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., 53e52347bdSJani Nikula #define _COMPONENT ACPI_PCI_COMPONENT 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 PCI/PCI interrupt routing info messages: 64e52347bdSJani Nikula acpi.debug_layer=0x400000 65e52347bdSJani Nikula Enable AML "Debug" output, i.e., stores to the Debug 66e52347bdSJani Nikula object while interpreting AML: 67e52347bdSJani Nikula acpi.debug_layer=0xffffffff acpi.debug_level=0x2 68e52347bdSJani Nikula Enable all messages related to ACPI hardware: 69e52347bdSJani Nikula acpi.debug_layer=0x2 acpi.debug_level=0xffffffff 70e52347bdSJani Nikula 71e52347bdSJani Nikula Some values produce so much output that the system is 72e52347bdSJani Nikula unusable. The "log_buf_len" parameter may be useful 73e52347bdSJani Nikula if you need to capture more output. 74e52347bdSJani Nikula 75e52347bdSJani Nikula acpi_enforce_resources= [ACPI] 76e52347bdSJani Nikula { strict | lax | no } 77e52347bdSJani Nikula Check for resource conflicts between native drivers 78e52347bdSJani Nikula and ACPI OperationRegions (SystemIO and SystemMemory 79e52347bdSJani Nikula only). IO ports and memory declared in ACPI might be 80e52347bdSJani Nikula used by the ACPI subsystem in arbitrary AML code and 81e52347bdSJani Nikula can interfere with legacy drivers. 82e52347bdSJani Nikula strict (default): access to resources claimed by ACPI 83e52347bdSJani Nikula is denied; legacy drivers trying to access reserved 84e52347bdSJani Nikula resources will fail to bind to device using them. 85e52347bdSJani Nikula lax: access to resources claimed by ACPI is allowed; 86e52347bdSJani Nikula legacy drivers trying to access reserved resources 87e52347bdSJani Nikula will bind successfully but a warning message is logged. 88e52347bdSJani Nikula no: ACPI OperationRegions are not marked as reserved, 89e52347bdSJani Nikula no further checks are performed. 90e52347bdSJani Nikula 91e52347bdSJani Nikula acpi_force_table_verification [HW,ACPI] 92e52347bdSJani Nikula Enable table checksum verification during early stage. 93e52347bdSJani Nikula By default, this is disabled due to x86 early mapping 94e52347bdSJani Nikula size limitation. 95e52347bdSJani Nikula 96e52347bdSJani Nikula acpi_irq_balance [HW,ACPI] 97e52347bdSJani Nikula ACPI will balance active IRQs 98e52347bdSJani Nikula default in APIC mode 99e52347bdSJani Nikula 100e52347bdSJani Nikula acpi_irq_nobalance [HW,ACPI] 101e52347bdSJani Nikula ACPI will not move active IRQs (default) 102e52347bdSJani Nikula default in PIC mode 103e52347bdSJani Nikula 104e52347bdSJani Nikula acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 105e52347bdSJani Nikula Format: <irq>,<irq>... 106e52347bdSJani Nikula 107e52347bdSJani Nikula acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 108e52347bdSJani Nikula use by PCI 109e52347bdSJani Nikula Format: <irq>,<irq>... 110e52347bdSJani Nikula 1119c4aa1eeSLv Zheng acpi_mask_gpe= [HW,ACPI] 1129c4aa1eeSLv Zheng Due to the existence of _Lxx/_Exx, some GPEs triggered 1139c4aa1eeSLv Zheng by unsupported hardware/firmware features can result in 1149c4aa1eeSLv Zheng GPE floodings that cannot be automatically disabled by 1159c4aa1eeSLv Zheng the GPE dispatcher. 1169c4aa1eeSLv Zheng This facility can be used to prevent such uncontrolled 1179c4aa1eeSLv Zheng GPE floodings. 118a7583e72SYunfeng Ye Format: <byte> 1199c4aa1eeSLv Zheng 120e52347bdSJani Nikula acpi_no_auto_serialize [HW,ACPI] 121e52347bdSJani Nikula Disable auto-serialization of AML methods 122e52347bdSJani Nikula AML control methods that contain the opcodes to create 123e52347bdSJani Nikula named objects will be marked as "Serialized" by the 124e52347bdSJani Nikula auto-serialization feature. 125e52347bdSJani Nikula This feature is enabled by default. 126e52347bdSJani Nikula This option allows to turn off the feature. 127e52347bdSJani Nikula 128e52347bdSJani Nikula acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump 129e52347bdSJani Nikula kernels. 130e52347bdSJani Nikula 131e52347bdSJani Nikula acpi_no_static_ssdt [HW,ACPI] 132e52347bdSJani Nikula Disable installation of static SSDTs at early boot time 133e52347bdSJani Nikula By default, SSDTs contained in the RSDT/XSDT will be 134e52347bdSJani Nikula installed automatically and they will appear under 135e52347bdSJani Nikula /sys/firmware/acpi/tables. 136e52347bdSJani Nikula This option turns off this feature. 137e52347bdSJani Nikula Note that specifying this option does not affect 138e52347bdSJani Nikula dynamic table installation which will install SSDT 139e52347bdSJani Nikula tables to /sys/firmware/acpi/tables/dynamic. 140e52347bdSJani Nikula 1413f9e12e0SJean Delvare acpi_no_watchdog [HW,ACPI,WDT] 1423f9e12e0SJean Delvare Ignore the ACPI-based watchdog interface (WDAT) and let 1433f9e12e0SJean Delvare a native driver control the watchdog device instead. 1443f9e12e0SJean Delvare 145e52347bdSJani Nikula acpi_rsdp= [ACPI,EFI,KEXEC] 146e52347bdSJani Nikula Pass the RSDP address to the kernel, mostly used 147e52347bdSJani Nikula on machines running EFI runtime service to boot the 148e52347bdSJani Nikula second kernel for kdump. 149e52347bdSJani Nikula 150e52347bdSJani Nikula acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 151e52347bdSJani Nikula Format: To spoof as Windows 98: ="Microsoft Windows" 152e52347bdSJani Nikula 153e52347bdSJani Nikula acpi_rev_override [ACPI] Override the _REV object to return 5 (instead 154e52347bdSJani Nikula of 2 which is mandated by ACPI 6) as the supported ACPI 155e52347bdSJani Nikula specification revision (when using this switch, it may 156e52347bdSJani Nikula be necessary to carry out a cold reboot _twice_ in a 157e52347bdSJani Nikula row to make it take effect on the platform firmware). 158e52347bdSJani Nikula 159e52347bdSJani Nikula acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 160e52347bdSJani Nikula acpi_osi="string1" # add string1 161e52347bdSJani Nikula acpi_osi="!string2" # remove string2 162e52347bdSJani Nikula acpi_osi=!* # remove all strings 163e52347bdSJani Nikula acpi_osi=! # disable all built-in OS vendor 164e52347bdSJani Nikula strings 165e52347bdSJani Nikula acpi_osi=!! # enable all built-in OS vendor 166e52347bdSJani Nikula strings 167e52347bdSJani Nikula acpi_osi= # disable all strings 168e52347bdSJani Nikula 169e52347bdSJani Nikula 'acpi_osi=!' can be used in combination with single or 170e52347bdSJani Nikula multiple 'acpi_osi="string1"' to support specific OS 171e52347bdSJani Nikula vendor string(s). Note that such command can only 172e52347bdSJani Nikula affect the default state of the OS vendor strings, thus 173e52347bdSJani Nikula it cannot affect the default state of the feature group 174e52347bdSJani Nikula strings and the current state of the OS vendor strings, 175e52347bdSJani Nikula specifying it multiple times through kernel command line 176e52347bdSJani Nikula is meaningless. This command is useful when one do not 177e52347bdSJani Nikula care about the state of the feature group strings which 178e52347bdSJani Nikula should be controlled by the OSPM. 179e52347bdSJani Nikula Examples: 180e52347bdSJani Nikula 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent 181e52347bdSJani Nikula to 'acpi_osi="Windows 2000" acpi_osi=!', they all 182e52347bdSJani Nikula can make '_OSI("Windows 2000")' TRUE. 183e52347bdSJani Nikula 184e52347bdSJani Nikula 'acpi_osi=' cannot be used in combination with other 185e52347bdSJani Nikula 'acpi_osi=' command lines, the _OSI method will not 186e52347bdSJani Nikula exist in the ACPI namespace. NOTE that such command can 187e52347bdSJani Nikula only affect the _OSI support state, thus specifying it 188e52347bdSJani Nikula multiple times through kernel command line is also 189e52347bdSJani Nikula meaningless. 190e52347bdSJani Nikula Examples: 191e52347bdSJani Nikula 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' 192e52347bdSJani Nikula FALSE. 193e52347bdSJani Nikula 194e52347bdSJani Nikula 'acpi_osi=!*' can be used in combination with single or 195e52347bdSJani Nikula multiple 'acpi_osi="string1"' to support specific 196e52347bdSJani Nikula string(s). Note that such command can affect the 197e52347bdSJani Nikula current state of both the OS vendor strings and the 198e52347bdSJani Nikula feature group strings, thus specifying it multiple times 199e52347bdSJani Nikula through kernel command line is meaningful. But it may 200e52347bdSJani Nikula still not able to affect the final state of a string if 201e52347bdSJani Nikula there are quirks related to this string. This command 202e52347bdSJani Nikula is useful when one want to control the state of the 203e52347bdSJani Nikula feature group strings to debug BIOS issues related to 204e52347bdSJani Nikula the OSPM features. 205e52347bdSJani Nikula Examples: 206e52347bdSJani Nikula 1. 'acpi_osi="Module Device" acpi_osi=!*' can make 207e52347bdSJani Nikula '_OSI("Module Device")' FALSE. 208e52347bdSJani Nikula 2. 'acpi_osi=!* acpi_osi="Module Device"' can make 209e52347bdSJani Nikula '_OSI("Module Device")' TRUE. 210e52347bdSJani Nikula 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is 211e52347bdSJani Nikula equivalent to 212e52347bdSJani Nikula 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' 213e52347bdSJani Nikula and 214e52347bdSJani Nikula 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', 215e52347bdSJani Nikula they all will make '_OSI("Windows 2000")' TRUE. 216e52347bdSJani Nikula 217e52347bdSJani Nikula acpi_pm_good [X86] 218e52347bdSJani Nikula Override the pmtimer bug detection: force the kernel 219e52347bdSJani Nikula to assume that this machine's pmtimer latches its value 220e52347bdSJani Nikula and always returns good values. 221e52347bdSJani Nikula 222e52347bdSJani Nikula acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 223e52347bdSJani Nikula Format: { level | edge | high | low } 224e52347bdSJani Nikula 225e52347bdSJani Nikula acpi_skip_timer_override [HW,ACPI] 226e52347bdSJani Nikula Recognize and ignore IRQ0/pin2 Interrupt Override. 227e52347bdSJani Nikula For broken nForce2 BIOS resulting in XT-PIC timer. 228e52347bdSJani Nikula 229e52347bdSJani Nikula acpi_sleep= [HW,ACPI] Sleep options 230e52347bdSJani Nikula Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, 23157044031SRafael J. Wysocki old_ordering, nonvs, sci_force_enable, nobl } 232151f4e2bSMauro Carvalho Chehab See Documentation/power/video.rst for information on 233e52347bdSJani Nikula s3_bios and s3_mode. 234e52347bdSJani Nikula s3_beep is for debugging; it makes the PC's speaker beep 235e52347bdSJani Nikula as soon as the kernel's real-mode entry point is called. 236e52347bdSJani Nikula s4_nohwsig prevents ACPI hardware signature from being 237e52347bdSJani Nikula used during resume from hibernation. 238e52347bdSJani Nikula old_ordering causes the ACPI 1.0 ordering of the _PTS 239e52347bdSJani Nikula control method, with respect to putting devices into 240e52347bdSJani Nikula low power states, to be enforced (the ACPI 2.0 ordering 241e52347bdSJani Nikula of _PTS is used by default). 242e52347bdSJani Nikula nonvs prevents the kernel from saving/restoring the 243e52347bdSJani Nikula ACPI NVS memory during suspend/hibernation and resume. 244e52347bdSJani Nikula sci_force_enable causes the kernel to set SCI_EN directly 245e52347bdSJani Nikula on resume from S1/S3 (which is against the ACPI spec, 246e52347bdSJani Nikula but some broken systems don't work without it). 24757044031SRafael J. Wysocki nobl causes the internal blacklist of systems known to 24857044031SRafael J. Wysocki behave incorrectly in some ways with respect to system 24957044031SRafael J. Wysocki suspend and resume to be ignored (use wisely). 250e52347bdSJani Nikula 251e52347bdSJani Nikula acpi_use_timer_override [HW,ACPI] 252e52347bdSJani Nikula Use timer override. For some broken Nvidia NF5 boards 253e52347bdSJani Nikula that require a timer override, but don't have HPET 254e52347bdSJani Nikula 255e52347bdSJani Nikula add_efi_memmap [EFI; X86] Include EFI memory map in 256e52347bdSJani Nikula kernel's map of available physical RAM. 257e52347bdSJani Nikula 258e52347bdSJani Nikula agp= [AGP] 259e52347bdSJani Nikula { off | try_unsupported } 260e52347bdSJani Nikula off: disable AGP support 261e52347bdSJani Nikula try_unsupported: try to drive unsupported chipsets 262e52347bdSJani Nikula (may crash computer or cause data corruption) 263e52347bdSJani Nikula 264e52347bdSJani Nikula ALSA [HW,ALSA] 2651ca2c806SMauro Carvalho Chehab See Documentation/sound/alsa-configuration.rst 266e52347bdSJani Nikula 267e52347bdSJani Nikula alignment= [KNL,ARM] 268e52347bdSJani Nikula Allow the default userspace alignment fault handler 269e52347bdSJani Nikula behaviour to be specified. Bit 0 enables warnings, 270e52347bdSJani Nikula bit 1 enables fixups, and bit 2 sends a segfault. 271e52347bdSJani Nikula 272e52347bdSJani Nikula align_va_addr= [X86-64] 273e52347bdSJani Nikula Align virtual addresses by clearing slice [14:12] when 274e52347bdSJani Nikula allocating a VMA at process creation time. This option 275e52347bdSJani Nikula gives you up to 3% performance improvement on AMD F15h 276e52347bdSJani Nikula machines (where it is enabled by default) for a 277e52347bdSJani Nikula CPU-intensive style benchmark, and it can vary highly in 278e52347bdSJani Nikula a microbenchmark depending on workload and compiler. 279e52347bdSJani Nikula 280e52347bdSJani Nikula 32: only for 32-bit processes 281e52347bdSJani Nikula 64: only for 64-bit processes 282e52347bdSJani Nikula on: enable for both 32- and 64-bit processes 283e52347bdSJani Nikula off: disable for both 32- and 64-bit processes 284e52347bdSJani Nikula 285e52347bdSJani Nikula alloc_snapshot [FTRACE] 286e52347bdSJani Nikula Allocate the ftrace snapshot buffer on boot up when the 287e52347bdSJani Nikula main buffer is allocated. This is handy if debugging 288e52347bdSJani Nikula and you need to use tracing_snapshot() on boot up, and 289e52347bdSJani Nikula do not want to use tracing_snapshot_alloc() as it needs 290e52347bdSJani Nikula to be done where GFP_KERNEL allocations are allowed. 291e52347bdSJani Nikula 292e52347bdSJani Nikula amd_iommu= [HW,X86-64] 293e52347bdSJani Nikula Pass parameters to the AMD IOMMU driver in the system. 294e52347bdSJani Nikula Possible values are: 295e52347bdSJani Nikula fullflush - enable flushing of IO/TLB entries when 296e52347bdSJani Nikula they are unmapped. Otherwise they are 297e52347bdSJani Nikula flushed before they will be reused, which 298e52347bdSJani Nikula is a lot of faster 299e52347bdSJani Nikula off - do not initialize any AMD IOMMU found in 300e52347bdSJani Nikula the system 301e52347bdSJani Nikula force_isolation - Force device isolation for all 302e52347bdSJani Nikula devices. The IOMMU driver is not 303e52347bdSJani Nikula allowed anymore to lift isolation 304e52347bdSJani Nikula requirements as needed. This option 305e52347bdSJani Nikula does not override iommu=pt 306e52347bdSJani Nikula 307e52347bdSJani Nikula amd_iommu_dump= [HW,X86-64] 308e52347bdSJani Nikula Enable AMD IOMMU driver option to dump the ACPI table 309e52347bdSJani Nikula for AMD IOMMU. With this option enabled, AMD IOMMU 310e52347bdSJani Nikula driver will print ACPI tables for AMD IOMMU during 311e52347bdSJani Nikula IOMMU initialization. 312e52347bdSJani Nikula 313e52347bdSJani Nikula amd_iommu_intr= [HW,X86-64] 314e52347bdSJani Nikula Specifies one of the following AMD IOMMU interrupt 315e52347bdSJani Nikula remapping modes: 316e52347bdSJani Nikula legacy - Use legacy interrupt remapping mode. 317e52347bdSJani Nikula vapic - Use virtual APIC mode, which allows IOMMU 318e52347bdSJani Nikula to inject interrupts directly into guest. 319e52347bdSJani Nikula This mode requires kvm-amd.avic=1. 320e52347bdSJani Nikula (Default when IOMMU HW support is present.) 321e52347bdSJani Nikula 322e52347bdSJani Nikula amijoy.map= [HW,JOY] Amiga joystick support 323e52347bdSJani Nikula Map of devices attached to JOY0DAT and JOY1DAT 324e52347bdSJani Nikula Format: <a>,<b> 3251752118dSTom Saeger See also Documentation/input/joydev/joystick.rst 326e52347bdSJani Nikula 327e52347bdSJani Nikula analog.map= [HW,JOY] Analog joystick and gamepad support 328e52347bdSJani Nikula Specifies type or capabilities of an analog joystick 329e52347bdSJani Nikula connected to one of 16 gameports 330e52347bdSJani Nikula Format: <type1>,<type2>,..<type16> 331e52347bdSJani Nikula 332e52347bdSJani Nikula apc= [HW,SPARC] 333e52347bdSJani Nikula Power management functions (SPARCstation-4/5 + deriv.) 334e52347bdSJani Nikula Format: noidle 335e52347bdSJani Nikula Disable APC CPU standby support. SPARCstation-Fox does 336e52347bdSJani Nikula not play well with APC CPU idle - disable it if you have 337e52347bdSJani Nikula APC and your system crashes randomly. 338e52347bdSJani Nikula 33964e05d11SDou Liyang apic= [APIC,X86] Advanced Programmable Interrupt Controller 340806654a9SWill Deacon Change the output verbosity while booting 341e52347bdSJani Nikula Format: { quiet (default) | verbose | debug } 342e52347bdSJani Nikula Change the amount of debugging information output 343e52347bdSJani Nikula when initialising the APIC and IO-APIC components. 34464e05d11SDou Liyang For X86-32, this can also be used to specify an APIC 34564e05d11SDou Liyang driver name. 34664e05d11SDou Liyang Format: apic=driver_name 34764e05d11SDou Liyang Examples: apic=bigsmp 348e52347bdSJani Nikula 349e52347bdSJani Nikula apic_extnmi= [APIC,X86] External NMI delivery setting 350e52347bdSJani Nikula Format: { bsp (default) | all | none } 351e52347bdSJani Nikula bsp: External NMI is delivered only to CPU 0 352e52347bdSJani Nikula all: External NMIs are broadcast to all CPUs as a 353e52347bdSJani Nikula backup of CPU 0 354e52347bdSJani Nikula none: External NMI is masked for all CPUs. This is 355e52347bdSJani Nikula useful so that a dump capture kernel won't be 356e52347bdSJani Nikula shot down by NMI 357e52347bdSJani Nikula 358e52347bdSJani Nikula autoconf= [IPV6] 35919093313SMauro Carvalho Chehab See Documentation/networking/ipv6.rst. 360e52347bdSJani Nikula 361e52347bdSJani Nikula show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller 362e52347bdSJani Nikula Limit apic dumping. The parameter defines the maximal 363e52347bdSJani Nikula number of local apics being dumped. Also it is possible 364e52347bdSJani Nikula to set it to "all" by meaning -- no limit here. 365e52347bdSJani Nikula Format: { 1 (default) | 2 | ... | all }. 366e52347bdSJani Nikula The parameter valid if only apic=debug or 367e52347bdSJani Nikula apic=verbose is specified. 368e52347bdSJani Nikula Example: apic=debug show_lapic=all 369e52347bdSJani Nikula 370e52347bdSJani Nikula apm= [APM] Advanced Power Management 371e52347bdSJani Nikula See header of arch/x86/kernel/apm_32.c. 372e52347bdSJani Nikula 373e52347bdSJani Nikula arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 374e52347bdSJani Nikula Format: <io>,<irq>,<nodeID> 375e52347bdSJani Nikula 376e52347bdSJani Nikula ataflop= [HW,M68k] 377e52347bdSJani Nikula 378e52347bdSJani Nikula atarimouse= [HW,MOUSE] Atari Mouse 379e52347bdSJani Nikula 380e52347bdSJani Nikula atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 381e52347bdSJani Nikula EzKey and similar keyboards 382e52347bdSJani Nikula 383e52347bdSJani Nikula atkbd.reset= [HW] Reset keyboard during initialization 384e52347bdSJani Nikula 385e52347bdSJani Nikula atkbd.set= [HW] Select keyboard code set 386e52347bdSJani Nikula Format: <int> (2 = AT (default), 3 = PS/2) 387e52347bdSJani Nikula 388e52347bdSJani Nikula atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 389e52347bdSJani Nikula keyboards 390e52347bdSJani Nikula 391e52347bdSJani Nikula atkbd.softraw= [HW] Choose between synthetic and real raw mode 392e52347bdSJani Nikula Format: <bool> (0 = real, 1 = synthetic (default)) 393e52347bdSJani Nikula 394e52347bdSJani Nikula atkbd.softrepeat= [HW] 395e52347bdSJani Nikula Use software keyboard repeat 396e52347bdSJani Nikula 397e52347bdSJani Nikula audit= [KNL] Enable the audit sub-system 39811dd2666SGreg Edwards Format: { "0" | "1" | "off" | "on" } 39911dd2666SGreg Edwards 0 | off - kernel audit is disabled and can not be 40011dd2666SGreg Edwards enabled until the next reboot 401e52347bdSJani Nikula unset - kernel audit is initialized but disabled and 402e52347bdSJani Nikula will be fully enabled by the userspace auditd. 40311dd2666SGreg Edwards 1 | on - kernel audit is initialized and partially 40411dd2666SGreg Edwards enabled, storing at most audit_backlog_limit 40511dd2666SGreg Edwards messages in RAM until it is fully enabled by the 40611dd2666SGreg Edwards userspace auditd. 407e52347bdSJani Nikula Default: unset 408e52347bdSJani Nikula 409e52347bdSJani Nikula audit_backlog_limit= [KNL] Set the audit queue size limit. 410e52347bdSJani Nikula Format: <int> (must be >=0) 411e52347bdSJani Nikula Default: 64 412e52347bdSJani Nikula 413e52347bdSJani Nikula bau= [X86_UV] Enable the BAU on SGI UV. The default 414e52347bdSJani Nikula behavior is to disable the BAU (i.e. bau=0). 415e52347bdSJani Nikula Format: { "0" | "1" } 416e52347bdSJani Nikula 0 - Disable the BAU. 417e52347bdSJani Nikula 1 - Enable the BAU. 418e52347bdSJani Nikula unset - Disable the BAU. 419e52347bdSJani Nikula 420e52347bdSJani Nikula baycom_epp= [HW,AX25] 421e52347bdSJani Nikula Format: <io>,<mode> 422e52347bdSJani Nikula 423e52347bdSJani Nikula baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 424e52347bdSJani Nikula Format: <io>,<mode> 425e52347bdSJani Nikula See header of drivers/net/hamradio/baycom_par.c. 426e52347bdSJani Nikula 427e52347bdSJani Nikula baycom_ser_fdx= [HW,AX25] 428e52347bdSJani Nikula BayCom Serial Port AX.25 Modem (Full Duplex Mode) 429e52347bdSJani Nikula Format: <io>,<irq>,<mode>[,<baud>] 430e52347bdSJani Nikula See header of drivers/net/hamradio/baycom_ser_fdx.c. 431e52347bdSJani Nikula 432e52347bdSJani Nikula baycom_ser_hdx= [HW,AX25] 433e52347bdSJani Nikula BayCom Serial Port AX.25 Modem (Half Duplex Mode) 434e52347bdSJani Nikula Format: <io>,<irq>,<mode> 435e52347bdSJani Nikula See header of drivers/net/hamradio/baycom_ser_hdx.c. 436e52347bdSJani Nikula 437e52347bdSJani Nikula blkdevparts= Manual partition parsing of block device(s) for 438e52347bdSJani Nikula embedded devices based on command line input. 439898bd37aSMauro Carvalho Chehab See Documentation/block/cmdline-partition.rst 440e52347bdSJani Nikula 441e52347bdSJani Nikula boot_delay= Milliseconds to delay each printk during boot. 442e52347bdSJani Nikula Values larger than 10 seconds (10000) are changed to 443e52347bdSJani Nikula no delay (0). 444e52347bdSJani Nikula Format: integer 445e52347bdSJani Nikula 4467495e092SSteven Rostedt (VMware) bootconfig [KNL] 4477495e092SSteven Rostedt (VMware) Extended command line options can be added to an initrd 4487495e092SSteven Rostedt (VMware) and this will cause the kernel to look for it. 4497495e092SSteven Rostedt (VMware) 4507495e092SSteven Rostedt (VMware) See Documentation/admin-guide/bootconfig.rst 4517495e092SSteven Rostedt (VMware) 452e52347bdSJani Nikula bert_disable [ACPI] 453e52347bdSJani Nikula Disable BERT OS support on buggy BIOSes. 454e52347bdSJani Nikula 4551ffb8d03SAlex Hung bgrt_disable [ACPI][X86] 4561ffb8d03SAlex Hung Disable BGRT to avoid flickering OEM logo. 4571ffb8d03SAlex Hung 458e52347bdSJani Nikula bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 459e52347bdSJani Nikula bttv.radio= Most important insmod options are available as 460e52347bdSJani Nikula kernel args too. 46132e2eae2SMauro Carvalho Chehab bttv.pll= See Documentation/admin-guide/media/bttv.rst 462e52347bdSJani Nikula bttv.tuner= 463e52347bdSJani Nikula 464e52347bdSJani Nikula bulk_remove=off [PPC] This parameter disables the use of the pSeries 465e52347bdSJani Nikula firmware feature for flushing multiple hpte entries 466e52347bdSJani Nikula at a time. 467e52347bdSJani Nikula 468e52347bdSJani Nikula c101= [NET] Moxa C101 synchronous serial card 469e52347bdSJani Nikula 470e52347bdSJani Nikula cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 471e52347bdSJani Nikula Sometimes CPU hardware bugs make them report the cache 472e52347bdSJani Nikula size incorrectly. The kernel will attempt work arounds 473e52347bdSJani Nikula to fix known problems, but for some CPUs it is not 474e52347bdSJani Nikula possible to determine what the correct size should be. 475e52347bdSJani Nikula This option provides an override for these situations. 476e52347bdSJani Nikula 4773fc46fc9SMartin Kepplinger carrier_timeout= 4783fc46fc9SMartin Kepplinger [NET] Specifies amount of time (in seconds) that 4793fc46fc9SMartin Kepplinger the kernel should wait for a network carrier. By default 4803fc46fc9SMartin Kepplinger it waits 120 seconds. 4813fc46fc9SMartin Kepplinger 482e52347bdSJani Nikula ca_keys= [KEYS] This parameter identifies a specific key(s) on 483e52347bdSJani Nikula the system trusted keyring to be used for certificate 484e52347bdSJani Nikula trust validation. 485e52347bdSJani Nikula format: { id:<keyid> | builtin } 486e52347bdSJani Nikula 487e52347bdSJani Nikula cca= [MIPS] Override the kernel pages' cache coherency 488e52347bdSJani Nikula algorithm. Accepted values range from 0 to 7 489e52347bdSJani Nikula inclusive. See arch/mips/include/asm/pgtable-bits.h 490e52347bdSJani Nikula for platform specific values (SB1, Loongson3 and 491e52347bdSJani Nikula others). 492e52347bdSJani Nikula 493e52347bdSJani Nikula ccw_timeout_log [S390] 4948b4a503dSMauro Carvalho Chehab See Documentation/s390/common_io.rst for details. 495e52347bdSJani Nikula 496e52347bdSJani Nikula cgroup_disable= [KNL] Disable a particular controller 497e52347bdSJani Nikula Format: {name of the controller(s) to disable} 498e52347bdSJani Nikula The effects of cgroup_disable=foo are: 499e52347bdSJani Nikula - foo isn't auto-mounted if you mount all cgroups in 500e52347bdSJani Nikula a single hierarchy 501e52347bdSJani Nikula - foo isn't visible as an individually mountable 502e52347bdSJani Nikula subsystem 503e52347bdSJani Nikula {Currently only "memory" controller deal with this and 504e52347bdSJani Nikula cut the overhead, others just disable the usage. So 505e52347bdSJani Nikula only cgroup_disable=memory is actually worthy} 506e52347bdSJani Nikula 5073fc9c12dSTejun Heo cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1 5083fc9c12dSTejun Heo Format: { { controller | "all" | "named" } 5093fc9c12dSTejun Heo [,{ controller | "all" | "named" }...] } 510e52347bdSJani Nikula Like cgroup_disable, but only applies to cgroup v1; 511e52347bdSJani Nikula the blacklisted controllers remain available in cgroup2. 5123fc9c12dSTejun Heo "all" blacklists all controllers and "named" disables 5133fc9c12dSTejun Heo named mounts. Specifying both "all" and "named" disables 5143fc9c12dSTejun Heo all v1 hierarchies. 515e52347bdSJani Nikula 516e52347bdSJani Nikula cgroup.memory= [KNL] Pass options to the cgroup memory controller. 517e52347bdSJani Nikula Format: <string> 518e52347bdSJani Nikula nosocket -- Disable socket memory accounting. 519e52347bdSJani Nikula nokmem -- Disable kernel memory accounting. 520e52347bdSJani Nikula 521e52347bdSJani Nikula checkreqprot [SELINUX] Set initial checkreqprot flag value. 522e52347bdSJani Nikula Format: { "0" | "1" } 523e52347bdSJani Nikula See security/selinux/Kconfig help text. 524e52347bdSJani Nikula 0 -- check protection applied by kernel (includes 525e52347bdSJani Nikula any implied execute protection). 526e52347bdSJani Nikula 1 -- check protection requested by application. 527e52347bdSJani Nikula Default value is set via a kernel config option. 528e52347bdSJani Nikula Value can be changed at runtime via 529d41415ebSStephen Smalley /sys/fs/selinux/checkreqprot. 530e9c38f9fSStephen Smalley Setting checkreqprot to 1 is deprecated. 531e52347bdSJani Nikula 532e52347bdSJani Nikula cio_ignore= [S390] 5338b4a503dSMauro Carvalho Chehab See Documentation/s390/common_io.rst for details. 534e52347bdSJani Nikula clk_ignore_unused 535e52347bdSJani Nikula [CLK] 536e52347bdSJani Nikula Prevents the clock framework from automatically gating 537e52347bdSJani Nikula clocks that have not been explicitly enabled by a Linux 538e52347bdSJani Nikula device driver but are enabled in hardware at reset or 539e52347bdSJani Nikula by the bootloader/firmware. Note that this does not 540e52347bdSJani Nikula force such clocks to be always-on nor does it reserve 541e52347bdSJani Nikula those clocks in any way. This parameter is useful for 542e52347bdSJani Nikula debug and development, but should not be needed on a 543e52347bdSJani Nikula platform with proper driver support. For more 54418bcaa4eSMauro Carvalho Chehab information, see Documentation/driver-api/clk.rst. 545e52347bdSJani Nikula 546e52347bdSJani Nikula clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 547e52347bdSJani Nikula [Deprecated] 548e52347bdSJani Nikula Forces specified clocksource (if available) to be used 549e52347bdSJani Nikula when calculating gettimeofday(). If specified 550e52347bdSJani Nikula clocksource is not available, it defaults to PIT. 551e52347bdSJani Nikula Format: { pit | tsc | cyclone | pmtmr } 552e52347bdSJani Nikula 553e52347bdSJani Nikula clocksource= Override the default clocksource 554e52347bdSJani Nikula Format: <string> 555e52347bdSJani Nikula Override the default clocksource and use the clocksource 556e52347bdSJani Nikula with the name specified. 557e52347bdSJani Nikula Some clocksource names to choose from, depending on 558e52347bdSJani Nikula the platform: 559e52347bdSJani Nikula [all] jiffies (this is the base, fallback clocksource) 560e52347bdSJani Nikula [ACPI] acpi_pm 561e52347bdSJani Nikula [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 562e52347bdSJani Nikula pxa_timer,timer3,32k_counter,timer0_1 563e52347bdSJani Nikula [X86-32] pit,hpet,tsc; 564e52347bdSJani Nikula scx200_hrt on Geode; cyclone on IBM x440 565e52347bdSJani Nikula [MIPS] MIPS 566e52347bdSJani Nikula [PARISC] cr16 567e52347bdSJani Nikula [S390] tod 568e52347bdSJani Nikula [SH] SuperH 569e52347bdSJani Nikula [SPARC64] tick 570e52347bdSJani Nikula [X86-64] hpet,tsc 571e52347bdSJani Nikula 572e52347bdSJani Nikula clocksource.arm_arch_timer.evtstrm= 573e52347bdSJani Nikula [ARM,ARM64] 574e52347bdSJani Nikula Format: <bool> 575e52347bdSJani Nikula Enable/disable the eventstream feature of the ARM 576e52347bdSJani Nikula architected timer so that code using WFE-based polling 577e52347bdSJani Nikula loops can be debugged more effectively on production 578e52347bdSJani Nikula systems. 579e52347bdSJani Nikula 580e52347bdSJani Nikula clearcpuid=BITNUM [X86] 581e52347bdSJani Nikula Disable CPUID feature X for the kernel. See 582e52347bdSJani Nikula arch/x86/include/asm/cpufeatures.h for the valid bit 583e52347bdSJani Nikula numbers. Note the Linux specific bits are not necessarily 584e52347bdSJani Nikula stable over kernel options, but the vendor specific 585e52347bdSJani Nikula ones should be. 586e52347bdSJani Nikula Also note that user programs calling CPUID directly 587e52347bdSJani Nikula or using the feature without checking anything 588e52347bdSJani Nikula will still see it. This just prevents it from 589e52347bdSJani Nikula being used by the kernel or shown in /proc/cpuinfo. 590e52347bdSJani Nikula Also note the kernel might malfunction if you disable 591e52347bdSJani Nikula some critical bits. 592e52347bdSJani Nikula 593e52347bdSJani Nikula cma=nn[MG]@[start[MG][-end[MG]]] 594e52347bdSJani Nikula [ARM,X86,KNL] 595e52347bdSJani Nikula Sets the size of kernel global memory area for 596e52347bdSJani Nikula contiguous memory allocations and optionally the 597e52347bdSJani Nikula placement constraint by the physical address range of 598e52347bdSJani Nikula memory allocations. A value of 0 disables CMA 599e52347bdSJani Nikula altogether. For more information, see 600e52347bdSJani Nikula include/linux/dma-contiguous.h 601e52347bdSJani Nikula 602e52347bdSJani Nikula cmo_free_hint= [PPC] Format: { yes | no } 603e52347bdSJani Nikula Specify whether pages are marked as being inactive 604e52347bdSJani Nikula when they are freed. This is used in CMO environments 605e52347bdSJani Nikula to determine OS memory pressure for page stealing by 606e52347bdSJani Nikula a hypervisor. 607e52347bdSJani Nikula Default: yes 608e52347bdSJani Nikula 609e52347bdSJani Nikula coherent_pool=nn[KMG] [ARM,KNL] 610e52347bdSJani Nikula Sets the size of memory pool for coherent, atomic dma 611e52347bdSJani Nikula allocations, by default set to 256K. 612e52347bdSJani Nikula 613e52347bdSJani Nikula com20020= [HW,NET] ARCnet - COM20020 chipset 614e52347bdSJani Nikula Format: 615e52347bdSJani Nikula <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 616e52347bdSJani Nikula 617e52347bdSJani Nikula com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 618e52347bdSJani Nikula Format: <io>[,<irq>] 619e52347bdSJani Nikula 620e52347bdSJani Nikula com90xx= [HW,NET] 621e52347bdSJani Nikula ARCnet - COM90xx chipset (memory-mapped buffers) 622e52347bdSJani Nikula Format: <io>[,<irq>[,<memstart>]] 623e52347bdSJani Nikula 624e52347bdSJani Nikula condev= [HW,S390] console device 625e52347bdSJani Nikula conmode= 626e52347bdSJani Nikula 627e52347bdSJani Nikula console= [KNL] Output console device and options. 628e52347bdSJani Nikula 629e52347bdSJani Nikula tty<n> Use the virtual console device <n>. 630e52347bdSJani Nikula 631e52347bdSJani Nikula ttyS<n>[,options] 632e52347bdSJani Nikula ttyUSB0[,options] 633e52347bdSJani Nikula Use the specified serial port. The options are of 634e52347bdSJani Nikula the form "bbbbpnf", where "bbbb" is the baud rate, 635e52347bdSJani Nikula "p" is parity ("n", "o", or "e"), "n" is number of 636e52347bdSJani Nikula bits, and "f" is flow control ("r" for RTS or 637e52347bdSJani Nikula omit it). Default is "9600n8". 638e52347bdSJani Nikula 639e52347bdSJani Nikula See Documentation/admin-guide/serial-console.rst for more 640e52347bdSJani Nikula information. See 641d9d6ef25SMauro Carvalho Chehab Documentation/networking/netconsole.rst for an 642e52347bdSJani Nikula alternative. 643e52347bdSJani Nikula 644e52347bdSJani Nikula uart[8250],io,<addr>[,options] 645e52347bdSJani Nikula uart[8250],mmio,<addr>[,options] 646e52347bdSJani Nikula uart[8250],mmio16,<addr>[,options] 647e52347bdSJani Nikula uart[8250],mmio32,<addr>[,options] 648e52347bdSJani Nikula uart[8250],0x<addr>[,options] 649e52347bdSJani Nikula Start an early, polled-mode console on the 8250/16550 650e52347bdSJani Nikula UART at the specified I/O port or MMIO address, 651e52347bdSJani Nikula switching to the matching ttyS device later. 652e52347bdSJani Nikula MMIO inter-register address stride is either 8-bit 653e52347bdSJani Nikula (mmio), 16-bit (mmio16), or 32-bit (mmio32). 654e52347bdSJani Nikula If none of [io|mmio|mmio16|mmio32], <addr> is assumed 655e52347bdSJani Nikula to be equivalent to 'mmio'. 'options' are specified in 656e52347bdSJani Nikula the same format described for ttyS above; if unspecified, 657e52347bdSJani Nikula the h/w is not re-initialized. 658e52347bdSJani Nikula 659e52347bdSJani Nikula hvc<n> Use the hypervisor console device <n>. This is for 660e52347bdSJani Nikula both Xen and PowerPC hypervisors. 661e52347bdSJani Nikula 662e52347bdSJani Nikula If the device connected to the port is not a TTY but a braille 663e52347bdSJani Nikula device, prepend "brl," before the device type, for instance 664e52347bdSJani Nikula console=brl,ttyS0 665e52347bdSJani Nikula For now, only VisioBraille is supported. 666e52347bdSJani Nikula 667cca10d58SSergey Senozhatsky console_msg_format= 668cca10d58SSergey Senozhatsky [KNL] Change console messages format 669cca10d58SSergey Senozhatsky default 670cca10d58SSergey Senozhatsky By default we print messages on consoles in 671cca10d58SSergey Senozhatsky "[time stamp] text\n" format (time stamp may not be 672cca10d58SSergey Senozhatsky printed, depending on CONFIG_PRINTK_TIME or 673cca10d58SSergey Senozhatsky `printk_time' param). 674cca10d58SSergey Senozhatsky syslog 675cca10d58SSergey Senozhatsky Switch to syslog format: "<%u>[time stamp] text\n" 676cca10d58SSergey Senozhatsky IOW, each message will have a facility and loglevel 677cca10d58SSergey Senozhatsky prefix. The format is similar to one used by syslog() 678cca10d58SSergey Senozhatsky syscall, or to executing "dmesg -S --raw" or to reading 679cca10d58SSergey Senozhatsky from /proc/kmsg. 680cca10d58SSergey Senozhatsky 681e52347bdSJani Nikula consoleblank= [KNL] The console blank (screen saver) timeout in 682ac0a314cSDaniel Xu seconds. A value of 0 disables the blank timer. 683ac0a314cSDaniel Xu Defaults to 0. 684e52347bdSJani Nikula 685e52347bdSJani Nikula coredump_filter= 686e52347bdSJani Nikula [KNL] Change the default value for 687e52347bdSJani Nikula /proc/<pid>/coredump_filter. 688cd4ca341SJimmy Assarsson See also Documentation/filesystems/proc.rst. 689e52347bdSJani Nikula 69062a31ce1SLeo Yan coresight_cpu_debug.enable 69162a31ce1SLeo Yan [ARM,ARM64] 69262a31ce1SLeo Yan Format: <bool> 69362a31ce1SLeo Yan Enable/disable the CPU sampling based debugging. 69462a31ce1SLeo Yan 0: default value, disable debugging 69562a31ce1SLeo Yan 1: enable debugging at boot time 69662a31ce1SLeo Yan 697e52347bdSJani Nikula cpuidle.off=1 [CPU_IDLE] 698e52347bdSJani Nikula disable the cpuidle sub-system 699e52347bdSJani Nikula 70061cb5758SRafael J. Wysocki cpuidle.governor= 70161cb5758SRafael J. Wysocki [CPU_IDLE] Name of the cpuidle governor to use. 70261cb5758SRafael J. Wysocki 703d82f2692SLen Brown cpufreq.off=1 [CPU_FREQ] 704d82f2692SLen Brown disable the cpufreq sub-system 705d82f2692SLen Brown 706e52347bdSJani Nikula cpu_init_udelay=N 707e52347bdSJani Nikula [X86] Delay for N microsec between assert and de-assert 708e52347bdSJani Nikula of APIC INIT to start processors. This delay occurs 709e52347bdSJani Nikula on every CPU online, such as boot, and resume from suspend. 710e52347bdSJani Nikula Default: 10000 711e52347bdSJani Nikula 712e52347bdSJani Nikula cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 713e52347bdSJani Nikula Format: 714e52347bdSJani Nikula <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 715e52347bdSJani Nikula 716e52347bdSJani Nikula crashkernel=size[KMG][@offset[KMG]] 717e52347bdSJani Nikula [KNL] Using kexec, Linux can switch to a 'crash kernel' 718e52347bdSJani Nikula upon panic. This parameter reserves the physical 719e52347bdSJani Nikula memory region [offset, offset + size] for that kernel 720e52347bdSJani Nikula image. If '@offset' is omitted, then a suitable offset 721b9ac3849SDave Young is selected automatically. 722b9ac3849SDave Young [KNL, x86_64] select a region under 4G first, and 723b9ac3849SDave Young fall back to reserve region above 4G when '@offset' 724b9ac3849SDave Young hasn't been specified. 725330d4810SMauro Carvalho Chehab See Documentation/admin-guide/kdump/kdump.rst for further details. 726e52347bdSJani Nikula 727e52347bdSJani Nikula crashkernel=range1:size1[,range2:size2,...][@offset] 728e52347bdSJani Nikula [KNL] Same as above, but depends on the memory 729e52347bdSJani Nikula in the running system. The syntax of range is 730e52347bdSJani Nikula start-[end] where start and end are both 731e52347bdSJani Nikula a memory unit (amount[KMG]). See also 732330d4810SMauro Carvalho Chehab Documentation/admin-guide/kdump/kdump.rst for an example. 733e52347bdSJani Nikula 734e52347bdSJani Nikula crashkernel=size[KMG],high 735e52347bdSJani Nikula [KNL, x86_64] range could be above 4G. Allow kernel 736e52347bdSJani Nikula to allocate physical memory region from top, so could 737e52347bdSJani Nikula be above 4G if system have more than 4G ram installed. 738e52347bdSJani Nikula Otherwise memory region will be allocated below 4G, if 739e52347bdSJani Nikula available. 740e52347bdSJani Nikula It will be ignored if crashkernel=X is specified. 741e52347bdSJani Nikula crashkernel=size[KMG],low 742e52347bdSJani Nikula [KNL, x86_64] range under 4G. When crashkernel=X,high 743e52347bdSJani Nikula is passed, kernel could allocate physical memory region 744e52347bdSJani Nikula above 4G, that cause second kernel crash on system 745e52347bdSJani Nikula that require some amount of low memory, e.g. swiotlb 746e52347bdSJani Nikula requires at least 64M+32K low memory, also enough extra 747e52347bdSJani Nikula low memory is needed to make sure DMA buffers for 32-bit 748e52347bdSJani Nikula devices won't run out. Kernel would try to allocate at 749e52347bdSJani Nikula at least 256M below 4G automatically. 750e52347bdSJani Nikula This one let user to specify own low range under 4G 751e52347bdSJani Nikula for second kernel instead. 752e52347bdSJani Nikula 0: to disable low allocation. 753e52347bdSJani Nikula It will be ignored when crashkernel=X,high is not used 754e52347bdSJani Nikula or memory reserved is below 4G. 755e52347bdSJani Nikula 756e52347bdSJani Nikula cryptomgr.notests 757e52347bdSJani Nikula [KNL] Disable crypto self-tests 758e52347bdSJani Nikula 759e52347bdSJani Nikula cs89x0_dma= [HW,NET] 760e52347bdSJani Nikula Format: <dma> 761e52347bdSJani Nikula 762e52347bdSJani Nikula cs89x0_media= [HW,NET] 763e52347bdSJani Nikula Format: { rj45 | aui | bnc } 764e52347bdSJani Nikula 765e52347bdSJani Nikula dasd= [HW,NET] 766e52347bdSJani Nikula See header of drivers/s390/block/dasd_devmap.c. 767e52347bdSJani Nikula 768e52347bdSJani Nikula db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 769e52347bdSJani Nikula (one device per port) 770e52347bdSJani Nikula Format: <port#>,<type> 7711752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 772e52347bdSJani Nikula 773e52347bdSJani Nikula ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot 774787e3075SSteffen Maier time. See 775787e3075SSteffen Maier Documentation/admin-guide/dynamic-debug-howto.rst for 776e52347bdSJani Nikula details. Deprecated, see dyndbg. 777e52347bdSJani Nikula 778e52347bdSJani Nikula debug [KNL] Enable kernel debugging (events log level). 779e52347bdSJani Nikula 7803672476eSTobin C. Harding debug_boot_weak_hash 7813672476eSTobin C. Harding [KNL] Enable printing [hashed] pointers early in the 7823672476eSTobin C. Harding boot sequence. If enabled, we use a weak hash instead 7833672476eSTobin C. Harding of siphash to hash pointers. Use this option if you are 7843672476eSTobin C. Harding seeing instances of '(___ptrval___)') and need to see a 7853672476eSTobin C. Harding value (hashed pointer) instead. Cryptographically 7863672476eSTobin C. Harding insecure, please do not use on production kernels. 7873672476eSTobin C. Harding 788e52347bdSJani Nikula debug_locks_verbose= 789e52347bdSJani Nikula [KNL] verbose self-tests 790e52347bdSJani Nikula Format=<0|1> 791e52347bdSJani Nikula Print debugging info while doing the locking API 792e52347bdSJani Nikula self-tests. 793e52347bdSJani Nikula We default to 0 (no extra messages), setting it to 794e52347bdSJani Nikula 1 will print _a lot_ more information - normally 795e52347bdSJani Nikula only useful to kernel developers. 796e52347bdSJani Nikula 797e52347bdSJani Nikula debug_objects [KNL] Enable object debugging 798e52347bdSJani Nikula 799e52347bdSJani Nikula no_debug_objects 800e52347bdSJani Nikula [KNL] Disable object debugging 801e52347bdSJani Nikula 802e52347bdSJani Nikula debug_guardpage_minorder= 803e52347bdSJani Nikula [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this 804e52347bdSJani Nikula parameter allows control of the order of pages that will 805e52347bdSJani Nikula be intentionally kept free (and hence protected) by the 806e52347bdSJani Nikula buddy allocator. Bigger value increase the probability 807e52347bdSJani Nikula of catching random memory corruption, but reduce the 808e52347bdSJani Nikula amount of memory for normal system use. The maximum 809e52347bdSJani Nikula possible value is MAX_ORDER/2. Setting this parameter 810e52347bdSJani Nikula to 1 or 2 should be enough to identify most random 811e52347bdSJani Nikula memory corruption problems caused by bugs in kernel or 812e52347bdSJani Nikula driver code when a CPU writes to (or reads from) a 813e52347bdSJani Nikula random memory location. Note that there exists a class 814e52347bdSJani Nikula of memory corruptions problems caused by buggy H/W or 815e52347bdSJani Nikula F/W or by drivers badly programing DMA (basically when 816e52347bdSJani Nikula memory is written at bus level and the CPU MMU is 817e52347bdSJani Nikula bypassed) which are not detectable by 818e52347bdSJani Nikula CONFIG_DEBUG_PAGEALLOC, hence this option will not help 819e52347bdSJani Nikula tracking down these problems. 820e52347bdSJani Nikula 821e52347bdSJani Nikula debug_pagealloc= 8223972f6bbSVlastimil Babka [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter 8233972f6bbSVlastimil Babka enables the feature at boot time. By default, it is 8243972f6bbSVlastimil Babka disabled and the system will work mostly the same as a 8253972f6bbSVlastimil Babka kernel built without CONFIG_DEBUG_PAGEALLOC. 8268974558fSVlastimil Babka Note: to get most of debug_pagealloc error reports, it's 8278974558fSVlastimil Babka useful to also enable the page_owner functionality. 828e52347bdSJani Nikula on: enable the feature 829e52347bdSJani Nikula 830e52347bdSJani Nikula debugpat [X86] Enable PAT debugging 831e52347bdSJani Nikula 832e52347bdSJani Nikula decnet.addr= [HW,NET] 833e52347bdSJani Nikula Format: <area>[,<node>] 8349a69fb9cSMauro Carvalho Chehab See also Documentation/networking/decnet.rst. 835e52347bdSJani Nikula 836e52347bdSJani Nikula default_hugepagesz= 837282f4214SMike Kravetz [HW] The size of the default HugeTLB page. This is 838282f4214SMike Kravetz the size represented by the legacy /proc/ hugepages 839282f4214SMike Kravetz APIs. In addition, this is the default hugetlb size 840282f4214SMike Kravetz used for shmget(), mmap() and mounting hugetlbfs 841282f4214SMike Kravetz filesystems. If not specified, defaults to the 842282f4214SMike Kravetz architecture's default huge page size. Huge page 843282f4214SMike Kravetz sizes are architecture dependent. See also 844282f4214SMike Kravetz Documentation/admin-guide/mm/hugetlbpage.rst. 845282f4214SMike Kravetz Format: size[KMG] 846e52347bdSJani Nikula 84725b4e70dSRob Herring deferred_probe_timeout= 84825b4e70dSRob Herring [KNL] Debugging option to set a timeout in seconds for 84925b4e70dSRob Herring deferred probe to give up waiting on dependencies to 85025b4e70dSRob Herring probe. Only specific dependencies (subsystems or 85125b4e70dSRob Herring drivers) that have opted in will be ignored. A timeout of 0 85225b4e70dSRob Herring will timeout at the end of initcalls. This option will also 85325b4e70dSRob Herring dump out devices still on the deferred probe list after 85425b4e70dSRob Herring retrying. 85525b4e70dSRob Herring 856c65e6815SMikhail Zaslonko dfltcc= [HW,S390] 857c65e6815SMikhail Zaslonko Format: { on | off | def_only | inf_only | always } 858c65e6815SMikhail Zaslonko on: s390 zlib hardware support for compression on 859c65e6815SMikhail Zaslonko level 1 and decompression (default) 860c65e6815SMikhail Zaslonko off: No s390 zlib hardware support 861c65e6815SMikhail Zaslonko def_only: s390 zlib hardware support for deflate 862c65e6815SMikhail Zaslonko only (compression on level 1) 863c65e6815SMikhail Zaslonko inf_only: s390 zlib hardware support for inflate 864c65e6815SMikhail Zaslonko only (decompression) 865c65e6815SMikhail Zaslonko always: Same as 'on' but ignores the selected compression 866c65e6815SMikhail Zaslonko level always using hardware support (used for debugging) 867c65e6815SMikhail Zaslonko 868e52347bdSJani Nikula dhash_entries= [KNL] 869e52347bdSJani Nikula Set number of hash buckets for dentry cache. 870e52347bdSJani Nikula 871e52347bdSJani Nikula disable_1tb_segments [PPC] 872e52347bdSJani Nikula Disables the use of 1TB hash page table segments. This 873e52347bdSJani Nikula causes the kernel to fall back to 256MB segments which 874e52347bdSJani Nikula can be useful when debugging issues that require an SLB 875e52347bdSJani Nikula miss to occur. 876e52347bdSJani Nikula 87782a1b8edSNicholas Piggin stress_slb [PPC] 87882a1b8edSNicholas Piggin Limits the number of kernel SLB entries, and flushes 87982a1b8edSNicholas Piggin them frequently to increase the rate of SLB faults 88082a1b8edSNicholas Piggin on kernel addresses. 88182a1b8edSNicholas Piggin 882e52347bdSJani Nikula disable= [IPV6] 88319093313SMauro Carvalho Chehab See Documentation/networking/ipv6.rst. 884e52347bdSJani Nikula 885b5cb15d9SChris von Recklinghausen hardened_usercopy= 886b5cb15d9SChris von Recklinghausen [KNL] Under CONFIG_HARDENED_USERCOPY, whether 887b5cb15d9SChris von Recklinghausen hardening is enabled for this boot. Hardened 888b5cb15d9SChris von Recklinghausen usercopy checking is used to protect the kernel 889b5cb15d9SChris von Recklinghausen from reading or writing beyond known memory 890b5cb15d9SChris von Recklinghausen allocation boundaries as a proactive defense 891b5cb15d9SChris von Recklinghausen against bounds-checking flaws in the kernel's 892b5cb15d9SChris von Recklinghausen copy_to_user()/copy_from_user() interface. 893b5cb15d9SChris von Recklinghausen on Perform hardened usercopy checks (default). 894b5cb15d9SChris von Recklinghausen off Disable hardened usercopy checks. 895b5cb15d9SChris von Recklinghausen 896e52347bdSJani Nikula disable_radix [PPC] 897e52347bdSJani Nikula Disable RADIX MMU mode on POWER9 898e52347bdSJani Nikula 899bf6b7661SAneesh Kumar K.V radix_hcall_invalidate=on [PPC/PSERIES] 900bf6b7661SAneesh Kumar K.V Disable RADIX GTSE feature and use hcall for TLB 901bf6b7661SAneesh Kumar K.V invalidate. 902bf6b7661SAneesh Kumar K.V 9032275d7b5SNicholas Piggin disable_tlbie [PPC] 9042275d7b5SNicholas Piggin Disable TLBIE instruction. Currently does not work 9052275d7b5SNicholas Piggin with KVM, with HASH MMU, or with coherent accelerators. 9062275d7b5SNicholas Piggin 907e52347bdSJani Nikula disable_cpu_apicid= [X86,APIC,SMP] 908e52347bdSJani Nikula Format: <int> 909e52347bdSJani Nikula The number of initial APIC ID for the 910e52347bdSJani Nikula corresponding CPU to be disabled at boot, 911e52347bdSJani Nikula mostly used for the kdump 2nd kernel to 912e52347bdSJani Nikula disable BSP to wake up multiple CPUs without 913e52347bdSJani Nikula causing system reset or hang due to sending 914e52347bdSJani Nikula INIT from AP to BSP. 915e52347bdSJani Nikula 9162a5bf23dSPeter Zijlstra perf_v4_pmi= [X86,INTEL] 9172a5bf23dSPeter Zijlstra Format: <bool> 918af3bdb99SAndi Kleen Disable Intel PMU counter freezing feature. 919af3bdb99SAndi Kleen The feature only exists starting from 920af3bdb99SAndi Kleen Arch Perfmon v4 (Skylake and newer). 921af3bdb99SAndi Kleen 922e52347bdSJani Nikula disable_ddw [PPC/PSERIES] 923e52347bdSJani Nikula Disable Dynamic DMA Window support. Use this if 924e52347bdSJani Nikula to workaround buggy firmware. 925e52347bdSJani Nikula 926e52347bdSJani Nikula disable_ipv6= [IPV6] 92719093313SMauro Carvalho Chehab See Documentation/networking/ipv6.rst. 928e52347bdSJani Nikula 929e52347bdSJani Nikula disable_mtrr_cleanup [X86] 930e52347bdSJani Nikula The kernel tries to adjust MTRR layout from continuous 931e52347bdSJani Nikula to discrete, to make X server driver able to add WB 932e52347bdSJani Nikula entry later. This parameter disables that. 933e52347bdSJani Nikula 934e52347bdSJani Nikula disable_mtrr_trim [X86, Intel and AMD only] 935e52347bdSJani Nikula By default the kernel will trim any uncacheable 936e52347bdSJani Nikula memory out of your available memory pool based on 937e52347bdSJani Nikula MTRR settings. This parameter disables that behavior, 938e52347bdSJani Nikula possibly causing your machine to run very slowly. 939e52347bdSJani Nikula 940e52347bdSJani Nikula disable_timer_pin_1 [X86] 941e52347bdSJani Nikula Disable PIN 1 of APIC timer 942e52347bdSJani Nikula Can be useful to work around chipset bugs. 943e52347bdSJani Nikula 944e52347bdSJani Nikula dis_ucode_ldr [X86] Disable the microcode loader. 945e52347bdSJani Nikula 946e52347bdSJani Nikula dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, 947e52347bdSJani Nikula this option disables the debugging code at boot. 948e52347bdSJani Nikula 949e52347bdSJani Nikula dma_debug_entries=<number> 950e52347bdSJani Nikula This option allows to tune the number of preallocated 951e52347bdSJani Nikula entries for DMA-API debugging code. One entry is 952e52347bdSJani Nikula required per DMA-API allocation. Use this if the 953e52347bdSJani Nikula DMA-API debugging code disables itself because the 954e52347bdSJani Nikula architectural default is too low. 955e52347bdSJani Nikula 956e52347bdSJani Nikula dma_debug_driver=<driver_name> 957e52347bdSJani Nikula With this option the DMA-API debugging driver 958e52347bdSJani Nikula filter feature can be enabled at boot time. Just 959e52347bdSJani Nikula pass the driver to filter for as the parameter. 960e52347bdSJani Nikula The filter can be disabled or changed to another 961e52347bdSJani Nikula driver later using sysfs. 962e52347bdSJani Nikula 9631ea61b68SFeng Tang driver_async_probe= [KNL] 9641ea61b68SFeng Tang List of driver names to be probed asynchronously. 9651ea61b68SFeng Tang Format: <driver_name1>,<driver_name2>... 9661ea61b68SFeng Tang 96753fd40a9SJani Nikula drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] 968e52347bdSJani Nikula Broken monitors, graphic adapters, KVMs and EDIDless 969e52347bdSJani Nikula panels may send no or incorrect EDID data sets. 970e52347bdSJani Nikula This parameter allows to specify an EDID data sets 971e52347bdSJani Nikula in the /lib/firmware directory that are used instead. 972e52347bdSJani Nikula Generic built-in EDID data sets are used, if one of 973e52347bdSJani Nikula edid/1024x768.bin, edid/1280x1024.bin, 974e52347bdSJani Nikula edid/1680x1050.bin, or edid/1920x1080.bin is given 975e52347bdSJani Nikula and no file with the same name exists. Details and 976e52347bdSJani Nikula instructions how to build your own EDID data are 977cd4ca341SJimmy Assarsson available in Documentation/admin-guide/edid.rst. An EDID 978e52347bdSJani Nikula data set will only be used for a particular connector, 979e52347bdSJani Nikula if its name and a colon are prepended to the EDID 980e52347bdSJani Nikula name. Each connector may use a unique EDID data 981e52347bdSJani Nikula set by separating the files with a comma. An EDID 982e52347bdSJani Nikula data set with no connector name will be used for 983e52347bdSJani Nikula any connectors not explicitly specified. 984e52347bdSJani Nikula 985e52347bdSJani Nikula dscc4.setup= [NET] 986e52347bdSJani Nikula 987a2b05b7aSNicholas Piggin dt_cpu_ftrs= [PPC] 988a2b05b7aSNicholas Piggin Format: {"off" | "known"} 989a2b05b7aSNicholas Piggin Control how the dt_cpu_ftrs device-tree binding is 990a2b05b7aSNicholas Piggin used for CPU feature discovery and setup (if it 991a2b05b7aSNicholas Piggin exists). 992a2b05b7aSNicholas Piggin off: Do not use it, fall back to legacy cpu table. 993a2b05b7aSNicholas Piggin known: Do not pass through unknown features to guests 994a2b05b7aSNicholas Piggin or userspace, only those that the kernel is aware of. 995a2b05b7aSNicholas Piggin 996e7aa8c2eSLinus Torvalds dump_apple_properties [X86] 997e7aa8c2eSLinus Torvalds Dump name and content of EFI device properties on 998e7aa8c2eSLinus Torvalds x86 Macs. Useful for driver authors to determine 999e7aa8c2eSLinus Torvalds what data is available or for reverse-engineering. 1000e7aa8c2eSLinus Torvalds 1001e52347bdSJani Nikula dyndbg[="val"] [KNL,DYNAMIC_DEBUG] 1002e52347bdSJani Nikula module.dyndbg[="val"] 1003e52347bdSJani Nikula Enable debug messages at boot time. See 1004787e3075SSteffen Maier Documentation/admin-guide/dynamic-debug-howto.rst 1005787e3075SSteffen Maier for details. 1006e52347bdSJani Nikula 1007e52347bdSJani Nikula nopku [X86] Disable Memory Protection Keys CPU feature found 1008e52347bdSJani Nikula in some Intel CPUs. 1009e52347bdSJani Nikula 1010e52347bdSJani Nikula module.async_probe [KNL] 1011e52347bdSJani Nikula Enable asynchronous probe on this module. 1012e52347bdSJani Nikula 1013e52347bdSJani Nikula early_ioremap_debug [KNL] 1014e52347bdSJani Nikula Enable debug messages in early_ioremap support. This 1015e52347bdSJani Nikula is useful for tracking down temporary early mappings 1016e52347bdSJani Nikula which are not unmapped. 1017e52347bdSJani Nikula 1018e52347bdSJani Nikula earlycon= [KNL] Output early console device and options. 1019e52347bdSJani Nikula 1020e18409c0SChristoph Hellwig When used with no options, the early console is 1021e18409c0SChristoph Hellwig determined by stdout-path property in device tree's 1022e18409c0SChristoph Hellwig chosen node or the ACPI SPCR table if supported by 1023e18409c0SChristoph Hellwig the platform. 1024e52347bdSJani Nikula 1025e52347bdSJani Nikula cdns,<addr>[,options] 1026e52347bdSJani Nikula Start an early, polled-mode console on a Cadence 1027e52347bdSJani Nikula (xuartps) serial port at the specified address. Only 1028e52347bdSJani Nikula supported option is baud rate. If baud rate is not 1029e52347bdSJani Nikula specified, the serial port must already be setup and 1030e52347bdSJani Nikula configured. 1031e52347bdSJani Nikula 1032e52347bdSJani Nikula uart[8250],io,<addr>[,options] 1033e52347bdSJani Nikula uart[8250],mmio,<addr>[,options] 1034e52347bdSJani Nikula uart[8250],mmio32,<addr>[,options] 1035e52347bdSJani Nikula uart[8250],mmio32be,<addr>[,options] 1036e52347bdSJani Nikula uart[8250],0x<addr>[,options] 1037e52347bdSJani Nikula Start an early, polled-mode console on the 8250/16550 1038e52347bdSJani Nikula UART at the specified I/O port or MMIO address. 1039e52347bdSJani Nikula MMIO inter-register address stride is either 8-bit 1040e52347bdSJani Nikula (mmio) or 32-bit (mmio32 or mmio32be). 1041e52347bdSJani Nikula If none of [io|mmio|mmio32|mmio32be], <addr> is assumed 1042e52347bdSJani Nikula to be equivalent to 'mmio'. 'options' are specified 1043e52347bdSJani Nikula in the same format described for "console=ttyS<n>"; if 1044e52347bdSJani Nikula unspecified, the h/w is not initialized. 1045e52347bdSJani Nikula 1046e52347bdSJani Nikula pl011,<addr> 1047e52347bdSJani Nikula pl011,mmio32,<addr> 1048e52347bdSJani Nikula Start an early, polled-mode console on a pl011 serial 1049e52347bdSJani Nikula port at the specified address. The pl011 serial port 1050e52347bdSJani Nikula must already be setup and configured. Options are not 1051e52347bdSJani Nikula yet supported. If 'mmio32' is specified, then only 1052e52347bdSJani Nikula the driver will use only 32-bit accessors to read/write 1053e52347bdSJani Nikula the device registers. 1054e52347bdSJani Nikula 1055e52347bdSJani Nikula meson,<addr> 1056e52347bdSJani Nikula Start an early, polled-mode console on a meson serial 1057e52347bdSJani Nikula port at the specified address. The serial port must 1058e52347bdSJani Nikula already be setup and configured. Options are not yet 1059e52347bdSJani Nikula supported. 1060e52347bdSJani Nikula 1061e52347bdSJani Nikula msm_serial,<addr> 1062e52347bdSJani Nikula Start an early, polled-mode console on an msm serial 1063e52347bdSJani Nikula port at the specified address. The serial port 1064e52347bdSJani Nikula must already be setup and configured. Options are not 1065e52347bdSJani Nikula yet supported. 1066e52347bdSJani Nikula 1067e52347bdSJani Nikula msm_serial_dm,<addr> 1068e52347bdSJani Nikula Start an early, polled-mode console on an msm serial 1069e52347bdSJani Nikula dm port at the specified address. The serial port 1070e52347bdSJani Nikula must already be setup and configured. Options are not 1071e52347bdSJani Nikula yet supported. 1072e52347bdSJani Nikula 1073e36361d7SAndreas Färber owl,<addr> 1074e36361d7SAndreas Färber Start an early, polled-mode console on a serial port 1075e36361d7SAndreas Färber of an Actions Semi SoC, such as S500 or S900, at the 1076e36361d7SAndreas Färber specified address. The serial port must already be 1077e36361d7SAndreas Färber setup and configured. Options are not yet supported. 1078e36361d7SAndreas Färber 1079c10b1332SManivannan Sadhasivam rda,<addr> 1080c10b1332SManivannan Sadhasivam Start an early, polled-mode console on a serial port 1081c10b1332SManivannan Sadhasivam of an RDA Micro SoC, such as RDA8810PL, at the 1082c10b1332SManivannan Sadhasivam specified address. The serial port must already be 1083c10b1332SManivannan Sadhasivam setup and configured. Options are not yet supported. 1084c10b1332SManivannan Sadhasivam 108582f12ab3SPalmer Dabbelt sbi 108682f12ab3SPalmer Dabbelt Use RISC-V SBI (Supervisor Binary Interface) for early 108782f12ab3SPalmer Dabbelt console. 108882f12ab3SPalmer Dabbelt 1089e52347bdSJani Nikula smh Use ARM semihosting calls for early console. 1090e52347bdSJani Nikula 1091e52347bdSJani Nikula s3c2410,<addr> 1092e52347bdSJani Nikula s3c2412,<addr> 1093e52347bdSJani Nikula s3c2440,<addr> 1094e52347bdSJani Nikula s3c6400,<addr> 1095e52347bdSJani Nikula s5pv210,<addr> 1096e52347bdSJani Nikula exynos4210,<addr> 1097e52347bdSJani Nikula Use early console provided by serial driver available 1098e52347bdSJani Nikula on Samsung SoCs, requires selecting proper type and 1099e52347bdSJani Nikula a correct base address of the selected UART port. The 1100e52347bdSJani Nikula serial port must already be setup and configured. 1101e52347bdSJani Nikula Options are not yet supported. 1102e52347bdSJani Nikula 1103ec84aa0aSMartin Blumenstingl lantiq,<addr> 1104ec84aa0aSMartin Blumenstingl Start an early, polled-mode console on a lantiq serial 1105ec84aa0aSMartin Blumenstingl (lqasc) port at the specified address. The serial port 1106ec84aa0aSMartin Blumenstingl must already be setup and configured. Options are not 1107ec84aa0aSMartin Blumenstingl yet supported. 1108ec84aa0aSMartin Blumenstingl 1109e52347bdSJani Nikula lpuart,<addr> 1110e52347bdSJani Nikula lpuart32,<addr> 1111e52347bdSJani Nikula Use early console provided by Freescale LP UART driver 1112e52347bdSJani Nikula found on Freescale Vybrid and QorIQ LS1021A processors. 1113e52347bdSJani Nikula A valid base address must be provided, and the serial 1114e52347bdSJani Nikula port must already be setup and configured. 1115e52347bdSJani Nikula 11167fe068dbSJonathan Neuschäfer ec_imx21,<addr> 11177fe068dbSJonathan Neuschäfer ec_imx6q,<addr> 11187fe068dbSJonathan Neuschäfer Start an early, polled-mode, output-only console on the 11197fe068dbSJonathan Neuschäfer Freescale i.MX UART at the specified address. The UART 11207fe068dbSJonathan Neuschäfer must already be setup and configured. 11217fe068dbSJonathan Neuschäfer 1122f7c864e7SAndre Przywara ar3700_uart,<addr> 1123e52347bdSJani Nikula Start an early, polled-mode console on the 1124e52347bdSJani Nikula Armada 3700 serial port at the specified 1125e52347bdSJani Nikula address. The serial port must already be setup 1126e52347bdSJani Nikula and configured. Options are not yet supported. 1127e52347bdSJani Nikula 112843f1831bSKarthikeyan Ramasubramanian qcom_geni,<addr> 112943f1831bSKarthikeyan Ramasubramanian Start an early, polled-mode console on a Qualcomm 113043f1831bSKarthikeyan Ramasubramanian Generic Interface (GENI) based serial port at the 113143f1831bSKarthikeyan Ramasubramanian specified address. The serial port must already be 113243f1831bSKarthikeyan Ramasubramanian setup and configured. Options are not yet supported. 113343f1831bSKarthikeyan Ramasubramanian 113469c1f396SArd Biesheuvel efifb,[options] 113569c1f396SArd Biesheuvel Start an early, unaccelerated console on the EFI 113669c1f396SArd Biesheuvel memory mapped framebuffer (if available). On cache 113769c1f396SArd Biesheuvel coherent non-x86 systems that use system memory for 113869c1f396SArd Biesheuvel the framebuffer, pass the 'ram' option so that it is 113969c1f396SArd Biesheuvel mapped with the correct attributes. 114069c1f396SArd Biesheuvel 114109864c1cSStefan-gabriel Mirea linflex,<addr> 11429905f32aSStefan-Gabriel Mirea Use early console provided by Freescale LINFlexD UART 114309864c1cSStefan-gabriel Mirea serial driver for NXP S32V234 SoCs. A valid base 114409864c1cSStefan-gabriel Mirea address must be provided, and the serial port must 114509864c1cSStefan-gabriel Mirea already be setup and configured. 114609864c1cSStefan-gabriel Mirea 11474ba66a97SArnd Bergmann earlyprintk= [X86,SH,ARM,M68k,S390] 1148e52347bdSJani Nikula earlyprintk=vga 114989175cf7SHeiko Carstens earlyprintk=sclp 1150e52347bdSJani Nikula earlyprintk=xen 1151e52347bdSJani Nikula earlyprintk=serial[,ttySn[,baudrate]] 1152e52347bdSJani Nikula earlyprintk=serial[,0x...[,baudrate]] 1153e52347bdSJani Nikula earlyprintk=ttySn[,baudrate] 1154e52347bdSJani Nikula earlyprintk=dbgp[debugController#] 1155d2266bbfSFeng Tang earlyprintk=pciserial[,force],bus:device.function[,baudrate] 11561b5aeebfSLu Baolu earlyprintk=xdbc[xhciController#] 1157e52347bdSJani Nikula 1158e52347bdSJani Nikula earlyprintk is useful when the kernel crashes before 1159e52347bdSJani Nikula the normal console is initialized. It is not enabled by 1160e52347bdSJani Nikula default because it has some cosmetic problems. 1161e52347bdSJani Nikula 1162e52347bdSJani Nikula Append ",keep" to not disable it when the real console 1163e52347bdSJani Nikula takes over. 1164e52347bdSJani Nikula 1165e52347bdSJani Nikula Only one of vga, efi, serial, or usb debug port can 1166e52347bdSJani Nikula be used at a time. 1167e52347bdSJani Nikula 1168e52347bdSJani Nikula Currently only ttyS0 and ttyS1 may be specified by 1169e52347bdSJani Nikula name. Other I/O ports may be explicitly specified 1170e52347bdSJani Nikula on some architectures (x86 and arm at least) by 1171e52347bdSJani Nikula replacing ttySn with an I/O port address, like this: 1172e52347bdSJani Nikula earlyprintk=serial,0x1008,115200 1173e52347bdSJani Nikula You can find the port for a given device in 1174e52347bdSJani Nikula /proc/tty/driver/serial: 1175e52347bdSJani Nikula 2: uart:ST16650V2 port:00001008 irq:18 ... 1176e52347bdSJani Nikula 1177e52347bdSJani Nikula Interaction with the standard serial driver is not 1178e52347bdSJani Nikula very good. 1179e52347bdSJani Nikula 1180e52347bdSJani Nikula The VGA and EFI output is eventually overwritten by 1181e52347bdSJani Nikula the real console. 1182e52347bdSJani Nikula 1183e52347bdSJani Nikula The xen output can only be used by Xen PV guests. 1184e52347bdSJani Nikula 118589175cf7SHeiko Carstens The sclp output can only be used on s390. 118689175cf7SHeiko Carstens 1187d2266bbfSFeng Tang The optional "force" to "pciserial" enables use of a 1188d2266bbfSFeng Tang PCI device even when its classcode is not of the 1189d2266bbfSFeng Tang UART class. 1190d2266bbfSFeng Tang 1191e52347bdSJani Nikula edac_report= [HW,EDAC] Control how to report EDAC event 1192e52347bdSJani Nikula Format: {"on" | "off" | "force"} 1193e52347bdSJani Nikula on: enable EDAC to report H/W event. May be overridden 1194e52347bdSJani Nikula by other higher priority error reporting module. 1195e52347bdSJani Nikula off: disable H/W event reporting through EDAC. 1196e52347bdSJani Nikula force: enforce the use of EDAC to report H/W event. 1197e52347bdSJani Nikula default: on. 1198e52347bdSJani Nikula 1199e52347bdSJani Nikula ekgdboc= [X86,KGDB] Allow early kernel console debugging 1200e52347bdSJani Nikula ekgdboc=kbd 1201e52347bdSJani Nikula 1202e52347bdSJani Nikula This is designed to be used in conjunction with 1203e52347bdSJani Nikula the boot argument: earlyprintk=vga 1204e52347bdSJani Nikula 1205f71fc3bcSDouglas Anderson This parameter works in place of the kgdboc parameter 1206f71fc3bcSDouglas Anderson but can only be used if the backing tty is available 1207f71fc3bcSDouglas Anderson very early in the boot process. For early debugging 1208f71fc3bcSDouglas Anderson via a serial port see kgdboc_earlycon instead. 1209f71fc3bcSDouglas Anderson 1210e52347bdSJani Nikula edd= [EDD] 1211e52347bdSJani Nikula Format: {"off" | "on" | "skip[mbr]"} 1212e52347bdSJani Nikula 1213e52347bdSJani Nikula efi= [EFI] 1214b617c526SDan Williams Format: { "old_map", "nochunk", "noruntime", "debug", 12154444f854SMatthew Garrett "nosoftreserve", "disable_early_pci_dma", 12164444f854SMatthew Garrett "no_disable_early_pci_dma" } 1217e52347bdSJani Nikula old_map [X86-64]: switch to the old ioremap-based EFI 12181f299fadSArd Biesheuvel runtime services mapping. [Needs CONFIG_X86_UV=y] 1219e52347bdSJani Nikula nochunk: disable reading files in "chunks" in the EFI 1220e52347bdSJani Nikula boot stub, as chunking can cause problems with some 1221e52347bdSJani Nikula firmware implementations. 1222e52347bdSJani Nikula noruntime : disable EFI runtime services support 1223e52347bdSJani Nikula debug: enable misc debug output 1224b617c526SDan Williams nosoftreserve: The EFI_MEMORY_SP (Specific Purpose) 1225b617c526SDan Williams attribute may cause the kernel to reserve the 1226b617c526SDan Williams memory range for a memory mapping driver to 1227b617c526SDan Williams claim. Specify efi=nosoftreserve to disable this 1228b617c526SDan Williams reservation and treat the memory by its base type 1229b617c526SDan Williams (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM"). 12304444f854SMatthew Garrett disable_early_pci_dma: Disable the busmaster bit on all 12314444f854SMatthew Garrett PCI bridges while in the EFI boot stub 12324444f854SMatthew Garrett no_disable_early_pci_dma: Leave the busmaster bit set 12334444f854SMatthew Garrett on all PCI bridges while in the EFI boot stub 1234e52347bdSJani Nikula 1235e52347bdSJani Nikula efi_no_storage_paranoia [EFI; X86] 1236e52347bdSJani Nikula Using this parameter you can use more than 50% of 1237e52347bdSJani Nikula your efi variable storage. Use this parameter only if 1238e52347bdSJani Nikula you are really sure that your UEFI does sane gc and 1239e52347bdSJani Nikula fulfills the spec otherwise your board may brick. 1240e52347bdSJani Nikula 1241e52347bdSJani Nikula efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] 1242e52347bdSJani Nikula Add arbitrary attribute to specific memory range by 1243e52347bdSJani Nikula updating original EFI memory map. 1244e52347bdSJani Nikula Region of memory which aa attribute is added to is 1245e52347bdSJani Nikula from ss to ss+nn. 1246199c8471SDan Williams 1247e52347bdSJani Nikula If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 1248e52347bdSJani Nikula is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) 1249e52347bdSJani Nikula attribute is added to range 0x100000000-0x180000000 and 1250e52347bdSJani Nikula 0x10a0000000-0x1120000000. 1251e52347bdSJani Nikula 1252199c8471SDan Williams If efi_fake_mem=8G@9G:0x40000 is specified, the 1253199c8471SDan Williams EFI_MEMORY_SP(0x40000) attribute is added to 1254199c8471SDan Williams range 0x240000000-0x43fffffff. 1255199c8471SDan Williams 1256e52347bdSJani Nikula Using this parameter you can do debugging of EFI memmap 1257199c8471SDan Williams related features. For example, you can do debugging of 1258e52347bdSJani Nikula Address Range Mirroring feature even if your box 1259199c8471SDan Williams doesn't support it, or mark specific memory as 1260199c8471SDan Williams "soft reserved". 1261e52347bdSJani Nikula 1262e52347bdSJani Nikula efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT 1263e52347bdSJani Nikula that is to be dynamically loaded by Linux. If there are 1264e52347bdSJani Nikula multiple variables with the same name but with different 1265e52347bdSJani Nikula vendor GUIDs, all of them will be loaded. See 1266cb1aaebeSMauro Carvalho Chehab Documentation/admin-guide/acpi/ssdt-overlays.rst for details. 1267e52347bdSJani Nikula 1268e52347bdSJani Nikula 1269e52347bdSJani Nikula eisa_irq_edge= [PARISC,HW] 1270e52347bdSJani Nikula See header of drivers/parisc/eisa.c. 1271e52347bdSJani Nikula 1272e52347bdSJani Nikula elanfreq= [X86-32] 1273e52347bdSJani Nikula See comment before function elanfreq_setup() in 1274e52347bdSJani Nikula arch/x86/kernel/cpu/cpufreq/elanfreq.c. 1275e52347bdSJani Nikula 1276e52347bdSJani Nikula elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] 1277e52347bdSJani Nikula Specifies physical address of start of kernel core 1278e52347bdSJani Nikula image elf header and optionally the size. Generally 1279e52347bdSJani Nikula kexec loader will pass this option to capture kernel. 1280330d4810SMauro Carvalho Chehab See Documentation/admin-guide/kdump/kdump.rst for details. 1281e52347bdSJani Nikula 1282e52347bdSJani Nikula enable_mtrr_cleanup [X86] 1283e52347bdSJani Nikula The kernel tries to adjust MTRR layout from continuous 1284e52347bdSJani Nikula to discrete, to make X server driver able to add WB 1285e52347bdSJani Nikula entry later. This parameter enables that. 1286e52347bdSJani Nikula 1287e52347bdSJani Nikula enable_timer_pin_1 [X86] 1288e52347bdSJani Nikula Enable PIN 1 of APIC timer 1289e52347bdSJani Nikula Can be useful to work around chipset bugs 1290e52347bdSJani Nikula (in particular on some ATI chipsets). 1291e52347bdSJani Nikula The kernel tries to set a reasonable default. 1292e52347bdSJani Nikula 1293e52347bdSJani Nikula enforcing [SELINUX] Set initial enforcing status. 1294e52347bdSJani Nikula Format: {"0" | "1"} 1295e52347bdSJani Nikula See security/selinux/Kconfig help text. 1296e52347bdSJani Nikula 0 -- permissive (log only, no denials). 1297e52347bdSJani Nikula 1 -- enforcing (deny and log). 1298e52347bdSJani Nikula Default value is 0. 1299d41415ebSStephen Smalley Value can be changed at runtime via 1300d41415ebSStephen Smalley /sys/fs/selinux/enforce. 1301e52347bdSJani Nikula 1302e52347bdSJani Nikula erst_disable [ACPI] 1303e52347bdSJani Nikula Disable Error Record Serialization Table (ERST) 1304e52347bdSJani Nikula support. 1305e52347bdSJani Nikula 1306e52347bdSJani Nikula ether= [HW,NET] Ethernet cards parameters 1307e52347bdSJani Nikula This option is obsoleted by the "netdev=" option, which 1308e52347bdSJani Nikula has equivalent usage. See its documentation for details. 1309e52347bdSJani Nikula 1310e52347bdSJani Nikula evm= [EVM] 1311e52347bdSJani Nikula Format: { "fix" } 1312e52347bdSJani Nikula Permit 'security.evm' to be updated regardless of 1313e52347bdSJani Nikula current integrity status. 1314e52347bdSJani Nikula 1315e52347bdSJani Nikula failslab= 1316e52347bdSJani Nikula fail_page_alloc= 1317e52347bdSJani Nikula fail_make_request=[KNL] 1318e52347bdSJani Nikula General fault injection mechanism. 1319e52347bdSJani Nikula Format: <interval>,<probability>,<space>,<times> 1320e52347bdSJani Nikula See also Documentation/fault-injection/. 1321e52347bdSJani Nikula 1322e52347bdSJani Nikula floppy= [HW] 1323e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/floppy.rst. 1324e52347bdSJani Nikula 1325e52347bdSJani Nikula force_pal_cache_flush 1326e52347bdSJani Nikula [IA-64] Avoid check_sal_cache_flush which may hang on 1327e52347bdSJani Nikula buggy SAL_CACHE_FLUSH implementations. Using this 1328e52347bdSJani Nikula parameter will force ia64_sal_cache_flush to call 1329e52347bdSJani Nikula ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 1330e52347bdSJani Nikula 1331e52347bdSJani Nikula forcepae [X86-32] 1332e52347bdSJani Nikula Forcefully enable Physical Address Extension (PAE). 1333e52347bdSJani Nikula Many Pentium M systems disable PAE but may have a 1334e52347bdSJani Nikula functionally usable PAE implementation. 1335e52347bdSJani Nikula Warning: use of this parameter will taint the kernel 1336e52347bdSJani Nikula and may cause unknown problems. 1337e52347bdSJani Nikula 1338e52347bdSJani Nikula ftrace=[tracer] 1339e52347bdSJani Nikula [FTRACE] will set and start the specified tracer 1340e52347bdSJani Nikula as early as possible in order to facilitate early 1341e52347bdSJani Nikula boot debugging. 1342e52347bdSJani Nikula 1343e52347bdSJani Nikula ftrace_dump_on_oops[=orig_cpu] 1344e52347bdSJani Nikula [FTRACE] will dump the trace buffers on oops. 1345e52347bdSJani Nikula If no parameter is passed, ftrace will dump 1346e52347bdSJani Nikula buffers of all CPUs, but if you pass orig_cpu, it will 1347e52347bdSJani Nikula dump only the buffer of the CPU that triggered the 1348e52347bdSJani Nikula oops. 1349e52347bdSJani Nikula 1350e52347bdSJani Nikula ftrace_filter=[function-list] 1351e52347bdSJani Nikula [FTRACE] Limit the functions traced by the function 1352e52347bdSJani Nikula tracer at boot up. function-list is a comma separated 1353e52347bdSJani Nikula list of functions. This list can be changed at run 1354e52347bdSJani Nikula time by the set_ftrace_filter file in the debugfs 1355e52347bdSJani Nikula tracing directory. 1356e52347bdSJani Nikula 1357e52347bdSJani Nikula ftrace_notrace=[function-list] 1358e52347bdSJani Nikula [FTRACE] Do not trace the functions specified in 1359e52347bdSJani Nikula function-list. This list can be changed at run time 1360e52347bdSJani Nikula by the set_ftrace_notrace file in the debugfs 1361e52347bdSJani Nikula tracing directory. 1362e52347bdSJani Nikula 1363e52347bdSJani Nikula ftrace_graph_filter=[function-list] 1364e52347bdSJani Nikula [FTRACE] Limit the top level callers functions traced 1365e52347bdSJani Nikula by the function graph tracer at boot up. 1366e52347bdSJani Nikula function-list is a comma separated list of functions 1367e52347bdSJani Nikula that can be changed at run time by the 1368e52347bdSJani Nikula set_graph_function file in the debugfs tracing directory. 1369e52347bdSJani Nikula 1370e52347bdSJani Nikula ftrace_graph_notrace=[function-list] 1371e52347bdSJani Nikula [FTRACE] Do not trace from the functions specified in 1372e52347bdSJani Nikula function-list. This list is a comma separated list of 1373e52347bdSJani Nikula functions that can be changed at run time by the 1374e52347bdSJani Nikula set_graph_notrace file in the debugfs tracing directory. 1375e52347bdSJani Nikula 137665a50c65STodd Brandt ftrace_graph_max_depth=<uint> 137765a50c65STodd Brandt [FTRACE] Used with the function graph tracer. This is 137865a50c65STodd Brandt the max depth it will trace into a function. This value 137965a50c65STodd Brandt can be changed at run time by the max_graph_depth file 138065a50c65STodd Brandt in the tracefs tracing directory. default: 0 (no limit) 138165a50c65STodd Brandt 13828375e74fSSaravana Kannan fw_devlink= [KNL] Create device links between consumer and supplier 13838375e74fSSaravana Kannan devices by scanning the firmware to infer the 13848375e74fSSaravana Kannan consumer/supplier relationships. This feature is 13858375e74fSSaravana Kannan especially useful when drivers are loaded as modules as 13868375e74fSSaravana Kannan it ensures proper ordering of tasks like device probing 13878375e74fSSaravana Kannan (suppliers first, then consumers), supplier boot state 13888375e74fSSaravana Kannan clean up (only after all consumers have probed), 13898375e74fSSaravana Kannan suspend/resume & runtime PM (consumers first, then 13908375e74fSSaravana Kannan suppliers). 13918375e74fSSaravana Kannan Format: { off | permissive | on | rpm } 13928375e74fSSaravana Kannan off -- Don't create device links from firmware info. 13938375e74fSSaravana Kannan permissive -- Create device links from firmware info 13948375e74fSSaravana Kannan but use it only for ordering boot state clean 13958375e74fSSaravana Kannan up (sync_state() calls). 13968375e74fSSaravana Kannan on -- Create device links from firmware info and use it 13978375e74fSSaravana Kannan to enforce probe and suspend/resume ordering. 13988375e74fSSaravana Kannan rpm -- Like "on", but also use to order runtime PM. 13998375e74fSSaravana Kannan 1400e52347bdSJani Nikula gamecon.map[2|3]= 1401e52347bdSJani Nikula [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 1402e52347bdSJani Nikula support via parallel port (up to 5 devices per port) 1403e52347bdSJani Nikula Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 14041752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 1405e52347bdSJani Nikula 1406e52347bdSJani Nikula gamma= [HW,DRM] 1407e52347bdSJani Nikula 1408e52347bdSJani Nikula gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 1409e52347bdSJani Nikula Format: off | on 1410e52347bdSJani Nikula default: on 1411e52347bdSJani Nikula 1412e52347bdSJani Nikula gcov_persist= [GCOV] When non-zero (default), profiling data for 1413e52347bdSJani Nikula kernel modules is saved and remains accessible via 1414e52347bdSJani Nikula debugfs, even when the module is unloaded/reloaded. 1415e52347bdSJani Nikula When zero, profiling data is discarded and associated 1416e52347bdSJani Nikula debugfs files are removed at module unload time. 1417e52347bdSJani Nikula 141847512cfdSThomas Gleixner goldfish [X86] Enable the goldfish android emulator platform. 141947512cfdSThomas Gleixner Don't use this when you are not running on the 142047512cfdSThomas Gleixner android emulator 142147512cfdSThomas Gleixner 1422e52347bdSJani Nikula gpt [EFI] Forces disk with valid GPT signature but 1423e52347bdSJani Nikula invalid Protective MBR to be treated as GPT. If the 1424e52347bdSJani Nikula primary GPT is corrupted, it enables the backup/alternate 1425e52347bdSJani Nikula GPT to be used instead. 1426e52347bdSJani Nikula 1427e52347bdSJani Nikula grcan.enable0= [HW] Configuration of physical interface 0. Determines 1428e52347bdSJani Nikula the "Enable 0" bit of the configuration register. 1429e52347bdSJani Nikula Format: 0 | 1 1430e52347bdSJani Nikula Default: 0 1431e52347bdSJani Nikula grcan.enable1= [HW] Configuration of physical interface 1. Determines 1432e52347bdSJani Nikula the "Enable 0" bit of the configuration register. 1433e52347bdSJani Nikula Format: 0 | 1 1434e52347bdSJani Nikula Default: 0 1435e52347bdSJani Nikula grcan.select= [HW] Select which physical interface to use. 1436e52347bdSJani Nikula Format: 0 | 1 1437e52347bdSJani Nikula Default: 0 1438e52347bdSJani Nikula grcan.txsize= [HW] Sets the size of the tx buffer. 1439e52347bdSJani Nikula Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0. 1440e52347bdSJani Nikula Default: 1024 1441e52347bdSJani Nikula grcan.rxsize= [HW] Sets the size of the rx buffer. 1442e52347bdSJani Nikula Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. 1443e52347bdSJani Nikula Default: 1024 1444e52347bdSJani Nikula 1445e52347bdSJani Nikula gpio-mockup.gpio_mockup_ranges 1446e52347bdSJani Nikula [HW] Sets the ranges of gpiochip of for this device. 1447e52347bdSJani Nikula Format: <start1>,<end1>,<start2>,<end2>... 1448e52347bdSJani Nikula 1449e52347bdSJani Nikula hardlockup_all_cpu_backtrace= 1450e52347bdSJani Nikula [KNL] Should the hard-lockup detector generate 1451e52347bdSJani Nikula backtraces on all cpus. 1452f117955aSGuilherme G. Piccoli Format: 0 | 1 1453e52347bdSJani Nikula 1454e52347bdSJani Nikula hashdist= [KNL,NUMA] Large hashes allocated during boot 1455e52347bdSJani Nikula are distributed across NUMA nodes. Defaults on 1456e52347bdSJani Nikula for 64-bit NUMA, off otherwise. 1457e52347bdSJani Nikula Format: 0 | 1 (for off | on) 1458e52347bdSJani Nikula 1459e52347bdSJani Nikula hcl= [IA-64] SGI's Hardware Graph compatibility layer 1460e52347bdSJani Nikula 1461e52347bdSJani Nikula hd= [EIDE] (E)IDE hard drive subsystem geometry 1462e52347bdSJani Nikula Format: <cyl>,<head>,<sect> 1463e52347bdSJani Nikula 1464e52347bdSJani Nikula hest_disable [ACPI] 1465e52347bdSJani Nikula Disable Hardware Error Source Table (HEST) support; 1466e52347bdSJani Nikula corresponding firmware-first mode error processing 1467e52347bdSJani Nikula logic will be disabled. 1468e52347bdSJani Nikula 1469e52347bdSJani Nikula highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 1470e52347bdSJani Nikula size of <nn>. This works even on boxes that have no 1471e52347bdSJani Nikula highmem otherwise. This also works to reduce highmem 1472e52347bdSJani Nikula size on bigger boxes. 1473e52347bdSJani Nikula 1474e52347bdSJani Nikula highres= [KNL] Enable/disable high resolution timer mode. 1475e52347bdSJani Nikula Valid parameters: "on", "off" 1476e52347bdSJani Nikula Default: "on" 1477e52347bdSJani Nikula 1478e52347bdSJani Nikula hlt [BUGS=ARM,SH] 1479e52347bdSJani Nikula 1480e52347bdSJani Nikula hpet= [X86-32,HPET] option to control HPET usage 1481e52347bdSJani Nikula Format: { enable (default) | disable | force | 1482e52347bdSJani Nikula verbose } 1483e52347bdSJani Nikula disable: disable HPET and use PIT instead 1484e52347bdSJani Nikula force: allow force enabled of undocumented chips (ICH4, 1485e52347bdSJani Nikula VIA, nVidia) 1486e52347bdSJani Nikula verbose: show contents of HPET registers during setup 1487e52347bdSJani Nikula 1488e52347bdSJani Nikula hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET 1489e52347bdSJani Nikula registers. Default set by CONFIG_HPET_MMAP_DEFAULT. 1490e52347bdSJani Nikula 1491cf11e85fSRoman Gushchin hugetlb_cma= [HW] The size of a cma area used for allocation 1492cf11e85fSRoman Gushchin of gigantic hugepages. 1493cf11e85fSRoman Gushchin Format: nn[KMGTPE] 1494cf11e85fSRoman Gushchin 1495cf11e85fSRoman Gushchin Reserve a cma area of given size and allocate gigantic 1496cf11e85fSRoman Gushchin hugepages using the cma allocator. If enabled, the 1497cf11e85fSRoman Gushchin boot-time allocation of gigantic hugepages is skipped. 1498cf11e85fSRoman Gushchin 1499282f4214SMike Kravetz hugepages= [HW] Number of HugeTLB pages to allocate at boot. 1500282f4214SMike Kravetz If this follows hugepagesz (below), it specifies 1501282f4214SMike Kravetz the number of pages of hugepagesz to be allocated. 1502282f4214SMike Kravetz If this is the first HugeTLB parameter on the command 1503282f4214SMike Kravetz line, it specifies the number of pages to allocate for 1504282f4214SMike Kravetz the default huge page size. See also 1505282f4214SMike Kravetz Documentation/admin-guide/mm/hugetlbpage.rst. 1506282f4214SMike Kravetz Format: <integer> 1507282f4214SMike Kravetz 1508282f4214SMike Kravetz hugepagesz= 1509282f4214SMike Kravetz [HW] The size of the HugeTLB pages. This is used in 1510282f4214SMike Kravetz conjunction with hugepages (above) to allocate huge 1511282f4214SMike Kravetz pages of a specific size at boot. The pair 1512282f4214SMike Kravetz hugepagesz=X hugepages=Y can be specified once for 1513282f4214SMike Kravetz each supported huge page size. Huge page sizes are 1514282f4214SMike Kravetz architecture dependent. See also 1515282f4214SMike Kravetz Documentation/admin-guide/mm/hugetlbpage.rst. 1516282f4214SMike Kravetz Format: size[KMG] 1517e52347bdSJani Nikula 1518a49d9c0aSOmar Sandoval hung_task_panic= 1519a49d9c0aSOmar Sandoval [KNL] Should the hung task detector generate panics. 1520f117955aSGuilherme G. Piccoli Format: 0 | 1 1521a49d9c0aSOmar Sandoval 1522b467f3efSVlastimil Babka A value of 1 instructs the kernel to panic when a 1523a49d9c0aSOmar Sandoval hung task is detected. The default value is controlled 1524a49d9c0aSOmar Sandoval by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time 1525a49d9c0aSOmar Sandoval option. The value selected by this boot parameter can 1526a49d9c0aSOmar Sandoval be changed later by the kernel.hung_task_panic sysctl. 1527a49d9c0aSOmar Sandoval 1528e52347bdSJani Nikula hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) 1529e52347bdSJani Nikula terminal devices. Valid values: 0..8 1530e52347bdSJani Nikula hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. 1531e52347bdSJani Nikula If specified, z/VM IUCV HVC accepts connections 1532e52347bdSJani Nikula from listed z/VM user IDs only. 15333a025de6SYi Sun 15343a025de6SYi Sun hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations 15353a025de6SYi Sun which allow the hypervisor to 'idle' the 15363a025de6SYi Sun guest on lock contention. 15373a025de6SYi Sun 1538e52347bdSJani Nikula keep_bootcon [KNL] 1539e52347bdSJani Nikula Do not unregister boot console at start. This is only 1540e52347bdSJani Nikula useful for debugging when something happens in the window 1541e52347bdSJani Nikula between unregistering the boot console and initializing 1542e52347bdSJani Nikula the real console. 1543e52347bdSJani Nikula 1544e52347bdSJani Nikula i2c_bus= [HW] Override the default board specific I2C bus speed 1545e52347bdSJani Nikula or register an additional I2C bus that is not 1546e52347bdSJani Nikula registered from board initialization code. 1547e52347bdSJani Nikula Format: 1548e52347bdSJani Nikula <bus_id>,<clkrate> 1549e52347bdSJani Nikula 1550e52347bdSJani Nikula i8042.debug [HW] Toggle i8042 debug mode 1551e52347bdSJani Nikula i8042.unmask_kbd_data 1552e52347bdSJani Nikula [HW] Enable printing of interrupt data from the KBD port 1553e52347bdSJani Nikula (disabled by default, and as a pre-condition 1554e52347bdSJani Nikula requires that i8042.debug=1 be enabled) 1555e52347bdSJani Nikula i8042.direct [HW] Put keyboard port into non-translated mode 1556e52347bdSJani Nikula i8042.dumbkbd [HW] Pretend that controller can only read data from 1557e52347bdSJani Nikula keyboard and cannot control its state 1558e52347bdSJani Nikula (Don't attempt to blink the leds) 1559e52347bdSJani Nikula i8042.noaux [HW] Don't check for auxiliary (== mouse) port 1560e52347bdSJani Nikula i8042.nokbd [HW] Don't check/create keyboard port 1561e52347bdSJani Nikula i8042.noloop [HW] Disable the AUX Loopback command while probing 1562e52347bdSJani Nikula for the AUX port 1563e52347bdSJani Nikula i8042.nomux [HW] Don't check presence of an active multiplexing 1564e52347bdSJani Nikula controller 1565e52347bdSJani Nikula i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 1566e52347bdSJani Nikula controllers 1567e52347bdSJani Nikula i8042.notimeout [HW] Ignore timeout condition signalled by controller 1568e52347bdSJani Nikula i8042.reset [HW] Reset the controller during init, cleanup and 1569e52347bdSJani Nikula suspend-to-ram transitions, only during s2r 1570e52347bdSJani Nikula transitions, or never reset 1571e52347bdSJani Nikula Format: { 1 | Y | y | 0 | N | n } 1572e52347bdSJani Nikula 1, Y, y: always reset controller 1573e52347bdSJani Nikula 0, N, n: don't ever reset controller 1574e52347bdSJani Nikula Default: only on s2r transitions on x86; most other 1575e52347bdSJani Nikula architectures force reset to be always executed 1576e52347bdSJani Nikula i8042.unlock [HW] Unlock (ignore) the keylock 1577e52347bdSJani Nikula i8042.kbdreset [HW] Reset device connected to KBD port 1578e52347bdSJani Nikula 1579e52347bdSJani Nikula i810= [HW,DRM] 1580e52347bdSJani Nikula 1581e52347bdSJani Nikula i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 1582e52347bdSJani Nikula indicates that the driver is running on unsupported 1583e52347bdSJani Nikula hardware. 1584e52347bdSJani Nikula i8k.force [HW] Activate i8k driver even if SMM BIOS signature 1585e52347bdSJani Nikula does not match list of supported models. 1586e52347bdSJani Nikula i8k.power_status 1587e52347bdSJani Nikula [HW] Report power status in /proc/i8k 1588e52347bdSJani Nikula (disabled by default) 1589e52347bdSJani Nikula i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 1590e52347bdSJani Nikula capability is set. 1591e52347bdSJani Nikula 1592e52347bdSJani Nikula i915.invert_brightness= 1593e52347bdSJani Nikula [DRM] Invert the sense of the variable that is used to 1594e52347bdSJani Nikula set the brightness of the panel backlight. Normally a 1595e52347bdSJani Nikula brightness value of 0 indicates backlight switched off, 1596e52347bdSJani Nikula and the maximum of the brightness value sets the backlight 1597e52347bdSJani Nikula to maximum brightness. If this parameter is set to 0 1598e52347bdSJani Nikula (default) and the machine requires it, or this parameter 1599e52347bdSJani Nikula is set to 1, a brightness value of 0 sets the backlight 1600e52347bdSJani Nikula to maximum brightness, and the maximum of the brightness 1601e52347bdSJani Nikula value switches the backlight off. 1602e52347bdSJani Nikula -1 -- never invert brightness 1603e52347bdSJani Nikula 0 -- machine default 1604e52347bdSJani Nikula 1 -- force brightness inversion 1605e52347bdSJani Nikula 1606e52347bdSJani Nikula icn= [HW,ISDN] 1607e52347bdSJani Nikula Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 1608e52347bdSJani Nikula 1609e52347bdSJani Nikula ide-core.nodma= [HW] (E)IDE subsystem 1610e52347bdSJani Nikula Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc 1611e52347bdSJani Nikula .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr 1612e52347bdSJani Nikula .cdrom .chs .ignore_cable are additional options 1613d7b461c5SMauro Carvalho Chehab See Documentation/ide/ide.rst. 1614e52347bdSJani Nikula 1615e52347bdSJani Nikula ide-generic.probe-mask= [HW] (E)IDE subsystem 1616e52347bdSJani Nikula Format: <int> 1617e52347bdSJani Nikula Probe mask for legacy ISA IDE ports. Depending on 1618e52347bdSJani Nikula platform up to 6 ports are supported, enabled by 1619e52347bdSJani Nikula setting corresponding bits in the mask to 1. The 1620e52347bdSJani Nikula default value is 0x0, which has a special meaning. 1621e52347bdSJani Nikula On systems that have PCI, it triggers scanning the 1622e52347bdSJani Nikula PCI bus for the first and the second port, which 1623e52347bdSJani Nikula are then probed. On systems without PCI the value 1624e52347bdSJani Nikula of 0x0 enables probing the two first ports as if it 1625e52347bdSJani Nikula was 0x3. 1626e52347bdSJani Nikula 1627e52347bdSJani Nikula ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 1628e52347bdSJani Nikula Claim all unknown PCI IDE storage controllers. 1629e52347bdSJani Nikula 1630e52347bdSJani Nikula idle= [X86] 1631e52347bdSJani Nikula Format: idle=poll, idle=halt, idle=nomwait 1632e52347bdSJani Nikula Poll forces a polling idle loop that can slightly 1633e52347bdSJani Nikula improve the performance of waking up a idle CPU, but 1634e52347bdSJani Nikula will use a lot of power and make the system run hot. 1635e52347bdSJani Nikula Not recommended. 1636e52347bdSJani Nikula idle=halt: Halt is forced to be used for CPU idle. 1637e52347bdSJani Nikula In such case C2/C3 won't be used again. 1638e52347bdSJani Nikula idle=nomwait: Disable mwait for CPU C-states 1639e52347bdSJani Nikula 1640e52347bdSJani Nikula ieee754= [MIPS] Select IEEE Std 754 conformance mode 1641e52347bdSJani Nikula Format: { strict | legacy | 2008 | relaxed } 1642e52347bdSJani Nikula Default: strict 1643e52347bdSJani Nikula 1644e52347bdSJani Nikula Choose which programs will be accepted for execution 1645e52347bdSJani Nikula based on the IEEE 754 NaN encoding(s) supported by 1646e52347bdSJani Nikula the FPU and the NaN encoding requested with the value 1647e52347bdSJani Nikula of an ELF file header flag individually set by each 1648e52347bdSJani Nikula binary. Hardware implementations are permitted to 1649e52347bdSJani Nikula support either or both of the legacy and the 2008 NaN 1650e52347bdSJani Nikula encoding mode. 1651e52347bdSJani Nikula 1652e52347bdSJani Nikula Available settings are as follows: 1653e52347bdSJani Nikula strict accept binaries that request a NaN encoding 1654e52347bdSJani Nikula supported by the FPU 1655e52347bdSJani Nikula legacy only accept legacy-NaN binaries, if supported 1656e52347bdSJani Nikula by the FPU 1657e52347bdSJani Nikula 2008 only accept 2008-NaN binaries, if supported 1658e52347bdSJani Nikula by the FPU 1659e52347bdSJani Nikula relaxed accept any binaries regardless of whether 1660e52347bdSJani Nikula supported by the FPU 1661e52347bdSJani Nikula 1662e52347bdSJani Nikula The FPU emulator is always able to support both NaN 1663e52347bdSJani Nikula encodings, so if no FPU hardware is present or it has 1664e52347bdSJani Nikula been disabled with 'nofpu', then the settings of 1665e52347bdSJani Nikula 'legacy' and '2008' strap the emulator accordingly, 1666e52347bdSJani Nikula 'relaxed' straps the emulator for both legacy-NaN and 1667e52347bdSJani Nikula 2008-NaN, whereas 'strict' enables legacy-NaN only on 1668e52347bdSJani Nikula legacy processors and both NaN encodings on MIPS32 or 1669e52347bdSJani Nikula MIPS64 CPUs. 1670e52347bdSJani Nikula 1671e52347bdSJani Nikula The setting for ABS.fmt/NEG.fmt instruction execution 1672e52347bdSJani Nikula mode generally follows that for the NaN encoding, 1673e52347bdSJani Nikula except where unsupported by hardware. 1674e52347bdSJani Nikula 1675e52347bdSJani Nikula ignore_loglevel [KNL] 1676e52347bdSJani Nikula Ignore loglevel setting - this will print /all/ 1677e52347bdSJani Nikula kernel messages to the console. Useful for debugging. 1678e52347bdSJani Nikula We also add it as printk module parameter, so users 1679e52347bdSJani Nikula could change it dynamically, usually by 1680e52347bdSJani Nikula /sys/module/printk/parameters/ignore_loglevel. 1681e52347bdSJani Nikula 1682e52347bdSJani Nikula ignore_rlimit_data 1683e52347bdSJani Nikula Ignore RLIMIT_DATA setting for data mappings, 1684e52347bdSJani Nikula print warning at first misuse. Can be changed via 1685e52347bdSJani Nikula /sys/module/kernel/parameters/ignore_rlimit_data. 1686e52347bdSJani Nikula 1687e52347bdSJani Nikula ihash_entries= [KNL] 1688e52347bdSJani Nikula Set number of hash buckets for inode cache. 1689e52347bdSJani Nikula 1690e52347bdSJani Nikula ima_appraise= [IMA] appraise integrity measurements 1691e52347bdSJani Nikula Format: { "off" | "enforce" | "fix" | "log" } 1692e52347bdSJani Nikula default: "enforce" 1693e52347bdSJani Nikula 169441475a3eSPetr Vorel ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead. 1695e52347bdSJani Nikula The builtin appraise policy appraises all files 1696e52347bdSJani Nikula owned by uid=0. 1697e52347bdSJani Nikula 1698d68a6fe9SMimi Zohar ima_canonical_fmt [IMA] 1699d68a6fe9SMimi Zohar Use the canonical format for the binary runtime 1700d68a6fe9SMimi Zohar measurements, instead of host native format. 1701d68a6fe9SMimi Zohar 1702e52347bdSJani Nikula ima_hash= [IMA] 1703e52347bdSJani Nikula Format: { md5 | sha1 | rmd160 | sha256 | sha384 1704e52347bdSJani Nikula | sha512 | ... } 1705e52347bdSJani Nikula default: "sha1" 1706e52347bdSJani Nikula 1707e52347bdSJani Nikula The list of supported hash algorithms is defined 1708e52347bdSJani Nikula in crypto/hash_info.h. 1709e52347bdSJani Nikula 1710e52347bdSJani Nikula ima_policy= [IMA] 171133ce9549SMimi Zohar The builtin policies to load during IMA setup. 17129e67028eSMimi Zohar Format: "tcb | appraise_tcb | secure_boot | 17139e67028eSMimi Zohar fail_securely" 171433ce9549SMimi Zohar 171533ce9549SMimi Zohar The "tcb" policy measures all programs exec'd, files 171633ce9549SMimi Zohar mmap'd for exec, and all files opened with the read 171733ce9549SMimi Zohar mode bit set by either the effective uid (euid=0) or 171833ce9549SMimi Zohar uid=0. 171933ce9549SMimi Zohar 172033ce9549SMimi Zohar The "appraise_tcb" policy appraises the integrity of 172141475a3eSPetr Vorel all files owned by root. 1722e52347bdSJani Nikula 1723503ceaefSMimi Zohar The "secure_boot" policy appraises the integrity 1724503ceaefSMimi Zohar of files (eg. kexec kernel image, kernel modules, 1725503ceaefSMimi Zohar firmware, policy, etc) based on file signatures. 1726e52347bdSJani Nikula 17279e67028eSMimi Zohar The "fail_securely" policy forces file signature 17289e67028eSMimi Zohar verification failure also on privileged mounted 17299e67028eSMimi Zohar filesystems with the SB_I_UNVERIFIABLE_SIGNATURE 17309e67028eSMimi Zohar flag. 17319e67028eSMimi Zohar 1732e52347bdSJani Nikula ima_tcb [IMA] Deprecated. Use ima_policy= instead. 1733e52347bdSJani Nikula Load a policy which meets the needs of the Trusted 1734e52347bdSJani Nikula Computing Base. This means IMA will measure all 1735e52347bdSJani Nikula programs exec'd, files mmap'd for exec, and all files 1736e52347bdSJani Nikula opened for read by uid=0. 1737e52347bdSJani Nikula 1738e52347bdSJani Nikula ima_template= [IMA] 1739e52347bdSJani Nikula Select one of defined IMA measurements template formats. 1740e52347bdSJani Nikula Formats: { "ima" | "ima-ng" | "ima-sig" } 1741e52347bdSJani Nikula Default: "ima-ng" 1742e52347bdSJani Nikula 1743e52347bdSJani Nikula ima_template_fmt= 1744e52347bdSJani Nikula [IMA] Define a custom template format. 1745e52347bdSJani Nikula Format: { "field1|...|fieldN" } 1746e52347bdSJani Nikula 1747e52347bdSJani Nikula ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage 1748e52347bdSJani Nikula Format: <min_file_size> 1749e52347bdSJani Nikula Set the minimal file size for using asynchronous hash. 1750e52347bdSJani Nikula If left unspecified, ahash usage is disabled. 1751e52347bdSJani Nikula 1752e52347bdSJani Nikula ahash performance varies for different data sizes on 1753e52347bdSJani Nikula different crypto accelerators. This option can be used 1754e52347bdSJani Nikula to achieve the best performance for a particular HW. 1755e52347bdSJani Nikula 1756e52347bdSJani Nikula ima.ahash_bufsize= [IMA] Asynchronous hash buffer size 1757e52347bdSJani Nikula Format: <bufsize> 1758e52347bdSJani Nikula Set hashing buffer size. Default: 4k. 1759e52347bdSJani Nikula 1760e52347bdSJani Nikula ahash performance varies for different chunk sizes on 1761e52347bdSJani Nikula different crypto accelerators. This option can be used 1762e52347bdSJani Nikula to achieve best performance for particular HW. 1763e52347bdSJani Nikula 1764e52347bdSJani Nikula init= [KNL] 1765e52347bdSJani Nikula Format: <full_path> 1766e52347bdSJani Nikula Run specified binary instead of /sbin/init as init 1767e52347bdSJani Nikula process. 1768e52347bdSJani Nikula 1769e52347bdSJani Nikula initcall_debug [KNL] Trace initcalls as they are executed. Useful 1770e52347bdSJani Nikula for working out where the kernel is dying during 1771e52347bdSJani Nikula startup. 1772e52347bdSJani Nikula 1773e52347bdSJani Nikula initcall_blacklist= [KNL] Do not execute a comma-separated list of 1774e52347bdSJani Nikula initcall functions. Useful for debugging built-in 1775e52347bdSJani Nikula modules and initcalls. 1776e52347bdSJani Nikula 1777e52347bdSJani Nikula initrd= [BOOT] Specify the location of the initial ramdisk 1778e52347bdSJani Nikula 1779694cfd87SRonald G. Minnich initrdmem= [KNL] Specify a physical address and size from which to 1780694cfd87SRonald G. Minnich load the initrd. If an initrd is compiled in or 1781694cfd87SRonald G. Minnich specified in the bootparams, it takes priority over this 1782694cfd87SRonald G. Minnich setting. 1783694cfd87SRonald G. Minnich Format: ss[KMG],nn[KMG] 1784694cfd87SRonald G. Minnich Default is 0, 0 1785694cfd87SRonald G. Minnich 17866471384aSAlexander Potapenko init_on_alloc= [MM] Fill newly allocated pages and heap objects with 17876471384aSAlexander Potapenko zeroes. 17886471384aSAlexander Potapenko Format: 0 | 1 17896471384aSAlexander Potapenko Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON. 17906471384aSAlexander Potapenko 17916471384aSAlexander Potapenko init_on_free= [MM] Fill freed pages and heap objects with zeroes. 17926471384aSAlexander Potapenko Format: 0 | 1 17936471384aSAlexander Potapenko Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON. 17946471384aSAlexander Potapenko 1795e52347bdSJani Nikula init_pkru= [x86] Specify the default memory protection keys rights 1796e52347bdSJani Nikula register contents for all processes. 0x55555554 by 1797e52347bdSJani Nikula default (disallow access to all but pkey 0). Can 1798e52347bdSJani Nikula override in debugfs after boot. 1799e52347bdSJani Nikula 1800e52347bdSJani Nikula inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 1801e52347bdSJani Nikula Format: <irq> 1802e52347bdSJani Nikula 1803e52347bdSJani Nikula int_pln_enable [x86] Enable power limit notification interrupt 1804e52347bdSJani Nikula 1805e52347bdSJani Nikula integrity_audit=[IMA] 1806e52347bdSJani Nikula Format: { "0" | "1" } 1807e52347bdSJani Nikula 0 -- basic integrity auditing messages. (Default) 1808e52347bdSJani Nikula 1 -- additional integrity auditing messages. 1809e52347bdSJani Nikula 1810e52347bdSJani Nikula intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 1811e52347bdSJani Nikula on 1812e52347bdSJani Nikula Enable intel iommu driver. 1813e52347bdSJani Nikula off 1814e52347bdSJani Nikula Disable intel iommu driver. 1815e52347bdSJani Nikula igfx_off [Default Off] 1816e52347bdSJani Nikula By default, gfx is mapped as normal device. If a gfx 1817e52347bdSJani Nikula device has a dedicated DMAR unit, the DMAR unit is 1818e52347bdSJani Nikula bypassed by not enabling DMAR with this option. In 1819e52347bdSJani Nikula this case, gfx device will use physical address for 1820e52347bdSJani Nikula DMA. 1821e52347bdSJani Nikula forcedac [x86_64] 1822e52347bdSJani Nikula With this option iommu will not optimize to look 1823e52347bdSJani Nikula for io virtual address below 32-bit forcing dual 1824e52347bdSJani Nikula address cycle on pci bus for cards supporting greater 1825e52347bdSJani Nikula than 32-bit addressing. The default is to look 1826e52347bdSJani Nikula for translation below 32-bit and if not available 1827e52347bdSJani Nikula then look in the higher range. 1828e52347bdSJani Nikula strict [Default Off] 1829e52347bdSJani Nikula With this option on every unmap_single operation will 1830e52347bdSJani Nikula result in a hardware IOTLB flush operation as opposed 1831e52347bdSJani Nikula to batching them for performance. 1832e52347bdSJani Nikula sp_off [Default Off] 1833e52347bdSJani Nikula By default, super page will be supported if Intel IOMMU 1834e52347bdSJani Nikula has the capability. With this option, super page will 1835e52347bdSJani Nikula not be supported. 18368950dcd8SLu Baolu sm_on [Default Off] 18378950dcd8SLu Baolu By default, scalable mode will be disabled even if the 1838765b6a98SLu Baolu hardware advertises that it has support for the scalable 1839765b6a98SLu Baolu mode translation. With this option set, scalable mode 18408950dcd8SLu Baolu will be used on hardware which claims to support it. 1841bfd20f1cSShaohua Li tboot_noforce [Default Off] 1842bfd20f1cSShaohua Li Do not force the Intel IOMMU enabled under tboot. 1843bfd20f1cSShaohua Li By default, tboot will force Intel IOMMU on, which 1844bfd20f1cSShaohua Li could harm performance of some high-throughput 1845bfd20f1cSShaohua Li devices like 40GBit network cards, even if identity 1846bfd20f1cSShaohua Li mapping is enabled. 1847bfd20f1cSShaohua Li Note that using this option lowers the security 1848bfd20f1cSShaohua Li provided by tboot because it makes the system 1849bfd20f1cSShaohua Li vulnerable to DMA attacks. 1850e5e04d05SLu Baolu nobounce [Default off] 1851bf347b9dSAlex Hung Disable bounce buffer for untrusted devices such as 1852e5e04d05SLu Baolu the Thunderbolt devices. This will treat the untrusted 1853e5e04d05SLu Baolu devices as the trusted ones, hence might expose security 1854e5e04d05SLu Baolu risks of DMA attacks. 1855e52347bdSJani Nikula 1856e52347bdSJani Nikula intel_idle.max_cstate= [KNL,HW,ACPI,X86] 1857e52347bdSJani Nikula 0 disables intel_idle and fall back on acpi_idle. 1858e52347bdSJani Nikula 1 to 9 specify maximum depth of C-state. 1859e52347bdSJani Nikula 1860e52347bdSJani Nikula intel_pstate= [X86] 1861e52347bdSJani Nikula disable 1862e52347bdSJani Nikula Do not enable intel_pstate as the default 1863e52347bdSJani Nikula scaling driver for the supported processors 18647b9dc3f7SLinus Torvalds passive 18657b9dc3f7SLinus Torvalds Use intel_pstate as a scaling driver, but configure it 18667b9dc3f7SLinus Torvalds to work with generic cpufreq governors (instead of 18677b9dc3f7SLinus Torvalds enabling its internal governor). This mode cannot be 18687b9dc3f7SLinus Torvalds used along with the hardware-managed P-states (HWP) 18697b9dc3f7SLinus Torvalds feature. 1870e52347bdSJani Nikula force 1871e52347bdSJani Nikula Enable intel_pstate on systems that prohibit it by default 1872e52347bdSJani Nikula in favor of acpi-cpufreq. Forcing the intel_pstate driver 1873e52347bdSJani Nikula instead of acpi-cpufreq may disable platform features, such 1874e52347bdSJani Nikula as thermal controls and power capping, that rely on ACPI 1875e52347bdSJani Nikula P-States information being indicated to OSPM and therefore 1876e52347bdSJani Nikula should be used with caution. This option does not work with 1877e52347bdSJani Nikula processors that aren't supported by the intel_pstate driver 1878e52347bdSJani Nikula or on platforms that use pcc-cpufreq instead of acpi-cpufreq. 1879e52347bdSJani Nikula no_hwp 1880e52347bdSJani Nikula Do not enable hardware P state control (HWP) 1881e52347bdSJani Nikula if available. 1882e52347bdSJani Nikula hwp_only 1883e52347bdSJani Nikula Only load intel_pstate on systems which support 1884e52347bdSJani Nikula hardware P state control (HWP) if available. 1885e52347bdSJani Nikula support_acpi_ppc 1886e52347bdSJani Nikula Enforce ACPI _PPC performance limits. If the Fixed ACPI 1887e52347bdSJani Nikula Description Table, specifies preferred power management 1888e52347bdSJani Nikula profile as "Enterprise Server" or "Performance Server", 1889e52347bdSJani Nikula then this feature is turned on by default. 18907b9dc3f7SLinus Torvalds per_cpu_perf_limits 18917b9dc3f7SLinus Torvalds Allow per-logical-CPU P-State performance control limits using 18927b9dc3f7SLinus Torvalds cpufreq sysfs interface 1893e52347bdSJani Nikula 1894e52347bdSJani Nikula intremap= [X86-64, Intel-IOMMU] 1895e52347bdSJani Nikula on enable Interrupt Remapping (default) 1896e52347bdSJani Nikula off disable Interrupt Remapping 1897e52347bdSJani Nikula nosid disable Source ID checking 1898e52347bdSJani Nikula no_x2apic_optout 1899e52347bdSJani Nikula BIOS x2APIC opt-out request will be ignored 1900e52347bdSJani Nikula nopost disable Interrupt Posting 1901e52347bdSJani Nikula 1902e52347bdSJani Nikula iomem= Disable strict checking of access to MMIO memory 1903e52347bdSJani Nikula strict regions from userspace. 1904e52347bdSJani Nikula relaxed 1905e52347bdSJani Nikula 1906e52347bdSJani Nikula iommu= [x86] 1907e52347bdSJani Nikula off 1908e52347bdSJani Nikula force 1909e52347bdSJani Nikula noforce 1910e52347bdSJani Nikula biomerge 1911e52347bdSJani Nikula panic 1912e52347bdSJani Nikula nopanic 1913e52347bdSJani Nikula merge 1914e52347bdSJani Nikula nomerge 1915e52347bdSJani Nikula soft 191658d11317SOlof Johansson pt [x86] 191758d11317SOlof Johansson nopt [x86] 1918e52347bdSJani Nikula nobypass [PPC/POWERNV] 1919e52347bdSJani Nikula Disable IOMMU bypass, using IOMMU for PCI devices. 1920e52347bdSJani Nikula 192168a6efe8SZhen Lei iommu.strict= [ARM64] Configure TLB invalidation behaviour 192268a6efe8SZhen Lei Format: { "0" | "1" } 192368a6efe8SZhen Lei 0 - Lazy mode. 192468a6efe8SZhen Lei Request that DMA unmap operations use deferred 192568a6efe8SZhen Lei invalidation of hardware TLBs, for increased 192668a6efe8SZhen Lei throughput at the cost of reduced device isolation. 192768a6efe8SZhen Lei Will fall back to strict mode if not supported by 192868a6efe8SZhen Lei the relevant IOMMU driver. 192968a6efe8SZhen Lei 1 - Strict mode (default). 193068a6efe8SZhen Lei DMA unmap operations invalidate IOMMU hardware TLBs 193168a6efe8SZhen Lei synchronously. 193268a6efe8SZhen Lei 1933fccb4e3bSWill Deacon iommu.passthrough= 1934c8fb436bSJoerg Roedel [ARM64, X86] Configure DMA to bypass the IOMMU by default. 1935fccb4e3bSWill Deacon Format: { "0" | "1" } 1936fccb4e3bSWill Deacon 0 - Use IOMMU translation for DMA. 1937fccb4e3bSWill Deacon 1 - Bypass the IOMMU for DMA. 19389d723b4cSRobin Murphy unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. 1939e52347bdSJani Nikula 1940e52347bdSJani Nikula io7= [HW] IO7 for Marvel based alpha systems 1941e52347bdSJani Nikula See comment before marvel_specify_io7 in 1942e52347bdSJani Nikula arch/alpha/kernel/core_marvel.c. 1943e52347bdSJani Nikula 1944e52347bdSJani Nikula io_delay= [X86] I/O delay method 1945e52347bdSJani Nikula 0x80 1946e52347bdSJani Nikula Standard port 0x80 based delay 1947e52347bdSJani Nikula 0xed 1948e52347bdSJani Nikula Alternate port 0xed based delay (needed on some systems) 1949e52347bdSJani Nikula udelay 1950e52347bdSJani Nikula Simple two microseconds delay 1951e52347bdSJani Nikula none 1952e52347bdSJani Nikula No delay 1953e52347bdSJani Nikula 1954e52347bdSJani Nikula ip= [IP_PNP] 19553eb30c51SNiklas Söderlund See Documentation/admin-guide/nfs/nfsroot.rst. 1956e52347bdSJani Nikula 19575ac893b8SWaiman Long ipcmni_extend [KNL] Extend the maximum number of unique System V 19585ac893b8SWaiman Long IPC identifiers from 32,768 to 16,777,216. 19595ac893b8SWaiman Long 1960e52347bdSJani Nikula irqaffinity= [SMP] Set the default irq affinity mask 1961e52347bdSJani Nikula The argument is a cpu list, as described above. 1962e52347bdSJani Nikula 19630962289bSMarc Zyngier irqchip.gicv2_force_probe= 19640962289bSMarc Zyngier [ARM, ARM64] 19650962289bSMarc Zyngier Format: <bool> 19660962289bSMarc Zyngier Force the kernel to look for the second 4kB page 19670962289bSMarc Zyngier of a GICv2 controller even if the memory range 19680962289bSMarc Zyngier exposed by the device tree is too small. 19690962289bSMarc Zyngier 1970f736d65dSMarc Zyngier irqchip.gicv3_nolpi= 1971f736d65dSMarc Zyngier [ARM, ARM64] 1972f736d65dSMarc Zyngier Force the kernel to ignore the availability of 1973f736d65dSMarc Zyngier LPIs (and by consequence ITSs). Intended for system 1974f736d65dSMarc Zyngier that use the kernel as a bootloader, and thus want 1975f736d65dSMarc Zyngier to let secondary kernels in charge of setting up 1976f736d65dSMarc Zyngier LPIs. 1977f736d65dSMarc Zyngier 1978bc3c03ccSJulien Thierry irqchip.gicv3_pseudo_nmi= [ARM64] 1979bc3c03ccSJulien Thierry Enables support for pseudo-NMIs in the kernel. This 1980bc3c03ccSJulien Thierry requires the kernel to be built with 1981bc3c03ccSJulien Thierry CONFIG_ARM64_PSEUDO_NMI. 1982bc3c03ccSJulien Thierry 1983e52347bdSJani Nikula irqfixup [HW] 1984e52347bdSJani Nikula When an interrupt is not handled search all handlers 1985e52347bdSJani Nikula for it. Intended to get systems with badly broken 1986e52347bdSJani Nikula firmware running. 1987e52347bdSJani Nikula 1988e52347bdSJani Nikula irqpoll [HW] 1989e52347bdSJani Nikula When an interrupt is not handled search all handlers 1990e52347bdSJani Nikula for it. Also check all handlers each timer 1991e52347bdSJani Nikula interrupt. Intended to get systems with badly broken 1992e52347bdSJani Nikula firmware running. 1993e52347bdSJani Nikula 1994e52347bdSJani Nikula isapnp= [ISAPNP] 1995e52347bdSJani Nikula Format: <RDP>,<reset>,<pci_scan>,<verbosity> 1996e52347bdSJani Nikula 1997d94d1053SFrederic Weisbecker isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance. 1998b0d40d2bSFrederic Weisbecker [Deprecated - use cpusets instead] 1999b0d40d2bSFrederic Weisbecker Format: [flag-list,]<cpu-list> 2000e52347bdSJani Nikula 2001b0d40d2bSFrederic Weisbecker Specify one or more CPUs to isolate from disturbances 2002b0d40d2bSFrederic Weisbecker specified in the flag list (default: domain): 2003b0d40d2bSFrederic Weisbecker 2004b0d40d2bSFrederic Weisbecker nohz 2005b0d40d2bSFrederic Weisbecker Disable the tick when a single task runs. 2006083c6eeaSFrederic Weisbecker 2007083c6eeaSFrederic Weisbecker A residual 1Hz tick is offloaded to workqueues, which you 2008083c6eeaSFrederic Weisbecker need to affine to housekeeping through the global 2009083c6eeaSFrederic Weisbecker workqueue's affinity configured via the 2010083c6eeaSFrederic Weisbecker /sys/devices/virtual/workqueue/cpumask sysfs file, or 2011083c6eeaSFrederic Weisbecker by using the 'domain' flag described below. 2012083c6eeaSFrederic Weisbecker 2013083c6eeaSFrederic Weisbecker NOTE: by default the global workqueue runs on all CPUs, 2014083c6eeaSFrederic Weisbecker so to protect individual CPUs the 'cpumask' file has to 2015083c6eeaSFrederic Weisbecker be configured manually after bootup. 2016083c6eeaSFrederic Weisbecker 2017b0d40d2bSFrederic Weisbecker domain 2018b0d40d2bSFrederic Weisbecker Isolate from the general SMP balancing and scheduling 2019b0d40d2bSFrederic Weisbecker algorithms. Note that performing domain isolation this way 2020b0d40d2bSFrederic Weisbecker is irreversible: it's not possible to bring back a CPU to 2021b0d40d2bSFrederic Weisbecker the domains once isolated through isolcpus. It's strongly 2022b0d40d2bSFrederic Weisbecker advised to use cpusets instead to disable scheduler load 2023b0d40d2bSFrederic Weisbecker balancing through the "cpuset.sched_load_balance" file. 2024b0d40d2bSFrederic Weisbecker It offers a much more flexible interface where CPUs can 2025b0d40d2bSFrederic Weisbecker move in and out of an isolated set anytime. 2026b0d40d2bSFrederic Weisbecker 2027b0d40d2bSFrederic Weisbecker You can move a process onto or off an "isolated" CPU via 2028b0d40d2bSFrederic Weisbecker the CPU affinity syscalls or cpuset. 2029e52347bdSJani Nikula <cpu number> begins at 0 and the maximum value is 2030e52347bdSJani Nikula "number of CPUs in system - 1". 2031e52347bdSJani Nikula 203211ea68f5SMing Lei managed_irq 203311ea68f5SMing Lei 203411ea68f5SMing Lei Isolate from being targeted by managed interrupts 203511ea68f5SMing Lei which have an interrupt mask containing isolated 203611ea68f5SMing Lei CPUs. The affinity of managed interrupts is 203711ea68f5SMing Lei handled by the kernel and cannot be changed via 203811ea68f5SMing Lei the /proc/irq/* interfaces. 203911ea68f5SMing Lei 204011ea68f5SMing Lei This isolation is best effort and only effective 204111ea68f5SMing Lei if the automatically assigned interrupt mask of a 204211ea68f5SMing Lei device queue contains isolated and housekeeping 204311ea68f5SMing Lei CPUs. If housekeeping CPUs are online then such 204411ea68f5SMing Lei interrupts are directed to the housekeeping CPU 204511ea68f5SMing Lei so that IO submitted on the housekeeping CPU 204611ea68f5SMing Lei cannot disturb the isolated CPU. 204711ea68f5SMing Lei 204811ea68f5SMing Lei If a queue's affinity mask contains only isolated 204911ea68f5SMing Lei CPUs then this parameter has no effect on the 205011ea68f5SMing Lei interrupt routing decision, though interrupts are 205111ea68f5SMing Lei only delivered when tasks running on those 205211ea68f5SMing Lei isolated CPUs submit IO. IO submitted on 205311ea68f5SMing Lei housekeeping CPUs has no influence on those 205411ea68f5SMing Lei queues. 205511ea68f5SMing Lei 2056b0d40d2bSFrederic Weisbecker The format of <cpu-list> is described above. 2057b0d40d2bSFrederic Weisbecker 2058e52347bdSJani Nikula iucv= [HW,NET] 2059e52347bdSJani Nikula 2060e52347bdSJani Nikula ivrs_ioapic [HW,X86_64] 2061e52347bdSJani Nikula Provide an override to the IOAPIC-ID<->DEVICE-ID 2062e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 2063e52347bdSJani Nikula example, to map IOAPIC-ID decimal 10 to 2064e52347bdSJani Nikula PCI device 00:14.0 write the parameter as: 2065e52347bdSJani Nikula ivrs_ioapic[10]=00:14.0 2066e52347bdSJani Nikula 2067e52347bdSJani Nikula ivrs_hpet [HW,X86_64] 2068e52347bdSJani Nikula Provide an override to the HPET-ID<->DEVICE-ID 2069e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 2070e52347bdSJani Nikula example, to map HPET-ID decimal 0 to 2071e52347bdSJani Nikula PCI device 00:14.0 write the parameter as: 2072e52347bdSJani Nikula ivrs_hpet[0]=00:14.0 2073e52347bdSJani Nikula 2074e52347bdSJani Nikula ivrs_acpihid [HW,X86_64] 2075e52347bdSJani Nikula Provide an override to the ACPI-HID:UID<->DEVICE-ID 2076e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 2077e52347bdSJani Nikula example, to map UART-HID:UID AMD0020:0 to 2078e52347bdSJani Nikula PCI device 00:14.5 write the parameter as: 2079e52347bdSJani Nikula ivrs_acpihid[00:14.5]=AMD0020:0 2080e52347bdSJani Nikula 2081e52347bdSJani Nikula js= [HW,JOY] Analog joystick 20821752118dSTom Saeger See Documentation/input/joydev/joystick.rst. 2083e52347bdSJani Nikula 2084e52347bdSJani Nikula nokaslr [KNL] 2085e52347bdSJani Nikula When CONFIG_RANDOMIZE_BASE is set, this disables 2086e52347bdSJani Nikula kernel and module base offset ASLR (Address Space 2087e52347bdSJani Nikula Layout Randomization). 2088e52347bdSJani Nikula 2089b0845ce5SMark Rutland kasan_multi_shot 2090b0845ce5SMark Rutland [KNL] Enforce KASAN (Kernel Address Sanitizer) to print 2091b0845ce5SMark Rutland report on every invalid memory access. Without this 2092b0845ce5SMark Rutland parameter KASAN will print report only for the first 2093b0845ce5SMark Rutland invalid access. 2094b0845ce5SMark Rutland 2095e52347bdSJani Nikula keepinitrd [HW,ARM] 2096e52347bdSJani Nikula 2097e52347bdSJani Nikula kernelcore= [KNL,X86,IA-64,PPC] 2098a5c6d650SDavid Rientjes Format: nn[KMGTPE] | nn% | "mirror" 2099a5c6d650SDavid Rientjes This parameter specifies the amount of memory usable by 2100a5c6d650SDavid Rientjes the kernel for non-movable allocations. The requested 2101a5c6d650SDavid Rientjes amount is spread evenly throughout all nodes in the 2102a5c6d650SDavid Rientjes system as ZONE_NORMAL. The remaining memory is used for 2103a5c6d650SDavid Rientjes movable memory in its own zone, ZONE_MOVABLE. In the 2104a5c6d650SDavid Rientjes event, a node is too small to have both ZONE_NORMAL and 2105a5c6d650SDavid Rientjes ZONE_MOVABLE, kernelcore memory will take priority and 2106a5c6d650SDavid Rientjes other nodes will have a larger ZONE_MOVABLE. 2107a5c6d650SDavid Rientjes 2108a5c6d650SDavid Rientjes ZONE_MOVABLE is used for the allocation of pages that 2109a5c6d650SDavid Rientjes may be reclaimed or moved by the page migration 2110a5c6d650SDavid Rientjes subsystem. Note that allocations like PTEs-from-HighMem 2111a5c6d650SDavid Rientjes still use the HighMem zone if it exists, and the Normal 2112e52347bdSJani Nikula zone if it does not. 2113e52347bdSJani Nikula 2114a5c6d650SDavid Rientjes It is possible to specify the exact amount of memory in 2115a5c6d650SDavid Rientjes the form of "nn[KMGTPE]", a percentage of total system 2116a5c6d650SDavid Rientjes memory in the form of "nn%", or "mirror". If "mirror" 2117e52347bdSJani Nikula option is specified, mirrored (reliable) memory is used 2118e52347bdSJani Nikula for non-movable allocations and remaining memory is used 2119a5c6d650SDavid Rientjes for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" 2120a5c6d650SDavid Rientjes are exclusive, so you cannot specify multiple forms. 2121e52347bdSJani Nikula 2122e52347bdSJani Nikula kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. 2123e52347bdSJani Nikula Format: <Controller#>[,poll interval] 2124e52347bdSJani Nikula The controller # is the number of the ehci usb debug 2125e52347bdSJani Nikula port as it is probed via PCI. The poll interval is 2126e52347bdSJani Nikula optional and is the number seconds in between 2127e52347bdSJani Nikula each poll cycle to the debug port in case you need 2128e52347bdSJani Nikula the functionality for interrupting the kernel with 2129e52347bdSJani Nikula gdb or control-c on the dbgp connection. When 2130e52347bdSJani Nikula not using this parameter you use sysrq-g to break into 2131e52347bdSJani Nikula the kernel debugger. 2132e52347bdSJani Nikula 2133e52347bdSJani Nikula kgdboc= [KGDB,HW] kgdb over consoles. 2134e52347bdSJani Nikula Requires a tty driver that supports console polling, 2135e52347bdSJani Nikula or a supported polling keyboard driver (non-usb). 2136e52347bdSJani Nikula Serial only format: <serial_device>[,baud] 2137e52347bdSJani Nikula keyboard only format: kbd 2138e52347bdSJani Nikula keyboard and serial format: kbd,<serial_device>[,baud] 2139e52347bdSJani Nikula Optional Kernel mode setting: 2140e52347bdSJani Nikula kms, kbd format: kms,kbd 2141e52347bdSJani Nikula kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] 2142e52347bdSJani Nikula 2143f71fc3bcSDouglas Anderson kgdboc_earlycon= [KGDB,HW] 2144f71fc3bcSDouglas Anderson If the boot console provides the ability to read 2145f71fc3bcSDouglas Anderson characters and can work in polling mode, you can use 2146f71fc3bcSDouglas Anderson this parameter to tell kgdb to use it as a backend 2147f71fc3bcSDouglas Anderson until the normal console is registered. Intended to 2148f71fc3bcSDouglas Anderson be used together with the kgdboc parameter which 2149f71fc3bcSDouglas Anderson specifies the normal console to transition to. 2150f71fc3bcSDouglas Anderson 2151f71fc3bcSDouglas Anderson The name of the early console should be specified 2152f71fc3bcSDouglas Anderson as the value of this parameter. Note that the name of 2153f71fc3bcSDouglas Anderson the early console might be different than the tty 2154f71fc3bcSDouglas Anderson name passed to kgdboc. It's OK to leave the value 2155f71fc3bcSDouglas Anderson blank and the first boot console that implements 2156f71fc3bcSDouglas Anderson read() will be picked. 2157f71fc3bcSDouglas Anderson 2158e52347bdSJani Nikula kgdbwait [KGDB] Stop kernel execution and enter the 2159e52347bdSJani Nikula kernel debugger at the earliest opportunity. 2160e52347bdSJani Nikula 2161e52347bdSJani Nikula kmac= [MIPS] korina ethernet MAC address. 2162e52347bdSJani Nikula Configure the RouterBoard 532 series on-chip 2163e52347bdSJani Nikula Ethernet adapter MAC address. 2164e52347bdSJani Nikula 2165e52347bdSJani Nikula kmemleak= [KNL] Boot-time kmemleak enable/disable 2166e52347bdSJani Nikula Valid arguments: on, off 2167e52347bdSJani Nikula Default: on 2168e52347bdSJani Nikula Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, 2169e52347bdSJani Nikula the default is off. 2170e52347bdSJani Nikula 2171970988e1SMasami Hiramatsu kprobe_event=[probe-list] 2172970988e1SMasami Hiramatsu [FTRACE] Add kprobe events and enable at boot time. 2173970988e1SMasami Hiramatsu The probe-list is a semicolon delimited list of probe 2174970988e1SMasami Hiramatsu definitions. Each definition is same as kprobe_events 2175970988e1SMasami Hiramatsu interface, but the parameters are comma delimited. 2176970988e1SMasami Hiramatsu For example, to add a kprobe event on vfs_read with 2177970988e1SMasami Hiramatsu arg1 and arg2, add to the command line; 2178970988e1SMasami Hiramatsu 2179970988e1SMasami Hiramatsu kprobe_event=p,vfs_read,$arg1,$arg2 2180970988e1SMasami Hiramatsu 2181970988e1SMasami Hiramatsu See also Documentation/trace/kprobetrace.rst "Kernel 2182970988e1SMasami Hiramatsu Boot Parameter" section. 2183970988e1SMasami Hiramatsu 2184de190555SJeremy Linton kpti= [ARM64] Control page table isolation of user 2185de190555SJeremy Linton and kernel address spaces. 2186de190555SJeremy Linton Default: enabled on cores which need mitigation. 2187de190555SJeremy Linton 0: force disabled 2188de190555SJeremy Linton 1: force enabled 2189de190555SJeremy Linton 2190e52347bdSJani Nikula kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. 2191e52347bdSJani Nikula Default is 0 (don't ignore, but inject #GP) 2192e52347bdSJani Nikula 2193c4ae60e4SLiran Alon kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface. 2194c4ae60e4SLiran Alon Default is false (don't support). 2195c4ae60e4SLiran Alon 2196e52347bdSJani Nikula kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit 2197e52347bdSJani Nikula KVM MMU at runtime. 2198e52347bdSJani Nikula Default is 0 (off) 2199e52347bdSJani Nikula 2200b8e8c830SPaolo Bonzini kvm.nx_huge_pages= 2201b8e8c830SPaolo Bonzini [KVM] Controls the software workaround for the 2202b8e8c830SPaolo Bonzini X86_BUG_ITLB_MULTIHIT bug. 2203b8e8c830SPaolo Bonzini force : Always deploy workaround. 2204b8e8c830SPaolo Bonzini off : Never deploy workaround. 2205b8e8c830SPaolo Bonzini auto : Deploy workaround based on the presence of 2206b8e8c830SPaolo Bonzini X86_BUG_ITLB_MULTIHIT. 2207b8e8c830SPaolo Bonzini 2208b8e8c830SPaolo Bonzini Default is 'auto'. 2209b8e8c830SPaolo Bonzini 2210b8e8c830SPaolo Bonzini If the software workaround is enabled for the host, 2211b8e8c830SPaolo Bonzini guests do need not to enable it for nested guests. 2212b8e8c830SPaolo Bonzini 22131aa9b957SJunaid Shahid kvm.nx_huge_pages_recovery_ratio= 22141aa9b957SJunaid Shahid [KVM] Controls how many 4KiB pages are periodically zapped 22151aa9b957SJunaid Shahid back to huge pages. 0 disables the recovery, otherwise if 22161aa9b957SJunaid Shahid the value is N KVM will zap 1/Nth of the 4KiB pages every 22171aa9b957SJunaid Shahid minute. The default is 60. 22181aa9b957SJunaid Shahid 2219e52347bdSJani Nikula kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. 2220e52347bdSJani Nikula Default is 1 (enabled) 2221e52347bdSJani Nikula 2222e52347bdSJani Nikula kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) 2223e52347bdSJani Nikula for all guests. 2224e52347bdSJani Nikula Default is 1 (enabled) if in 64-bit or 32-bit PAE mode. 2225e52347bdSJani Nikula 2226e23f62f7SMarc Zyngier kvm-arm.vgic_v3_group0_trap= 2227e23f62f7SMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 group-0 2228e23f62f7SMarc Zyngier system registers 2229e23f62f7SMarc Zyngier 2230182936eeSMarc Zyngier kvm-arm.vgic_v3_group1_trap= 2231182936eeSMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 group-1 2232182936eeSMarc Zyngier system registers 2233182936eeSMarc Zyngier 2234ff89511eSMarc Zyngier kvm-arm.vgic_v3_common_trap= 2235ff89511eSMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 common 2236ff89511eSMarc Zyngier system registers 2237ff89511eSMarc Zyngier 2238a7546054SMarc Zyngier kvm-arm.vgic_v4_enable= 2239a7546054SMarc Zyngier [KVM,ARM] Allow use of GICv4 for direct injection of 2240a7546054SMarc Zyngier LPIs. 2241a7546054SMarc Zyngier 2242e52347bdSJani Nikula kvm-intel.ept= [KVM,Intel] Disable extended page tables 2243e52347bdSJani Nikula (virtualized MMU) support on capable Intel chips. 2244e52347bdSJani Nikula Default is 1 (enabled) 2245e52347bdSJani Nikula 2246e52347bdSJani Nikula kvm-intel.emulate_invalid_guest_state= 2247e52347bdSJani Nikula [KVM,Intel] Enable emulation of invalid guest states 2248e52347bdSJani Nikula Default is 0 (disabled) 2249e52347bdSJani Nikula 2250e52347bdSJani Nikula kvm-intel.flexpriority= 2251e52347bdSJani Nikula [KVM,Intel] Disable FlexPriority feature (TPR shadow). 2252e52347bdSJani Nikula Default is 1 (enabled) 2253e52347bdSJani Nikula 2254e52347bdSJani Nikula kvm-intel.nested= 2255e52347bdSJani Nikula [KVM,Intel] Enable VMX nesting (nVMX). 2256e52347bdSJani Nikula Default is 0 (disabled) 2257e52347bdSJani Nikula 2258e52347bdSJani Nikula kvm-intel.unrestricted_guest= 2259e52347bdSJani Nikula [KVM,Intel] Disable unrestricted guest feature 2260e52347bdSJani Nikula (virtualized real and unpaged mode) on capable 2261e52347bdSJani Nikula Intel chips. Default is 1 (enabled) 2262e52347bdSJani Nikula 2263a399477eSKonrad Rzeszutek Wilk kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault 2264a399477eSKonrad Rzeszutek Wilk CVE-2018-3620. 2265a399477eSKonrad Rzeszutek Wilk 2266a399477eSKonrad Rzeszutek Wilk Valid arguments: never, cond, always 2267a399477eSKonrad Rzeszutek Wilk 2268a399477eSKonrad Rzeszutek Wilk always: L1D cache flush on every VMENTER. 2269a399477eSKonrad Rzeszutek Wilk cond: Flush L1D on VMENTER only when the code between 2270a399477eSKonrad Rzeszutek Wilk VMEXIT and VMENTER can leak host memory. 2271a399477eSKonrad Rzeszutek Wilk never: Disables the mitigation 2272a399477eSKonrad Rzeszutek Wilk 2273a399477eSKonrad Rzeszutek Wilk Default is cond (do L1 cache flush in specific instances) 2274a399477eSKonrad Rzeszutek Wilk 2275e52347bdSJani Nikula kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification 2276e52347bdSJani Nikula feature (tagged TLBs) on capable Intel chips. 2277e52347bdSJani Nikula Default is 1 (enabled) 2278e52347bdSJani Nikula 2279d90a7a0eSJiri Kosina l1tf= [X86] Control mitigation of the L1TF vulnerability on 2280d90a7a0eSJiri Kosina affected CPUs 2281d90a7a0eSJiri Kosina 2282d90a7a0eSJiri Kosina The kernel PTE inversion protection is unconditionally 2283d90a7a0eSJiri Kosina enabled and cannot be disabled. 2284d90a7a0eSJiri Kosina 2285d90a7a0eSJiri Kosina full 2286d90a7a0eSJiri Kosina Provides all available mitigations for the 2287d90a7a0eSJiri Kosina L1TF vulnerability. Disables SMT and 2288d90a7a0eSJiri Kosina enables all mitigations in the 2289d90a7a0eSJiri Kosina hypervisors, i.e. unconditional L1D flush. 2290d90a7a0eSJiri Kosina 2291d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2292d90a7a0eSJiri Kosina sysfs interface is still possible after 2293d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2294d90a7a0eSJiri Kosina when the first VM is started in a 2295d90a7a0eSJiri Kosina potentially insecure configuration, 2296d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2297d90a7a0eSJiri Kosina 2298d90a7a0eSJiri Kosina full,force 2299d90a7a0eSJiri Kosina Same as 'full', but disables SMT and L1D 2300d90a7a0eSJiri Kosina flush runtime control. Implies the 2301d90a7a0eSJiri Kosina 'nosmt=force' command line option. 2302d90a7a0eSJiri Kosina (i.e. sysfs control of SMT is disabled.) 2303d90a7a0eSJiri Kosina 2304d90a7a0eSJiri Kosina flush 2305d90a7a0eSJiri Kosina Leaves SMT enabled and enables the default 2306d90a7a0eSJiri Kosina hypervisor mitigation, i.e. conditional 2307d90a7a0eSJiri Kosina L1D flush. 2308d90a7a0eSJiri Kosina 2309d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2310d90a7a0eSJiri Kosina sysfs interface is still possible after 2311d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2312d90a7a0eSJiri Kosina when the first VM is started in a 2313d90a7a0eSJiri Kosina potentially insecure configuration, 2314d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2315d90a7a0eSJiri Kosina 2316d90a7a0eSJiri Kosina flush,nosmt 2317d90a7a0eSJiri Kosina 2318d90a7a0eSJiri Kosina Disables SMT and enables the default 2319d90a7a0eSJiri Kosina hypervisor mitigation. 2320d90a7a0eSJiri Kosina 2321d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2322d90a7a0eSJiri Kosina sysfs interface is still possible after 2323d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2324d90a7a0eSJiri Kosina when the first VM is started in a 2325d90a7a0eSJiri Kosina potentially insecure configuration, 2326d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2327d90a7a0eSJiri Kosina 2328d90a7a0eSJiri Kosina flush,nowarn 2329d90a7a0eSJiri Kosina Same as 'flush', but hypervisors will not 2330d90a7a0eSJiri Kosina warn when a VM is started in a potentially 2331d90a7a0eSJiri Kosina insecure configuration. 2332d90a7a0eSJiri Kosina 2333d90a7a0eSJiri Kosina off 2334d90a7a0eSJiri Kosina Disables hypervisor mitigations and doesn't 2335d90a7a0eSJiri Kosina emit any warnings. 23365b5e4d62SMichal Hocko It also drops the swap size and available 23375b5e4d62SMichal Hocko RAM limit restriction on both hypervisor and 23385b5e4d62SMichal Hocko bare metal. 2339d90a7a0eSJiri Kosina 2340d90a7a0eSJiri Kosina Default is 'flush'. 2341d90a7a0eSJiri Kosina 234265fd4cb6SThomas Gleixner For details see: Documentation/admin-guide/hw-vuln/l1tf.rst 2343d90a7a0eSJiri Kosina 2344e52347bdSJani Nikula l2cr= [PPC] 2345e52347bdSJani Nikula 2346e52347bdSJani Nikula l3cr= [PPC] 2347e52347bdSJani Nikula 2348e52347bdSJani Nikula lapic [X86-32,APIC] Enable the local APIC even if BIOS 2349e52347bdSJani Nikula disabled it. 2350e52347bdSJani Nikula 2351e52347bdSJani Nikula lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline 2352e52347bdSJani Nikula value for LAPIC timer one-shot implementation. Default 2353e52347bdSJani Nikula back to the programmable timer unit in the LAPIC. 2354e52347bdSJani Nikula 2355e52347bdSJani Nikula lapic_timer_c2_ok [X86,APIC] trust the local apic timer 2356e52347bdSJani Nikula in C2 power state. 2357e52347bdSJani Nikula 2358e52347bdSJani Nikula libata.dma= [LIBATA] DMA control 2359e52347bdSJani Nikula libata.dma=0 Disable all PATA and SATA DMA 2360e52347bdSJani Nikula libata.dma=1 PATA and SATA Disk DMA only 2361e52347bdSJani Nikula libata.dma=2 ATAPI (CDROM) DMA only 2362e52347bdSJani Nikula libata.dma=4 Compact Flash DMA only 2363e52347bdSJani Nikula Combinations also work, so libata.dma=3 enables DMA 2364e52347bdSJani Nikula for disks and CDROMs, but not CFs. 2365e52347bdSJani Nikula 2366e52347bdSJani Nikula libata.ignore_hpa= [LIBATA] Ignore HPA limit 2367e52347bdSJani Nikula libata.ignore_hpa=0 keep BIOS limits (default) 2368e52347bdSJani Nikula libata.ignore_hpa=1 ignore limits, using full disk 2369e52347bdSJani Nikula 2370e52347bdSJani Nikula libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 2371e52347bdSJani Nikula when set. 2372e52347bdSJani Nikula Format: <int> 2373e52347bdSJani Nikula 2374e52347bdSJani Nikula libata.force= [LIBATA] Force configurations. The format is comma 2375e52347bdSJani Nikula separated list of "[ID:]VAL" where ID is 2376e52347bdSJani Nikula PORT[.DEVICE]. PORT and DEVICE are decimal numbers 2377e52347bdSJani Nikula matching port, link or device. Basically, it matches 2378e52347bdSJani Nikula the ATA ID string printed on console by libata. If 2379e52347bdSJani Nikula the whole ID part is omitted, the last PORT and DEVICE 2380e52347bdSJani Nikula values are used. If ID hasn't been specified yet, the 2381e52347bdSJani Nikula configuration applies to all ports, links and devices. 2382e52347bdSJani Nikula 2383e52347bdSJani Nikula If only DEVICE is omitted, the parameter applies to 2384e52347bdSJani Nikula the port and all links and devices behind it. DEVICE 2385e52347bdSJani Nikula number of 0 either selects the first device or the 2386e52347bdSJani Nikula first fan-out link behind PMP device. It does not 2387e52347bdSJani Nikula select the host link. DEVICE number of 15 selects the 2388e52347bdSJani Nikula host link and device attached to it. 2389e52347bdSJani Nikula 2390e52347bdSJani Nikula The VAL specifies the configuration to force. As long 2391e52347bdSJani Nikula as there's no ambiguity shortcut notation is allowed. 2392e52347bdSJani Nikula For example, both 1.5 and 1.5G would work for 1.5Gbps. 2393e52347bdSJani Nikula The following configurations can be forced. 2394e52347bdSJani Nikula 2395e52347bdSJani Nikula * Cable type: 40c, 80c, short40c, unk, ign or sata. 2396e52347bdSJani Nikula Any ID with matching PORT is used. 2397e52347bdSJani Nikula 2398e52347bdSJani Nikula * SATA link speed limit: 1.5Gbps or 3.0Gbps. 2399e52347bdSJani Nikula 2400e52347bdSJani Nikula * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 2401e52347bdSJani Nikula udma[/][16,25,33,44,66,100,133] notation is also 2402e52347bdSJani Nikula allowed. 2403e52347bdSJani Nikula 2404e52347bdSJani Nikula * [no]ncq: Turn on or off NCQ. 2405e52347bdSJani Nikula 2406e52347bdSJani Nikula * [no]ncqtrim: Turn off queued DSM TRIM. 2407e52347bdSJani Nikula 2408e52347bdSJani Nikula * nohrst, nosrst, norst: suppress hard, soft 2409e52347bdSJani Nikula and both resets. 2410e52347bdSJani Nikula 2411e52347bdSJani Nikula * rstonce: only attempt one reset during 2412e52347bdSJani Nikula hot-unplug link recovery 2413e52347bdSJani Nikula 2414e52347bdSJani Nikula * dump_id: dump IDENTIFY data. 2415e52347bdSJani Nikula 2416e52347bdSJani Nikula * atapi_dmadir: Enable ATAPI DMADIR bridge support 2417e52347bdSJani Nikula 2418e52347bdSJani Nikula * disable: Disable this device. 2419e52347bdSJani Nikula 2420e52347bdSJani Nikula If there are multiple matching configurations changing 2421e52347bdSJani Nikula the same attribute, the last one is used. 2422e52347bdSJani Nikula 2423e52347bdSJani Nikula memblock=debug [KNL] Enable memblock debug messages. 2424e52347bdSJani Nikula 2425e52347bdSJani Nikula load_ramdisk= [RAM] List of ramdisks to load from floppy 2426e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/ramdisk.rst. 2427e52347bdSJani Nikula 2428e52347bdSJani Nikula lockd.nlm_grace_period=P [NFS] Assign grace period. 2429e52347bdSJani Nikula Format: <integer> 2430e52347bdSJani Nikula 2431e52347bdSJani Nikula lockd.nlm_tcpport=N [NFS] Assign TCP port. 2432e52347bdSJani Nikula Format: <integer> 2433e52347bdSJani Nikula 2434e52347bdSJani Nikula lockd.nlm_timeout=T [NFS] Assign timeout value. 2435e52347bdSJani Nikula Format: <integer> 2436e52347bdSJani Nikula 2437e52347bdSJani Nikula lockd.nlm_udpport=M [NFS] Assign UDP port. 2438e52347bdSJani Nikula Format: <integer> 2439e52347bdSJani Nikula 2440000d388eSMatthew Garrett lockdown= [SECURITY] 2441000d388eSMatthew Garrett { integrity | confidentiality } 2442000d388eSMatthew Garrett Enable the kernel lockdown feature. If set to 2443000d388eSMatthew Garrett integrity, kernel features that allow userland to 2444000d388eSMatthew Garrett modify the running kernel are disabled. If set to 2445000d388eSMatthew Garrett confidentiality, kernel features that allow userland 2446000d388eSMatthew Garrett to extract confidential information from the kernel 2447000d388eSMatthew Garrett are also disabled. 2448000d388eSMatthew Garrett 2449e52347bdSJani Nikula locktorture.nreaders_stress= [KNL] 2450e52347bdSJani Nikula Set the number of locking read-acquisition kthreads. 2451e52347bdSJani Nikula Defaults to being automatically set based on the 2452e52347bdSJani Nikula number of online CPUs. 2453e52347bdSJani Nikula 2454e52347bdSJani Nikula locktorture.nwriters_stress= [KNL] 2455e52347bdSJani Nikula Set the number of locking write-acquisition kthreads. 2456e52347bdSJani Nikula 2457e52347bdSJani Nikula locktorture.onoff_holdoff= [KNL] 2458e52347bdSJani Nikula Set time (s) after boot for CPU-hotplug testing. 2459e52347bdSJani Nikula 2460e52347bdSJani Nikula locktorture.onoff_interval= [KNL] 2461e52347bdSJani Nikula Set time (s) between CPU-hotplug operations, or 2462e52347bdSJani Nikula zero to disable CPU-hotplug testing. 2463e52347bdSJani Nikula 2464e52347bdSJani Nikula locktorture.shuffle_interval= [KNL] 2465e52347bdSJani Nikula Set task-shuffle interval (jiffies). Shuffling 2466e52347bdSJani Nikula tasks allows some CPUs to go into dyntick-idle 2467e52347bdSJani Nikula mode during the locktorture test. 2468e52347bdSJani Nikula 2469e52347bdSJani Nikula locktorture.shutdown_secs= [KNL] 2470e52347bdSJani Nikula Set time (s) after boot system shutdown. This 2471e52347bdSJani Nikula is useful for hands-off automated testing. 2472e52347bdSJani Nikula 2473e52347bdSJani Nikula locktorture.stat_interval= [KNL] 2474e52347bdSJani Nikula Time (s) between statistics printk()s. 2475e52347bdSJani Nikula 2476e52347bdSJani Nikula locktorture.stutter= [KNL] 2477e52347bdSJani Nikula Time (s) to stutter testing, for example, 2478e52347bdSJani Nikula specifying five seconds causes the test to run for 2479e52347bdSJani Nikula five seconds, wait for five seconds, and so on. 2480e52347bdSJani Nikula This tests the locking primitive's ability to 2481e52347bdSJani Nikula transition abruptly to and from idle. 2482e52347bdSJani Nikula 2483e52347bdSJani Nikula locktorture.torture_type= [KNL] 2484e52347bdSJani Nikula Specify the locking implementation to test. 2485e52347bdSJani Nikula 2486e52347bdSJani Nikula locktorture.verbose= [KNL] 2487e52347bdSJani Nikula Enable additional printk() statements. 2488e52347bdSJani Nikula 2489e52347bdSJani Nikula logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 2490e52347bdSJani Nikula Format: <irq> 2491e52347bdSJani Nikula 2492e52347bdSJani Nikula loglevel= All Kernel Messages with a loglevel smaller than the 2493e52347bdSJani Nikula console loglevel will be printed to the console. It can 2494e52347bdSJani Nikula also be changed with klogd or other programs. The 2495e52347bdSJani Nikula loglevels are defined as follows: 2496e52347bdSJani Nikula 2497e52347bdSJani Nikula 0 (KERN_EMERG) system is unusable 2498e52347bdSJani Nikula 1 (KERN_ALERT) action must be taken immediately 2499e52347bdSJani Nikula 2 (KERN_CRIT) critical conditions 2500e52347bdSJani Nikula 3 (KERN_ERR) error conditions 2501e52347bdSJani Nikula 4 (KERN_WARNING) warning conditions 2502e52347bdSJani Nikula 5 (KERN_NOTICE) normal but significant condition 2503e52347bdSJani Nikula 6 (KERN_INFO) informational 2504e52347bdSJani Nikula 7 (KERN_DEBUG) debug-level messages 2505e52347bdSJani Nikula 2506e52347bdSJani Nikula log_buf_len=n[KMG] Sets the size of the printk ring buffer, 2507e52347bdSJani Nikula in bytes. n must be a power of two and greater 2508e52347bdSJani Nikula than the minimal size. The minimal size is defined 2509e52347bdSJani Nikula by LOG_BUF_SHIFT kernel config parameter. There is 2510e52347bdSJani Nikula also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter 2511e52347bdSJani Nikula that allows to increase the default size depending on 2512e52347bdSJani Nikula the number of CPUs. See init/Kconfig for more details. 2513e52347bdSJani Nikula 2514e52347bdSJani Nikula logo.nologo [FB] Disables display of the built-in Linux logo. 2515e52347bdSJani Nikula This may be used to provide more screen space for 2516e52347bdSJani Nikula kernel log messages and is useful when debugging 2517e52347bdSJani Nikula kernel boot problems. 2518e52347bdSJani Nikula 2519e52347bdSJani Nikula lp=0 [LP] Specify parallel ports to use, e.g, 2520e52347bdSJani Nikula lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 2521e52347bdSJani Nikula lp=reset first parallel port). 'lp=0' disables the 2522e52347bdSJani Nikula lp=auto printer driver. 'lp=reset' (which can be 2523e52347bdSJani Nikula specified in addition to the ports) causes 2524e52347bdSJani Nikula attached printers to be reset. Using 2525e52347bdSJani Nikula lp=port1,port2,... specifies the parallel ports 2526e52347bdSJani Nikula to associate lp devices with, starting with 2527e52347bdSJani Nikula lp0. A port specification may be 'none' to skip 2528e52347bdSJani Nikula that lp device, or a parport name such as 2529e52347bdSJani Nikula 'parport0'. Specifying 'lp=auto' instead of a 2530e52347bdSJani Nikula port specification list means that device IDs 2531e52347bdSJani Nikula from each port should be examined, to see if 2532e52347bdSJani Nikula an IEEE 1284-compliant printer is attached; if 2533e52347bdSJani Nikula so, the driver will manage that printer. 2534e52347bdSJani Nikula See also header of drivers/char/lp.c. 2535e52347bdSJani Nikula 2536e52347bdSJani Nikula lpj=n [KNL] 2537e52347bdSJani Nikula Sets loops_per_jiffy to given constant, thus avoiding 2538e52347bdSJani Nikula time-consuming boot-time autodetection (up to 250 ms per 2539e52347bdSJani Nikula CPU). 0 enables autodetection (default). To determine 2540e52347bdSJani Nikula the correct value for your kernel, boot with normal 2541e52347bdSJani Nikula autodetection and see what value is printed. Note that 2542e52347bdSJani Nikula on SMP systems the preset will be applied to all CPUs, 2543e52347bdSJani Nikula which is likely to cause problems if your CPUs need 2544e52347bdSJani Nikula significantly divergent settings. An incorrect value 2545e52347bdSJani Nikula will cause delays in the kernel to be wrong, leading to 2546e52347bdSJani Nikula unpredictable I/O errors and other breakage. Although 2547e52347bdSJani Nikula unlikely, in the extreme case this might damage your 2548e52347bdSJani Nikula hardware. 2549e52347bdSJani Nikula 2550e52347bdSJani Nikula ltpc= [NET] 2551e52347bdSJani Nikula Format: <io>,<irq>,<dma> 2552e52347bdSJani Nikula 25539b8c7c14SKees Cook lsm.debug [SECURITY] Enable LSM initialization debugging output. 25549b8c7c14SKees Cook 255579f7865dSKees Cook lsm=lsm1,...,lsmN 255679f7865dSKees Cook [SECURITY] Choose order of LSM initialization. This 255789a9684eSKees Cook overrides CONFIG_LSM, and the "security=" parameter. 255879f7865dSKees Cook 2559e52347bdSJani Nikula machvec= [IA-64] Force the use of a particular machine-vector 2560e52347bdSJani Nikula (machvec) in a generic kernel. 2561df43acacSChristoph Hellwig Example: machvec=hpzx1 2562e52347bdSJani Nikula 2563e52347bdSJani Nikula machtype= [Loongson] Share the same kernel image file between different 2564e52347bdSJani Nikula yeeloong laptop. 2565e52347bdSJani Nikula Example: machtype=lemote-yeeloong-2f-7inch 2566e52347bdSJani Nikula 2567e52347bdSJani Nikula max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater 2568e52347bdSJani Nikula than or equal to this physical address is ignored. 2569e52347bdSJani Nikula 2570e52347bdSJani Nikula maxcpus= [SMP] Maximum number of processors that an SMP kernel 2571e52347bdSJani Nikula will bring up during bootup. maxcpus=n : n >= 0 limits 2572e52347bdSJani Nikula the kernel to bring up 'n' processors. Surely after 2573e52347bdSJani Nikula bootup you can bring up the other plugged cpu by executing 2574e52347bdSJani Nikula "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus 2575e52347bdSJani Nikula only takes effect during system bootup. 2576e52347bdSJani Nikula While n=0 is a special case, it is equivalent to "nosmp", 2577e52347bdSJani Nikula which also disables the IO APIC. 2578e52347bdSJani Nikula 2579e52347bdSJani Nikula max_loop= [LOOP] The number of loop block devices that get 2580e52347bdSJani Nikula (loop.max_loop) unconditionally pre-created at init time. The default 2581e52347bdSJani Nikula number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead 2582e52347bdSJani Nikula of statically allocating a predefined number, loop 2583e52347bdSJani Nikula devices can be requested on-demand with the 2584e52347bdSJani Nikula /dev/loop-control interface. 2585e52347bdSJani Nikula 2586e52347bdSJani Nikula mce [X86-32] Machine Check Exception 2587e52347bdSJani Nikula 2588cb1aaebeSMauro Carvalho Chehab mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst 2589e52347bdSJani Nikula 2590e52347bdSJani Nikula md= [HW] RAID subsystems devices and level 2591e52347bdSJani Nikula See Documentation/admin-guide/md.rst. 2592e52347bdSJani Nikula 2593e52347bdSJani Nikula mdacon= [MDA] 2594e52347bdSJani Nikula Format: <first>,<last> 2595e52347bdSJani Nikula Specifies range of consoles to be captured by the MDA. 2596e52347bdSJani Nikula 2597bc124170SThomas Gleixner mds= [X86,INTEL] 2598bc124170SThomas Gleixner Control mitigation for the Micro-architectural Data 2599bc124170SThomas Gleixner Sampling (MDS) vulnerability. 2600bc124170SThomas Gleixner 2601bc124170SThomas Gleixner Certain CPUs are vulnerable to an exploit against CPU 2602bc124170SThomas Gleixner internal buffers which can forward information to a 2603bc124170SThomas Gleixner disclosure gadget under certain conditions. 2604bc124170SThomas Gleixner 2605bc124170SThomas Gleixner In vulnerable processors, the speculatively 2606bc124170SThomas Gleixner forwarded data can be used in a cache side channel 2607bc124170SThomas Gleixner attack, to access data to which the attacker does 2608bc124170SThomas Gleixner not have direct access. 2609bc124170SThomas Gleixner 2610bc124170SThomas Gleixner This parameter controls the MDS mitigation. The 2611bc124170SThomas Gleixner options are: 2612bc124170SThomas Gleixner 2613bc124170SThomas Gleixner full - Enable MDS mitigation on vulnerable CPUs 2614d71eb0ceSJosh Poimboeuf full,nosmt - Enable MDS mitigation and disable 2615d71eb0ceSJosh Poimboeuf SMT on vulnerable CPUs 2616bc124170SThomas Gleixner off - Unconditionally disable MDS mitigation 2617bc124170SThomas Gleixner 261864870ed1SWaiman Long On TAA-affected machines, mds=off can be prevented by 261964870ed1SWaiman Long an active TAA mitigation as both vulnerabilities are 262064870ed1SWaiman Long mitigated with the same mechanism so in order to disable 262164870ed1SWaiman Long this mitigation, you need to specify tsx_async_abort=off 262264870ed1SWaiman Long too. 262364870ed1SWaiman Long 2624bc124170SThomas Gleixner Not specifying this option is equivalent to 2625bc124170SThomas Gleixner mds=full. 2626bc124170SThomas Gleixner 26275999bbe7SThomas Gleixner For details see: Documentation/admin-guide/hw-vuln/mds.rst 26285999bbe7SThomas Gleixner 2629e52347bdSJani Nikula mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 2630f3cd4c86SBaoquan He Amount of memory to be used in cases as follows: 2631f3cd4c86SBaoquan He 2632f3cd4c86SBaoquan He 1 for test; 2633f3cd4c86SBaoquan He 2 when the kernel is not able to see the whole system memory; 2634f3cd4c86SBaoquan He 3 memory that lies after 'mem=' boundary is excluded from 2635f3cd4c86SBaoquan He the hypervisor, then assigned to KVM guests. 2636f3cd4c86SBaoquan He 2637e52347bdSJani Nikula [X86] Work as limiting max address. Use together 2638e52347bdSJani Nikula with memmap= to avoid physical address space collisions. 2639e52347bdSJani Nikula Without memmap= PCI devices could be placed at addresses 2640e52347bdSJani Nikula belonging to unused RAM. 2641e52347bdSJani Nikula 2642f3cd4c86SBaoquan He Note that this only takes effects during boot time since 2643f3cd4c86SBaoquan He in above case 3, memory may need be hot added after boot 2644f3cd4c86SBaoquan He if system memory of hypervisor is not sufficient. 2645f3cd4c86SBaoquan He 2646e52347bdSJani Nikula mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 2647e52347bdSJani Nikula memory. 2648e52347bdSJani Nikula 2649e52347bdSJani Nikula memchunk=nn[KMG] 2650e52347bdSJani Nikula [KNL,SH] Allow user to override the default size for 2651e52347bdSJani Nikula per-device physically contiguous DMA buffers. 2652e52347bdSJani Nikula 2653e52347bdSJani Nikula memhp_default_state=online/offline 2654e52347bdSJani Nikula [KNL] Set the initial state for the memory hotplug 2655e52347bdSJani Nikula onlining policy. If not specified, the default value is 2656e52347bdSJani Nikula set according to the 2657e52347bdSJani Nikula CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config 2658e52347bdSJani Nikula option. 2659cb1aaebeSMauro Carvalho Chehab See Documentation/admin-guide/mm/memory-hotplug.rst. 2660e52347bdSJani Nikula 2661e52347bdSJani Nikula memmap=exactmap [KNL,X86] Enable setting of an exact 2662e52347bdSJani Nikula E820 memory map, as specified by the user. 2663e52347bdSJani Nikula Such memmap=exactmap lines can be constructed based on 2664e52347bdSJani Nikula BIOS output or other requirements. See the memmap=nn@ss 2665e52347bdSJani Nikula option description. 2666e52347bdSJani Nikula 2667e52347bdSJani Nikula memmap=nn[KMG]@ss[KMG] 2668e52347bdSJani Nikula [KNL] Force usage of a specific region of memory. 2669e52347bdSJani Nikula Region of memory to be used is from ss to ss+nn. 26708fcc9bc3SBaoquan He If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG], 26718fcc9bc3SBaoquan He which limits max address to nn[KMG]. 26728fcc9bc3SBaoquan He Multiple different regions can be specified, 26738fcc9bc3SBaoquan He comma delimited. 26748fcc9bc3SBaoquan He Example: 26758fcc9bc3SBaoquan He memmap=100M@2G,100M#3G,1G!1024G 2676e52347bdSJani Nikula 2677e52347bdSJani Nikula memmap=nn[KMG]#ss[KMG] 2678e52347bdSJani Nikula [KNL,ACPI] Mark specific memory as ACPI data. 2679e52347bdSJani Nikula Region of memory to be marked is from ss to ss+nn. 2680e52347bdSJani Nikula 2681e52347bdSJani Nikula memmap=nn[KMG]$ss[KMG] 2682e52347bdSJani Nikula [KNL,ACPI] Mark specific memory as reserved. 2683e52347bdSJani Nikula Region of memory to be reserved is from ss to ss+nn. 2684e52347bdSJani Nikula Example: Exclude memory from 0x18690000-0x1869ffff 2685e52347bdSJani Nikula memmap=64K$0x18690000 2686e52347bdSJani Nikula or 2687e52347bdSJani Nikula memmap=0x10000$0x18690000 26888fcc9bc3SBaoquan He Some bootloaders may need an escape character before '$', 26898fcc9bc3SBaoquan He like Grub2, otherwise '$' and the following number 26908fcc9bc3SBaoquan He will be eaten. 2691e52347bdSJani Nikula 2692e52347bdSJani Nikula memmap=nn[KMG]!ss[KMG] 2693e52347bdSJani Nikula [KNL,X86] Mark specific memory as protected. 2694e52347bdSJani Nikula Region of memory to be used, from ss to ss+nn. 2695e52347bdSJani Nikula The memory region may be marked as e820 type 12 (0xc) 2696e52347bdSJani Nikula and is NVDIMM or ADR memory. 2697e52347bdSJani Nikula 2698ef61f8a3SJan H. Schönherr memmap=<size>%<offset>-<oldtype>+<newtype> 2699ef61f8a3SJan H. Schönherr [KNL,ACPI] Convert memory within the specified region 2700ef61f8a3SJan H. Schönherr from <oldtype> to <newtype>. If "-<oldtype>" is left 2701ef61f8a3SJan H. Schönherr out, the whole region will be marked as <newtype>, 2702ef61f8a3SJan H. Schönherr even if previously unavailable. If "+<newtype>" is left 2703ef61f8a3SJan H. Schönherr out, matching memory will be removed. Types are 2704ef61f8a3SJan H. Schönherr specified as e820 types, e.g., 1 = RAM, 2 = reserved, 2705ef61f8a3SJan H. Schönherr 3 = ACPI, 12 = PRAM. 2706ef61f8a3SJan H. Schönherr 2707e52347bdSJani Nikula memory_corruption_check=0/1 [X86] 2708e52347bdSJani Nikula Some BIOSes seem to corrupt the first 64k of 2709e52347bdSJani Nikula memory when doing things like suspend/resume. 2710e52347bdSJani Nikula Setting this option will scan the memory 2711e52347bdSJani Nikula looking for corruption. Enabling this will 2712e52347bdSJani Nikula both detect corruption and prevent the kernel 2713e52347bdSJani Nikula from using the memory being corrupted. 2714e52347bdSJani Nikula However, its intended as a diagnostic tool; if 2715e52347bdSJani Nikula repeatable BIOS-originated corruption always 2716e52347bdSJani Nikula affects the same memory, you can use memmap= 2717e52347bdSJani Nikula to prevent the kernel from using that memory. 2718e52347bdSJani Nikula 2719e52347bdSJani Nikula memory_corruption_check_size=size [X86] 2720e52347bdSJani Nikula By default it checks for corruption in the low 2721e52347bdSJani Nikula 64k, making this memory unavailable for normal 2722e52347bdSJani Nikula use. Use this parameter to scan for 2723e52347bdSJani Nikula corruption in more or less memory. 2724e52347bdSJani Nikula 2725e52347bdSJani Nikula memory_corruption_check_period=seconds [X86] 2726e52347bdSJani Nikula By default it checks for corruption every 60 2727e52347bdSJani Nikula seconds. Use this parameter to check at some 2728e52347bdSJani Nikula other rate. 0 disables periodic checking. 2729e52347bdSJani Nikula 2730d90fe2acSChristophe Leroy memtest= [KNL,X86,ARM,PPC] Enable memtest 2731e52347bdSJani Nikula Format: <integer> 2732e52347bdSJani Nikula default : 0 <disable> 2733e52347bdSJani Nikula Specifies the number of memtest passes to be 2734e52347bdSJani Nikula performed. Each pass selects another test 2735e52347bdSJani Nikula pattern from a given set of patterns. Memtest 2736e52347bdSJani Nikula fills the memory with this pattern, validates 2737e52347bdSJani Nikula memory contents and reserves bad memory 2738e52347bdSJani Nikula regions that are detected. 2739e52347bdSJani Nikula 2740c262f3b9STom Lendacky mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control 2741c262f3b9STom Lendacky Valid arguments: on, off 2742c262f3b9STom Lendacky Default (depends on kernel configuration option): 2743c262f3b9STom Lendacky on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y) 2744c262f3b9STom Lendacky off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n) 2745c262f3b9STom Lendacky mem_encrypt=on: Activate SME 2746c262f3b9STom Lendacky mem_encrypt=off: Do not activate SME 2747c262f3b9STom Lendacky 27482f5947dfSChristoph Hellwig Refer to Documentation/virt/kvm/amd-memory-encryption.rst 2749c262f3b9STom Lendacky for details on when memory encryption can be activated. 2750c262f3b9STom Lendacky 27517b9dc3f7SLinus Torvalds mem_sleep_default= [SUSPEND] Default system suspend mode: 27527b9dc3f7SLinus Torvalds s2idle - Suspend-To-Idle 27537b9dc3f7SLinus Torvalds shallow - Power-On Suspend or equivalent (if supported) 27547b9dc3f7SLinus Torvalds deep - Suspend-To-RAM or equivalent (if supported) 275558e7cb9eSRafael J. Wysocki See Documentation/admin-guide/pm/sleep-states.rst. 27567b9dc3f7SLinus Torvalds 2757e52347bdSJani Nikula meye.*= [HW] Set MotionEye Camera parameters 275832e2eae2SMauro Carvalho Chehab See Documentation/admin-guide/media/meye.rst. 2759e52347bdSJani Nikula 2760e52347bdSJani Nikula mfgpt_irq= [IA-32] Specify the IRQ to use for the 2761e52347bdSJani Nikula Multi-Function General Purpose Timers on AMD Geode 2762e52347bdSJani Nikula platforms. 2763e52347bdSJani Nikula 2764e52347bdSJani Nikula mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 2765e52347bdSJani Nikula the BIOS has incorrectly applied a workaround. TinyBIOS 2766e52347bdSJani Nikula version 0.98 is known to be affected, 0.99 fixes the 2767e52347bdSJani Nikula problem by letting the user disable the workaround. 2768e52347bdSJani Nikula 2769e52347bdSJani Nikula mga= [HW,DRM] 2770e52347bdSJani Nikula 2771e52347bdSJani Nikula min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this 2772e52347bdSJani Nikula physical address is ignored. 2773e52347bdSJani Nikula 2774e52347bdSJani Nikula mini2440= [ARM,HW,KNL] 2775e52347bdSJani Nikula Format:[0..2][b][c][t] 2776e52347bdSJani Nikula Default: "0tb" 2777e52347bdSJani Nikula MINI2440 configuration specification: 2778e52347bdSJani Nikula 0 - The attached screen is the 3.5" TFT 2779e52347bdSJani Nikula 1 - The attached screen is the 7" TFT 2780e52347bdSJani Nikula 2 - The VGA Shield is attached (1024x768) 2781e52347bdSJani Nikula Leaving out the screen size parameter will not load 2782e52347bdSJani Nikula the TFT driver, and the framebuffer will be left 2783e52347bdSJani Nikula unconfigured. 2784e52347bdSJani Nikula b - Enable backlight. The TFT backlight pin will be 2785e52347bdSJani Nikula linked to the kernel VESA blanking code and a GPIO 2786e52347bdSJani Nikula LED. This parameter is not necessary when using the 2787e52347bdSJani Nikula VGA shield. 2788e52347bdSJani Nikula c - Enable the s3c camera interface. 2789e52347bdSJani Nikula t - Reserved for enabling touchscreen support. The 2790e52347bdSJani Nikula touchscreen support is not enabled in the mainstream 2791e52347bdSJani Nikula kernel as of 2.6.30, a preliminary port can be found 2792e52347bdSJani Nikula in the "bleeding edge" mini2440 support kernel at 2793e52347bdSJani Nikula http://repo.or.cz/w/linux-2.6/mini2440.git 2794e52347bdSJani Nikula 279598af8452SJosh Poimboeuf mitigations= 2796a111b7c0SJosh Poimboeuf [X86,PPC,S390,ARM64] Control optional mitigations for 2797a111b7c0SJosh Poimboeuf CPU vulnerabilities. This is a set of curated, 2798d68be4c4SJosh Poimboeuf arch-independent options, each of which is an 2799d68be4c4SJosh Poimboeuf aggregation of existing arch-specific options. 280098af8452SJosh Poimboeuf 280198af8452SJosh Poimboeuf off 280298af8452SJosh Poimboeuf Disable all optional CPU mitigations. This 280398af8452SJosh Poimboeuf improves system performance, but it may also 280498af8452SJosh Poimboeuf expose users to several CPU vulnerabilities. 2805782e69efSJosh Poimboeuf Equivalent to: nopti [X86,PPC] 2806a111b7c0SJosh Poimboeuf kpti=0 [ARM64] 2807a2059825SJosh Poimboeuf nospectre_v1 [X86,PPC] 28080336e04aSJosh Poimboeuf nobp=0 [S390] 2809a111b7c0SJosh Poimboeuf nospectre_v2 [X86,PPC,S390,ARM64] 2810d68be4c4SJosh Poimboeuf spectre_v2_user=off [X86] 2811782e69efSJosh Poimboeuf spec_store_bypass_disable=off [X86,PPC] 2812a111b7c0SJosh Poimboeuf ssbd=force-off [ARM64] 2813d68be4c4SJosh Poimboeuf l1tf=off [X86] 28145c14068fSJosh Poimboeuf mds=off [X86] 2815a7a248c5SPawan Gupta tsx_async_abort=off [X86] 2816b8e8c830SPaolo Bonzini kvm.nx_huge_pages=off [X86] 2817b8e8c830SPaolo Bonzini 2818b8e8c830SPaolo Bonzini Exceptions: 2819b8e8c830SPaolo Bonzini This does not have any effect on 2820b8e8c830SPaolo Bonzini kvm.nx_huge_pages when 2821b8e8c830SPaolo Bonzini kvm.nx_huge_pages=force. 282298af8452SJosh Poimboeuf 282398af8452SJosh Poimboeuf auto (default) 282498af8452SJosh Poimboeuf Mitigate all CPU vulnerabilities, but leave SMT 282598af8452SJosh Poimboeuf enabled, even if it's vulnerable. This is for 282698af8452SJosh Poimboeuf users who don't want to be surprised by SMT 282798af8452SJosh Poimboeuf getting disabled across kernel upgrades, or who 282898af8452SJosh Poimboeuf have other ways of avoiding SMT-based attacks. 2829d68be4c4SJosh Poimboeuf Equivalent to: (default behavior) 283098af8452SJosh Poimboeuf 283198af8452SJosh Poimboeuf auto,nosmt 283298af8452SJosh Poimboeuf Mitigate all CPU vulnerabilities, disabling SMT 283398af8452SJosh Poimboeuf if needed. This is for users who always want to 283498af8452SJosh Poimboeuf be fully mitigated, even if it means losing SMT. 2835d68be4c4SJosh Poimboeuf Equivalent to: l1tf=flush,nosmt [X86] 28365c14068fSJosh Poimboeuf mds=full,nosmt [X86] 2837a7a248c5SPawan Gupta tsx_async_abort=full,nosmt [X86] 283898af8452SJosh Poimboeuf 2839e52347bdSJani Nikula mminit_loglevel= 2840e52347bdSJani Nikula [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 2841e52347bdSJani Nikula parameter allows control of the logging verbosity for 2842e52347bdSJani Nikula the additional memory initialisation checks. A value 2843e52347bdSJani Nikula of 0 disables mminit logging and a level of 4 will 2844e52347bdSJani Nikula log everything. Information is printed at KERN_DEBUG 2845e52347bdSJani Nikula so loglevel=8 may also need to be specified. 2846e52347bdSJani Nikula 2847e52347bdSJani Nikula module.sig_enforce 2848e52347bdSJani Nikula [KNL] When CONFIG_MODULE_SIG is set, this means that 2849e52347bdSJani Nikula modules without (valid) signatures will fail to load. 2850e52347bdSJani Nikula Note that if CONFIG_MODULE_SIG_FORCE is set, that 2851e52347bdSJani Nikula is always true, so this option does nothing. 2852e52347bdSJani Nikula 2853e52347bdSJani Nikula module_blacklist= [KNL] Do not load a comma-separated list of 2854e52347bdSJani Nikula modules. Useful for debugging problem modules. 2855e52347bdSJani Nikula 2856e52347bdSJani Nikula mousedev.tap_time= 2857e52347bdSJani Nikula [MOUSE] Maximum time between finger touching and 2858e52347bdSJani Nikula leaving touchpad surface for touch to be considered 2859e52347bdSJani Nikula a tap and be reported as a left button click (for 2860e52347bdSJani Nikula touchpads working in absolute mode only). 2861e52347bdSJani Nikula Format: <msecs> 2862e52347bdSJani Nikula mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 2863e52347bdSJani Nikula reporting absolute coordinates, such as tablets 2864e52347bdSJani Nikula mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 2865e52347bdSJani Nikula reporting absolute coordinates, such as tablets 2866e52347bdSJani Nikula 2867a5c6d650SDavid Rientjes movablecore= [KNL,X86,IA-64,PPC] 2868a5c6d650SDavid Rientjes Format: nn[KMGTPE] | nn% 2869a5c6d650SDavid Rientjes This parameter is the complement to kernelcore=, it 2870a5c6d650SDavid Rientjes specifies the amount of memory used for migratable 2871a5c6d650SDavid Rientjes allocations. If both kernelcore and movablecore is 2872a5c6d650SDavid Rientjes specified, then kernelcore will be at *least* the 2873a5c6d650SDavid Rientjes specified value but may be more. If movablecore on its 2874a5c6d650SDavid Rientjes own is specified, the administrator must be careful 2875e52347bdSJani Nikula that the amount of memory usable for all allocations 2876e52347bdSJani Nikula is not too small. 2877e52347bdSJani Nikula 2878f70029bbSMichal Hocko movable_node [KNL] Boot-time switch to make hotplugable memory 2879f70029bbSMichal Hocko NUMA nodes to be movable. This means that the memory 2880f70029bbSMichal Hocko of such nodes will be usable only for movable 2881f70029bbSMichal Hocko allocations which rules out almost all kernel 2882f70029bbSMichal Hocko allocations. Use with caution! 2883e52347bdSJani Nikula 2884e52347bdSJani Nikula MTD_Partition= [MTD] 2885e52347bdSJani Nikula Format: <name>,<region-number>,<size>,<offset> 2886e52347bdSJani Nikula 2887e52347bdSJani Nikula MTD_Region= [MTD] Format: 2888e52347bdSJani Nikula <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 2889e52347bdSJani Nikula 2890e52347bdSJani Nikula mtdparts= [MTD] 2891fb251124SJonathan Neuschäfer See drivers/mtd/parsers/cmdlinepart.c 2892e52347bdSJani Nikula 2893e52347bdSJani Nikula multitce=off [PPC] This parameter disables the use of the pSeries 2894e52347bdSJani Nikula firmware feature for updating multiple TCE entries 2895e52347bdSJani Nikula at a time. 2896e52347bdSJani Nikula 2897e52347bdSJani Nikula onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration 2898e52347bdSJani Nikula 2899e52347bdSJani Nikula Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] 2900e52347bdSJani Nikula 2901e52347bdSJani Nikula boundary - index of last SLC block on Flex-OneNAND. 2902e52347bdSJani Nikula The remaining blocks are configured as MLC blocks. 2903e52347bdSJani Nikula lock - Configure if Flex-OneNAND boundary should be locked. 2904e52347bdSJani Nikula Once locked, the boundary cannot be changed. 2905e52347bdSJani Nikula 1 indicates lock status, 0 indicates unlock status. 2906e52347bdSJani Nikula 2907e52347bdSJani Nikula mtdset= [ARM] 2908e52347bdSJani Nikula ARM/S3C2412 JIVE boot control 2909e52347bdSJani Nikula 2910e52347bdSJani Nikula See arch/arm/mach-s3c2412/mach-jive.c 2911e52347bdSJani Nikula 2912e52347bdSJani Nikula mtouchusb.raw_coordinates= 2913e52347bdSJani Nikula [HW] Make the MicroTouch USB driver use raw coordinates 2914e52347bdSJani Nikula ('y', default) or cooked coordinates ('n') 2915e52347bdSJani Nikula 2916e52347bdSJani Nikula mtrr_chunk_size=nn[KMG] [X86] 2917e52347bdSJani Nikula used for mtrr cleanup. It is largest continuous chunk 2918e52347bdSJani Nikula that could hold holes aka. UC entries. 2919e52347bdSJani Nikula 2920e52347bdSJani Nikula mtrr_gran_size=nn[KMG] [X86] 2921e52347bdSJani Nikula Used for mtrr cleanup. It is granularity of mtrr block. 2922e52347bdSJani Nikula Default is 1. 2923e52347bdSJani Nikula Large value could prevent small alignment from 2924e52347bdSJani Nikula using up MTRRs. 2925e52347bdSJani Nikula 2926e52347bdSJani Nikula mtrr_spare_reg_nr=n [X86] 2927e52347bdSJani Nikula Format: <integer> 2928e52347bdSJani Nikula Range: 0,7 : spare reg number 2929e52347bdSJani Nikula Default : 1 2930e52347bdSJani Nikula Used for mtrr cleanup. It is spare mtrr entries number. 2931e52347bdSJani Nikula Set to 2 or more if your graphical card needs more. 2932e52347bdSJani Nikula 2933e52347bdSJani Nikula n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 2934e52347bdSJani Nikula 2935e52347bdSJani Nikula netdev= [NET] Network devices parameters 2936e52347bdSJani Nikula Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 2937e52347bdSJani Nikula Note that mem_start is often overloaded to mean 2938e52347bdSJani Nikula something different and driver-specific. 2939e52347bdSJani Nikula This usage is only documented in each driver source 2940e52347bdSJani Nikula file if at all. 2941e52347bdSJani Nikula 2942e52347bdSJani Nikula nf_conntrack.acct= 2943e52347bdSJani Nikula [NETFILTER] Enable connection tracking flow accounting 2944e52347bdSJani Nikula 0 to disable accounting 2945e52347bdSJani Nikula 1 to enable accounting 2946e52347bdSJani Nikula Default value is 0. 2947e52347bdSJani Nikula 2948e52347bdSJani Nikula nfsaddrs= [NFS] Deprecated. Use ip= instead. 29493eb30c51SNiklas Söderlund See Documentation/admin-guide/nfs/nfsroot.rst. 2950e52347bdSJani Nikula 2951e52347bdSJani Nikula nfsroot= [NFS] nfs root filesystem for disk-less boxes. 29523eb30c51SNiklas Söderlund See Documentation/admin-guide/nfs/nfsroot.rst. 2953e52347bdSJani Nikula 2954e52347bdSJani Nikula nfsrootdebug [NFS] enable nfsroot debugging messages. 29553eb30c51SNiklas Söderlund See Documentation/admin-guide/nfs/nfsroot.rst. 2956e52347bdSJani Nikula 2957e52347bdSJani Nikula nfs.callback_nr_threads= 2958e52347bdSJani Nikula [NFSv4] set the total number of threads that the 2959e52347bdSJani Nikula NFS client will assign to service NFSv4 callback 2960e52347bdSJani Nikula requests. 2961e52347bdSJani Nikula 2962e52347bdSJani Nikula nfs.callback_tcpport= 2963e52347bdSJani Nikula [NFS] set the TCP port on which the NFSv4 callback 2964e52347bdSJani Nikula channel should listen. 2965e52347bdSJani Nikula 2966e52347bdSJani Nikula nfs.cache_getent= 2967e52347bdSJani Nikula [NFS] sets the pathname to the program which is used 2968e52347bdSJani Nikula to update the NFS client cache entries. 2969e52347bdSJani Nikula 2970e52347bdSJani Nikula nfs.cache_getent_timeout= 2971e52347bdSJani Nikula [NFS] sets the timeout after which an attempt to 2972e52347bdSJani Nikula update a cache entry is deemed to have failed. 2973e52347bdSJani Nikula 2974e52347bdSJani Nikula nfs.idmap_cache_timeout= 2975e52347bdSJani Nikula [NFS] set the maximum lifetime for idmapper cache 2976e52347bdSJani Nikula entries. 2977e52347bdSJani Nikula 2978e52347bdSJani Nikula nfs.enable_ino64= 2979e52347bdSJani Nikula [NFS] enable 64-bit inode numbers. 2980e52347bdSJani Nikula If zero, the NFS client will fake up a 32-bit inode 2981e52347bdSJani Nikula number for the readdir() and stat() syscalls instead 2982e52347bdSJani Nikula of returning the full 64-bit number. 2983e52347bdSJani Nikula The default is to return 64-bit inode numbers. 2984e52347bdSJani Nikula 2985e52347bdSJani Nikula nfs.max_session_cb_slots= 2986e52347bdSJani Nikula [NFSv4.1] Sets the maximum number of session 2987e52347bdSJani Nikula slots the client will assign to the callback 2988e52347bdSJani Nikula channel. This determines the maximum number of 2989e52347bdSJani Nikula callbacks the client will process in parallel for 2990e52347bdSJani Nikula a particular server. 2991e52347bdSJani Nikula 2992e52347bdSJani Nikula nfs.max_session_slots= 2993e52347bdSJani Nikula [NFSv4.1] Sets the maximum number of session slots 2994e52347bdSJani Nikula the client will attempt to negotiate with the server. 2995e52347bdSJani Nikula This limits the number of simultaneous RPC requests 2996e52347bdSJani Nikula that the client can send to the NFSv4.1 server. 2997e52347bdSJani Nikula Note that there is little point in setting this 2998e52347bdSJani Nikula value higher than the max_tcp_slot_table_limit. 2999e52347bdSJani Nikula 3000e52347bdSJani Nikula nfs.nfs4_disable_idmapping= 3001e52347bdSJani Nikula [NFSv4] When set to the default of '1', this option 3002e52347bdSJani Nikula ensures that both the RPC level authentication 3003e52347bdSJani Nikula scheme and the NFS level operations agree to use 3004e52347bdSJani Nikula numeric uids/gids if the mount is using the 3005e52347bdSJani Nikula 'sec=sys' security flavour. In effect it is 3006e52347bdSJani Nikula disabling idmapping, which can make migration from 3007e52347bdSJani Nikula legacy NFSv2/v3 systems to NFSv4 easier. 3008e52347bdSJani Nikula Servers that do not support this mode of operation 3009e52347bdSJani Nikula will be autodetected by the client, and it will fall 3010e52347bdSJani Nikula back to using the idmapper. 3011e52347bdSJani Nikula To turn off this behaviour, set the value to '0'. 3012e52347bdSJani Nikula nfs.nfs4_unique_id= 3013e52347bdSJani Nikula [NFS4] Specify an additional fixed unique ident- 3014e52347bdSJani Nikula ification string that NFSv4 clients can insert into 3015e52347bdSJani Nikula their nfs_client_id4 string. This is typically a 3016e52347bdSJani Nikula UUID that is generated at system install time. 3017e52347bdSJani Nikula 3018e52347bdSJani Nikula nfs.send_implementation_id = 3019e52347bdSJani Nikula [NFSv4.1] Send client implementation identification 3020e52347bdSJani Nikula information in exchange_id requests. 3021e52347bdSJani Nikula If zero, no implementation identification information 3022e52347bdSJani Nikula will be sent. 3023e52347bdSJani Nikula The default is to send the implementation identification 3024e52347bdSJani Nikula information. 3025e52347bdSJani Nikula 3026e52347bdSJani Nikula nfs.recover_lost_locks = 3027e52347bdSJani Nikula [NFSv4] Attempt to recover locks that were lost due 3028e52347bdSJani Nikula to a lease timeout on the server. Please note that 3029e52347bdSJani Nikula doing this risks data corruption, since there are 3030e52347bdSJani Nikula no guarantees that the file will remain unchanged 3031e52347bdSJani Nikula after the locks are lost. 3032e52347bdSJani Nikula If you want to enable the kernel legacy behaviour of 3033e52347bdSJani Nikula attempting to recover these locks, then set this 3034e52347bdSJani Nikula parameter to '1'. 3035e52347bdSJani Nikula The default parameter value of '0' causes the kernel 3036e52347bdSJani Nikula not to attempt recovery of lost locks. 3037e52347bdSJani Nikula 3038e52347bdSJani Nikula nfs4.layoutstats_timer = 3039e52347bdSJani Nikula [NFSv4.2] Change the rate at which the kernel sends 3040e52347bdSJani Nikula layoutstats to the pNFS metadata server. 3041e52347bdSJani Nikula 3042e52347bdSJani Nikula Setting this to value to 0 causes the kernel to use 3043e52347bdSJani Nikula whatever value is the default set by the layout 3044e52347bdSJani Nikula driver. A non-zero value sets the minimum interval 3045e52347bdSJani Nikula in seconds between layoutstats transmissions. 3046e52347bdSJani Nikula 3047e52347bdSJani Nikula nfsd.nfs4_disable_idmapping= 3048e52347bdSJani Nikula [NFSv4] When set to the default of '1', the NFSv4 3049e52347bdSJani Nikula server will return only numeric uids and gids to 3050e52347bdSJani Nikula clients using auth_sys, and will accept numeric uids 3051e52347bdSJani Nikula and gids from such clients. This is intended to ease 3052e52347bdSJani Nikula migration from NFSv2/v3. 3053e52347bdSJani Nikula 3054c0c74acbSHans-Christian Noren Egtvedt nmi_debug= [KNL,SH] Specify one or more actions to take 3055e52347bdSJani Nikula when a NMI is triggered. 3056e52347bdSJani Nikula Format: [state][,regs][,debounce][,die] 3057e52347bdSJani Nikula 3058e52347bdSJani Nikula nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels 3059e52347bdSJani Nikula Format: [panic,][nopanic,][num] 3060e52347bdSJani Nikula Valid num: 0 or 1 3061e52347bdSJani Nikula 0 - turn hardlockup detector in nmi_watchdog off 3062e52347bdSJani Nikula 1 - turn hardlockup detector in nmi_watchdog on 3063e52347bdSJani Nikula When panic is specified, panic when an NMI watchdog 306493285c01SZhenzhong Duan timeout occurs (or 'nopanic' to not panic on an NMI 306593285c01SZhenzhong Duan watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) 306693285c01SZhenzhong Duan To disable both hard and soft lockup detectors, 3067e52347bdSJani Nikula please see 'nowatchdog'. 3068e52347bdSJani Nikula This is useful when you use a panic=... timeout and 3069e52347bdSJani Nikula need the box quickly up again. 3070e52347bdSJani Nikula 3071d22881dcSScott Wood These settings can be accessed at runtime via 3072d22881dcSScott Wood the nmi_watchdog and hardlockup_panic sysctls. 3073d22881dcSScott Wood 3074e52347bdSJani Nikula netpoll.carrier_timeout= 3075e52347bdSJani Nikula [NET] Specifies amount of time (in seconds) that 3076e52347bdSJani Nikula netpoll should wait for a carrier. By default netpoll 3077e52347bdSJani Nikula waits 4 seconds. 3078e52347bdSJani Nikula 3079e52347bdSJani Nikula no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 3080e52347bdSJani Nikula emulation library even if a 387 maths coprocessor 3081e52347bdSJani Nikula is present. 3082e52347bdSJani Nikula 3083372fddf7SKirill A. Shutemov no5lvl [X86-64] Disable 5-level paging mode. Forces 3084372fddf7SKirill A. Shutemov kernel to use 4-level paging instead. 3085372fddf7SKirill A. Shutemov 3086e52347bdSJani Nikula no_console_suspend 3087e52347bdSJani Nikula [HW] Never suspend the console 3088e52347bdSJani Nikula Disable suspending of consoles during suspend and 3089e52347bdSJani Nikula hibernate operations. Once disabled, debugging 3090e52347bdSJani Nikula messages can reach various consoles while the rest 3091e52347bdSJani Nikula of the system is being put to sleep (ie, while 3092e52347bdSJani Nikula debugging driver suspend/resume hooks). This may 3093e52347bdSJani Nikula not work reliably with all consoles, but is known 3094e52347bdSJani Nikula to work with serial and VGA consoles. 3095e52347bdSJani Nikula To facilitate more flexible debugging, we also add 3096e52347bdSJani Nikula console_suspend, a printk module parameter to control 3097e52347bdSJani Nikula it. Users could use console_suspend (usually 3098e52347bdSJani Nikula /sys/module/printk/parameters/console_suspend) to 3099e52347bdSJani Nikula turn on/off it dynamically. 3100e52347bdSJani Nikula 3101c6c40533SKairui Song novmcoredd [KNL,KDUMP] 3102c6c40533SKairui Song Disable device dump. Device dump allows drivers to 3103c6c40533SKairui Song append dump data to vmcore so you can collect driver 3104c6c40533SKairui Song specified debug info. Drivers can append the data 3105c6c40533SKairui Song without any limit and this data is stored in memory, 3106c6c40533SKairui Song so this may cause significant memory stress. Disabling 3107c6c40533SKairui Song device dump can help save memory but the driver debug 3108c6c40533SKairui Song data will be no longer available. This parameter 3109c6c40533SKairui Song is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP 3110c6c40533SKairui Song is set. 3111c6c40533SKairui Song 3112e52347bdSJani Nikula noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 3113e52347bdSJani Nikula caches in the slab allocator. Saves per-node memory, 3114e52347bdSJani Nikula but will impact performance. 3115e52347bdSJani Nikula 3116e52347bdSJani Nikula noalign [KNL,ARM] 3117e52347bdSJani Nikula 3118686140a1SVasily Gorbik noaltinstr [S390] Disables alternative instructions patching 3119686140a1SVasily Gorbik (CPU alternatives feature). 3120686140a1SVasily Gorbik 3121e52347bdSJani Nikula noapic [SMP,APIC] Tells the kernel to not make use of any 3122e52347bdSJani Nikula IOAPICs that may be present in the system. 3123e52347bdSJani Nikula 3124e52347bdSJani Nikula noautogroup Disable scheduler automatic task group creation. 3125e52347bdSJani Nikula 3126e52347bdSJani Nikula nobats [PPC] Do not use BATs for mapping kernel lowmem 3127e52347bdSJani Nikula on "Classic" PPC cores. 3128e52347bdSJani Nikula 3129e52347bdSJani Nikula nocache [ARM] 3130e52347bdSJani Nikula 3131e52347bdSJani Nikula noclflush [BUGS=X86] Don't use the CLFLUSH instruction 3132e52347bdSJani Nikula 3133e52347bdSJani Nikula nodelayacct [KNL] Disable per-task delay accounting 3134e52347bdSJani Nikula 3135e52347bdSJani Nikula nodsp [SH] Disable hardware DSP at boot time. 3136e52347bdSJani Nikula 3137e52347bdSJani Nikula noefi Disable EFI runtime services support. 3138e52347bdSJani Nikula 3139e52347bdSJani Nikula noexec [IA-64] 3140e52347bdSJani Nikula 3141e52347bdSJani Nikula noexec [X86] 3142e52347bdSJani Nikula On X86-32 available only on PAE configured kernels. 3143e52347bdSJani Nikula noexec=on: enable non-executable mappings (default) 3144e52347bdSJani Nikula noexec=off: disable non-executable mappings 3145e52347bdSJani Nikula 3146de78a9c4SChristophe Leroy nosmap [X86,PPC] 3147e52347bdSJani Nikula Disable SMAP (Supervisor Mode Access Prevention) 3148e52347bdSJani Nikula even if it is supported by processor. 3149e52347bdSJani Nikula 31500fb1c25aSChristophe Leroy nosmep [X86,PPC] 3151e52347bdSJani Nikula Disable SMEP (Supervisor Mode Execution Prevention) 3152e52347bdSJani Nikula even if it is supported by processor. 3153e52347bdSJani Nikula 3154e52347bdSJani Nikula noexec32 [X86-64] 3155e52347bdSJani Nikula This affects only 32-bit executables. 3156e52347bdSJani Nikula noexec32=on: enable non-executable mappings (default) 3157e52347bdSJani Nikula read doesn't imply executable mappings 3158e52347bdSJani Nikula noexec32=off: disable non-executable mappings 3159e52347bdSJani Nikula read implies executable mappings 3160e52347bdSJani Nikula 3161e52347bdSJani Nikula nofpu [MIPS,SH] Disable hardware FPU at boot time. 3162e52347bdSJani Nikula 3163e52347bdSJani Nikula nofxsr [BUGS=X86-32] Disables x86 floating point extended 3164e52347bdSJani Nikula register save and restore. The kernel will only save 3165e52347bdSJani Nikula legacy floating-point registers on task switch. 3166e52347bdSJani Nikula 3167d909f910SNicholas Piggin nohugeiomap [KNL,x86,PPC] Disable kernel huge I/O mappings. 3168e52347bdSJani Nikula 3169e52347bdSJani Nikula nosmt [KNL,S390] Disable symmetric multithreading (SMT). 3170e52347bdSJani Nikula Equivalent to smt=1. 3171e52347bdSJani Nikula 317205736e4aSThomas Gleixner [KNL,x86] Disable symmetric multithreading (SMT). 3173506a66f3SThomas Gleixner nosmt=force: Force disable SMT, cannot be undone 3174506a66f3SThomas Gleixner via the sysfs control file. 317505736e4aSThomas Gleixner 3176a2059825SJosh Poimboeuf nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1 3177a2059825SJosh Poimboeuf (bounds check bypass). With this option data leaks are 3178a2059825SJosh Poimboeuf possible in the system. 317926cb1f36SDiana Craciun 3180e5ce5e72SJeremy Linton nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for 3181e5ce5e72SJeremy Linton the Spectre variant 2 (indirect branch prediction) 3182e5ce5e72SJeremy Linton vulnerability. System may allow data leaks with this 3183e5ce5e72SJeremy Linton option. 3184da285121SDavid Woodhouse 318524f7fc83SKonrad Rzeszutek Wilk nospec_store_bypass_disable 318624f7fc83SKonrad Rzeszutek Wilk [HW] Disable all mitigations for the Speculative Store Bypass vulnerability 318724f7fc83SKonrad Rzeszutek Wilk 3188e52347bdSJani Nikula noxsave [BUGS=X86] Disables x86 extended register state save 3189e52347bdSJani Nikula and restore using xsave. The kernel will fallback to 3190e52347bdSJani Nikula enabling legacy floating-point and sse state. 3191e52347bdSJani Nikula 3192e52347bdSJani Nikula noxsaveopt [X86] Disables xsaveopt used in saving x86 extended 3193e52347bdSJani Nikula register states. The kernel will fall back to use 3194e52347bdSJani Nikula xsave to save the states. By using this parameter, 3195e52347bdSJani Nikula performance of saving the states is degraded because 3196e52347bdSJani Nikula xsave doesn't support modified optimization while 3197e52347bdSJani Nikula xsaveopt supports it on xsaveopt enabled systems. 3198e52347bdSJani Nikula 3199e52347bdSJani Nikula noxsaves [X86] Disables xsaves and xrstors used in saving and 3200e52347bdSJani Nikula restoring x86 extended register state in compacted 3201e52347bdSJani Nikula form of xsave area. The kernel will fall back to use 3202e52347bdSJani Nikula xsaveopt and xrstor to save and restore the states 3203e52347bdSJani Nikula in standard form of xsave area. By using this 3204e52347bdSJani Nikula parameter, xsave area per process might occupy more 3205e52347bdSJani Nikula memory on xsaves enabled systems. 3206e52347bdSJani Nikula 3207e52347bdSJani Nikula nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or 3208e52347bdSJani Nikula wfi(ARM) instruction doesn't work correctly and not to 3209e52347bdSJani Nikula use it. This is also useful when using JTAG debugger. 3210e52347bdSJani Nikula 3211e52347bdSJani Nikula no_file_caps Tells the kernel not to honor file capabilities. The 3212e52347bdSJani Nikula only way then for a file to be executed with privilege 3213e52347bdSJani Nikula is to be setuid root or executed by root. 3214e52347bdSJani Nikula 3215e52347bdSJani Nikula nohalt [IA-64] Tells the kernel not to use the power saving 3216e52347bdSJani Nikula function PAL_HALT_LIGHT when idle. This increases 3217e52347bdSJani Nikula power-consumption. On the positive side, it reduces 3218e52347bdSJani Nikula interrupt wake-up latency, which may improve performance 3219e52347bdSJani Nikula in certain environments such as networked servers or 3220e52347bdSJani Nikula real-time systems. 3221e52347bdSJani Nikula 3222e52347bdSJani Nikula nohibernate [HIBERNATION] Disable hibernation and resume. 3223e52347bdSJani Nikula 3224e52347bdSJani Nikula nohz= [KNL] Boottime enable/disable dynamic ticks 3225e52347bdSJani Nikula Valid arguments: on, off 3226e52347bdSJani Nikula Default: on 3227e52347bdSJani Nikula 3228d94d1053SFrederic Weisbecker nohz_full= [KNL,BOOT,SMP,ISOL] 3229e52347bdSJani Nikula The argument is a cpu list, as described above. 3230e52347bdSJani Nikula In kernels built with CONFIG_NO_HZ_FULL=y, set 3231e52347bdSJani Nikula the specified list of CPUs whose tick will be stopped 3232e52347bdSJani Nikula whenever possible. The boot CPU will be forced outside 3233f99bcb2cSPaul E. McKenney the range to maintain the timekeeping. Any CPUs 3234f99bcb2cSPaul E. McKenney in this list will have their RCU callbacks offloaded, 3235f99bcb2cSPaul E. McKenney just as if they had also been called out in the 3236f99bcb2cSPaul E. McKenney rcu_nocbs= boot parameter. 3237e52347bdSJani Nikula 3238e52347bdSJani Nikula noiotrap [SH] Disables trapped I/O port accesses. 3239e52347bdSJani Nikula 3240e52347bdSJani Nikula noirqdebug [X86-32] Disables the code which attempts to detect and 3241e52347bdSJani Nikula disable unhandled interrupt sources. 3242e52347bdSJani Nikula 3243e52347bdSJani Nikula no_timer_check [X86,APIC] Disables the code which tests for 3244e52347bdSJani Nikula broken timer IRQ sources. 3245e52347bdSJani Nikula 3246e52347bdSJani Nikula noisapnp [ISAPNP] Disables ISA PnP code. 3247e52347bdSJani Nikula 3248e52347bdSJani Nikula noinitrd [RAM] Tells the kernel not to load any configured 3249e52347bdSJani Nikula initial RAM disk. 3250e52347bdSJani Nikula 3251e52347bdSJani Nikula nointremap [X86-64, Intel-IOMMU] Do not enable interrupt 3252e52347bdSJani Nikula remapping. 3253e52347bdSJani Nikula [Deprecated - use intremap=off] 3254e52347bdSJani Nikula 3255e52347bdSJani Nikula nointroute [IA-64] 3256e52347bdSJani Nikula 3257e52347bdSJani Nikula noinvpcid [X86] Disable the INVPCID cpu feature. 3258e52347bdSJani Nikula 3259e52347bdSJani Nikula nojitter [IA-64] Disables jitter checking for ITC timers. 3260e52347bdSJani Nikula 3261e52347bdSJani Nikula no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver 3262e52347bdSJani Nikula 3263e52347bdSJani Nikula no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page 3264e52347bdSJani Nikula fault handling. 3265e52347bdSJani Nikula 3266e7aa8c2eSLinus Torvalds no-vmw-sched-clock 3267e7aa8c2eSLinus Torvalds [X86,PV_OPS] Disable paravirtualized VMware scheduler 3268e7aa8c2eSLinus Torvalds clock and use the default one. 3269e7aa8c2eSLinus Torvalds 3270e73a8f38SAlexey Makhalov no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time 3271e0685fa2SSteven Price accounting. steal time is computed, but won't 3272e0685fa2SSteven Price influence scheduler behaviour 3273e52347bdSJani Nikula 3274e52347bdSJani Nikula nolapic [X86-32,APIC] Do not enable or use the local APIC. 3275e52347bdSJani Nikula 3276e52347bdSJani Nikula nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 3277e52347bdSJani Nikula 3278e52347bdSJani Nikula noltlbs [PPC] Do not use large page/tlb entries for kernel 3279e52347bdSJani Nikula lowmem mapping on PPC40x and PPC8xx 3280e52347bdSJani Nikula 3281e52347bdSJani Nikula nomca [IA-64] Disable machine check abort handling 3282e52347bdSJani Nikula 3283e52347bdSJani Nikula nomce [X86-32] Disable Machine Check Exception 3284e52347bdSJani Nikula 3285e52347bdSJani Nikula nomfgpt [X86-32] Disable Multi-Function General Purpose 3286e52347bdSJani Nikula Timer usage (for AMD Geode machines). 3287e52347bdSJani Nikula 3288e52347bdSJani Nikula nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to 3289e52347bdSJani Nikula shutdown the other cpus. Instead use the REBOOT_VECTOR 3290e52347bdSJani Nikula irq. 3291e52347bdSJani Nikula 3292e52347bdSJani Nikula nomodule Disable module load 3293e52347bdSJani Nikula 3294e52347bdSJani Nikula nopat [X86] Disable PAT (page attribute table extension of 3295e52347bdSJani Nikula pagetables) support. 3296e52347bdSJani Nikula 32970790c9aaSAndy Lutomirski nopcid [X86-64] Disable the PCID cpu feature. 32980790c9aaSAndy Lutomirski 3299e52347bdSJani Nikula norandmaps Don't use address space randomization. Equivalent to 3300e52347bdSJani Nikula echo 0 > /proc/sys/kernel/randomize_va_space 3301e52347bdSJani Nikula 3302e52347bdSJani Nikula noreplace-smp [X86-32,SMP] Don't replace SMP instructions 3303e52347bdSJani Nikula with UP alternatives 3304e52347bdSJani Nikula 3305e52347bdSJani Nikula nordrand [X86] Disable kernel use of the RDRAND and 3306e52347bdSJani Nikula RDSEED instructions even if they are supported 3307e52347bdSJani Nikula by the processor. RDRAND and RDSEED are still 3308e52347bdSJani Nikula available to user space applications. 3309e52347bdSJani Nikula 3310e52347bdSJani Nikula noresume [SWSUSP] Disables resume and restores original swap 3311e52347bdSJani Nikula space. 3312e52347bdSJani Nikula 3313e52347bdSJani Nikula no-scroll [VGA] Disables scrollback. 3314e52347bdSJani Nikula This is required for the Braillex ib80-piezo Braille 3315e52347bdSJani Nikula reader made by F.H. Papenmeier (Germany). 3316e52347bdSJani Nikula 3317e52347bdSJani Nikula nosbagart [IA-64] 3318e52347bdSJani Nikula 3319e52347bdSJani Nikula nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 3320e52347bdSJani Nikula 3321e52347bdSJani Nikula nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 3322e52347bdSJani Nikula and disable the IO APIC. legacy for "maxcpus=0". 3323e52347bdSJani Nikula 3324e52347bdSJani Nikula nosoftlockup [KNL] Disable the soft-lockup detector. 3325e52347bdSJani Nikula 3326e52347bdSJani Nikula nosync [HW,M68K] Disables sync negotiation for all devices. 3327e52347bdSJani Nikula 3328e52347bdSJani Nikula nowatchdog [KNL] Disable both lockup detectors, i.e. 3329e52347bdSJani Nikula soft-lockup and NMI watchdog (hard-lockup). 3330e52347bdSJani Nikula 3331e52347bdSJani Nikula nowb [ARM] 3332e52347bdSJani Nikula 3333e52347bdSJani Nikula nox2apic [X86-64,APIC] Do not enable x2APIC mode. 3334e52347bdSJani Nikula 3335e52347bdSJani Nikula cpu0_hotplug [X86] Turn on CPU0 hotplug feature when 3336e52347bdSJani Nikula CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. 3337e52347bdSJani Nikula Some features depend on CPU0. Known dependencies are: 3338e52347bdSJani Nikula 1. Resume from suspend/hibernate depends on CPU0. 3339e52347bdSJani Nikula Suspend/hibernate will fail if CPU0 is offline and you 3340e52347bdSJani Nikula need to online CPU0 before suspend/hibernate. 3341e52347bdSJani Nikula 2. PIC interrupts also depend on CPU0. CPU0 can't be 3342e52347bdSJani Nikula removed if a PIC interrupt is detected. 3343e52347bdSJani Nikula It's said poweroff/reboot may depend on CPU0 on some 3344e52347bdSJani Nikula machines although I haven't seen such issues so far 3345e52347bdSJani Nikula after CPU0 is offline on a few tested machines. 3346e52347bdSJani Nikula If the dependencies are under your control, you can 3347e52347bdSJani Nikula turn on cpu0_hotplug. 3348e52347bdSJani Nikula 334935b55ef2SNoam Camus nps_mtm_hs_ctr= [KNL,ARC] 335035b55ef2SNoam Camus This parameter sets the maximum duration, in 335135b55ef2SNoam Camus cycles, each HW thread of the CTOP can run 335235b55ef2SNoam Camus without interruptions, before HW switches it. 335335b55ef2SNoam Camus The actual maximum duration is 16 times this 335435b55ef2SNoam Camus parameter's value. 335535b55ef2SNoam Camus Format: integer between 1 and 255 335635b55ef2SNoam Camus Default: 255 335735b55ef2SNoam Camus 3358e52347bdSJani Nikula nptcg= [IA-64] Override max number of concurrent global TLB 3359e52347bdSJani Nikula purges which is reported from either PAL_VM_SUMMARY or 3360e52347bdSJani Nikula SAL PALO. 3361e52347bdSJani Nikula 3362e52347bdSJani Nikula nr_cpus= [SMP] Maximum number of processors that an SMP kernel 3363e52347bdSJani Nikula could support. nr_cpus=n : n >= 1 limits the kernel to 3364e52347bdSJani Nikula support 'n' processors. It could be larger than the 3365e52347bdSJani Nikula number of already plugged CPU during bootup, later in 3366e52347bdSJani Nikula runtime you can physically add extra cpu until it reaches 3367e52347bdSJani Nikula n. So during boot up some boot time memory for per-cpu 3368e52347bdSJani Nikula variables need be pre-allocated for later physical cpu 3369e52347bdSJani Nikula hot plugging. 3370e52347bdSJani Nikula 3371e52347bdSJani Nikula nr_uarts= [SERIAL] maximum number of UARTs to be registered. 3372e52347bdSJani Nikula 3373e52347bdSJani Nikula numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing. 3374e52347bdSJani Nikula Allowed values are enable and disable 3375e52347bdSJani Nikula 3376e52347bdSJani Nikula numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 3377c9bff3eeSMichal Hocko 'node', 'default' can be specified 3378e52347bdSJani Nikula This can be set from sysctl after boot. 337957043247SMauro Carvalho Chehab See Documentation/admin-guide/sysctl/vm.rst for details. 3380e52347bdSJani Nikula 3381e52347bdSJani Nikula ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. 3382a74e2a22SMauro Carvalho Chehab See Documentation/core-api/debugging-via-ohci1394.rst for more 3383e52347bdSJani Nikula info. 3384e52347bdSJani Nikula 3385e52347bdSJani Nikula olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 3386e52347bdSJani Nikula Rather than timing out after 20 ms if an EC 3387e52347bdSJani Nikula command is not properly ACKed, override the length 3388e52347bdSJani Nikula of the timeout. We have interrupts disabled while 3389e52347bdSJani Nikula waiting for the ACK, so if this is set too high 3390e52347bdSJani Nikula interrupts *may* be lost! 3391e52347bdSJani Nikula 3392e52347bdSJani Nikula omap_mux= [OMAP] Override bootloader pin multiplexing. 3393e52347bdSJani Nikula Format: <mux_mode0.mode_name=value>... 3394e52347bdSJani Nikula For example, to override I2C bus2: 3395e52347bdSJani Nikula omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 3396e52347bdSJani Nikula 3397e52347bdSJani Nikula oprofile.timer= [HW] 3398e52347bdSJani Nikula Use timer interrupt instead of performance counters 3399e52347bdSJani Nikula 3400e52347bdSJani Nikula oprofile.cpu_type= Force an oprofile cpu type 3401e52347bdSJani Nikula This might be useful if you have an older oprofile 3402e52347bdSJani Nikula userland or if you want common events. 3403e52347bdSJani Nikula Format: { arch_perfmon } 3404e52347bdSJani Nikula arch_perfmon: [X86] Force use of architectural 3405e52347bdSJani Nikula perfmon on Intel CPUs instead of the 3406e52347bdSJani Nikula CPU specific event set. 3407e52347bdSJani Nikula timer: [X86] Force use of architectural NMI 3408e52347bdSJani Nikula timer mode (see also oprofile.timer 3409e52347bdSJani Nikula for generic hr timer mode) 3410e52347bdSJani Nikula 3411e52347bdSJani Nikula oops=panic Always panic on oopses. Default is to just kill the 3412e52347bdSJani Nikula process, but there is a small probability of 3413e52347bdSJani Nikula deadlocking the machine. 3414e52347bdSJani Nikula This will also cause panics on machine check exceptions. 3415e52347bdSJani Nikula Useful together with panic=30 to trigger a reboot. 3416e52347bdSJani Nikula 3417e900a918SDan Williams page_alloc.shuffle= 3418e900a918SDan Williams [KNL] Boolean flag to control whether the page allocator 3419e900a918SDan Williams should randomize its free lists. The randomization may 3420e900a918SDan Williams be automatically enabled if the kernel detects it is 3421e900a918SDan Williams running on a platform with a direct-mapped memory-side 3422e900a918SDan Williams cache, and this parameter can be used to 3423e900a918SDan Williams override/disable that behavior. The state of the flag 3424e900a918SDan Williams can be read from sysfs at: 3425e900a918SDan Williams /sys/module/page_alloc/parameters/shuffle. 3426e900a918SDan Williams 3427e52347bdSJani Nikula page_owner= [KNL] Boot-time page_owner enabling option. 3428e52347bdSJani Nikula Storage of the information about who allocated 3429e52347bdSJani Nikula each page is disabled in default. With this switch, 3430e52347bdSJani Nikula we can turn it on. 3431e52347bdSJani Nikula on: enable the feature 3432e52347bdSJani Nikula 3433e52347bdSJani Nikula page_poison= [KNL] Boot-time parameter changing the state of 34348c9a134cSKees Cook poisoning on the buddy allocator, available with 34358c9a134cSKees Cook CONFIG_PAGE_POISONING=y. 34368c9a134cSKees Cook off: turn off poisoning (default) 3437e52347bdSJani Nikula on: turn on poisoning 3438e52347bdSJani Nikula 3439e52347bdSJani Nikula panic= [KNL] Kernel behaviour on panic: delay <timeout> 3440e52347bdSJani Nikula timeout > 0: seconds before rebooting 3441e52347bdSJani Nikula timeout = 0: wait forever 3442e52347bdSJani Nikula timeout < 0: reboot immediately 3443e52347bdSJani Nikula Format: <timeout> 3444e52347bdSJani Nikula 3445d999bd93SFeng Tang panic_print= Bitmask for printing system info when panic happens. 3446d999bd93SFeng Tang User can chose combination of the following bits: 3447d999bd93SFeng Tang bit 0: print all tasks info 3448d999bd93SFeng Tang bit 1: print system memory info 3449d999bd93SFeng Tang bit 2: print timer info 3450d999bd93SFeng Tang bit 3: print locks info if CONFIG_LOCKDEP is on 3451d999bd93SFeng Tang bit 4: print ftrace buffer 3452de6da1e8SFeng Tang bit 5: print all printk messages in buffer 3453d999bd93SFeng Tang 3454db38d5c1SRafael Aquini panic_on_taint= Bitmask for conditionally calling panic() in add_taint() 3455db38d5c1SRafael Aquini Format: <hex>[,nousertaint] 3456db38d5c1SRafael Aquini Hexadecimal bitmask representing the set of TAINT flags 3457db38d5c1SRafael Aquini that will cause the kernel to panic when add_taint() is 3458db38d5c1SRafael Aquini called with any of the flags in this set. 3459db38d5c1SRafael Aquini The optional switch "nousertaint" can be utilized to 3460db38d5c1SRafael Aquini prevent userspace forced crashes by writing to sysctl 3461db38d5c1SRafael Aquini /proc/sys/kernel/tainted any flagset matching with the 3462db38d5c1SRafael Aquini bitmask set on panic_on_taint. 3463db38d5c1SRafael Aquini See Documentation/admin-guide/tainted-kernels.rst for 3464db38d5c1SRafael Aquini extra details on the taint flags that users can pick 3465db38d5c1SRafael Aquini to compose the bitmask to assign to panic_on_taint. 3466db38d5c1SRafael Aquini 3467e52347bdSJani Nikula panic_on_warn panic() instead of WARN(). Useful to cause kdump 3468e52347bdSJani Nikula on a WARN(). 3469e52347bdSJani Nikula 3470e52347bdSJani Nikula crash_kexec_post_notifiers 3471e52347bdSJani Nikula Run kdump after running panic-notifiers and dumping 3472e52347bdSJani Nikula kmsg. This only for the users who doubt kdump always 3473e52347bdSJani Nikula succeeds in any situation. 3474e52347bdSJani Nikula Note that this also increases risks of kdump failure, 3475e52347bdSJani Nikula because some panic notifiers can make the crashed 3476e52347bdSJani Nikula kernel more unstable. 3477e52347bdSJani Nikula 3478e52347bdSJani Nikula parkbd.port= [HW] Parallel port number the keyboard adapter is 3479e52347bdSJani Nikula connected to, default is 0. 3480e52347bdSJani Nikula Format: <parport#> 3481e52347bdSJani Nikula parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 3482e52347bdSJani Nikula 0 for XT, 1 for AT (default is AT). 3483e52347bdSJani Nikula Format: <mode> 3484e52347bdSJani Nikula 3485e52347bdSJani Nikula parport= [HW,PPT] Specify parallel ports. 0 disables. 3486e52347bdSJani Nikula Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 3487e52347bdSJani Nikula Use 'auto' to force the driver to use any 3488e52347bdSJani Nikula IRQ/DMA settings detected (the default is to 3489e52347bdSJani Nikula ignore detected IRQ/DMA settings because of 3490e52347bdSJani Nikula possible conflicts). You can specify the base 3491e52347bdSJani Nikula address, IRQ, and DMA settings; IRQ and DMA 3492e52347bdSJani Nikula should be numbers, or 'auto' (for using detected 3493e52347bdSJani Nikula settings on that particular port), or 'nofifo' 3494e52347bdSJani Nikula (to avoid using a FIFO even if it is detected). 3495e52347bdSJani Nikula Parallel ports are assigned in the order they 3496e52347bdSJani Nikula are specified on the command line, starting 3497e52347bdSJani Nikula with parport0. 3498e52347bdSJani Nikula 3499e52347bdSJani Nikula parport_init_mode= [HW,PPT] 3500e52347bdSJani Nikula Configure VIA parallel port to operate in 3501e52347bdSJani Nikula a specific mode. This is necessary on Pegasos 3502e52347bdSJani Nikula computer where firmware has no options for setting 3503e52347bdSJani Nikula up parallel port mode and sets it to spp. 3504e52347bdSJani Nikula Currently this function knows 686a and 8231 chips. 3505e52347bdSJani Nikula Format: [spp|ps2|epp|ecp|ecpepp] 3506e52347bdSJani Nikula 3507e52347bdSJani Nikula pause_on_oops= 3508e52347bdSJani Nikula Halt all CPUs after the first oops has been printed for 3509e52347bdSJani Nikula the specified number of seconds. This is to be used if 3510e52347bdSJani Nikula your oopses keep scrolling off the screen. 3511e52347bdSJani Nikula 3512e52347bdSJani Nikula pcbit= [HW,ISDN] 3513e52347bdSJani Nikula 3514e52347bdSJani Nikula pcd. [PARIDE] 3515e52347bdSJani Nikula See header of drivers/block/paride/pcd.c. 3516e7751617SMauro Carvalho Chehab See also Documentation/admin-guide/blockdev/paride.rst. 3517e52347bdSJani Nikula 351807d8d7e5SLogan Gunthorpe pci=option[,option...] [PCI] various PCI subsystem options. 351907d8d7e5SLogan Gunthorpe 352007d8d7e5SLogan Gunthorpe Some options herein operate on a specific device 352107d8d7e5SLogan Gunthorpe or a set of devices (<pci_dev>). These are 352207d8d7e5SLogan Gunthorpe specified in one of the following formats: 352307d8d7e5SLogan Gunthorpe 352445db3370SLogan Gunthorpe [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]* 352507d8d7e5SLogan Gunthorpe pci:<vendor>:<device>[:<subvendor>:<subdevice>] 352607d8d7e5SLogan Gunthorpe 352707d8d7e5SLogan Gunthorpe Note: the first format specifies a PCI 352807d8d7e5SLogan Gunthorpe bus/device/function address which may change 352907d8d7e5SLogan Gunthorpe if new hardware is inserted, if motherboard 353007d8d7e5SLogan Gunthorpe firmware changes, or due to changes caused 353107d8d7e5SLogan Gunthorpe by other kernel parameters. If the 353207d8d7e5SLogan Gunthorpe domain is left unspecified, it is 353345db3370SLogan Gunthorpe taken to be zero. Optionally, a path 353445db3370SLogan Gunthorpe to a device through multiple device/function 353545db3370SLogan Gunthorpe addresses can be specified after the base 353645db3370SLogan Gunthorpe address (this is more robust against 353745db3370SLogan Gunthorpe renumbering issues). The second format 353807d8d7e5SLogan Gunthorpe selects devices using IDs from the 353907d8d7e5SLogan Gunthorpe configuration space which may match multiple 354007d8d7e5SLogan Gunthorpe devices in the system. 354107d8d7e5SLogan Gunthorpe 354211eb0e0eSSinan Kaya earlydump dump PCI config space before the kernel 3543e52347bdSJani Nikula changes anything 3544e52347bdSJani Nikula off [X86] don't probe for the PCI bus 3545e52347bdSJani Nikula bios [X86-32] force use of PCI BIOS, don't access 3546e52347bdSJani Nikula the hardware directly. Use this if your machine 3547e52347bdSJani Nikula has a non-standard PCI host bridge. 3548e52347bdSJani Nikula nobios [X86-32] disallow use of PCI BIOS, only direct 3549e52347bdSJani Nikula hardware access methods are allowed. Use this 3550e52347bdSJani Nikula if you experience crashes upon bootup and you 3551e52347bdSJani Nikula suspect they are caused by the BIOS. 3552e52347bdSJani Nikula conf1 [X86] Force use of PCI Configuration Access 3553e52347bdSJani Nikula Mechanism 1 (config address in IO port 0xCF8, 3554e52347bdSJani Nikula data in IO port 0xCFC, both 32-bit). 3555e52347bdSJani Nikula conf2 [X86] Force use of PCI Configuration Access 3556e52347bdSJani Nikula Mechanism 2 (IO port 0xCF8 is an 8-bit port for 3557e52347bdSJani Nikula the function, IO port 0xCFA, also 8-bit, sets 3558e52347bdSJani Nikula bus number. The config space is then accessed 3559e52347bdSJani Nikula through ports 0xC000-0xCFFF). 3560e52347bdSJani Nikula See http://wiki.osdev.org/PCI for more info 3561e52347bdSJani Nikula on the configuration access mechanisms. 3562e52347bdSJani Nikula noaer [PCIE] If the PCIEAER kernel config parameter is 3563e52347bdSJani Nikula enabled, this kernel boot option can be used to 3564e52347bdSJani Nikula disable the use of PCIE advanced error reporting. 3565e52347bdSJani Nikula nodomains [PCI] Disable support for multiple PCI 3566e52347bdSJani Nikula root domains (aka PCI segments, in ACPI-speak). 3567e52347bdSJani Nikula nommconf [X86] Disable use of MMCONFIG for PCI 3568e52347bdSJani Nikula Configuration 3569e52347bdSJani Nikula check_enable_amd_mmconf [X86] check for and enable 3570e52347bdSJani Nikula properly configured MMIO access to PCI 3571e52347bdSJani Nikula config space on AMD family 10h CPU 3572e52347bdSJani Nikula nomsi [MSI] If the PCI_MSI kernel config parameter is 3573e52347bdSJani Nikula enabled, this kernel boot option can be used to 3574e52347bdSJani Nikula disable the use of MSI interrupts system-wide. 3575e52347bdSJani Nikula noioapicquirk [APIC] Disable all boot interrupt quirks. 3576e52347bdSJani Nikula Safety option to keep boot IRQs enabled. This 3577e52347bdSJani Nikula should never be necessary. 3578e52347bdSJani Nikula ioapicreroute [APIC] Enable rerouting of boot IRQs to the 3579e52347bdSJani Nikula primary IO-APIC for bridges that cannot disable 3580e52347bdSJani Nikula boot IRQs. This fixes a source of spurious IRQs 3581e52347bdSJani Nikula when the system masks IRQs. 3582e52347bdSJani Nikula noioapicreroute [APIC] Disable workaround that uses the 3583e52347bdSJani Nikula boot IRQ equivalent of an IRQ that connects to 3584e52347bdSJani Nikula a chipset where boot IRQs cannot be disabled. 3585e52347bdSJani Nikula The opposite of ioapicreroute. 3586e52347bdSJani Nikula biosirq [X86-32] Use PCI BIOS calls to get the interrupt 3587e52347bdSJani Nikula routing table. These calls are known to be buggy 3588e52347bdSJani Nikula on several machines and they hang the machine 3589e52347bdSJani Nikula when used, but on other computers it's the only 3590e52347bdSJani Nikula way to get the interrupt routing table. Try 3591e52347bdSJani Nikula this option if the kernel is unable to allocate 3592e52347bdSJani Nikula IRQs or discover secondary PCI buses on your 3593e52347bdSJani Nikula motherboard. 3594e52347bdSJani Nikula rom [X86] Assign address space to expansion ROMs. 3595e52347bdSJani Nikula Use with caution as certain devices share 3596e52347bdSJani Nikula address decoders between ROMs and other 3597e52347bdSJani Nikula resources. 3598e52347bdSJani Nikula norom [X86] Do not assign address space to 3599e52347bdSJani Nikula expansion ROMs that do not already have 3600e52347bdSJani Nikula BIOS assigned address ranges. 3601e52347bdSJani Nikula nobar [X86] Do not assign address space to the 3602e52347bdSJani Nikula BARs that weren't assigned by the BIOS. 3603e52347bdSJani Nikula irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 3604e52347bdSJani Nikula assigned automatically to PCI devices. You can 3605e52347bdSJani Nikula make the kernel exclude IRQs of your ISA cards 3606e52347bdSJani Nikula this way. 3607e52347bdSJani Nikula pirqaddr=0xAAAAA [X86] Specify the physical address 3608e52347bdSJani Nikula of the PIRQ table (normally generated 3609e52347bdSJani Nikula by the BIOS) if it is outside the 3610e52347bdSJani Nikula F0000h-100000h range. 3611e52347bdSJani Nikula lastbus=N [X86] Scan all buses thru bus #N. Can be 3612e52347bdSJani Nikula useful if the kernel is unable to find your 3613e52347bdSJani Nikula secondary buses and you want to tell it 3614e52347bdSJani Nikula explicitly which ones they are. 3615e52347bdSJani Nikula assign-busses [X86] Always assign all PCI bus 3616e52347bdSJani Nikula numbers ourselves, overriding 3617e52347bdSJani Nikula whatever the firmware may have done. 3618e52347bdSJani Nikula usepirqmask [X86] Honor the possible IRQ mask stored 3619e52347bdSJani Nikula in the BIOS $PIR table. This is needed on 3620e52347bdSJani Nikula some systems with broken BIOSes, notably 3621e52347bdSJani Nikula some HP Pavilion N5400 and Omnibook XE3 3622e52347bdSJani Nikula notebooks. This will have no effect if ACPI 3623e52347bdSJani Nikula IRQ routing is enabled. 3624e52347bdSJani Nikula noacpi [X86] Do not use ACPI for IRQ routing 3625e52347bdSJani Nikula or for PCI scanning. 3626e52347bdSJani Nikula use_crs [X86] Use PCI host bridge window information 3627e52347bdSJani Nikula from ACPI. On BIOSes from 2008 or later, this 3628e52347bdSJani Nikula is enabled by default. If you need to use this, 3629e52347bdSJani Nikula please report a bug. 3630e52347bdSJani Nikula nocrs [X86] Ignore PCI host bridge windows from ACPI. 3631e52347bdSJani Nikula If you need to use this, please report a bug. 3632e52347bdSJani Nikula routeirq Do IRQ routing for all PCI devices. 3633e52347bdSJani Nikula This is normally done in pci_enable_device(), 3634e52347bdSJani Nikula so this option is a temporary workaround 3635e52347bdSJani Nikula for broken drivers that don't call it. 3636e52347bdSJani Nikula skip_isa_align [X86] do not align io start addr, so can 3637e52347bdSJani Nikula handle more pci cards 3638e52347bdSJani Nikula noearly [X86] Don't do any early type 1 scanning. 3639e52347bdSJani Nikula This might help on some broken boards which 3640e52347bdSJani Nikula machine check when some devices' config space 3641e52347bdSJani Nikula is read. But various workarounds are disabled 3642e52347bdSJani Nikula and some IOMMU drivers will not work. 3643e52347bdSJani Nikula bfsort Sort PCI devices into breadth-first order. 3644e52347bdSJani Nikula This sorting is done to get a device 3645e52347bdSJani Nikula order compatible with older (<= 2.4) kernels. 3646e52347bdSJani Nikula nobfsort Don't sort PCI devices into breadth-first order. 3647e52347bdSJani Nikula pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) 3648e52347bdSJani Nikula tuning and use the BIOS-configured MPS defaults. 3649e52347bdSJani Nikula pcie_bus_safe Set every device's MPS to the largest value 3650e52347bdSJani Nikula supported by all devices below the root complex. 3651e52347bdSJani Nikula pcie_bus_perf Set device MPS to the largest allowable MPS 3652e52347bdSJani Nikula based on its parent bus. Also set MRRS (Max 3653e52347bdSJani Nikula Read Request Size) to the largest supported 3654e52347bdSJani Nikula value (no larger than the MPS that the device 3655e52347bdSJani Nikula or bus can support) for best performance. 3656e52347bdSJani Nikula pcie_bus_peer2peer Set every device's MPS to 128B, which 3657e52347bdSJani Nikula every device is guaranteed to support. This 3658e52347bdSJani Nikula configuration allows peer-to-peer DMA between 3659e52347bdSJani Nikula any pair of devices, possibly at the cost of 3660e52347bdSJani Nikula reduced performance. This also guarantees 3661e52347bdSJani Nikula that hot-added devices will work. 3662e52347bdSJani Nikula cbiosize=nn[KMG] The fixed amount of bus space which is 3663e52347bdSJani Nikula reserved for the CardBus bridge's IO window. 3664e52347bdSJani Nikula The default value is 256 bytes. 3665e52347bdSJani Nikula cbmemsize=nn[KMG] The fixed amount of bus space which is 3666e52347bdSJani Nikula reserved for the CardBus bridge's memory 3667e52347bdSJani Nikula window. The default value is 64 megabytes. 3668e52347bdSJani Nikula resource_alignment= 3669e52347bdSJani Nikula Format: 367007d8d7e5SLogan Gunthorpe [<order of align>@]<pci_dev>[; ...] 3671e52347bdSJani Nikula Specifies alignment and device to reassign 367207d8d7e5SLogan Gunthorpe aligned memory resources. How to 367307d8d7e5SLogan Gunthorpe specify the device is described above. 3674e52347bdSJani Nikula If <order of align> is not specified, 3675e52347bdSJani Nikula PAGE_SIZE is used as alignment. 36763b1b1ce3SAlexey Kardashevskiy A PCI-PCI bridge can be specified if resource 3677e52347bdSJani Nikula windows need to be expanded. 3678e52347bdSJani Nikula To specify the alignment for several 3679e52347bdSJani Nikula instances of a device, the PCI vendor, 3680e52347bdSJani Nikula device, subvendor, and subdevice may be 36813b1b1ce3SAlexey Kardashevskiy specified, e.g., 12@pci:8086:9c22:103c:198f 36823b1b1ce3SAlexey Kardashevskiy for 4096-byte alignment. 3683e52347bdSJani Nikula ecrc= Enable/disable PCIe ECRC (transaction layer 3684e52347bdSJani Nikula end-to-end CRC checking). 3685e52347bdSJani Nikula bios: Use BIOS/firmware settings. This is the 3686e52347bdSJani Nikula the default. 3687e52347bdSJani Nikula off: Turn ECRC off 3688e52347bdSJani Nikula on: Turn ECRC on. 3689e52347bdSJani Nikula hpiosize=nn[KMG] The fixed amount of bus space which is 3690e52347bdSJani Nikula reserved for hotplug bridge's IO window. 3691e52347bdSJani Nikula Default size is 256 bytes. 3692d7b8a217SNicholas Johnson hpmmiosize=nn[KMG] The fixed amount of bus space which is 3693d7b8a217SNicholas Johnson reserved for hotplug bridge's MMIO window. 3694d7b8a217SNicholas Johnson Default size is 2 megabytes. 3695d7b8a217SNicholas Johnson hpmmioprefsize=nn[KMG] The fixed amount of bus space which is 3696d7b8a217SNicholas Johnson reserved for hotplug bridge's MMIO_PREF window. 3697d7b8a217SNicholas Johnson Default size is 2 megabytes. 3698e52347bdSJani Nikula hpmemsize=nn[KMG] The fixed amount of bus space which is 3699d7b8a217SNicholas Johnson reserved for hotplug bridge's MMIO and 3700d7b8a217SNicholas Johnson MMIO_PREF window. 3701e52347bdSJani Nikula Default size is 2 megabytes. 3702e52347bdSJani Nikula hpbussize=nn The minimum amount of additional bus numbers 3703e52347bdSJani Nikula reserved for buses below a hotplug bridge. 3704e52347bdSJani Nikula Default is 1. 3705e52347bdSJani Nikula realloc= Enable/disable reallocating PCI bridge resources 3706e52347bdSJani Nikula if allocations done by BIOS are too small to 3707e52347bdSJani Nikula accommodate resources required by all child 3708e52347bdSJani Nikula devices. 3709e52347bdSJani Nikula off: Turn realloc off 3710e52347bdSJani Nikula on: Turn realloc on 3711e52347bdSJani Nikula realloc same as realloc=on 3712e52347bdSJani Nikula noari do not use PCIe ARI. 3713cef74409SGil Kupfer noats [PCIE, Intel-IOMMU, AMD-IOMMU] 3714cef74409SGil Kupfer do not use PCIe ATS (and IOMMU device IOTLB). 3715e52347bdSJani Nikula pcie_scan_all Scan all possible PCIe devices. Otherwise we 3716e52347bdSJani Nikula only look for one device below a PCIe downstream 3717e52347bdSJani Nikula port. 3718f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= big_root_window Try to add a big 64bit memory window to the PCIe 3719f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= root complex on AMD CPUs. Some GFX hardware 3720f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= can resize a BAR to allow access to all VRAM. 3721f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= Adding the window is slightly risky (it may 3722f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= conflict with unreported devices), so this 3723f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= taints the kernel. 3724aaca43fdSLogan Gunthorpe disable_acs_redir=<pci_dev>[; ...] 3725aaca43fdSLogan Gunthorpe Specify one or more PCI devices (in the format 3726aaca43fdSLogan Gunthorpe specified above) separated by semicolons. 3727aaca43fdSLogan Gunthorpe Each device specified will have the PCI ACS 3728aaca43fdSLogan Gunthorpe redirect capabilities forced off which will 3729aaca43fdSLogan Gunthorpe allow P2P traffic between devices through 3730aaca43fdSLogan Gunthorpe bridges without forcing it upstream. Note: 3731aaca43fdSLogan Gunthorpe this removes isolation between devices and 3732aaca43fdSLogan Gunthorpe may put more devices in an IOMMU group. 3733fbfe07d4SSebastian Ott force_floating [S390] Force usage of floating interrupts. 373456271303SSebastian Ott nomio [S390] Do not use MIO instructions. 3735de267a7cSPierre Morel norid [S390] ignore the RID field and force use of 3736de267a7cSPierre Morel one PCI domain per PCI function 3737e52347bdSJani Nikula 3738e52347bdSJani Nikula pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 3739e52347bdSJani Nikula Management. 3740e52347bdSJani Nikula off Disable ASPM. 3741e52347bdSJani Nikula force Enable ASPM even on devices that claim not to support it. 3742e52347bdSJani Nikula WARNING: Forcing ASPM on may cause system lockups. 3743e52347bdSJani Nikula 37444c0fd764SBjorn Helgaas pcie_ports= [PCIE] PCIe port services handling: 37454c0fd764SBjorn Helgaas native Use native PCIe services (PME, AER, DPC, PCIe hotplug) 37464c0fd764SBjorn Helgaas even if the platform doesn't give the OS permission to 37474c0fd764SBjorn Helgaas use them. This may cause conflicts if the platform 37484c0fd764SBjorn Helgaas also tries to use these services. 374935a0b237SOlof Johansson dpc-native Use native PCIe service for DPC only. May 375035a0b237SOlof Johansson cause conflicts if firmware uses AER or DPC. 37514c0fd764SBjorn Helgaas compat Disable native PCIe services (PME, AER, DPC, PCIe 37524c0fd764SBjorn Helgaas hotplug). 3753e52347bdSJani Nikula 3754e52347bdSJani Nikula pcie_port_pm= [PCIE] PCIe port power management handling: 3755e52347bdSJani Nikula off Disable power management of all PCIe ports 3756e52347bdSJani Nikula force Forcibly enable power management of all PCIe ports 3757e52347bdSJani Nikula 3758e52347bdSJani Nikula pcie_pme= [PCIE,PM] Native PCIe PME signaling options: 3759e52347bdSJani Nikula nomsi Do not use MSI for native PCIe PME signaling (this makes 3760e52347bdSJani Nikula all PCIe root ports use INTx for all services). 3761e52347bdSJani Nikula 3762e52347bdSJani Nikula pcmv= [HW,PCMCIA] BadgePAD 4 3763e52347bdSJani Nikula 3764e52347bdSJani Nikula pd_ignore_unused 3765e52347bdSJani Nikula [PM] 3766e52347bdSJani Nikula Keep all power-domains already enabled by bootloader on, 3767e52347bdSJani Nikula even if no driver has claimed them. This is useful 3768e52347bdSJani Nikula for debug and development, but should not be 3769e52347bdSJani Nikula needed on a platform with proper driver support. 3770e52347bdSJani Nikula 3771e52347bdSJani Nikula pd. [PARIDE] 3772e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 3773e52347bdSJani Nikula 3774e52347bdSJani Nikula pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 3775e52347bdSJani Nikula boot time. 3776e52347bdSJani Nikula Format: { 0 | 1 } 3777e52347bdSJani Nikula See arch/parisc/kernel/pdc_chassis.c 3778e52347bdSJani Nikula 3779e52347bdSJani Nikula percpu_alloc= Select which percpu first chunk allocator to use. 3780e52347bdSJani Nikula Currently supported values are "embed" and "page". 3781e52347bdSJani Nikula Archs may support subset or none of the selections. 3782e52347bdSJani Nikula See comments in mm/percpu.c for details on each 3783e52347bdSJani Nikula allocator. This parameter is primarily for debugging 3784e52347bdSJani Nikula and performance comparison. 3785e52347bdSJani Nikula 3786e52347bdSJani Nikula pf. [PARIDE] 3787e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 3788e52347bdSJani Nikula 3789e52347bdSJani Nikula pg. [PARIDE] 3790e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 3791e52347bdSJani Nikula 3792e52347bdSJani Nikula pirq= [SMP,APIC] Manual mp-table setup 3793cb1aaebeSMauro Carvalho Chehab See Documentation/x86/i386/IO-APIC.rst. 3794e52347bdSJani Nikula 3795e52347bdSJani Nikula plip= [PPT,NET] Parallel port network link 3796e52347bdSJani Nikula Format: { parport<nr> | timid | 0 } 37973ba9b1b8STom Saeger See also Documentation/admin-guide/parport.rst. 3798e52347bdSJani Nikula 3799e52347bdSJani Nikula pmtmr= [X86] Manual setup of pmtmr I/O Port. 3800e52347bdSJani Nikula Override pmtimer IOPort with a hex value. 3801e52347bdSJani Nikula e.g. pmtmr=0x508 3802e52347bdSJani Nikula 3803db96a759SChen Yu pm_debug_messages [SUSPEND,KNL] 3804db96a759SChen Yu Enable suspend/resume debug messages during boot up. 3805db96a759SChen Yu 3806e52347bdSJani Nikula pnp.debug=1 [PNP] 3807e52347bdSJani Nikula Enable PNP debug messages (depends on the 3808e52347bdSJani Nikula CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time 3809e52347bdSJani Nikula via /sys/module/pnp/parameters/debug. We always show 3810e52347bdSJani Nikula current resource usage; turning this on also shows 3811e52347bdSJani Nikula possible settings and some assignment information. 3812e52347bdSJani Nikula 3813e52347bdSJani Nikula pnpacpi= [ACPI] 3814e52347bdSJani Nikula { off } 3815e52347bdSJani Nikula 3816e52347bdSJani Nikula pnpbios= [ISAPNP] 3817e52347bdSJani Nikula { on | off | curr | res | no-curr | no-res } 3818e52347bdSJani Nikula 3819e52347bdSJani Nikula pnp_reserve_irq= 3820e52347bdSJani Nikula [ISAPNP] Exclude IRQs for the autoconfiguration 3821e52347bdSJani Nikula 3822e52347bdSJani Nikula pnp_reserve_dma= 3823e52347bdSJani Nikula [ISAPNP] Exclude DMAs for the autoconfiguration 3824e52347bdSJani Nikula 3825e52347bdSJani Nikula pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 3826e52347bdSJani Nikula Ranges are in pairs (I/O port base and size). 3827e52347bdSJani Nikula 3828e52347bdSJani Nikula pnp_reserve_mem= 3829e52347bdSJani Nikula [ISAPNP] Exclude memory regions for the 3830e52347bdSJani Nikula autoconfiguration. 3831e52347bdSJani Nikula Ranges are in pairs (memory base and size). 3832e52347bdSJani Nikula 3833e52347bdSJani Nikula ports= [IP_VS_FTP] IPVS ftp helper module 3834e52347bdSJani Nikula Default is 21. 3835e52347bdSJani Nikula Up to 8 (IP_VS_APP_MAX_PORTS) ports 3836e52347bdSJani Nikula may be specified. 3837e52347bdSJani Nikula Format: <port>,<port>.... 3838e52347bdSJani Nikula 3839c3cbd075SBalbir Singh powersave=off [PPC] This option disables power saving features. 3840c3cbd075SBalbir Singh It specifically disables cpuidle and sets the 3841c3cbd075SBalbir Singh platform machine description specific power_save 3842c3cbd075SBalbir Singh function to NULL. On Idle the CPU just reduces 3843c3cbd075SBalbir Singh execution priority. 3844c3cbd075SBalbir Singh 3845e52347bdSJani Nikula ppc_strict_facility_enable 3846e52347bdSJani Nikula [PPC] This option catches any kernel floating point, 3847e52347bdSJani Nikula Altivec, VSX and SPE outside of regions specifically 3848e52347bdSJani Nikula allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). 3849e52347bdSJani Nikula There is some performance impact when enabling this. 3850e52347bdSJani Nikula 385107fd1761SCyril Bur ppc_tm= [PPC] 385207fd1761SCyril Bur Format: {"off"} 385307fd1761SCyril Bur Disable Hardware Transactional Memory 385407fd1761SCyril Bur 3855e52347bdSJani Nikula print-fatal-signals= 3856e52347bdSJani Nikula [KNL] debug: print fatal signals 3857e52347bdSJani Nikula 3858e52347bdSJani Nikula If enabled, warn about various signal handling 3859e52347bdSJani Nikula related application anomalies: too many signals, 3860e52347bdSJani Nikula too many POSIX.1 timers, fatal signals causing a 3861e52347bdSJani Nikula coredump - etc. 3862e52347bdSJani Nikula 3863e52347bdSJani Nikula If you hit the warning due to signal overflow, 3864e52347bdSJani Nikula you might want to try "ulimit -i unlimited". 3865e52347bdSJani Nikula 3866e52347bdSJani Nikula default: off. 3867e52347bdSJani Nikula 3868e52347bdSJani Nikula printk.always_kmsg_dump= 3869e52347bdSJani Nikula Trigger kmsg_dump for cases other than kernel oops or 3870e52347bdSJani Nikula panics 3871e52347bdSJani Nikula Format: <bool> (1/Y/y=enable, 0/N/n=disable) 3872e52347bdSJani Nikula default: disabled 3873e52347bdSJani Nikula 3874e52347bdSJani Nikula printk.devkmsg={on,off,ratelimit} 3875e52347bdSJani Nikula Control writing to /dev/kmsg. 3876e52347bdSJani Nikula on - unlimited logging to /dev/kmsg from userspace 3877e52347bdSJani Nikula off - logging to /dev/kmsg disabled 3878e52347bdSJani Nikula ratelimit - ratelimit the logging 3879e52347bdSJani Nikula Default: ratelimit 3880e52347bdSJani Nikula 3881e52347bdSJani Nikula printk.time= Show timing data prefixed to each printk message line 3882e52347bdSJani Nikula Format: <bool> (1/Y/y=enable, 0/N/n=disable) 3883e52347bdSJani Nikula 3884e52347bdSJani Nikula processor.max_cstate= [HW,ACPI] 3885e52347bdSJani Nikula Limit processor to maximum C-state 3886e52347bdSJani Nikula max_cstate=9 overrides any DMI blacklist limit. 3887e52347bdSJani Nikula 3888e52347bdSJani Nikula processor.nocst [HW,ACPI] 3889e52347bdSJani Nikula Ignore the _CST method to determine C-states, 3890e52347bdSJani Nikula instead using the legacy FADT method 3891e52347bdSJani Nikula 3892e52347bdSJani Nikula profile= [KNL] Enable kernel profiling via /proc/profile 3893e7e61fc0SRandy Dunlap Format: [<profiletype>,]<number> 3894e7e61fc0SRandy Dunlap Param: <profiletype>: "schedule", "sleep", or "kvm" 3895e7e61fc0SRandy Dunlap [defaults to kernel profiling] 3896e52347bdSJani Nikula Param: "schedule" - profile schedule points. 3897e52347bdSJani Nikula Param: "sleep" - profile D-state sleeping (millisecs). 3898e52347bdSJani Nikula Requires CONFIG_SCHEDSTATS 3899e52347bdSJani Nikula Param: "kvm" - profile VM exits. 3900e7e61fc0SRandy Dunlap Param: <number> - step/bucket size as a power of 2 for 3901e7e61fc0SRandy Dunlap statistical time based profiling. 3902e52347bdSJani Nikula 3903e52347bdSJani Nikula prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 3904e52347bdSJani Nikula before loading. 3905e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/ramdisk.rst. 3906e52347bdSJani Nikula 3907ecdc5d84SVasily Gorbik prot_virt= [S390] enable hosting protected virtual machines 3908ecdc5d84SVasily Gorbik isolated from the hypervisor (if hardware supports 3909ecdc5d84SVasily Gorbik that). 3910ecdc5d84SVasily Gorbik Format: <bool> 3911ecdc5d84SVasily Gorbik 3912e0c27447SJohannes Weiner psi= [KNL] Enable or disable pressure stall information 3913e0c27447SJohannes Weiner tracking. 3914e0c27447SJohannes Weiner Format: <bool> 3915e0c27447SJohannes Weiner 3916e52347bdSJani Nikula psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 3917e52347bdSJani Nikula probe for; one of (bare|imps|exps|lifebook|any). 3918e52347bdSJani Nikula psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 3919e52347bdSJani Nikula per second. 3920e52347bdSJani Nikula psmouse.resetafter= [HW,MOUSE] 3921e52347bdSJani Nikula Try to reset the device after so many bad packets 3922e52347bdSJani Nikula (0 = never). 3923e52347bdSJani Nikula psmouse.resolution= 3924e52347bdSJani Nikula [HW,MOUSE] Set desired mouse resolution, in dpi. 3925e52347bdSJani Nikula psmouse.smartscroll= 3926e52347bdSJani Nikula [HW,MOUSE] Controls Logitech smartscroll autorepeat. 3927e52347bdSJani Nikula 0 = disabled, 1 = enabled (default). 3928e52347bdSJani Nikula 3929e52347bdSJani Nikula pstore.backend= Specify the name of the pstore backend to use 3930e52347bdSJani Nikula 3931e52347bdSJani Nikula pt. [PARIDE] 3932e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 3933e52347bdSJani Nikula 393401c9b17bSDave Hansen pti= [X86_64] Control Page Table Isolation of user and 393501c9b17bSDave Hansen kernel address spaces. Disabling this feature 393601c9b17bSDave Hansen removes hardening, but improves performance of 393701c9b17bSDave Hansen system calls and interrupts. 393801c9b17bSDave Hansen 393901c9b17bSDave Hansen on - unconditionally enable 394001c9b17bSDave Hansen off - unconditionally disable 394101c9b17bSDave Hansen auto - kernel detects whether your CPU model is 394201c9b17bSDave Hansen vulnerable to issues that PTI mitigates 394301c9b17bSDave Hansen 394401c9b17bSDave Hansen Not specifying this option is equivalent to pti=auto. 394501c9b17bSDave Hansen 394601c9b17bSDave Hansen nopti [X86_64] 394701c9b17bSDave Hansen Equivalent to pti=off 394841f4c20bSBorislav Petkov 3949e52347bdSJani Nikula pty.legacy_count= 3950e52347bdSJani Nikula [KNL] Number of legacy pty's. Overwrites compiled-in 3951e52347bdSJani Nikula default number. 3952e52347bdSJani Nikula 3953e52347bdSJani Nikula quiet [KNL] Disable most log messages 3954e52347bdSJani Nikula 3955e52347bdSJani Nikula r128= [HW,DRM] 3956e52347bdSJani Nikula 3957e52347bdSJani Nikula raid= [HW,RAID] 3958e52347bdSJani Nikula See Documentation/admin-guide/md.rst. 3959e52347bdSJani Nikula 3960e52347bdSJani Nikula ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 3961e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/ramdisk.rst. 3962e52347bdSJani Nikula 39639b254366SKees Cook random.trust_cpu={on,off} 39649b254366SKees Cook [KNL] Enable or disable trusting the use of the 39659b254366SKees Cook CPU's random number generator (if available) to 39669b254366SKees Cook fully seed the kernel's CRNG. Default is controlled 39679b254366SKees Cook by CONFIG_RANDOM_TRUST_CPU. 39689b254366SKees Cook 3969011d8261SBorislav Petkov ras=option[,option,...] [KNL] RAS-specific options 3970011d8261SBorislav Petkov 3971011d8261SBorislav Petkov cec_disable [X86] 3972011d8261SBorislav Petkov Disable the Correctable Errors Collector, 3973011d8261SBorislav Petkov see CONFIG_RAS_CEC help text. 3974011d8261SBorislav Petkov 3975e52347bdSJani Nikula rcu_nocbs= [KNL] 3976da8739f2SPaul E. McKenney The argument is a cpu list, as described above, 3977da8739f2SPaul E. McKenney except that the string "all" can be used to 3978da8739f2SPaul E. McKenney specify every CPU on the system. 3979e52347bdSJani Nikula 3980e52347bdSJani Nikula In kernels built with CONFIG_RCU_NOCB_CPU=y, set 3981e52347bdSJani Nikula the specified list of CPUs to be no-callback CPUs. 398277095901SPaul E. McKenney Invocation of these CPUs' RCU callbacks will be 398377095901SPaul E. McKenney offloaded to "rcuox/N" kthreads created for that 398477095901SPaul E. McKenney purpose, where "x" is "p" for RCU-preempt, and 398577095901SPaul E. McKenney "s" for RCU-sched, and "N" is the CPU number. 398677095901SPaul E. McKenney This reduces OS jitter on the offloaded CPUs, 398777095901SPaul E. McKenney which can be useful for HPC and real-time 398877095901SPaul E. McKenney workloads. It can also improve energy efficiency 398977095901SPaul E. McKenney for asymmetric multiprocessors. 3990e52347bdSJani Nikula 3991e52347bdSJani Nikula rcu_nocb_poll [KNL] 3992e52347bdSJani Nikula Rather than requiring that offloaded CPUs 3993e52347bdSJani Nikula (specified by rcu_nocbs= above) explicitly 3994e52347bdSJani Nikula awaken the corresponding "rcuoN" kthreads, 3995e52347bdSJani Nikula make these kthreads poll for callbacks. 3996e52347bdSJani Nikula This improves the real-time response for the 3997e52347bdSJani Nikula offloaded CPUs by relieving them of the need to 3998e52347bdSJani Nikula wake up the corresponding kthread, but degrades 3999e52347bdSJani Nikula energy efficiency by requiring that the kthreads 4000e52347bdSJani Nikula periodically wake up to do the polling. 4001e52347bdSJani Nikula 4002e52347bdSJani Nikula rcutree.blimit= [KNL] 4003e52347bdSJani Nikula Set maximum number of finished RCU callbacks to 4004e52347bdSJani Nikula process in one batch. 4005e52347bdSJani Nikula 4006e52347bdSJani Nikula rcutree.dump_tree= [KNL] 4007e52347bdSJani Nikula Dump the structure of the rcu_node combining tree 4008e52347bdSJani Nikula out at early boot. This is used for diagnostic 4009e52347bdSJani Nikula purposes, to verify correct tree setup. 4010e52347bdSJani Nikula 4011e52347bdSJani Nikula rcutree.gp_cleanup_delay= [KNL] 4012e52347bdSJani Nikula Set the number of jiffies to delay each step of 401390040c9eSPaul E. McKenney RCU grace-period cleanup. 4014e52347bdSJani Nikula 4015e52347bdSJani Nikula rcutree.gp_init_delay= [KNL] 4016e52347bdSJani Nikula Set the number of jiffies to delay each step of 401790040c9eSPaul E. McKenney RCU grace-period initialization. 4018e52347bdSJani Nikula 4019e52347bdSJani Nikula rcutree.gp_preinit_delay= [KNL] 4020e52347bdSJani Nikula Set the number of jiffies to delay each step of 4021e52347bdSJani Nikula RCU grace-period pre-initialization, that is, 4022e52347bdSJani Nikula the propagation of recent CPU-hotplug changes up 402390040c9eSPaul E. McKenney the rcu_node combining tree. 4024e52347bdSJani Nikula 402548d07c04SSebastian Andrzej Siewior rcutree.use_softirq= [KNL] 402648d07c04SSebastian Andrzej Siewior If set to zero, move all RCU_SOFTIRQ processing to 402748d07c04SSebastian Andrzej Siewior per-CPU rcuc kthreads. Defaults to a non-zero 402848d07c04SSebastian Andrzej Siewior value, meaning that RCU_SOFTIRQ is used by default. 402948d07c04SSebastian Andrzej Siewior Specify rcutree.use_softirq=0 to use rcuc kthreads. 403048d07c04SSebastian Andrzej Siewior 4031e52347bdSJani Nikula rcutree.rcu_fanout_exact= [KNL] 4032e52347bdSJani Nikula Disable autobalancing of the rcu_node combining 4033e52347bdSJani Nikula tree. This is used by rcutorture, and might 4034e52347bdSJani Nikula possibly be useful for architectures having high 4035e52347bdSJani Nikula cache-to-cache transfer latencies. 4036e52347bdSJani Nikula 4037e52347bdSJani Nikula rcutree.rcu_fanout_leaf= [KNL] 4038e52347bdSJani Nikula Change the number of CPUs assigned to each 4039e52347bdSJani Nikula leaf rcu_node structure. Useful for very 4040e52347bdSJani Nikula large systems, which will choose the value 64, 4041e52347bdSJani Nikula and for NUMA systems with large remote-access 4042e52347bdSJani Nikula latencies, which will choose a value aligned 4043e52347bdSJani Nikula with the appropriate hardware boundaries. 4044e52347bdSJani Nikula 4045e52347bdSJani Nikula rcutree.jiffies_till_first_fqs= [KNL] 4046e52347bdSJani Nikula Set delay from grace-period initialization to 4047e52347bdSJani Nikula first attempt to force quiescent states. 4048e52347bdSJani Nikula Units are jiffies, minimum value is zero, 4049e52347bdSJani Nikula and maximum value is HZ. 4050e52347bdSJani Nikula 4051e52347bdSJani Nikula rcutree.jiffies_till_next_fqs= [KNL] 4052e52347bdSJani Nikula Set delay between subsequent attempts to force 4053e52347bdSJani Nikula quiescent states. Units are jiffies, minimum 4054e52347bdSJani Nikula value is one, and maximum value is HZ. 4055e52347bdSJani Nikula 40561a4762b9SPaul E. McKenney rcutree.jiffies_till_sched_qs= [KNL] 40571a4762b9SPaul E. McKenney Set required age in jiffies for a 40581a4762b9SPaul E. McKenney given grace period before RCU starts 40591a4762b9SPaul E. McKenney soliciting quiescent-state help from 40601a4762b9SPaul E. McKenney rcu_note_context_switch() and cond_resched(). 40611a4762b9SPaul E. McKenney If not specified, the kernel will calculate 40621a4762b9SPaul E. McKenney a value based on the most recent settings 40631a4762b9SPaul E. McKenney of rcutree.jiffies_till_first_fqs 40641a4762b9SPaul E. McKenney and rcutree.jiffies_till_next_fqs. 40651a4762b9SPaul E. McKenney This calculated value may be viewed in 40661a4762b9SPaul E. McKenney rcutree.jiffies_to_sched_qs. Any attempt to set 40671a4762b9SPaul E. McKenney rcutree.jiffies_to_sched_qs will be cheerfully 40681a4762b9SPaul E. McKenney overwritten. 40691a4762b9SPaul E. McKenney 4070e52347bdSJani Nikula rcutree.kthread_prio= [KNL,BOOT] 4071e52347bdSJani Nikula Set the SCHED_FIFO priority of the RCU per-CPU 4072e52347bdSJani Nikula kthreads (rcuc/N). This value is also used for 4073e52347bdSJani Nikula the priority of the RCU boost threads (rcub/N) 4074e52347bdSJani Nikula and for the RCU grace-period kthreads (rcu_bh, 4075e52347bdSJani Nikula rcu_preempt, and rcu_sched). If RCU_BOOST is 4076e52347bdSJani Nikula set, valid values are 1-99 and the default is 1 4077e52347bdSJani Nikula (the least-favored priority). Otherwise, when 4078e52347bdSJani Nikula RCU_BOOST is not set, valid values are 0-99 and 4079e52347bdSJani Nikula the default is zero (non-realtime operation). 4080e52347bdSJani Nikula 4081f7c612b0SPaul E. McKenney rcutree.rcu_nocb_gp_stride= [KNL] 4082f7c612b0SPaul E. McKenney Set the number of NOCB callback kthreads in 4083f7c612b0SPaul E. McKenney each group, which defaults to the square root 4084f7c612b0SPaul E. McKenney of the number of CPUs. Larger numbers reduce 4085f7c612b0SPaul E. McKenney the wakeup overhead on the global grace-period 4086f7c612b0SPaul E. McKenney kthread, but increases that same overhead on 4087f7c612b0SPaul E. McKenney each group's NOCB grace-period kthread. 4088e52347bdSJani Nikula 4089e52347bdSJani Nikula rcutree.qhimark= [KNL] 4090e52347bdSJani Nikula Set threshold of queued RCU callbacks beyond which 4091e52347bdSJani Nikula batch limiting is disabled. 4092e52347bdSJani Nikula 4093e52347bdSJani Nikula rcutree.qlowmark= [KNL] 4094e52347bdSJani Nikula Set threshold of queued RCU callbacks below which 4095e52347bdSJani Nikula batch limiting is re-enabled. 4096e52347bdSJani Nikula 4097b2b00ddfSPaul E. McKenney rcutree.qovld= [KNL] 4098b2b00ddfSPaul E. McKenney Set threshold of queued RCU callbacks beyond which 4099b2b00ddfSPaul E. McKenney RCU's force-quiescent-state scan will aggressively 4100b2b00ddfSPaul E. McKenney enlist help from cond_resched() and sched IPIs to 4101b2b00ddfSPaul E. McKenney help CPUs more quickly reach quiescent states. 4102b2b00ddfSPaul E. McKenney Set to less than zero to make this be set based 4103b2b00ddfSPaul E. McKenney on rcutree.qhimark at boot time and to zero to 4104b2b00ddfSPaul E. McKenney disable more aggressive help enlistment. 4105b2b00ddfSPaul E. McKenney 4106e52347bdSJani Nikula rcutree.rcu_idle_gp_delay= [KNL] 4107e52347bdSJani Nikula Set wakeup interval for idle CPUs that have 4108e52347bdSJani Nikula RCU callbacks (RCU_FAST_NO_HZ=y). 4109e52347bdSJani Nikula 4110e52347bdSJani Nikula rcutree.rcu_idle_lazy_gp_delay= [KNL] 4111e52347bdSJani Nikula Set wakeup interval for idle CPUs that have 4112e52347bdSJani Nikula only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y). 4113e52347bdSJani Nikula Lazy RCU callbacks are those which RCU can 4114e52347bdSJani Nikula prove do nothing more than free memory. 4115e52347bdSJani Nikula 4116e3c50dfbSPaul E. McKenney rcutree.rcu_kick_kthreads= [KNL] 4117e3c50dfbSPaul E. McKenney Cause the grace-period kthread to get an extra 4118e3c50dfbSPaul E. McKenney wake_up() if it sleeps three times longer than 4119e3c50dfbSPaul E. McKenney it should at force-quiescent-state time. 4120e3c50dfbSPaul E. McKenney This wake_up() will be accompanied by a 4121e3c50dfbSPaul E. McKenney WARN_ONCE() splat and an ftrace_dump(). 4122e3c50dfbSPaul E. McKenney 41232ccaff10SPaul E. McKenney rcutree.sysrq_rcu= [KNL] 41242ccaff10SPaul E. McKenney Commandeer a sysrq key to dump out Tree RCU's 41252ccaff10SPaul E. McKenney rcu_node tree with an eye towards determining 41262ccaff10SPaul E. McKenney why a new grace period has not yet started. 41272ccaff10SPaul E. McKenney 4128881ed593SPaul E. McKenney rcuperf.gp_async= [KNL] 4129881ed593SPaul E. McKenney Measure performance of asynchronous 4130881ed593SPaul E. McKenney grace-period primitives such as call_rcu(). 4131881ed593SPaul E. McKenney 4132881ed593SPaul E. McKenney rcuperf.gp_async_max= [KNL] 4133881ed593SPaul E. McKenney Specify the maximum number of outstanding 4134881ed593SPaul E. McKenney callbacks per writer thread. When a writer 4135881ed593SPaul E. McKenney thread exceeds this limit, it invokes the 4136881ed593SPaul E. McKenney corresponding flavor of rcu_barrier() to allow 4137881ed593SPaul E. McKenney previously posted callbacks to drain. 4138881ed593SPaul E. McKenney 4139e52347bdSJani Nikula rcuperf.gp_exp= [KNL] 4140e52347bdSJani Nikula Measure performance of expedited synchronous 4141e52347bdSJani Nikula grace-period primitives. 4142e52347bdSJani Nikula 4143e52347bdSJani Nikula rcuperf.holdoff= [KNL] 4144e52347bdSJani Nikula Set test-start holdoff period. The purpose of 4145e52347bdSJani Nikula this parameter is to delay the start of the 4146e52347bdSJani Nikula test until boot completes in order to avoid 4147e52347bdSJani Nikula interference. 4148e52347bdSJani Nikula 4149e6e78b00SJoel Fernandes (Google) rcuperf.kfree_rcu_test= [KNL] 4150e6e78b00SJoel Fernandes (Google) Set to measure performance of kfree_rcu() flooding. 4151e6e78b00SJoel Fernandes (Google) 4152e6e78b00SJoel Fernandes (Google) rcuperf.kfree_nthreads= [KNL] 4153e6e78b00SJoel Fernandes (Google) The number of threads running loops of kfree_rcu(). 4154e6e78b00SJoel Fernandes (Google) 4155e6e78b00SJoel Fernandes (Google) rcuperf.kfree_alloc_num= [KNL] 4156e6e78b00SJoel Fernandes (Google) Number of allocations and frees done in an iteration. 4157e6e78b00SJoel Fernandes (Google) 4158e6e78b00SJoel Fernandes (Google) rcuperf.kfree_loops= [KNL] 4159e6e78b00SJoel Fernandes (Google) Number of loops doing rcuperf.kfree_alloc_num number 4160e6e78b00SJoel Fernandes (Google) of allocations and frees. 4161e6e78b00SJoel Fernandes (Google) 4162e52347bdSJani Nikula rcuperf.nreaders= [KNL] 4163e52347bdSJani Nikula Set number of RCU readers. The value -1 selects 4164e52347bdSJani Nikula N, where N is the number of CPUs. A value 4165e52347bdSJani Nikula "n" less than -1 selects N-n+1, where N is again 4166e52347bdSJani Nikula the number of CPUs. For example, -2 selects N 4167e52347bdSJani Nikula (the number of CPUs), -3 selects N+1, and so on. 4168e52347bdSJani Nikula A value of "n" less than or equal to -N selects 4169e52347bdSJani Nikula a single reader. 4170e52347bdSJani Nikula 4171e52347bdSJani Nikula rcuperf.nwriters= [KNL] 4172e52347bdSJani Nikula Set number of RCU writers. The values operate 4173e52347bdSJani Nikula the same as for rcuperf.nreaders. 4174e52347bdSJani Nikula N, where N is the number of CPUs 4175e52347bdSJani Nikula 4176820687a7SPaul E. McKenney rcuperf.perf_type= [KNL] 4177820687a7SPaul E. McKenney Specify the RCU implementation to test. 4178820687a7SPaul E. McKenney 4179e52347bdSJani Nikula rcuperf.shutdown= [KNL] 4180e52347bdSJani Nikula Shut the system down after performance tests 4181e52347bdSJani Nikula complete. This is useful for hands-off automated 4182e52347bdSJani Nikula testing. 4183e52347bdSJani Nikula 4184e52347bdSJani Nikula rcuperf.verbose= [KNL] 4185e52347bdSJani Nikula Enable additional printk() statements. 4186e52347bdSJani Nikula 4187820687a7SPaul E. McKenney rcuperf.writer_holdoff= [KNL] 4188820687a7SPaul E. McKenney Write-side holdoff between grace periods, 4189820687a7SPaul E. McKenney in microseconds. The default of zero says 4190820687a7SPaul E. McKenney no holdoff. 4191820687a7SPaul E. McKenney 4192e52347bdSJani Nikula rcutorture.fqs_duration= [KNL] 4193e52347bdSJani Nikula Set duration of force_quiescent_state bursts 4194e52347bdSJani Nikula in microseconds. 4195e52347bdSJani Nikula 4196e52347bdSJani Nikula rcutorture.fqs_holdoff= [KNL] 4197e52347bdSJani Nikula Set holdoff time within force_quiescent_state bursts 4198e52347bdSJani Nikula in microseconds. 4199e52347bdSJani Nikula 4200e52347bdSJani Nikula rcutorture.fqs_stutter= [KNL] 4201e52347bdSJani Nikula Set wait time between force_quiescent_state bursts 4202e52347bdSJani Nikula in seconds. 4203e52347bdSJani Nikula 4204ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress= [KNL] 4205ed8f6fb2SPaul E. McKenney Enable RCU grace-period forward-progress testing 4206ed8f6fb2SPaul E. McKenney for the types of RCU supporting this notion. 4207ed8f6fb2SPaul E. McKenney 4208ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_div= [KNL] 4209ed8f6fb2SPaul E. McKenney Specify the fraction of a CPU-stall-warning 4210ed8f6fb2SPaul E. McKenney period to do tight-loop forward-progress testing. 4211ed8f6fb2SPaul E. McKenney 4212ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_holdoff= [KNL] 4213ed8f6fb2SPaul E. McKenney Number of seconds to wait between successive 4214ed8f6fb2SPaul E. McKenney forward-progress tests. 4215ed8f6fb2SPaul E. McKenney 4216ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_need_resched= [KNL] 4217ed8f6fb2SPaul E. McKenney Enclose cond_resched() calls within checks for 4218ed8f6fb2SPaul E. McKenney need_resched() during tight-loop forward-progress 4219ed8f6fb2SPaul E. McKenney testing. 4220ed8f6fb2SPaul E. McKenney 4221e52347bdSJani Nikula rcutorture.gp_cond= [KNL] 4222e52347bdSJani Nikula Use conditional/asynchronous update-side 4223e52347bdSJani Nikula primitives, if available. 4224e52347bdSJani Nikula 4225e52347bdSJani Nikula rcutorture.gp_exp= [KNL] 4226e52347bdSJani Nikula Use expedited update-side primitives, if available. 4227e52347bdSJani Nikula 4228e52347bdSJani Nikula rcutorture.gp_normal= [KNL] 4229e52347bdSJani Nikula Use normal (non-expedited) asynchronous 4230e52347bdSJani Nikula update-side primitives, if available. 4231e52347bdSJani Nikula 4232e52347bdSJani Nikula rcutorture.gp_sync= [KNL] 4233e52347bdSJani Nikula Use normal (non-expedited) synchronous 4234e52347bdSJani Nikula update-side primitives, if available. If all 4235e52347bdSJani Nikula of rcutorture.gp_cond=, rcutorture.gp_exp=, 4236e52347bdSJani Nikula rcutorture.gp_normal=, and rcutorture.gp_sync= 4237e52347bdSJani Nikula are zero, rcutorture acts as if is interpreted 4238e52347bdSJani Nikula they are all non-zero. 4239e52347bdSJani Nikula 4240e52347bdSJani Nikula rcutorture.n_barrier_cbs= [KNL] 4241e52347bdSJani Nikula Set callbacks/threads for rcu_barrier() testing. 4242e52347bdSJani Nikula 4243e52347bdSJani Nikula rcutorture.nfakewriters= [KNL] 4244e52347bdSJani Nikula Set number of concurrent RCU writers. These just 4245e52347bdSJani Nikula stress RCU, they don't participate in the actual 4246e52347bdSJani Nikula test, hence the "fake". 4247e52347bdSJani Nikula 4248e52347bdSJani Nikula rcutorture.nreaders= [KNL] 4249e52347bdSJani Nikula Set number of RCU readers. The value -1 selects 4250e52347bdSJani Nikula N-1, where N is the number of CPUs. A value 4251e52347bdSJani Nikula "n" less than -1 selects N-n-2, where N is again 4252e52347bdSJani Nikula the number of CPUs. For example, -2 selects N 4253e52347bdSJani Nikula (the number of CPUs), -3 selects N+1, and so on. 4254e52347bdSJani Nikula 4255e52347bdSJani Nikula rcutorture.object_debug= [KNL] 4256e52347bdSJani Nikula Enable debug-object double-call_rcu() testing. 4257e52347bdSJani Nikula 4258e52347bdSJani Nikula rcutorture.onoff_holdoff= [KNL] 4259e52347bdSJani Nikula Set time (s) after boot for CPU-hotplug testing. 4260e52347bdSJani Nikula 4261e52347bdSJani Nikula rcutorture.onoff_interval= [KNL] 4262028be12bSPaul E. McKenney Set time (jiffies) between CPU-hotplug operations, 4263028be12bSPaul E. McKenney or zero to disable CPU-hotplug testing. 4264e52347bdSJani Nikula 4265e52347bdSJani Nikula rcutorture.shuffle_interval= [KNL] 4266e52347bdSJani Nikula Set task-shuffle interval (s). Shuffling tasks 4267e52347bdSJani Nikula allows some CPUs to go into dyntick-idle mode 4268e52347bdSJani Nikula during the rcutorture test. 4269e52347bdSJani Nikula 4270e52347bdSJani Nikula rcutorture.shutdown_secs= [KNL] 4271e52347bdSJani Nikula Set time (s) after boot system shutdown. This 4272e52347bdSJani Nikula is useful for hands-off automated testing. 4273e52347bdSJani Nikula 4274e52347bdSJani Nikula rcutorture.stall_cpu= [KNL] 4275e52347bdSJani Nikula Duration of CPU stall (s) to test RCU CPU stall 4276e52347bdSJani Nikula warnings, zero to disable. 4277e52347bdSJani Nikula 427819a8ff95SPaul E. McKenney rcutorture.stall_cpu_block= [KNL] 427919a8ff95SPaul E. McKenney Sleep while stalling if set. This will result 428019a8ff95SPaul E. McKenney in warnings from preemptible RCU in addition 428119a8ff95SPaul E. McKenney to any other stall-related activity. 428219a8ff95SPaul E. McKenney 4283e52347bdSJani Nikula rcutorture.stall_cpu_holdoff= [KNL] 4284e52347bdSJani Nikula Time to wait (s) after boot before inducing stall. 4285e52347bdSJani Nikula 42862b1516e5SPaul E. McKenney rcutorture.stall_cpu_irqsoff= [KNL] 42872b1516e5SPaul E. McKenney Disable interrupts while stalling if set. 42882b1516e5SPaul E. McKenney 428955b2dcf5SPaul E. McKenney rcutorture.stall_gp_kthread= [KNL] 429055b2dcf5SPaul E. McKenney Duration (s) of forced sleep within RCU 429155b2dcf5SPaul E. McKenney grace-period kthread to test RCU CPU stall 429255b2dcf5SPaul E. McKenney warnings, zero to disable. If both stall_cpu 429355b2dcf5SPaul E. McKenney and stall_gp_kthread are specified, the 429455b2dcf5SPaul E. McKenney kthread is starved first, then the CPU. 429555b2dcf5SPaul E. McKenney 4296e52347bdSJani Nikula rcutorture.stat_interval= [KNL] 4297e52347bdSJani Nikula Time (s) between statistics printk()s. 4298e52347bdSJani Nikula 4299e52347bdSJani Nikula rcutorture.stutter= [KNL] 4300e52347bdSJani Nikula Time (s) to stutter testing, for example, specifying 4301e52347bdSJani Nikula five seconds causes the test to run for five seconds, 4302e52347bdSJani Nikula wait for five seconds, and so on. This tests RCU's 4303e52347bdSJani Nikula ability to transition abruptly to and from idle. 4304e52347bdSJani Nikula 4305e52347bdSJani Nikula rcutorture.test_boost= [KNL] 4306e52347bdSJani Nikula Test RCU priority boosting? 0=no, 1=maybe, 2=yes. 4307e52347bdSJani Nikula "Maybe" means test if the RCU implementation 4308e52347bdSJani Nikula under test support RCU priority boosting. 4309e52347bdSJani Nikula 4310e52347bdSJani Nikula rcutorture.test_boost_duration= [KNL] 4311e52347bdSJani Nikula Duration (s) of each individual boost test. 4312e52347bdSJani Nikula 4313e52347bdSJani Nikula rcutorture.test_boost_interval= [KNL] 4314e52347bdSJani Nikula Interval (s) between each boost test. 4315e52347bdSJani Nikula 4316e52347bdSJani Nikula rcutorture.test_no_idle_hz= [KNL] 4317e52347bdSJani Nikula Test RCU's dyntick-idle handling. See also the 4318e52347bdSJani Nikula rcutorture.shuffle_interval parameter. 4319e52347bdSJani Nikula 4320e52347bdSJani Nikula rcutorture.torture_type= [KNL] 4321e52347bdSJani Nikula Specify the RCU implementation to test. 4322e52347bdSJani Nikula 4323e52347bdSJani Nikula rcutorture.verbose= [KNL] 4324e52347bdSJani Nikula Enable additional printk() statements. 4325e52347bdSJani Nikula 4326cdc694b2SPaul E. McKenney rcupdate.rcu_cpu_stall_ftrace_dump= [KNL] 4327cdc694b2SPaul E. McKenney Dump ftrace buffer after reporting RCU CPU 4328cdc694b2SPaul E. McKenney stall warning. 4329cdc694b2SPaul E. McKenney 4330e52347bdSJani Nikula rcupdate.rcu_cpu_stall_suppress= [KNL] 4331e52347bdSJani Nikula Suppress RCU CPU stall warning messages. 4332e52347bdSJani Nikula 433358c53360SPaul E. McKenney rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL] 433458c53360SPaul E. McKenney Suppress RCU CPU stall warning messages and 433558c53360SPaul E. McKenney rcutorture writer stall warnings that occur 433658c53360SPaul E. McKenney during early boot, that is, during the time 433758c53360SPaul E. McKenney before the init task is spawned. 433858c53360SPaul E. McKenney 4339e52347bdSJani Nikula rcupdate.rcu_cpu_stall_timeout= [KNL] 4340e52347bdSJani Nikula Set timeout for RCU CPU stall warning messages. 4341e52347bdSJani Nikula 4342e52347bdSJani Nikula rcupdate.rcu_expedited= [KNL] 4343e52347bdSJani Nikula Use expedited grace-period primitives, for 4344e52347bdSJani Nikula example, synchronize_rcu_expedited() instead 4345e52347bdSJani Nikula of synchronize_rcu(). This reduces latency, 4346e52347bdSJani Nikula but can increase CPU utilization, degrade 4347e52347bdSJani Nikula real-time latency, and degrade energy efficiency. 4348e52347bdSJani Nikula No effect on CONFIG_TINY_RCU kernels. 4349e52347bdSJani Nikula 4350e52347bdSJani Nikula rcupdate.rcu_normal= [KNL] 4351e52347bdSJani Nikula Use only normal grace-period primitives, 4352e52347bdSJani Nikula for example, synchronize_rcu() instead of 4353e52347bdSJani Nikula synchronize_rcu_expedited(). This improves 4354e52347bdSJani Nikula real-time latency, CPU utilization, and 4355e52347bdSJani Nikula energy efficiency, but can expose users to 4356e52347bdSJani Nikula increased grace-period latency. This parameter 4357e52347bdSJani Nikula overrides rcupdate.rcu_expedited. No effect on 4358e52347bdSJani Nikula CONFIG_TINY_RCU kernels. 4359e52347bdSJani Nikula 4360e52347bdSJani Nikula rcupdate.rcu_normal_after_boot= [KNL] 4361e52347bdSJani Nikula Once boot has completed (that is, after 4362e52347bdSJani Nikula rcu_end_inkernel_boot() has been invoked), use 4363e52347bdSJani Nikula only normal grace-period primitives. No effect 4364e52347bdSJani Nikula on CONFIG_TINY_RCU kernels. 4365e52347bdSJani Nikula 4366b0afa0f0SPaul E. McKenney rcupdate.rcu_task_ipi_delay= [KNL] 4367b0afa0f0SPaul E. McKenney Set time in jiffies during which RCU tasks will 4368b0afa0f0SPaul E. McKenney avoid sending IPIs, starting with the beginning 4369b0afa0f0SPaul E. McKenney of a given grace period. Setting a large 4370b0afa0f0SPaul E. McKenney number avoids disturbing real-time workloads, 4371b0afa0f0SPaul E. McKenney but lengthens grace periods. 4372b0afa0f0SPaul E. McKenney 4373e52347bdSJani Nikula rcupdate.rcu_task_stall_timeout= [KNL] 4374e52347bdSJani Nikula Set timeout in jiffies for RCU task stall warning 4375e52347bdSJani Nikula messages. Disable with a value less than or equal 4376e52347bdSJani Nikula to zero. 4377e52347bdSJani Nikula 4378e52347bdSJani Nikula rcupdate.rcu_self_test= [KNL] 4379e52347bdSJani Nikula Run the RCU early boot self tests 4380e52347bdSJani Nikula 4381e52347bdSJani Nikula rdinit= [KNL] 4382e52347bdSJani Nikula Format: <full_path> 4383e52347bdSJani Nikula Run specified binary instead of /init from the ramdisk, 4384e52347bdSJani Nikula used for early userspace startup. See initrd. 4385e52347bdSJani Nikula 4386c49a0a80STom Lendacky rdrand= [X86] 4387c49a0a80STom Lendacky force - Override the decision by the kernel to hide the 4388c49a0a80STom Lendacky advertisement of RDRAND support (this affects 4389c49a0a80STom Lendacky certain AMD processors because of buggy BIOS 4390c49a0a80STom Lendacky support, specifically around the suspend/resume 4391c49a0a80STom Lendacky path). 4392c49a0a80STom Lendacky 43931d9807fcSTony Luck rdt= [HW,X86,RDT] 43941d9807fcSTony Luck Turn on/off individual RDT features. List is: 439531516de3SFenghua Yu cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp, 439631516de3SFenghua Yu mba. 43971d9807fcSTony Luck E.g. to turn on cmt and turn off mba use: 43981d9807fcSTony Luck rdt=cmt,!mba 43991d9807fcSTony Luck 4400e52347bdSJani Nikula reboot= [KNL] 4401e52347bdSJani Nikula Format (x86 or x86_64): 4402e52347bdSJani Nikula [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \ 4403e52347bdSJani Nikula [[,]s[mp]#### \ 4404e52347bdSJani Nikula [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ 4405e52347bdSJani Nikula [[,]f[orce] 4406b287a25aSAaro Koskinen Where reboot_mode is one of warm (soft) or cold (hard) or gpio 4407b287a25aSAaro Koskinen (prefix with 'panic_' to set mode for panic 4408b287a25aSAaro Koskinen reboot only), 4409e52347bdSJani Nikula reboot_type is one of bios, acpi, kbd, triple, efi, or pci, 4410e52347bdSJani Nikula reboot_force is either force or not specified, 4411e52347bdSJani Nikula reboot_cpu is s[mp]#### with #### being the processor 4412e52347bdSJani Nikula to be used for rebooting. 4413e52347bdSJani Nikula 4414e52347bdSJani Nikula relax_domain_level= 4415e52347bdSJani Nikula [KNL, SMP] Set scheduler's default relax_domain_level. 4416da82c92fSMauro Carvalho Chehab See Documentation/admin-guide/cgroup-v1/cpusets.rst. 4417e52347bdSJani Nikula 4418ffd2e8dfSBjorn Helgaas reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory 4419ffd2e8dfSBjorn Helgaas Format: <base1>,<size1>[,<base2>,<size2>,...] 4420ffd2e8dfSBjorn Helgaas Reserve I/O ports or memory so the kernel won't use 4421ffd2e8dfSBjorn Helgaas them. If <base> is less than 0x10000, the region 4422ffd2e8dfSBjorn Helgaas is assumed to be I/O ports; otherwise it is memory. 4423e52347bdSJani Nikula 4424e52347bdSJani Nikula reservetop= [X86-32] 4425e52347bdSJani Nikula Format: nn[KMG] 4426e52347bdSJani Nikula Reserves a hole at the top of the kernel virtual 4427e52347bdSJani Nikula address space. 4428e52347bdSJani Nikula 4429e52347bdSJani Nikula reservelow= [X86] 4430e52347bdSJani Nikula Format: nn[K] 4431e52347bdSJani Nikula Set the amount of memory to reserve for BIOS at 4432e52347bdSJani Nikula the bottom of the address space. 4433e52347bdSJani Nikula 4434e52347bdSJani Nikula reset_devices [KNL] Force drivers to reset the underlying device 4435e52347bdSJani Nikula during initialization. 4436e52347bdSJani Nikula 4437e52347bdSJani Nikula resume= [SWSUSP] 4438e52347bdSJani Nikula Specify the partition device for software suspend 4439e52347bdSJani Nikula Format: 4440e52347bdSJani Nikula {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>} 4441e52347bdSJani Nikula 4442e52347bdSJani Nikula resume_offset= [SWSUSP] 4443e52347bdSJani Nikula Specify the offset from the beginning of the partition 4444e52347bdSJani Nikula given by "resume=" at which the swap header is located, 4445e52347bdSJani Nikula in <PAGE_SIZE> units (needed only for swap files). 4446151f4e2bSMauro Carvalho Chehab See Documentation/power/swsusp-and-swap-files.rst 4447e52347bdSJani Nikula 4448e52347bdSJani Nikula resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to 4449e52347bdSJani Nikula read the resume files 4450e52347bdSJani Nikula 4451e52347bdSJani Nikula resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up. 4452e52347bdSJani Nikula Useful for devices that are detected asynchronously 4453e52347bdSJani Nikula (e.g. USB and MMC devices). 4454e52347bdSJani Nikula 4455e52347bdSJani Nikula hibernate= [HIBERNATION] 4456e52347bdSJani Nikula noresume Don't check if there's a hibernation image 4457e52347bdSJani Nikula present during boot. 4458e52347bdSJani Nikula nocompress Don't compress/decompress hibernation images. 4459e52347bdSJani Nikula no Disable hibernation and resume. 4460e52347bdSJani Nikula protect_image Turn on image protection during restoration 4461e52347bdSJani Nikula (that will set all pages holding image data 4462e52347bdSJani Nikula during restoration read-only). 4463e52347bdSJani Nikula 4464e52347bdSJani Nikula retain_initrd [RAM] Keep initrd memory after extraction 4465e52347bdSJani Nikula 4466e52347bdSJani Nikula rfkill.default_state= 4467e52347bdSJani Nikula 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, 4468e52347bdSJani Nikula etc. communication is blocked by default. 4469e52347bdSJani Nikula 1 Unblocked. 4470e52347bdSJani Nikula 4471e52347bdSJani Nikula rfkill.master_switch_mode= 4472e52347bdSJani Nikula 0 The "airplane mode" button does nothing. 4473e52347bdSJani Nikula 1 The "airplane mode" button toggles between everything 4474e52347bdSJani Nikula blocked and the previous configuration. 4475e52347bdSJani Nikula 2 The "airplane mode" button toggles between everything 4476e52347bdSJani Nikula blocked and everything unblocked. 4477e52347bdSJani Nikula 4478e52347bdSJani Nikula rhash_entries= [KNL,NET] 4479e52347bdSJani Nikula Set number of hash buckets for route cache 4480e52347bdSJani Nikula 4481e16fd002SGrzegorz Andrejczuk ring3mwait=disable 4482e16fd002SGrzegorz Andrejczuk [KNL] Disable ring 3 MONITOR/MWAIT feature on supported 4483e16fd002SGrzegorz Andrejczuk CPUs. 4484e16fd002SGrzegorz Andrejczuk 4485e52347bdSJani Nikula ro [KNL] Mount root device read-only on boot 4486e52347bdSJani Nikula 4487e52347bdSJani Nikula rodata= [KNL] 4488e52347bdSJani Nikula on Mark read-only kernel memory as read-only (default). 4489e52347bdSJani Nikula off Leave read-only kernel memory writable for debugging. 4490e52347bdSJani Nikula 4491e52347bdSJani Nikula rockchip.usb_uart 4492e52347bdSJani Nikula Enable the uart passthrough on the designated usb port 4493e52347bdSJani Nikula on Rockchip SoCs. When active, the signals of the 4494e52347bdSJani Nikula debug-uart get routed to the D+ and D- pins of the usb 4495e52347bdSJani Nikula port and the regular usb controller gets disabled. 4496e52347bdSJani Nikula 4497e52347bdSJani Nikula root= [KNL] Root filesystem 4498e52347bdSJani Nikula See name_to_dev_t comment in init/do_mounts.c. 4499e52347bdSJani Nikula 4500e52347bdSJani Nikula rootdelay= [KNL] Delay (in seconds) to pause before attempting to 4501e52347bdSJani Nikula mount the root filesystem 4502e52347bdSJani Nikula 4503e52347bdSJani Nikula rootflags= [KNL] Set root filesystem mount option string 4504e52347bdSJani Nikula 4505e52347bdSJani Nikula rootfstype= [KNL] Set root filesystem type 4506e52347bdSJani Nikula 4507e52347bdSJani Nikula rootwait [KNL] Wait (indefinitely) for root device to show up. 4508e52347bdSJani Nikula Useful for devices that are detected asynchronously 4509e52347bdSJani Nikula (e.g. USB and MMC devices). 4510e52347bdSJani Nikula 4511e52347bdSJani Nikula rproc_mem=nn[KMG][@address] 4512e52347bdSJani Nikula [KNL,ARM,CMA] Remoteproc physical memory block. 4513e52347bdSJani Nikula Memory area to be used by remote processor image, 4514e52347bdSJani Nikula managed by CMA. 4515e52347bdSJani Nikula 4516e52347bdSJani Nikula rw [KNL] Mount root device read-write on boot 4517e52347bdSJani Nikula 4518e52347bdSJani Nikula S [KNL] Run init in single mode 4519e52347bdSJani Nikula 4520e52347bdSJani Nikula s390_iommu= [HW,S390] 4521e52347bdSJani Nikula Set s390 IOTLB flushing mode 4522e52347bdSJani Nikula strict 4523e52347bdSJani Nikula With strict flushing every unmap operation will result in 4524e52347bdSJani Nikula an IOTLB flush. Default is lazy flushing before reuse, 4525e52347bdSJani Nikula which is faster. 4526e52347bdSJani Nikula 4527e52347bdSJani Nikula sa1100ir [NET] 4528e52347bdSJani Nikula See drivers/net/irda/sa1100_ir.c. 4529e52347bdSJani Nikula 4530e52347bdSJani Nikula sbni= [NET] Granch SBNI12 leased line adapter 4531e52347bdSJani Nikula 4532e52347bdSJani Nikula sched_debug [KNL] Enables verbose scheduler debug messages. 4533e52347bdSJani Nikula 4534e52347bdSJani Nikula schedstats= [KNL,X86] Enable or disable scheduled statistics. 4535e52347bdSJani Nikula Allowed values are enable and disable. This feature 4536e52347bdSJani Nikula incurs a small amount of overhead in the scheduler 4537e52347bdSJani Nikula but is useful for debugging and performance tuning. 4538e52347bdSJani Nikula 453905289b90SThara Gopinath sched_thermal_decay_shift= 454005289b90SThara Gopinath [KNL, SMP] Set a decay shift for scheduler thermal 454105289b90SThara Gopinath pressure signal. Thermal pressure signal follows the 454205289b90SThara Gopinath default decay period of other scheduler pelt 454305289b90SThara Gopinath signals(usually 32 ms but configurable). Setting 454405289b90SThara Gopinath sched_thermal_decay_shift will left shift the decay 454505289b90SThara Gopinath period for the thermal pressure signal by the shift 454605289b90SThara Gopinath value. 454705289b90SThara Gopinath i.e. with the default pelt decay period of 32 ms 454805289b90SThara Gopinath sched_thermal_decay_shift thermal pressure decay pr 454905289b90SThara Gopinath 1 64 ms 455005289b90SThara Gopinath 2 128 ms 455105289b90SThara Gopinath and so on. 455205289b90SThara Gopinath Format: integer between 0 and 10 455305289b90SThara Gopinath Default is 0. 455405289b90SThara Gopinath 4555e52347bdSJani Nikula skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate 4556e52347bdSJani Nikula xtime_lock contention on larger systems, and/or RCU lock 4557e52347bdSJani Nikula contention on all systems with CONFIG_MAXSMP set. 4558e52347bdSJani Nikula Format: { "0" | "1" } 4559e52347bdSJani Nikula 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1" 4560e52347bdSJani Nikula 1 -- enable. 4561e52347bdSJani Nikula Note: increases power consumption, thus should only be 4562e52347bdSJani Nikula enabled if running jitter sensitive (HPC/RT) workloads. 4563e52347bdSJani Nikula 456489a9684eSKees Cook security= [SECURITY] Choose a legacy "major" security module to 456589a9684eSKees Cook enable at boot. This has been deprecated by the 456689a9684eSKees Cook "lsm=" parameter. 4567e52347bdSJani Nikula 4568e52347bdSJani Nikula selinux= [SELINUX] Disable or enable SELinux at boot time. 4569e52347bdSJani Nikula Format: { "0" | "1" } 4570e52347bdSJani Nikula See security/selinux/Kconfig help text. 4571e52347bdSJani Nikula 0 -- disable. 4572e52347bdSJani Nikula 1 -- enable. 4573d41415ebSStephen Smalley Default value is 1. 4574e52347bdSJani Nikula 4575e52347bdSJani Nikula apparmor= [APPARMOR] Disable or enable AppArmor at boot time 4576e52347bdSJani Nikula Format: { "0" | "1" } 4577e52347bdSJani Nikula See security/apparmor/Kconfig help text 4578e52347bdSJani Nikula 0 -- disable. 4579e52347bdSJani Nikula 1 -- enable. 4580e52347bdSJani Nikula Default value is set via kernel config option. 4581e52347bdSJani Nikula 4582e52347bdSJani Nikula serialnumber [BUGS=X86-32] 4583e52347bdSJani Nikula 4584e52347bdSJani Nikula shapers= [NET] 4585e52347bdSJani Nikula Maximal number of shapers. 4586e52347bdSJani Nikula 4587e52347bdSJani Nikula simeth= [IA-64] 4588e52347bdSJani Nikula simscsi= 4589e52347bdSJani Nikula 4590e52347bdSJani Nikula slram= [HW,MTD] 4591e52347bdSJani Nikula 4592e52347bdSJani Nikula slab_nomerge [MM] 4593e52347bdSJani Nikula Disable merging of slabs with similar size. May be 4594e52347bdSJani Nikula necessary if there is some reason to distinguish 45957660a6fdSKees Cook allocs to different slabs, especially in hardened 45967660a6fdSKees Cook environments where the risk of heap overflows and 45977660a6fdSKees Cook layout control by attackers can usually be 45987660a6fdSKees Cook frustrated by disabling merging. This will reduce 45997660a6fdSKees Cook most of the exposure of a heap attack to a single 46007660a6fdSKees Cook cache (risks via metadata attacks are mostly 46017660a6fdSKees Cook unchanged). Debug options disable merging on their 46027660a6fdSKees Cook own. 4603ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 4604e52347bdSJani Nikula 4605e52347bdSJani Nikula slab_max_order= [MM, SLAB] 4606e52347bdSJani Nikula Determines the maximum allowed order for slabs. 4607e52347bdSJani Nikula A high setting may cause OOMs due to memory 4608e52347bdSJani Nikula fragmentation. Defaults to 1 for systems with 4609e52347bdSJani Nikula more than 32MB of RAM, 0 otherwise. 4610e52347bdSJani Nikula 4611e52347bdSJani Nikula slub_debug[=options[,slabs]] [MM, SLUB] 4612e52347bdSJani Nikula Enabling slub_debug allows one to determine the 4613e52347bdSJani Nikula culprit if slab objects become corrupted. Enabling 4614e52347bdSJani Nikula slub_debug can create guard zones around objects and 4615e52347bdSJani Nikula may poison objects when not in use. Also tracks the 4616e52347bdSJani Nikula last alloc / free. For more information see 4617ad56b738SMike Rapoport Documentation/vm/slub.rst. 4618e52347bdSJani Nikula 46191663f26dSTejun Heo slub_memcg_sysfs= [MM, SLUB] 46201663f26dSTejun Heo Determines whether to enable sysfs directories for 46211663f26dSTejun Heo memory cgroup sub-caches. 1 to enable, 0 to disable. 46221663f26dSTejun Heo The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON. 46231663f26dSTejun Heo Enabling this can lead to a very high number of debug 46241663f26dSTejun Heo directories and files being created under 46251663f26dSTejun Heo /sys/kernel/slub. 46261663f26dSTejun Heo 4627e52347bdSJani Nikula slub_max_order= [MM, SLUB] 4628e52347bdSJani Nikula Determines the maximum allowed order for slabs. 4629e52347bdSJani Nikula A high setting may cause OOMs due to memory 4630e52347bdSJani Nikula fragmentation. For more information see 4631ad56b738SMike Rapoport Documentation/vm/slub.rst. 4632e52347bdSJani Nikula 4633e52347bdSJani Nikula slub_min_objects= [MM, SLUB] 4634e52347bdSJani Nikula The minimum number of objects per slab. SLUB will 4635e52347bdSJani Nikula increase the slab order up to slub_max_order to 4636e52347bdSJani Nikula generate a sufficiently large slab able to contain 4637e52347bdSJani Nikula the number of objects indicated. The higher the number 4638e52347bdSJani Nikula of objects the smaller the overhead of tracking slabs 4639e52347bdSJani Nikula and the less frequently locks need to be acquired. 4640ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 4641e52347bdSJani Nikula 4642e52347bdSJani Nikula slub_min_order= [MM, SLUB] 4643e52347bdSJani Nikula Determines the minimum page order for slabs. Must be 4644e52347bdSJani Nikula lower than slub_max_order. 4645ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 4646e52347bdSJani Nikula 4647e52347bdSJani Nikula slub_nomerge [MM, SLUB] 4648e52347bdSJani Nikula Same with slab_nomerge. This is supported for legacy. 4649e52347bdSJani Nikula See slab_nomerge for more information. 4650e52347bdSJani Nikula 4651e52347bdSJani Nikula smart2= [HW] 4652e52347bdSJani Nikula Format: <io1>[,<io2>[,...,<io8>]] 4653e52347bdSJani Nikula 4654e52347bdSJani Nikula smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 4655e52347bdSJani Nikula smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 4656e52347bdSJani Nikula smsc-ircc2.ircc_sir= [HW] SIR base I/O port 4657e52347bdSJani Nikula smsc-ircc2.ircc_fir= [HW] FIR base I/O port 4658e52347bdSJani Nikula smsc-ircc2.ircc_irq= [HW] IRQ line 4659e52347bdSJani Nikula smsc-ircc2.ircc_dma= [HW] DMA channel 4660e52347bdSJani Nikula smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 4661e52347bdSJani Nikula 0: Toshiba Satellite 1800 (GP data pin select) 4662e52347bdSJani Nikula 1: Fast pin select (default) 4663e52347bdSJani Nikula 2: ATC IRMode 4664e52347bdSJani Nikula 4665e52347bdSJani Nikula smt [KNL,S390] Set the maximum number of threads (logical 4666e52347bdSJani Nikula CPUs) to use per physical CPU on systems capable of 4667e52347bdSJani Nikula symmetric multithreading (SMT). Will be capped to the 4668e52347bdSJani Nikula actual hardware limit. 4669e52347bdSJani Nikula Format: <integer> 4670e52347bdSJani Nikula Default: -1 (no limit) 4671e52347bdSJani Nikula 4672e52347bdSJani Nikula softlockup_panic= 4673e52347bdSJani Nikula [KNL] Should the soft-lockup detector generate panics. 4674f117955aSGuilherme G. Piccoli Format: 0 | 1 4675e52347bdSJani Nikula 4676f117955aSGuilherme G. Piccoli A value of 1 instructs the soft-lockup detector 46770a07bef6SGuilherme G. Piccoli to panic the machine when a soft-lockup occurs. It is 46780a07bef6SGuilherme G. Piccoli also controlled by the kernel.softlockup_panic sysctl 46790a07bef6SGuilherme G. Piccoli and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the 46800a07bef6SGuilherme G. Piccoli respective build-time switch to that functionality. 46813ce62385SBorislav Petkov 4682e52347bdSJani Nikula softlockup_all_cpu_backtrace= 4683e52347bdSJani Nikula [KNL] Should the soft-lockup detector generate 4684e52347bdSJani Nikula backtraces on all cpus. 4685f117955aSGuilherme G. Piccoli Format: 0 | 1 4686e52347bdSJani Nikula 4687e52347bdSJani Nikula sonypi.*= [HW] Sony Programmable I/O Control Device driver 46889e1cbedeSMauro Carvalho Chehab See Documentation/admin-guide/laptops/sonypi.rst 4689e52347bdSJani Nikula 4690da285121SDavid Woodhouse spectre_v2= [X86] Control mitigation of Spectre variant 2 4691da285121SDavid Woodhouse (indirect branch speculation) vulnerability. 4692fa1202efSThomas Gleixner The default operation protects the kernel from 4693fa1202efSThomas Gleixner user space attacks. 4694da285121SDavid Woodhouse 4695fa1202efSThomas Gleixner on - unconditionally enable, implies 4696fa1202efSThomas Gleixner spectre_v2_user=on 4697fa1202efSThomas Gleixner off - unconditionally disable, implies 4698fa1202efSThomas Gleixner spectre_v2_user=off 4699da285121SDavid Woodhouse auto - kernel detects whether your CPU model is 4700da285121SDavid Woodhouse vulnerable 4701da285121SDavid Woodhouse 4702da285121SDavid Woodhouse Selecting 'on' will, and 'auto' may, choose a 4703da285121SDavid Woodhouse mitigation method at run time according to the 4704da285121SDavid Woodhouse CPU, the available microcode, the setting of the 4705da285121SDavid Woodhouse CONFIG_RETPOLINE configuration option, and the 4706da285121SDavid Woodhouse compiler with which the kernel was built. 4707da285121SDavid Woodhouse 4708fa1202efSThomas Gleixner Selecting 'on' will also enable the mitigation 4709fa1202efSThomas Gleixner against user space to user space task attacks. 4710fa1202efSThomas Gleixner 4711fa1202efSThomas Gleixner Selecting 'off' will disable both the kernel and 4712fa1202efSThomas Gleixner the user space protections. 4713fa1202efSThomas Gleixner 4714da285121SDavid Woodhouse Specific mitigations can also be selected manually: 4715da285121SDavid Woodhouse 4716da285121SDavid Woodhouse retpoline - replace indirect branches 4717da285121SDavid Woodhouse retpoline,generic - google's original retpoline 4718da285121SDavid Woodhouse retpoline,amd - AMD-specific minimal thunk 4719da285121SDavid Woodhouse 4720da285121SDavid Woodhouse Not specifying this option is equivalent to 4721da285121SDavid Woodhouse spectre_v2=auto. 4722da285121SDavid Woodhouse 4723fa1202efSThomas Gleixner spectre_v2_user= 4724fa1202efSThomas Gleixner [X86] Control mitigation of Spectre variant 2 4725fa1202efSThomas Gleixner (indirect branch speculation) vulnerability between 4726fa1202efSThomas Gleixner user space tasks 4727fa1202efSThomas Gleixner 4728fa1202efSThomas Gleixner on - Unconditionally enable mitigations. Is 4729fa1202efSThomas Gleixner enforced by spectre_v2=on 4730fa1202efSThomas Gleixner 4731fa1202efSThomas Gleixner off - Unconditionally disable mitigations. Is 4732fa1202efSThomas Gleixner enforced by spectre_v2=off 4733fa1202efSThomas Gleixner 47347cc765a6SThomas Gleixner prctl - Indirect branch speculation is enabled, 47357cc765a6SThomas Gleixner but mitigation can be enabled via prctl 47367cc765a6SThomas Gleixner per thread. The mitigation control state 47377cc765a6SThomas Gleixner is inherited on fork. 47387cc765a6SThomas Gleixner 473955a97402SThomas Gleixner prctl,ibpb 474055a97402SThomas Gleixner - Like "prctl" above, but only STIBP is 474155a97402SThomas Gleixner controlled per thread. IBPB is issued 474255a97402SThomas Gleixner always when switching between different user 474355a97402SThomas Gleixner space processes. 474455a97402SThomas Gleixner 47456b3e64c2SThomas Gleixner seccomp 47466b3e64c2SThomas Gleixner - Same as "prctl" above, but all seccomp 47476b3e64c2SThomas Gleixner threads will enable the mitigation unless 47486b3e64c2SThomas Gleixner they explicitly opt out. 47496b3e64c2SThomas Gleixner 475055a97402SThomas Gleixner seccomp,ibpb 475155a97402SThomas Gleixner - Like "seccomp" above, but only STIBP is 475255a97402SThomas Gleixner controlled per thread. IBPB is issued 475355a97402SThomas Gleixner always when switching between different 475455a97402SThomas Gleixner user space processes. 475555a97402SThomas Gleixner 4756fa1202efSThomas Gleixner auto - Kernel selects the mitigation depending on 4757fa1202efSThomas Gleixner the available CPU features and vulnerability. 47586b3e64c2SThomas Gleixner 47596b3e64c2SThomas Gleixner Default mitigation: 47606b3e64c2SThomas Gleixner If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl" 4761fa1202efSThomas Gleixner 4762fa1202efSThomas Gleixner Not specifying this option is equivalent to 4763fa1202efSThomas Gleixner spectre_v2_user=auto. 4764fa1202efSThomas Gleixner 476524f7fc83SKonrad Rzeszutek Wilk spec_store_bypass_disable= 476624f7fc83SKonrad Rzeszutek Wilk [HW] Control Speculative Store Bypass (SSB) Disable mitigation 476724f7fc83SKonrad Rzeszutek Wilk (Speculative Store Bypass vulnerability) 476824f7fc83SKonrad Rzeszutek Wilk 476924f7fc83SKonrad Rzeszutek Wilk Certain CPUs are vulnerable to an exploit against a 477024f7fc83SKonrad Rzeszutek Wilk a common industry wide performance optimization known 477124f7fc83SKonrad Rzeszutek Wilk as "Speculative Store Bypass" in which recent stores 477224f7fc83SKonrad Rzeszutek Wilk to the same memory location may not be observed by 477324f7fc83SKonrad Rzeszutek Wilk later loads during speculative execution. The idea 477424f7fc83SKonrad Rzeszutek Wilk is that such stores are unlikely and that they can 477524f7fc83SKonrad Rzeszutek Wilk be detected prior to instruction retirement at the 477624f7fc83SKonrad Rzeszutek Wilk end of a particular speculation execution window. 477724f7fc83SKonrad Rzeszutek Wilk 477824f7fc83SKonrad Rzeszutek Wilk In vulnerable processors, the speculatively forwarded 477924f7fc83SKonrad Rzeszutek Wilk store can be used in a cache side channel attack, for 478024f7fc83SKonrad Rzeszutek Wilk example to read memory to which the attacker does not 478124f7fc83SKonrad Rzeszutek Wilk directly have access (e.g. inside sandboxed code). 478224f7fc83SKonrad Rzeszutek Wilk 478324f7fc83SKonrad Rzeszutek Wilk This parameter controls whether the Speculative Store 478424f7fc83SKonrad Rzeszutek Wilk Bypass optimization is used. 478524f7fc83SKonrad Rzeszutek Wilk 47866b4c1360SMichael Ellerman On x86 the options are: 47876b4c1360SMichael Ellerman 478824f7fc83SKonrad Rzeszutek Wilk on - Unconditionally disable Speculative Store Bypass 478924f7fc83SKonrad Rzeszutek Wilk off - Unconditionally enable Speculative Store Bypass 479024f7fc83SKonrad Rzeszutek Wilk auto - Kernel detects whether the CPU model contains an 479124f7fc83SKonrad Rzeszutek Wilk implementation of Speculative Store Bypass and 4792f21b53b2SKees Cook picks the most appropriate mitigation. If the 4793f21b53b2SKees Cook CPU is not vulnerable, "off" is selected. If the 4794f21b53b2SKees Cook CPU is vulnerable the default mitigation is 4795f21b53b2SKees Cook architecture and Kconfig dependent. See below. 4796a73ec77eSThomas Gleixner prctl - Control Speculative Store Bypass per thread 4797a73ec77eSThomas Gleixner via prctl. Speculative Store Bypass is enabled 4798a73ec77eSThomas Gleixner for a process by default. The state of the control 4799a73ec77eSThomas Gleixner is inherited on fork. 4800f21b53b2SKees Cook seccomp - Same as "prctl" above, but all seccomp threads 4801f21b53b2SKees Cook will disable SSB unless they explicitly opt out. 480224f7fc83SKonrad Rzeszutek Wilk 4803f21b53b2SKees Cook Default mitigations: 4804f21b53b2SKees Cook X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl" 4805f21b53b2SKees Cook 48066b4c1360SMichael Ellerman On powerpc the options are: 48076b4c1360SMichael Ellerman 48086b4c1360SMichael Ellerman on,auto - On Power8 and Power9 insert a store-forwarding 48096b4c1360SMichael Ellerman barrier on kernel entry and exit. On Power7 48106b4c1360SMichael Ellerman perform a software flush on kernel entry and 48116b4c1360SMichael Ellerman exit. 48126b4c1360SMichael Ellerman off - No action. 48136b4c1360SMichael Ellerman 48146b4c1360SMichael Ellerman Not specifying this option is equivalent to 48156b4c1360SMichael Ellerman spec_store_bypass_disable=auto. 48166b4c1360SMichael Ellerman 4817e52347bdSJani Nikula spia_io_base= [HW,MTD] 4818e52347bdSJani Nikula spia_fio_base= 4819e52347bdSJani Nikula spia_pedr= 4820e52347bdSJani Nikula spia_peddr= 4821e52347bdSJani Nikula 48226650cdd9SPeter Zijlstra (Intel) split_lock_detect= 48236650cdd9SPeter Zijlstra (Intel) [X86] Enable split lock detection 48246650cdd9SPeter Zijlstra (Intel) 48256650cdd9SPeter Zijlstra (Intel) When enabled (and if hardware support is present), atomic 48266650cdd9SPeter Zijlstra (Intel) instructions that access data across cache line 48276650cdd9SPeter Zijlstra (Intel) boundaries will result in an alignment check exception. 48286650cdd9SPeter Zijlstra (Intel) 48296650cdd9SPeter Zijlstra (Intel) off - not enabled 48306650cdd9SPeter Zijlstra (Intel) 48316650cdd9SPeter Zijlstra (Intel) warn - the kernel will emit rate limited warnings 48326650cdd9SPeter Zijlstra (Intel) about applications triggering the #AC 48336650cdd9SPeter Zijlstra (Intel) exception. This mode is the default on CPUs 48346650cdd9SPeter Zijlstra (Intel) that supports split lock detection. 48356650cdd9SPeter Zijlstra (Intel) 48366650cdd9SPeter Zijlstra (Intel) fatal - the kernel will send SIGBUS to applications 48376650cdd9SPeter Zijlstra (Intel) that trigger the #AC exception. 48386650cdd9SPeter Zijlstra (Intel) 48396650cdd9SPeter Zijlstra (Intel) If an #AC exception is hit in the kernel or in 48406650cdd9SPeter Zijlstra (Intel) firmware (i.e. not while executing in user mode) 48416650cdd9SPeter Zijlstra (Intel) the kernel will oops in either "warn" or "fatal" 48426650cdd9SPeter Zijlstra (Intel) mode. 48436650cdd9SPeter Zijlstra (Intel) 48447e5b3c26SMark Gross srbds= [X86,INTEL] 48457e5b3c26SMark Gross Control the Special Register Buffer Data Sampling 48467e5b3c26SMark Gross (SRBDS) mitigation. 48477e5b3c26SMark Gross 48487e5b3c26SMark Gross Certain CPUs are vulnerable to an MDS-like 48497e5b3c26SMark Gross exploit which can leak bits from the random 48507e5b3c26SMark Gross number generator. 48517e5b3c26SMark Gross 48527e5b3c26SMark Gross By default, this issue is mitigated by 48537e5b3c26SMark Gross microcode. However, the microcode fix can cause 48547e5b3c26SMark Gross the RDRAND and RDSEED instructions to become 48557e5b3c26SMark Gross much slower. Among other effects, this will 48567e5b3c26SMark Gross result in reduced throughput from /dev/urandom. 48577e5b3c26SMark Gross 48587e5b3c26SMark Gross The microcode mitigation can be disabled with 48597e5b3c26SMark Gross the following option: 48607e5b3c26SMark Gross 48617e5b3c26SMark Gross off: Disable mitigation and remove 48627e5b3c26SMark Gross performance impact to RDRAND and RDSEED 48637e5b3c26SMark Gross 4864c350c008SPaul E. McKenney srcutree.counter_wrap_check [KNL] 4865c350c008SPaul E. McKenney Specifies how frequently to check for 4866c350c008SPaul E. McKenney grace-period sequence counter wrap for the 4867c350c008SPaul E. McKenney srcu_data structure's ->srcu_gp_seq_needed field. 4868c350c008SPaul E. McKenney The greater the number of bits set in this kernel 4869c350c008SPaul E. McKenney parameter, the less frequently counter wrap will 4870c350c008SPaul E. McKenney be checked for. Note that the bottom two bits 4871c350c008SPaul E. McKenney are ignored. 4872c350c008SPaul E. McKenney 487322607d66SPaul E. McKenney srcutree.exp_holdoff [KNL] 487422607d66SPaul E. McKenney Specifies how many nanoseconds must elapse 487522607d66SPaul E. McKenney since the end of the last SRCU grace period for 487622607d66SPaul E. McKenney a given srcu_struct until the next normal SRCU 487722607d66SPaul E. McKenney grace period will be considered for automatic 487822607d66SPaul E. McKenney expediting. Set to zero to disable automatic 487922607d66SPaul E. McKenney expediting. 488022607d66SPaul E. McKenney 4881a43ae4dfSMarc Zyngier ssbd= [ARM64,HW] 4882a43ae4dfSMarc Zyngier Speculative Store Bypass Disable control 4883a43ae4dfSMarc Zyngier 4884a43ae4dfSMarc Zyngier On CPUs that are vulnerable to the Speculative 4885a43ae4dfSMarc Zyngier Store Bypass vulnerability and offer a 4886a43ae4dfSMarc Zyngier firmware based mitigation, this parameter 4887a43ae4dfSMarc Zyngier indicates how the mitigation should be used: 4888a43ae4dfSMarc Zyngier 4889a43ae4dfSMarc Zyngier force-on: Unconditionally enable mitigation for 4890a43ae4dfSMarc Zyngier for both kernel and userspace 4891a43ae4dfSMarc Zyngier force-off: Unconditionally disable mitigation for 4892a43ae4dfSMarc Zyngier for both kernel and userspace 4893a43ae4dfSMarc Zyngier kernel: Always enable mitigation in the 4894a43ae4dfSMarc Zyngier kernel, and offer a prctl interface 4895a43ae4dfSMarc Zyngier to allow userspace to register its 4896a43ae4dfSMarc Zyngier interest in being mitigated too. 4897a43ae4dfSMarc Zyngier 48981be7107fSHugh Dickins stack_guard_gap= [MM] 48991be7107fSHugh Dickins override the default stack gap protection. The value 49001be7107fSHugh Dickins is in page units and it defines how many pages prior 49011be7107fSHugh Dickins to (for stacks growing down) resp. after (for stacks 49021be7107fSHugh Dickins growing up) the main stack are reserved for no other 49031be7107fSHugh Dickins mapping. Default value is 256 pages. 49041be7107fSHugh Dickins 4905e52347bdSJani Nikula stacktrace [FTRACE] 4906e52347bdSJani Nikula Enabled the stack tracer on boot up. 4907e52347bdSJani Nikula 4908e52347bdSJani Nikula stacktrace_filter=[function-list] 4909e52347bdSJani Nikula [FTRACE] Limit the functions that the stack tracer 4910e52347bdSJani Nikula will trace at boot up. function-list is a comma separated 4911e52347bdSJani Nikula list of functions. This list can be changed at run 4912e52347bdSJani Nikula time by the stack_trace_filter file in the debugfs 4913e52347bdSJani Nikula tracing directory. Note, this enables stack tracing 4914e52347bdSJani Nikula and the stacktrace above is not needed. 4915e52347bdSJani Nikula 4916e52347bdSJani Nikula sti= [PARISC,HW] 4917e52347bdSJani Nikula Format: <num> 4918e52347bdSJani Nikula Set the STI (builtin display/keyboard on the HP-PARISC 4919e52347bdSJani Nikula machines) console (graphic card) which should be used 4920e52347bdSJani Nikula as the initial boot-console. 4921e52347bdSJani Nikula See also comment in drivers/video/console/sticore.c. 4922e52347bdSJani Nikula 4923e52347bdSJani Nikula sti_font= [HW] 4924e52347bdSJani Nikula See comment in drivers/video/console/sticore.c. 4925e52347bdSJani Nikula 4926e52347bdSJani Nikula stifb= [HW] 4927e52347bdSJani Nikula Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 4928e52347bdSJani Nikula 4929e52347bdSJani Nikula sunrpc.min_resvport= 4930e52347bdSJani Nikula sunrpc.max_resvport= 4931e52347bdSJani Nikula [NFS,SUNRPC] 4932e52347bdSJani Nikula SunRPC servers often require that client requests 4933e52347bdSJani Nikula originate from a privileged port (i.e. a port in the 4934e52347bdSJani Nikula range 0 < portnr < 1024). 4935e52347bdSJani Nikula An administrator who wishes to reserve some of these 4936e52347bdSJani Nikula ports for other uses may adjust the range that the 4937e52347bdSJani Nikula kernel's sunrpc client considers to be privileged 4938e52347bdSJani Nikula using these two parameters to set the minimum and 4939e52347bdSJani Nikula maximum port values. 4940e52347bdSJani Nikula 4941e52347bdSJani Nikula sunrpc.svc_rpc_per_connection_limit= 4942e52347bdSJani Nikula [NFS,SUNRPC] 4943e52347bdSJani Nikula Limit the number of requests that the server will 4944e52347bdSJani Nikula process in parallel from a single connection. 4945e52347bdSJani Nikula The default value is 0 (no limit). 4946e52347bdSJani Nikula 4947e52347bdSJani Nikula sunrpc.pool_mode= 4948e52347bdSJani Nikula [NFS] 4949e52347bdSJani Nikula Control how the NFS server code allocates CPUs to 4950e52347bdSJani Nikula service thread pools. Depending on how many NICs 4951e52347bdSJani Nikula you have and where their interrupts are bound, this 4952e52347bdSJani Nikula option will affect which CPUs will do NFS serving. 4953e52347bdSJani Nikula Note: this parameter cannot be changed while the 4954e52347bdSJani Nikula NFS server is running. 4955e52347bdSJani Nikula 4956e52347bdSJani Nikula auto the server chooses an appropriate mode 4957e52347bdSJani Nikula automatically using heuristics 4958e52347bdSJani Nikula global a single global pool contains all CPUs 4959e52347bdSJani Nikula percpu one pool for each CPU 4960e52347bdSJani Nikula pernode one pool for each NUMA node (equivalent 4961e52347bdSJani Nikula to global on non-NUMA machines) 4962e52347bdSJani Nikula 4963e52347bdSJani Nikula sunrpc.tcp_slot_table_entries= 4964e52347bdSJani Nikula sunrpc.udp_slot_table_entries= 4965e52347bdSJani Nikula [NFS,SUNRPC] 4966e52347bdSJani Nikula Sets the upper limit on the number of simultaneous 4967e52347bdSJani Nikula RPC calls that can be sent from the client to a 4968e52347bdSJani Nikula server. Increasing these values may allow you to 4969e52347bdSJani Nikula improve throughput, but will also increase the 4970e52347bdSJani Nikula amount of memory reserved for use by the client. 4971e52347bdSJani Nikula 4972e52347bdSJani Nikula suspend.pm_test_delay= 4973e52347bdSJani Nikula [SUSPEND] 4974e52347bdSJani Nikula Sets the number of seconds to remain in a suspend test 4975e52347bdSJani Nikula mode before resuming the system (see 4976e52347bdSJani Nikula /sys/power/pm_test). Only available when CONFIG_PM_DEBUG 4977e52347bdSJani Nikula is set. Default value is 5. 4978e52347bdSJani Nikula 49796a9c930bSRam Pai svm= [PPC] 49806a9c930bSRam Pai Format: { on | off | y | n | 1 | 0 } 49816a9c930bSRam Pai This parameter controls use of the Protected 49826a9c930bSRam Pai Execution Facility on pSeries. 49836a9c930bSRam Pai 4984e52347bdSJani Nikula swapaccount=[0|1] 4985e52347bdSJani Nikula [KNL] Enable accounting of swap in memory resource 4986e52347bdSJani Nikula controller if no parameter or 1 is given or disable 4987da82c92fSMauro Carvalho Chehab it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst) 4988e52347bdSJani Nikula 4989e52347bdSJani Nikula swiotlb= [ARM,IA-64,PPC,MIPS,X86] 4990fff5d992SGeert Uytterhoeven Format: { <int> | force | noforce } 4991e52347bdSJani Nikula <int> -- Number of I/O TLB slabs 4992e52347bdSJani Nikula force -- force using of bounce buffers even if they 4993e52347bdSJani Nikula wouldn't be automatically used by the kernel 4994fff5d992SGeert Uytterhoeven noforce -- Never use bounce buffers (for debugging) 4995e52347bdSJani Nikula 4996e52347bdSJani Nikula switches= [HW,M68k] 4997e52347bdSJani Nikula 49983db978d4SVlastimil Babka sysctl.*= [KNL] 49993db978d4SVlastimil Babka Set a sysctl parameter, right before loading the init 50003db978d4SVlastimil Babka process, as if the value was written to the respective 50013db978d4SVlastimil Babka /proc/sys/... file. Both '.' and '/' are recognized as 50023db978d4SVlastimil Babka separators. Unrecognized parameters and invalid values 50033db978d4SVlastimil Babka are reported in the kernel log. Sysctls registered 50043db978d4SVlastimil Babka later by a loaded module cannot be set this way. 50053db978d4SVlastimil Babka Example: sysctl.vm.swappiness=40 50063db978d4SVlastimil Babka 5007e52347bdSJani Nikula sysfs.deprecated=0|1 [KNL] 5008e52347bdSJani Nikula Enable/disable old style sysfs layout for old udev 5009e52347bdSJani Nikula on older distributions. When this option is enabled 5010e52347bdSJani Nikula very new udev will not work anymore. When this option 5011e52347bdSJani Nikula is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) 5012e52347bdSJani Nikula in older udev will not work anymore. 5013e52347bdSJani Nikula Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in 5014e52347bdSJani Nikula the kernel configuration. 5015e52347bdSJani Nikula 5016e52347bdSJani Nikula sysrq_always_enabled 5017e52347bdSJani Nikula [KNL] 5018e52347bdSJani Nikula Ignore sysrq setting - this boot parameter will 5019e52347bdSJani Nikula neutralize any effect of /proc/sys/kernel/sysrq. 5020e52347bdSJani Nikula Useful for debugging. 5021e52347bdSJani Nikula 5022e52347bdSJani Nikula tcpmhash_entries= [KNL,NET] 5023e52347bdSJani Nikula Set the number of tcp_metrics_hash slots. 5024e52347bdSJani Nikula Default value is 8192 or 16384 depending on total 5025e52347bdSJani Nikula ram pages. This is used to specify the TCP metrics 50261cec2cacSMauro Carvalho Chehab cache size. See Documentation/networking/ip-sysctl.rst 5027e52347bdSJani Nikula "tcp_no_metrics_save" section for more details. 5028e52347bdSJani Nikula 5029e52347bdSJani Nikula tdfx= [HW,DRM] 5030e52347bdSJani Nikula 5031e52347bdSJani Nikula test_suspend= [SUSPEND][,N] 5032e52347bdSJani Nikula Specify "mem" (for Suspend-to-RAM) or "standby" (for 5033e52347bdSJani Nikula standby suspend) or "freeze" (for suspend type freeze) 5034e52347bdSJani Nikula as the system sleep state during system startup with 5035e52347bdSJani Nikula the optional capability to repeat N number of times. 5036e52347bdSJani Nikula The system is woken from this state using a 5037e52347bdSJani Nikula wakeup-capable RTC alarm. 5038e52347bdSJani Nikula 5039e52347bdSJani Nikula thash_entries= [KNL,NET] 5040e52347bdSJani Nikula Set number of hash buckets for TCP connection 5041e52347bdSJani Nikula 5042e52347bdSJani Nikula thermal.act= [HW,ACPI] 5043e52347bdSJani Nikula -1: disable all active trip points in all thermal zones 5044e52347bdSJani Nikula <degrees C>: override all lowest active trip points 5045e52347bdSJani Nikula 5046e52347bdSJani Nikula thermal.crt= [HW,ACPI] 5047e52347bdSJani Nikula -1: disable all critical trip points in all thermal zones 5048e52347bdSJani Nikula <degrees C>: override all critical trip points 5049e52347bdSJani Nikula 5050e52347bdSJani Nikula thermal.nocrt= [HW,ACPI] 5051e52347bdSJani Nikula Set to disable actions on ACPI thermal zone 5052e52347bdSJani Nikula critical and hot trip points. 5053e52347bdSJani Nikula 5054e52347bdSJani Nikula thermal.off= [HW,ACPI] 5055e52347bdSJani Nikula 1: disable ACPI thermal control 5056e52347bdSJani Nikula 5057e52347bdSJani Nikula thermal.psv= [HW,ACPI] 5058e52347bdSJani Nikula -1: disable all passive trip points 5059e52347bdSJani Nikula <degrees C>: override all passive trip points to this 5060e52347bdSJani Nikula value 5061e52347bdSJani Nikula 5062e52347bdSJani Nikula thermal.tzp= [HW,ACPI] 5063e52347bdSJani Nikula Specify global default ACPI thermal zone polling rate 5064e52347bdSJani Nikula <deci-seconds>: poll all this frequency 5065e52347bdSJani Nikula 0: no polling (default) 5066e52347bdSJani Nikula 5067e52347bdSJani Nikula threadirqs [KNL] 5068e52347bdSJani Nikula Force threading of all interrupt handlers except those 5069e52347bdSJani Nikula marked explicitly IRQF_NO_THREAD. 5070e52347bdSJani Nikula 5071e52347bdSJani Nikula topology= [S390] 5072e52347bdSJani Nikula Format: {off | on} 5073e52347bdSJani Nikula Specify if the kernel should make use of the cpu 5074e52347bdSJani Nikula topology information if the hardware supports this. 5075e52347bdSJani Nikula The scheduler will make use of this information and 5076e52347bdSJani Nikula e.g. base its process migration decisions on it. 5077e52347bdSJani Nikula Default is on. 5078e52347bdSJani Nikula 5079e52347bdSJani Nikula topology_updates= [KNL, PPC, NUMA] 5080e52347bdSJani Nikula Format: {off} 5081e52347bdSJani Nikula Specify if the kernel should ignore (off) 5082e52347bdSJani Nikula topology updates sent by the hypervisor to this 5083e52347bdSJani Nikula LPAR. 5084e52347bdSJani Nikula 50858171d3e0SPaul E. McKenney torture.disable_onoff_at_boot= [KNL] 50868171d3e0SPaul E. McKenney Prevent the CPU-hotplug component of torturing 50878171d3e0SPaul E. McKenney until after init has spawned. 50888171d3e0SPaul E. McKenney 5089e52347bdSJani Nikula tp720= [HW,PS2] 5090e52347bdSJani Nikula 5091e52347bdSJani Nikula tpm_suspend_pcr=[HW,TPM] 5092e52347bdSJani Nikula Format: integer pcr id 5093e52347bdSJani Nikula Specify that at suspend time, the tpm driver 5094e52347bdSJani Nikula should extend the specified pcr with zeros, 5095e52347bdSJani Nikula as a workaround for some chips which fail to 5096e52347bdSJani Nikula flush the last written pcr on TPM_SaveState. 5097e52347bdSJani Nikula This will guarantee that all the other pcrs 5098e52347bdSJani Nikula are saved. 5099e52347bdSJani Nikula 5100e52347bdSJani Nikula trace_buf_size=nn[KMG] 5101e52347bdSJani Nikula [FTRACE] will set tracing buffer size on each cpu. 5102e52347bdSJani Nikula 5103e52347bdSJani Nikula trace_event=[event-list] 5104e52347bdSJani Nikula [FTRACE] Set and start specified trace events in order 5105e52347bdSJani Nikula to facilitate early boot debugging. The event-list is a 5106e52347bdSJani Nikula comma separated list of trace events to enable. See 51075fb94e9cSMauro Carvalho Chehab also Documentation/trace/events.rst 5108e52347bdSJani Nikula 5109e52347bdSJani Nikula trace_options=[option-list] 5110e52347bdSJani Nikula [FTRACE] Enable or disable tracer options at boot. 5111e52347bdSJani Nikula The option-list is a comma delimited list of options 5112e52347bdSJani Nikula that can be enabled or disabled just as if you were 5113e52347bdSJani Nikula to echo the option name into 5114e52347bdSJani Nikula 5115e52347bdSJani Nikula /sys/kernel/debug/tracing/trace_options 5116e52347bdSJani Nikula 5117e52347bdSJani Nikula For example, to enable stacktrace option (to dump the 5118e52347bdSJani Nikula stack trace of each event), add to the command line: 5119e52347bdSJani Nikula 5120e52347bdSJani Nikula trace_options=stacktrace 5121e52347bdSJani Nikula 51225fb94e9cSMauro Carvalho Chehab See also Documentation/trace/ftrace.rst "trace options" 5123e52347bdSJani Nikula section. 5124e52347bdSJani Nikula 5125e52347bdSJani Nikula tp_printk[FTRACE] 5126e52347bdSJani Nikula Have the tracepoints sent to printk as well as the 5127e52347bdSJani Nikula tracing ring buffer. This is useful for early boot up 5128e52347bdSJani Nikula where the system hangs or reboots and does not give the 5129e52347bdSJani Nikula option for reading the tracing buffer or performing a 5130e52347bdSJani Nikula ftrace_dump_on_oops. 5131e52347bdSJani Nikula 5132e52347bdSJani Nikula To turn off having tracepoints sent to printk, 5133e52347bdSJani Nikula echo 0 > /proc/sys/kernel/tracepoint_printk 5134e52347bdSJani Nikula Note, echoing 1 into this file without the 5135e52347bdSJani Nikula tracepoint_printk kernel cmdline option has no effect. 5136e52347bdSJani Nikula 5137e52347bdSJani Nikula ** CAUTION ** 5138e52347bdSJani Nikula 5139e52347bdSJani Nikula Having tracepoints sent to printk() and activating high 5140e52347bdSJani Nikula frequency tracepoints such as irq or sched, can cause 5141e52347bdSJani Nikula the system to live lock. 5142e52347bdSJani Nikula 5143e52347bdSJani Nikula traceoff_on_warning 5144e52347bdSJani Nikula [FTRACE] enable this option to disable tracing when a 5145e52347bdSJani Nikula warning is hit. This turns off "tracing_on". Tracing can 5146e52347bdSJani Nikula be enabled again by echoing '1' into the "tracing_on" 5147e52347bdSJani Nikula file located in /sys/kernel/debug/tracing/ 5148e52347bdSJani Nikula 5149e52347bdSJani Nikula This option is useful, as it disables the trace before 5150e52347bdSJani Nikula the WARNING dump is called, which prevents the trace to 5151e52347bdSJani Nikula be filled with content caused by the warning output. 5152e52347bdSJani Nikula 5153e52347bdSJani Nikula This option can also be set at run time via the sysctl 5154e52347bdSJani Nikula option: kernel/traceoff_on_warning 5155e52347bdSJani Nikula 5156e52347bdSJani Nikula transparent_hugepage= 5157e52347bdSJani Nikula [KNL] 5158e52347bdSJani Nikula Format: [always|madvise|never] 5159e52347bdSJani Nikula Can be used to control the default behavior of the system 5160e52347bdSJani Nikula with respect to transparent hugepages. 516145c9a74fSMike Rapoport See Documentation/admin-guide/mm/transhuge.rst 516245c9a74fSMike Rapoport for more details. 5163e52347bdSJani Nikula 5164e52347bdSJani Nikula tsc= Disable clocksource stability checks for TSC. 5165e52347bdSJani Nikula Format: <string> 5166e52347bdSJani Nikula [x86] reliable: mark tsc clocksource as reliable, this 5167e52347bdSJani Nikula disables clocksource verification at runtime, as well 5168e52347bdSJani Nikula as the stability checks done at bootup. Used to enable 5169e52347bdSJani Nikula high-resolution timer mode on older hardware, and in 5170e52347bdSJani Nikula virtualized environment. 5171e52347bdSJani Nikula [x86] noirqtime: Do not use TSC to do irq accounting. 5172e52347bdSJani Nikula Used to run time disable IRQ_TIME_ACCOUNTING on any 5173e52347bdSJani Nikula platforms where RDTSC is slow and this accounting 5174e52347bdSJani Nikula can add overhead. 51756be53520SDou Liyang [x86] unstable: mark the TSC clocksource as unstable, this 51766be53520SDou Liyang marks the TSC unconditionally unstable at bootup and 51776be53520SDou Liyang avoids any further wobbles once the TSC watchdog notices. 51780f0b7e1cSJuri Lelli [x86] nowatchdog: disable clocksource watchdog. Used 51790f0b7e1cSJuri Lelli in situations with strict latency requirements (where 51800f0b7e1cSJuri Lelli interruptions from clocksource watchdog are not 51810f0b7e1cSJuri Lelli acceptable). 5182e52347bdSJani Nikula 5183bd35c77eSKrzysztof Piecuch tsc_early_khz= [X86] Skip early TSC calibration and use the given 5184bd35c77eSKrzysztof Piecuch value instead. Useful when the early TSC frequency discovery 5185bd35c77eSKrzysztof Piecuch procedure is not reliable, such as on overclocked systems 5186bd35c77eSKrzysztof Piecuch with CPUID.16h support and partial CPUID.15h support. 5187bd35c77eSKrzysztof Piecuch Format: <unsigned int> 5188bd35c77eSKrzysztof Piecuch 518995c5824fSPawan Gupta tsx= [X86] Control Transactional Synchronization 519095c5824fSPawan Gupta Extensions (TSX) feature in Intel processors that 519195c5824fSPawan Gupta support TSX control. 519295c5824fSPawan Gupta 519395c5824fSPawan Gupta This parameter controls the TSX feature. The options are: 519495c5824fSPawan Gupta 519595c5824fSPawan Gupta on - Enable TSX on the system. Although there are 519695c5824fSPawan Gupta mitigations for all known security vulnerabilities, 519795c5824fSPawan Gupta TSX has been known to be an accelerator for 519895c5824fSPawan Gupta several previous speculation-related CVEs, and 519995c5824fSPawan Gupta so there may be unknown security risks associated 520095c5824fSPawan Gupta with leaving it enabled. 520195c5824fSPawan Gupta 520295c5824fSPawan Gupta off - Disable TSX on the system. (Note that this 520395c5824fSPawan Gupta option takes effect only on newer CPUs which are 520495c5824fSPawan Gupta not vulnerable to MDS, i.e., have 520595c5824fSPawan Gupta MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get 520695c5824fSPawan Gupta the new IA32_TSX_CTRL MSR through a microcode 520795c5824fSPawan Gupta update. This new MSR allows for the reliable 520895c5824fSPawan Gupta deactivation of the TSX functionality.) 520995c5824fSPawan Gupta 52107531a359SPawan Gupta auto - Disable TSX if X86_BUG_TAA is present, 52117531a359SPawan Gupta otherwise enable TSX on the system. 52127531a359SPawan Gupta 521395c5824fSPawan Gupta Not specifying this option is equivalent to tsx=off. 521495c5824fSPawan Gupta 521595c5824fSPawan Gupta See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst 521695c5824fSPawan Gupta for more details. 521795c5824fSPawan Gupta 5218a7a248c5SPawan Gupta tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async 5219a7a248c5SPawan Gupta Abort (TAA) vulnerability. 5220a7a248c5SPawan Gupta 5221a7a248c5SPawan Gupta Similar to Micro-architectural Data Sampling (MDS) 5222a7a248c5SPawan Gupta certain CPUs that support Transactional 5223a7a248c5SPawan Gupta Synchronization Extensions (TSX) are vulnerable to an 5224a7a248c5SPawan Gupta exploit against CPU internal buffers which can forward 5225a7a248c5SPawan Gupta information to a disclosure gadget under certain 5226a7a248c5SPawan Gupta conditions. 5227a7a248c5SPawan Gupta 5228a7a248c5SPawan Gupta In vulnerable processors, the speculatively forwarded 5229a7a248c5SPawan Gupta data can be used in a cache side channel attack, to 5230a7a248c5SPawan Gupta access data to which the attacker does not have direct 5231a7a248c5SPawan Gupta access. 5232a7a248c5SPawan Gupta 5233a7a248c5SPawan Gupta This parameter controls the TAA mitigation. The 5234a7a248c5SPawan Gupta options are: 5235a7a248c5SPawan Gupta 5236a7a248c5SPawan Gupta full - Enable TAA mitigation on vulnerable CPUs 5237a7a248c5SPawan Gupta if TSX is enabled. 5238a7a248c5SPawan Gupta 5239a7a248c5SPawan Gupta full,nosmt - Enable TAA mitigation and disable SMT on 5240a7a248c5SPawan Gupta vulnerable CPUs. If TSX is disabled, SMT 5241a7a248c5SPawan Gupta is not disabled because CPU is not 5242a7a248c5SPawan Gupta vulnerable to cross-thread TAA attacks. 5243a7a248c5SPawan Gupta off - Unconditionally disable TAA mitigation 5244a7a248c5SPawan Gupta 524564870ed1SWaiman Long On MDS-affected machines, tsx_async_abort=off can be 524664870ed1SWaiman Long prevented by an active MDS mitigation as both vulnerabilities 524764870ed1SWaiman Long are mitigated with the same mechanism so in order to disable 524864870ed1SWaiman Long this mitigation, you need to specify mds=off too. 524964870ed1SWaiman Long 5250a7a248c5SPawan Gupta Not specifying this option is equivalent to 5251a7a248c5SPawan Gupta tsx_async_abort=full. On CPUs which are MDS affected 5252a7a248c5SPawan Gupta and deploy MDS mitigation, TAA mitigation is not 5253a7a248c5SPawan Gupta required and doesn't provide any additional 5254a7a248c5SPawan Gupta mitigation. 5255a7a248c5SPawan Gupta 5256a7a248c5SPawan Gupta For details see: 5257a7a248c5SPawan Gupta Documentation/admin-guide/hw-vuln/tsx_async_abort.rst 5258a7a248c5SPawan Gupta 5259e52347bdSJani Nikula turbografx.map[2|3]= [HW,JOY] 5260e52347bdSJani Nikula TurboGraFX parallel port interface 5261e52347bdSJani Nikula Format: 5262e52347bdSJani Nikula <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 52631752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 5264e52347bdSJani Nikula 5265e52347bdSJani Nikula udbg-immortal [PPC] When debugging early kernel crashes that 5266e52347bdSJani Nikula happen after console_init() and before a proper 5267e52347bdSJani Nikula console driver takes over, this boot options might 5268e52347bdSJani Nikula help "seeing" what's going on. 5269e52347bdSJani Nikula 5270e52347bdSJani Nikula uhash_entries= [KNL,NET] 5271e52347bdSJani Nikula Set number of hash buckets for UDP/UDP-Lite connections 5272e52347bdSJani Nikula 5273e52347bdSJani Nikula uhci-hcd.ignore_oc= 5274e52347bdSJani Nikula [USB] Ignore overcurrent events (default N). 5275e52347bdSJani Nikula Some badly-designed motherboards generate lots of 5276e52347bdSJani Nikula bogus events, for ports that aren't wired to 5277e52347bdSJani Nikula anything. Set this parameter to avoid log spamming. 5278e52347bdSJani Nikula Note that genuine overcurrent events won't be 5279e52347bdSJani Nikula reported either. 5280e52347bdSJani Nikula 5281e52347bdSJani Nikula unknown_nmi_panic 5282e52347bdSJani Nikula [X86] Cause panic on unknown NMI. 5283e52347bdSJani Nikula 5284e52347bdSJani Nikula usbcore.authorized_default= 5285e52347bdSJani Nikula [USB] Default USB device authorization: 5286e52347bdSJani Nikula (default -1 = authorized except for wireless USB, 52877bae0432SDmitry Torokhov 0 = not authorized, 1 = authorized, 2 = authorized 52887bae0432SDmitry Torokhov if device connected to internal port) 5289e52347bdSJani Nikula 5290e52347bdSJani Nikula usbcore.autosuspend= 5291e52347bdSJani Nikula [USB] The autosuspend time delay (in seconds) used 5292e52347bdSJani Nikula for newly-detected USB devices (default 2). This 5293e52347bdSJani Nikula is the time required before an idle device will be 5294e52347bdSJani Nikula autosuspended. Devices for which the delay is set 5295e52347bdSJani Nikula to a negative value won't be autosuspended at all. 5296e52347bdSJani Nikula 5297e52347bdSJani Nikula usbcore.usbfs_snoop= 5298e52347bdSJani Nikula [USB] Set to log all usbfs traffic (default 0 = off). 5299e52347bdSJani Nikula 5300e52347bdSJani Nikula usbcore.usbfs_snoop_max= 5301e52347bdSJani Nikula [USB] Maximum number of bytes to snoop in each URB 5302e52347bdSJani Nikula (default = 65536). 5303e52347bdSJani Nikula 5304e52347bdSJani Nikula usbcore.blinkenlights= 5305e52347bdSJani Nikula [USB] Set to cycle leds on hubs (default 0 = off). 5306e52347bdSJani Nikula 5307e52347bdSJani Nikula usbcore.old_scheme_first= 5308e52347bdSJani Nikula [USB] Start with the old device initialization 53093155f4f4SAlan Stern scheme (default 0 = off). 5310e52347bdSJani Nikula 5311e52347bdSJani Nikula usbcore.usbfs_memory_mb= 5312e52347bdSJani Nikula [USB] Memory limit (in MB) for buffers allocated by 5313e52347bdSJani Nikula usbfs (default = 16, 0 = max = 2047). 5314e52347bdSJani Nikula 5315e52347bdSJani Nikula usbcore.use_both_schemes= 5316e52347bdSJani Nikula [USB] Try the other device initialization scheme 5317e52347bdSJani Nikula if the first one fails (default 1 = enabled). 5318e52347bdSJani Nikula 5319e52347bdSJani Nikula usbcore.initial_descriptor_timeout= 5320e52347bdSJani Nikula [USB] Specifies timeout for the initial 64-byte 5321e52347bdSJani Nikula USB_REQ_GET_DESCRIPTOR request in milliseconds 5322e52347bdSJani Nikula (default 5000 = 5.0 seconds). 5323e52347bdSJani Nikula 5324e52347bdSJani Nikula usbcore.nousb [USB] Disable the USB subsystem 5325e52347bdSJani Nikula 5326027bd6caSKai-Heng Feng usbcore.quirks= 5327027bd6caSKai-Heng Feng [USB] A list of quirk entries to augment the built-in 5328027bd6caSKai-Heng Feng usb core quirk list. List entries are separated by 5329027bd6caSKai-Heng Feng commas. Each entry has the form 5330027bd6caSKai-Heng Feng VendorID:ProductID:Flags. The IDs are 4-digit hex 5331027bd6caSKai-Heng Feng numbers and Flags is a set of letters. Each letter 5332027bd6caSKai-Heng Feng will change the built-in quirk; setting it if it is 5333027bd6caSKai-Heng Feng clear and clearing it if it is set. The letters have 5334027bd6caSKai-Heng Feng the following meanings: 5335027bd6caSKai-Heng Feng a = USB_QUIRK_STRING_FETCH_255 (string 5336027bd6caSKai-Heng Feng descriptors must not be fetched using 5337027bd6caSKai-Heng Feng a 255-byte read); 5338027bd6caSKai-Heng Feng b = USB_QUIRK_RESET_RESUME (device can't resume 5339027bd6caSKai-Heng Feng correctly so reset it instead); 5340027bd6caSKai-Heng Feng c = USB_QUIRK_NO_SET_INTF (device can't handle 5341027bd6caSKai-Heng Feng Set-Interface requests); 5342027bd6caSKai-Heng Feng d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't 5343027bd6caSKai-Heng Feng handle its Configuration or Interface 5344027bd6caSKai-Heng Feng strings); 5345027bd6caSKai-Heng Feng e = USB_QUIRK_RESET (device can't be reset 5346027bd6caSKai-Heng Feng (e.g morph devices), don't use reset); 5347027bd6caSKai-Heng Feng f = USB_QUIRK_HONOR_BNUMINTERFACES (device has 5348027bd6caSKai-Heng Feng more interface descriptions than the 5349027bd6caSKai-Heng Feng bNumInterfaces count, and can't handle 5350027bd6caSKai-Heng Feng talking to these interfaces); 5351027bd6caSKai-Heng Feng g = USB_QUIRK_DELAY_INIT (device needs a pause 5352027bd6caSKai-Heng Feng during initialization, after we read 5353027bd6caSKai-Heng Feng the device descriptor); 5354027bd6caSKai-Heng Feng h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For 5355027bd6caSKai-Heng Feng high speed and super speed interrupt 5356027bd6caSKai-Heng Feng endpoints, the USB 2.0 and USB 3.0 spec 5357027bd6caSKai-Heng Feng require the interval in microframes (1 5358027bd6caSKai-Heng Feng microframe = 125 microseconds) to be 5359027bd6caSKai-Heng Feng calculated as interval = 2 ^ 5360027bd6caSKai-Heng Feng (bInterval-1). 5361027bd6caSKai-Heng Feng Devices with this quirk report their 5362027bd6caSKai-Heng Feng bInterval as the result of this 5363027bd6caSKai-Heng Feng calculation instead of the exponent 5364027bd6caSKai-Heng Feng variable used in the calculation); 5365027bd6caSKai-Heng Feng i = USB_QUIRK_DEVICE_QUALIFIER (device can't 5366027bd6caSKai-Heng Feng handle device_qualifier descriptor 5367027bd6caSKai-Heng Feng requests); 5368027bd6caSKai-Heng Feng j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device 5369027bd6caSKai-Heng Feng generates spurious wakeup, ignore 5370027bd6caSKai-Heng Feng remote wakeup capability); 5371027bd6caSKai-Heng Feng k = USB_QUIRK_NO_LPM (device can't handle Link 5372027bd6caSKai-Heng Feng Power Management); 5373027bd6caSKai-Heng Feng l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL 5374027bd6caSKai-Heng Feng (Device reports its bInterval as linear 5375027bd6caSKai-Heng Feng frames instead of the USB 2.0 5376027bd6caSKai-Heng Feng calculation); 5377027bd6caSKai-Heng Feng m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs 5378027bd6caSKai-Heng Feng to be disconnected before suspend to 53794d8d5a39SKai-Heng Feng prevent spurious wakeup); 53804d8d5a39SKai-Heng Feng n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a 53814d8d5a39SKai-Heng Feng pause after every control message); 5382781f0766SKai-Heng Feng o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra 5383781f0766SKai-Heng Feng delay after resetting its port); 5384027bd6caSKai-Heng Feng Example: quirks=0781:5580:bk,0a5c:5834:gij 5385027bd6caSKai-Heng Feng 5386e52347bdSJani Nikula usbhid.mousepoll= 5387e52347bdSJani Nikula [USBHID] The interval which mice are to be polled at. 5388e52347bdSJani Nikula 5389933bfe4dSTobias Jakobi usbhid.jspoll= 5390933bfe4dSTobias Jakobi [USBHID] The interval which joysticks are to be polled at. 5391933bfe4dSTobias Jakobi 53922ddc8e2dSFilip Alac usbhid.kbpoll= 53932ddc8e2dSFilip Alac [USBHID] The interval which keyboards are to be polled at. 53942ddc8e2dSFilip Alac 5395e52347bdSJani Nikula usb-storage.delay_use= 5396e52347bdSJani Nikula [UMS] The delay in seconds before a new device is 5397e52347bdSJani Nikula scanned for Logical Units (default 1). 5398e52347bdSJani Nikula 5399e52347bdSJani Nikula usb-storage.quirks= 5400e52347bdSJani Nikula [UMS] A list of quirks entries to supplement or 5401e52347bdSJani Nikula override the built-in unusual_devs list. List 5402e52347bdSJani Nikula entries are separated by commas. Each entry has 5403e52347bdSJani Nikula the form VID:PID:Flags where VID and PID are Vendor 5404e52347bdSJani Nikula and Product ID values (4-digit hex numbers) and 5405e52347bdSJani Nikula Flags is a set of characters, each corresponding 5406e52347bdSJani Nikula to a common usb-storage quirk flag as follows: 5407e52347bdSJani Nikula a = SANE_SENSE (collect more than 18 bytes 540865cc8bf9SOliver Neukum of sense data, not on uas); 5409e52347bdSJani Nikula b = BAD_SENSE (don't collect more than 18 541065cc8bf9SOliver Neukum bytes of sense data, not on uas); 5411e52347bdSJani Nikula c = FIX_CAPACITY (decrease the reported 5412e52347bdSJani Nikula device capacity by one sector); 5413e52347bdSJani Nikula d = NO_READ_DISC_INFO (don't use 541465cc8bf9SOliver Neukum READ_DISC_INFO command, not on uas); 5415e52347bdSJani Nikula e = NO_READ_CAPACITY_16 (don't use 5416e52347bdSJani Nikula READ_CAPACITY_16 command); 5417e52347bdSJani Nikula f = NO_REPORT_OPCODES (don't use report opcodes 5418e52347bdSJani Nikula command, uas only); 5419e52347bdSJani Nikula g = MAX_SECTORS_240 (don't transfer more than 5420e52347bdSJani Nikula 240 sectors at a time, uas only); 5421e52347bdSJani Nikula h = CAPACITY_HEURISTICS (decrease the 5422e52347bdSJani Nikula reported device capacity by one 5423e52347bdSJani Nikula sector if the number is odd); 5424e52347bdSJani Nikula i = IGNORE_DEVICE (don't bind to this 5425e52347bdSJani Nikula device); 5426e52347bdSJani Nikula j = NO_REPORT_LUNS (don't use report luns 5427e52347bdSJani Nikula command, uas only); 5428e52347bdSJani Nikula l = NOT_LOCKABLE (don't try to lock and 542965cc8bf9SOliver Neukum unlock ejectable media, not on uas); 5430e52347bdSJani Nikula m = MAX_SECTORS_64 (don't transfer more 543165cc8bf9SOliver Neukum than 64 sectors = 32 KB at a time, 543265cc8bf9SOliver Neukum not on uas); 5433e52347bdSJani Nikula n = INITIAL_READ10 (force a retry of the 543465cc8bf9SOliver Neukum initial READ(10) command, not on uas); 5435e52347bdSJani Nikula o = CAPACITY_OK (accept the capacity 543665cc8bf9SOliver Neukum reported by the device, not on uas); 5437e52347bdSJani Nikula p = WRITE_CACHE (the device cache is ON 543865cc8bf9SOliver Neukum by default, not on uas); 5439e52347bdSJani Nikula r = IGNORE_RESIDUE (the device reports 544065cc8bf9SOliver Neukum bogus residue values, not on uas); 5441e52347bdSJani Nikula s = SINGLE_LUN (the device has only one 5442e52347bdSJani Nikula Logical Unit); 5443e52347bdSJani Nikula t = NO_ATA_1X (don't allow ATA(12) and ATA(16) 5444e52347bdSJani Nikula commands, uas only); 5445e52347bdSJani Nikula u = IGNORE_UAS (don't bind to the uas driver); 5446e52347bdSJani Nikula w = NO_WP_DETECT (don't test whether the 5447e52347bdSJani Nikula medium is write-protected). 5448e52347bdSJani Nikula y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE 544965cc8bf9SOliver Neukum even if the device claims no cache, 545065cc8bf9SOliver Neukum not on uas) 5451e52347bdSJani Nikula Example: quirks=0419:aaf5:rl,0421:0433:rc 5452e52347bdSJani Nikula 5453e52347bdSJani Nikula user_debug= [KNL,ARM] 5454e52347bdSJani Nikula Format: <int> 5455e52347bdSJani Nikula See arch/arm/Kconfig.debug help text. 5456e52347bdSJani Nikula 1 - undefined instruction events 5457e52347bdSJani Nikula 2 - system calls 5458e52347bdSJani Nikula 4 - invalid data aborts 5459e52347bdSJani Nikula 8 - SIGSEGV faults 5460e52347bdSJani Nikula 16 - SIGBUS faults 5461e52347bdSJani Nikula Example: user_debug=31 5462e52347bdSJani Nikula 5463e52347bdSJani Nikula userpte= 5464e52347bdSJani Nikula [X86] Flags controlling user PTE allocations. 5465e52347bdSJani Nikula 5466e52347bdSJani Nikula nohigh = do not allocate PTE pages in 5467e52347bdSJani Nikula HIGHMEM regardless of setting 5468e52347bdSJani Nikula of CONFIG_HIGHPTE. 5469e52347bdSJani Nikula 5470e52347bdSJani Nikula vdso= [X86,SH] 5471e52347bdSJani Nikula On X86_32, this is an alias for vdso32=. Otherwise: 5472e52347bdSJani Nikula 5473e52347bdSJani Nikula vdso=1: enable VDSO (the default) 5474e52347bdSJani Nikula vdso=0: disable VDSO mapping 5475e52347bdSJani Nikula 5476e52347bdSJani Nikula vdso32= [X86] Control the 32-bit vDSO 5477e52347bdSJani Nikula vdso32=1: enable 32-bit VDSO 5478e52347bdSJani Nikula vdso32=0 or vdso32=2: disable 32-bit VDSO 5479e52347bdSJani Nikula 5480e52347bdSJani Nikula See the help text for CONFIG_COMPAT_VDSO for more 5481e52347bdSJani Nikula details. If CONFIG_COMPAT_VDSO is set, the default is 5482e52347bdSJani Nikula vdso32=0; otherwise, the default is vdso32=1. 5483e52347bdSJani Nikula 5484e52347bdSJani Nikula For compatibility with older kernels, vdso32=2 is an 5485e52347bdSJani Nikula alias for vdso32=0. 5486e52347bdSJani Nikula 5487e52347bdSJani Nikula Try vdso32=0 if you encounter an error that says: 5488e52347bdSJani Nikula dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! 5489e52347bdSJani Nikula 5490e52347bdSJani Nikula vector= [IA-64,SMP] 5491e52347bdSJani Nikula vector=percpu: enable percpu vector domain 5492e52347bdSJani Nikula 5493e52347bdSJani Nikula video= [FB] Frame buffer configuration 5494ab42b818SMauro Carvalho Chehab See Documentation/fb/modedb.rst. 5495e52347bdSJani Nikula 5496e52347bdSJani Nikula video.brightness_switch_enabled= [0,1] 5497e52347bdSJani Nikula If set to 1, on receiving an ACPI notify event 5498e52347bdSJani Nikula generated by hotkey, video driver will adjust brightness 5499e52347bdSJani Nikula level and then send out the event to user space through 5500e52347bdSJani Nikula the allocated input device; If set to 0, video driver 5501e52347bdSJani Nikula will only send out the event without touching backlight 5502e52347bdSJani Nikula brightness level. 5503e52347bdSJani Nikula default: 1 5504e52347bdSJani Nikula 5505e52347bdSJani Nikula virtio_mmio.device= 5506e52347bdSJani Nikula [VMMIO] Memory mapped virtio (platform) device. 5507e52347bdSJani Nikula 5508e52347bdSJani Nikula <size>@<baseaddr>:<irq>[:<id>] 5509e52347bdSJani Nikula where: 5510e52347bdSJani Nikula <size> := size (can use standard suffixes 5511e52347bdSJani Nikula like K, M and G) 5512e52347bdSJani Nikula <baseaddr> := physical base address 5513e52347bdSJani Nikula <irq> := interrupt number (as passed to 5514e52347bdSJani Nikula request_irq()) 5515e52347bdSJani Nikula <id> := (optional) platform device id 5516e52347bdSJani Nikula example: 5517e52347bdSJani Nikula virtio_mmio.device=1K@0x100b0000:48:7 5518e52347bdSJani Nikula 5519e52347bdSJani Nikula Can be used multiple times for multiple devices. 5520e52347bdSJani Nikula 5521e52347bdSJani Nikula vga= [BOOT,X86-32] Select a particular video mode 5522cb1aaebeSMauro Carvalho Chehab See Documentation/x86/boot.rst and 55234f4cfa6cSMauro Carvalho Chehab Documentation/admin-guide/svga.rst. 5524e52347bdSJani Nikula Use vga=ask for menu. 5525e52347bdSJani Nikula This is actually a boot loader parameter; the value is 5526e52347bdSJani Nikula passed to the kernel using a special protocol. 5527e52347bdSJani Nikula 5528f682a97aSAlexander Duyck vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y. 5529f682a97aSAlexander Duyck May slow down system boot speed, especially when 5530f682a97aSAlexander Duyck enabled on systems with a large amount of memory. 5531f682a97aSAlexander Duyck All options are enabled by default, and this 5532f682a97aSAlexander Duyck interface is meant to allow for selectively 5533f682a97aSAlexander Duyck enabling or disabling specific virtual memory 5534f682a97aSAlexander Duyck debugging features. 5535f682a97aSAlexander Duyck 5536f682a97aSAlexander Duyck Available options are: 5537f682a97aSAlexander Duyck P Enable page structure init time poisoning 5538f682a97aSAlexander Duyck - Disable all of the above options 5539f682a97aSAlexander Duyck 5540e52347bdSJani Nikula vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 5541e52347bdSJani Nikula size of <nn>. This can be used to increase the 5542e52347bdSJani Nikula minimum size (128MB on x86). It can also be used to 5543e52347bdSJani Nikula decrease the size and leave more room for directly 5544e52347bdSJani Nikula mapped kernel RAM. 5545e52347bdSJani Nikula 55463f429842SHeiko Carstens vmcp_cma=nn[MG] [KNL,S390] 55473f429842SHeiko Carstens Sets the memory size reserved for contiguous memory 55483f429842SHeiko Carstens allocations for the vmcp device driver. 55493f429842SHeiko Carstens 5550e52347bdSJani Nikula vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 5551e52347bdSJani Nikula Format: <command> 5552e52347bdSJani Nikula 5553e52347bdSJani Nikula vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 5554e52347bdSJani Nikula Format: <command> 5555e52347bdSJani Nikula 5556e52347bdSJani Nikula vmpoff= [KNL,S390] Perform z/VM CP command after power off. 5557e52347bdSJani Nikula Format: <command> 5558e52347bdSJani Nikula 5559e52347bdSJani Nikula vsyscall= [X86-64] 5560e52347bdSJani Nikula Controls the behavior of vsyscalls (i.e. calls to 5561e52347bdSJani Nikula fixed addresses of 0xffffffffff600x00 from legacy 5562e52347bdSJani Nikula code). Most statically-linked binaries and older 5563e52347bdSJani Nikula versions of glibc use these calls. Because these 5564e52347bdSJani Nikula functions are at fixed addresses, they make nice 5565e52347bdSJani Nikula targets for exploits that can control RIP. 5566e52347bdSJani Nikula 5567e52347bdSJani Nikula emulate [default] Vsyscalls turn into traps and are 5568bd49e16eSAndy Lutomirski emulated reasonably safely. The vsyscall 5569bd49e16eSAndy Lutomirski page is readable. 5570e52347bdSJani Nikula 5571bd49e16eSAndy Lutomirski xonly Vsyscalls turn into traps and are 5572bd49e16eSAndy Lutomirski emulated reasonably safely. The vsyscall 5573bd49e16eSAndy Lutomirski page is not readable. 5574e52347bdSJani Nikula 5575e52347bdSJani Nikula none Vsyscalls don't work at all. This makes 5576e52347bdSJani Nikula them quite hard to use for exploits but 5577e52347bdSJani Nikula might break your system. 5578e52347bdSJani Nikula 5579e52347bdSJani Nikula vt.color= [VT] Default text color. 5580e52347bdSJani Nikula Format: 0xYX, X = foreground, Y = background. 5581e52347bdSJani Nikula Default: 0x07 = light gray on black. 5582e52347bdSJani Nikula 5583e52347bdSJani Nikula vt.cur_default= [VT] Default cursor shape. 5584e52347bdSJani Nikula Format: 0xCCBBAA, where AA, BB, and CC are the same as 5585e52347bdSJani Nikula the parameters of the <Esc>[?A;B;Cc escape sequence; 5586e52347bdSJani Nikula see VGA-softcursor.txt. Default: 2 = underline. 5587e52347bdSJani Nikula 5588e52347bdSJani Nikula vt.default_blu= [VT] 5589e52347bdSJani Nikula Format: <blue0>,<blue1>,<blue2>,...,<blue15> 5590e52347bdSJani Nikula Change the default blue palette of the console. 5591e52347bdSJani Nikula This is a 16-member array composed of values 5592e52347bdSJani Nikula ranging from 0-255. 5593e52347bdSJani Nikula 5594e52347bdSJani Nikula vt.default_grn= [VT] 5595e52347bdSJani Nikula Format: <green0>,<green1>,<green2>,...,<green15> 5596e52347bdSJani Nikula Change the default green palette of the console. 5597e52347bdSJani Nikula This is a 16-member array composed of values 5598e52347bdSJani Nikula ranging from 0-255. 5599e52347bdSJani Nikula 5600e52347bdSJani Nikula vt.default_red= [VT] 5601e52347bdSJani Nikula Format: <red0>,<red1>,<red2>,...,<red15> 5602e52347bdSJani Nikula Change the default red palette of the console. 5603e52347bdSJani Nikula This is a 16-member array composed of values 5604e52347bdSJani Nikula ranging from 0-255. 5605e52347bdSJani Nikula 5606e52347bdSJani Nikula vt.default_utf8= 5607e52347bdSJani Nikula [VT] 5608e52347bdSJani Nikula Format=<0|1> 5609e52347bdSJani Nikula Set system-wide default UTF-8 mode for all tty's. 5610e52347bdSJani Nikula Default is 1, i.e. UTF-8 mode is enabled for all 5611e52347bdSJani Nikula newly opened terminals. 5612e52347bdSJani Nikula 5613e52347bdSJani Nikula vt.global_cursor_default= 5614e52347bdSJani Nikula [VT] 5615e52347bdSJani Nikula Format=<-1|0|1> 5616e52347bdSJani Nikula Set system-wide default for whether a cursor 5617e52347bdSJani Nikula is shown on new VTs. Default is -1, 5618e52347bdSJani Nikula i.e. cursors will be created by default unless 5619e52347bdSJani Nikula overridden by individual drivers. 0 will hide 5620e52347bdSJani Nikula cursors, 1 will display them. 5621e52347bdSJani Nikula 5622e52347bdSJani Nikula vt.italic= [VT] Default color for italic text; 0-15. 5623e52347bdSJani Nikula Default: 2 = green. 5624e52347bdSJani Nikula 5625e52347bdSJani Nikula vt.underline= [VT] Default color for underlined text; 0-15. 5626e52347bdSJani Nikula Default: 3 = cyan. 5627e52347bdSJani Nikula 5628e52347bdSJani Nikula watchdog timers [HW,WDT] For information on watchdog timers, 5629cc2a2d19SMauro Carvalho Chehab see Documentation/watchdog/watchdog-parameters.rst 5630e52347bdSJani Nikula or other driver-specific files in the 5631e52347bdSJani Nikula Documentation/watchdog/ directory. 5632e52347bdSJani Nikula 563311295055SLaurence Oberman watchdog_thresh= 563411295055SLaurence Oberman [KNL] 563511295055SLaurence Oberman Set the hard lockup detector stall duration 563611295055SLaurence Oberman threshold in seconds. The soft lockup detector 563711295055SLaurence Oberman threshold is set to twice the value. A value of 0 563811295055SLaurence Oberman disables both lockup detectors. Default is 10 563911295055SLaurence Oberman seconds. 564011295055SLaurence Oberman 5641e52347bdSJani Nikula workqueue.watchdog_thresh= 5642e52347bdSJani Nikula If CONFIG_WQ_WATCHDOG is configured, workqueue can 5643e52347bdSJani Nikula warn stall conditions and dump internal state to 5644e52347bdSJani Nikula help debugging. 0 disables workqueue stall 5645e52347bdSJani Nikula detection; otherwise, it's the stall threshold 5646e52347bdSJani Nikula duration in seconds. The default value is 30 and 5647e52347bdSJani Nikula it can be updated at runtime by writing to the 5648e52347bdSJani Nikula corresponding sysfs file. 5649e52347bdSJani Nikula 5650e52347bdSJani Nikula workqueue.disable_numa 5651e52347bdSJani Nikula By default, all work items queued to unbound 5652e52347bdSJani Nikula workqueues are affine to the NUMA nodes they're 5653e52347bdSJani Nikula issued on, which results in better behavior in 5654e52347bdSJani Nikula general. If NUMA affinity needs to be disabled for 5655e52347bdSJani Nikula whatever reason, this option can be used. Note 5656e52347bdSJani Nikula that this also can be controlled per-workqueue for 5657e52347bdSJani Nikula workqueues visible under /sys/bus/workqueue/. 5658e52347bdSJani Nikula 5659e52347bdSJani Nikula workqueue.power_efficient 5660e52347bdSJani Nikula Per-cpu workqueues are generally preferred because 5661e52347bdSJani Nikula they show better performance thanks to cache 5662e52347bdSJani Nikula locality; unfortunately, per-cpu workqueues tend to 5663e52347bdSJani Nikula be more power hungry than unbound workqueues. 5664e52347bdSJani Nikula 5665e52347bdSJani Nikula Enabling this makes the per-cpu workqueues which 5666e52347bdSJani Nikula were observed to contribute significantly to power 5667e52347bdSJani Nikula consumption unbound, leading to measurably lower 5668e52347bdSJani Nikula power usage at the cost of small performance 5669e52347bdSJani Nikula overhead. 5670e52347bdSJani Nikula 5671e52347bdSJani Nikula The default value of this parameter is determined by 5672e52347bdSJani Nikula the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. 5673e52347bdSJani Nikula 5674e52347bdSJani Nikula workqueue.debug_force_rr_cpu 5675e52347bdSJani Nikula Workqueue used to implicitly guarantee that work 5676e52347bdSJani Nikula items queued without explicit CPU specified are put 5677e52347bdSJani Nikula on the local CPU. This guarantee is no longer true 5678e52347bdSJani Nikula and while local CPU is still preferred work items 5679e52347bdSJani Nikula may be put on foreign CPUs. This debug option 5680e52347bdSJani Nikula forces round-robin CPU selection to flush out 5681e52347bdSJani Nikula usages which depend on the now broken guarantee. 5682e52347bdSJani Nikula When enabled, memory and cache locality will be 5683e52347bdSJani Nikula impacted. 5684e52347bdSJani Nikula 5685e52347bdSJani Nikula x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 5686e52347bdSJani Nikula default x2apic cluster mode on platforms 5687e52347bdSJani Nikula supporting x2apic. 5688e52347bdSJani Nikula 5689e52347bdSJani Nikula x86_intel_mid_timer= [X86-32,APBT] 5690e52347bdSJani Nikula Choose timer option for x86 Intel MID platform. 5691e52347bdSJani Nikula Two valid options are apbt timer only and lapic timer 5692e52347bdSJani Nikula plus one apbt timer for broadcast timer. 5693e52347bdSJani Nikula x86_intel_mid_timer=apbt_only | lapic_and_apbt 5694e52347bdSJani Nikula 5695e52347bdSJani Nikula xen_512gb_limit [KNL,X86-64,XEN] 5696e52347bdSJani Nikula Restricts the kernel running paravirtualized under Xen 5697e52347bdSJani Nikula to use only up to 512 GB of RAM. The reason to do so is 5698e52347bdSJani Nikula crash analysis tools and Xen tools for doing domain 5699e52347bdSJani Nikula save/restore/migration must be enabled to handle larger 5700e52347bdSJani Nikula domains. 5701e52347bdSJani Nikula 5702e52347bdSJani Nikula xen_emul_unplug= [HW,X86,XEN] 5703e52347bdSJani Nikula Unplug Xen emulated devices 5704e52347bdSJani Nikula Format: [unplug0,][unplug1] 5705e52347bdSJani Nikula ide-disks -- unplug primary master IDE devices 5706e52347bdSJani Nikula aux-ide-disks -- unplug non-primary-master IDE devices 5707e52347bdSJani Nikula nics -- unplug network devices 5708e52347bdSJani Nikula all -- unplug all emulated devices (NICs and IDE disks) 5709e52347bdSJani Nikula unnecessary -- unplugging emulated devices is 5710e52347bdSJani Nikula unnecessary even if the host did not respond to 5711e52347bdSJani Nikula the unplug protocol 5712e52347bdSJani Nikula never -- do not unplug even if version check succeeds 5713e52347bdSJani Nikula 5714c6875f3aSBoris Ostrovsky xen_legacy_crash [X86,XEN] 5715c6875f3aSBoris Ostrovsky Crash from Xen panic notifier, without executing late 5716c6875f3aSBoris Ostrovsky panic() code such as dumping handler. 5717c6875f3aSBoris Ostrovsky 5718e52347bdSJani Nikula xen_nopvspin [X86,XEN] 5719e52347bdSJani Nikula Disables the ticketlock slowpath using Xen PV 5720e52347bdSJani Nikula optimizations. 5721e52347bdSJani Nikula 5722e52347bdSJani Nikula xen_nopv [X86] 5723e52347bdSJani Nikula Disables the PV optimizations forcing the HVM guest to 5724e52347bdSJani Nikula run as generic HVM guest with no PV drivers. 5725b39b0497SZhenzhong Duan This option is obsoleted by the "nopv" option, which 5726b39b0497SZhenzhong Duan has equivalent effect for XEN platform. 5727e52347bdSJani Nikula 5728197ecb38SMarek Marczykowski-Górecki xen_scrub_pages= [XEN] 5729197ecb38SMarek Marczykowski-Górecki Boolean option to control scrubbing pages before giving them back 5730197ecb38SMarek Marczykowski-Górecki to Xen, for use by other domains. Can be also changed at runtime 5731197ecb38SMarek Marczykowski-Górecki with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. 5732197ecb38SMarek Marczykowski-Górecki Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. 5733197ecb38SMarek Marczykowski-Górecki 57342ec16bc0SRyan Thibodeaux xen_timer_slop= [X86-64,XEN] 57352ec16bc0SRyan Thibodeaux Set the timer slop (in nanoseconds) for the virtual Xen 57362ec16bc0SRyan Thibodeaux timers (default is 100000). This adjusts the minimum 57372ec16bc0SRyan Thibodeaux delta of virtualized Xen timers, where lower values 57382ec16bc0SRyan Thibodeaux improve timer resolution at the expense of processing 57392ec16bc0SRyan Thibodeaux more timer interrupts. 57402ec16bc0SRyan Thibodeaux 574130978346SZhenzhong Duan nopv= [X86,XEN,KVM,HYPER_V,VMWARE] 574230978346SZhenzhong Duan Disables the PV optimizations forcing the guest to run 574330978346SZhenzhong Duan as generic guest with no PV drivers. Currently support 574430978346SZhenzhong Duan XEN HVM, KVM, HYPER_V and VMWARE guest. 574530978346SZhenzhong Duan 5746e52347bdSJani Nikula xirc2ps_cs= [NET,PCMCIA] 5747e52347bdSJani Nikula Format: 5748e52347bdSJani Nikula <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 5749c0addc9aSLaurentiu Tudor 5750ba45cff6SMichael Neuling xive= [PPC] 5751ba45cff6SMichael Neuling By default on POWER9 and above, the kernel will 5752ba45cff6SMichael Neuling natively use the XIVE interrupt controller. This option 5753ba45cff6SMichael Neuling allows the fallback firmware mode to be used: 5754ba45cff6SMichael Neuling 5755ba45cff6SMichael Neuling off Fallback to firmware control of XIVE interrupt 5756ba45cff6SMichael Neuling controller on both pseries and powernv 5757ba45cff6SMichael Neuling platforms. Only useful on POWER9 and above. 5758ba45cff6SMichael Neuling 5759c0addc9aSLaurentiu Tudor xhci-hcd.quirks [USB,KNL] 5760c0addc9aSLaurentiu Tudor A hex value specifying bitmask with supplemental xhci 5761c0addc9aSLaurentiu Tudor host controller quirks. Meaning of each bit can be 5762c0addc9aSLaurentiu Tudor consulted in header drivers/usb/host/xhci.h. 57636278f55bSGustavo Romero 57646278f55bSGustavo Romero xmon [PPC] 57656278f55bSGustavo Romero Format: { early | on | rw | ro | off } 57666278f55bSGustavo Romero Controls if xmon debugger is enabled. Default is off. 57676278f55bSGustavo Romero Passing only "xmon" is equivalent to "xmon=early". 57686278f55bSGustavo Romero early Call xmon as early as possible on boot; xmon 57696278f55bSGustavo Romero debugger is called from setup_arch(). 57706278f55bSGustavo Romero on xmon debugger hooks will be installed so xmon 57716278f55bSGustavo Romero is only called on a kernel crash. Default mode, 57726278f55bSGustavo Romero i.e. either "ro" or "rw" mode, is controlled 57736278f55bSGustavo Romero with CONFIG_XMON_DEFAULT_RO_MODE. 57746278f55bSGustavo Romero rw xmon debugger hooks will be installed so xmon 57756278f55bSGustavo Romero is called only on a kernel crash, mode is write, 57766278f55bSGustavo Romero meaning SPR registers, memory and, other data 57776278f55bSGustavo Romero can be written using xmon commands. 57786278f55bSGustavo Romero ro same as "rw" option above but SPR registers, 57796278f55bSGustavo Romero memory, and other data can't be written using 57806278f55bSGustavo Romero xmon commands. 57816278f55bSGustavo Romero off xmon is disabled. 5782