744e52347bdSJani Nikula On systems that have PCI, it triggers scanning the 1745e52347bdSJani Nikula PCI bus for the first and the second port, which 1746e52347bdSJani Nikula are then probed. On systems without PCI the value 1747e52347bdSJani Nikula of 0x0 enables probing the two first ports as if it 1748e52347bdSJani Nikula was 0x3. 1749e52347bdSJani Nikula 1750e52347bdSJani Nikula ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 1751e52347bdSJani Nikula Claim all unknown PCI IDE storage controllers. 1752e52347bdSJani Nikula 1753e52347bdSJani Nikula idle= [X86] 1754e52347bdSJani Nikula Format: idle=poll, idle=halt, idle=nomwait 1755e52347bdSJani Nikula Poll forces a polling idle loop that can slightly 1756e52347bdSJani Nikula improve the performance of waking up a idle CPU, but 1757e52347bdSJani Nikula will use a lot of power and make the system run hot. 1758e52347bdSJani Nikula Not recommended. 1759e52347bdSJani Nikula idle=halt: Halt is forced to be used for CPU idle. 1760e52347bdSJani Nikula In such case C2/C3 won't be used again. 1761e52347bdSJani Nikula idle=nomwait: Disable mwait for CPU C-states 1762e52347bdSJani Nikula 176303d939c7SDave Jiang idxd.sva= [HW] 176403d939c7SDave Jiang Format: <bool> 176503d939c7SDave Jiang Allow force disabling of Shared Virtual Memory (SVA) 176603d939c7SDave Jiang support for the idxd driver. By default it is set to 176703d939c7SDave Jiang true (1). 176803d939c7SDave Jiang 1769ade8a86bSDave Jiang idxd.tc_override= [HW] 1770ade8a86bSDave Jiang Format: <bool> 1771ade8a86bSDave Jiang Allow override of default traffic class configuration 1772ade8a86bSDave Jiang for the device. By default it is set to false (0). 1773ade8a86bSDave Jiang 1774e52347bdSJani Nikula ieee754= [MIPS] Select IEEE Std 754 conformance mode 1775e52347bdSJani Nikula Format: { strict | legacy | 2008 | relaxed } 1776e52347bdSJani Nikula Default: strict 1777e52347bdSJani Nikula 1778e52347bdSJani Nikula Choose which programs will be accepted for execution 1779e52347bdSJani Nikula based on the IEEE 754 NaN encoding(s) supported by 1780e52347bdSJani Nikula the FPU and the NaN encoding requested with the value 1781e52347bdSJani Nikula of an ELF file header flag individually set by each 1782e52347bdSJani Nikula binary. Hardware implementations are permitted to 1783e52347bdSJani Nikula support either or both of the legacy and the 2008 NaN 1784e52347bdSJani Nikula encoding mode. 1785e52347bdSJani Nikula 1786e52347bdSJani Nikula Available settings are as follows: 1787e52347bdSJani Nikula strict accept binaries that request a NaN encoding 1788e52347bdSJani Nikula supported by the FPU 1789e52347bdSJani Nikula legacy only accept legacy-NaN binaries, if supported 1790e52347bdSJani Nikula by the FPU 1791e52347bdSJani Nikula 2008 only accept 2008-NaN binaries, if supported 1792e52347bdSJani Nikula by the FPU 1793e52347bdSJani Nikula relaxed accept any binaries regardless of whether 1794e52347bdSJani Nikula supported by the FPU 1795e52347bdSJani Nikula 1796e52347bdSJani Nikula The FPU emulator is always able to support both NaN 1797e52347bdSJani Nikula encodings, so if no FPU hardware is present or it has 1798e52347bdSJani Nikula been disabled with 'nofpu', then the settings of 1799e52347bdSJani Nikula 'legacy' and '2008' strap the emulator accordingly, 1800e52347bdSJani Nikula 'relaxed' straps the emulator for both legacy-NaN and 1801e52347bdSJani Nikula 2008-NaN, whereas 'strict' enables legacy-NaN only on 1802e52347bdSJani Nikula legacy processors and both NaN encodings on MIPS32 or 1803e52347bdSJani Nikula MIPS64 CPUs. 1804e52347bdSJani Nikula 1805e52347bdSJani Nikula The setting for ABS.fmt/NEG.fmt instruction execution 1806e52347bdSJani Nikula mode generally follows that for the NaN encoding, 1807e52347bdSJani Nikula except where unsupported by hardware. 1808e52347bdSJani Nikula 1809e52347bdSJani Nikula ignore_loglevel [KNL] 1810e52347bdSJani Nikula Ignore loglevel setting - this will print /all/ 1811e52347bdSJani Nikula kernel messages to the console. Useful for debugging. 1812e52347bdSJani Nikula We also add it as printk module parameter, so users 1813e52347bdSJani Nikula could change it dynamically, usually by 1814e52347bdSJani Nikula /sys/module/printk/parameters/ignore_loglevel. 1815e52347bdSJani Nikula 1816e52347bdSJani Nikula ignore_rlimit_data 1817e52347bdSJani Nikula Ignore RLIMIT_DATA setting for data mappings, 1818e52347bdSJani Nikula print warning at first misuse. Can be changed via 1819e52347bdSJani Nikula /sys/module/kernel/parameters/ignore_rlimit_data. 1820e52347bdSJani Nikula 1821e52347bdSJani Nikula ihash_entries= [KNL] 1822e52347bdSJani Nikula Set number of hash buckets for inode cache. 1823e52347bdSJani Nikula 1824e52347bdSJani Nikula ima_appraise= [IMA] appraise integrity measurements 1825e52347bdSJani Nikula Format: { "off" | "enforce" | "fix" | "log" } 1826e52347bdSJani Nikula default: "enforce" 1827e52347bdSJani Nikula 182841475a3eSPetr Vorel ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead. 1829e52347bdSJani Nikula The builtin appraise policy appraises all files 1830e52347bdSJani Nikula owned by uid=0. 1831e52347bdSJani Nikula 1832d68a6fe9SMimi Zohar ima_canonical_fmt [IMA] 1833d68a6fe9SMimi Zohar Use the canonical format for the binary runtime 1834d68a6fe9SMimi Zohar measurements, instead of host native format. 1835d68a6fe9SMimi Zohar 1836e52347bdSJani Nikula ima_hash= [IMA] 1837e52347bdSJani Nikula Format: { md5 | sha1 | rmd160 | sha256 | sha384 1838e52347bdSJani Nikula | sha512 | ... } 1839e52347bdSJani Nikula default: "sha1" 1840e52347bdSJani Nikula 1841e52347bdSJani Nikula The list of supported hash algorithms is defined 1842e52347bdSJani Nikula in crypto/hash_info.h. 1843e52347bdSJani Nikula 1844e52347bdSJani Nikula ima_policy= [IMA] 184533ce9549SMimi Zohar The builtin policies to load during IMA setup. 18469e67028eSMimi Zohar Format: "tcb | appraise_tcb | secure_boot | 184703cee168SLakshmi Ramasubramanian fail_securely | critical_data" 184833ce9549SMimi Zohar 184933ce9549SMimi Zohar The "tcb" policy measures all programs exec'd, files 185033ce9549SMimi Zohar mmap'd for exec, and all files opened with the read 185133ce9549SMimi Zohar mode bit set by either the effective uid (euid=0) or 185233ce9549SMimi Zohar uid=0. 185333ce9549SMimi Zohar 185433ce9549SMimi Zohar The "appraise_tcb" policy appraises the integrity of 185541475a3eSPetr Vorel all files owned by root. 1856e52347bdSJani Nikula 1857503ceaefSMimi Zohar The "secure_boot" policy appraises the integrity 1858503ceaefSMimi Zohar of files (eg. kexec kernel image, kernel modules, 1859503ceaefSMimi Zohar firmware, policy, etc) based on file signatures. 1860e52347bdSJani Nikula 18619e67028eSMimi Zohar The "fail_securely" policy forces file signature 18629e67028eSMimi Zohar verification failure also on privileged mounted 18639e67028eSMimi Zohar filesystems with the SB_I_UNVERIFIABLE_SIGNATURE 18649e67028eSMimi Zohar flag. 18659e67028eSMimi Zohar 186603cee168SLakshmi Ramasubramanian The "critical_data" policy measures kernel integrity 186703cee168SLakshmi Ramasubramanian critical data. 186803cee168SLakshmi Ramasubramanian 1869e52347bdSJani Nikula ima_tcb [IMA] Deprecated. Use ima_policy= instead. 1870e52347bdSJani Nikula Load a policy which meets the needs of the Trusted 1871e52347bdSJani Nikula Computing Base. This means IMA will measure all 1872e52347bdSJani Nikula programs exec'd, files mmap'd for exec, and all files 1873e52347bdSJani Nikula opened for read by uid=0. 1874e52347bdSJani Nikula 1875e52347bdSJani Nikula ima_template= [IMA] 1876e52347bdSJani Nikula Select one of defined IMA measurements template formats. 1877e52347bdSJani Nikula Formats: { "ima" | "ima-ng" | "ima-sig" } 1878e52347bdSJani Nikula Default: "ima-ng" 1879e52347bdSJani Nikula 1880e52347bdSJani Nikula ima_template_fmt= 1881e52347bdSJani Nikula [IMA] Define a custom template format. 1882e52347bdSJani Nikula Format: { "field1|...|fieldN" } 1883e52347bdSJani Nikula 1884e52347bdSJani Nikula ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage 1885e52347bdSJani Nikula Format: <min_file_size> 1886e52347bdSJani Nikula Set the minimal file size for using asynchronous hash. 1887e52347bdSJani Nikula If left unspecified, ahash usage is disabled. 1888e52347bdSJani Nikula 1889e52347bdSJani Nikula ahash performance varies for different data sizes on 1890e52347bdSJani Nikula different crypto accelerators. This option can be used 1891e52347bdSJani Nikula to achieve the best performance for a particular HW. 1892e52347bdSJani Nikula 1893e52347bdSJani Nikula ima.ahash_bufsize= [IMA] Asynchronous hash buffer size 1894e52347bdSJani Nikula Format: <bufsize> 1895e52347bdSJani Nikula Set hashing buffer size. Default: 4k. 1896e52347bdSJani Nikula 1897e52347bdSJani Nikula ahash performance varies for different chunk sizes on 1898e52347bdSJani Nikula different crypto accelerators. This option can be used 1899e52347bdSJani Nikula to achieve best performance for particular HW. 1900e52347bdSJani Nikula 1901e52347bdSJani Nikula init= [KNL] 1902e52347bdSJani Nikula Format: <full_path> 1903e52347bdSJani Nikula Run specified binary instead of /sbin/init as init 1904e52347bdSJani Nikula process. 1905e52347bdSJani Nikula 1906e52347bdSJani Nikula initcall_debug [KNL] Trace initcalls as they are executed. Useful 1907e52347bdSJani Nikula for working out where the kernel is dying during 1908e52347bdSJani Nikula startup. 1909e52347bdSJani Nikula 1910e52347bdSJani Nikula initcall_blacklist= [KNL] Do not execute a comma-separated list of 1911e52347bdSJani Nikula initcall functions. Useful for debugging built-in 1912e52347bdSJani Nikula modules and initcalls. 1913e52347bdSJani Nikula 1914e7cb072eSRasmus Villemoes initramfs_async= [KNL] 1915e7cb072eSRasmus Villemoes Format: <bool> 1916e7cb072eSRasmus Villemoes Default: 1 1917e7cb072eSRasmus Villemoes This parameter controls whether the initramfs 1918e7cb072eSRasmus Villemoes image is unpacked asynchronously, concurrently 1919e7cb072eSRasmus Villemoes with devices being probed and 1920e7cb072eSRasmus Villemoes initialized. This should normally just work, 1921e7cb072eSRasmus Villemoes but as a debugging aid, one can get the 1922e7cb072eSRasmus Villemoes historical behaviour of the initramfs 1923e7cb072eSRasmus Villemoes unpacking being completed before device_ and 1924e7cb072eSRasmus Villemoes late_ initcalls. 1925e7cb072eSRasmus Villemoes 1926e52347bdSJani Nikula initrd= [BOOT] Specify the location of the initial ramdisk 1927e52347bdSJani Nikula 1928694cfd87SRonald G. Minnich initrdmem= [KNL] Specify a physical address and size from which to 1929694cfd87SRonald G. Minnich load the initrd. If an initrd is compiled in or 1930694cfd87SRonald G. Minnich specified in the bootparams, it takes priority over this 1931694cfd87SRonald G. Minnich setting. 1932694cfd87SRonald G. Minnich Format: ss[KMG],nn[KMG] 1933694cfd87SRonald G. Minnich Default is 0, 0 1934694cfd87SRonald G. Minnich 19356471384aSAlexander Potapenko init_on_alloc= [MM] Fill newly allocated pages and heap objects with 19366471384aSAlexander Potapenko zeroes. 19376471384aSAlexander Potapenko Format: 0 | 1 19386471384aSAlexander Potapenko Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON. 19396471384aSAlexander Potapenko 19406471384aSAlexander Potapenko init_on_free= [MM] Fill freed pages and heap objects with zeroes. 19416471384aSAlexander Potapenko Format: 0 | 1 19426471384aSAlexander Potapenko Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON. 19436471384aSAlexander Potapenko 1944be3a5b0eSRandy Dunlap init_pkru= [X86] Specify the default memory protection keys rights 1945e52347bdSJani Nikula register contents for all processes. 0x55555554 by 1946e52347bdSJani Nikula default (disallow access to all but pkey 0). Can 1947e52347bdSJani Nikula override in debugfs after boot. 1948e52347bdSJani Nikula 1949e52347bdSJani Nikula inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 1950e52347bdSJani Nikula Format: <irq> 1951e52347bdSJani Nikula 1952be3a5b0eSRandy Dunlap int_pln_enable [X86] Enable power limit notification interrupt 1953e52347bdSJani Nikula 1954e52347bdSJani Nikula integrity_audit=[IMA] 1955e52347bdSJani Nikula Format: { "0" | "1" } 1956e52347bdSJani Nikula 0 -- basic integrity auditing messages. (Default) 1957e52347bdSJani Nikula 1 -- additional integrity auditing messages. 1958e52347bdSJani Nikula 1959e52347bdSJani Nikula intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 1960e52347bdSJani Nikula on 1961e52347bdSJani Nikula Enable intel iommu driver. 1962e52347bdSJani Nikula off 1963e52347bdSJani Nikula Disable intel iommu driver. 1964e52347bdSJani Nikula igfx_off [Default Off] 1965e52347bdSJani Nikula By default, gfx is mapped as normal device. If a gfx 1966e52347bdSJani Nikula device has a dedicated DMAR unit, the DMAR unit is 1967e52347bdSJani Nikula bypassed by not enabling DMAR with this option. In 1968e52347bdSJani Nikula this case, gfx device will use physical address for 1969e52347bdSJani Nikula DMA. 1970e52347bdSJani Nikula strict [Default Off] 19711d479f16SJohn Garry Deprecated, equivalent to iommu.strict=1. 1972e52347bdSJani Nikula sp_off [Default Off] 1973e52347bdSJani Nikula By default, super page will be supported if Intel IOMMU 1974e52347bdSJani Nikula has the capability. With this option, super page will 1975e52347bdSJani Nikula not be supported. 1976792fb43cSLu Baolu sm_on 1977792fb43cSLu Baolu Enable the Intel IOMMU scalable mode if the hardware 1978792fb43cSLu Baolu advertises that it has support for the scalable mode 1979792fb43cSLu Baolu translation. 1980792fb43cSLu Baolu sm_off 1981792fb43cSLu Baolu Disallow use of the Intel IOMMU scalable mode. 1982bfd20f1cSShaohua Li tboot_noforce [Default Off] 1983bfd20f1cSShaohua Li Do not force the Intel IOMMU enabled under tboot. 1984bfd20f1cSShaohua Li By default, tboot will force Intel IOMMU on, which 1985bfd20f1cSShaohua Li could harm performance of some high-throughput 1986bfd20f1cSShaohua Li devices like 40GBit network cards, even if identity 1987bfd20f1cSShaohua Li mapping is enabled. 1988bfd20f1cSShaohua Li Note that using this option lowers the security 1989bfd20f1cSShaohua Li provided by tboot because it makes the system 1990bfd20f1cSShaohua Li vulnerable to DMA attacks. 1991e52347bdSJani Nikula 1992e52347bdSJani Nikula intel_idle.max_cstate= [KNL,HW,ACPI,X86] 1993e52347bdSJani Nikula 0 disables intel_idle and fall back on acpi_idle. 1994e52347bdSJani Nikula 1 to 9 specify maximum depth of C-state. 1995e52347bdSJani Nikula 1996e52347bdSJani Nikula intel_pstate= [X86] 1997e52347bdSJani Nikula disable 1998e52347bdSJani Nikula Do not enable intel_pstate as the default 1999e52347bdSJani Nikula scaling driver for the supported processors 20007b9dc3f7SLinus Torvalds passive 20017b9dc3f7SLinus Torvalds Use intel_pstate as a scaling driver, but configure it 20027b9dc3f7SLinus Torvalds to work with generic cpufreq governors (instead of 20037b9dc3f7SLinus Torvalds enabling its internal governor). This mode cannot be 20047b9dc3f7SLinus Torvalds used along with the hardware-managed P-states (HWP) 20057b9dc3f7SLinus Torvalds feature. 2006e52347bdSJani Nikula force 2007e52347bdSJani Nikula Enable intel_pstate on systems that prohibit it by default 2008e52347bdSJani Nikula in favor of acpi-cpufreq. Forcing the intel_pstate driver 2009e52347bdSJani Nikula instead of acpi-cpufreq may disable platform features, such 2010e52347bdSJani Nikula as thermal controls and power capping, that rely on ACPI 2011e52347bdSJani Nikula P-States information being indicated to OSPM and therefore 2012e52347bdSJani Nikula should be used with caution. This option does not work with 2013e52347bdSJani Nikula processors that aren't supported by the intel_pstate driver 2014e52347bdSJani Nikula or on platforms that use pcc-cpufreq instead of acpi-cpufreq. 2015e52347bdSJani Nikula no_hwp 2016e52347bdSJani Nikula Do not enable hardware P state control (HWP) 2017e52347bdSJani Nikula if available. 2018e52347bdSJani Nikula hwp_only 2019e52347bdSJani Nikula Only load intel_pstate on systems which support 2020e52347bdSJani Nikula hardware P state control (HWP) if available. 2021e52347bdSJani Nikula support_acpi_ppc 2022e52347bdSJani Nikula Enforce ACPI _PPC performance limits. If the Fixed ACPI 2023e52347bdSJani Nikula Description Table, specifies preferred power management 2024e52347bdSJani Nikula profile as "Enterprise Server" or "Performance Server", 2025e52347bdSJani Nikula then this feature is turned on by default. 20267b9dc3f7SLinus Torvalds per_cpu_perf_limits 20277b9dc3f7SLinus Torvalds Allow per-logical-CPU P-State performance control limits using 20287b9dc3f7SLinus Torvalds cpufreq sysfs interface 2029e52347bdSJani Nikula 2030e52347bdSJani Nikula intremap= [X86-64, Intel-IOMMU] 2031e52347bdSJani Nikula on enable Interrupt Remapping (default) 2032e52347bdSJani Nikula off disable Interrupt Remapping 2033e52347bdSJani Nikula nosid disable Source ID checking 2034e52347bdSJani Nikula no_x2apic_optout 2035e52347bdSJani Nikula BIOS x2APIC opt-out request will be ignored 2036e52347bdSJani Nikula nopost disable Interrupt Posting 2037e52347bdSJani Nikula 2038e52347bdSJani Nikula iomem= Disable strict checking of access to MMIO memory 2039e52347bdSJani Nikula strict regions from userspace. 2040e52347bdSJani Nikula relaxed 2041e52347bdSJani Nikula 2042be3a5b0eSRandy Dunlap iommu= [X86] 2043e52347bdSJani Nikula off 2044e52347bdSJani Nikula force 2045e52347bdSJani Nikula noforce 2046e52347bdSJani Nikula biomerge 2047e52347bdSJani Nikula panic 2048e52347bdSJani Nikula nopanic 2049e52347bdSJani Nikula merge 2050e52347bdSJani Nikula nomerge 2051e52347bdSJani Nikula soft 2052be3a5b0eSRandy Dunlap pt [X86] 2053be3a5b0eSRandy Dunlap nopt [X86] 2054e52347bdSJani Nikula nobypass [PPC/POWERNV] 2055e52347bdSJani Nikula Disable IOMMU bypass, using IOMMU for PCI devices. 2056e52347bdSJani Nikula 20573542dcb1SRobin Murphy iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices. 20583542dcb1SRobin Murphy Format: { "0" | "1" } 20593542dcb1SRobin Murphy 0 - Try to allocate a 32-bit DMA address first, before 20603542dcb1SRobin Murphy falling back to the full range if needed. 20613542dcb1SRobin Murphy 1 - Allocate directly from the full usable range, 20623542dcb1SRobin Murphy forcing Dual Address Cycle for PCI cards supporting 20633542dcb1SRobin Murphy greater than 32-bit addressing. 20643542dcb1SRobin Murphy 2065531353e6SRobin Murphy iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour 206668a6efe8SZhen Lei Format: { "0" | "1" } 206768a6efe8SZhen Lei 0 - Lazy mode. 206868a6efe8SZhen Lei Request that DMA unmap operations use deferred 206968a6efe8SZhen Lei invalidation of hardware TLBs, for increased 207068a6efe8SZhen Lei throughput at the cost of reduced device isolation. 207168a6efe8SZhen Lei Will fall back to strict mode if not supported by 207268a6efe8SZhen Lei the relevant IOMMU driver. 2073712d8f20SZhen Lei 1 - Strict mode. 207468a6efe8SZhen Lei DMA unmap operations invalidate IOMMU hardware TLBs 207568a6efe8SZhen Lei synchronously. 2076e96763ecSRobin Murphy unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}. 2077e96763ecSRobin Murphy Note: on x86, strict mode specified via one of the 2078e96763ecSRobin Murphy legacy driver-specific options takes precedence. 207968a6efe8SZhen Lei 2080fccb4e3bSWill Deacon iommu.passthrough= 2081c8fb436bSJoerg Roedel [ARM64, X86] Configure DMA to bypass the IOMMU by default. 2082fccb4e3bSWill Deacon Format: { "0" | "1" } 2083fccb4e3bSWill Deacon 0 - Use IOMMU translation for DMA. 2084fccb4e3bSWill Deacon 1 - Bypass the IOMMU for DMA. 20859d723b4cSRobin Murphy unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. 2086e52347bdSJani Nikula 20877c42376eSRandy Dunlap io7= [HW] IO7 for Marvel-based Alpha systems 2088e52347bdSJani Nikula See comment before marvel_specify_io7 in 2089e52347bdSJani Nikula arch/alpha/kernel/core_marvel.c. 2090e52347bdSJani Nikula 2091e52347bdSJani Nikula io_delay= [X86] I/O delay method 2092e52347bdSJani Nikula 0x80 2093e52347bdSJani Nikula Standard port 0x80 based delay 2094e52347bdSJani Nikula 0xed 2095e52347bdSJani Nikula Alternate port 0xed based delay (needed on some systems) 2096e52347bdSJani Nikula udelay 2097e52347bdSJani Nikula Simple two microseconds delay 2098e52347bdSJani Nikula none 2099e52347bdSJani Nikula No delay 2100e52347bdSJani Nikula 2101e52347bdSJani Nikula ip= [IP_PNP] 21023eb30c51SNiklas Söderlund See Documentation/admin-guide/nfs/nfsroot.rst. 2103e52347bdSJani Nikula 21045ac893b8SWaiman Long ipcmni_extend [KNL] Extend the maximum number of unique System V 21055ac893b8SWaiman Long IPC identifiers from 32,768 to 16,777,216. 21065ac893b8SWaiman Long 2107e52347bdSJani Nikula irqaffinity= [SMP] Set the default irq affinity mask 2108e52347bdSJani Nikula The argument is a cpu list, as described above. 2109e52347bdSJani Nikula 21100962289bSMarc Zyngier irqchip.gicv2_force_probe= 21110962289bSMarc Zyngier [ARM, ARM64] 21120962289bSMarc Zyngier Format: <bool> 21130962289bSMarc Zyngier Force the kernel to look for the second 4kB page 21140962289bSMarc Zyngier of a GICv2 controller even if the memory range 21150962289bSMarc Zyngier exposed by the device tree is too small. 21160962289bSMarc Zyngier 2117f736d65dSMarc Zyngier irqchip.gicv3_nolpi= 2118f736d65dSMarc Zyngier [ARM, ARM64] 2119f736d65dSMarc Zyngier Force the kernel to ignore the availability of 2120f736d65dSMarc Zyngier LPIs (and by consequence ITSs). Intended for system 2121f736d65dSMarc Zyngier that use the kernel as a bootloader, and thus want 2122f736d65dSMarc Zyngier to let secondary kernels in charge of setting up 2123f736d65dSMarc Zyngier LPIs. 2124f736d65dSMarc Zyngier 2125bc3c03ccSJulien Thierry irqchip.gicv3_pseudo_nmi= [ARM64] 2126bc3c03ccSJulien Thierry Enables support for pseudo-NMIs in the kernel. This 2127bc3c03ccSJulien Thierry requires the kernel to be built with 2128bc3c03ccSJulien Thierry CONFIG_ARM64_PSEUDO_NMI. 2129bc3c03ccSJulien Thierry 2130e52347bdSJani Nikula irqfixup [HW] 2131e52347bdSJani Nikula When an interrupt is not handled search all handlers 2132e52347bdSJani Nikula for it. Intended to get systems with badly broken 2133e52347bdSJani Nikula firmware running. 2134e52347bdSJani Nikula 2135e52347bdSJani Nikula irqpoll [HW] 2136e52347bdSJani Nikula When an interrupt is not handled search all handlers 2137e52347bdSJani Nikula for it. Also check all handlers each timer 2138e52347bdSJani Nikula interrupt. Intended to get systems with badly broken 2139e52347bdSJani Nikula firmware running. 2140e52347bdSJani Nikula 2141e52347bdSJani Nikula isapnp= [ISAPNP] 2142e52347bdSJani Nikula Format: <RDP>,<reset>,<pci_scan>,<verbosity> 2143e52347bdSJani Nikula 2144d94d1053SFrederic Weisbecker isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance. 2145b0d40d2bSFrederic Weisbecker [Deprecated - use cpusets instead] 2146b0d40d2bSFrederic Weisbecker Format: [flag-list,]<cpu-list> 2147e52347bdSJani Nikula 2148b0d40d2bSFrederic Weisbecker Specify one or more CPUs to isolate from disturbances 2149b0d40d2bSFrederic Weisbecker specified in the flag list (default: domain): 2150b0d40d2bSFrederic Weisbecker 2151b0d40d2bSFrederic Weisbecker nohz 2152b0d40d2bSFrederic Weisbecker Disable the tick when a single task runs. 2153083c6eeaSFrederic Weisbecker 2154083c6eeaSFrederic Weisbecker A residual 1Hz tick is offloaded to workqueues, which you 2155083c6eeaSFrederic Weisbecker need to affine to housekeeping through the global 2156083c6eeaSFrederic Weisbecker workqueue's affinity configured via the 2157083c6eeaSFrederic Weisbecker /sys/devices/virtual/workqueue/cpumask sysfs file, or 2158083c6eeaSFrederic Weisbecker by using the 'domain' flag described below. 2159083c6eeaSFrederic Weisbecker 2160083c6eeaSFrederic Weisbecker NOTE: by default the global workqueue runs on all CPUs, 2161083c6eeaSFrederic Weisbecker so to protect individual CPUs the 'cpumask' file has to 2162083c6eeaSFrederic Weisbecker be configured manually after bootup. 2163083c6eeaSFrederic Weisbecker 2164b0d40d2bSFrederic Weisbecker domain 2165b0d40d2bSFrederic Weisbecker Isolate from the general SMP balancing and scheduling 2166b0d40d2bSFrederic Weisbecker algorithms. Note that performing domain isolation this way 2167b0d40d2bSFrederic Weisbecker is irreversible: it's not possible to bring back a CPU to 2168b0d40d2bSFrederic Weisbecker the domains once isolated through isolcpus. It's strongly 2169b0d40d2bSFrederic Weisbecker advised to use cpusets instead to disable scheduler load 2170b0d40d2bSFrederic Weisbecker balancing through the "cpuset.sched_load_balance" file. 2171b0d40d2bSFrederic Weisbecker It offers a much more flexible interface where CPUs can 2172b0d40d2bSFrederic Weisbecker move in and out of an isolated set anytime. 2173b0d40d2bSFrederic Weisbecker 2174b0d40d2bSFrederic Weisbecker You can move a process onto or off an "isolated" CPU via 2175b0d40d2bSFrederic Weisbecker the CPU affinity syscalls or cpuset. 2176e52347bdSJani Nikula <cpu number> begins at 0 and the maximum value is 2177e52347bdSJani Nikula "number of CPUs in system - 1". 2178e52347bdSJani Nikula 217911ea68f5SMing Lei managed_irq 218011ea68f5SMing Lei 218111ea68f5SMing Lei Isolate from being targeted by managed interrupts 218211ea68f5SMing Lei which have an interrupt mask containing isolated 218311ea68f5SMing Lei CPUs. The affinity of managed interrupts is 218411ea68f5SMing Lei handled by the kernel and cannot be changed via 218511ea68f5SMing Lei the /proc/irq/* interfaces. 218611ea68f5SMing Lei 218711ea68f5SMing Lei This isolation is best effort and only effective 218811ea68f5SMing Lei if the automatically assigned interrupt mask of a 218911ea68f5SMing Lei device queue contains isolated and housekeeping 219011ea68f5SMing Lei CPUs. If housekeeping CPUs are online then such 219111ea68f5SMing Lei interrupts are directed to the housekeeping CPU 219211ea68f5SMing Lei so that IO submitted on the housekeeping CPU 219311ea68f5SMing Lei cannot disturb the isolated CPU. 219411ea68f5SMing Lei 219511ea68f5SMing Lei If a queue's affinity mask contains only isolated 219611ea68f5SMing Lei CPUs then this parameter has no effect on the 219711ea68f5SMing Lei interrupt routing decision, though interrupts are 219811ea68f5SMing Lei only delivered when tasks running on those 219911ea68f5SMing Lei isolated CPUs submit IO. IO submitted on 220011ea68f5SMing Lei housekeeping CPUs has no influence on those 220111ea68f5SMing Lei queues. 220211ea68f5SMing Lei 2203b0d40d2bSFrederic Weisbecker The format of <cpu-list> is described above. 2204b0d40d2bSFrederic Weisbecker 2205e52347bdSJani Nikula iucv= [HW,NET] 2206e52347bdSJani Nikula 2207be3a5b0eSRandy Dunlap ivrs_ioapic [HW,X86-64] 2208e52347bdSJani Nikula Provide an override to the IOAPIC-ID<->DEVICE-ID 2209e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 2210e52347bdSJani Nikula example, to map IOAPIC-ID decimal 10 to 2211e52347bdSJani Nikula PCI device 00:14.0 write the parameter as: 2212e52347bdSJani Nikula ivrs_ioapic[10]=00:14.0 2213e52347bdSJani Nikula 2214be3a5b0eSRandy Dunlap ivrs_hpet [HW,X86-64] 2215e52347bdSJani Nikula Provide an override to the HPET-ID<->DEVICE-ID 2216e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 2217e52347bdSJani Nikula example, to map HPET-ID decimal 0 to 2218e52347bdSJani Nikula PCI device 00:14.0 write the parameter as: 2219e52347bdSJani Nikula ivrs_hpet[0]=00:14.0 2220e52347bdSJani Nikula 2221be3a5b0eSRandy Dunlap ivrs_acpihid [HW,X86-64] 2222e52347bdSJani Nikula Provide an override to the ACPI-HID:UID<->DEVICE-ID 2223e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 2224e52347bdSJani Nikula example, to map UART-HID:UID AMD0020:0 to 2225e52347bdSJani Nikula PCI device 00:14.5 write the parameter as: 2226e52347bdSJani Nikula ivrs_acpihid[00:14.5]=AMD0020:0 2227e52347bdSJani Nikula 2228e52347bdSJani Nikula js= [HW,JOY] Analog joystick 22291752118dSTom Saeger See Documentation/input/joydev/joystick.rst. 2230e52347bdSJani Nikula 2231e52347bdSJani Nikula nokaslr [KNL] 2232e52347bdSJani Nikula When CONFIG_RANDOMIZE_BASE is set, this disables 2233e52347bdSJani Nikula kernel and module base offset ASLR (Address Space 2234e52347bdSJani Nikula Layout Randomization). 2235e52347bdSJani Nikula 2236b0845ce5SMark Rutland kasan_multi_shot 2237b0845ce5SMark Rutland [KNL] Enforce KASAN (Kernel Address Sanitizer) to print 2238b0845ce5SMark Rutland report on every invalid memory access. Without this 2239b0845ce5SMark Rutland parameter KASAN will print report only for the first 2240b0845ce5SMark Rutland invalid access. 2241b0845ce5SMark Rutland 2242e52347bdSJani Nikula keepinitrd [HW,ARM] 2243e52347bdSJani Nikula 2244e52347bdSJani Nikula kernelcore= [KNL,X86,IA-64,PPC] 2245a5c6d650SDavid Rientjes Format: nn[KMGTPE] | nn% | "mirror" 2246a5c6d650SDavid Rientjes This parameter specifies the amount of memory usable by 2247a5c6d650SDavid Rientjes the kernel for non-movable allocations. The requested 2248a5c6d650SDavid Rientjes amount is spread evenly throughout all nodes in the 2249a5c6d650SDavid Rientjes system as ZONE_NORMAL. The remaining memory is used for 2250a5c6d650SDavid Rientjes movable memory in its own zone, ZONE_MOVABLE. In the 2251a5c6d650SDavid Rientjes event, a node is too small to have both ZONE_NORMAL and 2252a5c6d650SDavid Rientjes ZONE_MOVABLE, kernelcore memory will take priority and 2253a5c6d650SDavid Rientjes other nodes will have a larger ZONE_MOVABLE. 2254a5c6d650SDavid Rientjes 2255a5c6d650SDavid Rientjes ZONE_MOVABLE is used for the allocation of pages that 2256a5c6d650SDavid Rientjes may be reclaimed or moved by the page migration 2257a5c6d650SDavid Rientjes subsystem. Note that allocations like PTEs-from-HighMem 2258a5c6d650SDavid Rientjes still use the HighMem zone if it exists, and the Normal 2259e52347bdSJani Nikula zone if it does not. 2260e52347bdSJani Nikula 2261a5c6d650SDavid Rientjes It is possible to specify the exact amount of memory in 2262a5c6d650SDavid Rientjes the form of "nn[KMGTPE]", a percentage of total system 2263a5c6d650SDavid Rientjes memory in the form of "nn%", or "mirror". If "mirror" 2264e52347bdSJani Nikula option is specified, mirrored (reliable) memory is used 2265e52347bdSJani Nikula for non-movable allocations and remaining memory is used 2266a5c6d650SDavid Rientjes for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" 2267a5c6d650SDavid Rientjes are exclusive, so you cannot specify multiple forms. 2268e52347bdSJani Nikula 2269e52347bdSJani Nikula kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. 2270e52347bdSJani Nikula Format: <Controller#>[,poll interval] 2271e52347bdSJani Nikula The controller # is the number of the ehci usb debug 2272e52347bdSJani Nikula port as it is probed via PCI. The poll interval is 2273e52347bdSJani Nikula optional and is the number seconds in between 2274e52347bdSJani Nikula each poll cycle to the debug port in case you need 2275e52347bdSJani Nikula the functionality for interrupting the kernel with 2276e52347bdSJani Nikula gdb or control-c on the dbgp connection. When 2277e52347bdSJani Nikula not using this parameter you use sysrq-g to break into 2278e52347bdSJani Nikula the kernel debugger. 2279e52347bdSJani Nikula 2280e52347bdSJani Nikula kgdboc= [KGDB,HW] kgdb over consoles. 2281e52347bdSJani Nikula Requires a tty driver that supports console polling, 2282e52347bdSJani Nikula or a supported polling keyboard driver (non-usb). 2283e52347bdSJani Nikula Serial only format: <serial_device>[,baud] 2284e52347bdSJani Nikula keyboard only format: kbd 2285e52347bdSJani Nikula keyboard and serial format: kbd,<serial_device>[,baud] 2286e52347bdSJani Nikula Optional Kernel mode setting: 2287e52347bdSJani Nikula kms, kbd format: kms,kbd 2288e52347bdSJani Nikula kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] 2289e52347bdSJani Nikula 2290f71fc3bcSDouglas Anderson kgdboc_earlycon= [KGDB,HW] 2291f71fc3bcSDouglas Anderson If the boot console provides the ability to read 2292f71fc3bcSDouglas Anderson characters and can work in polling mode, you can use 2293f71fc3bcSDouglas Anderson this parameter to tell kgdb to use it as a backend 2294f71fc3bcSDouglas Anderson until the normal console is registered. Intended to 2295f71fc3bcSDouglas Anderson be used together with the kgdboc parameter which 2296f71fc3bcSDouglas Anderson specifies the normal console to transition to. 2297f71fc3bcSDouglas Anderson 2298f71fc3bcSDouglas Anderson The name of the early console should be specified 2299f71fc3bcSDouglas Anderson as the value of this parameter. Note that the name of 2300f71fc3bcSDouglas Anderson the early console might be different than the tty 2301f71fc3bcSDouglas Anderson name passed to kgdboc. It's OK to leave the value 2302f71fc3bcSDouglas Anderson blank and the first boot console that implements 2303f71fc3bcSDouglas Anderson read() will be picked. 2304f71fc3bcSDouglas Anderson 2305e52347bdSJani Nikula kgdbwait [KGDB] Stop kernel execution and enter the 2306e52347bdSJani Nikula kernel debugger at the earliest opportunity. 2307e52347bdSJani Nikula 2308497de97eSRandy Dunlap kmac= [MIPS] Korina ethernet MAC address. 2309e52347bdSJani Nikula Configure the RouterBoard 532 series on-chip 2310e52347bdSJani Nikula Ethernet adapter MAC address. 2311e52347bdSJani Nikula 2312e52347bdSJani Nikula kmemleak= [KNL] Boot-time kmemleak enable/disable 2313e52347bdSJani Nikula Valid arguments: on, off 2314e52347bdSJani Nikula Default: on 2315e52347bdSJani Nikula Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, 2316e52347bdSJani Nikula the default is off. 2317e52347bdSJani Nikula 2318970988e1SMasami Hiramatsu kprobe_event=[probe-list] 2319970988e1SMasami Hiramatsu [FTRACE] Add kprobe events and enable at boot time. 2320970988e1SMasami Hiramatsu The probe-list is a semicolon delimited list of probe 2321970988e1SMasami Hiramatsu definitions. Each definition is same as kprobe_events 2322970988e1SMasami Hiramatsu interface, but the parameters are comma delimited. 2323970988e1SMasami Hiramatsu For example, to add a kprobe event on vfs_read with 2324970988e1SMasami Hiramatsu arg1 and arg2, add to the command line; 2325970988e1SMasami Hiramatsu 2326970988e1SMasami Hiramatsu kprobe_event=p,vfs_read,$arg1,$arg2 2327970988e1SMasami Hiramatsu 2328970988e1SMasami Hiramatsu See also Documentation/trace/kprobetrace.rst "Kernel 2329970988e1SMasami Hiramatsu Boot Parameter" section. 2330970988e1SMasami Hiramatsu 2331de190555SJeremy Linton kpti= [ARM64] Control page table isolation of user 2332de190555SJeremy Linton and kernel address spaces. 2333de190555SJeremy Linton Default: enabled on cores which need mitigation. 2334de190555SJeremy Linton 0: force disabled 2335de190555SJeremy Linton 1: force enabled 2336de190555SJeremy Linton 2337e52347bdSJani Nikula kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. 2338e52347bdSJani Nikula Default is 0 (don't ignore, but inject #GP) 2339e52347bdSJani Nikula 2340c4ae60e4SLiran Alon kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface. 2341c4ae60e4SLiran Alon Default is false (don't support). 2342c4ae60e4SLiran Alon 2343e52347bdSJani Nikula kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit 2344e52347bdSJani Nikula KVM MMU at runtime. 2345e52347bdSJani Nikula Default is 0 (off) 2346e52347bdSJani Nikula 2347b8e8c830SPaolo Bonzini kvm.nx_huge_pages= 2348b8e8c830SPaolo Bonzini [KVM] Controls the software workaround for the 2349b8e8c830SPaolo Bonzini X86_BUG_ITLB_MULTIHIT bug. 2350b8e8c830SPaolo Bonzini force : Always deploy workaround. 2351b8e8c830SPaolo Bonzini off : Never deploy workaround. 2352b8e8c830SPaolo Bonzini auto : Deploy workaround based on the presence of 2353b8e8c830SPaolo Bonzini X86_BUG_ITLB_MULTIHIT. 2354b8e8c830SPaolo Bonzini 2355b8e8c830SPaolo Bonzini Default is 'auto'. 2356b8e8c830SPaolo Bonzini 2357b8e8c830SPaolo Bonzini If the software workaround is enabled for the host, 2358b8e8c830SPaolo Bonzini guests do need not to enable it for nested guests. 2359b8e8c830SPaolo Bonzini 23601aa9b957SJunaid Shahid kvm.nx_huge_pages_recovery_ratio= 23611aa9b957SJunaid Shahid [KVM] Controls how many 4KiB pages are periodically zapped 23621aa9b957SJunaid Shahid back to huge pages. 0 disables the recovery, otherwise if 23631aa9b957SJunaid Shahid the value is N KVM will zap 1/Nth of the 4KiB pages every 23644dfe4f40SJunaid Shahid period (see below). The default is 60. 23654dfe4f40SJunaid Shahid 23664dfe4f40SJunaid Shahid kvm.nx_huge_pages_recovery_period_ms= 23674dfe4f40SJunaid Shahid [KVM] Controls the time period at which KVM zaps 4KiB pages 23684dfe4f40SJunaid Shahid back to huge pages. If the value is a non-zero N, KVM will 23694dfe4f40SJunaid Shahid zap a portion (see ratio above) of the pages every N msecs. 23704dfe4f40SJunaid Shahid If the value is 0 (the default), KVM will pick a period based 23714dfe4f40SJunaid Shahid on the ratio, such that a page is zapped after 1 hour on average. 23721aa9b957SJunaid Shahid 2373e52347bdSJani Nikula kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. 2374e52347bdSJani Nikula Default is 1 (enabled) 2375e52347bdSJani Nikula 2376e52347bdSJani Nikula kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) 2377e52347bdSJani Nikula for all guests. 2378e52347bdSJani Nikula Default is 1 (enabled) if in 64-bit or 32-bit PAE mode. 2379e52347bdSJani Nikula 2380d8b369c4SDavid Brazdil kvm-arm.mode= 2381d8b369c4SDavid Brazdil [KVM,ARM] Select one of KVM/arm64's modes of operation. 2382d8b369c4SDavid Brazdil 2383b6a68b97SMarc Zyngier none: Forcefully disable KVM. 2384b6a68b97SMarc Zyngier 23851945a067SMarc Zyngier nvhe: Standard nVHE-based mode, without support for 23861945a067SMarc Zyngier protected guests. 23871945a067SMarc Zyngier 2388d8b369c4SDavid Brazdil protected: nVHE-based mode with support for guests whose 2389d8b369c4SDavid Brazdil state is kept private from the host. 2390d8b369c4SDavid Brazdil Not valid if the kernel is running in EL2. 2391d8b369c4SDavid Brazdil 239253e8ce13SAlexandru Elisei Defaults to VHE/nVHE based on hardware support. Setting 239353e8ce13SAlexandru Elisei mode to "protected" will disable kexec and hibernation 239453e8ce13SAlexandru Elisei for the host. 2395d8b369c4SDavid Brazdil 2396e23f62f7SMarc Zyngier kvm-arm.vgic_v3_group0_trap= 2397e23f62f7SMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 group-0 2398e23f62f7SMarc Zyngier system registers 2399e23f62f7SMarc Zyngier 2400182936eeSMarc Zyngier kvm-arm.vgic_v3_group1_trap= 2401182936eeSMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 group-1 2402182936eeSMarc Zyngier system registers 2403182936eeSMarc Zyngier 2404ff89511eSMarc Zyngier kvm-arm.vgic_v3_common_trap= 2405ff89511eSMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 common 2406ff89511eSMarc Zyngier system registers 2407ff89511eSMarc Zyngier 2408a7546054SMarc Zyngier kvm-arm.vgic_v4_enable= 2409a7546054SMarc Zyngier [KVM,ARM] Allow use of GICv4 for direct injection of 2410a7546054SMarc Zyngier LPIs. 2411a7546054SMarc Zyngier 2412aed26eebSSatheesh Rajendran kvm_cma_resv_ratio=n [PPC] 2413aed26eebSSatheesh Rajendran Reserves given percentage from system memory area for 2414aed26eebSSatheesh Rajendran contiguous memory allocation for KVM hash pagetable 2415aed26eebSSatheesh Rajendran allocation. 2416aed26eebSSatheesh Rajendran By default it reserves 5% of total system memory. 2417aed26eebSSatheesh Rajendran Format: <integer> 2418aed26eebSSatheesh Rajendran Default: 5 2419aed26eebSSatheesh Rajendran 2420e52347bdSJani Nikula kvm-intel.ept= [KVM,Intel] Disable extended page tables 2421e52347bdSJani Nikula (virtualized MMU) support on capable Intel chips. 2422e52347bdSJani Nikula Default is 1 (enabled) 2423e52347bdSJani Nikula 2424e52347bdSJani Nikula kvm-intel.emulate_invalid_guest_state= 2425e52347bdSJani Nikula [KVM,Intel] Enable emulation of invalid guest states 2426e52347bdSJani Nikula Default is 0 (disabled) 2427e52347bdSJani Nikula 2428e52347bdSJani Nikula kvm-intel.flexpriority= 2429e52347bdSJani Nikula [KVM,Intel] Disable FlexPriority feature (TPR shadow). 2430e52347bdSJani Nikula Default is 1 (enabled) 2431e52347bdSJani Nikula 2432e52347bdSJani Nikula kvm-intel.nested= 2433e52347bdSJani Nikula [KVM,Intel] Enable VMX nesting (nVMX). 2434e52347bdSJani Nikula Default is 0 (disabled) 2435e52347bdSJani Nikula 2436e52347bdSJani Nikula kvm-intel.unrestricted_guest= 2437e52347bdSJani Nikula [KVM,Intel] Disable unrestricted guest feature 2438e52347bdSJani Nikula (virtualized real and unpaged mode) on capable 2439e52347bdSJani Nikula Intel chips. Default is 1 (enabled) 2440e52347bdSJani Nikula 2441a399477eSKonrad Rzeszutek Wilk kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault 2442a399477eSKonrad Rzeszutek Wilk CVE-2018-3620. 2443a399477eSKonrad Rzeszutek Wilk 2444a399477eSKonrad Rzeszutek Wilk Valid arguments: never, cond, always 2445a399477eSKonrad Rzeszutek Wilk 2446a399477eSKonrad Rzeszutek Wilk always: L1D cache flush on every VMENTER. 2447a399477eSKonrad Rzeszutek Wilk cond: Flush L1D on VMENTER only when the code between 2448a399477eSKonrad Rzeszutek Wilk VMEXIT and VMENTER can leak host memory. 2449a399477eSKonrad Rzeszutek Wilk never: Disables the mitigation 2450a399477eSKonrad Rzeszutek Wilk 2451a399477eSKonrad Rzeszutek Wilk Default is cond (do L1 cache flush in specific instances) 2452a399477eSKonrad Rzeszutek Wilk 2453e52347bdSJani Nikula kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification 2454e52347bdSJani Nikula feature (tagged TLBs) on capable Intel chips. 2455e52347bdSJani Nikula Default is 1 (enabled) 2456e52347bdSJani Nikula 2457b7fe54f6SBalbir Singh l1d_flush= [X86,INTEL] 2458b7fe54f6SBalbir Singh Control mitigation for L1D based snooping vulnerability. 2459b7fe54f6SBalbir Singh 2460b7fe54f6SBalbir Singh Certain CPUs are vulnerable to an exploit against CPU 2461b7fe54f6SBalbir Singh internal buffers which can forward information to a 2462b7fe54f6SBalbir Singh disclosure gadget under certain conditions. 2463b7fe54f6SBalbir Singh 2464b7fe54f6SBalbir Singh In vulnerable processors, the speculatively 2465b7fe54f6SBalbir Singh forwarded data can be used in a cache side channel 2466b7fe54f6SBalbir Singh attack, to access data to which the attacker does 2467b7fe54f6SBalbir Singh not have direct access. 2468b7fe54f6SBalbir Singh 2469b7fe54f6SBalbir Singh This parameter controls the mitigation. The 2470b7fe54f6SBalbir Singh options are: 2471b7fe54f6SBalbir Singh 2472b7fe54f6SBalbir Singh on - enable the interface for the mitigation 2473b7fe54f6SBalbir Singh 2474d90a7a0eSJiri Kosina l1tf= [X86] Control mitigation of the L1TF vulnerability on 2475d90a7a0eSJiri Kosina affected CPUs 2476d90a7a0eSJiri Kosina 2477d90a7a0eSJiri Kosina The kernel PTE inversion protection is unconditionally 2478d90a7a0eSJiri Kosina enabled and cannot be disabled. 2479d90a7a0eSJiri Kosina 2480d90a7a0eSJiri Kosina full 2481d90a7a0eSJiri Kosina Provides all available mitigations for the 2482d90a7a0eSJiri Kosina L1TF vulnerability. Disables SMT and 2483d90a7a0eSJiri Kosina enables all mitigations in the 2484d90a7a0eSJiri Kosina hypervisors, i.e. unconditional L1D flush. 2485d90a7a0eSJiri Kosina 2486d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2487d90a7a0eSJiri Kosina sysfs interface is still possible after 2488d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2489d90a7a0eSJiri Kosina when the first VM is started in a 2490d90a7a0eSJiri Kosina potentially insecure configuration, 2491d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2492d90a7a0eSJiri Kosina 2493d90a7a0eSJiri Kosina full,force 2494d90a7a0eSJiri Kosina Same as 'full', but disables SMT and L1D 2495d90a7a0eSJiri Kosina flush runtime control. Implies the 2496d90a7a0eSJiri Kosina 'nosmt=force' command line option. 2497d90a7a0eSJiri Kosina (i.e. sysfs control of SMT is disabled.) 2498d90a7a0eSJiri Kosina 2499d90a7a0eSJiri Kosina flush 2500d90a7a0eSJiri Kosina Leaves SMT enabled and enables the default 2501d90a7a0eSJiri Kosina hypervisor mitigation, i.e. conditional 2502d90a7a0eSJiri Kosina L1D flush. 2503d90a7a0eSJiri Kosina 2504d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2505d90a7a0eSJiri Kosina sysfs interface is still possible after 2506d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2507d90a7a0eSJiri Kosina when the first VM is started in a 2508d90a7a0eSJiri Kosina potentially insecure configuration, 2509d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2510d90a7a0eSJiri Kosina 2511d90a7a0eSJiri Kosina flush,nosmt 2512d90a7a0eSJiri Kosina 2513d90a7a0eSJiri Kosina Disables SMT and enables the default 2514d90a7a0eSJiri Kosina hypervisor mitigation. 2515d90a7a0eSJiri Kosina 2516d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2517d90a7a0eSJiri Kosina sysfs interface is still possible after 2518d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2519d90a7a0eSJiri Kosina when the first VM is started in a 2520d90a7a0eSJiri Kosina potentially insecure configuration, 2521d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2522d90a7a0eSJiri Kosina 2523d90a7a0eSJiri Kosina flush,nowarn 2524d90a7a0eSJiri Kosina Same as 'flush', but hypervisors will not 2525d90a7a0eSJiri Kosina warn when a VM is started in a potentially 2526d90a7a0eSJiri Kosina insecure configuration. 2527d90a7a0eSJiri Kosina 2528d90a7a0eSJiri Kosina off 2529d90a7a0eSJiri Kosina Disables hypervisor mitigations and doesn't 2530d90a7a0eSJiri Kosina emit any warnings. 25315b5e4d62SMichal Hocko It also drops the swap size and available 25325b5e4d62SMichal Hocko RAM limit restriction on both hypervisor and 25335b5e4d62SMichal Hocko bare metal. 2534d90a7a0eSJiri Kosina 2535d90a7a0eSJiri Kosina Default is 'flush'. 2536d90a7a0eSJiri Kosina 253765fd4cb6SThomas Gleixner For details see: Documentation/admin-guide/hw-vuln/l1tf.rst 2538d90a7a0eSJiri Kosina 2539e52347bdSJani Nikula l2cr= [PPC] 2540e52347bdSJani Nikula 2541e52347bdSJani Nikula l3cr= [PPC] 2542e52347bdSJani Nikula 2543e52347bdSJani Nikula lapic [X86-32,APIC] Enable the local APIC even if BIOS 2544e52347bdSJani Nikula disabled it. 2545e52347bdSJani Nikula 2546622381e6SRandy Dunlap lapic= [X86,APIC] Do not use TSC deadline 2547e52347bdSJani Nikula value for LAPIC timer one-shot implementation. Default 2548e52347bdSJani Nikula back to the programmable timer unit in the LAPIC. 2549622381e6SRandy Dunlap Format: notscdeadline 2550e52347bdSJani Nikula 2551e52347bdSJani Nikula lapic_timer_c2_ok [X86,APIC] trust the local apic timer 2552e52347bdSJani Nikula in C2 power state. 2553e52347bdSJani Nikula 2554e52347bdSJani Nikula libata.dma= [LIBATA] DMA control 2555e52347bdSJani Nikula libata.dma=0 Disable all PATA and SATA DMA 2556e52347bdSJani Nikula libata.dma=1 PATA and SATA Disk DMA only 2557e52347bdSJani Nikula libata.dma=2 ATAPI (CDROM) DMA only 2558e52347bdSJani Nikula libata.dma=4 Compact Flash DMA only 2559e52347bdSJani Nikula Combinations also work, so libata.dma=3 enables DMA 2560e52347bdSJani Nikula for disks and CDROMs, but not CFs. 2561e52347bdSJani Nikula 2562e52347bdSJani Nikula libata.ignore_hpa= [LIBATA] Ignore HPA limit 2563e52347bdSJani Nikula libata.ignore_hpa=0 keep BIOS limits (default) 2564e52347bdSJani Nikula libata.ignore_hpa=1 ignore limits, using full disk 2565e52347bdSJani Nikula 2566e52347bdSJani Nikula libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 2567e52347bdSJani Nikula when set. 2568e52347bdSJani Nikula Format: <int> 2569e52347bdSJani Nikula 257025942e5eSRandy Dunlap libata.force= [LIBATA] Force configurations. The format is comma- 2571e52347bdSJani Nikula separated list of "[ID:]VAL" where ID is 2572e52347bdSJani Nikula PORT[.DEVICE]. PORT and DEVICE are decimal numbers 2573e52347bdSJani Nikula matching port, link or device. Basically, it matches 2574e52347bdSJani Nikula the ATA ID string printed on console by libata. If 2575e52347bdSJani Nikula the whole ID part is omitted, the last PORT and DEVICE 2576e52347bdSJani Nikula values are used. If ID hasn't been specified yet, the 2577e52347bdSJani Nikula configuration applies to all ports, links and devices. 2578e52347bdSJani Nikula 2579e52347bdSJani Nikula If only DEVICE is omitted, the parameter applies to 2580e52347bdSJani Nikula the port and all links and devices behind it. DEVICE 2581e52347bdSJani Nikula number of 0 either selects the first device or the 2582e52347bdSJani Nikula first fan-out link behind PMP device. It does not 2583e52347bdSJani Nikula select the host link. DEVICE number of 15 selects the 2584e52347bdSJani Nikula host link and device attached to it. 2585e52347bdSJani Nikula 2586e52347bdSJani Nikula The VAL specifies the configuration to force. As long 2587e52347bdSJani Nikula as there's no ambiguity shortcut notation is allowed. 2588e52347bdSJani Nikula For example, both 1.5 and 1.5G would work for 1.5Gbps. 2589e52347bdSJani Nikula The following configurations can be forced. 2590e52347bdSJani Nikula 2591e52347bdSJani Nikula * Cable type: 40c, 80c, short40c, unk, ign or sata. 2592e52347bdSJani Nikula Any ID with matching PORT is used. 2593e52347bdSJani Nikula 2594e52347bdSJani Nikula * SATA link speed limit: 1.5Gbps or 3.0Gbps. 2595e52347bdSJani Nikula 2596e52347bdSJani Nikula * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 2597e52347bdSJani Nikula udma[/][16,25,33,44,66,100,133] notation is also 2598e52347bdSJani Nikula allowed. 2599e52347bdSJani Nikula 2600e52347bdSJani Nikula * [no]ncq: Turn on or off NCQ. 2601e52347bdSJani Nikula 2602e52347bdSJani Nikula * [no]ncqtrim: Turn off queued DSM TRIM. 2603e52347bdSJani Nikula 2604e52347bdSJani Nikula * nohrst, nosrst, norst: suppress hard, soft 2605e52347bdSJani Nikula and both resets. 2606e52347bdSJani Nikula 2607e52347bdSJani Nikula * rstonce: only attempt one reset during 2608e52347bdSJani Nikula hot-unplug link recovery 2609e52347bdSJani Nikula 2610e52347bdSJani Nikula * dump_id: dump IDENTIFY data. 2611e52347bdSJani Nikula 2612e52347bdSJani Nikula * atapi_dmadir: Enable ATAPI DMADIR bridge support 2613e52347bdSJani Nikula 2614e52347bdSJani Nikula * disable: Disable this device. 2615e52347bdSJani Nikula 2616e52347bdSJani Nikula If there are multiple matching configurations changing 2617e52347bdSJani Nikula the same attribute, the last one is used. 2618e52347bdSJani Nikula 2619e52347bdSJani Nikula memblock=debug [KNL] Enable memblock debug messages. 2620e52347bdSJani Nikula 26216b99e6e6SRandy Dunlap load_ramdisk= [RAM] [Deprecated] 2622e52347bdSJani Nikula 2623e52347bdSJani Nikula lockd.nlm_grace_period=P [NFS] Assign grace period. 2624e52347bdSJani Nikula Format: <integer> 2625e52347bdSJani Nikula 2626e52347bdSJani Nikula lockd.nlm_tcpport=N [NFS] Assign TCP port. 2627e52347bdSJani Nikula Format: <integer> 2628e52347bdSJani Nikula 2629e52347bdSJani Nikula lockd.nlm_timeout=T [NFS] Assign timeout value. 2630e52347bdSJani Nikula Format: <integer> 2631e52347bdSJani Nikula 2632e52347bdSJani Nikula lockd.nlm_udpport=M [NFS] Assign UDP port. 2633e52347bdSJani Nikula Format: <integer> 2634e52347bdSJani Nikula 2635000d388eSMatthew Garrett lockdown= [SECURITY] 2636000d388eSMatthew Garrett { integrity | confidentiality } 2637000d388eSMatthew Garrett Enable the kernel lockdown feature. If set to 2638000d388eSMatthew Garrett integrity, kernel features that allow userland to 2639000d388eSMatthew Garrett modify the running kernel are disabled. If set to 2640000d388eSMatthew Garrett confidentiality, kernel features that allow userland 2641000d388eSMatthew Garrett to extract confidential information from the kernel 2642000d388eSMatthew Garrett are also disabled. 2643000d388eSMatthew Garrett 2644e52347bdSJani Nikula locktorture.nreaders_stress= [KNL] 2645e52347bdSJani Nikula Set the number of locking read-acquisition kthreads. 2646e52347bdSJani Nikula Defaults to being automatically set based on the 2647e52347bdSJani Nikula number of online CPUs. 2648e52347bdSJani Nikula 2649e52347bdSJani Nikula locktorture.nwriters_stress= [KNL] 2650e52347bdSJani Nikula Set the number of locking write-acquisition kthreads. 2651e52347bdSJani Nikula 2652e52347bdSJani Nikula locktorture.onoff_holdoff= [KNL] 2653e52347bdSJani Nikula Set time (s) after boot for CPU-hotplug testing. 2654e52347bdSJani Nikula 2655e52347bdSJani Nikula locktorture.onoff_interval= [KNL] 2656e52347bdSJani Nikula Set time (s) between CPU-hotplug operations, or 2657e52347bdSJani Nikula zero to disable CPU-hotplug testing. 2658e52347bdSJani Nikula 2659e52347bdSJani Nikula locktorture.shuffle_interval= [KNL] 2660e52347bdSJani Nikula Set task-shuffle interval (jiffies). Shuffling 2661e52347bdSJani Nikula tasks allows some CPUs to go into dyntick-idle 2662e52347bdSJani Nikula mode during the locktorture test. 2663e52347bdSJani Nikula 2664e52347bdSJani Nikula locktorture.shutdown_secs= [KNL] 2665e52347bdSJani Nikula Set time (s) after boot system shutdown. This 2666e52347bdSJani Nikula is useful for hands-off automated testing. 2667e52347bdSJani Nikula 2668e52347bdSJani Nikula locktorture.stat_interval= [KNL] 2669e52347bdSJani Nikula Time (s) between statistics printk()s. 2670e52347bdSJani Nikula 2671e52347bdSJani Nikula locktorture.stutter= [KNL] 2672e52347bdSJani Nikula Time (s) to stutter testing, for example, 2673e52347bdSJani Nikula specifying five seconds causes the test to run for 2674e52347bdSJani Nikula five seconds, wait for five seconds, and so on. 2675e52347bdSJani Nikula This tests the locking primitive's ability to 2676e52347bdSJani Nikula transition abruptly to and from idle. 2677e52347bdSJani Nikula 2678e52347bdSJani Nikula locktorture.torture_type= [KNL] 2679e52347bdSJani Nikula Specify the locking implementation to test. 2680e52347bdSJani Nikula 2681e52347bdSJani Nikula locktorture.verbose= [KNL] 2682e52347bdSJani Nikula Enable additional printk() statements. 2683e52347bdSJani Nikula 2684e52347bdSJani Nikula logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 2685e52347bdSJani Nikula Format: <irq> 2686e52347bdSJani Nikula 2687e52347bdSJani Nikula loglevel= All Kernel Messages with a loglevel smaller than the 2688e52347bdSJani Nikula console loglevel will be printed to the console. It can 2689e52347bdSJani Nikula also be changed with klogd or other programs. The 2690e52347bdSJani Nikula loglevels are defined as follows: 2691e52347bdSJani Nikula 2692e52347bdSJani Nikula 0 (KERN_EMERG) system is unusable 2693e52347bdSJani Nikula 1 (KERN_ALERT) action must be taken immediately 2694e52347bdSJani Nikula 2 (KERN_CRIT) critical conditions 2695e52347bdSJani Nikula 3 (KERN_ERR) error conditions 2696e52347bdSJani Nikula 4 (KERN_WARNING) warning conditions 2697e52347bdSJani Nikula 5 (KERN_NOTICE) normal but significant condition 2698e52347bdSJani Nikula 6 (KERN_INFO) informational 2699e52347bdSJani Nikula 7 (KERN_DEBUG) debug-level messages 2700e52347bdSJani Nikula 2701e52347bdSJani Nikula log_buf_len=n[KMG] Sets the size of the printk ring buffer, 2702e52347bdSJani Nikula in bytes. n must be a power of two and greater 2703e52347bdSJani Nikula than the minimal size. The minimal size is defined 2704e52347bdSJani Nikula by LOG_BUF_SHIFT kernel config parameter. There is 2705e52347bdSJani Nikula also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter 2706e52347bdSJani Nikula that allows to increase the default size depending on 2707e52347bdSJani Nikula the number of CPUs. See init/Kconfig for more details. 2708e52347bdSJani Nikula 2709e52347bdSJani Nikula logo.nologo [FB] Disables display of the built-in Linux logo. 2710e52347bdSJani Nikula This may be used to provide more screen space for 2711e52347bdSJani Nikula kernel log messages and is useful when debugging 2712e52347bdSJani Nikula kernel boot problems. 2713e52347bdSJani Nikula 2714e52347bdSJani Nikula lp=0 [LP] Specify parallel ports to use, e.g, 2715e52347bdSJani Nikula lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 2716e52347bdSJani Nikula lp=reset first parallel port). 'lp=0' disables the 2717e52347bdSJani Nikula lp=auto printer driver. 'lp=reset' (which can be 2718e52347bdSJani Nikula specified in addition to the ports) causes 2719e52347bdSJani Nikula attached printers to be reset. Using 2720e52347bdSJani Nikula lp=port1,port2,... specifies the parallel ports 2721e52347bdSJani Nikula to associate lp devices with, starting with 2722e52347bdSJani Nikula lp0. A port specification may be 'none' to skip 2723e52347bdSJani Nikula that lp device, or a parport name such as 2724e52347bdSJani Nikula 'parport0'. Specifying 'lp=auto' instead of a 2725e52347bdSJani Nikula port specification list means that device IDs 2726e52347bdSJani Nikula from each port should be examined, to see if 2727e52347bdSJani Nikula an IEEE 1284-compliant printer is attached; if 2728e52347bdSJani Nikula so, the driver will manage that printer. 2729e52347bdSJani Nikula See also header of drivers/char/lp.c. 2730e52347bdSJani Nikula 2731e52347bdSJani Nikula lpj=n [KNL] 2732e52347bdSJani Nikula Sets loops_per_jiffy to given constant, thus avoiding 2733e52347bdSJani Nikula time-consuming boot-time autodetection (up to 250 ms per 2734e52347bdSJani Nikula CPU). 0 enables autodetection (default). To determine 2735e52347bdSJani Nikula the correct value for your kernel, boot with normal 2736e52347bdSJani Nikula autodetection and see what value is printed. Note that 2737e52347bdSJani Nikula on SMP systems the preset will be applied to all CPUs, 2738e52347bdSJani Nikula which is likely to cause problems if your CPUs need 2739e52347bdSJani Nikula significantly divergent settings. An incorrect value 2740e52347bdSJani Nikula will cause delays in the kernel to be wrong, leading to 2741e52347bdSJani Nikula unpredictable I/O errors and other breakage. Although 2742e52347bdSJani Nikula unlikely, in the extreme case this might damage your 2743e52347bdSJani Nikula hardware. 2744e52347bdSJani Nikula 2745e52347bdSJani Nikula ltpc= [NET] 2746e52347bdSJani Nikula Format: <io>,<irq>,<dma> 2747e52347bdSJani Nikula 27489b8c7c14SKees Cook lsm.debug [SECURITY] Enable LSM initialization debugging output. 27499b8c7c14SKees Cook 275079f7865dSKees Cook lsm=lsm1,...,lsmN 275179f7865dSKees Cook [SECURITY] Choose order of LSM initialization. This 275289a9684eSKees Cook overrides CONFIG_LSM, and the "security=" parameter. 275379f7865dSKees Cook 2754e52347bdSJani Nikula machvec= [IA-64] Force the use of a particular machine-vector 2755e52347bdSJani Nikula (machvec) in a generic kernel. 2756df43acacSChristoph Hellwig Example: machvec=hpzx1 2757e52347bdSJani Nikula 275842769488SRandy Dunlap machtype= [Loongson] Share the same kernel image file between 275942769488SRandy Dunlap different yeeloong laptops. 2760e52347bdSJani Nikula Example: machtype=lemote-yeeloong-2f-7inch 2761e52347bdSJani Nikula 2762e52347bdSJani Nikula max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater 2763e52347bdSJani Nikula than or equal to this physical address is ignored. 2764e52347bdSJani Nikula 2765e52347bdSJani Nikula maxcpus= [SMP] Maximum number of processors that an SMP kernel 2766e52347bdSJani Nikula will bring up during bootup. maxcpus=n : n >= 0 limits 2767e52347bdSJani Nikula the kernel to bring up 'n' processors. Surely after 2768e52347bdSJani Nikula bootup you can bring up the other plugged cpu by executing 2769e52347bdSJani Nikula "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus 2770e52347bdSJani Nikula only takes effect during system bootup. 2771e52347bdSJani Nikula While n=0 is a special case, it is equivalent to "nosmp", 2772e52347bdSJani Nikula which also disables the IO APIC. 2773e52347bdSJani Nikula 2774e52347bdSJani Nikula max_loop= [LOOP] The number of loop block devices that get 2775e52347bdSJani Nikula (loop.max_loop) unconditionally pre-created at init time. The default 2776e52347bdSJani Nikula number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead 2777e52347bdSJani Nikula of statically allocating a predefined number, loop 2778e52347bdSJani Nikula devices can be requested on-demand with the 2779e52347bdSJani Nikula /dev/loop-control interface. 2780e52347bdSJani Nikula 2781e52347bdSJani Nikula mce [X86-32] Machine Check Exception 2782e52347bdSJani Nikula 2783cb1aaebeSMauro Carvalho Chehab mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst 2784e52347bdSJani Nikula 2785e52347bdSJani Nikula md= [HW] RAID subsystems devices and level 2786e52347bdSJani Nikula See Documentation/admin-guide/md.rst. 2787e52347bdSJani Nikula 2788e52347bdSJani Nikula mdacon= [MDA] 2789e52347bdSJani Nikula Format: <first>,<last> 2790e52347bdSJani Nikula Specifies range of consoles to be captured by the MDA. 2791e52347bdSJani Nikula 2792bc124170SThomas Gleixner mds= [X86,INTEL] 2793bc124170SThomas Gleixner Control mitigation for the Micro-architectural Data 2794bc124170SThomas Gleixner Sampling (MDS) vulnerability. 2795bc124170SThomas Gleixner 2796bc124170SThomas Gleixner Certain CPUs are vulnerable to an exploit against CPU 2797bc124170SThomas Gleixner internal buffers which can forward information to a 2798bc124170SThomas Gleixner disclosure gadget under certain conditions. 2799bc124170SThomas Gleixner 2800bc124170SThomas Gleixner In vulnerable processors, the speculatively 2801bc124170SThomas Gleixner forwarded data can be used in a cache side channel 2802bc124170SThomas Gleixner attack, to access data to which the attacker does 2803bc124170SThomas Gleixner not have direct access. 2804bc124170SThomas Gleixner 2805bc124170SThomas Gleixner This parameter controls the MDS mitigation. The 2806bc124170SThomas Gleixner options are: 2807bc124170SThomas Gleixner 2808bc124170SThomas Gleixner full - Enable MDS mitigation on vulnerable CPUs 2809d71eb0ceSJosh Poimboeuf full,nosmt - Enable MDS mitigation and disable 2810d71eb0ceSJosh Poimboeuf SMT on vulnerable CPUs 2811bc124170SThomas Gleixner off - Unconditionally disable MDS mitigation 2812bc124170SThomas Gleixner 281364870ed1SWaiman Long On TAA-affected machines, mds=off can be prevented by 281464870ed1SWaiman Long an active TAA mitigation as both vulnerabilities are 281564870ed1SWaiman Long mitigated with the same mechanism so in order to disable 281664870ed1SWaiman Long this mitigation, you need to specify tsx_async_abort=off 281764870ed1SWaiman Long too. 281864870ed1SWaiman Long 2819bc124170SThomas Gleixner Not specifying this option is equivalent to 2820bc124170SThomas Gleixner mds=full. 2821bc124170SThomas Gleixner 28225999bbe7SThomas Gleixner For details see: Documentation/admin-guide/hw-vuln/mds.rst 28235999bbe7SThomas Gleixner 2824e52347bdSJani Nikula mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 2825f3cd4c86SBaoquan He Amount of memory to be used in cases as follows: 2826f3cd4c86SBaoquan He 2827f3cd4c86SBaoquan He 1 for test; 2828f3cd4c86SBaoquan He 2 when the kernel is not able to see the whole system memory; 2829f3cd4c86SBaoquan He 3 memory that lies after 'mem=' boundary is excluded from 2830f3cd4c86SBaoquan He the hypervisor, then assigned to KVM guests. 2831f3cd4c86SBaoquan He 2832e52347bdSJani Nikula [X86] Work as limiting max address. Use together 2833e52347bdSJani Nikula with memmap= to avoid physical address space collisions. 2834e52347bdSJani Nikula Without memmap= PCI devices could be placed at addresses 2835e52347bdSJani Nikula belonging to unused RAM. 2836e52347bdSJani Nikula 2837f3cd4c86SBaoquan He Note that this only takes effects during boot time since 2838f3cd4c86SBaoquan He in above case 3, memory may need be hot added after boot 2839f3cd4c86SBaoquan He if system memory of hypervisor is not sufficient. 2840f3cd4c86SBaoquan He 2841e52347bdSJani Nikula mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 2842e52347bdSJani Nikula memory. 2843e52347bdSJani Nikula 2844e52347bdSJani Nikula memchunk=nn[KMG] 2845e52347bdSJani Nikula [KNL,SH] Allow user to override the default size for 2846e52347bdSJani Nikula per-device physically contiguous DMA buffers. 2847e52347bdSJani Nikula 2848e52347bdSJani Nikula memhp_default_state=online/offline 2849e52347bdSJani Nikula [KNL] Set the initial state for the memory hotplug 2850e52347bdSJani Nikula onlining policy. If not specified, the default value is 2851e52347bdSJani Nikula set according to the 2852e52347bdSJani Nikula CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config 2853e52347bdSJani Nikula option. 2854cb1aaebeSMauro Carvalho Chehab See Documentation/admin-guide/mm/memory-hotplug.rst. 2855e52347bdSJani Nikula 2856e52347bdSJani Nikula memmap=exactmap [KNL,X86] Enable setting of an exact 2857e52347bdSJani Nikula E820 memory map, as specified by the user. 2858e52347bdSJani Nikula Such memmap=exactmap lines can be constructed based on 2859e52347bdSJani Nikula BIOS output or other requirements. See the memmap=nn@ss 2860e52347bdSJani Nikula option description. 2861e52347bdSJani Nikula 2862e52347bdSJani Nikula memmap=nn[KMG]@ss[KMG] 28634c8e3de4SBarry Song [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory. 2864e52347bdSJani Nikula Region of memory to be used is from ss to ss+nn. 28658fcc9bc3SBaoquan He If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG], 28668fcc9bc3SBaoquan He which limits max address to nn[KMG]. 28678fcc9bc3SBaoquan He Multiple different regions can be specified, 28688fcc9bc3SBaoquan He comma delimited. 28698fcc9bc3SBaoquan He Example: 28708fcc9bc3SBaoquan He memmap=100M@2G,100M#3G,1G!1024G 2871e52347bdSJani Nikula 2872e52347bdSJani Nikula memmap=nn[KMG]#ss[KMG] 2873e52347bdSJani Nikula [KNL,ACPI] Mark specific memory as ACPI data. 2874e52347bdSJani Nikula Region of memory to be marked is from ss to ss+nn. 2875e52347bdSJani Nikula 2876e52347bdSJani Nikula memmap=nn[KMG]$ss[KMG] 2877e52347bdSJani Nikula [KNL,ACPI] Mark specific memory as reserved. 2878e52347bdSJani Nikula Region of memory to be reserved is from ss to ss+nn. 2879e52347bdSJani Nikula Example: Exclude memory from 0x18690000-0x1869ffff 2880e52347bdSJani Nikula memmap=64K$0x18690000 2881e52347bdSJani Nikula or 2882e52347bdSJani Nikula memmap=0x10000$0x18690000 28838fcc9bc3SBaoquan He Some bootloaders may need an escape character before '$', 28848fcc9bc3SBaoquan He like Grub2, otherwise '$' and the following number 28858fcc9bc3SBaoquan He will be eaten. 2886e52347bdSJani Nikula 2887e52347bdSJani Nikula memmap=nn[KMG]!ss[KMG] 2888e52347bdSJani Nikula [KNL,X86] Mark specific memory as protected. 2889e52347bdSJani Nikula Region of memory to be used, from ss to ss+nn. 2890e52347bdSJani Nikula The memory region may be marked as e820 type 12 (0xc) 2891e52347bdSJani Nikula and is NVDIMM or ADR memory. 2892e52347bdSJani Nikula 2893ef61f8a3SJan H. Schönherr memmap=<size>%<offset>-<oldtype>+<newtype> 2894ef61f8a3SJan H. Schönherr [KNL,ACPI] Convert memory within the specified region 2895ef61f8a3SJan H. Schönherr from <oldtype> to <newtype>. If "-<oldtype>" is left 2896ef61f8a3SJan H. Schönherr out, the whole region will be marked as <newtype>, 2897ef61f8a3SJan H. Schönherr even if previously unavailable. If "+<newtype>" is left 2898ef61f8a3SJan H. Schönherr out, matching memory will be removed. Types are 2899ef61f8a3SJan H. Schönherr specified as e820 types, e.g., 1 = RAM, 2 = reserved, 2900ef61f8a3SJan H. Schönherr 3 = ACPI, 12 = PRAM. 2901ef61f8a3SJan H. Schönherr 2902e52347bdSJani Nikula memory_corruption_check=0/1 [X86] 2903e52347bdSJani Nikula Some BIOSes seem to corrupt the first 64k of 2904e52347bdSJani Nikula memory when doing things like suspend/resume. 2905e52347bdSJani Nikula Setting this option will scan the memory 2906e52347bdSJani Nikula looking for corruption. Enabling this will 2907e52347bdSJani Nikula both detect corruption and prevent the kernel 2908e52347bdSJani Nikula from using the memory being corrupted. 2909e52347bdSJani Nikula However, its intended as a diagnostic tool; if 2910e52347bdSJani Nikula repeatable BIOS-originated corruption always 2911e52347bdSJani Nikula affects the same memory, you can use memmap= 2912e52347bdSJani Nikula to prevent the kernel from using that memory. 2913e52347bdSJani Nikula 2914e52347bdSJani Nikula memory_corruption_check_size=size [X86] 2915e52347bdSJani Nikula By default it checks for corruption in the low 2916e52347bdSJani Nikula 64k, making this memory unavailable for normal 2917e52347bdSJani Nikula use. Use this parameter to scan for 2918e52347bdSJani Nikula corruption in more or less memory. 2919e52347bdSJani Nikula 2920e52347bdSJani Nikula memory_corruption_check_period=seconds [X86] 2921e52347bdSJani Nikula By default it checks for corruption every 60 2922e52347bdSJani Nikula seconds. Use this parameter to check at some 2923e52347bdSJani Nikula other rate. 0 disables periodic checking. 2924e52347bdSJani Nikula 2925e3a9d9fcSOscar Salvador memory_hotplug.memmap_on_memory 2926e3a9d9fcSOscar Salvador [KNL,X86,ARM] Boolean flag to enable this feature. 2927e3a9d9fcSOscar Salvador Format: {on | off (default)} 2928e3a9d9fcSOscar Salvador When enabled, runtime hotplugged memory will 2929e3a9d9fcSOscar Salvador allocate its internal metadata (struct pages) 2930e3a9d9fcSOscar Salvador from the hotadded memory which will allow to 2931e3a9d9fcSOscar Salvador hotadd a lot of memory without requiring 2932e3a9d9fcSOscar Salvador additional memory to do so. 2933e3a9d9fcSOscar Salvador This feature is disabled by default because it 2934e3a9d9fcSOscar Salvador has some implication on large (e.g. GB) 2935e3a9d9fcSOscar Salvador allocations in some configurations (e.g. small 2936e3a9d9fcSOscar Salvador memory blocks). 2937e3a9d9fcSOscar Salvador The state of the flag can be read in 2938e3a9d9fcSOscar Salvador /sys/module/memory_hotplug/parameters/memmap_on_memory. 2939e3a9d9fcSOscar Salvador Note that even when enabled, there are a few cases where 2940e3a9d9fcSOscar Salvador the feature is not effective. 2941e3a9d9fcSOscar Salvador 29424bab4964SMuchun Song This is not compatible with hugetlb_free_vmemmap. If 29434bab4964SMuchun Song both parameters are enabled, hugetlb_free_vmemmap takes 29444bab4964SMuchun Song precedence over memory_hotplug.memmap_on_memory. 29454bab4964SMuchun Song 2946f6e5aedfSKefeng Wang memtest= [KNL,X86,ARM,PPC,RISCV] Enable memtest 2947e52347bdSJani Nikula Format: <integer> 2948e52347bdSJani Nikula default : 0 <disable> 2949e52347bdSJani Nikula Specifies the number of memtest passes to be 2950e52347bdSJani Nikula performed. Each pass selects another test 2951e52347bdSJani Nikula pattern from a given set of patterns. Memtest 2952e52347bdSJani Nikula fills the memory with this pattern, validates 2953e52347bdSJani Nikula memory contents and reserves bad memory 2954e52347bdSJani Nikula regions that are detected. 2955e52347bdSJani Nikula 2956c262f3b9STom Lendacky mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control 2957c262f3b9STom Lendacky Valid arguments: on, off 2958c262f3b9STom Lendacky Default (depends on kernel configuration option): 2959c262f3b9STom Lendacky on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y) 2960c262f3b9STom Lendacky off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n) 2961c262f3b9STom Lendacky mem_encrypt=on: Activate SME 2962c262f3b9STom Lendacky mem_encrypt=off: Do not activate SME 2963c262f3b9STom Lendacky 29642f5947dfSChristoph Hellwig Refer to Documentation/virt/kvm/amd-memory-encryption.rst 2965c262f3b9STom Lendacky for details on when memory encryption can be activated. 2966c262f3b9STom Lendacky 29677b9dc3f7SLinus Torvalds mem_sleep_default= [SUSPEND] Default system suspend mode: 29687b9dc3f7SLinus Torvalds s2idle - Suspend-To-Idle 29697b9dc3f7SLinus Torvalds shallow - Power-On Suspend or equivalent (if supported) 29707b9dc3f7SLinus Torvalds deep - Suspend-To-RAM or equivalent (if supported) 297158e7cb9eSRafael J. Wysocki See Documentation/admin-guide/pm/sleep-states.rst. 29727b9dc3f7SLinus Torvalds 2973e52347bdSJani Nikula meye.*= [HW] Set MotionEye Camera parameters 297432e2eae2SMauro Carvalho Chehab See Documentation/admin-guide/media/meye.rst. 2975e52347bdSJani Nikula 2976e52347bdSJani Nikula mfgpt_irq= [IA-32] Specify the IRQ to use for the 2977e52347bdSJani Nikula Multi-Function General Purpose Timers on AMD Geode 2978e52347bdSJani Nikula platforms. 2979e52347bdSJani Nikula 2980e52347bdSJani Nikula mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 2981e52347bdSJani Nikula the BIOS has incorrectly applied a workaround. TinyBIOS 2982e52347bdSJani Nikula version 0.98 is known to be affected, 0.99 fixes the 2983e52347bdSJani Nikula problem by letting the user disable the workaround. 2984e52347bdSJani Nikula 2985e52347bdSJani Nikula mga= [HW,DRM] 2986e52347bdSJani Nikula 2987e52347bdSJani Nikula min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this 2988e52347bdSJani Nikula physical address is ignored. 2989e52347bdSJani Nikula 2990e52347bdSJani Nikula mini2440= [ARM,HW,KNL] 2991e52347bdSJani Nikula Format:[0..2][b][c][t] 2992e52347bdSJani Nikula Default: "0tb" 2993e52347bdSJani Nikula MINI2440 configuration specification: 2994e52347bdSJani Nikula 0 - The attached screen is the 3.5" TFT 2995e52347bdSJani Nikula 1 - The attached screen is the 7" TFT 2996e52347bdSJani Nikula 2 - The VGA Shield is attached (1024x768) 2997e52347bdSJani Nikula Leaving out the screen size parameter will not load 2998e52347bdSJani Nikula the TFT driver, and the framebuffer will be left 2999e52347bdSJani Nikula unconfigured. 3000e52347bdSJani Nikula b - Enable backlight. The TFT backlight pin will be 3001e52347bdSJani Nikula linked to the kernel VESA blanking code and a GPIO 3002e52347bdSJani Nikula LED. This parameter is not necessary when using the 3003e52347bdSJani Nikula VGA shield. 3004e52347bdSJani Nikula c - Enable the s3c camera interface. 3005e52347bdSJani Nikula t - Reserved for enabling touchscreen support. The 3006e52347bdSJani Nikula touchscreen support is not enabled in the mainstream 3007e52347bdSJani Nikula kernel as of 2.6.30, a preliminary port can be found 3008e52347bdSJani Nikula in the "bleeding edge" mini2440 support kernel at 30096b2484e1SAlexander A. Klimov https://repo.or.cz/w/linux-2.6/mini2440.git 3010e52347bdSJani Nikula 301198af8452SJosh Poimboeuf mitigations= 3012a111b7c0SJosh Poimboeuf [X86,PPC,S390,ARM64] Control optional mitigations for 3013a111b7c0SJosh Poimboeuf CPU vulnerabilities. This is a set of curated, 3014d68be4c4SJosh Poimboeuf arch-independent options, each of which is an 3015d68be4c4SJosh Poimboeuf aggregation of existing arch-specific options. 301698af8452SJosh Poimboeuf 301798af8452SJosh Poimboeuf off 301898af8452SJosh Poimboeuf Disable all optional CPU mitigations. This 301998af8452SJosh Poimboeuf improves system performance, but it may also 302098af8452SJosh Poimboeuf expose users to several CPU vulnerabilities. 3021782e69efSJosh Poimboeuf Equivalent to: nopti [X86,PPC] 3022a111b7c0SJosh Poimboeuf kpti=0 [ARM64] 3023a2059825SJosh Poimboeuf nospectre_v1 [X86,PPC] 30240336e04aSJosh Poimboeuf nobp=0 [S390] 3025a111b7c0SJosh Poimboeuf nospectre_v2 [X86,PPC,S390,ARM64] 3026d68be4c4SJosh Poimboeuf spectre_v2_user=off [X86] 3027782e69efSJosh Poimboeuf spec_store_bypass_disable=off [X86,PPC] 3028a111b7c0SJosh Poimboeuf ssbd=force-off [ARM64] 3029d68be4c4SJosh Poimboeuf l1tf=off [X86] 30305c14068fSJosh Poimboeuf mds=off [X86] 3031a7a248c5SPawan Gupta tsx_async_abort=off [X86] 3032b8e8c830SPaolo Bonzini kvm.nx_huge_pages=off [X86] 3033f7964378SNicholas Piggin no_entry_flush [PPC] 30349a32a7e7SNicholas Piggin no_uaccess_flush [PPC] 3035b8e8c830SPaolo Bonzini 3036b8e8c830SPaolo Bonzini Exceptions: 3037b8e8c830SPaolo Bonzini This does not have any effect on 3038b8e8c830SPaolo Bonzini kvm.nx_huge_pages when 3039b8e8c830SPaolo Bonzini kvm.nx_huge_pages=force. 304098af8452SJosh Poimboeuf 304198af8452SJosh Poimboeuf auto (default) 304298af8452SJosh Poimboeuf Mitigate all CPU vulnerabilities, but leave SMT 304398af8452SJosh Poimboeuf enabled, even if it's vulnerable. This is for 304498af8452SJosh Poimboeuf users who don't want to be surprised by SMT 304598af8452SJosh Poimboeuf getting disabled across kernel upgrades, or who 304698af8452SJosh Poimboeuf have other ways of avoiding SMT-based attacks. 3047d68be4c4SJosh Poimboeuf Equivalent to: (default behavior) 304898af8452SJosh Poimboeuf 304998af8452SJosh Poimboeuf auto,nosmt 305098af8452SJosh Poimboeuf Mitigate all CPU vulnerabilities, disabling SMT 305198af8452SJosh Poimboeuf if needed. This is for users who always want to 305298af8452SJosh Poimboeuf be fully mitigated, even if it means losing SMT. 3053d68be4c4SJosh Poimboeuf Equivalent to: l1tf=flush,nosmt [X86] 30545c14068fSJosh Poimboeuf mds=full,nosmt [X86] 3055a7a248c5SPawan Gupta tsx_async_abort=full,nosmt [X86] 305698af8452SJosh Poimboeuf 3057e52347bdSJani Nikula mminit_loglevel= 3058e52347bdSJani Nikula [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 3059e52347bdSJani Nikula parameter allows control of the logging verbosity for 3060e52347bdSJani Nikula the additional memory initialisation checks. A value 3061e52347bdSJani Nikula of 0 disables mminit logging and a level of 4 will 3062e52347bdSJani Nikula log everything. Information is printed at KERN_DEBUG 3063e52347bdSJani Nikula so loglevel=8 may also need to be specified. 3064e52347bdSJani Nikula 3065e52347bdSJani Nikula module.sig_enforce 3066e52347bdSJani Nikula [KNL] When CONFIG_MODULE_SIG is set, this means that 3067e52347bdSJani Nikula modules without (valid) signatures will fail to load. 3068e52347bdSJani Nikula Note that if CONFIG_MODULE_SIG_FORCE is set, that 3069e52347bdSJani Nikula is always true, so this option does nothing. 3070e52347bdSJani Nikula 3071e52347bdSJani Nikula module_blacklist= [KNL] Do not load a comma-separated list of 3072e52347bdSJani Nikula modules. Useful for debugging problem modules. 3073e52347bdSJani Nikula 3074e52347bdSJani Nikula mousedev.tap_time= 3075e52347bdSJani Nikula [MOUSE] Maximum time between finger touching and 3076e52347bdSJani Nikula leaving touchpad surface for touch to be considered 3077e52347bdSJani Nikula a tap and be reported as a left button click (for 3078e52347bdSJani Nikula touchpads working in absolute mode only). 3079e52347bdSJani Nikula Format: <msecs> 3080e52347bdSJani Nikula mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 3081e52347bdSJani Nikula reporting absolute coordinates, such as tablets 3082e52347bdSJani Nikula mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 3083e52347bdSJani Nikula reporting absolute coordinates, such as tablets 3084e52347bdSJani Nikula 3085a5c6d650SDavid Rientjes movablecore= [KNL,X86,IA-64,PPC] 3086a5c6d650SDavid Rientjes Format: nn[KMGTPE] | nn% 3087a5c6d650SDavid Rientjes This parameter is the complement to kernelcore=, it 3088a5c6d650SDavid Rientjes specifies the amount of memory used for migratable 3089a5c6d650SDavid Rientjes allocations. If both kernelcore and movablecore is 3090a5c6d650SDavid Rientjes specified, then kernelcore will be at *least* the 3091a5c6d650SDavid Rientjes specified value but may be more. If movablecore on its 3092a5c6d650SDavid Rientjes own is specified, the administrator must be careful 3093e52347bdSJani Nikula that the amount of memory usable for all allocations 3094e52347bdSJani Nikula is not too small. 3095e52347bdSJani Nikula 3096f70029bbSMichal Hocko movable_node [KNL] Boot-time switch to make hotplugable memory 3097f70029bbSMichal Hocko NUMA nodes to be movable. This means that the memory 3098f70029bbSMichal Hocko of such nodes will be usable only for movable 3099f70029bbSMichal Hocko allocations which rules out almost all kernel 3100f70029bbSMichal Hocko allocations. Use with caution! 3101e52347bdSJani Nikula 3102e52347bdSJani Nikula MTD_Partition= [MTD] 3103e52347bdSJani Nikula Format: <name>,<region-number>,<size>,<offset> 3104e52347bdSJani Nikula 3105e52347bdSJani Nikula MTD_Region= [MTD] Format: 3106e52347bdSJani Nikula <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 3107e52347bdSJani Nikula 3108e52347bdSJani Nikula mtdparts= [MTD] 3109fb251124SJonathan Neuschäfer See drivers/mtd/parsers/cmdlinepart.c 3110e52347bdSJani Nikula 3111e52347bdSJani Nikula multitce=off [PPC] This parameter disables the use of the pSeries 3112e52347bdSJani Nikula firmware feature for updating multiple TCE entries 3113e52347bdSJani Nikula at a time. 3114e52347bdSJani Nikula 3115e52347bdSJani Nikula onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration 3116e52347bdSJani Nikula 3117e52347bdSJani Nikula Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] 3118e52347bdSJani Nikula 3119e52347bdSJani Nikula boundary - index of last SLC block on Flex-OneNAND. 3120e52347bdSJani Nikula The remaining blocks are configured as MLC blocks. 3121e52347bdSJani Nikula lock - Configure if Flex-OneNAND boundary should be locked. 3122e52347bdSJani Nikula Once locked, the boundary cannot be changed. 3123e52347bdSJani Nikula 1 indicates lock status, 0 indicates unlock status. 3124e52347bdSJani Nikula 3125e52347bdSJani Nikula mtdset= [ARM] 3126e52347bdSJani Nikula ARM/S3C2412 JIVE boot control 3127e52347bdSJani Nikula 31280f12999eSKrzysztof Kozlowski See arch/arm/mach-s3c/mach-jive.c 3129e52347bdSJani Nikula 3130e52347bdSJani Nikula mtouchusb.raw_coordinates= 3131e52347bdSJani Nikula [HW] Make the MicroTouch USB driver use raw coordinates 3132e52347bdSJani Nikula ('y', default) or cooked coordinates ('n') 3133e52347bdSJani Nikula 3134e52347bdSJani Nikula mtrr_chunk_size=nn[KMG] [X86] 3135e52347bdSJani Nikula used for mtrr cleanup. It is largest continuous chunk 3136e52347bdSJani Nikula that could hold holes aka. UC entries. 3137e52347bdSJani Nikula 3138e52347bdSJani Nikula mtrr_gran_size=nn[KMG] [X86] 3139e52347bdSJani Nikula Used for mtrr cleanup. It is granularity of mtrr block. 3140e52347bdSJani Nikula Default is 1. 3141e52347bdSJani Nikula Large value could prevent small alignment from 3142e52347bdSJani Nikula using up MTRRs. 3143e52347bdSJani Nikula 3144e52347bdSJani Nikula mtrr_spare_reg_nr=n [X86] 3145e52347bdSJani Nikula Format: <integer> 3146e52347bdSJani Nikula Range: 0,7 : spare reg number 3147e52347bdSJani Nikula Default : 1 3148e52347bdSJani Nikula Used for mtrr cleanup. It is spare mtrr entries number. 3149e52347bdSJani Nikula Set to 2 or more if your graphical card needs more. 3150e52347bdSJani Nikula 3151e52347bdSJani Nikula n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 3152e52347bdSJani Nikula 3153e52347bdSJani Nikula netdev= [NET] Network devices parameters 3154e52347bdSJani Nikula Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 3155e52347bdSJani Nikula Note that mem_start is often overloaded to mean 3156e52347bdSJani Nikula something different and driver-specific. 3157e52347bdSJani Nikula This usage is only documented in each driver source 3158e52347bdSJani Nikula file if at all. 3159e52347bdSJani Nikula 3160e52347bdSJani Nikula nf_conntrack.acct= 3161e52347bdSJani Nikula [NETFILTER] Enable connection tracking flow accounting 3162e52347bdSJani Nikula 0 to disable accounting 3163e52347bdSJani Nikula 1 to enable accounting 3164e52347bdSJani Nikula Default value is 0. 3165e52347bdSJani Nikula 3166e52347bdSJani Nikula nfsaddrs= [NFS] Deprecated. Use ip= instead. 31673eb30c51SNiklas Söderlund See Documentation/admin-guide/nfs/nfsroot.rst. 3168e52347bdSJani Nikula 3169e52347bdSJani Nikula nfsroot= [NFS] nfs root filesystem for disk-less boxes. 31703eb30c51SNiklas Söderlund See Documentation/admin-guide/nfs/nfsroot.rst. 3171e52347bdSJani Nikula 3172e52347bdSJani Nikula nfsrootdebug [NFS] enable nfsroot debugging messages. 31733eb30c51SNiklas Söderlund See Documentation/admin-guide/nfs/nfsroot.rst. 3174e52347bdSJani Nikula 3175e52347bdSJani Nikula nfs.callback_nr_threads= 3176e52347bdSJani Nikula [NFSv4] set the total number of threads that the 3177e52347bdSJani Nikula NFS client will assign to service NFSv4 callback 3178e52347bdSJani Nikula requests. 3179e52347bdSJani Nikula 3180e52347bdSJani Nikula nfs.callback_tcpport= 3181e52347bdSJani Nikula [NFS] set the TCP port on which the NFSv4 callback 3182e52347bdSJani Nikula channel should listen. 3183e52347bdSJani Nikula 3184e52347bdSJani Nikula nfs.cache_getent= 3185e52347bdSJani Nikula [NFS] sets the pathname to the program which is used 3186e52347bdSJani Nikula to update the NFS client cache entries. 3187e52347bdSJani Nikula 3188e52347bdSJani Nikula nfs.cache_getent_timeout= 3189e52347bdSJani Nikula [NFS] sets the timeout after which an attempt to 3190e52347bdSJani Nikula update a cache entry is deemed to have failed. 3191e52347bdSJani Nikula 3192e52347bdSJani Nikula nfs.idmap_cache_timeout= 3193e52347bdSJani Nikula [NFS] set the maximum lifetime for idmapper cache 3194e52347bdSJani Nikula entries. 3195e52347bdSJani Nikula 3196e52347bdSJani Nikula nfs.enable_ino64= 3197e52347bdSJani Nikula [NFS] enable 64-bit inode numbers. 3198e52347bdSJani Nikula If zero, the NFS client will fake up a 32-bit inode 3199e52347bdSJani Nikula number for the readdir() and stat() syscalls instead 3200e52347bdSJani Nikula of returning the full 64-bit number. 3201e52347bdSJani Nikula The default is to return 64-bit inode numbers. 3202e52347bdSJani Nikula 3203e52347bdSJani Nikula nfs.max_session_cb_slots= 3204e52347bdSJani Nikula [NFSv4.1] Sets the maximum number of session 3205e52347bdSJani Nikula slots the client will assign to the callback 3206e52347bdSJani Nikula channel. This determines the maximum number of 3207e52347bdSJani Nikula callbacks the client will process in parallel for 3208e52347bdSJani Nikula a particular server. 3209e52347bdSJani Nikula 3210e52347bdSJani Nikula nfs.max_session_slots= 3211e52347bdSJani Nikula [NFSv4.1] Sets the maximum number of session slots 3212e52347bdSJani Nikula the client will attempt to negotiate with the server. 3213e52347bdSJani Nikula This limits the number of simultaneous RPC requests 3214e52347bdSJani Nikula that the client can send to the NFSv4.1 server. 3215e52347bdSJani Nikula Note that there is little point in setting this 3216e52347bdSJani Nikula value higher than the max_tcp_slot_table_limit. 3217e52347bdSJani Nikula 3218e52347bdSJani Nikula nfs.nfs4_disable_idmapping= 3219e52347bdSJani Nikula [NFSv4] When set to the default of '1', this option 3220e52347bdSJani Nikula ensures that both the RPC level authentication 3221e52347bdSJani Nikula scheme and the NFS level operations agree to use 3222e52347bdSJani Nikula numeric uids/gids if the mount is using the 3223e52347bdSJani Nikula 'sec=sys' security flavour. In effect it is 3224e52347bdSJani Nikula disabling idmapping, which can make migration from 3225e52347bdSJani Nikula legacy NFSv2/v3 systems to NFSv4 easier. 3226e52347bdSJani Nikula Servers that do not support this mode of operation 3227e52347bdSJani Nikula will be autodetected by the client, and it will fall 3228e52347bdSJani Nikula back to using the idmapper. 3229e52347bdSJani Nikula To turn off this behaviour, set the value to '0'. 3230e52347bdSJani Nikula nfs.nfs4_unique_id= 3231e52347bdSJani Nikula [NFS4] Specify an additional fixed unique ident- 3232e52347bdSJani Nikula ification string that NFSv4 clients can insert into 3233e52347bdSJani Nikula their nfs_client_id4 string. This is typically a 3234e52347bdSJani Nikula UUID that is generated at system install time. 3235e52347bdSJani Nikula 3236e52347bdSJani Nikula nfs.send_implementation_id = 3237e52347bdSJani Nikula [NFSv4.1] Send client implementation identification 3238e52347bdSJani Nikula information in exchange_id requests. 3239e52347bdSJani Nikula If zero, no implementation identification information 3240e52347bdSJani Nikula will be sent. 3241e52347bdSJani Nikula The default is to send the implementation identification 3242e52347bdSJani Nikula information. 3243e52347bdSJani Nikula 3244e52347bdSJani Nikula nfs.recover_lost_locks = 3245e52347bdSJani Nikula [NFSv4] Attempt to recover locks that were lost due 3246e52347bdSJani Nikula to a lease timeout on the server. Please note that 3247e52347bdSJani Nikula doing this risks data corruption, since there are 3248e52347bdSJani Nikula no guarantees that the file will remain unchanged 3249e52347bdSJani Nikula after the locks are lost. 3250e52347bdSJani Nikula If you want to enable the kernel legacy behaviour of 3251e52347bdSJani Nikula attempting to recover these locks, then set this 3252e52347bdSJani Nikula parameter to '1'. 3253e52347bdSJani Nikula The default parameter value of '0' causes the kernel 3254e52347bdSJani Nikula not to attempt recovery of lost locks. 3255e52347bdSJani Nikula 3256e52347bdSJani Nikula nfs4.layoutstats_timer = 3257e52347bdSJani Nikula [NFSv4.2] Change the rate at which the kernel sends 3258e52347bdSJani Nikula layoutstats to the pNFS metadata server. 3259e52347bdSJani Nikula 3260e52347bdSJani Nikula Setting this to value to 0 causes the kernel to use 3261e52347bdSJani Nikula whatever value is the default set by the layout 3262e52347bdSJani Nikula driver. A non-zero value sets the minimum interval 3263e52347bdSJani Nikula in seconds between layoutstats transmissions. 3264e52347bdSJani Nikula 32656d91929aSJ. Bruce Fields nfsd.inter_copy_offload_enable = 32666d91929aSJ. Bruce Fields [NFSv4.2] When set to 1, the server will support 32676d91929aSJ. Bruce Fields server-to-server copies for which this server is 32686d91929aSJ. Bruce Fields the destination of the copy. 32696d91929aSJ. Bruce Fields 32706d91929aSJ. Bruce Fields nfsd.nfsd4_ssc_umount_timeout = 32716d91929aSJ. Bruce Fields [NFSv4.2] When used as the destination of a 32726d91929aSJ. Bruce Fields server-to-server copy, knfsd temporarily mounts 32736d91929aSJ. Bruce Fields the source server. It caches the mount in case 32746d91929aSJ. Bruce Fields it will be needed again, and discards it if not 32756d91929aSJ. Bruce Fields used for the number of milliseconds specified by 32766d91929aSJ. Bruce Fields this parameter. 32776d91929aSJ. Bruce Fields 3278e52347bdSJani Nikula nfsd.nfs4_disable_idmapping= 3279e52347bdSJani Nikula [NFSv4] When set to the default of '1', the NFSv4 3280e52347bdSJani Nikula server will return only numeric uids and gids to 3281e52347bdSJani Nikula clients using auth_sys, and will accept numeric uids 3282e52347bdSJani Nikula and gids from such clients. This is intended to ease 3283e52347bdSJani Nikula migration from NFSv2/v3. 3284e52347bdSJani Nikula 32856d91929aSJ. Bruce Fields 3286160c7ba3SPaul E. McKenney nmi_backtrace.backtrace_idle [KNL] 3287160c7ba3SPaul E. McKenney Dump stacks even of idle CPUs in response to an 3288160c7ba3SPaul E. McKenney NMI stack-backtrace request. 3289160c7ba3SPaul E. McKenney 3290c0c74acbSHans-Christian Noren Egtvedt nmi_debug= [KNL,SH] Specify one or more actions to take 3291e52347bdSJani Nikula when a NMI is triggered. 3292e52347bdSJani Nikula Format: [state][,regs][,debounce][,die] 3293e52347bdSJani Nikula 3294e52347bdSJani Nikula nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels 3295e52347bdSJani Nikula Format: [panic,][nopanic,][num] 3296e52347bdSJani Nikula Valid num: 0 or 1 3297e52347bdSJani Nikula 0 - turn hardlockup detector in nmi_watchdog off 3298e52347bdSJani Nikula 1 - turn hardlockup detector in nmi_watchdog on 3299e52347bdSJani Nikula When panic is specified, panic when an NMI watchdog 330093285c01SZhenzhong Duan timeout occurs (or 'nopanic' to not panic on an NMI 330193285c01SZhenzhong Duan watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) 330293285c01SZhenzhong Duan To disable both hard and soft lockup detectors, 3303e52347bdSJani Nikula please see 'nowatchdog'. 3304e52347bdSJani Nikula This is useful when you use a panic=... timeout and 3305e52347bdSJani Nikula need the box quickly up again. 3306e52347bdSJani Nikula 3307d22881dcSScott Wood These settings can be accessed at runtime via 3308d22881dcSScott Wood the nmi_watchdog and hardlockup_panic sysctls. 3309d22881dcSScott Wood 3310e52347bdSJani Nikula netpoll.carrier_timeout= 3311e52347bdSJani Nikula [NET] Specifies amount of time (in seconds) that 3312e52347bdSJani Nikula netpoll should wait for a carrier. By default netpoll 3313e52347bdSJani Nikula waits 4 seconds. 3314e52347bdSJani Nikula 3315e52347bdSJani Nikula no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 3316e52347bdSJani Nikula emulation library even if a 387 maths coprocessor 3317e52347bdSJani Nikula is present. 3318e52347bdSJani Nikula 3319372fddf7SKirill A. Shutemov no5lvl [X86-64] Disable 5-level paging mode. Forces 3320372fddf7SKirill A. Shutemov kernel to use 4-level paging instead. 3321372fddf7SKirill A. Shutemov 3322b745cfbaSAndy Lutomirski nofsgsbase [X86] Disables FSGSBASE instructions. 3323dd649bd0SAndy Lutomirski 3324e52347bdSJani Nikula no_console_suspend 3325e52347bdSJani Nikula [HW] Never suspend the console 3326e52347bdSJani Nikula Disable suspending of consoles during suspend and 3327e52347bdSJani Nikula hibernate operations. Once disabled, debugging 3328e52347bdSJani Nikula messages can reach various consoles while the rest 3329e52347bdSJani Nikula of the system is being put to sleep (ie, while 3330e52347bdSJani Nikula debugging driver suspend/resume hooks). This may 3331e52347bdSJani Nikula not work reliably with all consoles, but is known 3332e52347bdSJani Nikula to work with serial and VGA consoles. 3333e52347bdSJani Nikula To facilitate more flexible debugging, we also add 3334e52347bdSJani Nikula console_suspend, a printk module parameter to control 3335e52347bdSJani Nikula it. Users could use console_suspend (usually 3336e52347bdSJani Nikula /sys/module/printk/parameters/console_suspend) to 3337e52347bdSJani Nikula turn on/off it dynamically. 3338e52347bdSJani Nikula 3339c6c40533SKairui Song novmcoredd [KNL,KDUMP] 3340c6c40533SKairui Song Disable device dump. Device dump allows drivers to 3341c6c40533SKairui Song append dump data to vmcore so you can collect driver 3342c6c40533SKairui Song specified debug info. Drivers can append the data 3343c6c40533SKairui Song without any limit and this data is stored in memory, 3344c6c40533SKairui Song so this may cause significant memory stress. Disabling 3345c6c40533SKairui Song device dump can help save memory but the driver debug 3346c6c40533SKairui Song data will be no longer available. This parameter 3347c6c40533SKairui Song is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP 3348c6c40533SKairui Song is set. 3349c6c40533SKairui Song 3350e52347bdSJani Nikula noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 3351e52347bdSJani Nikula caches in the slab allocator. Saves per-node memory, 3352e52347bdSJani Nikula but will impact performance. 3353e52347bdSJani Nikula 3354e52347bdSJani Nikula noalign [KNL,ARM] 3355e52347bdSJani Nikula 3356686140a1SVasily Gorbik noaltinstr [S390] Disables alternative instructions patching 3357686140a1SVasily Gorbik (CPU alternatives feature). 3358686140a1SVasily Gorbik 3359e52347bdSJani Nikula noapic [SMP,APIC] Tells the kernel to not make use of any 3360e52347bdSJani Nikula IOAPICs that may be present in the system. 3361e52347bdSJani Nikula 3362e52347bdSJani Nikula noautogroup Disable scheduler automatic task group creation. 3363e52347bdSJani Nikula 3364e52347bdSJani Nikula nobats [PPC] Do not use BATs for mapping kernel lowmem 3365e52347bdSJani Nikula on "Classic" PPC cores. 3366e52347bdSJani Nikula 3367e52347bdSJani Nikula nocache [ARM] 3368e52347bdSJani Nikula 3369e52347bdSJani Nikula noclflush [BUGS=X86] Don't use the CLFLUSH instruction 3370e52347bdSJani Nikula 3371e4042ad4SPeter Zijlstra delayacct [KNL] Enable per-task delay accounting 3372e52347bdSJani Nikula 3373e52347bdSJani Nikula nodsp [SH] Disable hardware DSP at boot time. 3374e52347bdSJani Nikula 3375e52347bdSJani Nikula noefi Disable EFI runtime services support. 3376e52347bdSJani Nikula 3377f7964378SNicholas Piggin no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel. 3378f7964378SNicholas Piggin 3379e52347bdSJani Nikula noexec [IA-64] 3380e52347bdSJani Nikula 3381e52347bdSJani Nikula noexec [X86] 3382e52347bdSJani Nikula On X86-32 available only on PAE configured kernels. 3383e52347bdSJani Nikula noexec=on: enable non-executable mappings (default) 3384e52347bdSJani Nikula noexec=off: disable non-executable mappings 3385e52347bdSJani Nikula 3386de78a9c4SChristophe Leroy nosmap [X86,PPC] 3387e52347bdSJani Nikula Disable SMAP (Supervisor Mode Access Prevention) 3388e52347bdSJani Nikula even if it is supported by processor. 3389e52347bdSJani Nikula 33900fb1c25aSChristophe Leroy nosmep [X86,PPC] 3391e52347bdSJani Nikula Disable SMEP (Supervisor Mode Execution Prevention) 3392e52347bdSJani Nikula even if it is supported by processor. 3393e52347bdSJani Nikula 3394e52347bdSJani Nikula noexec32 [X86-64] 3395e52347bdSJani Nikula This affects only 32-bit executables. 3396e52347bdSJani Nikula noexec32=on: enable non-executable mappings (default) 3397e52347bdSJani Nikula read doesn't imply executable mappings 3398e52347bdSJani Nikula noexec32=off: disable non-executable mappings 3399e52347bdSJani Nikula read implies executable mappings 3400e52347bdSJani Nikula 3401e52347bdSJani Nikula nofpu [MIPS,SH] Disable hardware FPU at boot time. 3402e52347bdSJani Nikula 3403e52347bdSJani Nikula nofxsr [BUGS=X86-32] Disables x86 floating point extended 3404e52347bdSJani Nikula register save and restore. The kernel will only save 3405e52347bdSJani Nikula legacy floating-point registers on task switch. 3406e52347bdSJani Nikula 34075b280ed4STian Tao nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings. 3408e52347bdSJani Nikula 34098abddd96SNicholas Piggin nohugevmalloc [PPC] Disable kernel huge vmalloc mappings. 34108abddd96SNicholas Piggin 3411e52347bdSJani Nikula nosmt [KNL,S390] Disable symmetric multithreading (SMT). 3412e52347bdSJani Nikula Equivalent to smt=1. 3413e52347bdSJani Nikula 3414be3a5b0eSRandy Dunlap [KNL,X86] Disable symmetric multithreading (SMT). 3415506a66f3SThomas Gleixner nosmt=force: Force disable SMT, cannot be undone 3416506a66f3SThomas Gleixner via the sysfs control file. 341705736e4aSThomas Gleixner 3418a2059825SJosh Poimboeuf nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1 3419a2059825SJosh Poimboeuf (bounds check bypass). With this option data leaks are 3420a2059825SJosh Poimboeuf possible in the system. 342126cb1f36SDiana Craciun 3422e5ce5e72SJeremy Linton nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for 3423e5ce5e72SJeremy Linton the Spectre variant 2 (indirect branch prediction) 3424e5ce5e72SJeremy Linton vulnerability. System may allow data leaks with this 3425e5ce5e72SJeremy Linton option. 3426da285121SDavid Woodhouse 342724f7fc83SKonrad Rzeszutek Wilk nospec_store_bypass_disable 342824f7fc83SKonrad Rzeszutek Wilk [HW] Disable all mitigations for the Speculative Store Bypass vulnerability 342924f7fc83SKonrad Rzeszutek Wilk 34309a32a7e7SNicholas Piggin no_uaccess_flush 34319a32a7e7SNicholas Piggin [PPC] Don't flush the L1-D cache after accessing user data. 34329a32a7e7SNicholas Piggin 3433e52347bdSJani Nikula noxsave [BUGS=X86] Disables x86 extended register state save 3434e52347bdSJani Nikula and restore using xsave. The kernel will fallback to 3435e52347bdSJani Nikula enabling legacy floating-point and sse state. 3436e52347bdSJani Nikula 3437e52347bdSJani Nikula noxsaveopt [X86] Disables xsaveopt used in saving x86 extended 3438e52347bdSJani Nikula register states. The kernel will fall back to use 3439e52347bdSJani Nikula xsave to save the states. By using this parameter, 3440e52347bdSJani Nikula performance of saving the states is degraded because 3441e52347bdSJani Nikula xsave doesn't support modified optimization while 3442e52347bdSJani Nikula xsaveopt supports it on xsaveopt enabled systems. 3443e52347bdSJani Nikula 3444e52347bdSJani Nikula noxsaves [X86] Disables xsaves and xrstors used in saving and 3445e52347bdSJani Nikula restoring x86 extended register state in compacted 3446e52347bdSJani Nikula form of xsave area. The kernel will fall back to use 3447e52347bdSJani Nikula xsaveopt and xrstor to save and restore the states 3448e52347bdSJani Nikula in standard form of xsave area. By using this 3449e52347bdSJani Nikula parameter, xsave area per process might occupy more 3450e52347bdSJani Nikula memory on xsaves enabled systems. 3451e52347bdSJani Nikula 34523cae85f5SFlorian Fainelli nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait 34533cae85f5SFlorian Fainelli in do_idle() and not use the arch_cpu_idle() 34543cae85f5SFlorian Fainelli implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP 34553cae85f5SFlorian Fainelli to be effective. This is useful on platforms where the 34563cae85f5SFlorian Fainelli sleep(SH) or wfi(ARM,ARM64) instructions do not work 34573cae85f5SFlorian Fainelli correctly or when doing power measurements to evalute 34583cae85f5SFlorian Fainelli the impact of the sleep instructions. This is also 34593cae85f5SFlorian Fainelli useful when using JTAG debugger. 3460e52347bdSJani Nikula 3461e52347bdSJani Nikula no_file_caps Tells the kernel not to honor file capabilities. The 3462e52347bdSJani Nikula only way then for a file to be executed with privilege 3463e52347bdSJani Nikula is to be setuid root or executed by root. 3464e52347bdSJani Nikula 3465e52347bdSJani Nikula nohalt [IA-64] Tells the kernel not to use the power saving 3466e52347bdSJani Nikula function PAL_HALT_LIGHT when idle. This increases 3467e52347bdSJani Nikula power-consumption. On the positive side, it reduces 3468e52347bdSJani Nikula interrupt wake-up latency, which may improve performance 3469e52347bdSJani Nikula in certain environments such as networked servers or 3470e52347bdSJani Nikula real-time systems. 3471e52347bdSJani Nikula 34725ead723aSTimur Tabi no_hash_pointers 34735ead723aSTimur Tabi Force pointers printed to the console or buffers to be 34745ead723aSTimur Tabi unhashed. By default, when a pointer is printed via %p 34755ead723aSTimur Tabi format string, that pointer is "hashed", i.e. obscured 34765ead723aSTimur Tabi by hashing the pointer value. This is a security feature 34775ead723aSTimur Tabi that hides actual kernel addresses from unprivileged 34785ead723aSTimur Tabi users, but it also makes debugging the kernel more 34795ead723aSTimur Tabi difficult since unequal pointers can no longer be 34805ead723aSTimur Tabi compared. However, if this command-line option is 34815ead723aSTimur Tabi specified, then all normal pointers will have their true 34825ead723aSTimur Tabi value printed. Pointers printed via %pK may still be 34835ead723aSTimur Tabi hashed. This option should only be specified when 34845ead723aSTimur Tabi debugging the kernel. Please do not use on production 34855ead723aSTimur Tabi kernels. 34865ead723aSTimur Tabi 3487e52347bdSJani Nikula nohibernate [HIBERNATION] Disable hibernation and resume. 3488e52347bdSJani Nikula 3489e52347bdSJani Nikula nohz= [KNL] Boottime enable/disable dynamic ticks 3490e52347bdSJani Nikula Valid arguments: on, off 3491e52347bdSJani Nikula Default: on 3492e52347bdSJani Nikula 3493d94d1053SFrederic Weisbecker nohz_full= [KNL,BOOT,SMP,ISOL] 3494e52347bdSJani Nikula The argument is a cpu list, as described above. 3495e52347bdSJani Nikula In kernels built with CONFIG_NO_HZ_FULL=y, set 3496e52347bdSJani Nikula the specified list of CPUs whose tick will be stopped 3497e52347bdSJani Nikula whenever possible. The boot CPU will be forced outside 3498f99bcb2cSPaul E. McKenney the range to maintain the timekeeping. Any CPUs 3499f99bcb2cSPaul E. McKenney in this list will have their RCU callbacks offloaded, 3500f99bcb2cSPaul E. McKenney just as if they had also been called out in the 3501f99bcb2cSPaul E. McKenney rcu_nocbs= boot parameter. 3502e52347bdSJani Nikula 3503e52347bdSJani Nikula noiotrap [SH] Disables trapped I/O port accesses. 3504e52347bdSJani Nikula 3505e52347bdSJani Nikula noirqdebug [X86-32] Disables the code which attempts to detect and 3506e52347bdSJani Nikula disable unhandled interrupt sources. 3507e52347bdSJani Nikula 3508e52347bdSJani Nikula no_timer_check [X86,APIC] Disables the code which tests for 3509e52347bdSJani Nikula broken timer IRQ sources. 3510e52347bdSJani Nikula 3511e52347bdSJani Nikula noisapnp [ISAPNP] Disables ISA PnP code. 3512e52347bdSJani Nikula 3513e52347bdSJani Nikula noinitrd [RAM] Tells the kernel not to load any configured 3514e52347bdSJani Nikula initial RAM disk. 3515e52347bdSJani Nikula 3516e52347bdSJani Nikula nointremap [X86-64, Intel-IOMMU] Do not enable interrupt 3517e52347bdSJani Nikula remapping. 3518e52347bdSJani Nikula [Deprecated - use intremap=off] 3519e52347bdSJani Nikula 3520e52347bdSJani Nikula nointroute [IA-64] 3521e52347bdSJani Nikula 3522e52347bdSJani Nikula noinvpcid [X86] Disable the INVPCID cpu feature. 3523e52347bdSJani Nikula 3524e52347bdSJani Nikula nojitter [IA-64] Disables jitter checking for ITC timers. 3525e52347bdSJani Nikula 3526e52347bdSJani Nikula no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver 3527e52347bdSJani Nikula 3528e52347bdSJani Nikula no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page 3529e52347bdSJani Nikula fault handling. 3530e52347bdSJani Nikula 3531e7aa8c2eSLinus Torvalds no-vmw-sched-clock 3532e7aa8c2eSLinus Torvalds [X86,PV_OPS] Disable paravirtualized VMware scheduler 3533e7aa8c2eSLinus Torvalds clock and use the default one. 3534e7aa8c2eSLinus Torvalds 3535e73a8f38SAlexey Makhalov no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time 3536e0685fa2SSteven Price accounting. steal time is computed, but won't 3537e0685fa2SSteven Price influence scheduler behaviour 3538e52347bdSJani Nikula 3539e52347bdSJani Nikula nolapic [X86-32,APIC] Do not enable or use the local APIC. 3540e52347bdSJani Nikula 3541e52347bdSJani Nikula nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 3542e52347bdSJani Nikula 3543e52347bdSJani Nikula noltlbs [PPC] Do not use large page/tlb entries for kernel 3544e52347bdSJani Nikula lowmem mapping on PPC40x and PPC8xx 3545e52347bdSJani Nikula 3546e52347bdSJani Nikula nomca [IA-64] Disable machine check abort handling 3547e52347bdSJani Nikula 3548e52347bdSJani Nikula nomce [X86-32] Disable Machine Check Exception 3549e52347bdSJani Nikula 3550e52347bdSJani Nikula nomfgpt [X86-32] Disable Multi-Function General Purpose 3551e52347bdSJani Nikula Timer usage (for AMD Geode machines). 3552e52347bdSJani Nikula 3553e52347bdSJani Nikula nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to 3554e52347bdSJani Nikula shutdown the other cpus. Instead use the REBOOT_VECTOR 3555e52347bdSJani Nikula irq. 3556e52347bdSJani Nikula 3557e52347bdSJani Nikula nomodule Disable module load 3558e52347bdSJani Nikula 3559e52347bdSJani Nikula nopat [X86] Disable PAT (page attribute table extension of 3560e52347bdSJani Nikula pagetables) support. 3561e52347bdSJani Nikula 35620790c9aaSAndy Lutomirski nopcid [X86-64] Disable the PCID cpu feature. 35630790c9aaSAndy Lutomirski 3564e52347bdSJani Nikula norandmaps Don't use address space randomization. Equivalent to 3565e52347bdSJani Nikula echo 0 > /proc/sys/kernel/randomize_va_space 3566e52347bdSJani Nikula 3567e52347bdSJani Nikula noreplace-smp [X86-32,SMP] Don't replace SMP instructions 3568e52347bdSJani Nikula with UP alternatives 3569e52347bdSJani Nikula 3570e52347bdSJani Nikula nordrand [X86] Disable kernel use of the RDRAND and 3571e52347bdSJani Nikula RDSEED instructions even if they are supported 3572e52347bdSJani Nikula by the processor. RDRAND and RDSEED are still 3573e52347bdSJani Nikula available to user space applications. 3574e52347bdSJani Nikula 3575e52347bdSJani Nikula noresume [SWSUSP] Disables resume and restores original swap 3576e52347bdSJani Nikula space. 3577e52347bdSJani Nikula 3578e52347bdSJani Nikula no-scroll [VGA] Disables scrollback. 3579e52347bdSJani Nikula This is required for the Braillex ib80-piezo Braille 3580e52347bdSJani Nikula reader made by F.H. Papenmeier (Germany). 3581e52347bdSJani Nikula 3582e52347bdSJani Nikula nosbagart [IA-64] 3583e52347bdSJani Nikula 3584e52347bdSJani Nikula nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 3585e52347bdSJani Nikula 358638853a30SJarkko Sakkinen nosgx [X86-64,SGX] Disables Intel SGX kernel support. 358738853a30SJarkko Sakkinen 3588e52347bdSJani Nikula nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 3589e52347bdSJani Nikula and disable the IO APIC. legacy for "maxcpus=0". 3590e52347bdSJani Nikula 3591e52347bdSJani Nikula nosoftlockup [KNL] Disable the soft-lockup detector. 3592e52347bdSJani Nikula 3593e52347bdSJani Nikula nosync [HW,M68K] Disables sync negotiation for all devices. 3594e52347bdSJani Nikula 3595e52347bdSJani Nikula nowatchdog [KNL] Disable both lockup detectors, i.e. 3596e52347bdSJani Nikula soft-lockup and NMI watchdog (hard-lockup). 3597e52347bdSJani Nikula 3598e52347bdSJani Nikula nowb [ARM] 3599e52347bdSJani Nikula 3600e52347bdSJani Nikula nox2apic [X86-64,APIC] Do not enable x2APIC mode. 3601e52347bdSJani Nikula 3602e52347bdSJani Nikula cpu0_hotplug [X86] Turn on CPU0 hotplug feature when 3603e52347bdSJani Nikula CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. 3604e52347bdSJani Nikula Some features depend on CPU0. Known dependencies are: 3605e52347bdSJani Nikula 1. Resume from suspend/hibernate depends on CPU0. 3606e52347bdSJani Nikula Suspend/hibernate will fail if CPU0 is offline and you 3607e52347bdSJani Nikula need to online CPU0 before suspend/hibernate. 3608e52347bdSJani Nikula 2. PIC interrupts also depend on CPU0. CPU0 can't be 3609e52347bdSJani Nikula removed if a PIC interrupt is detected. 3610e52347bdSJani Nikula It's said poweroff/reboot may depend on CPU0 on some 3611e52347bdSJani Nikula machines although I haven't seen such issues so far 3612e52347bdSJani Nikula after CPU0 is offline on a few tested machines. 3613e52347bdSJani Nikula If the dependencies are under your control, you can 3614e52347bdSJani Nikula turn on cpu0_hotplug. 3615e52347bdSJani Nikula 361635b55ef2SNoam Camus nps_mtm_hs_ctr= [KNL,ARC] 361735b55ef2SNoam Camus This parameter sets the maximum duration, in 361835b55ef2SNoam Camus cycles, each HW thread of the CTOP can run 361935b55ef2SNoam Camus without interruptions, before HW switches it. 362035b55ef2SNoam Camus The actual maximum duration is 16 times this 362135b55ef2SNoam Camus parameter's value. 362235b55ef2SNoam Camus Format: integer between 1 and 255 362335b55ef2SNoam Camus Default: 255 362435b55ef2SNoam Camus 3625e52347bdSJani Nikula nptcg= [IA-64] Override max number of concurrent global TLB 3626e52347bdSJani Nikula purges which is reported from either PAL_VM_SUMMARY or 3627e52347bdSJani Nikula SAL PALO. 3628e52347bdSJani Nikula 3629e52347bdSJani Nikula nr_cpus= [SMP] Maximum number of processors that an SMP kernel 3630e52347bdSJani Nikula could support. nr_cpus=n : n >= 1 limits the kernel to 3631e52347bdSJani Nikula support 'n' processors. It could be larger than the 3632e52347bdSJani Nikula number of already plugged CPU during bootup, later in 3633e52347bdSJani Nikula runtime you can physically add extra cpu until it reaches 3634e52347bdSJani Nikula n. So during boot up some boot time memory for per-cpu 3635e52347bdSJani Nikula variables need be pre-allocated for later physical cpu 3636e52347bdSJani Nikula hot plugging. 3637e52347bdSJani Nikula 3638e52347bdSJani Nikula nr_uarts= [SERIAL] maximum number of UARTs to be registered. 3639e52347bdSJani Nikula 3640544ef682SBarry Song numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only 3641544ef682SBarry Song set up a single NUMA node spanning all memory. 3642544ef682SBarry Song 364300b072c0SBarry Song numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic 364400b072c0SBarry Song NUMA balancing. 3645e52347bdSJani Nikula Allowed values are enable and disable 3646e52347bdSJani Nikula 3647e52347bdSJani Nikula numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 3648c9bff3eeSMichal Hocko 'node', 'default' can be specified 3649e52347bdSJani Nikula This can be set from sysctl after boot. 365057043247SMauro Carvalho Chehab See Documentation/admin-guide/sysctl/vm.rst for details. 3651e52347bdSJani Nikula 3652e52347bdSJani Nikula ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. 3653a74e2a22SMauro Carvalho Chehab See Documentation/core-api/debugging-via-ohci1394.rst for more 3654e52347bdSJani Nikula info. 3655e52347bdSJani Nikula 3656e52347bdSJani Nikula olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 3657e52347bdSJani Nikula Rather than timing out after 20 ms if an EC 3658e52347bdSJani Nikula command is not properly ACKed, override the length 3659e52347bdSJani Nikula of the timeout. We have interrupts disabled while 3660e52347bdSJani Nikula waiting for the ACK, so if this is set too high 3661e52347bdSJani Nikula interrupts *may* be lost! 3662e52347bdSJani Nikula 3663e52347bdSJani Nikula omap_mux= [OMAP] Override bootloader pin multiplexing. 3664e52347bdSJani Nikula Format: <mux_mode0.mode_name=value>... 3665e52347bdSJani Nikula For example, to override I2C bus2: 3666e52347bdSJani Nikula omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 3667e52347bdSJani Nikula 3668e52347bdSJani Nikula oops=panic Always panic on oopses. Default is to just kill the 3669e52347bdSJani Nikula process, but there is a small probability of 3670e52347bdSJani Nikula deadlocking the machine. 3671e52347bdSJani Nikula This will also cause panics on machine check exceptions. 3672e52347bdSJani Nikula Useful together with panic=30 to trigger a reboot. 3673e52347bdSJani Nikula 3674e900a918SDan Williams page_alloc.shuffle= 3675e900a918SDan Williams [KNL] Boolean flag to control whether the page allocator 3676e900a918SDan Williams should randomize its free lists. The randomization may 3677e900a918SDan Williams be automatically enabled if the kernel detects it is 3678e900a918SDan Williams running on a platform with a direct-mapped memory-side 3679e900a918SDan Williams cache, and this parameter can be used to 3680e900a918SDan Williams override/disable that behavior. The state of the flag 3681e900a918SDan Williams can be read from sysfs at: 3682e900a918SDan Williams /sys/module/page_alloc/parameters/shuffle. 3683e900a918SDan Williams 3684e52347bdSJani Nikula page_owner= [KNL] Boot-time page_owner enabling option. 3685e52347bdSJani Nikula Storage of the information about who allocated 3686e52347bdSJani Nikula each page is disabled in default. With this switch, 3687e52347bdSJani Nikula we can turn it on. 3688e52347bdSJani Nikula on: enable the feature 3689e52347bdSJani Nikula 3690e52347bdSJani Nikula page_poison= [KNL] Boot-time parameter changing the state of 36918c9a134cSKees Cook poisoning on the buddy allocator, available with 36928c9a134cSKees Cook CONFIG_PAGE_POISONING=y. 36938c9a134cSKees Cook off: turn off poisoning (default) 3694e52347bdSJani Nikula on: turn on poisoning 3695e52347bdSJani Nikula 3696f58780a8SGavin Shan page_reporting.page_reporting_order= 3697f58780a8SGavin Shan [KNL] Minimal page reporting order 3698f58780a8SGavin Shan Format: <integer> 3699f58780a8SGavin Shan Adjust the minimal page reporting order. The page 3700f58780a8SGavin Shan reporting is disabled when it exceeds (MAX_ORDER-1). 3701f58780a8SGavin Shan 3702e52347bdSJani Nikula panic= [KNL] Kernel behaviour on panic: delay <timeout> 3703e52347bdSJani Nikula timeout > 0: seconds before rebooting 3704e52347bdSJani Nikula timeout = 0: wait forever 3705e52347bdSJani Nikula timeout < 0: reboot immediately 3706e52347bdSJani Nikula Format: <timeout> 3707e52347bdSJani Nikula 3708d999bd93SFeng Tang panic_print= Bitmask for printing system info when panic happens. 3709d999bd93SFeng Tang User can chose combination of the following bits: 3710d999bd93SFeng Tang bit 0: print all tasks info 3711d999bd93SFeng Tang bit 1: print system memory info 3712d999bd93SFeng Tang bit 2: print timer info 3713d999bd93SFeng Tang bit 3: print locks info if CONFIG_LOCKDEP is on 3714d999bd93SFeng Tang bit 4: print ftrace buffer 3715de6da1e8SFeng Tang bit 5: print all printk messages in buffer 3716d999bd93SFeng Tang 3717db38d5c1SRafael Aquini panic_on_taint= Bitmask for conditionally calling panic() in add_taint() 3718db38d5c1SRafael Aquini Format: <hex>[,nousertaint] 3719db38d5c1SRafael Aquini Hexadecimal bitmask representing the set of TAINT flags 3720db38d5c1SRafael Aquini that will cause the kernel to panic when add_taint() is 3721db38d5c1SRafael Aquini called with any of the flags in this set. 3722db38d5c1SRafael Aquini The optional switch "nousertaint" can be utilized to 3723db38d5c1SRafael Aquini prevent userspace forced crashes by writing to sysctl 3724db38d5c1SRafael Aquini /proc/sys/kernel/tainted any flagset matching with the 3725db38d5c1SRafael Aquini bitmask set on panic_on_taint. 3726db38d5c1SRafael Aquini See Documentation/admin-guide/tainted-kernels.rst for 3727db38d5c1SRafael Aquini extra details on the taint flags that users can pick 3728db38d5c1SRafael Aquini to compose the bitmask to assign to panic_on_taint. 3729db38d5c1SRafael Aquini 3730e52347bdSJani Nikula panic_on_warn panic() instead of WARN(). Useful to cause kdump 3731e52347bdSJani Nikula on a WARN(). 3732e52347bdSJani Nikula 3733e52347bdSJani Nikula crash_kexec_post_notifiers 3734e52347bdSJani Nikula Run kdump after running panic-notifiers and dumping 3735e52347bdSJani Nikula kmsg. This only for the users who doubt kdump always 3736e52347bdSJani Nikula succeeds in any situation. 3737e52347bdSJani Nikula Note that this also increases risks of kdump failure, 3738e52347bdSJani Nikula because some panic notifiers can make the crashed 3739e52347bdSJani Nikula kernel more unstable. 3740e52347bdSJani Nikula 3741e52347bdSJani Nikula parkbd.port= [HW] Parallel port number the keyboard adapter is 3742e52347bdSJani Nikula connected to, default is 0. 3743e52347bdSJani Nikula Format: <parport#> 3744e52347bdSJani Nikula parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 3745e52347bdSJani Nikula 0 for XT, 1 for AT (default is AT). 3746e52347bdSJani Nikula Format: <mode> 3747e52347bdSJani Nikula 3748e52347bdSJani Nikula parport= [HW,PPT] Specify parallel ports. 0 disables. 3749e52347bdSJani Nikula Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 3750e52347bdSJani Nikula Use 'auto' to force the driver to use any 3751e52347bdSJani Nikula IRQ/DMA settings detected (the default is to 3752e52347bdSJani Nikula ignore detected IRQ/DMA settings because of 3753e52347bdSJani Nikula possible conflicts). You can specify the base 3754e52347bdSJani Nikula address, IRQ, and DMA settings; IRQ and DMA 3755e52347bdSJani Nikula should be numbers, or 'auto' (for using detected 3756e52347bdSJani Nikula settings on that particular port), or 'nofifo' 3757e52347bdSJani Nikula (to avoid using a FIFO even if it is detected). 3758e52347bdSJani Nikula Parallel ports are assigned in the order they 3759e52347bdSJani Nikula are specified on the command line, starting 3760e52347bdSJani Nikula with parport0. 3761e52347bdSJani Nikula 3762e52347bdSJani Nikula parport_init_mode= [HW,PPT] 3763e52347bdSJani Nikula Configure VIA parallel port to operate in 3764e52347bdSJani Nikula a specific mode. This is necessary on Pegasos 3765e52347bdSJani Nikula computer where firmware has no options for setting 3766e52347bdSJani Nikula up parallel port mode and sets it to spp. 3767e52347bdSJani Nikula Currently this function knows 686a and 8231 chips. 3768e52347bdSJani Nikula Format: [spp|ps2|epp|ecp|ecpepp] 3769e52347bdSJani Nikula 3770426e2c6aSMaciej W. Rozycki pata_legacy.all= [HW,LIBATA] 3771426e2c6aSMaciej W. Rozycki Format: <int> 3772426e2c6aSMaciej W. Rozycki Set to non-zero to probe primary and secondary ISA 3773426e2c6aSMaciej W. Rozycki port ranges on PCI systems where no PCI PATA device 3774426e2c6aSMaciej W. Rozycki has been found at either range. Disabled by default. 3775426e2c6aSMaciej W. Rozycki 3776426e2c6aSMaciej W. Rozycki pata_legacy.autospeed= [HW,LIBATA] 3777426e2c6aSMaciej W. Rozycki Format: <int> 3778426e2c6aSMaciej W. Rozycki Set to non-zero if a chip is present that snoops speed 3779426e2c6aSMaciej W. Rozycki changes. Disabled by default. 3780426e2c6aSMaciej W. Rozycki 3781426e2c6aSMaciej W. Rozycki pata_legacy.ht6560a= [HW,LIBATA] 3782426e2c6aSMaciej W. Rozycki Format: <int> 3783426e2c6aSMaciej W. Rozycki Set to 1, 2, or 3 for HT 6560A on the primary channel, 3784426e2c6aSMaciej W. Rozycki the secondary channel, or both channels respectively. 3785426e2c6aSMaciej W. Rozycki Disabled by default. 3786426e2c6aSMaciej W. Rozycki 3787426e2c6aSMaciej W. Rozycki pata_legacy.ht6560b= [HW,LIBATA] 3788426e2c6aSMaciej W. Rozycki Format: <int> 3789426e2c6aSMaciej W. Rozycki Set to 1, 2, or 3 for HT 6560B on the primary channel, 3790426e2c6aSMaciej W. Rozycki the secondary channel, or both channels respectively. 3791426e2c6aSMaciej W. Rozycki Disabled by default. 3792426e2c6aSMaciej W. Rozycki 3793426e2c6aSMaciej W. Rozycki pata_legacy.iordy_mask= [HW,LIBATA] 3794426e2c6aSMaciej W. Rozycki Format: <int> 3795426e2c6aSMaciej W. Rozycki IORDY enable mask. Set individual bits to allow IORDY 3796426e2c6aSMaciej W. Rozycki for the respective channel. Bit 0 is for the first 3797426e2c6aSMaciej W. Rozycki legacy channel handled by this driver, bit 1 is for 3798426e2c6aSMaciej W. Rozycki the second channel, and so on. The sequence will often 3799426e2c6aSMaciej W. Rozycki correspond to the primary legacy channel, the secondary 3800426e2c6aSMaciej W. Rozycki legacy channel, and so on, but the handling of a PCI 3801426e2c6aSMaciej W. Rozycki bus and the use of other driver options may interfere 3802426e2c6aSMaciej W. Rozycki with the sequence. By default IORDY is allowed across 3803426e2c6aSMaciej W. Rozycki all channels. 3804426e2c6aSMaciej W. Rozycki 3805426e2c6aSMaciej W. Rozycki pata_legacy.opti82c46x= [HW,LIBATA] 3806426e2c6aSMaciej W. Rozycki Format: <int> 3807426e2c6aSMaciej W. Rozycki Set to 1, 2, or 3 for Opti 82c611A on the primary 3808426e2c6aSMaciej W. Rozycki channel, the secondary channel, or both channels 3809426e2c6aSMaciej W. Rozycki respectively. Disabled by default. 3810426e2c6aSMaciej W. Rozycki 3811426e2c6aSMaciej W. Rozycki pata_legacy.opti82c611a= [HW,LIBATA] 3812426e2c6aSMaciej W. Rozycki Format: <int> 3813426e2c6aSMaciej W. Rozycki Set to 1, 2, or 3 for Opti 82c465MV on the primary 3814426e2c6aSMaciej W. Rozycki channel, the secondary channel, or both channels 3815426e2c6aSMaciej W. Rozycki respectively. Disabled by default. 3816426e2c6aSMaciej W. Rozycki 3817426e2c6aSMaciej W. Rozycki pata_legacy.pio_mask= [HW,LIBATA] 3818426e2c6aSMaciej W. Rozycki Format: <int> 3819426e2c6aSMaciej W. Rozycki PIO mode mask for autospeed devices. Set individual 3820426e2c6aSMaciej W. Rozycki bits to allow the use of the respective PIO modes. 3821426e2c6aSMaciej W. Rozycki Bit 0 is for mode 0, bit 1 is for mode 1, and so on. 3822426e2c6aSMaciej W. Rozycki All modes allowed by default. 3823426e2c6aSMaciej W. Rozycki 3824426e2c6aSMaciej W. Rozycki pata_legacy.probe_all= [HW,LIBATA] 3825426e2c6aSMaciej W. Rozycki Format: <int> 3826426e2c6aSMaciej W. Rozycki Set to non-zero to probe tertiary and further ISA 3827426e2c6aSMaciej W. Rozycki port ranges on PCI systems. Disabled by default. 3828426e2c6aSMaciej W. Rozycki 38297d33004dSMaciej W. Rozycki pata_legacy.probe_mask= [HW,LIBATA] 38307d33004dSMaciej W. Rozycki Format: <int> 38317d33004dSMaciej W. Rozycki Probe mask for legacy ISA PATA ports. Depending on 38327d33004dSMaciej W. Rozycki platform configuration and the use of other driver 38337d33004dSMaciej W. Rozycki options up to 6 legacy ports are supported: 0x1f0, 38347d33004dSMaciej W. Rozycki 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing 38357d33004dSMaciej W. Rozycki of individual ports can be disabled by setting the 38367d33004dSMaciej W. Rozycki corresponding bits in the mask to 1. Bit 0 is for 38377d33004dSMaciej W. Rozycki the first port in the list above (0x1f0), and so on. 38387d33004dSMaciej W. Rozycki By default all supported ports are probed. 38397d33004dSMaciej W. Rozycki 3840426e2c6aSMaciej W. Rozycki pata_legacy.qdi= [HW,LIBATA] 3841426e2c6aSMaciej W. Rozycki Format: <int> 3842426e2c6aSMaciej W. Rozycki Set to non-zero to probe QDI controllers. By default 3843426e2c6aSMaciej W. Rozycki set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise. 3844426e2c6aSMaciej W. Rozycki 3845426e2c6aSMaciej W. Rozycki pata_legacy.winbond= [HW,LIBATA] 3846426e2c6aSMaciej W. Rozycki Format: <int> 3847426e2c6aSMaciej W. Rozycki Set to non-zero to probe Winbond controllers. Use 3848426e2c6aSMaciej W. Rozycki the standard I/O port (0x130) if 1, otherwise the 3849426e2c6aSMaciej W. Rozycki value given is the I/O port to use (typically 0x1b0). 3850426e2c6aSMaciej W. Rozycki By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE, 3851426e2c6aSMaciej W. Rozycki 0 otherwise. 3852426e2c6aSMaciej W. Rozycki 38536ddcec95SMaciej W. Rozycki pata_platform.pio_mask= [HW,LIBATA] 38546ddcec95SMaciej W. Rozycki Format: <int> 38556ddcec95SMaciej W. Rozycki Supported PIO mode mask. Set individual bits to allow 38566ddcec95SMaciej W. Rozycki the use of the respective PIO modes. Bit 0 is for 38576ddcec95SMaciej W. Rozycki mode 0, bit 1 is for mode 1, and so on. Mode 0 only 38586ddcec95SMaciej W. Rozycki allowed by default. 38596ddcec95SMaciej W. Rozycki 3860e52347bdSJani Nikula pause_on_oops= 3861e52347bdSJani Nikula Halt all CPUs after the first oops has been printed for 3862e52347bdSJani Nikula the specified number of seconds. This is to be used if 3863e52347bdSJani Nikula your oopses keep scrolling off the screen. 3864e52347bdSJani Nikula 3865e52347bdSJani Nikula pcbit= [HW,ISDN] 3866e52347bdSJani Nikula 3867e52347bdSJani Nikula pcd. [PARIDE] 3868e52347bdSJani Nikula See header of drivers/block/paride/pcd.c. 3869e7751617SMauro Carvalho Chehab See also Documentation/admin-guide/blockdev/paride.rst. 3870e52347bdSJani Nikula 387107d8d7e5SLogan Gunthorpe pci=option[,option...] [PCI] various PCI subsystem options. 387207d8d7e5SLogan Gunthorpe 387307d8d7e5SLogan Gunthorpe Some options herein operate on a specific device 387407d8d7e5SLogan Gunthorpe or a set of devices (<pci_dev>). These are 387507d8d7e5SLogan Gunthorpe specified in one of the following formats: 387607d8d7e5SLogan Gunthorpe 387745db3370SLogan Gunthorpe [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]* 387807d8d7e5SLogan Gunthorpe pci:<vendor>:<device>[:<subvendor>:<subdevice>] 387907d8d7e5SLogan Gunthorpe 388007d8d7e5SLogan Gunthorpe Note: the first format specifies a PCI 388107d8d7e5SLogan Gunthorpe bus/device/function address which may change 388207d8d7e5SLogan Gunthorpe if new hardware is inserted, if motherboard 388307d8d7e5SLogan Gunthorpe firmware changes, or due to changes caused 388407d8d7e5SLogan Gunthorpe by other kernel parameters. If the 388507d8d7e5SLogan Gunthorpe domain is left unspecified, it is 388645db3370SLogan Gunthorpe taken to be zero. Optionally, a path 388745db3370SLogan Gunthorpe to a device through multiple device/function 388845db3370SLogan Gunthorpe addresses can be specified after the base 388945db3370SLogan Gunthorpe address (this is more robust against 389045db3370SLogan Gunthorpe renumbering issues). The second format 389107d8d7e5SLogan Gunthorpe selects devices using IDs from the 389207d8d7e5SLogan Gunthorpe configuration space which may match multiple 389307d8d7e5SLogan Gunthorpe devices in the system. 389407d8d7e5SLogan Gunthorpe 389511eb0e0eSSinan Kaya earlydump dump PCI config space before the kernel 3896e52347bdSJani Nikula changes anything 3897e52347bdSJani Nikula off [X86] don't probe for the PCI bus 3898e52347bdSJani Nikula bios [X86-32] force use of PCI BIOS, don't access 3899e52347bdSJani Nikula the hardware directly. Use this if your machine 3900e52347bdSJani Nikula has a non-standard PCI host bridge. 3901e52347bdSJani Nikula nobios [X86-32] disallow use of PCI BIOS, only direct 3902e52347bdSJani Nikula hardware access methods are allowed. Use this 3903e52347bdSJani Nikula if you experience crashes upon bootup and you 3904e52347bdSJani Nikula suspect they are caused by the BIOS. 3905e52347bdSJani Nikula conf1 [X86] Force use of PCI Configuration Access 3906e52347bdSJani Nikula Mechanism 1 (config address in IO port 0xCF8, 3907e52347bdSJani Nikula data in IO port 0xCFC, both 32-bit). 3908e52347bdSJani Nikula conf2 [X86] Force use of PCI Configuration Access 3909e52347bdSJani Nikula Mechanism 2 (IO port 0xCF8 is an 8-bit port for 3910e52347bdSJani Nikula the function, IO port 0xCFA, also 8-bit, sets 3911e52347bdSJani Nikula bus number. The config space is then accessed 3912e52347bdSJani Nikula through ports 0xC000-0xCFFF). 3913e52347bdSJani Nikula See http://wiki.osdev.org/PCI for more info 3914e52347bdSJani Nikula on the configuration access mechanisms. 3915e52347bdSJani Nikula noaer [PCIE] If the PCIEAER kernel config parameter is 3916e52347bdSJani Nikula enabled, this kernel boot option can be used to 3917e52347bdSJani Nikula disable the use of PCIE advanced error reporting. 3918e52347bdSJani Nikula nodomains [PCI] Disable support for multiple PCI 3919e52347bdSJani Nikula root domains (aka PCI segments, in ACPI-speak). 3920e52347bdSJani Nikula nommconf [X86] Disable use of MMCONFIG for PCI 3921e52347bdSJani Nikula Configuration 3922e52347bdSJani Nikula check_enable_amd_mmconf [X86] check for and enable 3923e52347bdSJani Nikula properly configured MMIO access to PCI 3924e52347bdSJani Nikula config space on AMD family 10h CPU 3925e52347bdSJani Nikula nomsi [MSI] If the PCI_MSI kernel config parameter is 3926e52347bdSJani Nikula enabled, this kernel boot option can be used to 3927e52347bdSJani Nikula disable the use of MSI interrupts system-wide. 3928e52347bdSJani Nikula noioapicquirk [APIC] Disable all boot interrupt quirks. 3929e52347bdSJani Nikula Safety option to keep boot IRQs enabled. This 3930e52347bdSJani Nikula should never be necessary. 3931e52347bdSJani Nikula ioapicreroute [APIC] Enable rerouting of boot IRQs to the 3932e52347bdSJani Nikula primary IO-APIC for bridges that cannot disable 3933e52347bdSJani Nikula boot IRQs. This fixes a source of spurious IRQs 3934e52347bdSJani Nikula when the system masks IRQs. 3935e52347bdSJani Nikula noioapicreroute [APIC] Disable workaround that uses the 3936e52347bdSJani Nikula boot IRQ equivalent of an IRQ that connects to 3937e52347bdSJani Nikula a chipset where boot IRQs cannot be disabled. 3938e52347bdSJani Nikula The opposite of ioapicreroute. 3939e52347bdSJani Nikula biosirq [X86-32] Use PCI BIOS calls to get the interrupt 3940e52347bdSJani Nikula routing table. These calls are known to be buggy 3941e52347bdSJani Nikula on several machines and they hang the machine 3942e52347bdSJani Nikula when used, but on other computers it's the only 3943e52347bdSJani Nikula way to get the interrupt routing table. Try 3944e52347bdSJani Nikula this option if the kernel is unable to allocate 3945e52347bdSJani Nikula IRQs or discover secondary PCI buses on your 3946e52347bdSJani Nikula motherboard. 3947e52347bdSJani Nikula rom [X86] Assign address space to expansion ROMs. 3948e52347bdSJani Nikula Use with caution as certain devices share 3949e52347bdSJani Nikula address decoders between ROMs and other 3950e52347bdSJani Nikula resources. 3951e52347bdSJani Nikula norom [X86] Do not assign address space to 3952e52347bdSJani Nikula expansion ROMs that do not already have 3953e52347bdSJani Nikula BIOS assigned address ranges. 3954e52347bdSJani Nikula nobar [X86] Do not assign address space to the 3955e52347bdSJani Nikula BARs that weren't assigned by the BIOS. 3956e52347bdSJani Nikula irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 3957e52347bdSJani Nikula assigned automatically to PCI devices. You can 3958e52347bdSJani Nikula make the kernel exclude IRQs of your ISA cards 3959e52347bdSJani Nikula this way. 3960e52347bdSJani Nikula pirqaddr=0xAAAAA [X86] Specify the physical address 3961e52347bdSJani Nikula of the PIRQ table (normally generated 3962e52347bdSJani Nikula by the BIOS) if it is outside the 3963e52347bdSJani Nikula F0000h-100000h range. 3964e52347bdSJani Nikula lastbus=N [X86] Scan all buses thru bus #N. Can be 3965e52347bdSJani Nikula useful if the kernel is unable to find your 3966e52347bdSJani Nikula secondary buses and you want to tell it 3967e52347bdSJani Nikula explicitly which ones they are. 3968e52347bdSJani Nikula assign-busses [X86] Always assign all PCI bus 3969e52347bdSJani Nikula numbers ourselves, overriding 3970e52347bdSJani Nikula whatever the firmware may have done. 3971e52347bdSJani Nikula usepirqmask [X86] Honor the possible IRQ mask stored 3972e52347bdSJani Nikula in the BIOS $PIR table. This is needed on 3973e52347bdSJani Nikula some systems with broken BIOSes, notably 3974e52347bdSJani Nikula some HP Pavilion N5400 and Omnibook XE3 3975e52347bdSJani Nikula notebooks. This will have no effect if ACPI 3976e52347bdSJani Nikula IRQ routing is enabled. 3977e52347bdSJani Nikula noacpi [X86] Do not use ACPI for IRQ routing 3978e52347bdSJani Nikula or for PCI scanning. 3979e52347bdSJani Nikula use_crs [X86] Use PCI host bridge window information 3980e52347bdSJani Nikula from ACPI. On BIOSes from 2008 or later, this 3981e52347bdSJani Nikula is enabled by default. If you need to use this, 3982e52347bdSJani Nikula please report a bug. 3983e52347bdSJani Nikula nocrs [X86] Ignore PCI host bridge windows from ACPI. 3984e52347bdSJani Nikula If you need to use this, please report a bug. 3985e52347bdSJani Nikula routeirq Do IRQ routing for all PCI devices. 3986e52347bdSJani Nikula This is normally done in pci_enable_device(), 3987e52347bdSJani Nikula so this option is a temporary workaround 3988e52347bdSJani Nikula for broken drivers that don't call it. 3989e52347bdSJani Nikula skip_isa_align [X86] do not align io start addr, so can 3990e52347bdSJani Nikula handle more pci cards 3991e52347bdSJani Nikula noearly [X86] Don't do any early type 1 scanning. 3992e52347bdSJani Nikula This might help on some broken boards which 3993e52347bdSJani Nikula machine check when some devices' config space 3994e52347bdSJani Nikula is read. But various workarounds are disabled 3995e52347bdSJani Nikula and some IOMMU drivers will not work. 3996e52347bdSJani Nikula bfsort Sort PCI devices into breadth-first order. 3997e52347bdSJani Nikula This sorting is done to get a device 3998e52347bdSJani Nikula order compatible with older (<= 2.4) kernels. 3999e52347bdSJani Nikula nobfsort Don't sort PCI devices into breadth-first order. 4000e52347bdSJani Nikula pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) 4001e52347bdSJani Nikula tuning and use the BIOS-configured MPS defaults. 4002e52347bdSJani Nikula pcie_bus_safe Set every device's MPS to the largest value 4003e52347bdSJani Nikula supported by all devices below the root complex. 4004e52347bdSJani Nikula pcie_bus_perf Set device MPS to the largest allowable MPS 4005e52347bdSJani Nikula based on its parent bus. Also set MRRS (Max 4006e52347bdSJani Nikula Read Request Size) to the largest supported 4007e52347bdSJani Nikula value (no larger than the MPS that the device 4008e52347bdSJani Nikula or bus can support) for best performance. 4009e52347bdSJani Nikula pcie_bus_peer2peer Set every device's MPS to 128B, which 4010e52347bdSJani Nikula every device is guaranteed to support. This 4011e52347bdSJani Nikula configuration allows peer-to-peer DMA between 4012e52347bdSJani Nikula any pair of devices, possibly at the cost of 4013e52347bdSJani Nikula reduced performance. This also guarantees 4014e52347bdSJani Nikula that hot-added devices will work. 4015e52347bdSJani Nikula cbiosize=nn[KMG] The fixed amount of bus space which is 4016e52347bdSJani Nikula reserved for the CardBus bridge's IO window. 4017e52347bdSJani Nikula The default value is 256 bytes. 4018e52347bdSJani Nikula cbmemsize=nn[KMG] The fixed amount of bus space which is 4019e52347bdSJani Nikula reserved for the CardBus bridge's memory 4020e52347bdSJani Nikula window. The default value is 64 megabytes. 4021e52347bdSJani Nikula resource_alignment= 4022e52347bdSJani Nikula Format: 402307d8d7e5SLogan Gunthorpe [<order of align>@]<pci_dev>[; ...] 4024e52347bdSJani Nikula Specifies alignment and device to reassign 402507d8d7e5SLogan Gunthorpe aligned memory resources. How to 402607d8d7e5SLogan Gunthorpe specify the device is described above. 4027e52347bdSJani Nikula If <order of align> is not specified, 4028e52347bdSJani Nikula PAGE_SIZE is used as alignment. 40293b1b1ce3SAlexey Kardashevskiy A PCI-PCI bridge can be specified if resource 4030e52347bdSJani Nikula windows need to be expanded. 4031e52347bdSJani Nikula To specify the alignment for several 4032e52347bdSJani Nikula instances of a device, the PCI vendor, 4033e52347bdSJani Nikula device, subvendor, and subdevice may be 40343b1b1ce3SAlexey Kardashevskiy specified, e.g., 12@pci:8086:9c22:103c:198f 40353b1b1ce3SAlexey Kardashevskiy for 4096-byte alignment. 4036e52347bdSJani Nikula ecrc= Enable/disable PCIe ECRC (transaction layer 4037e52347bdSJani Nikula end-to-end CRC checking). 4038e52347bdSJani Nikula bios: Use BIOS/firmware settings. This is the 4039e52347bdSJani Nikula the default. 4040e52347bdSJani Nikula off: Turn ECRC off 4041e52347bdSJani Nikula on: Turn ECRC on. 4042e52347bdSJani Nikula hpiosize=nn[KMG] The fixed amount of bus space which is 4043e52347bdSJani Nikula reserved for hotplug bridge's IO window. 4044e52347bdSJani Nikula Default size is 256 bytes. 4045d7b8a217SNicholas Johnson hpmmiosize=nn[KMG] The fixed amount of bus space which is 4046d7b8a217SNicholas Johnson reserved for hotplug bridge's MMIO window. 4047d7b8a217SNicholas Johnson Default size is 2 megabytes. 4048d7b8a217SNicholas Johnson hpmmioprefsize=nn[KMG] The fixed amount of bus space which is 4049d7b8a217SNicholas Johnson reserved for hotplug bridge's MMIO_PREF window. 4050d7b8a217SNicholas Johnson Default size is 2 megabytes. 4051e52347bdSJani Nikula hpmemsize=nn[KMG] The fixed amount of bus space which is 4052d7b8a217SNicholas Johnson reserved for hotplug bridge's MMIO and 4053d7b8a217SNicholas Johnson MMIO_PREF window. 4054e52347bdSJani Nikula Default size is 2 megabytes. 4055e52347bdSJani Nikula hpbussize=nn The minimum amount of additional bus numbers 4056e52347bdSJani Nikula reserved for buses below a hotplug bridge. 4057e52347bdSJani Nikula Default is 1. 4058e52347bdSJani Nikula realloc= Enable/disable reallocating PCI bridge resources 4059e52347bdSJani Nikula if allocations done by BIOS are too small to 4060e52347bdSJani Nikula accommodate resources required by all child 4061e52347bdSJani Nikula devices. 4062e52347bdSJani Nikula off: Turn realloc off 4063e52347bdSJani Nikula on: Turn realloc on 4064e52347bdSJani Nikula realloc same as realloc=on 4065e52347bdSJani Nikula noari do not use PCIe ARI. 4066cef74409SGil Kupfer noats [PCIE, Intel-IOMMU, AMD-IOMMU] 4067cef74409SGil Kupfer do not use PCIe ATS (and IOMMU device IOTLB). 4068e52347bdSJani Nikula pcie_scan_all Scan all possible PCIe devices. Otherwise we 4069e52347bdSJani Nikula only look for one device below a PCIe downstream 4070e52347bdSJani Nikula port. 4071f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= big_root_window Try to add a big 64bit memory window to the PCIe 4072f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= root complex on AMD CPUs. Some GFX hardware 4073f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= can resize a BAR to allow access to all VRAM. 4074f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= Adding the window is slightly risky (it may 4075f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= conflict with unreported devices), so this 4076f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= taints the kernel. 4077aaca43fdSLogan Gunthorpe disable_acs_redir=<pci_dev>[; ...] 4078aaca43fdSLogan Gunthorpe Specify one or more PCI devices (in the format 4079aaca43fdSLogan Gunthorpe specified above) separated by semicolons. 4080aaca43fdSLogan Gunthorpe Each device specified will have the PCI ACS 4081aaca43fdSLogan Gunthorpe redirect capabilities forced off which will 4082aaca43fdSLogan Gunthorpe allow P2P traffic between devices through 4083aaca43fdSLogan Gunthorpe bridges without forcing it upstream. Note: 4084aaca43fdSLogan Gunthorpe this removes isolation between devices and 4085aaca43fdSLogan Gunthorpe may put more devices in an IOMMU group. 4086fbfe07d4SSebastian Ott force_floating [S390] Force usage of floating interrupts. 408756271303SSebastian Ott nomio [S390] Do not use MIO instructions. 4088de267a7cSPierre Morel norid [S390] ignore the RID field and force use of 4089de267a7cSPierre Morel one PCI domain per PCI function 4090e52347bdSJani Nikula 4091e52347bdSJani Nikula pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 4092e52347bdSJani Nikula Management. 4093e52347bdSJani Nikula off Disable ASPM. 4094e52347bdSJani Nikula force Enable ASPM even on devices that claim not to support it. 4095e52347bdSJani Nikula WARNING: Forcing ASPM on may cause system lockups. 4096e52347bdSJani Nikula 40974c0fd764SBjorn Helgaas pcie_ports= [PCIE] PCIe port services handling: 40984c0fd764SBjorn Helgaas native Use native PCIe services (PME, AER, DPC, PCIe hotplug) 40994c0fd764SBjorn Helgaas even if the platform doesn't give the OS permission to 41004c0fd764SBjorn Helgaas use them. This may cause conflicts if the platform 41014c0fd764SBjorn Helgaas also tries to use these services. 410235a0b237SOlof Johansson dpc-native Use native PCIe service for DPC only. May 410335a0b237SOlof Johansson cause conflicts if firmware uses AER or DPC. 41044c0fd764SBjorn Helgaas compat Disable native PCIe services (PME, AER, DPC, PCIe 41054c0fd764SBjorn Helgaas hotplug). 4106e52347bdSJani Nikula 4107e52347bdSJani Nikula pcie_port_pm= [PCIE] PCIe port power management handling: 4108e52347bdSJani Nikula off Disable power management of all PCIe ports 4109e52347bdSJani Nikula force Forcibly enable power management of all PCIe ports 4110e52347bdSJani Nikula 4111e52347bdSJani Nikula pcie_pme= [PCIE,PM] Native PCIe PME signaling options: 4112e52347bdSJani Nikula nomsi Do not use MSI for native PCIe PME signaling (this makes 4113e52347bdSJani Nikula all PCIe root ports use INTx for all services). 4114e52347bdSJani Nikula 4115e52347bdSJani Nikula pcmv= [HW,PCMCIA] BadgePAD 4 4116e52347bdSJani Nikula 4117e52347bdSJani Nikula pd_ignore_unused 4118e52347bdSJani Nikula [PM] 4119e52347bdSJani Nikula Keep all power-domains already enabled by bootloader on, 4120e52347bdSJani Nikula even if no driver has claimed them. This is useful 4121e52347bdSJani Nikula for debug and development, but should not be 4122e52347bdSJani Nikula needed on a platform with proper driver support. 4123e52347bdSJani Nikula 4124e52347bdSJani Nikula pd. [PARIDE] 4125e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 4126e52347bdSJani Nikula 4127e52347bdSJani Nikula pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 4128e52347bdSJani Nikula boot time. 4129e52347bdSJani Nikula Format: { 0 | 1 } 4130e52347bdSJani Nikula See arch/parisc/kernel/pdc_chassis.c 4131e52347bdSJani Nikula 4132e52347bdSJani Nikula percpu_alloc= Select which percpu first chunk allocator to use. 4133e52347bdSJani Nikula Currently supported values are "embed" and "page". 4134e52347bdSJani Nikula Archs may support subset or none of the selections. 4135e52347bdSJani Nikula See comments in mm/percpu.c for details on each 4136e52347bdSJani Nikula allocator. This parameter is primarily for debugging 4137e52347bdSJani Nikula and performance comparison. 4138e52347bdSJani Nikula 4139e52347bdSJani Nikula pf. [PARIDE] 4140e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 4141e52347bdSJani Nikula 4142e52347bdSJani Nikula pg. [PARIDE] 4143e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 4144e52347bdSJani Nikula 4145e52347bdSJani Nikula pirq= [SMP,APIC] Manual mp-table setup 4146cb1aaebeSMauro Carvalho Chehab See Documentation/x86/i386/IO-APIC.rst. 4147e52347bdSJani Nikula 4148e52347bdSJani Nikula plip= [PPT,NET] Parallel port network link 4149e52347bdSJani Nikula Format: { parport<nr> | timid | 0 } 41503ba9b1b8STom Saeger See also Documentation/admin-guide/parport.rst. 4151e52347bdSJani Nikula 4152e52347bdSJani Nikula pmtmr= [X86] Manual setup of pmtmr I/O Port. 4153e52347bdSJani Nikula Override pmtimer IOPort with a hex value. 4154e52347bdSJani Nikula e.g. pmtmr=0x508 4155e52347bdSJani Nikula 4156db96a759SChen Yu pm_debug_messages [SUSPEND,KNL] 4157db96a759SChen Yu Enable suspend/resume debug messages during boot up. 4158db96a759SChen Yu 4159e52347bdSJani Nikula pnp.debug=1 [PNP] 4160e52347bdSJani Nikula Enable PNP debug messages (depends on the 4161e52347bdSJani Nikula CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time 4162e52347bdSJani Nikula via /sys/module/pnp/parameters/debug. We always show 4163e52347bdSJani Nikula current resource usage; turning this on also shows 4164e52347bdSJani Nikula possible settings and some assignment information. 4165e52347bdSJani Nikula 4166e52347bdSJani Nikula pnpacpi= [ACPI] 4167e52347bdSJani Nikula { off } 4168e52347bdSJani Nikula 4169e52347bdSJani Nikula pnpbios= [ISAPNP] 4170e52347bdSJani Nikula { on | off | curr | res | no-curr | no-res } 4171e52347bdSJani Nikula 4172e52347bdSJani Nikula pnp_reserve_irq= 4173e52347bdSJani Nikula [ISAPNP] Exclude IRQs for the autoconfiguration 4174e52347bdSJani Nikula 4175e52347bdSJani Nikula pnp_reserve_dma= 4176e52347bdSJani Nikula [ISAPNP] Exclude DMAs for the autoconfiguration 4177e52347bdSJani Nikula 4178e52347bdSJani Nikula pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 4179e52347bdSJani Nikula Ranges are in pairs (I/O port base and size). 4180e52347bdSJani Nikula 4181e52347bdSJani Nikula pnp_reserve_mem= 4182e52347bdSJani Nikula [ISAPNP] Exclude memory regions for the 4183e52347bdSJani Nikula autoconfiguration. 4184e52347bdSJani Nikula Ranges are in pairs (memory base and size). 4185e52347bdSJani Nikula 4186e52347bdSJani Nikula ports= [IP_VS_FTP] IPVS ftp helper module 4187e52347bdSJani Nikula Default is 21. 4188e52347bdSJani Nikula Up to 8 (IP_VS_APP_MAX_PORTS) ports 4189e52347bdSJani Nikula may be specified. 4190e52347bdSJani Nikula Format: <port>,<port>.... 4191e52347bdSJani Nikula 4192c3cbd075SBalbir Singh powersave=off [PPC] This option disables power saving features. 4193c3cbd075SBalbir Singh It specifically disables cpuidle and sets the 4194c3cbd075SBalbir Singh platform machine description specific power_save 4195c3cbd075SBalbir Singh function to NULL. On Idle the CPU just reduces 4196c3cbd075SBalbir Singh execution priority. 4197c3cbd075SBalbir Singh 4198e52347bdSJani Nikula ppc_strict_facility_enable 4199e52347bdSJani Nikula [PPC] This option catches any kernel floating point, 4200e52347bdSJani Nikula Altivec, VSX and SPE outside of regions specifically 4201e52347bdSJani Nikula allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). 4202e52347bdSJani Nikula There is some performance impact when enabling this. 4203e52347bdSJani Nikula 420407fd1761SCyril Bur ppc_tm= [PPC] 420507fd1761SCyril Bur Format: {"off"} 420607fd1761SCyril Bur Disable Hardware Transactional Memory 420707fd1761SCyril Bur 42086ef869e0SMichal Hocko preempt= [KNL] 42096ef869e0SMichal Hocko Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC 42106ef869e0SMichal Hocko none - Limited to cond_resched() calls 42116ef869e0SMichal Hocko voluntary - Limited to cond_resched() and might_sleep() calls 42126ef869e0SMichal Hocko full - Any section that isn't explicitly preempt disabled 42136ef869e0SMichal Hocko can be preempted anytime. 42146ef869e0SMichal Hocko 4215e52347bdSJani Nikula print-fatal-signals= 4216e52347bdSJani Nikula [KNL] debug: print fatal signals 4217e52347bdSJani Nikula 4218e52347bdSJani Nikula If enabled, warn about various signal handling 4219e52347bdSJani Nikula related application anomalies: too many signals, 4220e52347bdSJani Nikula too many POSIX.1 timers, fatal signals causing a 4221e52347bdSJani Nikula coredump - etc. 4222e52347bdSJani Nikula 4223e52347bdSJani Nikula If you hit the warning due to signal overflow, 4224e52347bdSJani Nikula you might want to try "ulimit -i unlimited". 4225e52347bdSJani Nikula 4226e52347bdSJani Nikula default: off. 4227e52347bdSJani Nikula 4228e52347bdSJani Nikula printk.always_kmsg_dump= 4229e52347bdSJani Nikula Trigger kmsg_dump for cases other than kernel oops or 4230e52347bdSJani Nikula panics 4231e52347bdSJani Nikula Format: <bool> (1/Y/y=enable, 0/N/n=disable) 4232e52347bdSJani Nikula default: disabled 4233e52347bdSJani Nikula 423410102a89SDmitry Safonov printk.console_no_auto_verbose= 423510102a89SDmitry Safonov Disable console loglevel raise on oops, panic 423610102a89SDmitry Safonov or lockdep-detected issues (only if lock debug is on). 423710102a89SDmitry Safonov With an exception to setups with low baudrate on 423810102a89SDmitry Safonov serial console, keeping this 0 is a good choice 423910102a89SDmitry Safonov in order to provide more debug information. 424010102a89SDmitry Safonov Format: <bool> 424110102a89SDmitry Safonov default: 0 (auto_verbose is enabled) 424210102a89SDmitry Safonov 4243e52347bdSJani Nikula printk.devkmsg={on,off,ratelimit} 4244e52347bdSJani Nikula Control writing to /dev/kmsg. 4245e52347bdSJani Nikula on - unlimited logging to /dev/kmsg from userspace 4246e52347bdSJani Nikula off - logging to /dev/kmsg disabled 4247e52347bdSJani Nikula ratelimit - ratelimit the logging 4248e52347bdSJani Nikula Default: ratelimit 4249e52347bdSJani Nikula 4250e52347bdSJani Nikula printk.time= Show timing data prefixed to each printk message line 4251e52347bdSJani Nikula Format: <bool> (1/Y/y=enable, 0/N/n=disable) 4252e52347bdSJani Nikula 4253e52347bdSJani Nikula processor.max_cstate= [HW,ACPI] 4254e52347bdSJani Nikula Limit processor to maximum C-state 4255e52347bdSJani Nikula max_cstate=9 overrides any DMI blacklist limit. 4256e52347bdSJani Nikula 4257e52347bdSJani Nikula processor.nocst [HW,ACPI] 4258e52347bdSJani Nikula Ignore the _CST method to determine C-states, 4259e52347bdSJani Nikula instead using the legacy FADT method 4260e52347bdSJani Nikula 4261e52347bdSJani Nikula profile= [KNL] Enable kernel profiling via /proc/profile 4262e7e61fc0SRandy Dunlap Format: [<profiletype>,]<number> 4263e7e61fc0SRandy Dunlap Param: <profiletype>: "schedule", "sleep", or "kvm" 4264e7e61fc0SRandy Dunlap [defaults to kernel profiling] 4265e52347bdSJani Nikula Param: "schedule" - profile schedule points. 4266e52347bdSJani Nikula Param: "sleep" - profile D-state sleeping (millisecs). 4267e52347bdSJani Nikula Requires CONFIG_SCHEDSTATS 4268e52347bdSJani Nikula Param: "kvm" - profile VM exits. 4269e7e61fc0SRandy Dunlap Param: <number> - step/bucket size as a power of 2 for 4270e7e61fc0SRandy Dunlap statistical time based profiling. 4271e52347bdSJani Nikula 42726b99e6e6SRandy Dunlap prompt_ramdisk= [RAM] [Deprecated] 4273e52347bdSJani Nikula 4274ecdc5d84SVasily Gorbik prot_virt= [S390] enable hosting protected virtual machines 4275ecdc5d84SVasily Gorbik isolated from the hypervisor (if hardware supports 4276ecdc5d84SVasily Gorbik that). 4277ecdc5d84SVasily Gorbik Format: <bool> 4278ecdc5d84SVasily Gorbik 4279e0c27447SJohannes Weiner psi= [KNL] Enable or disable pressure stall information 4280e0c27447SJohannes Weiner tracking. 4281e0c27447SJohannes Weiner Format: <bool> 4282e0c27447SJohannes Weiner 4283e52347bdSJani Nikula psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 4284e52347bdSJani Nikula probe for; one of (bare|imps|exps|lifebook|any). 4285e52347bdSJani Nikula psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 4286e52347bdSJani Nikula per second. 4287e52347bdSJani Nikula psmouse.resetafter= [HW,MOUSE] 4288e52347bdSJani Nikula Try to reset the device after so many bad packets 4289e52347bdSJani Nikula (0 = never). 4290e52347bdSJani Nikula psmouse.resolution= 4291e52347bdSJani Nikula [HW,MOUSE] Set desired mouse resolution, in dpi. 4292e52347bdSJani Nikula psmouse.smartscroll= 4293e52347bdSJani Nikula [HW,MOUSE] Controls Logitech smartscroll autorepeat. 4294e52347bdSJani Nikula 0 = disabled, 1 = enabled (default). 4295e52347bdSJani Nikula 4296e52347bdSJani Nikula pstore.backend= Specify the name of the pstore backend to use 4297e52347bdSJani Nikula 4298e52347bdSJani Nikula pt. [PARIDE] 4299e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 4300e52347bdSJani Nikula 4301be3a5b0eSRandy Dunlap pti= [X86-64] Control Page Table Isolation of user and 430201c9b17bSDave Hansen kernel address spaces. Disabling this feature 430301c9b17bSDave Hansen removes hardening, but improves performance of 430401c9b17bSDave Hansen system calls and interrupts. 430501c9b17bSDave Hansen 430601c9b17bSDave Hansen on - unconditionally enable 430701c9b17bSDave Hansen off - unconditionally disable 430801c9b17bSDave Hansen auto - kernel detects whether your CPU model is 430901c9b17bSDave Hansen vulnerable to issues that PTI mitigates 431001c9b17bSDave Hansen 431101c9b17bSDave Hansen Not specifying this option is equivalent to pti=auto. 431201c9b17bSDave Hansen 4313be3a5b0eSRandy Dunlap nopti [X86-64] 431401c9b17bSDave Hansen Equivalent to pti=off 431541f4c20bSBorislav Petkov 4316e52347bdSJani Nikula pty.legacy_count= 4317e52347bdSJani Nikula [KNL] Number of legacy pty's. Overwrites compiled-in 4318e52347bdSJani Nikula default number. 4319e52347bdSJani Nikula 4320e52347bdSJani Nikula quiet [KNL] Disable most log messages 4321e52347bdSJani Nikula 4322e52347bdSJani Nikula r128= [HW,DRM] 4323e52347bdSJani Nikula 4324e52347bdSJani Nikula raid= [HW,RAID] 4325e52347bdSJani Nikula See Documentation/admin-guide/md.rst. 4326e52347bdSJani Nikula 4327e52347bdSJani Nikula ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 4328e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/ramdisk.rst. 4329e52347bdSJani Nikula 43306b99e6e6SRandy Dunlap ramdisk_start= [RAM] RAM disk image start address 43316b99e6e6SRandy Dunlap 43329b254366SKees Cook random.trust_cpu={on,off} 43339b254366SKees Cook [KNL] Enable or disable trusting the use of the 43349b254366SKees Cook CPU's random number generator (if available) to 43359b254366SKees Cook fully seed the kernel's CRNG. Default is controlled 43369b254366SKees Cook by CONFIG_RANDOM_TRUST_CPU. 43379b254366SKees Cook 433839218ff4SKees Cook randomize_kstack_offset= 433939218ff4SKees Cook [KNL] Enable or disable kernel stack offset 434039218ff4SKees Cook randomization, which provides roughly 5 bits of 434139218ff4SKees Cook entropy, frustrating memory corruption attacks 434239218ff4SKees Cook that depend on stack address determinism or 434339218ff4SKees Cook cross-syscall address exposures. This is only 434439218ff4SKees Cook available on architectures that have defined 434539218ff4SKees Cook CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET. 434639218ff4SKees Cook Format: <bool> (1/Y/y=enable, 0/N/n=disable) 434739218ff4SKees Cook Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT. 434839218ff4SKees Cook 4349011d8261SBorislav Petkov ras=option[,option,...] [KNL] RAS-specific options 4350011d8261SBorislav Petkov 4351011d8261SBorislav Petkov cec_disable [X86] 4352011d8261SBorislav Petkov Disable the Correctable Errors Collector, 4353011d8261SBorislav Petkov see CONFIG_RAS_CEC help text. 4354011d8261SBorislav Petkov 4355e52347bdSJani Nikula rcu_nocbs= [KNL] 43563e70df91SPaul Gortmaker The argument is a cpu list, as described above. 4357e52347bdSJani Nikula 4358e52347bdSJani Nikula In kernels built with CONFIG_RCU_NOCB_CPU=y, set 4359e52347bdSJani Nikula the specified list of CPUs to be no-callback CPUs. 436077095901SPaul E. McKenney Invocation of these CPUs' RCU callbacks will be 436177095901SPaul E. McKenney offloaded to "rcuox/N" kthreads created for that 436277095901SPaul E. McKenney purpose, where "x" is "p" for RCU-preempt, and 436377095901SPaul E. McKenney "s" for RCU-sched, and "N" is the CPU number. 436477095901SPaul E. McKenney This reduces OS jitter on the offloaded CPUs, 436577095901SPaul E. McKenney which can be useful for HPC and real-time 436677095901SPaul E. McKenney workloads. It can also improve energy efficiency 436777095901SPaul E. McKenney for asymmetric multiprocessors. 4368e52347bdSJani Nikula 4369e52347bdSJani Nikula rcu_nocb_poll [KNL] 4370e52347bdSJani Nikula Rather than requiring that offloaded CPUs 4371e52347bdSJani Nikula (specified by rcu_nocbs= above) explicitly 4372e52347bdSJani Nikula awaken the corresponding "rcuoN" kthreads, 4373e52347bdSJani Nikula make these kthreads poll for callbacks. 4374e52347bdSJani Nikula This improves the real-time response for the 4375e52347bdSJani Nikula offloaded CPUs by relieving them of the need to 4376e52347bdSJani Nikula wake up the corresponding kthread, but degrades 4377e52347bdSJani Nikula energy efficiency by requiring that the kthreads 4378e52347bdSJani Nikula periodically wake up to do the polling. 4379e52347bdSJani Nikula 4380e52347bdSJani Nikula rcutree.blimit= [KNL] 4381e52347bdSJani Nikula Set maximum number of finished RCU callbacks to 4382e52347bdSJani Nikula process in one batch. 4383e52347bdSJani Nikula 4384e52347bdSJani Nikula rcutree.dump_tree= [KNL] 4385e52347bdSJani Nikula Dump the structure of the rcu_node combining tree 4386e52347bdSJani Nikula out at early boot. This is used for diagnostic 4387e52347bdSJani Nikula purposes, to verify correct tree setup. 4388e52347bdSJani Nikula 4389e52347bdSJani Nikula rcutree.gp_cleanup_delay= [KNL] 4390e52347bdSJani Nikula Set the number of jiffies to delay each step of 439190040c9eSPaul E. McKenney RCU grace-period cleanup. 4392e52347bdSJani Nikula 4393e52347bdSJani Nikula rcutree.gp_init_delay= [KNL] 4394e52347bdSJani Nikula Set the number of jiffies to delay each step of 439590040c9eSPaul E. McKenney RCU grace-period initialization. 4396e52347bdSJani Nikula 4397e52347bdSJani Nikula rcutree.gp_preinit_delay= [KNL] 4398e52347bdSJani Nikula Set the number of jiffies to delay each step of 4399e52347bdSJani Nikula RCU grace-period pre-initialization, that is, 4400e52347bdSJani Nikula the propagation of recent CPU-hotplug changes up 440190040c9eSPaul E. McKenney the rcu_node combining tree. 4402e52347bdSJani Nikula 440348d07c04SSebastian Andrzej Siewior rcutree.use_softirq= [KNL] 440448d07c04SSebastian Andrzej Siewior If set to zero, move all RCU_SOFTIRQ processing to 440548d07c04SSebastian Andrzej Siewior per-CPU rcuc kthreads. Defaults to a non-zero 440648d07c04SSebastian Andrzej Siewior value, meaning that RCU_SOFTIRQ is used by default. 440748d07c04SSebastian Andrzej Siewior Specify rcutree.use_softirq=0 to use rcuc kthreads. 440848d07c04SSebastian Andrzej Siewior 44098b9a0eccSScott Wood But note that CONFIG_PREEMPT_RT=y kernels disable 44108b9a0eccSScott Wood this kernel boot parameter, forcibly setting it 44118b9a0eccSScott Wood to zero. 44128b9a0eccSScott Wood 4413e52347bdSJani Nikula rcutree.rcu_fanout_exact= [KNL] 4414e52347bdSJani Nikula Disable autobalancing of the rcu_node combining 4415e52347bdSJani Nikula tree. This is used by rcutorture, and might 4416e52347bdSJani Nikula possibly be useful for architectures having high 4417e52347bdSJani Nikula cache-to-cache transfer latencies. 4418e52347bdSJani Nikula 4419e52347bdSJani Nikula rcutree.rcu_fanout_leaf= [KNL] 4420e52347bdSJani Nikula Change the number of CPUs assigned to each 4421e52347bdSJani Nikula leaf rcu_node structure. Useful for very 4422e52347bdSJani Nikula large systems, which will choose the value 64, 4423e52347bdSJani Nikula and for NUMA systems with large remote-access 4424e52347bdSJani Nikula latencies, which will choose a value aligned 4425e52347bdSJani Nikula with the appropriate hardware boundaries. 4426e52347bdSJani Nikula 442753c72b59SUladzislau Rezki (Sony) rcutree.rcu_min_cached_objs= [KNL] 442853c72b59SUladzislau Rezki (Sony) Minimum number of objects which are cached and 442953c72b59SUladzislau Rezki (Sony) maintained per one CPU. Object size is equal 443053c72b59SUladzislau Rezki (Sony) to PAGE_SIZE. The cache allows to reduce the 443153c72b59SUladzislau Rezki (Sony) pressure to page allocator, also it makes the 443253c72b59SUladzislau Rezki (Sony) whole algorithm to behave better in low memory 443353c72b59SUladzislau Rezki (Sony) condition. 443453c72b59SUladzislau Rezki (Sony) 4435d0bfa8b3SZhang Qiang rcutree.rcu_delay_page_cache_fill_msec= [KNL] 4436d0bfa8b3SZhang Qiang Set the page-cache refill delay (in milliseconds) 4437d0bfa8b3SZhang Qiang in response to low-memory conditions. The range 4438d0bfa8b3SZhang Qiang of permitted values is in the range 0:100000. 4439d0bfa8b3SZhang Qiang 4440e52347bdSJani Nikula rcutree.jiffies_till_first_fqs= [KNL] 4441e52347bdSJani Nikula Set delay from grace-period initialization to 4442e52347bdSJani Nikula first attempt to force quiescent states. 4443e52347bdSJani Nikula Units are jiffies, minimum value is zero, 4444e52347bdSJani Nikula and maximum value is HZ. 4445e52347bdSJani Nikula 4446e52347bdSJani Nikula rcutree.jiffies_till_next_fqs= [KNL] 4447e52347bdSJani Nikula Set delay between subsequent attempts to force 4448e52347bdSJani Nikula quiescent states. Units are jiffies, minimum 4449e52347bdSJani Nikula value is one, and maximum value is HZ. 4450e52347bdSJani Nikula 44511a4762b9SPaul E. McKenney rcutree.jiffies_till_sched_qs= [KNL] 44521a4762b9SPaul E. McKenney Set required age in jiffies for a 44531a4762b9SPaul E. McKenney given grace period before RCU starts 44541a4762b9SPaul E. McKenney soliciting quiescent-state help from 44551a4762b9SPaul E. McKenney rcu_note_context_switch() and cond_resched(). 44561a4762b9SPaul E. McKenney If not specified, the kernel will calculate 44571a4762b9SPaul E. McKenney a value based on the most recent settings 44581a4762b9SPaul E. McKenney of rcutree.jiffies_till_first_fqs 44591a4762b9SPaul E. McKenney and rcutree.jiffies_till_next_fqs. 44601a4762b9SPaul E. McKenney This calculated value may be viewed in 44611a4762b9SPaul E. McKenney rcutree.jiffies_to_sched_qs. Any attempt to set 44621a4762b9SPaul E. McKenney rcutree.jiffies_to_sched_qs will be cheerfully 44631a4762b9SPaul E. McKenney overwritten. 44641a4762b9SPaul E. McKenney 4465e52347bdSJani Nikula rcutree.kthread_prio= [KNL,BOOT] 4466e52347bdSJani Nikula Set the SCHED_FIFO priority of the RCU per-CPU 4467e52347bdSJani Nikula kthreads (rcuc/N). This value is also used for 4468e52347bdSJani Nikula the priority of the RCU boost threads (rcub/N) 4469e52347bdSJani Nikula and for the RCU grace-period kthreads (rcu_bh, 4470e52347bdSJani Nikula rcu_preempt, and rcu_sched). If RCU_BOOST is 4471e52347bdSJani Nikula set, valid values are 1-99 and the default is 1 4472e52347bdSJani Nikula (the least-favored priority). Otherwise, when 4473e52347bdSJani Nikula RCU_BOOST is not set, valid values are 0-99 and 4474e52347bdSJani Nikula the default is zero (non-realtime operation). 4475e52347bdSJani Nikula 4476f7c612b0SPaul E. McKenney rcutree.rcu_nocb_gp_stride= [KNL] 4477f7c612b0SPaul E. McKenney Set the number of NOCB callback kthreads in 4478f7c612b0SPaul E. McKenney each group, which defaults to the square root 4479f7c612b0SPaul E. McKenney of the number of CPUs. Larger numbers reduce 4480f7c612b0SPaul E. McKenney the wakeup overhead on the global grace-period 4481f7c612b0SPaul E. McKenney kthread, but increases that same overhead on 4482f7c612b0SPaul E. McKenney each group's NOCB grace-period kthread. 4483e52347bdSJani Nikula 4484e52347bdSJani Nikula rcutree.qhimark= [KNL] 4485e52347bdSJani Nikula Set threshold of queued RCU callbacks beyond which 4486e52347bdSJani Nikula batch limiting is disabled. 4487e52347bdSJani Nikula 4488e52347bdSJani Nikula rcutree.qlowmark= [KNL] 4489e52347bdSJani Nikula Set threshold of queued RCU callbacks below which 4490e52347bdSJani Nikula batch limiting is re-enabled. 4491e52347bdSJani Nikula 4492b2b00ddfSPaul E. McKenney rcutree.qovld= [KNL] 4493b2b00ddfSPaul E. McKenney Set threshold of queued RCU callbacks beyond which 4494b2b00ddfSPaul E. McKenney RCU's force-quiescent-state scan will aggressively 4495b2b00ddfSPaul E. McKenney enlist help from cond_resched() and sched IPIs to 4496b2b00ddfSPaul E. McKenney help CPUs more quickly reach quiescent states. 4497b2b00ddfSPaul E. McKenney Set to less than zero to make this be set based 4498b2b00ddfSPaul E. McKenney on rcutree.qhimark at boot time and to zero to 4499b2b00ddfSPaul E. McKenney disable more aggressive help enlistment. 4500b2b00ddfSPaul E. McKenney 4501e52347bdSJani Nikula rcutree.rcu_idle_gp_delay= [KNL] 4502e52347bdSJani Nikula Set wakeup interval for idle CPUs that have 4503e52347bdSJani Nikula RCU callbacks (RCU_FAST_NO_HZ=y). 4504e52347bdSJani Nikula 4505e3c50dfbSPaul E. McKenney rcutree.rcu_kick_kthreads= [KNL] 4506e3c50dfbSPaul E. McKenney Cause the grace-period kthread to get an extra 4507e3c50dfbSPaul E. McKenney wake_up() if it sleeps three times longer than 4508e3c50dfbSPaul E. McKenney it should at force-quiescent-state time. 4509e3c50dfbSPaul E. McKenney This wake_up() will be accompanied by a 4510e3c50dfbSPaul E. McKenney WARN_ONCE() splat and an ftrace_dump(). 4511e3c50dfbSPaul E. McKenney 45123d29aaf1SPaul E. McKenney rcutree.rcu_unlock_delay= [KNL] 45133d29aaf1SPaul E. McKenney In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, 45143d29aaf1SPaul E. McKenney this specifies an rcu_read_unlock()-time delay 45153d29aaf1SPaul E. McKenney in microseconds. This defaults to zero. 45163d29aaf1SPaul E. McKenney Larger delays increase the probability of 45173d29aaf1SPaul E. McKenney catching RCU pointer leaks, that is, buggy use 45183d29aaf1SPaul E. McKenney of RCU-protected pointers after the relevant 45193d29aaf1SPaul E. McKenney rcu_read_unlock() has completed. 45203d29aaf1SPaul E. McKenney 45212ccaff10SPaul E. McKenney rcutree.sysrq_rcu= [KNL] 45222ccaff10SPaul E. McKenney Commandeer a sysrq key to dump out Tree RCU's 45232ccaff10SPaul E. McKenney rcu_node tree with an eye towards determining 45242ccaff10SPaul E. McKenney why a new grace period has not yet started. 45252ccaff10SPaul E. McKenney 45264e88ec4aSPaul E. McKenney rcuscale.gp_async= [KNL] 4527881ed593SPaul E. McKenney Measure performance of asynchronous 4528881ed593SPaul E. McKenney grace-period primitives such as call_rcu(). 4529881ed593SPaul E. McKenney 45304e88ec4aSPaul E. McKenney rcuscale.gp_async_max= [KNL] 4531881ed593SPaul E. McKenney Specify the maximum number of outstanding 4532881ed593SPaul E. McKenney callbacks per writer thread. When a writer 4533881ed593SPaul E. McKenney thread exceeds this limit, it invokes the 4534881ed593SPaul E. McKenney corresponding flavor of rcu_barrier() to allow 4535881ed593SPaul E. McKenney previously posted callbacks to drain. 4536881ed593SPaul E. McKenney 45374e88ec4aSPaul E. McKenney rcuscale.gp_exp= [KNL] 4538e52347bdSJani Nikula Measure performance of expedited synchronous 4539e52347bdSJani Nikula grace-period primitives. 4540e52347bdSJani Nikula 45414e88ec4aSPaul E. McKenney rcuscale.holdoff= [KNL] 4542e52347bdSJani Nikula Set test-start holdoff period. The purpose of 4543e52347bdSJani Nikula this parameter is to delay the start of the 4544e52347bdSJani Nikula test until boot completes in order to avoid 4545e52347bdSJani Nikula interference. 4546e52347bdSJani Nikula 45474e88ec4aSPaul E. McKenney rcuscale.kfree_rcu_test= [KNL] 4548e6e78b00SJoel Fernandes (Google) Set to measure performance of kfree_rcu() flooding. 4549e6e78b00SJoel Fernandes (Google) 4550686fe1bfSUladzislau Rezki (Sony) rcuscale.kfree_rcu_test_double= [KNL] 4551686fe1bfSUladzislau Rezki (Sony) Test the double-argument variant of kfree_rcu(). 4552686fe1bfSUladzislau Rezki (Sony) If this parameter has the same value as 4553686fe1bfSUladzislau Rezki (Sony) rcuscale.kfree_rcu_test_single, both the single- 4554686fe1bfSUladzislau Rezki (Sony) and double-argument variants are tested. 4555686fe1bfSUladzislau Rezki (Sony) 4556686fe1bfSUladzislau Rezki (Sony) rcuscale.kfree_rcu_test_single= [KNL] 4557686fe1bfSUladzislau Rezki (Sony) Test the single-argument variant of kfree_rcu(). 4558686fe1bfSUladzislau Rezki (Sony) If this parameter has the same value as 4559686fe1bfSUladzislau Rezki (Sony) rcuscale.kfree_rcu_test_double, both the single- 4560686fe1bfSUladzislau Rezki (Sony) and double-argument variants are tested. 4561686fe1bfSUladzislau Rezki (Sony) 45624e88ec4aSPaul E. McKenney rcuscale.kfree_nthreads= [KNL] 4563e6e78b00SJoel Fernandes (Google) The number of threads running loops of kfree_rcu(). 4564e6e78b00SJoel Fernandes (Google) 45654e88ec4aSPaul E. McKenney rcuscale.kfree_alloc_num= [KNL] 4566e6e78b00SJoel Fernandes (Google) Number of allocations and frees done in an iteration. 4567e6e78b00SJoel Fernandes (Google) 45684e88ec4aSPaul E. McKenney rcuscale.kfree_loops= [KNL] 45694e88ec4aSPaul E. McKenney Number of loops doing rcuscale.kfree_alloc_num number 4570e6e78b00SJoel Fernandes (Google) of allocations and frees. 4571e6e78b00SJoel Fernandes (Google) 45724e88ec4aSPaul E. McKenney rcuscale.nreaders= [KNL] 4573e52347bdSJani Nikula Set number of RCU readers. The value -1 selects 4574e52347bdSJani Nikula N, where N is the number of CPUs. A value 4575e52347bdSJani Nikula "n" less than -1 selects N-n+1, where N is again 4576e52347bdSJani Nikula the number of CPUs. For example, -2 selects N 4577e52347bdSJani Nikula (the number of CPUs), -3 selects N+1, and so on. 4578e52347bdSJani Nikula A value of "n" less than or equal to -N selects 4579e52347bdSJani Nikula a single reader. 4580e52347bdSJani Nikula 45814e88ec4aSPaul E. McKenney rcuscale.nwriters= [KNL] 4582e52347bdSJani Nikula Set number of RCU writers. The values operate 45834e88ec4aSPaul E. McKenney the same as for rcuscale.nreaders. 4584e52347bdSJani Nikula N, where N is the number of CPUs 4585e52347bdSJani Nikula 45864e88ec4aSPaul E. McKenney rcuscale.perf_type= [KNL] 4587820687a7SPaul E. McKenney Specify the RCU implementation to test. 4588820687a7SPaul E. McKenney 45894e88ec4aSPaul E. McKenney rcuscale.shutdown= [KNL] 4590e52347bdSJani Nikula Shut the system down after performance tests 4591e52347bdSJani Nikula complete. This is useful for hands-off automated 4592e52347bdSJani Nikula testing. 4593e52347bdSJani Nikula 45944e88ec4aSPaul E. McKenney rcuscale.verbose= [KNL] 4595e52347bdSJani Nikula Enable additional printk() statements. 4596e52347bdSJani Nikula 45974e88ec4aSPaul E. McKenney rcuscale.writer_holdoff= [KNL] 4598820687a7SPaul E. McKenney Write-side holdoff between grace periods, 4599820687a7SPaul E. McKenney in microseconds. The default of zero says 4600820687a7SPaul E. McKenney no holdoff. 4601820687a7SPaul E. McKenney 4602e52347bdSJani Nikula rcutorture.fqs_duration= [KNL] 4603e52347bdSJani Nikula Set duration of force_quiescent_state bursts 4604e52347bdSJani Nikula in microseconds. 4605e52347bdSJani Nikula 4606e52347bdSJani Nikula rcutorture.fqs_holdoff= [KNL] 4607e52347bdSJani Nikula Set holdoff time within force_quiescent_state bursts 4608e52347bdSJani Nikula in microseconds. 4609e52347bdSJani Nikula 4610e52347bdSJani Nikula rcutorture.fqs_stutter= [KNL] 4611e52347bdSJani Nikula Set wait time between force_quiescent_state bursts 4612e52347bdSJani Nikula in seconds. 4613e52347bdSJani Nikula 4614ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress= [KNL] 4615ed8f6fb2SPaul E. McKenney Enable RCU grace-period forward-progress testing 4616ed8f6fb2SPaul E. McKenney for the types of RCU supporting this notion. 4617ed8f6fb2SPaul E. McKenney 4618ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_div= [KNL] 4619ed8f6fb2SPaul E. McKenney Specify the fraction of a CPU-stall-warning 4620ed8f6fb2SPaul E. McKenney period to do tight-loop forward-progress testing. 4621ed8f6fb2SPaul E. McKenney 4622ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_holdoff= [KNL] 4623ed8f6fb2SPaul E. McKenney Number of seconds to wait between successive 4624ed8f6fb2SPaul E. McKenney forward-progress tests. 4625ed8f6fb2SPaul E. McKenney 4626ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_need_resched= [KNL] 4627ed8f6fb2SPaul E. McKenney Enclose cond_resched() calls within checks for 4628ed8f6fb2SPaul E. McKenney need_resched() during tight-loop forward-progress 4629ed8f6fb2SPaul E. McKenney testing. 4630ed8f6fb2SPaul E. McKenney 4631e52347bdSJani Nikula rcutorture.gp_cond= [KNL] 4632e52347bdSJani Nikula Use conditional/asynchronous update-side 4633e52347bdSJani Nikula primitives, if available. 4634e52347bdSJani Nikula 4635e52347bdSJani Nikula rcutorture.gp_exp= [KNL] 4636e52347bdSJani Nikula Use expedited update-side primitives, if available. 4637e52347bdSJani Nikula 4638e52347bdSJani Nikula rcutorture.gp_normal= [KNL] 4639e52347bdSJani Nikula Use normal (non-expedited) asynchronous 4640e52347bdSJani Nikula update-side primitives, if available. 4641e52347bdSJani Nikula 4642e52347bdSJani Nikula rcutorture.gp_sync= [KNL] 4643e52347bdSJani Nikula Use normal (non-expedited) synchronous 4644e52347bdSJani Nikula update-side primitives, if available. If all 4645e52347bdSJani Nikula of rcutorture.gp_cond=, rcutorture.gp_exp=, 4646e52347bdSJani Nikula rcutorture.gp_normal=, and rcutorture.gp_sync= 4647e52347bdSJani Nikula are zero, rcutorture acts as if is interpreted 4648e52347bdSJani Nikula they are all non-zero. 4649e52347bdSJani Nikula 4650d6855142SPaul E. McKenney rcutorture.irqreader= [KNL] 4651d6855142SPaul E. McKenney Run RCU readers from irq handlers, or, more 4652d6855142SPaul E. McKenney accurately, from a timer handler. Not all RCU 4653d6855142SPaul E. McKenney flavors take kindly to this sort of thing. 4654d6855142SPaul E. McKenney 4655d6855142SPaul E. McKenney rcutorture.leakpointer= [KNL] 4656d6855142SPaul E. McKenney Leak an RCU-protected pointer out of the reader. 4657d6855142SPaul E. McKenney This can of course result in splats, and is 4658d6855142SPaul E. McKenney intended to test the ability of things like 4659d6855142SPaul E. McKenney CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect 4660d6855142SPaul E. McKenney such leaks. 4661d6855142SPaul E. McKenney 4662e52347bdSJani Nikula rcutorture.n_barrier_cbs= [KNL] 4663e52347bdSJani Nikula Set callbacks/threads for rcu_barrier() testing. 4664e52347bdSJani Nikula 4665e52347bdSJani Nikula rcutorture.nfakewriters= [KNL] 4666e52347bdSJani Nikula Set number of concurrent RCU writers. These just 4667e52347bdSJani Nikula stress RCU, they don't participate in the actual 4668e52347bdSJani Nikula test, hence the "fake". 4669e52347bdSJani Nikula 46702c4319bdSPaul E. McKenney rcutorture.nocbs_nthreads= [KNL] 46712c4319bdSPaul E. McKenney Set number of RCU callback-offload togglers. 46722c4319bdSPaul E. McKenney Zero (the default) disables toggling. 46732c4319bdSPaul E. McKenney 46742c4319bdSPaul E. McKenney rcutorture.nocbs_toggle= [KNL] 46752c4319bdSPaul E. McKenney Set the delay in milliseconds between successive 46762c4319bdSPaul E. McKenney callback-offload toggling attempts. 46772c4319bdSPaul E. McKenney 4678e52347bdSJani Nikula rcutorture.nreaders= [KNL] 4679e52347bdSJani Nikula Set number of RCU readers. The value -1 selects 4680e52347bdSJani Nikula N-1, where N is the number of CPUs. A value 4681e52347bdSJani Nikula "n" less than -1 selects N-n-2, where N is again 4682e52347bdSJani Nikula the number of CPUs. For example, -2 selects N 4683e52347bdSJani Nikula (the number of CPUs), -3 selects N+1, and so on. 4684e52347bdSJani Nikula 4685e52347bdSJani Nikula rcutorture.object_debug= [KNL] 4686e52347bdSJani Nikula Enable debug-object double-call_rcu() testing. 4687e52347bdSJani Nikula 4688e52347bdSJani Nikula rcutorture.onoff_holdoff= [KNL] 4689e52347bdSJani Nikula Set time (s) after boot for CPU-hotplug testing. 4690e52347bdSJani Nikula 4691e52347bdSJani Nikula rcutorture.onoff_interval= [KNL] 4692028be12bSPaul E. McKenney Set time (jiffies) between CPU-hotplug operations, 4693028be12bSPaul E. McKenney or zero to disable CPU-hotplug testing. 4694e52347bdSJani Nikula 46954a5f133cSPaul E. McKenney rcutorture.read_exit= [KNL] 46964a5f133cSPaul E. McKenney Set the number of read-then-exit kthreads used 46974a5f133cSPaul E. McKenney to test the interaction of RCU updaters and 46984a5f133cSPaul E. McKenney task-exit processing. 46994a5f133cSPaul E. McKenney 47004a5f133cSPaul E. McKenney rcutorture.read_exit_burst= [KNL] 47014a5f133cSPaul E. McKenney The number of times in a given read-then-exit 47024a5f133cSPaul E. McKenney episode that a set of read-then-exit kthreads 47034a5f133cSPaul E. McKenney is spawned. 47044a5f133cSPaul E. McKenney 47054a5f133cSPaul E. McKenney rcutorture.read_exit_delay= [KNL] 47064a5f133cSPaul E. McKenney The delay, in seconds, between successive 47074a5f133cSPaul E. McKenney read-then-exit testing episodes. 47084a5f133cSPaul E. McKenney 4709e52347bdSJani Nikula rcutorture.shuffle_interval= [KNL] 4710e52347bdSJani Nikula Set task-shuffle interval (s). Shuffling tasks 4711e52347bdSJani Nikula allows some CPUs to go into dyntick-idle mode 4712e52347bdSJani Nikula during the rcutorture test. 4713e52347bdSJani Nikula 4714e52347bdSJani Nikula rcutorture.shutdown_secs= [KNL] 4715e52347bdSJani Nikula Set time (s) after boot system shutdown. This 4716e52347bdSJani Nikula is useful for hands-off automated testing. 4717e52347bdSJani Nikula 4718e52347bdSJani Nikula rcutorture.stall_cpu= [KNL] 4719e52347bdSJani Nikula Duration of CPU stall (s) to test RCU CPU stall 4720e52347bdSJani Nikula warnings, zero to disable. 4721e52347bdSJani Nikula 472219a8ff95SPaul E. McKenney rcutorture.stall_cpu_block= [KNL] 472319a8ff95SPaul E. McKenney Sleep while stalling if set. This will result 472419a8ff95SPaul E. McKenney in warnings from preemptible RCU in addition 472519a8ff95SPaul E. McKenney to any other stall-related activity. 472619a8ff95SPaul E. McKenney 4727e52347bdSJani Nikula rcutorture.stall_cpu_holdoff= [KNL] 4728e52347bdSJani Nikula Time to wait (s) after boot before inducing stall. 4729e52347bdSJani Nikula 47302b1516e5SPaul E. McKenney rcutorture.stall_cpu_irqsoff= [KNL] 47312b1516e5SPaul E. McKenney Disable interrupts while stalling if set. 47322b1516e5SPaul E. McKenney 473355b2dcf5SPaul E. McKenney rcutorture.stall_gp_kthread= [KNL] 473455b2dcf5SPaul E. McKenney Duration (s) of forced sleep within RCU 473555b2dcf5SPaul E. McKenney grace-period kthread to test RCU CPU stall 473655b2dcf5SPaul E. McKenney warnings, zero to disable. If both stall_cpu 473755b2dcf5SPaul E. McKenney and stall_gp_kthread are specified, the 473855b2dcf5SPaul E. McKenney kthread is starved first, then the CPU. 473955b2dcf5SPaul E. McKenney 4740e52347bdSJani Nikula rcutorture.stat_interval= [KNL] 4741e52347bdSJani Nikula Time (s) between statistics printk()s. 4742e52347bdSJani Nikula 4743e52347bdSJani Nikula rcutorture.stutter= [KNL] 4744e52347bdSJani Nikula Time (s) to stutter testing, for example, specifying 4745e52347bdSJani Nikula five seconds causes the test to run for five seconds, 4746e52347bdSJani Nikula wait for five seconds, and so on. This tests RCU's 4747e52347bdSJani Nikula ability to transition abruptly to and from idle. 4748e52347bdSJani Nikula 4749e52347bdSJani Nikula rcutorture.test_boost= [KNL] 4750e52347bdSJani Nikula Test RCU priority boosting? 0=no, 1=maybe, 2=yes. 4751e52347bdSJani Nikula "Maybe" means test if the RCU implementation 4752e52347bdSJani Nikula under test support RCU priority boosting. 4753e52347bdSJani Nikula 4754e52347bdSJani Nikula rcutorture.test_boost_duration= [KNL] 4755e52347bdSJani Nikula Duration (s) of each individual boost test. 4756e52347bdSJani Nikula 4757e52347bdSJani Nikula rcutorture.test_boost_interval= [KNL] 4758e52347bdSJani Nikula Interval (s) between each boost test. 4759e52347bdSJani Nikula 4760e52347bdSJani Nikula rcutorture.test_no_idle_hz= [KNL] 4761e52347bdSJani Nikula Test RCU's dyntick-idle handling. See also the 4762e52347bdSJani Nikula rcutorture.shuffle_interval parameter. 4763e52347bdSJani Nikula 4764e52347bdSJani Nikula rcutorture.torture_type= [KNL] 4765e52347bdSJani Nikula Specify the RCU implementation to test. 4766e52347bdSJani Nikula 4767e52347bdSJani Nikula rcutorture.verbose= [KNL] 4768e52347bdSJani Nikula Enable additional printk() statements. 4769e52347bdSJani Nikula 4770cdc694b2SPaul E. McKenney rcupdate.rcu_cpu_stall_ftrace_dump= [KNL] 4771cdc694b2SPaul E. McKenney Dump ftrace buffer after reporting RCU CPU 4772cdc694b2SPaul E. McKenney stall warning. 4773cdc694b2SPaul E. McKenney 4774e52347bdSJani Nikula rcupdate.rcu_cpu_stall_suppress= [KNL] 4775e52347bdSJani Nikula Suppress RCU CPU stall warning messages. 4776e52347bdSJani Nikula 477758c53360SPaul E. McKenney rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL] 477858c53360SPaul E. McKenney Suppress RCU CPU stall warning messages and 477958c53360SPaul E. McKenney rcutorture writer stall warnings that occur 478058c53360SPaul E. McKenney during early boot, that is, during the time 478158c53360SPaul E. McKenney before the init task is spawned. 478258c53360SPaul E. McKenney 4783e52347bdSJani Nikula rcupdate.rcu_cpu_stall_timeout= [KNL] 4784e52347bdSJani Nikula Set timeout for RCU CPU stall warning messages. 4785e52347bdSJani Nikula 4786e52347bdSJani Nikula rcupdate.rcu_expedited= [KNL] 4787e52347bdSJani Nikula Use expedited grace-period primitives, for 4788e52347bdSJani Nikula example, synchronize_rcu_expedited() instead 4789e52347bdSJani Nikula of synchronize_rcu(). This reduces latency, 4790e52347bdSJani Nikula but can increase CPU utilization, degrade 4791e52347bdSJani Nikula real-time latency, and degrade energy efficiency. 4792e52347bdSJani Nikula No effect on CONFIG_TINY_RCU kernels. 4793e52347bdSJani Nikula 4794e52347bdSJani Nikula rcupdate.rcu_normal= [KNL] 4795e52347bdSJani Nikula Use only normal grace-period primitives, 4796e52347bdSJani Nikula for example, synchronize_rcu() instead of 4797e52347bdSJani Nikula synchronize_rcu_expedited(). This improves 4798e52347bdSJani Nikula real-time latency, CPU utilization, and 4799e52347bdSJani Nikula energy efficiency, but can expose users to 4800e52347bdSJani Nikula increased grace-period latency. This parameter 4801e52347bdSJani Nikula overrides rcupdate.rcu_expedited. No effect on 4802e52347bdSJani Nikula CONFIG_TINY_RCU kernels. 4803e52347bdSJani Nikula 4804e52347bdSJani Nikula rcupdate.rcu_normal_after_boot= [KNL] 4805e52347bdSJani Nikula Once boot has completed (that is, after 4806e52347bdSJani Nikula rcu_end_inkernel_boot() has been invoked), use 4807e52347bdSJani Nikula only normal grace-period primitives. No effect 4808e52347bdSJani Nikula on CONFIG_TINY_RCU kernels. 4809e52347bdSJani Nikula 481036221e10SJulia Cartwright But note that CONFIG_PREEMPT_RT=y kernels enables 481136221e10SJulia Cartwright this kernel boot parameter, forcibly setting 481236221e10SJulia Cartwright it to the value one, that is, converting any 481336221e10SJulia Cartwright post-boot attempt at an expedited RCU grace 481436221e10SJulia Cartwright period to instead use normal non-expedited 481536221e10SJulia Cartwright grace-period processing. 481636221e10SJulia Cartwright 4817b0afa0f0SPaul E. McKenney rcupdate.rcu_task_ipi_delay= [KNL] 4818b0afa0f0SPaul E. McKenney Set time in jiffies during which RCU tasks will 4819b0afa0f0SPaul E. McKenney avoid sending IPIs, starting with the beginning 4820b0afa0f0SPaul E. McKenney of a given grace period. Setting a large 4821b0afa0f0SPaul E. McKenney number avoids disturbing real-time workloads, 4822b0afa0f0SPaul E. McKenney but lengthens grace periods. 4823b0afa0f0SPaul E. McKenney 4824e52347bdSJani Nikula rcupdate.rcu_task_stall_timeout= [KNL] 4825e52347bdSJani Nikula Set timeout in jiffies for RCU task stall warning 4826e52347bdSJani Nikula messages. Disable with a value less than or equal 4827e52347bdSJani Nikula to zero. 4828e52347bdSJani Nikula 4829e52347bdSJani Nikula rcupdate.rcu_self_test= [KNL] 4830e52347bdSJani Nikula Run the RCU early boot self tests 4831e52347bdSJani Nikula 4832e52347bdSJani Nikula rdinit= [KNL] 4833e52347bdSJani Nikula Format: <full_path> 4834e52347bdSJani Nikula Run specified binary instead of /init from the ramdisk, 4835e52347bdSJani Nikula used for early userspace startup. See initrd. 4836e52347bdSJani Nikula 4837c49a0a80STom Lendacky rdrand= [X86] 4838c49a0a80STom Lendacky force - Override the decision by the kernel to hide the 4839c49a0a80STom Lendacky advertisement of RDRAND support (this affects 4840c49a0a80STom Lendacky certain AMD processors because of buggy BIOS 4841c49a0a80STom Lendacky support, specifically around the suspend/resume 4842c49a0a80STom Lendacky path). 4843c49a0a80STom Lendacky 48441d9807fcSTony Luck rdt= [HW,X86,RDT] 48451d9807fcSTony Luck Turn on/off individual RDT features. List is: 484631516de3SFenghua Yu cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp, 484731516de3SFenghua Yu mba. 48481d9807fcSTony Luck E.g. to turn on cmt and turn off mba use: 48491d9807fcSTony Luck rdt=cmt,!mba 48501d9807fcSTony Luck 4851e52347bdSJani Nikula reboot= [KNL] 4852e52347bdSJani Nikula Format (x86 or x86_64): 485312febc18SPaul Gortmaker [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \ 4854e52347bdSJani Nikula [[,]s[mp]#### \ 4855e52347bdSJani Nikula [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ 4856e52347bdSJani Nikula [[,]f[orce] 4857b287a25aSAaro Koskinen Where reboot_mode is one of warm (soft) or cold (hard) or gpio 4858b287a25aSAaro Koskinen (prefix with 'panic_' to set mode for panic 4859b287a25aSAaro Koskinen reboot only), 4860e52347bdSJani Nikula reboot_type is one of bios, acpi, kbd, triple, efi, or pci, 4861e52347bdSJani Nikula reboot_force is either force or not specified, 4862e52347bdSJani Nikula reboot_cpu is s[mp]#### with #### being the processor 4863e52347bdSJani Nikula to be used for rebooting. 4864e52347bdSJani Nikula 48651fbeb3a8SPaul E. McKenney refscale.holdoff= [KNL] 4866847dd70aSPaul E. McKenney Set test-start holdoff period. The purpose of 4867847dd70aSPaul E. McKenney this parameter is to delay the start of the 4868847dd70aSPaul E. McKenney test until boot completes in order to avoid 4869847dd70aSPaul E. McKenney interference. 4870847dd70aSPaul E. McKenney 48711fbeb3a8SPaul E. McKenney refscale.loops= [KNL] 4872847dd70aSPaul E. McKenney Set the number of loops over the synchronization 4873847dd70aSPaul E. McKenney primitive under test. Increasing this number 4874847dd70aSPaul E. McKenney reduces noise due to loop start/end overhead, 4875847dd70aSPaul E. McKenney but the default has already reduced the per-pass 4876847dd70aSPaul E. McKenney noise to a handful of picoseconds on ca. 2020 4877847dd70aSPaul E. McKenney x86 laptops. 4878847dd70aSPaul E. McKenney 48791fbeb3a8SPaul E. McKenney refscale.nreaders= [KNL] 4880847dd70aSPaul E. McKenney Set number of readers. The default value of -1 4881847dd70aSPaul E. McKenney selects N, where N is roughly 75% of the number 4882847dd70aSPaul E. McKenney of CPUs. A value of zero is an interesting choice. 4883847dd70aSPaul E. McKenney 48841fbeb3a8SPaul E. McKenney refscale.nruns= [KNL] 4885847dd70aSPaul E. McKenney Set number of runs, each of which is dumped onto 4886847dd70aSPaul E. McKenney the console log. 4887847dd70aSPaul E. McKenney 48881fbeb3a8SPaul E. McKenney refscale.readdelay= [KNL] 4889847dd70aSPaul E. McKenney Set the read-side critical-section duration, 4890847dd70aSPaul E. McKenney measured in microseconds. 4891847dd70aSPaul E. McKenney 48921fbeb3a8SPaul E. McKenney refscale.scale_type= [KNL] 48931fbeb3a8SPaul E. McKenney Specify the read-protection implementation to test. 48941fbeb3a8SPaul E. McKenney 48951fbeb3a8SPaul E. McKenney refscale.shutdown= [KNL] 4896847dd70aSPaul E. McKenney Shut down the system at the end of the performance 4897847dd70aSPaul E. McKenney test. This defaults to 1 (shut it down) when 48984e88ec4aSPaul E. McKenney refscale is built into the kernel and to 0 (leave 48994e88ec4aSPaul E. McKenney it running) when refscale is built as a module. 4900847dd70aSPaul E. McKenney 49011fbeb3a8SPaul E. McKenney refscale.verbose= [KNL] 4902847dd70aSPaul E. McKenney Enable additional printk() statements. 4903847dd70aSPaul E. McKenney 4904e76506f0SPaul E. McKenney refscale.verbose_batched= [KNL] 4905e76506f0SPaul E. McKenney Batch the additional printk() statements. If zero 4906e76506f0SPaul E. McKenney (the default) or negative, print everything. Otherwise, 4907e76506f0SPaul E. McKenney print every Nth verbose statement, where N is the value 4908e76506f0SPaul E. McKenney specified. 4909e76506f0SPaul E. McKenney 4910e52347bdSJani Nikula relax_domain_level= 4911e52347bdSJani Nikula [KNL, SMP] Set scheduler's default relax_domain_level. 4912da82c92fSMauro Carvalho Chehab See Documentation/admin-guide/cgroup-v1/cpusets.rst. 4913e52347bdSJani Nikula 4914ffd2e8dfSBjorn Helgaas reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory 4915ffd2e8dfSBjorn Helgaas Format: <base1>,<size1>[,<base2>,<size2>,...] 4916ffd2e8dfSBjorn Helgaas Reserve I/O ports or memory so the kernel won't use 4917ffd2e8dfSBjorn Helgaas them. If <base> is less than 0x10000, the region 4918ffd2e8dfSBjorn Helgaas is assumed to be I/O ports; otherwise it is memory. 4919e52347bdSJani Nikula 4920e52347bdSJani Nikula reservetop= [X86-32] 4921e52347bdSJani Nikula Format: nn[KMG] 4922e52347bdSJani Nikula Reserves a hole at the top of the kernel virtual 4923e52347bdSJani Nikula address space. 4924e52347bdSJani Nikula 4925e52347bdSJani Nikula reset_devices [KNL] Force drivers to reset the underlying device 4926e52347bdSJani Nikula during initialization. 4927e52347bdSJani Nikula 4928e52347bdSJani Nikula resume= [SWSUSP] 4929e52347bdSJani Nikula Specify the partition device for software suspend 4930e52347bdSJani Nikula Format: 4931e52347bdSJani Nikula {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>} 4932e52347bdSJani Nikula 4933e52347bdSJani Nikula resume_offset= [SWSUSP] 4934e52347bdSJani Nikula Specify the offset from the beginning of the partition 4935e52347bdSJani Nikula given by "resume=" at which the swap header is located, 4936e52347bdSJani Nikula in <PAGE_SIZE> units (needed only for swap files). 4937151f4e2bSMauro Carvalho Chehab See Documentation/power/swsusp-and-swap-files.rst 4938e52347bdSJani Nikula 4939e52347bdSJani Nikula resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to 4940e52347bdSJani Nikula read the resume files 4941e52347bdSJani Nikula 4942e52347bdSJani Nikula resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up. 4943e52347bdSJani Nikula Useful for devices that are detected asynchronously 4944e52347bdSJani Nikula (e.g. USB and MMC devices). 4945e52347bdSJani Nikula 4946e52347bdSJani Nikula hibernate= [HIBERNATION] 4947e52347bdSJani Nikula noresume Don't check if there's a hibernation image 4948e52347bdSJani Nikula present during boot. 4949e52347bdSJani Nikula nocompress Don't compress/decompress hibernation images. 4950e52347bdSJani Nikula no Disable hibernation and resume. 4951e52347bdSJani Nikula protect_image Turn on image protection during restoration 4952e52347bdSJani Nikula (that will set all pages holding image data 4953e52347bdSJani Nikula during restoration read-only). 4954e52347bdSJani Nikula 4955e52347bdSJani Nikula retain_initrd [RAM] Keep initrd memory after extraction 4956e52347bdSJani Nikula 4957e52347bdSJani Nikula rfkill.default_state= 4958e52347bdSJani Nikula 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, 4959e52347bdSJani Nikula etc. communication is blocked by default. 4960e52347bdSJani Nikula 1 Unblocked. 4961e52347bdSJani Nikula 4962e52347bdSJani Nikula rfkill.master_switch_mode= 4963e52347bdSJani Nikula 0 The "airplane mode" button does nothing. 4964e52347bdSJani Nikula 1 The "airplane mode" button toggles between everything 4965e52347bdSJani Nikula blocked and the previous configuration. 4966e52347bdSJani Nikula 2 The "airplane mode" button toggles between everything 4967e52347bdSJani Nikula blocked and everything unblocked. 4968e52347bdSJani Nikula 4969e52347bdSJani Nikula rhash_entries= [KNL,NET] 4970e52347bdSJani Nikula Set number of hash buckets for route cache 4971e52347bdSJani Nikula 4972e16fd002SGrzegorz Andrejczuk ring3mwait=disable 4973e16fd002SGrzegorz Andrejczuk [KNL] Disable ring 3 MONITOR/MWAIT feature on supported 4974e16fd002SGrzegorz Andrejczuk CPUs. 4975e16fd002SGrzegorz Andrejczuk 4976e52347bdSJani Nikula ro [KNL] Mount root device read-only on boot 4977e52347bdSJani Nikula 4978e52347bdSJani Nikula rodata= [KNL] 4979e52347bdSJani Nikula on Mark read-only kernel memory as read-only (default). 4980e52347bdSJani Nikula off Leave read-only kernel memory writable for debugging. 4981e52347bdSJani Nikula 4982e52347bdSJani Nikula rockchip.usb_uart 4983e52347bdSJani Nikula Enable the uart passthrough on the designated usb port 4984e52347bdSJani Nikula on Rockchip SoCs. When active, the signals of the 4985e52347bdSJani Nikula debug-uart get routed to the D+ and D- pins of the usb 4986e52347bdSJani Nikula port and the regular usb controller gets disabled. 4987e52347bdSJani Nikula 4988e52347bdSJani Nikula root= [KNL] Root filesystem 4989e52347bdSJani Nikula See name_to_dev_t comment in init/do_mounts.c. 4990e52347bdSJani Nikula 4991e52347bdSJani Nikula rootdelay= [KNL] Delay (in seconds) to pause before attempting to 4992e52347bdSJani Nikula mount the root filesystem 4993e52347bdSJani Nikula 4994e52347bdSJani Nikula rootflags= [KNL] Set root filesystem mount option string 4995e52347bdSJani Nikula 4996e52347bdSJani Nikula rootfstype= [KNL] Set root filesystem type 4997e52347bdSJani Nikula 4998e52347bdSJani Nikula rootwait [KNL] Wait (indefinitely) for root device to show up. 4999e52347bdSJani Nikula Useful for devices that are detected asynchronously 5000e52347bdSJani Nikula (e.g. USB and MMC devices). 5001e52347bdSJani Nikula 5002e52347bdSJani Nikula rproc_mem=nn[KMG][@address] 5003e52347bdSJani Nikula [KNL,ARM,CMA] Remoteproc physical memory block. 5004e52347bdSJani Nikula Memory area to be used by remote processor image, 5005e52347bdSJani Nikula managed by CMA. 5006e52347bdSJani Nikula 5007e52347bdSJani Nikula rw [KNL] Mount root device read-write on boot 5008e52347bdSJani Nikula 5009e52347bdSJani Nikula S [KNL] Run init in single mode 5010e52347bdSJani Nikula 5011e52347bdSJani Nikula s390_iommu= [HW,S390] 5012e52347bdSJani Nikula Set s390 IOTLB flushing mode 5013e52347bdSJani Nikula strict 5014e52347bdSJani Nikula With strict flushing every unmap operation will result in 5015e52347bdSJani Nikula an IOTLB flush. Default is lazy flushing before reuse, 5016e52347bdSJani Nikula which is faster. 5017e52347bdSJani Nikula 50186aefbf1cSNiklas Schnelle s390_iommu_aperture= [KNL,S390] 50196aefbf1cSNiklas Schnelle Specifies the size of the per device DMA address space 50206aefbf1cSNiklas Schnelle accessible through the DMA and IOMMU APIs as a decimal 50216aefbf1cSNiklas Schnelle factor of the size of main memory. 50226aefbf1cSNiklas Schnelle The default is 1 meaning that one can concurrently use 50236aefbf1cSNiklas Schnelle as many DMA addresses as physical memory is installed, 50246aefbf1cSNiklas Schnelle if supported by hardware, and thus map all of memory 50256aefbf1cSNiklas Schnelle once. With a value of 2 one can map all of memory twice 50266aefbf1cSNiklas Schnelle and so on. As a special case a factor of 0 imposes no 50276aefbf1cSNiklas Schnelle restrictions other than those given by hardware at the 50286aefbf1cSNiklas Schnelle cost of significant additional memory use for tables. 50296aefbf1cSNiklas Schnelle 5030e52347bdSJani Nikula sa1100ir [NET] 5031e52347bdSJani Nikula See drivers/net/irda/sa1100_ir.c. 5032e52347bdSJani Nikula 50339406415fSPeter Zijlstra sched_verbose [KNL] Enables verbose scheduler debug messages. 5034e52347bdSJani Nikula 5035e52347bdSJani Nikula schedstats= [KNL,X86] Enable or disable scheduled statistics. 5036e52347bdSJani Nikula Allowed values are enable and disable. This feature 5037e52347bdSJani Nikula incurs a small amount of overhead in the scheduler 5038e52347bdSJani Nikula but is useful for debugging and performance tuning. 5039e52347bdSJani Nikula 504005289b90SThara Gopinath sched_thermal_decay_shift= 504105289b90SThara Gopinath [KNL, SMP] Set a decay shift for scheduler thermal 504205289b90SThara Gopinath pressure signal. Thermal pressure signal follows the 504305289b90SThara Gopinath default decay period of other scheduler pelt 504405289b90SThara Gopinath signals(usually 32 ms but configurable). Setting 504505289b90SThara Gopinath sched_thermal_decay_shift will left shift the decay 504605289b90SThara Gopinath period for the thermal pressure signal by the shift 504705289b90SThara Gopinath value. 504805289b90SThara Gopinath i.e. with the default pelt decay period of 32 ms 504905289b90SThara Gopinath sched_thermal_decay_shift thermal pressure decay pr 505005289b90SThara Gopinath 1 64 ms 505105289b90SThara Gopinath 2 128 ms 505205289b90SThara Gopinath and so on. 505305289b90SThara Gopinath Format: integer between 0 and 10 505405289b90SThara Gopinath Default is 0. 505505289b90SThara Gopinath 5056e9d338a0SPaul E. McKenney scftorture.holdoff= [KNL] 5057e9d338a0SPaul E. McKenney Number of seconds to hold off before starting 5058e9d338a0SPaul E. McKenney test. Defaults to zero for module insertion and 5059e9d338a0SPaul E. McKenney to 10 seconds for built-in smp_call_function() 5060e9d338a0SPaul E. McKenney tests. 5061e9d338a0SPaul E. McKenney 5062e9d338a0SPaul E. McKenney scftorture.longwait= [KNL] 5063e9d338a0SPaul E. McKenney Request ridiculously long waits randomly selected 5064e9d338a0SPaul E. McKenney up to the chosen limit in seconds. Zero (the 5065e9d338a0SPaul E. McKenney default) disables this feature. Please note 5066e9d338a0SPaul E. McKenney that requesting even small non-zero numbers of 5067e9d338a0SPaul E. McKenney seconds can result in RCU CPU stall warnings, 5068e9d338a0SPaul E. McKenney softlockup complaints, and so on. 5069e9d338a0SPaul E. McKenney 5070e9d338a0SPaul E. McKenney scftorture.nthreads= [KNL] 5071e9d338a0SPaul E. McKenney Number of kthreads to spawn to invoke the 5072e9d338a0SPaul E. McKenney smp_call_function() family of functions. 5073e9d338a0SPaul E. McKenney The default of -1 specifies a number of kthreads 5074e9d338a0SPaul E. McKenney equal to the number of CPUs. 5075e9d338a0SPaul E. McKenney 5076e9d338a0SPaul E. McKenney scftorture.onoff_holdoff= [KNL] 5077e9d338a0SPaul E. McKenney Number seconds to wait after the start of the 5078e9d338a0SPaul E. McKenney test before initiating CPU-hotplug operations. 5079e9d338a0SPaul E. McKenney 5080e9d338a0SPaul E. McKenney scftorture.onoff_interval= [KNL] 5081e9d338a0SPaul E. McKenney Number seconds to wait between successive 5082e9d338a0SPaul E. McKenney CPU-hotplug operations. Specifying zero (which 5083e9d338a0SPaul E. McKenney is the default) disables CPU-hotplug operations. 5084e9d338a0SPaul E. McKenney 5085e9d338a0SPaul E. McKenney scftorture.shutdown_secs= [KNL] 5086e9d338a0SPaul E. McKenney The number of seconds following the start of the 5087e9d338a0SPaul E. McKenney test after which to shut down the system. The 5088e9d338a0SPaul E. McKenney default of zero avoids shutting down the system. 5089e9d338a0SPaul E. McKenney Non-zero values are useful for automated tests. 5090e9d338a0SPaul E. McKenney 5091e9d338a0SPaul E. McKenney scftorture.stat_interval= [KNL] 5092e9d338a0SPaul E. McKenney The number of seconds between outputting the 5093e9d338a0SPaul E. McKenney current test statistics to the console. A value 5094e9d338a0SPaul E. McKenney of zero disables statistics output. 5095e9d338a0SPaul E. McKenney 5096e9d338a0SPaul E. McKenney scftorture.stutter_cpus= [KNL] 5097e9d338a0SPaul E. McKenney The number of jiffies to wait between each change 5098e9d338a0SPaul E. McKenney to the set of CPUs under test. 5099e9d338a0SPaul E. McKenney 5100e9d338a0SPaul E. McKenney scftorture.use_cpus_read_lock= [KNL] 5101e9d338a0SPaul E. McKenney Use use_cpus_read_lock() instead of the default 5102e9d338a0SPaul E. McKenney preempt_disable() to disable CPU hotplug 5103e9d338a0SPaul E. McKenney while invoking one of the smp_call_function*() 5104e9d338a0SPaul E. McKenney functions. 5105e9d338a0SPaul E. McKenney 5106e9d338a0SPaul E. McKenney scftorture.verbose= [KNL] 5107e9d338a0SPaul E. McKenney Enable additional printk() statements. 5108e9d338a0SPaul E. McKenney 5109e9d338a0SPaul E. McKenney scftorture.weight_single= [KNL] 5110e9d338a0SPaul E. McKenney The probability weighting to use for the 5111e9d338a0SPaul E. McKenney smp_call_function_single() function with a zero 5112e9d338a0SPaul E. McKenney "wait" parameter. A value of -1 selects the 5113e9d338a0SPaul E. McKenney default if all other weights are -1. However, 5114e9d338a0SPaul E. McKenney if at least one weight has some other value, a 5115e9d338a0SPaul E. McKenney value of -1 will instead select a weight of zero. 5116e9d338a0SPaul E. McKenney 5117e9d338a0SPaul E. McKenney scftorture.weight_single_wait= [KNL] 5118e9d338a0SPaul E. McKenney The probability weighting to use for the 5119e9d338a0SPaul E. McKenney smp_call_function_single() function with a 5120e9d338a0SPaul E. McKenney non-zero "wait" parameter. See weight_single. 5121e9d338a0SPaul E. McKenney 5122e9d338a0SPaul E. McKenney scftorture.weight_many= [KNL] 5123e9d338a0SPaul E. McKenney The probability weighting to use for the 5124e9d338a0SPaul E. McKenney smp_call_function_many() function with a zero 5125e9d338a0SPaul E. McKenney "wait" parameter. See weight_single. 5126e9d338a0SPaul E. McKenney Note well that setting a high probability for 5127e9d338a0SPaul E. McKenney this weighting can place serious IPI load 5128e9d338a0SPaul E. McKenney on the system. 5129e9d338a0SPaul E. McKenney 5130e9d338a0SPaul E. McKenney scftorture.weight_many_wait= [KNL] 5131e9d338a0SPaul E. McKenney The probability weighting to use for the 5132e9d338a0SPaul E. McKenney smp_call_function_many() function with a 5133e9d338a0SPaul E. McKenney non-zero "wait" parameter. See weight_single 5134e9d338a0SPaul E. McKenney and weight_many. 5135e9d338a0SPaul E. McKenney 5136e9d338a0SPaul E. McKenney scftorture.weight_all= [KNL] 5137e9d338a0SPaul E. McKenney The probability weighting to use for the 5138e9d338a0SPaul E. McKenney smp_call_function_all() function with a zero 5139e9d338a0SPaul E. McKenney "wait" parameter. See weight_single and 5140e9d338a0SPaul E. McKenney weight_many. 5141e9d338a0SPaul E. McKenney 5142e9d338a0SPaul E. McKenney scftorture.weight_all_wait= [KNL] 5143e9d338a0SPaul E. McKenney The probability weighting to use for the 5144e9d338a0SPaul E. McKenney smp_call_function_all() function with a 5145e9d338a0SPaul E. McKenney non-zero "wait" parameter. See weight_single 5146e9d338a0SPaul E. McKenney and weight_many. 5147e9d338a0SPaul E. McKenney 5148e52347bdSJani Nikula skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate 5149e52347bdSJani Nikula xtime_lock contention on larger systems, and/or RCU lock 5150e52347bdSJani Nikula contention on all systems with CONFIG_MAXSMP set. 5151e52347bdSJani Nikula Format: { "0" | "1" } 5152e52347bdSJani Nikula 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1" 5153e52347bdSJani Nikula 1 -- enable. 5154e52347bdSJani Nikula Note: increases power consumption, thus should only be 5155e52347bdSJani Nikula enabled if running jitter sensitive (HPC/RT) workloads. 5156e52347bdSJani Nikula 515789a9684eSKees Cook security= [SECURITY] Choose a legacy "major" security module to 515889a9684eSKees Cook enable at boot. This has been deprecated by the 515989a9684eSKees Cook "lsm=" parameter. 5160e52347bdSJani Nikula 5161e52347bdSJani Nikula selinux= [SELINUX] Disable or enable SELinux at boot time. 5162e52347bdSJani Nikula Format: { "0" | "1" } 5163e52347bdSJani Nikula See security/selinux/Kconfig help text. 5164e52347bdSJani Nikula 0 -- disable. 5165e52347bdSJani Nikula 1 -- enable. 5166d41415ebSStephen Smalley Default value is 1. 5167e52347bdSJani Nikula 5168e52347bdSJani Nikula apparmor= [APPARMOR] Disable or enable AppArmor at boot time 5169e52347bdSJani Nikula Format: { "0" | "1" } 5170e52347bdSJani Nikula See security/apparmor/Kconfig help text 5171e52347bdSJani Nikula 0 -- disable. 5172e52347bdSJani Nikula 1 -- enable. 5173e52347bdSJani Nikula Default value is set via kernel config option. 5174e52347bdSJani Nikula 5175e52347bdSJani Nikula serialnumber [BUGS=X86-32] 5176e52347bdSJani Nikula 5177e52347bdSJani Nikula shapers= [NET] 5178e52347bdSJani Nikula Maximal number of shapers. 5179e52347bdSJani Nikula 5180e52347bdSJani Nikula simeth= [IA-64] 5181e52347bdSJani Nikula simscsi= 5182e52347bdSJani Nikula 5183e52347bdSJani Nikula slram= [HW,MTD] 5184e52347bdSJani Nikula 518582edd9d5SRafael Aquini slab_merge [MM] 518682edd9d5SRafael Aquini Enable merging of slabs with similar size when the 518782edd9d5SRafael Aquini kernel is built without CONFIG_SLAB_MERGE_DEFAULT. 518882edd9d5SRafael Aquini 5189e52347bdSJani Nikula slab_nomerge [MM] 5190e52347bdSJani Nikula Disable merging of slabs with similar size. May be 5191e52347bdSJani Nikula necessary if there is some reason to distinguish 51927660a6fdSKees Cook allocs to different slabs, especially in hardened 51937660a6fdSKees Cook environments where the risk of heap overflows and 51947660a6fdSKees Cook layout control by attackers can usually be 51957660a6fdSKees Cook frustrated by disabling merging. This will reduce 51967660a6fdSKees Cook most of the exposure of a heap attack to a single 51977660a6fdSKees Cook cache (risks via metadata attacks are mostly 51987660a6fdSKees Cook unchanged). Debug options disable merging on their 51997660a6fdSKees Cook own. 5200ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 5201e52347bdSJani Nikula 5202e52347bdSJani Nikula slab_max_order= [MM, SLAB] 5203e52347bdSJani Nikula Determines the maximum allowed order for slabs. 5204e52347bdSJani Nikula A high setting may cause OOMs due to memory 5205e52347bdSJani Nikula fragmentation. Defaults to 1 for systems with 5206e52347bdSJani Nikula more than 32MB of RAM, 0 otherwise. 5207e52347bdSJani Nikula 5208e17f1dfbSVlastimil Babka slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB] 5209e52347bdSJani Nikula Enabling slub_debug allows one to determine the 5210e52347bdSJani Nikula culprit if slab objects become corrupted. Enabling 5211e52347bdSJani Nikula slub_debug can create guard zones around objects and 5212e52347bdSJani Nikula may poison objects when not in use. Also tracks the 5213e52347bdSJani Nikula last alloc / free. For more information see 5214ad56b738SMike Rapoport Documentation/vm/slub.rst. 5215e52347bdSJani Nikula 5216e52347bdSJani Nikula slub_max_order= [MM, SLUB] 5217e52347bdSJani Nikula Determines the maximum allowed order for slabs. 5218e52347bdSJani Nikula A high setting may cause OOMs due to memory 5219e52347bdSJani Nikula fragmentation. For more information see 5220ad56b738SMike Rapoport Documentation/vm/slub.rst. 5221e52347bdSJani Nikula 5222e52347bdSJani Nikula slub_min_objects= [MM, SLUB] 5223e52347bdSJani Nikula The minimum number of objects per slab. SLUB will 5224e52347bdSJani Nikula increase the slab order up to slub_max_order to 5225e52347bdSJani Nikula generate a sufficiently large slab able to contain 5226e52347bdSJani Nikula the number of objects indicated. The higher the number 5227e52347bdSJani Nikula of objects the smaller the overhead of tracking slabs 5228e52347bdSJani Nikula and the less frequently locks need to be acquired. 5229ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 5230e52347bdSJani Nikula 5231e52347bdSJani Nikula slub_min_order= [MM, SLUB] 5232e52347bdSJani Nikula Determines the minimum page order for slabs. Must be 5233e52347bdSJani Nikula lower than slub_max_order. 5234ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 5235e52347bdSJani Nikula 523682edd9d5SRafael Aquini slub_merge [MM, SLUB] 523782edd9d5SRafael Aquini Same with slab_merge. 523882edd9d5SRafael Aquini 5239e52347bdSJani Nikula slub_nomerge [MM, SLUB] 5240e52347bdSJani Nikula Same with slab_nomerge. This is supported for legacy. 5241e52347bdSJani Nikula See slab_nomerge for more information. 5242e52347bdSJani Nikula 5243e52347bdSJani Nikula smart2= [HW] 5244e52347bdSJani Nikula Format: <io1>[,<io2>[,...,<io8>]] 5245e52347bdSJani Nikula 5246e52347bdSJani Nikula smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 5247e52347bdSJani Nikula smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 5248e52347bdSJani Nikula smsc-ircc2.ircc_sir= [HW] SIR base I/O port 5249e52347bdSJani Nikula smsc-ircc2.ircc_fir= [HW] FIR base I/O port 5250e52347bdSJani Nikula smsc-ircc2.ircc_irq= [HW] IRQ line 5251e52347bdSJani Nikula smsc-ircc2.ircc_dma= [HW] DMA channel 5252e52347bdSJani Nikula smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 5253e52347bdSJani Nikula 0: Toshiba Satellite 1800 (GP data pin select) 5254e52347bdSJani Nikula 1: Fast pin select (default) 5255e52347bdSJani Nikula 2: ATC IRMode 5256e52347bdSJani Nikula 5257e52347bdSJani Nikula smt [KNL,S390] Set the maximum number of threads (logical 5258e52347bdSJani Nikula CPUs) to use per physical CPU on systems capable of 5259e52347bdSJani Nikula symmetric multithreading (SMT). Will be capped to the 5260e52347bdSJani Nikula actual hardware limit. 5261e52347bdSJani Nikula Format: <integer> 5262e52347bdSJani Nikula Default: -1 (no limit) 5263e52347bdSJani Nikula 5264e52347bdSJani Nikula softlockup_panic= 5265e52347bdSJani Nikula [KNL] Should the soft-lockup detector generate panics. 5266f117955aSGuilherme G. Piccoli Format: 0 | 1 5267e52347bdSJani Nikula 5268f117955aSGuilherme G. Piccoli A value of 1 instructs the soft-lockup detector 52690a07bef6SGuilherme G. Piccoli to panic the machine when a soft-lockup occurs. It is 52700a07bef6SGuilherme G. Piccoli also controlled by the kernel.softlockup_panic sysctl 52710a07bef6SGuilherme G. Piccoli and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the 52720a07bef6SGuilherme G. Piccoli respective build-time switch to that functionality. 52733ce62385SBorislav Petkov 5274e52347bdSJani Nikula softlockup_all_cpu_backtrace= 5275e52347bdSJani Nikula [KNL] Should the soft-lockup detector generate 5276e52347bdSJani Nikula backtraces on all cpus. 5277f117955aSGuilherme G. Piccoli Format: 0 | 1 5278e52347bdSJani Nikula 5279e52347bdSJani Nikula sonypi.*= [HW] Sony Programmable I/O Control Device driver 52809e1cbedeSMauro Carvalho Chehab See Documentation/admin-guide/laptops/sonypi.rst 5281e52347bdSJani Nikula 5282da285121SDavid Woodhouse spectre_v2= [X86] Control mitigation of Spectre variant 2 5283da285121SDavid Woodhouse (indirect branch speculation) vulnerability. 5284fa1202efSThomas Gleixner The default operation protects the kernel from 5285fa1202efSThomas Gleixner user space attacks. 5286da285121SDavid Woodhouse 5287fa1202efSThomas Gleixner on - unconditionally enable, implies 5288fa1202efSThomas Gleixner spectre_v2_user=on 5289fa1202efSThomas Gleixner off - unconditionally disable, implies 5290fa1202efSThomas Gleixner spectre_v2_user=off 5291da285121SDavid Woodhouse auto - kernel detects whether your CPU model is 5292da285121SDavid Woodhouse vulnerable 5293da285121SDavid Woodhouse 5294da285121SDavid Woodhouse Selecting 'on' will, and 'auto' may, choose a 5295da285121SDavid Woodhouse mitigation method at run time according to the 5296da285121SDavid Woodhouse CPU, the available microcode, the setting of the 5297da285121SDavid Woodhouse CONFIG_RETPOLINE configuration option, and the 5298da285121SDavid Woodhouse compiler with which the kernel was built. 5299da285121SDavid Woodhouse 5300fa1202efSThomas Gleixner Selecting 'on' will also enable the mitigation 5301fa1202efSThomas Gleixner against user space to user space task attacks. 5302fa1202efSThomas Gleixner 5303fa1202efSThomas Gleixner Selecting 'off' will disable both the kernel and 5304fa1202efSThomas Gleixner the user space protections. 5305fa1202efSThomas Gleixner 5306da285121SDavid Woodhouse Specific mitigations can also be selected manually: 5307da285121SDavid Woodhouse 5308da285121SDavid Woodhouse retpoline - replace indirect branches 5309da285121SDavid Woodhouse retpoline,generic - google's original retpoline 5310da285121SDavid Woodhouse retpoline,amd - AMD-specific minimal thunk 5311da285121SDavid Woodhouse 5312da285121SDavid Woodhouse Not specifying this option is equivalent to 5313da285121SDavid Woodhouse spectre_v2=auto. 5314da285121SDavid Woodhouse 5315fa1202efSThomas Gleixner spectre_v2_user= 5316fa1202efSThomas Gleixner [X86] Control mitigation of Spectre variant 2 5317fa1202efSThomas Gleixner (indirect branch speculation) vulnerability between 5318fa1202efSThomas Gleixner user space tasks 5319fa1202efSThomas Gleixner 5320fa1202efSThomas Gleixner on - Unconditionally enable mitigations. Is 5321fa1202efSThomas Gleixner enforced by spectre_v2=on 5322fa1202efSThomas Gleixner 5323fa1202efSThomas Gleixner off - Unconditionally disable mitigations. Is 5324fa1202efSThomas Gleixner enforced by spectre_v2=off 5325fa1202efSThomas Gleixner 53267cc765a6SThomas Gleixner prctl - Indirect branch speculation is enabled, 53277cc765a6SThomas Gleixner but mitigation can be enabled via prctl 53287cc765a6SThomas Gleixner per thread. The mitigation control state 53297cc765a6SThomas Gleixner is inherited on fork. 53307cc765a6SThomas Gleixner 533155a97402SThomas Gleixner prctl,ibpb 533255a97402SThomas Gleixner - Like "prctl" above, but only STIBP is 533355a97402SThomas Gleixner controlled per thread. IBPB is issued 533455a97402SThomas Gleixner always when switching between different user 533555a97402SThomas Gleixner space processes. 533655a97402SThomas Gleixner 53376b3e64c2SThomas Gleixner seccomp 53386b3e64c2SThomas Gleixner - Same as "prctl" above, but all seccomp 53396b3e64c2SThomas Gleixner threads will enable the mitigation unless 53406b3e64c2SThomas Gleixner they explicitly opt out. 53416b3e64c2SThomas Gleixner 534255a97402SThomas Gleixner seccomp,ibpb 534355a97402SThomas Gleixner - Like "seccomp" above, but only STIBP is 534455a97402SThomas Gleixner controlled per thread. IBPB is issued 534555a97402SThomas Gleixner always when switching between different 534655a97402SThomas Gleixner user space processes. 534755a97402SThomas Gleixner 5348fa1202efSThomas Gleixner auto - Kernel selects the mitigation depending on 5349fa1202efSThomas Gleixner the available CPU features and vulnerability. 53506b3e64c2SThomas Gleixner 53512f46993dSAndrea Arcangeli Default mitigation: "prctl" 5352fa1202efSThomas Gleixner 5353fa1202efSThomas Gleixner Not specifying this option is equivalent to 5354fa1202efSThomas Gleixner spectre_v2_user=auto. 5355fa1202efSThomas Gleixner 535624f7fc83SKonrad Rzeszutek Wilk spec_store_bypass_disable= 535724f7fc83SKonrad Rzeszutek Wilk [HW] Control Speculative Store Bypass (SSB) Disable mitigation 535824f7fc83SKonrad Rzeszutek Wilk (Speculative Store Bypass vulnerability) 535924f7fc83SKonrad Rzeszutek Wilk 536024f7fc83SKonrad Rzeszutek Wilk Certain CPUs are vulnerable to an exploit against a 536124f7fc83SKonrad Rzeszutek Wilk a common industry wide performance optimization known 536224f7fc83SKonrad Rzeszutek Wilk as "Speculative Store Bypass" in which recent stores 536324f7fc83SKonrad Rzeszutek Wilk to the same memory location may not be observed by 536424f7fc83SKonrad Rzeszutek Wilk later loads during speculative execution. The idea 536524f7fc83SKonrad Rzeszutek Wilk is that such stores are unlikely and that they can 536624f7fc83SKonrad Rzeszutek Wilk be detected prior to instruction retirement at the 536724f7fc83SKonrad Rzeszutek Wilk end of a particular speculation execution window. 536824f7fc83SKonrad Rzeszutek Wilk 536924f7fc83SKonrad Rzeszutek Wilk In vulnerable processors, the speculatively forwarded 537024f7fc83SKonrad Rzeszutek Wilk store can be used in a cache side channel attack, for 537124f7fc83SKonrad Rzeszutek Wilk example to read memory to which the attacker does not 537224f7fc83SKonrad Rzeszutek Wilk directly have access (e.g. inside sandboxed code). 537324f7fc83SKonrad Rzeszutek Wilk 537424f7fc83SKonrad Rzeszutek Wilk This parameter controls whether the Speculative Store 537524f7fc83SKonrad Rzeszutek Wilk Bypass optimization is used. 537624f7fc83SKonrad Rzeszutek Wilk 53776b4c1360SMichael Ellerman On x86 the options are: 53786b4c1360SMichael Ellerman 537924f7fc83SKonrad Rzeszutek Wilk on - Unconditionally disable Speculative Store Bypass 538024f7fc83SKonrad Rzeszutek Wilk off - Unconditionally enable Speculative Store Bypass 538124f7fc83SKonrad Rzeszutek Wilk auto - Kernel detects whether the CPU model contains an 538224f7fc83SKonrad Rzeszutek Wilk implementation of Speculative Store Bypass and 5383f21b53b2SKees Cook picks the most appropriate mitigation. If the 5384f21b53b2SKees Cook CPU is not vulnerable, "off" is selected. If the 5385f21b53b2SKees Cook CPU is vulnerable the default mitigation is 5386f21b53b2SKees Cook architecture and Kconfig dependent. See below. 5387a73ec77eSThomas Gleixner prctl - Control Speculative Store Bypass per thread 5388a73ec77eSThomas Gleixner via prctl. Speculative Store Bypass is enabled 5389a73ec77eSThomas Gleixner for a process by default. The state of the control 5390a73ec77eSThomas Gleixner is inherited on fork. 5391f21b53b2SKees Cook seccomp - Same as "prctl" above, but all seccomp threads 5392f21b53b2SKees Cook will disable SSB unless they explicitly opt out. 539324f7fc83SKonrad Rzeszutek Wilk 5394f21b53b2SKees Cook Default mitigations: 53952f46993dSAndrea Arcangeli X86: "prctl" 5396f21b53b2SKees Cook 53976b4c1360SMichael Ellerman On powerpc the options are: 53986b4c1360SMichael Ellerman 53996b4c1360SMichael Ellerman on,auto - On Power8 and Power9 insert a store-forwarding 54006b4c1360SMichael Ellerman barrier on kernel entry and exit. On Power7 54016b4c1360SMichael Ellerman perform a software flush on kernel entry and 54026b4c1360SMichael Ellerman exit. 54036b4c1360SMichael Ellerman off - No action. 54046b4c1360SMichael Ellerman 54056b4c1360SMichael Ellerman Not specifying this option is equivalent to 54066b4c1360SMichael Ellerman spec_store_bypass_disable=auto. 54076b4c1360SMichael Ellerman 5408e52347bdSJani Nikula spia_io_base= [HW,MTD] 5409e52347bdSJani Nikula spia_fio_base= 5410e52347bdSJani Nikula spia_pedr= 5411e52347bdSJani Nikula spia_peddr= 5412e52347bdSJani Nikula 54136650cdd9SPeter Zijlstra (Intel) split_lock_detect= 5414ebca1770SFenghua Yu [X86] Enable split lock detection or bus lock detection 54156650cdd9SPeter Zijlstra (Intel) 54166650cdd9SPeter Zijlstra (Intel) When enabled (and if hardware support is present), atomic 54176650cdd9SPeter Zijlstra (Intel) instructions that access data across cache line 5418ebca1770SFenghua Yu boundaries will result in an alignment check exception 5419ebca1770SFenghua Yu for split lock detection or a debug exception for 5420ebca1770SFenghua Yu bus lock detection. 54216650cdd9SPeter Zijlstra (Intel) 54226650cdd9SPeter Zijlstra (Intel) off - not enabled 54236650cdd9SPeter Zijlstra (Intel) 5424ebca1770SFenghua Yu warn - the kernel will emit rate-limited warnings 54256650cdd9SPeter Zijlstra (Intel) about applications triggering the #AC 5426ebca1770SFenghua Yu exception or the #DB exception. This mode is 5427ebca1770SFenghua Yu the default on CPUs that support split lock 5428ebca1770SFenghua Yu detection or bus lock detection. Default 5429ebca1770SFenghua Yu behavior is by #AC if both features are 5430ebca1770SFenghua Yu enabled in hardware. 54316650cdd9SPeter Zijlstra (Intel) 54326650cdd9SPeter Zijlstra (Intel) fatal - the kernel will send SIGBUS to applications 5433ebca1770SFenghua Yu that trigger the #AC exception or the #DB 5434ebca1770SFenghua Yu exception. Default behavior is by #AC if 5435ebca1770SFenghua Yu both features are enabled in hardware. 54366650cdd9SPeter Zijlstra (Intel) 54379d839c28SFenghua Yu ratelimit:N - 54389d839c28SFenghua Yu Set system wide rate limit to N bus locks 54399d839c28SFenghua Yu per second for bus lock detection. 54409d839c28SFenghua Yu 0 < N <= 1000. 54419d839c28SFenghua Yu 54429d839c28SFenghua Yu N/A for split lock detection. 54439d839c28SFenghua Yu 54449d839c28SFenghua Yu 54456650cdd9SPeter Zijlstra (Intel) If an #AC exception is hit in the kernel or in 54466650cdd9SPeter Zijlstra (Intel) firmware (i.e. not while executing in user mode) 54476650cdd9SPeter Zijlstra (Intel) the kernel will oops in either "warn" or "fatal" 54486650cdd9SPeter Zijlstra (Intel) mode. 54496650cdd9SPeter Zijlstra (Intel) 5450ebca1770SFenghua Yu #DB exception for bus lock is triggered only when 5451ebca1770SFenghua Yu CPL > 0. 5452ebca1770SFenghua Yu 54537e5b3c26SMark Gross srbds= [X86,INTEL] 54547e5b3c26SMark Gross Control the Special Register Buffer Data Sampling 54557e5b3c26SMark Gross (SRBDS) mitigation. 54567e5b3c26SMark Gross 54577e5b3c26SMark Gross Certain CPUs are vulnerable to an MDS-like 54587e5b3c26SMark Gross exploit which can leak bits from the random 54597e5b3c26SMark Gross number generator. 54607e5b3c26SMark Gross 54617e5b3c26SMark Gross By default, this issue is mitigated by 54627e5b3c26SMark Gross microcode. However, the microcode fix can cause 54637e5b3c26SMark Gross the RDRAND and RDSEED instructions to become 54647e5b3c26SMark Gross much slower. Among other effects, this will 54657e5b3c26SMark Gross result in reduced throughput from /dev/urandom. 54667e5b3c26SMark Gross 54677e5b3c26SMark Gross The microcode mitigation can be disabled with 54687e5b3c26SMark Gross the following option: 54697e5b3c26SMark Gross 54707e5b3c26SMark Gross off: Disable mitigation and remove 54717e5b3c26SMark Gross performance impact to RDRAND and RDSEED 54727e5b3c26SMark Gross 5473c350c008SPaul E. McKenney srcutree.counter_wrap_check [KNL] 5474c350c008SPaul E. McKenney Specifies how frequently to check for 5475c350c008SPaul E. McKenney grace-period sequence counter wrap for the 5476c350c008SPaul E. McKenney srcu_data structure's ->srcu_gp_seq_needed field. 5477c350c008SPaul E. McKenney The greater the number of bits set in this kernel 5478c350c008SPaul E. McKenney parameter, the less frequently counter wrap will 5479c350c008SPaul E. McKenney be checked for. Note that the bottom two bits 5480c350c008SPaul E. McKenney are ignored. 5481c350c008SPaul E. McKenney 548222607d66SPaul E. McKenney srcutree.exp_holdoff [KNL] 548322607d66SPaul E. McKenney Specifies how many nanoseconds must elapse 548422607d66SPaul E. McKenney since the end of the last SRCU grace period for 548522607d66SPaul E. McKenney a given srcu_struct until the next normal SRCU 548622607d66SPaul E. McKenney grace period will be considered for automatic 548722607d66SPaul E. McKenney expediting. Set to zero to disable automatic 548822607d66SPaul E. McKenney expediting. 548922607d66SPaul E. McKenney 5490a43ae4dfSMarc Zyngier ssbd= [ARM64,HW] 5491a43ae4dfSMarc Zyngier Speculative Store Bypass Disable control 5492a43ae4dfSMarc Zyngier 5493a43ae4dfSMarc Zyngier On CPUs that are vulnerable to the Speculative 5494a43ae4dfSMarc Zyngier Store Bypass vulnerability and offer a 5495a43ae4dfSMarc Zyngier firmware based mitigation, this parameter 5496a43ae4dfSMarc Zyngier indicates how the mitigation should be used: 5497a43ae4dfSMarc Zyngier 5498a43ae4dfSMarc Zyngier force-on: Unconditionally enable mitigation for 5499a43ae4dfSMarc Zyngier for both kernel and userspace 5500a43ae4dfSMarc Zyngier force-off: Unconditionally disable mitigation for 5501a43ae4dfSMarc Zyngier for both kernel and userspace 5502a43ae4dfSMarc Zyngier kernel: Always enable mitigation in the 5503a43ae4dfSMarc Zyngier kernel, and offer a prctl interface 5504a43ae4dfSMarc Zyngier to allow userspace to register its 5505a43ae4dfSMarc Zyngier interest in being mitigated too. 5506a43ae4dfSMarc Zyngier 55071be7107fSHugh Dickins stack_guard_gap= [MM] 55081be7107fSHugh Dickins override the default stack gap protection. The value 55091be7107fSHugh Dickins is in page units and it defines how many pages prior 55101be7107fSHugh Dickins to (for stacks growing down) resp. after (for stacks 55111be7107fSHugh Dickins growing up) the main stack are reserved for no other 55121be7107fSHugh Dickins mapping. Default value is 256 pages. 55131be7107fSHugh Dickins 5514e1fdc403SVijayanand Jitta stack_depot_disable= [KNL] 5515e1fdc403SVijayanand Jitta Setting this to true through kernel command line will 5516e1fdc403SVijayanand Jitta disable the stack depot thereby saving the static memory 5517e1fdc403SVijayanand Jitta consumed by the stack hash table. By default this is set 5518e1fdc403SVijayanand Jitta to false. 5519e1fdc403SVijayanand Jitta 5520e52347bdSJani Nikula stacktrace [FTRACE] 5521e52347bdSJani Nikula Enabled the stack tracer on boot up. 5522e52347bdSJani Nikula 5523e52347bdSJani Nikula stacktrace_filter=[function-list] 5524e52347bdSJani Nikula [FTRACE] Limit the functions that the stack tracer 552525942e5eSRandy Dunlap will trace at boot up. function-list is a comma-separated 5526e52347bdSJani Nikula list of functions. This list can be changed at run 5527e52347bdSJani Nikula time by the stack_trace_filter file in the debugfs 5528e52347bdSJani Nikula tracing directory. Note, this enables stack tracing 5529e52347bdSJani Nikula and the stacktrace above is not needed. 5530e52347bdSJani Nikula 5531e52347bdSJani Nikula sti= [PARISC,HW] 5532e52347bdSJani Nikula Format: <num> 5533e52347bdSJani Nikula Set the STI (builtin display/keyboard on the HP-PARISC 5534e52347bdSJani Nikula machines) console (graphic card) which should be used 5535e52347bdSJani Nikula as the initial boot-console. 5536e52347bdSJani Nikula See also comment in drivers/video/console/sticore.c. 5537e52347bdSJani Nikula 5538e52347bdSJani Nikula sti_font= [HW] 5539e52347bdSJani Nikula See comment in drivers/video/console/sticore.c. 5540e52347bdSJani Nikula 5541e52347bdSJani Nikula stifb= [HW] 5542e52347bdSJani Nikula Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 5543e52347bdSJani Nikula 55443aac3ebeSThomas Gleixner strict_sas_size= 55453aac3ebeSThomas Gleixner [X86] 55463aac3ebeSThomas Gleixner Format: <bool> 55473aac3ebeSThomas Gleixner Enable or disable strict sigaltstack size checks 55483aac3ebeSThomas Gleixner against the required signal frame size which 55493aac3ebeSThomas Gleixner depends on the supported FPU features. This can 55503aac3ebeSThomas Gleixner be used to filter out binaries which have 55513aac3ebeSThomas Gleixner not yet been made aware of AT_MINSIGSTKSZ. 55523aac3ebeSThomas Gleixner 5553e52347bdSJani Nikula sunrpc.min_resvport= 5554e52347bdSJani Nikula sunrpc.max_resvport= 5555e52347bdSJani Nikula [NFS,SUNRPC] 5556e52347bdSJani Nikula SunRPC servers often require that client requests 5557e52347bdSJani Nikula originate from a privileged port (i.e. a port in the 5558e52347bdSJani Nikula range 0 < portnr < 1024). 5559e52347bdSJani Nikula An administrator who wishes to reserve some of these 5560e52347bdSJani Nikula ports for other uses may adjust the range that the 5561e52347bdSJani Nikula kernel's sunrpc client considers to be privileged 5562e52347bdSJani Nikula using these two parameters to set the minimum and 5563e52347bdSJani Nikula maximum port values. 5564e52347bdSJani Nikula 5565e52347bdSJani Nikula sunrpc.svc_rpc_per_connection_limit= 5566e52347bdSJani Nikula [NFS,SUNRPC] 5567e52347bdSJani Nikula Limit the number of requests that the server will 5568e52347bdSJani Nikula process in parallel from a single connection. 5569e52347bdSJani Nikula The default value is 0 (no limit). 5570e52347bdSJani Nikula 5571e52347bdSJani Nikula sunrpc.pool_mode= 5572e52347bdSJani Nikula [NFS] 5573e52347bdSJani Nikula Control how the NFS server code allocates CPUs to 5574e52347bdSJani Nikula service thread pools. Depending on how many NICs 5575e52347bdSJani Nikula you have and where their interrupts are bound, this 5576e52347bdSJani Nikula option will affect which CPUs will do NFS serving. 5577e52347bdSJani Nikula Note: this parameter cannot be changed while the 5578e52347bdSJani Nikula NFS server is running. 5579e52347bdSJani Nikula 5580e52347bdSJani Nikula auto the server chooses an appropriate mode 5581e52347bdSJani Nikula automatically using heuristics 5582e52347bdSJani Nikula global a single global pool contains all CPUs 5583e52347bdSJani Nikula percpu one pool for each CPU 5584e52347bdSJani Nikula pernode one pool for each NUMA node (equivalent 5585e52347bdSJani Nikula to global on non-NUMA machines) 5586e52347bdSJani Nikula 5587e52347bdSJani Nikula sunrpc.tcp_slot_table_entries= 5588e52347bdSJani Nikula sunrpc.udp_slot_table_entries= 5589e52347bdSJani Nikula [NFS,SUNRPC] 5590e52347bdSJani Nikula Sets the upper limit on the number of simultaneous 5591e52347bdSJani Nikula RPC calls that can be sent from the client to a 5592e52347bdSJani Nikula server. Increasing these values may allow you to 5593e52347bdSJani Nikula improve throughput, but will also increase the 5594e52347bdSJani Nikula amount of memory reserved for use by the client. 5595e52347bdSJani Nikula 5596e52347bdSJani Nikula suspend.pm_test_delay= 5597e52347bdSJani Nikula [SUSPEND] 5598e52347bdSJani Nikula Sets the number of seconds to remain in a suspend test 5599e52347bdSJani Nikula mode before resuming the system (see 5600e52347bdSJani Nikula /sys/power/pm_test). Only available when CONFIG_PM_DEBUG 5601e52347bdSJani Nikula is set. Default value is 5. 5602e52347bdSJani Nikula 56036a9c930bSRam Pai svm= [PPC] 56046a9c930bSRam Pai Format: { on | off | y | n | 1 | 0 } 56056a9c930bSRam Pai This parameter controls use of the Protected 56066a9c930bSRam Pai Execution Facility on pSeries. 56076a9c930bSRam Pai 5608e52347bdSJani Nikula swapaccount=[0|1] 5609e52347bdSJani Nikula [KNL] Enable accounting of swap in memory resource 5610e52347bdSJani Nikula controller if no parameter or 1 is given or disable 5611da82c92fSMauro Carvalho Chehab it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst) 5612e52347bdSJani Nikula 5613e52347bdSJani Nikula swiotlb= [ARM,IA-64,PPC,MIPS,X86] 5614fff5d992SGeert Uytterhoeven Format: { <int> | force | noforce } 5615e52347bdSJani Nikula <int> -- Number of I/O TLB slabs 5616e52347bdSJani Nikula force -- force using of bounce buffers even if they 5617e52347bdSJani Nikula wouldn't be automatically used by the kernel 5618fff5d992SGeert Uytterhoeven noforce -- Never use bounce buffers (for debugging) 5619e52347bdSJani Nikula 5620e52347bdSJani Nikula switches= [HW,M68k] 5621e52347bdSJani Nikula 56223db978d4SVlastimil Babka sysctl.*= [KNL] 56233db978d4SVlastimil Babka Set a sysctl parameter, right before loading the init 56243db978d4SVlastimil Babka process, as if the value was written to the respective 56253db978d4SVlastimil Babka /proc/sys/... file. Both '.' and '/' are recognized as 56263db978d4SVlastimil Babka separators. Unrecognized parameters and invalid values 56273db978d4SVlastimil Babka are reported in the kernel log. Sysctls registered 56283db978d4SVlastimil Babka later by a loaded module cannot be set this way. 56293db978d4SVlastimil Babka Example: sysctl.vm.swappiness=40 56303db978d4SVlastimil Babka 5631e52347bdSJani Nikula sysfs.deprecated=0|1 [KNL] 5632e52347bdSJani Nikula Enable/disable old style sysfs layout for old udev 5633e52347bdSJani Nikula on older distributions. When this option is enabled 5634e52347bdSJani Nikula very new udev will not work anymore. When this option 5635e52347bdSJani Nikula is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) 5636e52347bdSJani Nikula in older udev will not work anymore. 5637e52347bdSJani Nikula Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in 5638e52347bdSJani Nikula the kernel configuration. 5639e52347bdSJani Nikula 5640e52347bdSJani Nikula sysrq_always_enabled 5641e52347bdSJani Nikula [KNL] 5642e52347bdSJani Nikula Ignore sysrq setting - this boot parameter will 5643e52347bdSJani Nikula neutralize any effect of /proc/sys/kernel/sysrq. 5644e52347bdSJani Nikula Useful for debugging. 5645e52347bdSJani Nikula 5646e52347bdSJani Nikula tcpmhash_entries= [KNL,NET] 5647e52347bdSJani Nikula Set the number of tcp_metrics_hash slots. 5648e52347bdSJani Nikula Default value is 8192 or 16384 depending on total 5649e52347bdSJani Nikula ram pages. This is used to specify the TCP metrics 56501cec2cacSMauro Carvalho Chehab cache size. See Documentation/networking/ip-sysctl.rst 5651e52347bdSJani Nikula "tcp_no_metrics_save" section for more details. 5652e52347bdSJani Nikula 5653e52347bdSJani Nikula tdfx= [HW,DRM] 5654e52347bdSJani Nikula 5655e52347bdSJani Nikula test_suspend= [SUSPEND][,N] 5656e52347bdSJani Nikula Specify "mem" (for Suspend-to-RAM) or "standby" (for 5657e52347bdSJani Nikula standby suspend) or "freeze" (for suspend type freeze) 5658e52347bdSJani Nikula as the system sleep state during system startup with 5659e52347bdSJani Nikula the optional capability to repeat N number of times. 5660e52347bdSJani Nikula The system is woken from this state using a 5661e52347bdSJani Nikula wakeup-capable RTC alarm. 5662e52347bdSJani Nikula 5663e52347bdSJani Nikula thash_entries= [KNL,NET] 5664e52347bdSJani Nikula Set number of hash buckets for TCP connection 5665e52347bdSJani Nikula 5666e52347bdSJani Nikula thermal.act= [HW,ACPI] 5667e52347bdSJani Nikula -1: disable all active trip points in all thermal zones 5668e52347bdSJani Nikula <degrees C>: override all lowest active trip points 5669e52347bdSJani Nikula 5670e52347bdSJani Nikula thermal.crt= [HW,ACPI] 5671e52347bdSJani Nikula -1: disable all critical trip points in all thermal zones 5672e52347bdSJani Nikula <degrees C>: override all critical trip points 5673e52347bdSJani Nikula 5674e52347bdSJani Nikula thermal.nocrt= [HW,ACPI] 5675e52347bdSJani Nikula Set to disable actions on ACPI thermal zone 5676e52347bdSJani Nikula critical and hot trip points. 5677e52347bdSJani Nikula 5678e52347bdSJani Nikula thermal.off= [HW,ACPI] 5679e52347bdSJani Nikula 1: disable ACPI thermal control 5680e52347bdSJani Nikula 5681e52347bdSJani Nikula thermal.psv= [HW,ACPI] 5682e52347bdSJani Nikula -1: disable all passive trip points 5683e52347bdSJani Nikula <degrees C>: override all passive trip points to this 5684e52347bdSJani Nikula value 5685e52347bdSJani Nikula 5686e52347bdSJani Nikula thermal.tzp= [HW,ACPI] 5687e52347bdSJani Nikula Specify global default ACPI thermal zone polling rate 5688e52347bdSJani Nikula <deci-seconds>: poll all this frequency 5689e52347bdSJani Nikula 0: no polling (default) 5690e52347bdSJani Nikula 5691e52347bdSJani Nikula threadirqs [KNL] 5692e52347bdSJani Nikula Force threading of all interrupt handlers except those 5693e52347bdSJani Nikula marked explicitly IRQF_NO_THREAD. 5694e52347bdSJani Nikula 5695e52347bdSJani Nikula topology= [S390] 5696e52347bdSJani Nikula Format: {off | on} 5697e52347bdSJani Nikula Specify if the kernel should make use of the cpu 5698e52347bdSJani Nikula topology information if the hardware supports this. 5699e52347bdSJani Nikula The scheduler will make use of this information and 5700e52347bdSJani Nikula e.g. base its process migration decisions on it. 5701e52347bdSJani Nikula Default is on. 5702e52347bdSJani Nikula 5703e52347bdSJani Nikula topology_updates= [KNL, PPC, NUMA] 5704e52347bdSJani Nikula Format: {off} 5705e52347bdSJani Nikula Specify if the kernel should ignore (off) 5706e52347bdSJani Nikula topology updates sent by the hypervisor to this 5707e52347bdSJani Nikula LPAR. 5708e52347bdSJani Nikula 57098171d3e0SPaul E. McKenney torture.disable_onoff_at_boot= [KNL] 57108171d3e0SPaul E. McKenney Prevent the CPU-hotplug component of torturing 57118171d3e0SPaul E. McKenney until after init has spawned. 57128171d3e0SPaul E. McKenney 57132102ad29SPaul E. McKenney torture.ftrace_dump_at_shutdown= [KNL] 57142102ad29SPaul E. McKenney Dump the ftrace buffer at torture-test shutdown, 57152102ad29SPaul E. McKenney even if there were no errors. This can be a 57162102ad29SPaul E. McKenney very costly operation when many torture tests 57172102ad29SPaul E. McKenney are running concurrently, especially on systems 57182102ad29SPaul E. McKenney with rotating-rust storage. 57192102ad29SPaul E. McKenney 57208a67a20bSPaul E. McKenney torture.verbose_sleep_frequency= [KNL] 57218a67a20bSPaul E. McKenney Specifies how many verbose printk()s should be 57228a67a20bSPaul E. McKenney emitted between each sleep. The default of zero 57238a67a20bSPaul E. McKenney disables verbose-printk() sleeping. 57248a67a20bSPaul E. McKenney 57258a67a20bSPaul E. McKenney torture.verbose_sleep_duration= [KNL] 57268a67a20bSPaul E. McKenney Duration of each verbose-printk() sleep in jiffies. 57278a67a20bSPaul E. McKenney 5728e52347bdSJani Nikula tp720= [HW,PS2] 5729e52347bdSJani Nikula 5730e52347bdSJani Nikula tpm_suspend_pcr=[HW,TPM] 5731e52347bdSJani Nikula Format: integer pcr id 5732e52347bdSJani Nikula Specify that at suspend time, the tpm driver 5733e52347bdSJani Nikula should extend the specified pcr with zeros, 5734e52347bdSJani Nikula as a workaround for some chips which fail to 5735e52347bdSJani Nikula flush the last written pcr on TPM_SaveState. 5736e52347bdSJani Nikula This will guarantee that all the other pcrs 5737e52347bdSJani Nikula are saved. 5738e52347bdSJani Nikula 5739e52347bdSJani Nikula trace_buf_size=nn[KMG] 5740e52347bdSJani Nikula [FTRACE] will set tracing buffer size on each cpu. 5741e52347bdSJani Nikula 5742e52347bdSJani Nikula trace_event=[event-list] 5743e52347bdSJani Nikula [FTRACE] Set and start specified trace events in order 5744e52347bdSJani Nikula to facilitate early boot debugging. The event-list is a 574525942e5eSRandy Dunlap comma-separated list of trace events to enable. See 57465fb94e9cSMauro Carvalho Chehab also Documentation/trace/events.rst 5747e52347bdSJani Nikula 5748e52347bdSJani Nikula trace_options=[option-list] 5749e52347bdSJani Nikula [FTRACE] Enable or disable tracer options at boot. 5750e52347bdSJani Nikula The option-list is a comma delimited list of options 5751e52347bdSJani Nikula that can be enabled or disabled just as if you were 5752e52347bdSJani Nikula to echo the option name into 5753e52347bdSJani Nikula 5754e52347bdSJani Nikula /sys/kernel/debug/tracing/trace_options 5755e52347bdSJani Nikula 5756e52347bdSJani Nikula For example, to enable stacktrace option (to dump the 5757e52347bdSJani Nikula stack trace of each event), add to the command line: 5758e52347bdSJani Nikula 5759e52347bdSJani Nikula trace_options=stacktrace 5760e52347bdSJani Nikula 57615fb94e9cSMauro Carvalho Chehab See also Documentation/trace/ftrace.rst "trace options" 5762e52347bdSJani Nikula section. 5763e52347bdSJani Nikula 5764e52347bdSJani Nikula tp_printk[FTRACE] 5765e52347bdSJani Nikula Have the tracepoints sent to printk as well as the 5766e52347bdSJani Nikula tracing ring buffer. This is useful for early boot up 5767e52347bdSJani Nikula where the system hangs or reboots and does not give the 5768e52347bdSJani Nikula option for reading the tracing buffer or performing a 5769e52347bdSJani Nikula ftrace_dump_on_oops. 5770e52347bdSJani Nikula 5771e52347bdSJani Nikula To turn off having tracepoints sent to printk, 5772e52347bdSJani Nikula echo 0 > /proc/sys/kernel/tracepoint_printk 5773e52347bdSJani Nikula Note, echoing 1 into this file without the 5774e52347bdSJani Nikula tracepoint_printk kernel cmdline option has no effect. 5775e52347bdSJani Nikula 5776f3860136SSteven Rostedt (VMware) The tp_printk_stop_on_boot (see below) can also be used 5777f3860136SSteven Rostedt (VMware) to stop the printing of events to console at 5778f3860136SSteven Rostedt (VMware) late_initcall_sync. 5779f3860136SSteven Rostedt (VMware) 5780e52347bdSJani Nikula ** CAUTION ** 5781e52347bdSJani Nikula 5782e52347bdSJani Nikula Having tracepoints sent to printk() and activating high 5783e52347bdSJani Nikula frequency tracepoints such as irq or sched, can cause 5784e52347bdSJani Nikula the system to live lock. 5785e52347bdSJani Nikula 5786f3860136SSteven Rostedt (VMware) tp_printk_stop_on_boot[FTRACE] 5787f3860136SSteven Rostedt (VMware) When tp_printk (above) is set, it can cause a lot of noise 5788f3860136SSteven Rostedt (VMware) on the console. It may be useful to only include the 5789f3860136SSteven Rostedt (VMware) printing of events during boot up, as user space may 5790f3860136SSteven Rostedt (VMware) make the system inoperable. 5791f3860136SSteven Rostedt (VMware) 5792f3860136SSteven Rostedt (VMware) This command line option will stop the printing of events 5793f3860136SSteven Rostedt (VMware) to console at the late_initcall_sync() time frame. 5794f3860136SSteven Rostedt (VMware) 5795e52347bdSJani Nikula traceoff_on_warning 5796e52347bdSJani Nikula [FTRACE] enable this option to disable tracing when a 5797e52347bdSJani Nikula warning is hit. This turns off "tracing_on". Tracing can 5798e52347bdSJani Nikula be enabled again by echoing '1' into the "tracing_on" 5799e52347bdSJani Nikula file located in /sys/kernel/debug/tracing/ 5800e52347bdSJani Nikula 5801e52347bdSJani Nikula This option is useful, as it disables the trace before 5802e52347bdSJani Nikula the WARNING dump is called, which prevents the trace to 5803e52347bdSJani Nikula be filled with content caused by the warning output. 5804e52347bdSJani Nikula 5805e52347bdSJani Nikula This option can also be set at run time via the sysctl 5806e52347bdSJani Nikula option: kernel/traceoff_on_warning 5807e52347bdSJani Nikula 5808e52347bdSJani Nikula transparent_hugepage= 5809e52347bdSJani Nikula [KNL] 5810e52347bdSJani Nikula Format: [always|madvise|never] 5811e52347bdSJani Nikula Can be used to control the default behavior of the system 5812e52347bdSJani Nikula with respect to transparent hugepages. 581345c9a74fSMike Rapoport See Documentation/admin-guide/mm/transhuge.rst 581445c9a74fSMike Rapoport for more details. 5815e52347bdSJani Nikula 58165d0682beSSumit Garg trusted.source= [KEYS] 58175d0682beSSumit Garg Format: <string> 58185d0682beSSumit Garg This parameter identifies the trust source as a backend 58195d0682beSSumit Garg for trusted keys implementation. Supported trust 58205d0682beSSumit Garg sources: 58215d0682beSSumit Garg - "tpm" 58225d0682beSSumit Garg - "tee" 58235d0682beSSumit Garg If not specified then it defaults to iterating through 58245d0682beSSumit Garg the trust source list starting with TPM and assigns the 58255d0682beSSumit Garg first trust source as a backend which is initialized 58265d0682beSSumit Garg successfully during iteration. 58275d0682beSSumit Garg 5828e52347bdSJani Nikula tsc= Disable clocksource stability checks for TSC. 5829e52347bdSJani Nikula Format: <string> 5830e52347bdSJani Nikula [x86] reliable: mark tsc clocksource as reliable, this 5831e52347bdSJani Nikula disables clocksource verification at runtime, as well 5832e52347bdSJani Nikula as the stability checks done at bootup. Used to enable 5833e52347bdSJani Nikula high-resolution timer mode on older hardware, and in 5834e52347bdSJani Nikula virtualized environment. 5835e52347bdSJani Nikula [x86] noirqtime: Do not use TSC to do irq accounting. 5836e52347bdSJani Nikula Used to run time disable IRQ_TIME_ACCOUNTING on any 5837e52347bdSJani Nikula platforms where RDTSC is slow and this accounting 5838e52347bdSJani Nikula can add overhead. 58396be53520SDou Liyang [x86] unstable: mark the TSC clocksource as unstable, this 58406be53520SDou Liyang marks the TSC unconditionally unstable at bootup and 58416be53520SDou Liyang avoids any further wobbles once the TSC watchdog notices. 58420f0b7e1cSJuri Lelli [x86] nowatchdog: disable clocksource watchdog. Used 58430f0b7e1cSJuri Lelli in situations with strict latency requirements (where 58440f0b7e1cSJuri Lelli interruptions from clocksource watchdog are not 58450f0b7e1cSJuri Lelli acceptable). 5846e52347bdSJani Nikula 5847bd35c77eSKrzysztof Piecuch tsc_early_khz= [X86] Skip early TSC calibration and use the given 5848bd35c77eSKrzysztof Piecuch value instead. Useful when the early TSC frequency discovery 5849bd35c77eSKrzysztof Piecuch procedure is not reliable, such as on overclocked systems 5850bd35c77eSKrzysztof Piecuch with CPUID.16h support and partial CPUID.15h support. 5851bd35c77eSKrzysztof Piecuch Format: <unsigned int> 5852bd35c77eSKrzysztof Piecuch 585395c5824fSPawan Gupta tsx= [X86] Control Transactional Synchronization 585495c5824fSPawan Gupta Extensions (TSX) feature in Intel processors that 585595c5824fSPawan Gupta support TSX control. 585695c5824fSPawan Gupta 585795c5824fSPawan Gupta This parameter controls the TSX feature. The options are: 585895c5824fSPawan Gupta 585995c5824fSPawan Gupta on - Enable TSX on the system. Although there are 586095c5824fSPawan Gupta mitigations for all known security vulnerabilities, 586195c5824fSPawan Gupta TSX has been known to be an accelerator for 586295c5824fSPawan Gupta several previous speculation-related CVEs, and 586395c5824fSPawan Gupta so there may be unknown security risks associated 586495c5824fSPawan Gupta with leaving it enabled. 586595c5824fSPawan Gupta 586695c5824fSPawan Gupta off - Disable TSX on the system. (Note that this 586795c5824fSPawan Gupta option takes effect only on newer CPUs which are 586895c5824fSPawan Gupta not vulnerable to MDS, i.e., have 586995c5824fSPawan Gupta MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get 587095c5824fSPawan Gupta the new IA32_TSX_CTRL MSR through a microcode 587195c5824fSPawan Gupta update. This new MSR allows for the reliable 587295c5824fSPawan Gupta deactivation of the TSX functionality.) 587395c5824fSPawan Gupta 58747531a359SPawan Gupta auto - Disable TSX if X86_BUG_TAA is present, 58757531a359SPawan Gupta otherwise enable TSX on the system. 58767531a359SPawan Gupta 587795c5824fSPawan Gupta Not specifying this option is equivalent to tsx=off. 587895c5824fSPawan Gupta 587995c5824fSPawan Gupta See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst 588095c5824fSPawan Gupta for more details. 588195c5824fSPawan Gupta 5882a7a248c5SPawan Gupta tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async 5883a7a248c5SPawan Gupta Abort (TAA) vulnerability. 5884a7a248c5SPawan Gupta 5885a7a248c5SPawan Gupta Similar to Micro-architectural Data Sampling (MDS) 5886a7a248c5SPawan Gupta certain CPUs that support Transactional 5887a7a248c5SPawan Gupta Synchronization Extensions (TSX) are vulnerable to an 5888a7a248c5SPawan Gupta exploit against CPU internal buffers which can forward 5889a7a248c5SPawan Gupta information to a disclosure gadget under certain 5890a7a248c5SPawan Gupta conditions. 5891a7a248c5SPawan Gupta 5892a7a248c5SPawan Gupta In vulnerable processors, the speculatively forwarded 5893a7a248c5SPawan Gupta data can be used in a cache side channel attack, to 5894a7a248c5SPawan Gupta access data to which the attacker does not have direct 5895a7a248c5SPawan Gupta access. 5896a7a248c5SPawan Gupta 5897a7a248c5SPawan Gupta This parameter controls the TAA mitigation. The 5898a7a248c5SPawan Gupta options are: 5899a7a248c5SPawan Gupta 5900a7a248c5SPawan Gupta full - Enable TAA mitigation on vulnerable CPUs 5901a7a248c5SPawan Gupta if TSX is enabled. 5902a7a248c5SPawan Gupta 5903a7a248c5SPawan Gupta full,nosmt - Enable TAA mitigation and disable SMT on 5904a7a248c5SPawan Gupta vulnerable CPUs. If TSX is disabled, SMT 5905a7a248c5SPawan Gupta is not disabled because CPU is not 5906a7a248c5SPawan Gupta vulnerable to cross-thread TAA attacks. 5907a7a248c5SPawan Gupta off - Unconditionally disable TAA mitigation 5908a7a248c5SPawan Gupta 590964870ed1SWaiman Long On MDS-affected machines, tsx_async_abort=off can be 591064870ed1SWaiman Long prevented by an active MDS mitigation as both vulnerabilities 591164870ed1SWaiman Long are mitigated with the same mechanism so in order to disable 591264870ed1SWaiman Long this mitigation, you need to specify mds=off too. 591364870ed1SWaiman Long 5914a7a248c5SPawan Gupta Not specifying this option is equivalent to 5915a7a248c5SPawan Gupta tsx_async_abort=full. On CPUs which are MDS affected 5916a7a248c5SPawan Gupta and deploy MDS mitigation, TAA mitigation is not 5917a7a248c5SPawan Gupta required and doesn't provide any additional 5918a7a248c5SPawan Gupta mitigation. 5919a7a248c5SPawan Gupta 5920a7a248c5SPawan Gupta For details see: 5921a7a248c5SPawan Gupta Documentation/admin-guide/hw-vuln/tsx_async_abort.rst 5922a7a248c5SPawan Gupta 5923e52347bdSJani Nikula turbografx.map[2|3]= [HW,JOY] 5924e52347bdSJani Nikula TurboGraFX parallel port interface 5925e52347bdSJani Nikula Format: 5926e52347bdSJani Nikula <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 59271752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 5928e52347bdSJani Nikula 5929e52347bdSJani Nikula udbg-immortal [PPC] When debugging early kernel crashes that 5930e52347bdSJani Nikula happen after console_init() and before a proper 5931e52347bdSJani Nikula console driver takes over, this boot options might 5932e52347bdSJani Nikula help "seeing" what's going on. 5933e52347bdSJani Nikula 5934e52347bdSJani Nikula uhash_entries= [KNL,NET] 5935e52347bdSJani Nikula Set number of hash buckets for UDP/UDP-Lite connections 5936e52347bdSJani Nikula 5937e52347bdSJani Nikula uhci-hcd.ignore_oc= 5938e52347bdSJani Nikula [USB] Ignore overcurrent events (default N). 5939e52347bdSJani Nikula Some badly-designed motherboards generate lots of 5940e52347bdSJani Nikula bogus events, for ports that aren't wired to 5941e52347bdSJani Nikula anything. Set this parameter to avoid log spamming. 5942e52347bdSJani Nikula Note that genuine overcurrent events won't be 5943e52347bdSJani Nikula reported either. 5944e52347bdSJani Nikula 5945e52347bdSJani Nikula unknown_nmi_panic 5946e52347bdSJani Nikula [X86] Cause panic on unknown NMI. 5947e52347bdSJani Nikula 5948e52347bdSJani Nikula usbcore.authorized_default= 5949e52347bdSJani Nikula [USB] Default USB device authorization: 5950e52347bdSJani Nikula (default -1 = authorized except for wireless USB, 59517bae0432SDmitry Torokhov 0 = not authorized, 1 = authorized, 2 = authorized 59527bae0432SDmitry Torokhov if device connected to internal port) 5953e52347bdSJani Nikula 5954e52347bdSJani Nikula usbcore.autosuspend= 5955e52347bdSJani Nikula [USB] The autosuspend time delay (in seconds) used 5956e52347bdSJani Nikula for newly-detected USB devices (default 2). This 5957e52347bdSJani Nikula is the time required before an idle device will be 5958e52347bdSJani Nikula autosuspended. Devices for which the delay is set 5959e52347bdSJani Nikula to a negative value won't be autosuspended at all. 5960e52347bdSJani Nikula 5961e52347bdSJani Nikula usbcore.usbfs_snoop= 5962e52347bdSJani Nikula [USB] Set to log all usbfs traffic (default 0 = off). 5963e52347bdSJani Nikula 5964e52347bdSJani Nikula usbcore.usbfs_snoop_max= 5965e52347bdSJani Nikula [USB] Maximum number of bytes to snoop in each URB 5966e52347bdSJani Nikula (default = 65536). 5967e52347bdSJani Nikula 5968e52347bdSJani Nikula usbcore.blinkenlights= 5969e52347bdSJani Nikula [USB] Set to cycle leds on hubs (default 0 = off). 5970e52347bdSJani Nikula 5971e52347bdSJani Nikula usbcore.old_scheme_first= 5972e52347bdSJani Nikula [USB] Start with the old device initialization 59733155f4f4SAlan Stern scheme (default 0 = off). 5974e52347bdSJani Nikula 5975e52347bdSJani Nikula usbcore.usbfs_memory_mb= 5976e52347bdSJani Nikula [USB] Memory limit (in MB) for buffers allocated by 5977e52347bdSJani Nikula usbfs (default = 16, 0 = max = 2047). 5978e52347bdSJani Nikula 5979e52347bdSJani Nikula usbcore.use_both_schemes= 5980e52347bdSJani Nikula [USB] Try the other device initialization scheme 5981e52347bdSJani Nikula if the first one fails (default 1 = enabled). 5982e52347bdSJani Nikula 5983e52347bdSJani Nikula usbcore.initial_descriptor_timeout= 5984e52347bdSJani Nikula [USB] Specifies timeout for the initial 64-byte 5985e52347bdSJani Nikula USB_REQ_GET_DESCRIPTOR request in milliseconds 5986e52347bdSJani Nikula (default 5000 = 5.0 seconds). 5987e52347bdSJani Nikula 5988e52347bdSJani Nikula usbcore.nousb [USB] Disable the USB subsystem 5989e52347bdSJani Nikula 5990027bd6caSKai-Heng Feng usbcore.quirks= 5991027bd6caSKai-Heng Feng [USB] A list of quirk entries to augment the built-in 5992027bd6caSKai-Heng Feng usb core quirk list. List entries are separated by 5993027bd6caSKai-Heng Feng commas. Each entry has the form 5994027bd6caSKai-Heng Feng VendorID:ProductID:Flags. The IDs are 4-digit hex 5995027bd6caSKai-Heng Feng numbers and Flags is a set of letters. Each letter 5996027bd6caSKai-Heng Feng will change the built-in quirk; setting it if it is 5997027bd6caSKai-Heng Feng clear and clearing it if it is set. The letters have 5998027bd6caSKai-Heng Feng the following meanings: 5999027bd6caSKai-Heng Feng a = USB_QUIRK_STRING_FETCH_255 (string 6000027bd6caSKai-Heng Feng descriptors must not be fetched using 6001027bd6caSKai-Heng Feng a 255-byte read); 6002027bd6caSKai-Heng Feng b = USB_QUIRK_RESET_RESUME (device can't resume 6003027bd6caSKai-Heng Feng correctly so reset it instead); 6004027bd6caSKai-Heng Feng c = USB_QUIRK_NO_SET_INTF (device can't handle 6005027bd6caSKai-Heng Feng Set-Interface requests); 6006027bd6caSKai-Heng Feng d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't 6007027bd6caSKai-Heng Feng handle its Configuration or Interface 6008027bd6caSKai-Heng Feng strings); 6009027bd6caSKai-Heng Feng e = USB_QUIRK_RESET (device can't be reset 6010027bd6caSKai-Heng Feng (e.g morph devices), don't use reset); 6011027bd6caSKai-Heng Feng f = USB_QUIRK_HONOR_BNUMINTERFACES (device has 6012027bd6caSKai-Heng Feng more interface descriptions than the 6013027bd6caSKai-Heng Feng bNumInterfaces count, and can't handle 6014027bd6caSKai-Heng Feng talking to these interfaces); 6015027bd6caSKai-Heng Feng g = USB_QUIRK_DELAY_INIT (device needs a pause 6016027bd6caSKai-Heng Feng during initialization, after we read 6017027bd6caSKai-Heng Feng the device descriptor); 6018027bd6caSKai-Heng Feng h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For 6019027bd6caSKai-Heng Feng high speed and super speed interrupt 6020027bd6caSKai-Heng Feng endpoints, the USB 2.0 and USB 3.0 spec 6021027bd6caSKai-Heng Feng require the interval in microframes (1 6022027bd6caSKai-Heng Feng microframe = 125 microseconds) to be 6023027bd6caSKai-Heng Feng calculated as interval = 2 ^ 6024027bd6caSKai-Heng Feng (bInterval-1). 6025027bd6caSKai-Heng Feng Devices with this quirk report their 6026027bd6caSKai-Heng Feng bInterval as the result of this 6027027bd6caSKai-Heng Feng calculation instead of the exponent 6028027bd6caSKai-Heng Feng variable used in the calculation); 6029027bd6caSKai-Heng Feng i = USB_QUIRK_DEVICE_QUALIFIER (device can't 6030027bd6caSKai-Heng Feng handle device_qualifier descriptor 6031027bd6caSKai-Heng Feng requests); 6032027bd6caSKai-Heng Feng j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device 6033027bd6caSKai-Heng Feng generates spurious wakeup, ignore 6034027bd6caSKai-Heng Feng remote wakeup capability); 6035027bd6caSKai-Heng Feng k = USB_QUIRK_NO_LPM (device can't handle Link 6036027bd6caSKai-Heng Feng Power Management); 6037027bd6caSKai-Heng Feng l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL 6038027bd6caSKai-Heng Feng (Device reports its bInterval as linear 6039027bd6caSKai-Heng Feng frames instead of the USB 2.0 6040027bd6caSKai-Heng Feng calculation); 6041027bd6caSKai-Heng Feng m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs 6042027bd6caSKai-Heng Feng to be disconnected before suspend to 60434d8d5a39SKai-Heng Feng prevent spurious wakeup); 60444d8d5a39SKai-Heng Feng n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a 60454d8d5a39SKai-Heng Feng pause after every control message); 6046781f0766SKai-Heng Feng o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra 6047781f0766SKai-Heng Feng delay after resetting its port); 6048027bd6caSKai-Heng Feng Example: quirks=0781:5580:bk,0a5c:5834:gij 6049027bd6caSKai-Heng Feng 6050e52347bdSJani Nikula usbhid.mousepoll= 6051e52347bdSJani Nikula [USBHID] The interval which mice are to be polled at. 6052e52347bdSJani Nikula 6053933bfe4dSTobias Jakobi usbhid.jspoll= 6054933bfe4dSTobias Jakobi [USBHID] The interval which joysticks are to be polled at. 6055933bfe4dSTobias Jakobi 60562ddc8e2dSFilip Alac usbhid.kbpoll= 60572ddc8e2dSFilip Alac [USBHID] The interval which keyboards are to be polled at. 60582ddc8e2dSFilip Alac 6059e52347bdSJani Nikula usb-storage.delay_use= 6060e52347bdSJani Nikula [UMS] The delay in seconds before a new device is 6061e52347bdSJani Nikula scanned for Logical Units (default 1). 6062e52347bdSJani Nikula 6063e52347bdSJani Nikula usb-storage.quirks= 6064e52347bdSJani Nikula [UMS] A list of quirks entries to supplement or 6065e52347bdSJani Nikula override the built-in unusual_devs list. List 6066e52347bdSJani Nikula entries are separated by commas. Each entry has 6067e52347bdSJani Nikula the form VID:PID:Flags where VID and PID are Vendor 6068e52347bdSJani Nikula and Product ID values (4-digit hex numbers) and 6069e52347bdSJani Nikula Flags is a set of characters, each corresponding 6070e52347bdSJani Nikula to a common usb-storage quirk flag as follows: 6071e52347bdSJani Nikula a = SANE_SENSE (collect more than 18 bytes 607265cc8bf9SOliver Neukum of sense data, not on uas); 6073e52347bdSJani Nikula b = BAD_SENSE (don't collect more than 18 607465cc8bf9SOliver Neukum bytes of sense data, not on uas); 6075e52347bdSJani Nikula c = FIX_CAPACITY (decrease the reported 6076e52347bdSJani Nikula device capacity by one sector); 6077e52347bdSJani Nikula d = NO_READ_DISC_INFO (don't use 607865cc8bf9SOliver Neukum READ_DISC_INFO command, not on uas); 6079e52347bdSJani Nikula e = NO_READ_CAPACITY_16 (don't use 6080e52347bdSJani Nikula READ_CAPACITY_16 command); 6081e52347bdSJani Nikula f = NO_REPORT_OPCODES (don't use report opcodes 6082e52347bdSJani Nikula command, uas only); 6083e52347bdSJani Nikula g = MAX_SECTORS_240 (don't transfer more than 6084e52347bdSJani Nikula 240 sectors at a time, uas only); 6085e52347bdSJani Nikula h = CAPACITY_HEURISTICS (decrease the 6086e52347bdSJani Nikula reported device capacity by one 6087e52347bdSJani Nikula sector if the number is odd); 6088e52347bdSJani Nikula i = IGNORE_DEVICE (don't bind to this 6089e52347bdSJani Nikula device); 6090e52347bdSJani Nikula j = NO_REPORT_LUNS (don't use report luns 6091e52347bdSJani Nikula command, uas only); 60928010622cSOliver Neukum k = NO_SAME (do not use WRITE_SAME, uas only) 6093e52347bdSJani Nikula l = NOT_LOCKABLE (don't try to lock and 609465cc8bf9SOliver Neukum unlock ejectable media, not on uas); 6095e52347bdSJani Nikula m = MAX_SECTORS_64 (don't transfer more 609665cc8bf9SOliver Neukum than 64 sectors = 32 KB at a time, 609765cc8bf9SOliver Neukum not on uas); 6098e52347bdSJani Nikula n = INITIAL_READ10 (force a retry of the 609965cc8bf9SOliver Neukum initial READ(10) command, not on uas); 6100e52347bdSJani Nikula o = CAPACITY_OK (accept the capacity 610165cc8bf9SOliver Neukum reported by the device, not on uas); 6102e52347bdSJani Nikula p = WRITE_CACHE (the device cache is ON 610365cc8bf9SOliver Neukum by default, not on uas); 6104e52347bdSJani Nikula r = IGNORE_RESIDUE (the device reports 610565cc8bf9SOliver Neukum bogus residue values, not on uas); 6106e52347bdSJani Nikula s = SINGLE_LUN (the device has only one 6107e52347bdSJani Nikula Logical Unit); 6108e52347bdSJani Nikula t = NO_ATA_1X (don't allow ATA(12) and ATA(16) 6109e52347bdSJani Nikula commands, uas only); 6110e52347bdSJani Nikula u = IGNORE_UAS (don't bind to the uas driver); 6111e52347bdSJani Nikula w = NO_WP_DETECT (don't test whether the 6112e52347bdSJani Nikula medium is write-protected). 6113e52347bdSJani Nikula y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE 611465cc8bf9SOliver Neukum even if the device claims no cache, 611565cc8bf9SOliver Neukum not on uas) 6116e52347bdSJani Nikula Example: quirks=0419:aaf5:rl,0421:0433:rc 6117e52347bdSJani Nikula 6118e52347bdSJani Nikula user_debug= [KNL,ARM] 6119e52347bdSJani Nikula Format: <int> 6120e52347bdSJani Nikula See arch/arm/Kconfig.debug help text. 6121e52347bdSJani Nikula 1 - undefined instruction events 6122e52347bdSJani Nikula 2 - system calls 6123e52347bdSJani Nikula 4 - invalid data aborts 6124e52347bdSJani Nikula 8 - SIGSEGV faults 6125e52347bdSJani Nikula 16 - SIGBUS faults 6126e52347bdSJani Nikula Example: user_debug=31 6127e52347bdSJani Nikula 6128e52347bdSJani Nikula userpte= 6129e52347bdSJani Nikula [X86] Flags controlling user PTE allocations. 6130e52347bdSJani Nikula 6131e52347bdSJani Nikula nohigh = do not allocate PTE pages in 6132e52347bdSJani Nikula HIGHMEM regardless of setting 6133e52347bdSJani Nikula of CONFIG_HIGHPTE. 6134e52347bdSJani Nikula 6135e52347bdSJani Nikula vdso= [X86,SH] 6136e52347bdSJani Nikula On X86_32, this is an alias for vdso32=. Otherwise: 6137e52347bdSJani Nikula 6138e52347bdSJani Nikula vdso=1: enable VDSO (the default) 6139e52347bdSJani Nikula vdso=0: disable VDSO mapping 6140e52347bdSJani Nikula 6141e52347bdSJani Nikula vdso32= [X86] Control the 32-bit vDSO 6142e52347bdSJani Nikula vdso32=1: enable 32-bit VDSO 6143e52347bdSJani Nikula vdso32=0 or vdso32=2: disable 32-bit VDSO 6144e52347bdSJani Nikula 6145e52347bdSJani Nikula See the help text for CONFIG_COMPAT_VDSO for more 6146e52347bdSJani Nikula details. If CONFIG_COMPAT_VDSO is set, the default is 6147e52347bdSJani Nikula vdso32=0; otherwise, the default is vdso32=1. 6148e52347bdSJani Nikula 6149e52347bdSJani Nikula For compatibility with older kernels, vdso32=2 is an 6150e52347bdSJani Nikula alias for vdso32=0. 6151e52347bdSJani Nikula 6152e52347bdSJani Nikula Try vdso32=0 if you encounter an error that says: 6153e52347bdSJani Nikula dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! 6154e52347bdSJani Nikula 6155e52347bdSJani Nikula vector= [IA-64,SMP] 6156e52347bdSJani Nikula vector=percpu: enable percpu vector domain 6157e52347bdSJani Nikula 6158e52347bdSJani Nikula video= [FB] Frame buffer configuration 6159ab42b818SMauro Carvalho Chehab See Documentation/fb/modedb.rst. 6160e52347bdSJani Nikula 6161e52347bdSJani Nikula video.brightness_switch_enabled= [0,1] 6162e52347bdSJani Nikula If set to 1, on receiving an ACPI notify event 6163e52347bdSJani Nikula generated by hotkey, video driver will adjust brightness 6164e52347bdSJani Nikula level and then send out the event to user space through 6165e52347bdSJani Nikula the allocated input device; If set to 0, video driver 6166e52347bdSJani Nikula will only send out the event without touching backlight 6167e52347bdSJani Nikula brightness level. 6168e52347bdSJani Nikula default: 1 6169e52347bdSJani Nikula 6170e52347bdSJani Nikula virtio_mmio.device= 6171e52347bdSJani Nikula [VMMIO] Memory mapped virtio (platform) device. 6172e52347bdSJani Nikula 6173e52347bdSJani Nikula <size>@<baseaddr>:<irq>[:<id>] 6174e52347bdSJani Nikula where: 6175e52347bdSJani Nikula <size> := size (can use standard suffixes 6176e52347bdSJani Nikula like K, M and G) 6177e52347bdSJani Nikula <baseaddr> := physical base address 6178e52347bdSJani Nikula <irq> := interrupt number (as passed to 6179e52347bdSJani Nikula request_irq()) 6180e52347bdSJani Nikula <id> := (optional) platform device id 6181e52347bdSJani Nikula example: 6182e52347bdSJani Nikula virtio_mmio.device=1K@0x100b0000:48:7 6183e52347bdSJani Nikula 6184e52347bdSJani Nikula Can be used multiple times for multiple devices. 6185e52347bdSJani Nikula 6186e52347bdSJani Nikula vga= [BOOT,X86-32] Select a particular video mode 6187cb1aaebeSMauro Carvalho Chehab See Documentation/x86/boot.rst and 61884f4cfa6cSMauro Carvalho Chehab Documentation/admin-guide/svga.rst. 6189e52347bdSJani Nikula Use vga=ask for menu. 6190e52347bdSJani Nikula This is actually a boot loader parameter; the value is 6191e52347bdSJani Nikula passed to the kernel using a special protocol. 6192e52347bdSJani Nikula 6193f682a97aSAlexander Duyck vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y. 6194f682a97aSAlexander Duyck May slow down system boot speed, especially when 6195f682a97aSAlexander Duyck enabled on systems with a large amount of memory. 6196f682a97aSAlexander Duyck All options are enabled by default, and this 6197f682a97aSAlexander Duyck interface is meant to allow for selectively 6198f682a97aSAlexander Duyck enabling or disabling specific virtual memory 6199f682a97aSAlexander Duyck debugging features. 6200f682a97aSAlexander Duyck 6201f682a97aSAlexander Duyck Available options are: 6202f682a97aSAlexander Duyck P Enable page structure init time poisoning 6203f682a97aSAlexander Duyck - Disable all of the above options 6204f682a97aSAlexander Duyck 6205e52347bdSJani Nikula vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 6206e52347bdSJani Nikula size of <nn>. This can be used to increase the 6207e52347bdSJani Nikula minimum size (128MB on x86). It can also be used to 6208e52347bdSJani Nikula decrease the size and leave more room for directly 6209e52347bdSJani Nikula mapped kernel RAM. 6210e52347bdSJani Nikula 62113f429842SHeiko Carstens vmcp_cma=nn[MG] [KNL,S390] 62123f429842SHeiko Carstens Sets the memory size reserved for contiguous memory 62133f429842SHeiko Carstens allocations for the vmcp device driver. 62143f429842SHeiko Carstens 6215e52347bdSJani Nikula vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 6216e52347bdSJani Nikula Format: <command> 6217e52347bdSJani Nikula 6218e52347bdSJani Nikula vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 6219e52347bdSJani Nikula Format: <command> 6220e52347bdSJani Nikula 6221e52347bdSJani Nikula vmpoff= [KNL,S390] Perform z/VM CP command after power off. 6222e52347bdSJani Nikula Format: <command> 6223e52347bdSJani Nikula 6224e52347bdSJani Nikula vsyscall= [X86-64] 6225e52347bdSJani Nikula Controls the behavior of vsyscalls (i.e. calls to 6226e52347bdSJani Nikula fixed addresses of 0xffffffffff600x00 from legacy 6227e52347bdSJani Nikula code). Most statically-linked binaries and older 6228e52347bdSJani Nikula versions of glibc use these calls. Because these 6229e52347bdSJani Nikula functions are at fixed addresses, they make nice 6230e52347bdSJani Nikula targets for exploits that can control RIP. 6231e52347bdSJani Nikula 6232e52347bdSJani Nikula emulate [default] Vsyscalls turn into traps and are 6233bd49e16eSAndy Lutomirski emulated reasonably safely. The vsyscall 6234bd49e16eSAndy Lutomirski page is readable. 6235e52347bdSJani Nikula 6236bd49e16eSAndy Lutomirski xonly Vsyscalls turn into traps and are 6237bd49e16eSAndy Lutomirski emulated reasonably safely. The vsyscall 6238bd49e16eSAndy Lutomirski page is not readable. 6239e52347bdSJani Nikula 6240e52347bdSJani Nikula none Vsyscalls don't work at all. This makes 6241e52347bdSJani Nikula them quite hard to use for exploits but 6242e52347bdSJani Nikula might break your system. 6243e52347bdSJani Nikula 6244e52347bdSJani Nikula vt.color= [VT] Default text color. 6245e52347bdSJani Nikula Format: 0xYX, X = foreground, Y = background. 6246e52347bdSJani Nikula Default: 0x07 = light gray on black. 6247e52347bdSJani Nikula 6248e52347bdSJani Nikula vt.cur_default= [VT] Default cursor shape. 6249e52347bdSJani Nikula Format: 0xCCBBAA, where AA, BB, and CC are the same as 6250e52347bdSJani Nikula the parameters of the <Esc>[?A;B;Cc escape sequence; 6251e52347bdSJani Nikula see VGA-softcursor.txt. Default: 2 = underline. 6252e52347bdSJani Nikula 6253e52347bdSJani Nikula vt.default_blu= [VT] 6254e52347bdSJani Nikula Format: <blue0>,<blue1>,<blue2>,...,<blue15> 6255e52347bdSJani Nikula Change the default blue palette of the console. 6256e52347bdSJani Nikula This is a 16-member array composed of values 6257e52347bdSJani Nikula ranging from 0-255. 6258e52347bdSJani Nikula 6259e52347bdSJani Nikula vt.default_grn= [VT] 6260e52347bdSJani Nikula Format: <green0>,<green1>,<green2>,...,<green15> 6261e52347bdSJani Nikula Change the default green palette of the console. 6262e52347bdSJani Nikula This is a 16-member array composed of values 6263e52347bdSJani Nikula ranging from 0-255. 6264e52347bdSJani Nikula 6265e52347bdSJani Nikula vt.default_red= [VT] 6266e52347bdSJani Nikula Format: <red0>,<red1>,<red2>,...,<red15> 6267e52347bdSJani Nikula Change the default red palette of the console. 6268e52347bdSJani Nikula This is a 16-member array composed of values 6269e52347bdSJani Nikula ranging from 0-255. 6270e52347bdSJani Nikula 6271e52347bdSJani Nikula vt.default_utf8= 6272e52347bdSJani Nikula [VT] 6273e52347bdSJani Nikula Format=<0|1> 6274e52347bdSJani Nikula Set system-wide default UTF-8 mode for all tty's. 6275e52347bdSJani Nikula Default is 1, i.e. UTF-8 mode is enabled for all 6276e52347bdSJani Nikula newly opened terminals. 6277e52347bdSJani Nikula 6278e52347bdSJani Nikula vt.global_cursor_default= 6279e52347bdSJani Nikula [VT] 6280e52347bdSJani Nikula Format=<-1|0|1> 6281e52347bdSJani Nikula Set system-wide default for whether a cursor 6282e52347bdSJani Nikula is shown on new VTs. Default is -1, 6283e52347bdSJani Nikula i.e. cursors will be created by default unless 6284e52347bdSJani Nikula overridden by individual drivers. 0 will hide 6285e52347bdSJani Nikula cursors, 1 will display them. 6286e52347bdSJani Nikula 6287e52347bdSJani Nikula vt.italic= [VT] Default color for italic text; 0-15. 6288e52347bdSJani Nikula Default: 2 = green. 6289e52347bdSJani Nikula 6290e52347bdSJani Nikula vt.underline= [VT] Default color for underlined text; 0-15. 6291e52347bdSJani Nikula Default: 3 = cyan. 6292e52347bdSJani Nikula 6293e52347bdSJani Nikula watchdog timers [HW,WDT] For information on watchdog timers, 6294cc2a2d19SMauro Carvalho Chehab see Documentation/watchdog/watchdog-parameters.rst 6295e52347bdSJani Nikula or other driver-specific files in the 6296e52347bdSJani Nikula Documentation/watchdog/ directory. 6297e52347bdSJani Nikula 629811295055SLaurence Oberman watchdog_thresh= 629911295055SLaurence Oberman [KNL] 630011295055SLaurence Oberman Set the hard lockup detector stall duration 630111295055SLaurence Oberman threshold in seconds. The soft lockup detector 630211295055SLaurence Oberman threshold is set to twice the value. A value of 0 630311295055SLaurence Oberman disables both lockup detectors. Default is 10 630411295055SLaurence Oberman seconds. 630511295055SLaurence Oberman 6306e52347bdSJani Nikula workqueue.watchdog_thresh= 6307e52347bdSJani Nikula If CONFIG_WQ_WATCHDOG is configured, workqueue can 6308e52347bdSJani Nikula warn stall conditions and dump internal state to 6309e52347bdSJani Nikula help debugging. 0 disables workqueue stall 6310e52347bdSJani Nikula detection; otherwise, it's the stall threshold 6311e52347bdSJani Nikula duration in seconds. The default value is 30 and 6312e52347bdSJani Nikula it can be updated at runtime by writing to the 6313e52347bdSJani Nikula corresponding sysfs file. 6314e52347bdSJani Nikula 6315e52347bdSJani Nikula workqueue.disable_numa 6316e52347bdSJani Nikula By default, all work items queued to unbound 6317e52347bdSJani Nikula workqueues are affine to the NUMA nodes they're 6318e52347bdSJani Nikula issued on, which results in better behavior in 6319e52347bdSJani Nikula general. If NUMA affinity needs to be disabled for 6320e52347bdSJani Nikula whatever reason, this option can be used. Note 6321e52347bdSJani Nikula that this also can be controlled per-workqueue for 6322e52347bdSJani Nikula workqueues visible under /sys/bus/workqueue/. 6323e52347bdSJani Nikula 6324e52347bdSJani Nikula workqueue.power_efficient 6325e52347bdSJani Nikula Per-cpu workqueues are generally preferred because 6326e52347bdSJani Nikula they show better performance thanks to cache 6327e52347bdSJani Nikula locality; unfortunately, per-cpu workqueues tend to 6328e52347bdSJani Nikula be more power hungry than unbound workqueues. 6329e52347bdSJani Nikula 6330e52347bdSJani Nikula Enabling this makes the per-cpu workqueues which 6331e52347bdSJani Nikula were observed to contribute significantly to power 6332e52347bdSJani Nikula consumption unbound, leading to measurably lower 6333e52347bdSJani Nikula power usage at the cost of small performance 6334e52347bdSJani Nikula overhead. 6335e52347bdSJani Nikula 6336e52347bdSJani Nikula The default value of this parameter is determined by 6337e52347bdSJani Nikula the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. 6338e52347bdSJani Nikula 6339e52347bdSJani Nikula workqueue.debug_force_rr_cpu 6340e52347bdSJani Nikula Workqueue used to implicitly guarantee that work 6341e52347bdSJani Nikula items queued without explicit CPU specified are put 6342e52347bdSJani Nikula on the local CPU. This guarantee is no longer true 6343e52347bdSJani Nikula and while local CPU is still preferred work items 6344e52347bdSJani Nikula may be put on foreign CPUs. This debug option 6345e52347bdSJani Nikula forces round-robin CPU selection to flush out 6346e52347bdSJani Nikula usages which depend on the now broken guarantee. 6347e52347bdSJani Nikula When enabled, memory and cache locality will be 6348e52347bdSJani Nikula impacted. 6349e52347bdSJani Nikula 6350e52347bdSJani Nikula x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 6351e52347bdSJani Nikula default x2apic cluster mode on platforms 6352e52347bdSJani Nikula supporting x2apic. 6353e52347bdSJani Nikula 6354e52347bdSJani Nikula xen_512gb_limit [KNL,X86-64,XEN] 6355e52347bdSJani Nikula Restricts the kernel running paravirtualized under Xen 6356e52347bdSJani Nikula to use only up to 512 GB of RAM. The reason to do so is 6357e52347bdSJani Nikula crash analysis tools and Xen tools for doing domain 6358e52347bdSJani Nikula save/restore/migration must be enabled to handle larger 6359e52347bdSJani Nikula domains. 6360e52347bdSJani Nikula 6361e52347bdSJani Nikula xen_emul_unplug= [HW,X86,XEN] 6362e52347bdSJani Nikula Unplug Xen emulated devices 6363e52347bdSJani Nikula Format: [unplug0,][unplug1] 6364e52347bdSJani Nikula ide-disks -- unplug primary master IDE devices 6365e52347bdSJani Nikula aux-ide-disks -- unplug non-primary-master IDE devices 6366e52347bdSJani Nikula nics -- unplug network devices 6367e52347bdSJani Nikula all -- unplug all emulated devices (NICs and IDE disks) 6368e52347bdSJani Nikula unnecessary -- unplugging emulated devices is 6369e52347bdSJani Nikula unnecessary even if the host did not respond to 6370e52347bdSJani Nikula the unplug protocol 6371e52347bdSJani Nikula never -- do not unplug even if version check succeeds 6372e52347bdSJani Nikula 6373c6875f3aSBoris Ostrovsky xen_legacy_crash [X86,XEN] 6374c6875f3aSBoris Ostrovsky Crash from Xen panic notifier, without executing late 6375c6875f3aSBoris Ostrovsky panic() code such as dumping handler. 6376c6875f3aSBoris Ostrovsky 6377e52347bdSJani Nikula xen_nopvspin [X86,XEN] 63789a3c05e6SZhenzhong Duan Disables the qspinlock slowpath using Xen PV optimizations. 63799a3c05e6SZhenzhong Duan This parameter is obsoleted by "nopvspin" parameter, which 63809a3c05e6SZhenzhong Duan has equivalent effect for XEN platform. 6381e52347bdSJani Nikula 6382e52347bdSJani Nikula xen_nopv [X86] 6383e52347bdSJani Nikula Disables the PV optimizations forcing the HVM guest to 6384e52347bdSJani Nikula run as generic HVM guest with no PV drivers. 6385b39b0497SZhenzhong Duan This option is obsoleted by the "nopv" option, which 6386b39b0497SZhenzhong Duan has equivalent effect for XEN platform. 6387e52347bdSJani Nikula 6388b36b0fe9SDavid Woodhouse xen_no_vector_callback 6389b36b0fe9SDavid Woodhouse [KNL,X86,XEN] Disable the vector callback for Xen 6390b36b0fe9SDavid Woodhouse event channel interrupts. 6391b36b0fe9SDavid Woodhouse 6392197ecb38SMarek Marczykowski-Górecki xen_scrub_pages= [XEN] 6393197ecb38SMarek Marczykowski-Górecki Boolean option to control scrubbing pages before giving them back 6394197ecb38SMarek Marczykowski-Górecki to Xen, for use by other domains. Can be also changed at runtime 6395197ecb38SMarek Marczykowski-Górecki with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. 6396197ecb38SMarek Marczykowski-Górecki Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. 6397197ecb38SMarek Marczykowski-Górecki 63982ec16bc0SRyan Thibodeaux xen_timer_slop= [X86-64,XEN] 63992ec16bc0SRyan Thibodeaux Set the timer slop (in nanoseconds) for the virtual Xen 64002ec16bc0SRyan Thibodeaux timers (default is 100000). This adjusts the minimum 64012ec16bc0SRyan Thibodeaux delta of virtualized Xen timers, where lower values 64022ec16bc0SRyan Thibodeaux improve timer resolution at the expense of processing 64032ec16bc0SRyan Thibodeaux more timer interrupts. 64042ec16bc0SRyan Thibodeaux 640540fdea02SJuergen Gross xen.balloon_boot_timeout= [XEN] 640640fdea02SJuergen Gross The time (in seconds) to wait before giving up to boot 640740fdea02SJuergen Gross in case initial ballooning fails to free enough memory. 640840fdea02SJuergen Gross Applies only when running as HVM or PVH guest and 640940fdea02SJuergen Gross started with less memory configured than allowed at 641040fdea02SJuergen Gross max. Default is 180. 641140fdea02SJuergen Gross 6412e99502f7SJuergen Gross xen.event_eoi_delay= [XEN] 6413e99502f7SJuergen Gross How long to delay EOI handling in case of event 6414e99502f7SJuergen Gross storms (jiffies). Default is 10. 6415e99502f7SJuergen Gross 6416e99502f7SJuergen Gross xen.event_loop_timeout= [XEN] 6417e99502f7SJuergen Gross After which time (jiffies) the event handling loop 6418e99502f7SJuergen Gross should start to delay EOI handling. Default is 2. 6419e99502f7SJuergen Gross 64201a89c1dcSJuergen Gross xen.fifo_events= [XEN] 64211a89c1dcSJuergen Gross Boolean parameter to disable using fifo event handling 64221a89c1dcSJuergen Gross even if available. Normally fifo event handling is 64231a89c1dcSJuergen Gross preferred over the 2-level event handling, as it is 64241a89c1dcSJuergen Gross fairer and the number of possible event channels is 64251a89c1dcSJuergen Gross much higher. Default is on (use fifo events). 64261a89c1dcSJuergen Gross 642730978346SZhenzhong Duan nopv= [X86,XEN,KVM,HYPER_V,VMWARE] 642830978346SZhenzhong Duan Disables the PV optimizations forcing the guest to run 642930978346SZhenzhong Duan as generic guest with no PV drivers. Currently support 643030978346SZhenzhong Duan XEN HVM, KVM, HYPER_V and VMWARE guest. 643130978346SZhenzhong Duan 64329a3c05e6SZhenzhong Duan nopvspin [X86,XEN,KVM] 643305eee619SZhenzhong Duan Disables the qspinlock slow path using PV optimizations 643405eee619SZhenzhong Duan which allow the hypervisor to 'idle' the guest on lock 643505eee619SZhenzhong Duan contention. 643605eee619SZhenzhong Duan 6437e52347bdSJani Nikula xirc2ps_cs= [NET,PCMCIA] 6438e52347bdSJani Nikula Format: 6439e52347bdSJani Nikula <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 6440c0addc9aSLaurentiu Tudor 6441ba45cff6SMichael Neuling xive= [PPC] 6442ba45cff6SMichael Neuling By default on POWER9 and above, the kernel will 6443ba45cff6SMichael Neuling natively use the XIVE interrupt controller. This option 6444ba45cff6SMichael Neuling allows the fallback firmware mode to be used: 6445ba45cff6SMichael Neuling 6446ba45cff6SMichael Neuling off Fallback to firmware control of XIVE interrupt 6447ba45cff6SMichael Neuling controller on both pseries and powernv 6448ba45cff6SMichael Neuling platforms. Only useful on POWER9 and above. 6449ba45cff6SMichael Neuling 6450c0addc9aSLaurentiu Tudor xhci-hcd.quirks [USB,KNL] 6451c0addc9aSLaurentiu Tudor A hex value specifying bitmask with supplemental xhci 6452c0addc9aSLaurentiu Tudor host controller quirks. Meaning of each bit can be 6453c0addc9aSLaurentiu Tudor consulted in header drivers/usb/host/xhci.h. 64546278f55bSGustavo Romero 64556278f55bSGustavo Romero xmon [PPC] 64566278f55bSGustavo Romero Format: { early | on | rw | ro | off } 64576278f55bSGustavo Romero Controls if xmon debugger is enabled. Default is off. 64586278f55bSGustavo Romero Passing only "xmon" is equivalent to "xmon=early". 64596278f55bSGustavo Romero early Call xmon as early as possible on boot; xmon 64606278f55bSGustavo Romero debugger is called from setup_arch(). 64616278f55bSGustavo Romero on xmon debugger hooks will be installed so xmon 64626278f55bSGustavo Romero is only called on a kernel crash. Default mode, 64636278f55bSGustavo Romero i.e. either "ro" or "rw" mode, is controlled 64646278f55bSGustavo Romero with CONFIG_XMON_DEFAULT_RO_MODE. 64656278f55bSGustavo Romero rw xmon debugger hooks will be installed so xmon 64666278f55bSGustavo Romero is called only on a kernel crash, mode is write, 64676278f55bSGustavo Romero meaning SPR registers, memory and, other data 64686278f55bSGustavo Romero can be written using xmon commands. 64696278f55bSGustavo Romero ro same as "rw" option above but SPR registers, 64706278f55bSGustavo Romero memory, and other data can't be written using 64716278f55bSGustavo Romero xmon commands. 64726278f55bSGustavo Romero off xmon is disabled. 6473