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] 25e52347bdSJani Nikula acpi_backlight=vendor 26e52347bdSJani Nikula acpi_backlight=video 27e52347bdSJani Nikula If set to vendor, prefer vendor specific driver 28e52347bdSJani Nikula (e.g. thinkpad_acpi, sony_acpi, etc.) instead 29e52347bdSJani Nikula of the ACPI video.ko driver. 30e52347bdSJani Nikula 31e52347bdSJani Nikula acpi_force_32bit_fadt_addr 32e52347bdSJani Nikula force FADT to use 32 bit addresses rather than the 33e52347bdSJani Nikula 64 bit X_* addresses. Some firmware have broken 64 34e52347bdSJani Nikula bit addresses for force ACPI ignore these and use 35e52347bdSJani Nikula the older legacy 32 bit addresses. 36e52347bdSJani Nikula 37e52347bdSJani Nikula acpica_no_return_repair [HW, ACPI] 38e52347bdSJani Nikula Disable AML predefined validation mechanism 39e52347bdSJani Nikula This mechanism can repair the evaluation result to make 40e52347bdSJani Nikula the return objects more ACPI specification compliant. 41e52347bdSJani Nikula This option is useful for developers to identify the 42e52347bdSJani Nikula root cause of an AML interpreter issue when the issue 43e52347bdSJani Nikula has something to do with the repair mechanism. 44e52347bdSJani Nikula 45e52347bdSJani Nikula acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] 46e52347bdSJani Nikula acpi.debug_level= [HW,ACPI,ACPI_DEBUG] 47e52347bdSJani Nikula Format: <int> 48e52347bdSJani Nikula CONFIG_ACPI_DEBUG must be enabled to produce any ACPI 49e52347bdSJani Nikula debug output. Bits in debug_layer correspond to a 50e52347bdSJani Nikula _COMPONENT in an ACPI source file, e.g., 51e52347bdSJani Nikula #define _COMPONENT ACPI_PCI_COMPONENT 52e52347bdSJani Nikula Bits in debug_level correspond to a level in 53e52347bdSJani Nikula ACPI_DEBUG_PRINT statements, e.g., 54e52347bdSJani Nikula ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... 55e52347bdSJani Nikula The debug_level mask defaults to "info". See 56cb1aaebeSMauro Carvalho Chehab Documentation/firmware-guide/acpi/debug.rst for more information about 57e52347bdSJani Nikula debug layers and levels. 58e52347bdSJani Nikula 59e52347bdSJani Nikula Enable processor driver info messages: 60e52347bdSJani Nikula acpi.debug_layer=0x20000000 61e52347bdSJani Nikula Enable PCI/PCI interrupt routing info messages: 62e52347bdSJani Nikula acpi.debug_layer=0x400000 63e52347bdSJani Nikula Enable AML "Debug" output, i.e., stores to the Debug 64e52347bdSJani Nikula object while interpreting AML: 65e52347bdSJani Nikula acpi.debug_layer=0xffffffff acpi.debug_level=0x2 66e52347bdSJani Nikula Enable all messages related to ACPI hardware: 67e52347bdSJani Nikula acpi.debug_layer=0x2 acpi.debug_level=0xffffffff 68e52347bdSJani Nikula 69e52347bdSJani Nikula Some values produce so much output that the system is 70e52347bdSJani Nikula unusable. The "log_buf_len" parameter may be useful 71e52347bdSJani Nikula if you need to capture more output. 72e52347bdSJani Nikula 73e52347bdSJani Nikula acpi_enforce_resources= [ACPI] 74e52347bdSJani Nikula { strict | lax | no } 75e52347bdSJani Nikula Check for resource conflicts between native drivers 76e52347bdSJani Nikula and ACPI OperationRegions (SystemIO and SystemMemory 77e52347bdSJani Nikula only). IO ports and memory declared in ACPI might be 78e52347bdSJani Nikula used by the ACPI subsystem in arbitrary AML code and 79e52347bdSJani Nikula can interfere with legacy drivers. 80e52347bdSJani Nikula strict (default): access to resources claimed by ACPI 81e52347bdSJani Nikula is denied; legacy drivers trying to access reserved 82e52347bdSJani Nikula resources will fail to bind to device using them. 83e52347bdSJani Nikula lax: access to resources claimed by ACPI is allowed; 84e52347bdSJani Nikula legacy drivers trying to access reserved resources 85e52347bdSJani Nikula will bind successfully but a warning message is logged. 86e52347bdSJani Nikula no: ACPI OperationRegions are not marked as reserved, 87e52347bdSJani Nikula no further checks are performed. 88e52347bdSJani Nikula 89e52347bdSJani Nikula acpi_force_table_verification [HW,ACPI] 90e52347bdSJani Nikula Enable table checksum verification during early stage. 91e52347bdSJani Nikula By default, this is disabled due to x86 early mapping 92e52347bdSJani Nikula size limitation. 93e52347bdSJani Nikula 94e52347bdSJani Nikula acpi_irq_balance [HW,ACPI] 95e52347bdSJani Nikula ACPI will balance active IRQs 96e52347bdSJani Nikula default in APIC mode 97e52347bdSJani Nikula 98e52347bdSJani Nikula acpi_irq_nobalance [HW,ACPI] 99e52347bdSJani Nikula ACPI will not move active IRQs (default) 100e52347bdSJani Nikula default in PIC mode 101e52347bdSJani Nikula 102e52347bdSJani Nikula acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 103e52347bdSJani Nikula Format: <irq>,<irq>... 104e52347bdSJani Nikula 105e52347bdSJani Nikula acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 106e52347bdSJani Nikula use by PCI 107e52347bdSJani Nikula Format: <irq>,<irq>... 108e52347bdSJani Nikula 1099c4aa1eeSLv Zheng acpi_mask_gpe= [HW,ACPI] 1109c4aa1eeSLv Zheng Due to the existence of _Lxx/_Exx, some GPEs triggered 1119c4aa1eeSLv Zheng by unsupported hardware/firmware features can result in 1129c4aa1eeSLv Zheng GPE floodings that cannot be automatically disabled by 1139c4aa1eeSLv Zheng the GPE dispatcher. 1149c4aa1eeSLv Zheng This facility can be used to prevent such uncontrolled 1159c4aa1eeSLv Zheng GPE floodings. 116a7583e72SYunfeng Ye Format: <byte> 1179c4aa1eeSLv Zheng 118e52347bdSJani Nikula acpi_no_auto_serialize [HW,ACPI] 119e52347bdSJani Nikula Disable auto-serialization of AML methods 120e52347bdSJani Nikula AML control methods that contain the opcodes to create 121e52347bdSJani Nikula named objects will be marked as "Serialized" by the 122e52347bdSJani Nikula auto-serialization feature. 123e52347bdSJani Nikula This feature is enabled by default. 124e52347bdSJani Nikula This option allows to turn off the feature. 125e52347bdSJani Nikula 126e52347bdSJani Nikula acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump 127e52347bdSJani Nikula kernels. 128e52347bdSJani Nikula 129e52347bdSJani Nikula acpi_no_static_ssdt [HW,ACPI] 130e52347bdSJani Nikula Disable installation of static SSDTs at early boot time 131e52347bdSJani Nikula By default, SSDTs contained in the RSDT/XSDT will be 132e52347bdSJani Nikula installed automatically and they will appear under 133e52347bdSJani Nikula /sys/firmware/acpi/tables. 134e52347bdSJani Nikula This option turns off this feature. 135e52347bdSJani Nikula Note that specifying this option does not affect 136e52347bdSJani Nikula dynamic table installation which will install SSDT 137e52347bdSJani Nikula tables to /sys/firmware/acpi/tables/dynamic. 138e52347bdSJani Nikula 139e52347bdSJani Nikula acpi_rsdp= [ACPI,EFI,KEXEC] 140e52347bdSJani Nikula Pass the RSDP address to the kernel, mostly used 141e52347bdSJani Nikula on machines running EFI runtime service to boot the 142e52347bdSJani Nikula second kernel for kdump. 143e52347bdSJani Nikula 144e52347bdSJani Nikula acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 145e52347bdSJani Nikula Format: To spoof as Windows 98: ="Microsoft Windows" 146e52347bdSJani Nikula 147e52347bdSJani Nikula acpi_rev_override [ACPI] Override the _REV object to return 5 (instead 148e52347bdSJani Nikula of 2 which is mandated by ACPI 6) as the supported ACPI 149e52347bdSJani Nikula specification revision (when using this switch, it may 150e52347bdSJani Nikula be necessary to carry out a cold reboot _twice_ in a 151e52347bdSJani Nikula row to make it take effect on the platform firmware). 152e52347bdSJani Nikula 153e52347bdSJani Nikula acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 154e52347bdSJani Nikula acpi_osi="string1" # add string1 155e52347bdSJani Nikula acpi_osi="!string2" # remove string2 156e52347bdSJani Nikula acpi_osi=!* # remove all strings 157e52347bdSJani Nikula acpi_osi=! # disable all built-in OS vendor 158e52347bdSJani Nikula strings 159e52347bdSJani Nikula acpi_osi=!! # enable all built-in OS vendor 160e52347bdSJani Nikula strings 161e52347bdSJani Nikula acpi_osi= # disable all strings 162e52347bdSJani Nikula 163e52347bdSJani Nikula 'acpi_osi=!' can be used in combination with single or 164e52347bdSJani Nikula multiple 'acpi_osi="string1"' to support specific OS 165e52347bdSJani Nikula vendor string(s). Note that such command can only 166e52347bdSJani Nikula affect the default state of the OS vendor strings, thus 167e52347bdSJani Nikula it cannot affect the default state of the feature group 168e52347bdSJani Nikula strings and the current state of the OS vendor strings, 169e52347bdSJani Nikula specifying it multiple times through kernel command line 170e52347bdSJani Nikula is meaningless. This command is useful when one do not 171e52347bdSJani Nikula care about the state of the feature group strings which 172e52347bdSJani Nikula should be controlled by the OSPM. 173e52347bdSJani Nikula Examples: 174e52347bdSJani Nikula 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent 175e52347bdSJani Nikula to 'acpi_osi="Windows 2000" acpi_osi=!', they all 176e52347bdSJani Nikula can make '_OSI("Windows 2000")' TRUE. 177e52347bdSJani Nikula 178e52347bdSJani Nikula 'acpi_osi=' cannot be used in combination with other 179e52347bdSJani Nikula 'acpi_osi=' command lines, the _OSI method will not 180e52347bdSJani Nikula exist in the ACPI namespace. NOTE that such command can 181e52347bdSJani Nikula only affect the _OSI support state, thus specifying it 182e52347bdSJani Nikula multiple times through kernel command line is also 183e52347bdSJani Nikula meaningless. 184e52347bdSJani Nikula Examples: 185e52347bdSJani Nikula 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' 186e52347bdSJani Nikula FALSE. 187e52347bdSJani Nikula 188e52347bdSJani Nikula 'acpi_osi=!*' can be used in combination with single or 189e52347bdSJani Nikula multiple 'acpi_osi="string1"' to support specific 190e52347bdSJani Nikula string(s). Note that such command can affect the 191e52347bdSJani Nikula current state of both the OS vendor strings and the 192e52347bdSJani Nikula feature group strings, thus specifying it multiple times 193e52347bdSJani Nikula through kernel command line is meaningful. But it may 194e52347bdSJani Nikula still not able to affect the final state of a string if 195e52347bdSJani Nikula there are quirks related to this string. This command 196e52347bdSJani Nikula is useful when one want to control the state of the 197e52347bdSJani Nikula feature group strings to debug BIOS issues related to 198e52347bdSJani Nikula the OSPM features. 199e52347bdSJani Nikula Examples: 200e52347bdSJani Nikula 1. 'acpi_osi="Module Device" acpi_osi=!*' can make 201e52347bdSJani Nikula '_OSI("Module Device")' FALSE. 202e52347bdSJani Nikula 2. 'acpi_osi=!* acpi_osi="Module Device"' can make 203e52347bdSJani Nikula '_OSI("Module Device")' TRUE. 204e52347bdSJani Nikula 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is 205e52347bdSJani Nikula equivalent to 206e52347bdSJani Nikula 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' 207e52347bdSJani Nikula and 208e52347bdSJani Nikula 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', 209e52347bdSJani Nikula they all will make '_OSI("Windows 2000")' TRUE. 210e52347bdSJani Nikula 211e52347bdSJani Nikula acpi_pm_good [X86] 212e52347bdSJani Nikula Override the pmtimer bug detection: force the kernel 213e52347bdSJani Nikula to assume that this machine's pmtimer latches its value 214e52347bdSJani Nikula and always returns good values. 215e52347bdSJani Nikula 216e52347bdSJani Nikula acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 217e52347bdSJani Nikula Format: { level | edge | high | low } 218e52347bdSJani Nikula 219e52347bdSJani Nikula acpi_skip_timer_override [HW,ACPI] 220e52347bdSJani Nikula Recognize and ignore IRQ0/pin2 Interrupt Override. 221e52347bdSJani Nikula For broken nForce2 BIOS resulting in XT-PIC timer. 222e52347bdSJani Nikula 223e52347bdSJani Nikula acpi_sleep= [HW,ACPI] Sleep options 224e52347bdSJani Nikula Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, 22557044031SRafael J. Wysocki old_ordering, nonvs, sci_force_enable, nobl } 226151f4e2bSMauro Carvalho Chehab See Documentation/power/video.rst for information on 227e52347bdSJani Nikula s3_bios and s3_mode. 228e52347bdSJani Nikula s3_beep is for debugging; it makes the PC's speaker beep 229e52347bdSJani Nikula as soon as the kernel's real-mode entry point is called. 230e52347bdSJani Nikula s4_nohwsig prevents ACPI hardware signature from being 231e52347bdSJani Nikula used during resume from hibernation. 232e52347bdSJani Nikula old_ordering causes the ACPI 1.0 ordering of the _PTS 233e52347bdSJani Nikula control method, with respect to putting devices into 234e52347bdSJani Nikula low power states, to be enforced (the ACPI 2.0 ordering 235e52347bdSJani Nikula of _PTS is used by default). 236e52347bdSJani Nikula nonvs prevents the kernel from saving/restoring the 237e52347bdSJani Nikula ACPI NVS memory during suspend/hibernation and resume. 238e52347bdSJani Nikula sci_force_enable causes the kernel to set SCI_EN directly 239e52347bdSJani Nikula on resume from S1/S3 (which is against the ACPI spec, 240e52347bdSJani Nikula but some broken systems don't work without it). 24157044031SRafael J. Wysocki nobl causes the internal blacklist of systems known to 24257044031SRafael J. Wysocki behave incorrectly in some ways with respect to system 24357044031SRafael J. Wysocki suspend and resume to be ignored (use wisely). 244e52347bdSJani Nikula 245e52347bdSJani Nikula acpi_use_timer_override [HW,ACPI] 246e52347bdSJani Nikula Use timer override. For some broken Nvidia NF5 boards 247e52347bdSJani Nikula that require a timer override, but don't have HPET 248e52347bdSJani Nikula 249e52347bdSJani Nikula add_efi_memmap [EFI; X86] Include EFI memory map in 250e52347bdSJani Nikula kernel's map of available physical RAM. 251e52347bdSJani Nikula 252e52347bdSJani Nikula agp= [AGP] 253e52347bdSJani Nikula { off | try_unsupported } 254e52347bdSJani Nikula off: disable AGP support 255e52347bdSJani Nikula try_unsupported: try to drive unsupported chipsets 256e52347bdSJani Nikula (may crash computer or cause data corruption) 257e52347bdSJani Nikula 258e52347bdSJani Nikula ALSA [HW,ALSA] 2591ca2c806SMauro Carvalho Chehab See Documentation/sound/alsa-configuration.rst 260e52347bdSJani Nikula 261e52347bdSJani Nikula alignment= [KNL,ARM] 262e52347bdSJani Nikula Allow the default userspace alignment fault handler 263e52347bdSJani Nikula behaviour to be specified. Bit 0 enables warnings, 264e52347bdSJani Nikula bit 1 enables fixups, and bit 2 sends a segfault. 265e52347bdSJani Nikula 266e52347bdSJani Nikula align_va_addr= [X86-64] 267e52347bdSJani Nikula Align virtual addresses by clearing slice [14:12] when 268e52347bdSJani Nikula allocating a VMA at process creation time. This option 269e52347bdSJani Nikula gives you up to 3% performance improvement on AMD F15h 270e52347bdSJani Nikula machines (where it is enabled by default) for a 271e52347bdSJani Nikula CPU-intensive style benchmark, and it can vary highly in 272e52347bdSJani Nikula a microbenchmark depending on workload and compiler. 273e52347bdSJani Nikula 274e52347bdSJani Nikula 32: only for 32-bit processes 275e52347bdSJani Nikula 64: only for 64-bit processes 276e52347bdSJani Nikula on: enable for both 32- and 64-bit processes 277e52347bdSJani Nikula off: disable for both 32- and 64-bit processes 278e52347bdSJani Nikula 279e52347bdSJani Nikula alloc_snapshot [FTRACE] 280e52347bdSJani Nikula Allocate the ftrace snapshot buffer on boot up when the 281e52347bdSJani Nikula main buffer is allocated. This is handy if debugging 282e52347bdSJani Nikula and you need to use tracing_snapshot() on boot up, and 283e52347bdSJani Nikula do not want to use tracing_snapshot_alloc() as it needs 284e52347bdSJani Nikula to be done where GFP_KERNEL allocations are allowed. 285e52347bdSJani Nikula 286e52347bdSJani Nikula amd_iommu= [HW,X86-64] 287e52347bdSJani Nikula Pass parameters to the AMD IOMMU driver in the system. 288e52347bdSJani Nikula Possible values are: 289e52347bdSJani Nikula fullflush - enable flushing of IO/TLB entries when 290e52347bdSJani Nikula they are unmapped. Otherwise they are 291e52347bdSJani Nikula flushed before they will be reused, which 292e52347bdSJani Nikula is a lot of faster 293e52347bdSJani Nikula off - do not initialize any AMD IOMMU found in 294e52347bdSJani Nikula the system 295e52347bdSJani Nikula force_isolation - Force device isolation for all 296e52347bdSJani Nikula devices. The IOMMU driver is not 297e52347bdSJani Nikula allowed anymore to lift isolation 298e52347bdSJani Nikula requirements as needed. This option 299e52347bdSJani Nikula does not override iommu=pt 300e52347bdSJani Nikula 301e52347bdSJani Nikula amd_iommu_dump= [HW,X86-64] 302e52347bdSJani Nikula Enable AMD IOMMU driver option to dump the ACPI table 303e52347bdSJani Nikula for AMD IOMMU. With this option enabled, AMD IOMMU 304e52347bdSJani Nikula driver will print ACPI tables for AMD IOMMU during 305e52347bdSJani Nikula IOMMU initialization. 306e52347bdSJani Nikula 307e52347bdSJani Nikula amd_iommu_intr= [HW,X86-64] 308e52347bdSJani Nikula Specifies one of the following AMD IOMMU interrupt 309e52347bdSJani Nikula remapping modes: 310e52347bdSJani Nikula legacy - Use legacy interrupt remapping mode. 311e52347bdSJani Nikula vapic - Use virtual APIC mode, which allows IOMMU 312e52347bdSJani Nikula to inject interrupts directly into guest. 313e52347bdSJani Nikula This mode requires kvm-amd.avic=1. 314e52347bdSJani Nikula (Default when IOMMU HW support is present.) 315e52347bdSJani Nikula 316e52347bdSJani Nikula amijoy.map= [HW,JOY] Amiga joystick support 317e52347bdSJani Nikula Map of devices attached to JOY0DAT and JOY1DAT 318e52347bdSJani Nikula Format: <a>,<b> 3191752118dSTom Saeger See also Documentation/input/joydev/joystick.rst 320e52347bdSJani Nikula 321e52347bdSJani Nikula analog.map= [HW,JOY] Analog joystick and gamepad support 322e52347bdSJani Nikula Specifies type or capabilities of an analog joystick 323e52347bdSJani Nikula connected to one of 16 gameports 324e52347bdSJani Nikula Format: <type1>,<type2>,..<type16> 325e52347bdSJani Nikula 326e52347bdSJani Nikula apc= [HW,SPARC] 327e52347bdSJani Nikula Power management functions (SPARCstation-4/5 + deriv.) 328e52347bdSJani Nikula Format: noidle 329e52347bdSJani Nikula Disable APC CPU standby support. SPARCstation-Fox does 330e52347bdSJani Nikula not play well with APC CPU idle - disable it if you have 331e52347bdSJani Nikula APC and your system crashes randomly. 332e52347bdSJani Nikula 33364e05d11SDou Liyang apic= [APIC,X86] Advanced Programmable Interrupt Controller 334806654a9SWill Deacon Change the output verbosity while booting 335e52347bdSJani Nikula Format: { quiet (default) | verbose | debug } 336e52347bdSJani Nikula Change the amount of debugging information output 337e52347bdSJani Nikula when initialising the APIC and IO-APIC components. 33864e05d11SDou Liyang For X86-32, this can also be used to specify an APIC 33964e05d11SDou Liyang driver name. 34064e05d11SDou Liyang Format: apic=driver_name 34164e05d11SDou Liyang Examples: apic=bigsmp 342e52347bdSJani Nikula 343e52347bdSJani Nikula apic_extnmi= [APIC,X86] External NMI delivery setting 344e52347bdSJani Nikula Format: { bsp (default) | all | none } 345e52347bdSJani Nikula bsp: External NMI is delivered only to CPU 0 346e52347bdSJani Nikula all: External NMIs are broadcast to all CPUs as a 347e52347bdSJani Nikula backup of CPU 0 348e52347bdSJani Nikula none: External NMI is masked for all CPUs. This is 349e52347bdSJani Nikula useful so that a dump capture kernel won't be 350e52347bdSJani Nikula shot down by NMI 351e52347bdSJani Nikula 352e52347bdSJani Nikula autoconf= [IPV6] 353e52347bdSJani Nikula See Documentation/networking/ipv6.txt. 354e52347bdSJani Nikula 355e52347bdSJani Nikula show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller 356e52347bdSJani Nikula Limit apic dumping. The parameter defines the maximal 357e52347bdSJani Nikula number of local apics being dumped. Also it is possible 358e52347bdSJani Nikula to set it to "all" by meaning -- no limit here. 359e52347bdSJani Nikula Format: { 1 (default) | 2 | ... | all }. 360e52347bdSJani Nikula The parameter valid if only apic=debug or 361e52347bdSJani Nikula apic=verbose is specified. 362e52347bdSJani Nikula Example: apic=debug show_lapic=all 363e52347bdSJani Nikula 364e52347bdSJani Nikula apm= [APM] Advanced Power Management 365e52347bdSJani Nikula See header of arch/x86/kernel/apm_32.c. 366e52347bdSJani Nikula 367e52347bdSJani Nikula arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 368e52347bdSJani Nikula Format: <io>,<irq>,<nodeID> 369e52347bdSJani Nikula 370e52347bdSJani Nikula ataflop= [HW,M68k] 371e52347bdSJani Nikula 372e52347bdSJani Nikula atarimouse= [HW,MOUSE] Atari Mouse 373e52347bdSJani Nikula 374e52347bdSJani Nikula atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 375e52347bdSJani Nikula EzKey and similar keyboards 376e52347bdSJani Nikula 377e52347bdSJani Nikula atkbd.reset= [HW] Reset keyboard during initialization 378e52347bdSJani Nikula 379e52347bdSJani Nikula atkbd.set= [HW] Select keyboard code set 380e52347bdSJani Nikula Format: <int> (2 = AT (default), 3 = PS/2) 381e52347bdSJani Nikula 382e52347bdSJani Nikula atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 383e52347bdSJani Nikula keyboards 384e52347bdSJani Nikula 385e52347bdSJani Nikula atkbd.softraw= [HW] Choose between synthetic and real raw mode 386e52347bdSJani Nikula Format: <bool> (0 = real, 1 = synthetic (default)) 387e52347bdSJani Nikula 388e52347bdSJani Nikula atkbd.softrepeat= [HW] 389e52347bdSJani Nikula Use software keyboard repeat 390e52347bdSJani Nikula 391e52347bdSJani Nikula audit= [KNL] Enable the audit sub-system 39211dd2666SGreg Edwards Format: { "0" | "1" | "off" | "on" } 39311dd2666SGreg Edwards 0 | off - kernel audit is disabled and can not be 39411dd2666SGreg Edwards enabled until the next reboot 395e52347bdSJani Nikula unset - kernel audit is initialized but disabled and 396e52347bdSJani Nikula will be fully enabled by the userspace auditd. 39711dd2666SGreg Edwards 1 | on - kernel audit is initialized and partially 39811dd2666SGreg Edwards enabled, storing at most audit_backlog_limit 39911dd2666SGreg Edwards messages in RAM until it is fully enabled by the 40011dd2666SGreg Edwards userspace auditd. 401e52347bdSJani Nikula Default: unset 402e52347bdSJani Nikula 403e52347bdSJani Nikula audit_backlog_limit= [KNL] Set the audit queue size limit. 404e52347bdSJani Nikula Format: <int> (must be >=0) 405e52347bdSJani Nikula Default: 64 406e52347bdSJani Nikula 407e52347bdSJani Nikula bau= [X86_UV] Enable the BAU on SGI UV. The default 408e52347bdSJani Nikula behavior is to disable the BAU (i.e. bau=0). 409e52347bdSJani Nikula Format: { "0" | "1" } 410e52347bdSJani Nikula 0 - Disable the BAU. 411e52347bdSJani Nikula 1 - Enable the BAU. 412e52347bdSJani Nikula unset - Disable the BAU. 413e52347bdSJani Nikula 414e52347bdSJani Nikula baycom_epp= [HW,AX25] 415e52347bdSJani Nikula Format: <io>,<mode> 416e52347bdSJani Nikula 417e52347bdSJani Nikula baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 418e52347bdSJani Nikula Format: <io>,<mode> 419e52347bdSJani Nikula See header of drivers/net/hamradio/baycom_par.c. 420e52347bdSJani Nikula 421e52347bdSJani Nikula baycom_ser_fdx= [HW,AX25] 422e52347bdSJani Nikula BayCom Serial Port AX.25 Modem (Full Duplex Mode) 423e52347bdSJani Nikula Format: <io>,<irq>,<mode>[,<baud>] 424e52347bdSJani Nikula See header of drivers/net/hamradio/baycom_ser_fdx.c. 425e52347bdSJani Nikula 426e52347bdSJani Nikula baycom_ser_hdx= [HW,AX25] 427e52347bdSJani Nikula BayCom Serial Port AX.25 Modem (Half Duplex Mode) 428e52347bdSJani Nikula Format: <io>,<irq>,<mode> 429e52347bdSJani Nikula See header of drivers/net/hamradio/baycom_ser_hdx.c. 430e52347bdSJani Nikula 431e52347bdSJani Nikula blkdevparts= Manual partition parsing of block device(s) for 432e52347bdSJani Nikula embedded devices based on command line input. 433898bd37aSMauro Carvalho Chehab See Documentation/block/cmdline-partition.rst 434e52347bdSJani Nikula 435e52347bdSJani Nikula boot_delay= Milliseconds to delay each printk during boot. 436e52347bdSJani Nikula Values larger than 10 seconds (10000) are changed to 437e52347bdSJani Nikula no delay (0). 438e52347bdSJani Nikula Format: integer 439e52347bdSJani Nikula 4407495e092SSteven Rostedt (VMware) bootconfig [KNL] 4417495e092SSteven Rostedt (VMware) Extended command line options can be added to an initrd 4427495e092SSteven Rostedt (VMware) and this will cause the kernel to look for it. 4437495e092SSteven Rostedt (VMware) 4447495e092SSteven Rostedt (VMware) See Documentation/admin-guide/bootconfig.rst 4457495e092SSteven Rostedt (VMware) 446e52347bdSJani Nikula bert_disable [ACPI] 447e52347bdSJani Nikula Disable BERT OS support on buggy BIOSes. 448e52347bdSJani Nikula 449e52347bdSJani Nikula bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 450e52347bdSJani Nikula bttv.radio= Most important insmod options are available as 451e52347bdSJani Nikula kernel args too. 452a405ed85STom Saeger bttv.pll= See Documentation/media/v4l-drivers/bttv.rst 453e52347bdSJani Nikula bttv.tuner= 454e52347bdSJani Nikula 455e52347bdSJani Nikula bulk_remove=off [PPC] This parameter disables the use of the pSeries 456e52347bdSJani Nikula firmware feature for flushing multiple hpte entries 457e52347bdSJani Nikula at a time. 458e52347bdSJani Nikula 459e52347bdSJani Nikula c101= [NET] Moxa C101 synchronous serial card 460e52347bdSJani Nikula 461e52347bdSJani Nikula cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 462e52347bdSJani Nikula Sometimes CPU hardware bugs make them report the cache 463e52347bdSJani Nikula size incorrectly. The kernel will attempt work arounds 464e52347bdSJani Nikula to fix known problems, but for some CPUs it is not 465e52347bdSJani Nikula possible to determine what the correct size should be. 466e52347bdSJani Nikula This option provides an override for these situations. 467e52347bdSJani Nikula 4683fc46fc9SMartin Kepplinger carrier_timeout= 4693fc46fc9SMartin Kepplinger [NET] Specifies amount of time (in seconds) that 4703fc46fc9SMartin Kepplinger the kernel should wait for a network carrier. By default 4713fc46fc9SMartin Kepplinger it waits 120 seconds. 4723fc46fc9SMartin Kepplinger 473e52347bdSJani Nikula ca_keys= [KEYS] This parameter identifies a specific key(s) on 474e52347bdSJani Nikula the system trusted keyring to be used for certificate 475e52347bdSJani Nikula trust validation. 476e52347bdSJani Nikula format: { id:<keyid> | builtin } 477e52347bdSJani Nikula 478e52347bdSJani Nikula cca= [MIPS] Override the kernel pages' cache coherency 479e52347bdSJani Nikula algorithm. Accepted values range from 0 to 7 480e52347bdSJani Nikula inclusive. See arch/mips/include/asm/pgtable-bits.h 481e52347bdSJani Nikula for platform specific values (SB1, Loongson3 and 482e52347bdSJani Nikula others). 483e52347bdSJani Nikula 484e52347bdSJani Nikula ccw_timeout_log [S390] 4858b4a503dSMauro Carvalho Chehab See Documentation/s390/common_io.rst for details. 486e52347bdSJani Nikula 487e52347bdSJani Nikula cgroup_disable= [KNL] Disable a particular controller 488e52347bdSJani Nikula Format: {name of the controller(s) to disable} 489e52347bdSJani Nikula The effects of cgroup_disable=foo are: 490e52347bdSJani Nikula - foo isn't auto-mounted if you mount all cgroups in 491e52347bdSJani Nikula a single hierarchy 492e52347bdSJani Nikula - foo isn't visible as an individually mountable 493e52347bdSJani Nikula subsystem 494e52347bdSJani Nikula {Currently only "memory" controller deal with this and 495e52347bdSJani Nikula cut the overhead, others just disable the usage. So 496e52347bdSJani Nikula only cgroup_disable=memory is actually worthy} 497e52347bdSJani Nikula 4983fc9c12dSTejun Heo cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1 4993fc9c12dSTejun Heo Format: { { controller | "all" | "named" } 5003fc9c12dSTejun Heo [,{ controller | "all" | "named" }...] } 501e52347bdSJani Nikula Like cgroup_disable, but only applies to cgroup v1; 502e52347bdSJani Nikula the blacklisted controllers remain available in cgroup2. 5033fc9c12dSTejun Heo "all" blacklists all controllers and "named" disables 5043fc9c12dSTejun Heo named mounts. Specifying both "all" and "named" disables 5053fc9c12dSTejun Heo all v1 hierarchies. 506e52347bdSJani Nikula 507e52347bdSJani Nikula cgroup.memory= [KNL] Pass options to the cgroup memory controller. 508e52347bdSJani Nikula Format: <string> 509e52347bdSJani Nikula nosocket -- Disable socket memory accounting. 510e52347bdSJani Nikula nokmem -- Disable kernel memory accounting. 511e52347bdSJani Nikula 512e52347bdSJani Nikula checkreqprot [SELINUX] Set initial checkreqprot flag value. 513e52347bdSJani Nikula Format: { "0" | "1" } 514e52347bdSJani Nikula See security/selinux/Kconfig help text. 515e52347bdSJani Nikula 0 -- check protection applied by kernel (includes 516e52347bdSJani Nikula any implied execute protection). 517e52347bdSJani Nikula 1 -- check protection requested by application. 518e52347bdSJani Nikula Default value is set via a kernel config option. 519e52347bdSJani Nikula Value can be changed at runtime via 520d41415ebSStephen Smalley /sys/fs/selinux/checkreqprot. 521e52347bdSJani Nikula 522e52347bdSJani Nikula cio_ignore= [S390] 5238b4a503dSMauro Carvalho Chehab See Documentation/s390/common_io.rst for details. 524e52347bdSJani Nikula clk_ignore_unused 525e52347bdSJani Nikula [CLK] 526e52347bdSJani Nikula Prevents the clock framework from automatically gating 527e52347bdSJani Nikula clocks that have not been explicitly enabled by a Linux 528e52347bdSJani Nikula device driver but are enabled in hardware at reset or 529e52347bdSJani Nikula by the bootloader/firmware. Note that this does not 530e52347bdSJani Nikula force such clocks to be always-on nor does it reserve 531e52347bdSJani Nikula those clocks in any way. This parameter is useful for 532e52347bdSJani Nikula debug and development, but should not be needed on a 533e52347bdSJani Nikula platform with proper driver support. For more 53418bcaa4eSMauro Carvalho Chehab information, see Documentation/driver-api/clk.rst. 535e52347bdSJani Nikula 536e52347bdSJani Nikula clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 537e52347bdSJani Nikula [Deprecated] 538e52347bdSJani Nikula Forces specified clocksource (if available) to be used 539e52347bdSJani Nikula when calculating gettimeofday(). If specified 540e52347bdSJani Nikula clocksource is not available, it defaults to PIT. 541e52347bdSJani Nikula Format: { pit | tsc | cyclone | pmtmr } 542e52347bdSJani Nikula 543e52347bdSJani Nikula clocksource= Override the default clocksource 544e52347bdSJani Nikula Format: <string> 545e52347bdSJani Nikula Override the default clocksource and use the clocksource 546e52347bdSJani Nikula with the name specified. 547e52347bdSJani Nikula Some clocksource names to choose from, depending on 548e52347bdSJani Nikula the platform: 549e52347bdSJani Nikula [all] jiffies (this is the base, fallback clocksource) 550e52347bdSJani Nikula [ACPI] acpi_pm 551e52347bdSJani Nikula [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 552e52347bdSJani Nikula pxa_timer,timer3,32k_counter,timer0_1 553e52347bdSJani Nikula [X86-32] pit,hpet,tsc; 554e52347bdSJani Nikula scx200_hrt on Geode; cyclone on IBM x440 555e52347bdSJani Nikula [MIPS] MIPS 556e52347bdSJani Nikula [PARISC] cr16 557e52347bdSJani Nikula [S390] tod 558e52347bdSJani Nikula [SH] SuperH 559e52347bdSJani Nikula [SPARC64] tick 560e52347bdSJani Nikula [X86-64] hpet,tsc 561e52347bdSJani Nikula 562e52347bdSJani Nikula clocksource.arm_arch_timer.evtstrm= 563e52347bdSJani Nikula [ARM,ARM64] 564e52347bdSJani Nikula Format: <bool> 565e52347bdSJani Nikula Enable/disable the eventstream feature of the ARM 566e52347bdSJani Nikula architected timer so that code using WFE-based polling 567e52347bdSJani Nikula loops can be debugged more effectively on production 568e52347bdSJani Nikula systems. 569e52347bdSJani Nikula 570e52347bdSJani Nikula clearcpuid=BITNUM [X86] 571e52347bdSJani Nikula Disable CPUID feature X for the kernel. See 572e52347bdSJani Nikula arch/x86/include/asm/cpufeatures.h for the valid bit 573e52347bdSJani Nikula numbers. Note the Linux specific bits are not necessarily 574e52347bdSJani Nikula stable over kernel options, but the vendor specific 575e52347bdSJani Nikula ones should be. 576e52347bdSJani Nikula Also note that user programs calling CPUID directly 577e52347bdSJani Nikula or using the feature without checking anything 578e52347bdSJani Nikula will still see it. This just prevents it from 579e52347bdSJani Nikula being used by the kernel or shown in /proc/cpuinfo. 580e52347bdSJani Nikula Also note the kernel might malfunction if you disable 581e52347bdSJani Nikula some critical bits. 582e52347bdSJani Nikula 583e52347bdSJani Nikula cma=nn[MG]@[start[MG][-end[MG]]] 584e52347bdSJani Nikula [ARM,X86,KNL] 585e52347bdSJani Nikula Sets the size of kernel global memory area for 586e52347bdSJani Nikula contiguous memory allocations and optionally the 587e52347bdSJani Nikula placement constraint by the physical address range of 588e52347bdSJani Nikula memory allocations. A value of 0 disables CMA 589e52347bdSJani Nikula altogether. For more information, see 590e52347bdSJani Nikula include/linux/dma-contiguous.h 591e52347bdSJani Nikula 592e52347bdSJani Nikula cmo_free_hint= [PPC] Format: { yes | no } 593e52347bdSJani Nikula Specify whether pages are marked as being inactive 594e52347bdSJani Nikula when they are freed. This is used in CMO environments 595e52347bdSJani Nikula to determine OS memory pressure for page stealing by 596e52347bdSJani Nikula a hypervisor. 597e52347bdSJani Nikula Default: yes 598e52347bdSJani Nikula 599e52347bdSJani Nikula coherent_pool=nn[KMG] [ARM,KNL] 600e52347bdSJani Nikula Sets the size of memory pool for coherent, atomic dma 601e52347bdSJani Nikula allocations, by default set to 256K. 602e52347bdSJani Nikula 603e52347bdSJani Nikula com20020= [HW,NET] ARCnet - COM20020 chipset 604e52347bdSJani Nikula Format: 605e52347bdSJani Nikula <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 606e52347bdSJani Nikula 607e52347bdSJani Nikula com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 608e52347bdSJani Nikula Format: <io>[,<irq>] 609e52347bdSJani Nikula 610e52347bdSJani Nikula com90xx= [HW,NET] 611e52347bdSJani Nikula ARCnet - COM90xx chipset (memory-mapped buffers) 612e52347bdSJani Nikula Format: <io>[,<irq>[,<memstart>]] 613e52347bdSJani Nikula 614e52347bdSJani Nikula condev= [HW,S390] console device 615e52347bdSJani Nikula conmode= 616e52347bdSJani Nikula 617e52347bdSJani Nikula console= [KNL] Output console device and options. 618e52347bdSJani Nikula 619e52347bdSJani Nikula tty<n> Use the virtual console device <n>. 620e52347bdSJani Nikula 621e52347bdSJani Nikula ttyS<n>[,options] 622e52347bdSJani Nikula ttyUSB0[,options] 623e52347bdSJani Nikula Use the specified serial port. The options are of 624e52347bdSJani Nikula the form "bbbbpnf", where "bbbb" is the baud rate, 625e52347bdSJani Nikula "p" is parity ("n", "o", or "e"), "n" is number of 626e52347bdSJani Nikula bits, and "f" is flow control ("r" for RTS or 627e52347bdSJani Nikula omit it). Default is "9600n8". 628e52347bdSJani Nikula 629e52347bdSJani Nikula See Documentation/admin-guide/serial-console.rst for more 630e52347bdSJani Nikula information. See 631e52347bdSJani Nikula Documentation/networking/netconsole.txt for an 632e52347bdSJani Nikula alternative. 633e52347bdSJani Nikula 634e52347bdSJani Nikula uart[8250],io,<addr>[,options] 635e52347bdSJani Nikula uart[8250],mmio,<addr>[,options] 636e52347bdSJani Nikula uart[8250],mmio16,<addr>[,options] 637e52347bdSJani Nikula uart[8250],mmio32,<addr>[,options] 638e52347bdSJani Nikula uart[8250],0x<addr>[,options] 639e52347bdSJani Nikula Start an early, polled-mode console on the 8250/16550 640e52347bdSJani Nikula UART at the specified I/O port or MMIO address, 641e52347bdSJani Nikula switching to the matching ttyS device later. 642e52347bdSJani Nikula MMIO inter-register address stride is either 8-bit 643e52347bdSJani Nikula (mmio), 16-bit (mmio16), or 32-bit (mmio32). 644e52347bdSJani Nikula If none of [io|mmio|mmio16|mmio32], <addr> is assumed 645e52347bdSJani Nikula to be equivalent to 'mmio'. 'options' are specified in 646e52347bdSJani Nikula the same format described for ttyS above; if unspecified, 647e52347bdSJani Nikula the h/w is not re-initialized. 648e52347bdSJani Nikula 649e52347bdSJani Nikula hvc<n> Use the hypervisor console device <n>. This is for 650e52347bdSJani Nikula both Xen and PowerPC hypervisors. 651e52347bdSJani Nikula 652e52347bdSJani Nikula If the device connected to the port is not a TTY but a braille 653e52347bdSJani Nikula device, prepend "brl," before the device type, for instance 654e52347bdSJani Nikula console=brl,ttyS0 655e52347bdSJani Nikula For now, only VisioBraille is supported. 656e52347bdSJani Nikula 657cca10d58SSergey Senozhatsky console_msg_format= 658cca10d58SSergey Senozhatsky [KNL] Change console messages format 659cca10d58SSergey Senozhatsky default 660cca10d58SSergey Senozhatsky By default we print messages on consoles in 661cca10d58SSergey Senozhatsky "[time stamp] text\n" format (time stamp may not be 662cca10d58SSergey Senozhatsky printed, depending on CONFIG_PRINTK_TIME or 663cca10d58SSergey Senozhatsky `printk_time' param). 664cca10d58SSergey Senozhatsky syslog 665cca10d58SSergey Senozhatsky Switch to syslog format: "<%u>[time stamp] text\n" 666cca10d58SSergey Senozhatsky IOW, each message will have a facility and loglevel 667cca10d58SSergey Senozhatsky prefix. The format is similar to one used by syslog() 668cca10d58SSergey Senozhatsky syscall, or to executing "dmesg -S --raw" or to reading 669cca10d58SSergey Senozhatsky from /proc/kmsg. 670cca10d58SSergey Senozhatsky 671e52347bdSJani Nikula consoleblank= [KNL] The console blank (screen saver) timeout in 672ac0a314cSDaniel Xu seconds. A value of 0 disables the blank timer. 673ac0a314cSDaniel Xu Defaults to 0. 674e52347bdSJani Nikula 675e52347bdSJani Nikula coredump_filter= 676e52347bdSJani Nikula [KNL] Change the default value for 677e52347bdSJani Nikula /proc/<pid>/coredump_filter. 678e52347bdSJani Nikula See also Documentation/filesystems/proc.txt. 679e52347bdSJani Nikula 68062a31ce1SLeo Yan coresight_cpu_debug.enable 68162a31ce1SLeo Yan [ARM,ARM64] 68262a31ce1SLeo Yan Format: <bool> 68362a31ce1SLeo Yan Enable/disable the CPU sampling based debugging. 68462a31ce1SLeo Yan 0: default value, disable debugging 68562a31ce1SLeo Yan 1: enable debugging at boot time 68662a31ce1SLeo Yan 687e52347bdSJani Nikula cpuidle.off=1 [CPU_IDLE] 688e52347bdSJani Nikula disable the cpuidle sub-system 689e52347bdSJani Nikula 69061cb5758SRafael J. Wysocki cpuidle.governor= 69161cb5758SRafael J. Wysocki [CPU_IDLE] Name of the cpuidle governor to use. 69261cb5758SRafael J. Wysocki 693d82f2692SLen Brown cpufreq.off=1 [CPU_FREQ] 694d82f2692SLen Brown disable the cpufreq sub-system 695d82f2692SLen Brown 696e52347bdSJani Nikula cpu_init_udelay=N 697e52347bdSJani Nikula [X86] Delay for N microsec between assert and de-assert 698e52347bdSJani Nikula of APIC INIT to start processors. This delay occurs 699e52347bdSJani Nikula on every CPU online, such as boot, and resume from suspend. 700e52347bdSJani Nikula Default: 10000 701e52347bdSJani Nikula 702e52347bdSJani Nikula cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 703e52347bdSJani Nikula Format: 704e52347bdSJani Nikula <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 705e52347bdSJani Nikula 706e52347bdSJani Nikula crashkernel=size[KMG][@offset[KMG]] 707e52347bdSJani Nikula [KNL] Using kexec, Linux can switch to a 'crash kernel' 708e52347bdSJani Nikula upon panic. This parameter reserves the physical 709e52347bdSJani Nikula memory region [offset, offset + size] for that kernel 710e52347bdSJani Nikula image. If '@offset' is omitted, then a suitable offset 711b9ac3849SDave Young is selected automatically. 712b9ac3849SDave Young [KNL, x86_64] select a region under 4G first, and 713b9ac3849SDave Young fall back to reserve region above 4G when '@offset' 714b9ac3849SDave Young hasn't been specified. 715330d4810SMauro Carvalho Chehab See Documentation/admin-guide/kdump/kdump.rst for further details. 716e52347bdSJani Nikula 717e52347bdSJani Nikula crashkernel=range1:size1[,range2:size2,...][@offset] 718e52347bdSJani Nikula [KNL] Same as above, but depends on the memory 719e52347bdSJani Nikula in the running system. The syntax of range is 720e52347bdSJani Nikula start-[end] where start and end are both 721e52347bdSJani Nikula a memory unit (amount[KMG]). See also 722330d4810SMauro Carvalho Chehab Documentation/admin-guide/kdump/kdump.rst for an example. 723e52347bdSJani Nikula 724e52347bdSJani Nikula crashkernel=size[KMG],high 725e52347bdSJani Nikula [KNL, x86_64] range could be above 4G. Allow kernel 726e52347bdSJani Nikula to allocate physical memory region from top, so could 727e52347bdSJani Nikula be above 4G if system have more than 4G ram installed. 728e52347bdSJani Nikula Otherwise memory region will be allocated below 4G, if 729e52347bdSJani Nikula available. 730e52347bdSJani Nikula It will be ignored if crashkernel=X is specified. 731e52347bdSJani Nikula crashkernel=size[KMG],low 732e52347bdSJani Nikula [KNL, x86_64] range under 4G. When crashkernel=X,high 733e52347bdSJani Nikula is passed, kernel could allocate physical memory region 734e52347bdSJani Nikula above 4G, that cause second kernel crash on system 735e52347bdSJani Nikula that require some amount of low memory, e.g. swiotlb 736e52347bdSJani Nikula requires at least 64M+32K low memory, also enough extra 737e52347bdSJani Nikula low memory is needed to make sure DMA buffers for 32-bit 738e52347bdSJani Nikula devices won't run out. Kernel would try to allocate at 739e52347bdSJani Nikula at least 256M below 4G automatically. 740e52347bdSJani Nikula This one let user to specify own low range under 4G 741e52347bdSJani Nikula for second kernel instead. 742e52347bdSJani Nikula 0: to disable low allocation. 743e52347bdSJani Nikula It will be ignored when crashkernel=X,high is not used 744e52347bdSJani Nikula or memory reserved is below 4G. 745e52347bdSJani Nikula 746e52347bdSJani Nikula cryptomgr.notests 747e52347bdSJani Nikula [KNL] Disable crypto self-tests 748e52347bdSJani Nikula 749e52347bdSJani Nikula cs89x0_dma= [HW,NET] 750e52347bdSJani Nikula Format: <dma> 751e52347bdSJani Nikula 752e52347bdSJani Nikula cs89x0_media= [HW,NET] 753e52347bdSJani Nikula Format: { rj45 | aui | bnc } 754e52347bdSJani Nikula 755e52347bdSJani Nikula dasd= [HW,NET] 756e52347bdSJani Nikula See header of drivers/s390/block/dasd_devmap.c. 757e52347bdSJani Nikula 758e52347bdSJani Nikula db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 759e52347bdSJani Nikula (one device per port) 760e52347bdSJani Nikula Format: <port#>,<type> 7611752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 762e52347bdSJani Nikula 763e52347bdSJani Nikula ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot 764787e3075SSteffen Maier time. See 765787e3075SSteffen Maier Documentation/admin-guide/dynamic-debug-howto.rst for 766e52347bdSJani Nikula details. Deprecated, see dyndbg. 767e52347bdSJani Nikula 768e52347bdSJani Nikula debug [KNL] Enable kernel debugging (events log level). 769e52347bdSJani Nikula 7703672476eSTobin C. Harding debug_boot_weak_hash 7713672476eSTobin C. Harding [KNL] Enable printing [hashed] pointers early in the 7723672476eSTobin C. Harding boot sequence. If enabled, we use a weak hash instead 7733672476eSTobin C. Harding of siphash to hash pointers. Use this option if you are 7743672476eSTobin C. Harding seeing instances of '(___ptrval___)') and need to see a 7753672476eSTobin C. Harding value (hashed pointer) instead. Cryptographically 7763672476eSTobin C. Harding insecure, please do not use on production kernels. 7773672476eSTobin C. Harding 778e52347bdSJani Nikula debug_locks_verbose= 779e52347bdSJani Nikula [KNL] verbose self-tests 780e52347bdSJani Nikula Format=<0|1> 781e52347bdSJani Nikula Print debugging info while doing the locking API 782e52347bdSJani Nikula self-tests. 783e52347bdSJani Nikula We default to 0 (no extra messages), setting it to 784e52347bdSJani Nikula 1 will print _a lot_ more information - normally 785e52347bdSJani Nikula only useful to kernel developers. 786e52347bdSJani Nikula 787e52347bdSJani Nikula debug_objects [KNL] Enable object debugging 788e52347bdSJani Nikula 789e52347bdSJani Nikula no_debug_objects 790e52347bdSJani Nikula [KNL] Disable object debugging 791e52347bdSJani Nikula 792e52347bdSJani Nikula debug_guardpage_minorder= 793e52347bdSJani Nikula [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this 794e52347bdSJani Nikula parameter allows control of the order of pages that will 795e52347bdSJani Nikula be intentionally kept free (and hence protected) by the 796e52347bdSJani Nikula buddy allocator. Bigger value increase the probability 797e52347bdSJani Nikula of catching random memory corruption, but reduce the 798e52347bdSJani Nikula amount of memory for normal system use. The maximum 799e52347bdSJani Nikula possible value is MAX_ORDER/2. Setting this parameter 800e52347bdSJani Nikula to 1 or 2 should be enough to identify most random 801e52347bdSJani Nikula memory corruption problems caused by bugs in kernel or 802e52347bdSJani Nikula driver code when a CPU writes to (or reads from) a 803e52347bdSJani Nikula random memory location. Note that there exists a class 804e52347bdSJani Nikula of memory corruptions problems caused by buggy H/W or 805e52347bdSJani Nikula F/W or by drivers badly programing DMA (basically when 806e52347bdSJani Nikula memory is written at bus level and the CPU MMU is 807e52347bdSJani Nikula bypassed) which are not detectable by 808e52347bdSJani Nikula CONFIG_DEBUG_PAGEALLOC, hence this option will not help 809e52347bdSJani Nikula tracking down these problems. 810e52347bdSJani Nikula 811e52347bdSJani Nikula debug_pagealloc= 8123972f6bbSVlastimil Babka [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter 8133972f6bbSVlastimil Babka enables the feature at boot time. By default, it is 8143972f6bbSVlastimil Babka disabled and the system will work mostly the same as a 8153972f6bbSVlastimil Babka kernel built without CONFIG_DEBUG_PAGEALLOC. 8168974558fSVlastimil Babka Note: to get most of debug_pagealloc error reports, it's 8178974558fSVlastimil Babka useful to also enable the page_owner functionality. 818e52347bdSJani Nikula on: enable the feature 819e52347bdSJani Nikula 820e52347bdSJani Nikula debugpat [X86] Enable PAT debugging 821e52347bdSJani Nikula 822e52347bdSJani Nikula decnet.addr= [HW,NET] 823e52347bdSJani Nikula Format: <area>[,<node>] 824e52347bdSJani Nikula See also Documentation/networking/decnet.txt. 825e52347bdSJani Nikula 826e52347bdSJani Nikula default_hugepagesz= 827e52347bdSJani Nikula [same as hugepagesz=] The size of the default 828e52347bdSJani Nikula HugeTLB page size. This is the size represented by 829e52347bdSJani Nikula the legacy /proc/ hugepages APIs, used for SHM, and 830e52347bdSJani Nikula default size when mounting hugetlbfs filesystems. 831e52347bdSJani Nikula Defaults to the default architecture's huge page size 832e52347bdSJani Nikula if not specified. 833e52347bdSJani Nikula 83425b4e70dSRob Herring deferred_probe_timeout= 83525b4e70dSRob Herring [KNL] Debugging option to set a timeout in seconds for 83625b4e70dSRob Herring deferred probe to give up waiting on dependencies to 83725b4e70dSRob Herring probe. Only specific dependencies (subsystems or 83825b4e70dSRob Herring drivers) that have opted in will be ignored. A timeout of 0 83925b4e70dSRob Herring will timeout at the end of initcalls. This option will also 84025b4e70dSRob Herring dump out devices still on the deferred probe list after 84125b4e70dSRob Herring retrying. 84225b4e70dSRob Herring 843c65e6815SMikhail Zaslonko dfltcc= [HW,S390] 844c65e6815SMikhail Zaslonko Format: { on | off | def_only | inf_only | always } 845c65e6815SMikhail Zaslonko on: s390 zlib hardware support for compression on 846c65e6815SMikhail Zaslonko level 1 and decompression (default) 847c65e6815SMikhail Zaslonko off: No s390 zlib hardware support 848c65e6815SMikhail Zaslonko def_only: s390 zlib hardware support for deflate 849c65e6815SMikhail Zaslonko only (compression on level 1) 850c65e6815SMikhail Zaslonko inf_only: s390 zlib hardware support for inflate 851c65e6815SMikhail Zaslonko only (decompression) 852c65e6815SMikhail Zaslonko always: Same as 'on' but ignores the selected compression 853c65e6815SMikhail Zaslonko level always using hardware support (used for debugging) 854c65e6815SMikhail Zaslonko 855e52347bdSJani Nikula dhash_entries= [KNL] 856e52347bdSJani Nikula Set number of hash buckets for dentry cache. 857e52347bdSJani Nikula 858e52347bdSJani Nikula disable_1tb_segments [PPC] 859e52347bdSJani Nikula Disables the use of 1TB hash page table segments. This 860e52347bdSJani Nikula causes the kernel to fall back to 256MB segments which 861e52347bdSJani Nikula can be useful when debugging issues that require an SLB 862e52347bdSJani Nikula miss to occur. 863e52347bdSJani Nikula 864e52347bdSJani Nikula disable= [IPV6] 865e52347bdSJani Nikula See Documentation/networking/ipv6.txt. 866e52347bdSJani Nikula 867b5cb15d9SChris von Recklinghausen hardened_usercopy= 868b5cb15d9SChris von Recklinghausen [KNL] Under CONFIG_HARDENED_USERCOPY, whether 869b5cb15d9SChris von Recklinghausen hardening is enabled for this boot. Hardened 870b5cb15d9SChris von Recklinghausen usercopy checking is used to protect the kernel 871b5cb15d9SChris von Recklinghausen from reading or writing beyond known memory 872b5cb15d9SChris von Recklinghausen allocation boundaries as a proactive defense 873b5cb15d9SChris von Recklinghausen against bounds-checking flaws in the kernel's 874b5cb15d9SChris von Recklinghausen copy_to_user()/copy_from_user() interface. 875b5cb15d9SChris von Recklinghausen on Perform hardened usercopy checks (default). 876b5cb15d9SChris von Recklinghausen off Disable hardened usercopy checks. 877b5cb15d9SChris von Recklinghausen 878e52347bdSJani Nikula disable_radix [PPC] 879e52347bdSJani Nikula Disable RADIX MMU mode on POWER9 880e52347bdSJani Nikula 8812275d7b5SNicholas Piggin disable_tlbie [PPC] 8822275d7b5SNicholas Piggin Disable TLBIE instruction. Currently does not work 8832275d7b5SNicholas Piggin with KVM, with HASH MMU, or with coherent accelerators. 8842275d7b5SNicholas Piggin 885e52347bdSJani Nikula disable_cpu_apicid= [X86,APIC,SMP] 886e52347bdSJani Nikula Format: <int> 887e52347bdSJani Nikula The number of initial APIC ID for the 888e52347bdSJani Nikula corresponding CPU to be disabled at boot, 889e52347bdSJani Nikula mostly used for the kdump 2nd kernel to 890e52347bdSJani Nikula disable BSP to wake up multiple CPUs without 891e52347bdSJani Nikula causing system reset or hang due to sending 892e52347bdSJani Nikula INIT from AP to BSP. 893e52347bdSJani Nikula 8942a5bf23dSPeter Zijlstra perf_v4_pmi= [X86,INTEL] 8952a5bf23dSPeter Zijlstra Format: <bool> 896af3bdb99SAndi Kleen Disable Intel PMU counter freezing feature. 897af3bdb99SAndi Kleen The feature only exists starting from 898af3bdb99SAndi Kleen Arch Perfmon v4 (Skylake and newer). 899af3bdb99SAndi Kleen 900e52347bdSJani Nikula disable_ddw [PPC/PSERIES] 901e52347bdSJani Nikula Disable Dynamic DMA Window support. Use this if 902e52347bdSJani Nikula to workaround buggy firmware. 903e52347bdSJani Nikula 904e52347bdSJani Nikula disable_ipv6= [IPV6] 905e52347bdSJani Nikula See Documentation/networking/ipv6.txt. 906e52347bdSJani Nikula 907e52347bdSJani Nikula disable_mtrr_cleanup [X86] 908e52347bdSJani Nikula The kernel tries to adjust MTRR layout from continuous 909e52347bdSJani Nikula to discrete, to make X server driver able to add WB 910e52347bdSJani Nikula entry later. This parameter disables that. 911e52347bdSJani Nikula 912e52347bdSJani Nikula disable_mtrr_trim [X86, Intel and AMD only] 913e52347bdSJani Nikula By default the kernel will trim any uncacheable 914e52347bdSJani Nikula memory out of your available memory pool based on 915e52347bdSJani Nikula MTRR settings. This parameter disables that behavior, 916e52347bdSJani Nikula possibly causing your machine to run very slowly. 917e52347bdSJani Nikula 918e52347bdSJani Nikula disable_timer_pin_1 [X86] 919e52347bdSJani Nikula Disable PIN 1 of APIC timer 920e52347bdSJani Nikula Can be useful to work around chipset bugs. 921e52347bdSJani Nikula 922e52347bdSJani Nikula dis_ucode_ldr [X86] Disable the microcode loader. 923e52347bdSJani Nikula 924e52347bdSJani Nikula dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, 925e52347bdSJani Nikula this option disables the debugging code at boot. 926e52347bdSJani Nikula 927e52347bdSJani Nikula dma_debug_entries=<number> 928e52347bdSJani Nikula This option allows to tune the number of preallocated 929e52347bdSJani Nikula entries for DMA-API debugging code. One entry is 930e52347bdSJani Nikula required per DMA-API allocation. Use this if the 931e52347bdSJani Nikula DMA-API debugging code disables itself because the 932e52347bdSJani Nikula architectural default is too low. 933e52347bdSJani Nikula 934e52347bdSJani Nikula dma_debug_driver=<driver_name> 935e52347bdSJani Nikula With this option the DMA-API debugging driver 936e52347bdSJani Nikula filter feature can be enabled at boot time. Just 937e52347bdSJani Nikula pass the driver to filter for as the parameter. 938e52347bdSJani Nikula The filter can be disabled or changed to another 939e52347bdSJani Nikula driver later using sysfs. 940e52347bdSJani Nikula 9411ea61b68SFeng Tang driver_async_probe= [KNL] 9421ea61b68SFeng Tang List of driver names to be probed asynchronously. 9431ea61b68SFeng Tang Format: <driver_name1>,<driver_name2>... 9441ea61b68SFeng Tang 94553fd40a9SJani Nikula drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] 946e52347bdSJani Nikula Broken monitors, graphic adapters, KVMs and EDIDless 947e52347bdSJani Nikula panels may send no or incorrect EDID data sets. 948e52347bdSJani Nikula This parameter allows to specify an EDID data sets 949e52347bdSJani Nikula in the /lib/firmware directory that are used instead. 950e52347bdSJani Nikula Generic built-in EDID data sets are used, if one of 951e52347bdSJani Nikula edid/1024x768.bin, edid/1280x1024.bin, 952e52347bdSJani Nikula edid/1680x1050.bin, or edid/1920x1080.bin is given 953e52347bdSJani Nikula and no file with the same name exists. Details and 954e52347bdSJani Nikula instructions how to build your own EDID data are 955baa293e9SMauro Carvalho Chehab available in Documentation/driver-api/edid.rst. An EDID 956e52347bdSJani Nikula data set will only be used for a particular connector, 957e52347bdSJani Nikula if its name and a colon are prepended to the EDID 958e52347bdSJani Nikula name. Each connector may use a unique EDID data 959e52347bdSJani Nikula set by separating the files with a comma. An EDID 960e52347bdSJani Nikula data set with no connector name will be used for 961e52347bdSJani Nikula any connectors not explicitly specified. 962e52347bdSJani Nikula 963e52347bdSJani Nikula dscc4.setup= [NET] 964e52347bdSJani Nikula 965a2b05b7aSNicholas Piggin dt_cpu_ftrs= [PPC] 966a2b05b7aSNicholas Piggin Format: {"off" | "known"} 967a2b05b7aSNicholas Piggin Control how the dt_cpu_ftrs device-tree binding is 968a2b05b7aSNicholas Piggin used for CPU feature discovery and setup (if it 969a2b05b7aSNicholas Piggin exists). 970a2b05b7aSNicholas Piggin off: Do not use it, fall back to legacy cpu table. 971a2b05b7aSNicholas Piggin known: Do not pass through unknown features to guests 972a2b05b7aSNicholas Piggin or userspace, only those that the kernel is aware of. 973a2b05b7aSNicholas Piggin 974e7aa8c2eSLinus Torvalds dump_apple_properties [X86] 975e7aa8c2eSLinus Torvalds Dump name and content of EFI device properties on 976e7aa8c2eSLinus Torvalds x86 Macs. Useful for driver authors to determine 977e7aa8c2eSLinus Torvalds what data is available or for reverse-engineering. 978e7aa8c2eSLinus Torvalds 979e52347bdSJani Nikula dyndbg[="val"] [KNL,DYNAMIC_DEBUG] 980e52347bdSJani Nikula module.dyndbg[="val"] 981e52347bdSJani Nikula Enable debug messages at boot time. See 982787e3075SSteffen Maier Documentation/admin-guide/dynamic-debug-howto.rst 983787e3075SSteffen Maier for details. 984e52347bdSJani Nikula 985e52347bdSJani Nikula nompx [X86] Disables Intel Memory Protection Extensions. 986cb1aaebeSMauro Carvalho Chehab See Documentation/x86/intel_mpx.rst for more 987e52347bdSJani Nikula information about the feature. 988e52347bdSJani Nikula 989e52347bdSJani Nikula nopku [X86] Disable Memory Protection Keys CPU feature found 990e52347bdSJani Nikula in some Intel CPUs. 991e52347bdSJani Nikula 992e52347bdSJani Nikula module.async_probe [KNL] 993e52347bdSJani Nikula Enable asynchronous probe on this module. 994e52347bdSJani Nikula 995e52347bdSJani Nikula early_ioremap_debug [KNL] 996e52347bdSJani Nikula Enable debug messages in early_ioremap support. This 997e52347bdSJani Nikula is useful for tracking down temporary early mappings 998e52347bdSJani Nikula which are not unmapped. 999e52347bdSJani Nikula 1000e52347bdSJani Nikula earlycon= [KNL] Output early console device and options. 1001e52347bdSJani Nikula 1002e18409c0SChristoph Hellwig When used with no options, the early console is 1003e18409c0SChristoph Hellwig determined by stdout-path property in device tree's 1004e18409c0SChristoph Hellwig chosen node or the ACPI SPCR table if supported by 1005e18409c0SChristoph Hellwig the platform. 1006e52347bdSJani Nikula 1007e52347bdSJani Nikula cdns,<addr>[,options] 1008e52347bdSJani Nikula Start an early, polled-mode console on a Cadence 1009e52347bdSJani Nikula (xuartps) serial port at the specified address. Only 1010e52347bdSJani Nikula supported option is baud rate. If baud rate is not 1011e52347bdSJani Nikula specified, the serial port must already be setup and 1012e52347bdSJani Nikula configured. 1013e52347bdSJani Nikula 1014e52347bdSJani Nikula uart[8250],io,<addr>[,options] 1015e52347bdSJani Nikula uart[8250],mmio,<addr>[,options] 1016e52347bdSJani Nikula uart[8250],mmio32,<addr>[,options] 1017e52347bdSJani Nikula uart[8250],mmio32be,<addr>[,options] 1018e52347bdSJani Nikula uart[8250],0x<addr>[,options] 1019e52347bdSJani Nikula Start an early, polled-mode console on the 8250/16550 1020e52347bdSJani Nikula UART at the specified I/O port or MMIO address. 1021e52347bdSJani Nikula MMIO inter-register address stride is either 8-bit 1022e52347bdSJani Nikula (mmio) or 32-bit (mmio32 or mmio32be). 1023e52347bdSJani Nikula If none of [io|mmio|mmio32|mmio32be], <addr> is assumed 1024e52347bdSJani Nikula to be equivalent to 'mmio'. 'options' are specified 1025e52347bdSJani Nikula in the same format described for "console=ttyS<n>"; if 1026e52347bdSJani Nikula unspecified, the h/w is not initialized. 1027e52347bdSJani Nikula 1028e52347bdSJani Nikula pl011,<addr> 1029e52347bdSJani Nikula pl011,mmio32,<addr> 1030e52347bdSJani Nikula Start an early, polled-mode console on a pl011 serial 1031e52347bdSJani Nikula port at the specified address. The pl011 serial port 1032e52347bdSJani Nikula must already be setup and configured. Options are not 1033e52347bdSJani Nikula yet supported. If 'mmio32' is specified, then only 1034e52347bdSJani Nikula the driver will use only 32-bit accessors to read/write 1035e52347bdSJani Nikula the device registers. 1036e52347bdSJani Nikula 1037e52347bdSJani Nikula meson,<addr> 1038e52347bdSJani Nikula Start an early, polled-mode console on a meson serial 1039e52347bdSJani Nikula port at the specified address. The serial port must 1040e52347bdSJani Nikula already be setup and configured. Options are not yet 1041e52347bdSJani Nikula supported. 1042e52347bdSJani Nikula 1043e52347bdSJani Nikula msm_serial,<addr> 1044e52347bdSJani Nikula Start an early, polled-mode console on an msm serial 1045e52347bdSJani Nikula port at the specified address. The serial port 1046e52347bdSJani Nikula must already be setup and configured. Options are not 1047e52347bdSJani Nikula yet supported. 1048e52347bdSJani Nikula 1049e52347bdSJani Nikula msm_serial_dm,<addr> 1050e52347bdSJani Nikula Start an early, polled-mode console on an msm serial 1051e52347bdSJani Nikula dm port at the specified address. The serial port 1052e52347bdSJani Nikula must already be setup and configured. Options are not 1053e52347bdSJani Nikula yet supported. 1054e52347bdSJani Nikula 1055e36361d7SAndreas Färber owl,<addr> 1056e36361d7SAndreas Färber Start an early, polled-mode console on a serial port 1057e36361d7SAndreas Färber of an Actions Semi SoC, such as S500 or S900, at the 1058e36361d7SAndreas Färber specified address. The serial port must already be 1059e36361d7SAndreas Färber setup and configured. Options are not yet supported. 1060e36361d7SAndreas Färber 1061c10b1332SManivannan Sadhasivam rda,<addr> 1062c10b1332SManivannan Sadhasivam Start an early, polled-mode console on a serial port 1063c10b1332SManivannan Sadhasivam of an RDA Micro SoC, such as RDA8810PL, at the 1064c10b1332SManivannan Sadhasivam specified address. The serial port must already be 1065c10b1332SManivannan Sadhasivam setup and configured. Options are not yet supported. 1066c10b1332SManivannan Sadhasivam 106782f12ab3SPalmer Dabbelt sbi 106882f12ab3SPalmer Dabbelt Use RISC-V SBI (Supervisor Binary Interface) for early 106982f12ab3SPalmer Dabbelt console. 107082f12ab3SPalmer Dabbelt 1071e52347bdSJani Nikula smh Use ARM semihosting calls for early console. 1072e52347bdSJani Nikula 1073e52347bdSJani Nikula s3c2410,<addr> 1074e52347bdSJani Nikula s3c2412,<addr> 1075e52347bdSJani Nikula s3c2440,<addr> 1076e52347bdSJani Nikula s3c6400,<addr> 1077e52347bdSJani Nikula s5pv210,<addr> 1078e52347bdSJani Nikula exynos4210,<addr> 1079e52347bdSJani Nikula Use early console provided by serial driver available 1080e52347bdSJani Nikula on Samsung SoCs, requires selecting proper type and 1081e52347bdSJani Nikula a correct base address of the selected UART port. The 1082e52347bdSJani Nikula serial port must already be setup and configured. 1083e52347bdSJani Nikula Options are not yet supported. 1084e52347bdSJani Nikula 1085ec84aa0aSMartin Blumenstingl lantiq,<addr> 1086ec84aa0aSMartin Blumenstingl Start an early, polled-mode console on a lantiq serial 1087ec84aa0aSMartin Blumenstingl (lqasc) port at the specified address. The serial port 1088ec84aa0aSMartin Blumenstingl must already be setup and configured. Options are not 1089ec84aa0aSMartin Blumenstingl yet supported. 1090ec84aa0aSMartin Blumenstingl 1091e52347bdSJani Nikula lpuart,<addr> 1092e52347bdSJani Nikula lpuart32,<addr> 1093e52347bdSJani Nikula Use early console provided by Freescale LP UART driver 1094e52347bdSJani Nikula found on Freescale Vybrid and QorIQ LS1021A processors. 1095e52347bdSJani Nikula A valid base address must be provided, and the serial 1096e52347bdSJani Nikula port must already be setup and configured. 1097e52347bdSJani Nikula 1098f7c864e7SAndre Przywara ar3700_uart,<addr> 1099e52347bdSJani Nikula Start an early, polled-mode console on the 1100e52347bdSJani Nikula Armada 3700 serial port at the specified 1101e52347bdSJani Nikula address. The serial port must already be setup 1102e52347bdSJani Nikula and configured. Options are not yet supported. 1103e52347bdSJani Nikula 110443f1831bSKarthikeyan Ramasubramanian qcom_geni,<addr> 110543f1831bSKarthikeyan Ramasubramanian Start an early, polled-mode console on a Qualcomm 110643f1831bSKarthikeyan Ramasubramanian Generic Interface (GENI) based serial port at the 110743f1831bSKarthikeyan Ramasubramanian specified address. The serial port must already be 110843f1831bSKarthikeyan Ramasubramanian setup and configured. Options are not yet supported. 110943f1831bSKarthikeyan Ramasubramanian 111069c1f396SArd Biesheuvel efifb,[options] 111169c1f396SArd Biesheuvel Start an early, unaccelerated console on the EFI 111269c1f396SArd Biesheuvel memory mapped framebuffer (if available). On cache 111369c1f396SArd Biesheuvel coherent non-x86 systems that use system memory for 111469c1f396SArd Biesheuvel the framebuffer, pass the 'ram' option so that it is 111569c1f396SArd Biesheuvel mapped with the correct attributes. 111669c1f396SArd Biesheuvel 111709864c1cSStefan-gabriel Mirea linflex,<addr> 11189905f32aSStefan-Gabriel Mirea Use early console provided by Freescale LINFlexD UART 111909864c1cSStefan-gabriel Mirea serial driver for NXP S32V234 SoCs. A valid base 112009864c1cSStefan-gabriel Mirea address must be provided, and the serial port must 112109864c1cSStefan-gabriel Mirea already be setup and configured. 112209864c1cSStefan-gabriel Mirea 11234ba66a97SArnd Bergmann earlyprintk= [X86,SH,ARM,M68k,S390] 1124e52347bdSJani Nikula earlyprintk=vga 112589175cf7SHeiko Carstens earlyprintk=sclp 1126e52347bdSJani Nikula earlyprintk=xen 1127e52347bdSJani Nikula earlyprintk=serial[,ttySn[,baudrate]] 1128e52347bdSJani Nikula earlyprintk=serial[,0x...[,baudrate]] 1129e52347bdSJani Nikula earlyprintk=ttySn[,baudrate] 1130e52347bdSJani Nikula earlyprintk=dbgp[debugController#] 1131d2266bbfSFeng Tang earlyprintk=pciserial[,force],bus:device.function[,baudrate] 11321b5aeebfSLu Baolu earlyprintk=xdbc[xhciController#] 1133e52347bdSJani Nikula 1134e52347bdSJani Nikula earlyprintk is useful when the kernel crashes before 1135e52347bdSJani Nikula the normal console is initialized. It is not enabled by 1136e52347bdSJani Nikula default because it has some cosmetic problems. 1137e52347bdSJani Nikula 1138e52347bdSJani Nikula Append ",keep" to not disable it when the real console 1139e52347bdSJani Nikula takes over. 1140e52347bdSJani Nikula 1141e52347bdSJani Nikula Only one of vga, efi, serial, or usb debug port can 1142e52347bdSJani Nikula be used at a time. 1143e52347bdSJani Nikula 1144e52347bdSJani Nikula Currently only ttyS0 and ttyS1 may be specified by 1145e52347bdSJani Nikula name. Other I/O ports may be explicitly specified 1146e52347bdSJani Nikula on some architectures (x86 and arm at least) by 1147e52347bdSJani Nikula replacing ttySn with an I/O port address, like this: 1148e52347bdSJani Nikula earlyprintk=serial,0x1008,115200 1149e52347bdSJani Nikula You can find the port for a given device in 1150e52347bdSJani Nikula /proc/tty/driver/serial: 1151e52347bdSJani Nikula 2: uart:ST16650V2 port:00001008 irq:18 ... 1152e52347bdSJani Nikula 1153e52347bdSJani Nikula Interaction with the standard serial driver is not 1154e52347bdSJani Nikula very good. 1155e52347bdSJani Nikula 1156e52347bdSJani Nikula The VGA and EFI output is eventually overwritten by 1157e52347bdSJani Nikula the real console. 1158e52347bdSJani Nikula 1159e52347bdSJani Nikula The xen output can only be used by Xen PV guests. 1160e52347bdSJani Nikula 116189175cf7SHeiko Carstens The sclp output can only be used on s390. 116289175cf7SHeiko Carstens 1163d2266bbfSFeng Tang The optional "force" to "pciserial" enables use of a 1164d2266bbfSFeng Tang PCI device even when its classcode is not of the 1165d2266bbfSFeng Tang UART class. 1166d2266bbfSFeng Tang 1167e52347bdSJani Nikula edac_report= [HW,EDAC] Control how to report EDAC event 1168e52347bdSJani Nikula Format: {"on" | "off" | "force"} 1169e52347bdSJani Nikula on: enable EDAC to report H/W event. May be overridden 1170e52347bdSJani Nikula by other higher priority error reporting module. 1171e52347bdSJani Nikula off: disable H/W event reporting through EDAC. 1172e52347bdSJani Nikula force: enforce the use of EDAC to report H/W event. 1173e52347bdSJani Nikula default: on. 1174e52347bdSJani Nikula 1175e52347bdSJani Nikula ekgdboc= [X86,KGDB] Allow early kernel console debugging 1176e52347bdSJani Nikula ekgdboc=kbd 1177e52347bdSJani Nikula 1178e52347bdSJani Nikula This is designed to be used in conjunction with 1179e52347bdSJani Nikula the boot argument: earlyprintk=vga 1180e52347bdSJani Nikula 1181e52347bdSJani Nikula edd= [EDD] 1182e52347bdSJani Nikula Format: {"off" | "on" | "skip[mbr]"} 1183e52347bdSJani Nikula 1184e52347bdSJani Nikula efi= [EFI] 1185b617c526SDan Williams Format: { "old_map", "nochunk", "noruntime", "debug", 11864444f854SMatthew Garrett "nosoftreserve", "disable_early_pci_dma", 11874444f854SMatthew Garrett "no_disable_early_pci_dma" } 1188e52347bdSJani Nikula old_map [X86-64]: switch to the old ioremap-based EFI 11891f299fadSArd Biesheuvel runtime services mapping. [Needs CONFIG_X86_UV=y] 1190e52347bdSJani Nikula nochunk: disable reading files in "chunks" in the EFI 1191e52347bdSJani Nikula boot stub, as chunking can cause problems with some 1192e52347bdSJani Nikula firmware implementations. 1193e52347bdSJani Nikula noruntime : disable EFI runtime services support 1194e52347bdSJani Nikula debug: enable misc debug output 1195b617c526SDan Williams nosoftreserve: The EFI_MEMORY_SP (Specific Purpose) 1196b617c526SDan Williams attribute may cause the kernel to reserve the 1197b617c526SDan Williams memory range for a memory mapping driver to 1198b617c526SDan Williams claim. Specify efi=nosoftreserve to disable this 1199b617c526SDan Williams reservation and treat the memory by its base type 1200b617c526SDan Williams (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM"). 12014444f854SMatthew Garrett disable_early_pci_dma: Disable the busmaster bit on all 12024444f854SMatthew Garrett PCI bridges while in the EFI boot stub 12034444f854SMatthew Garrett no_disable_early_pci_dma: Leave the busmaster bit set 12044444f854SMatthew Garrett on all PCI bridges while in the EFI boot stub 1205e52347bdSJani Nikula 1206e52347bdSJani Nikula efi_no_storage_paranoia [EFI; X86] 1207e52347bdSJani Nikula Using this parameter you can use more than 50% of 1208e52347bdSJani Nikula your efi variable storage. Use this parameter only if 1209e52347bdSJani Nikula you are really sure that your UEFI does sane gc and 1210e52347bdSJani Nikula fulfills the spec otherwise your board may brick. 1211e52347bdSJani Nikula 1212e52347bdSJani Nikula efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] 1213e52347bdSJani Nikula Add arbitrary attribute to specific memory range by 1214e52347bdSJani Nikula updating original EFI memory map. 1215e52347bdSJani Nikula Region of memory which aa attribute is added to is 1216e52347bdSJani Nikula from ss to ss+nn. 1217199c8471SDan Williams 1218e52347bdSJani Nikula If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 1219e52347bdSJani Nikula is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) 1220e52347bdSJani Nikula attribute is added to range 0x100000000-0x180000000 and 1221e52347bdSJani Nikula 0x10a0000000-0x1120000000. 1222e52347bdSJani Nikula 1223199c8471SDan Williams If efi_fake_mem=8G@9G:0x40000 is specified, the 1224199c8471SDan Williams EFI_MEMORY_SP(0x40000) attribute is added to 1225199c8471SDan Williams range 0x240000000-0x43fffffff. 1226199c8471SDan Williams 1227e52347bdSJani Nikula Using this parameter you can do debugging of EFI memmap 1228199c8471SDan Williams related features. For example, you can do debugging of 1229e52347bdSJani Nikula Address Range Mirroring feature even if your box 1230199c8471SDan Williams doesn't support it, or mark specific memory as 1231199c8471SDan Williams "soft reserved". 1232e52347bdSJani Nikula 1233e52347bdSJani Nikula efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT 1234e52347bdSJani Nikula that is to be dynamically loaded by Linux. If there are 1235e52347bdSJani Nikula multiple variables with the same name but with different 1236e52347bdSJani Nikula vendor GUIDs, all of them will be loaded. See 1237cb1aaebeSMauro Carvalho Chehab Documentation/admin-guide/acpi/ssdt-overlays.rst for details. 1238e52347bdSJani Nikula 1239e52347bdSJani Nikula 1240e52347bdSJani Nikula eisa_irq_edge= [PARISC,HW] 1241e52347bdSJani Nikula See header of drivers/parisc/eisa.c. 1242e52347bdSJani Nikula 1243e52347bdSJani Nikula elanfreq= [X86-32] 1244e52347bdSJani Nikula See comment before function elanfreq_setup() in 1245e52347bdSJani Nikula arch/x86/kernel/cpu/cpufreq/elanfreq.c. 1246e52347bdSJani Nikula 1247e52347bdSJani Nikula elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] 1248e52347bdSJani Nikula Specifies physical address of start of kernel core 1249e52347bdSJani Nikula image elf header and optionally the size. Generally 1250e52347bdSJani Nikula kexec loader will pass this option to capture kernel. 1251330d4810SMauro Carvalho Chehab See Documentation/admin-guide/kdump/kdump.rst for details. 1252e52347bdSJani Nikula 1253e52347bdSJani Nikula enable_mtrr_cleanup [X86] 1254e52347bdSJani Nikula The kernel tries to adjust MTRR layout from continuous 1255e52347bdSJani Nikula to discrete, to make X server driver able to add WB 1256e52347bdSJani Nikula entry later. This parameter enables that. 1257e52347bdSJani Nikula 1258e52347bdSJani Nikula enable_timer_pin_1 [X86] 1259e52347bdSJani Nikula Enable PIN 1 of APIC timer 1260e52347bdSJani Nikula Can be useful to work around chipset bugs 1261e52347bdSJani Nikula (in particular on some ATI chipsets). 1262e52347bdSJani Nikula The kernel tries to set a reasonable default. 1263e52347bdSJani Nikula 1264e52347bdSJani Nikula enforcing [SELINUX] Set initial enforcing status. 1265e52347bdSJani Nikula Format: {"0" | "1"} 1266e52347bdSJani Nikula See security/selinux/Kconfig help text. 1267e52347bdSJani Nikula 0 -- permissive (log only, no denials). 1268e52347bdSJani Nikula 1 -- enforcing (deny and log). 1269e52347bdSJani Nikula Default value is 0. 1270d41415ebSStephen Smalley Value can be changed at runtime via 1271d41415ebSStephen Smalley /sys/fs/selinux/enforce. 1272e52347bdSJani Nikula 1273e52347bdSJani Nikula erst_disable [ACPI] 1274e52347bdSJani Nikula Disable Error Record Serialization Table (ERST) 1275e52347bdSJani Nikula support. 1276e52347bdSJani Nikula 1277e52347bdSJani Nikula ether= [HW,NET] Ethernet cards parameters 1278e52347bdSJani Nikula This option is obsoleted by the "netdev=" option, which 1279e52347bdSJani Nikula has equivalent usage. See its documentation for details. 1280e52347bdSJani Nikula 1281e52347bdSJani Nikula evm= [EVM] 1282e52347bdSJani Nikula Format: { "fix" } 1283e52347bdSJani Nikula Permit 'security.evm' to be updated regardless of 1284e52347bdSJani Nikula current integrity status. 1285e52347bdSJani Nikula 1286e52347bdSJani Nikula failslab= 1287e52347bdSJani Nikula fail_page_alloc= 1288e52347bdSJani Nikula fail_make_request=[KNL] 1289e52347bdSJani Nikula General fault injection mechanism. 1290e52347bdSJani Nikula Format: <interval>,<probability>,<space>,<times> 1291e52347bdSJani Nikula See also Documentation/fault-injection/. 1292e52347bdSJani Nikula 1293e52347bdSJani Nikula floppy= [HW] 1294e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/floppy.rst. 1295e52347bdSJani Nikula 1296e52347bdSJani Nikula force_pal_cache_flush 1297e52347bdSJani Nikula [IA-64] Avoid check_sal_cache_flush which may hang on 1298e52347bdSJani Nikula buggy SAL_CACHE_FLUSH implementations. Using this 1299e52347bdSJani Nikula parameter will force ia64_sal_cache_flush to call 1300e52347bdSJani Nikula ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 1301e52347bdSJani Nikula 1302e52347bdSJani Nikula forcepae [X86-32] 1303e52347bdSJani Nikula Forcefully enable Physical Address Extension (PAE). 1304e52347bdSJani Nikula Many Pentium M systems disable PAE but may have a 1305e52347bdSJani Nikula functionally usable PAE implementation. 1306e52347bdSJani Nikula Warning: use of this parameter will taint the kernel 1307e52347bdSJani Nikula and may cause unknown problems. 1308e52347bdSJani Nikula 1309e52347bdSJani Nikula ftrace=[tracer] 1310e52347bdSJani Nikula [FTRACE] will set and start the specified tracer 1311e52347bdSJani Nikula as early as possible in order to facilitate early 1312e52347bdSJani Nikula boot debugging. 1313e52347bdSJani Nikula 1314e52347bdSJani Nikula ftrace_dump_on_oops[=orig_cpu] 1315e52347bdSJani Nikula [FTRACE] will dump the trace buffers on oops. 1316e52347bdSJani Nikula If no parameter is passed, ftrace will dump 1317e52347bdSJani Nikula buffers of all CPUs, but if you pass orig_cpu, it will 1318e52347bdSJani Nikula dump only the buffer of the CPU that triggered the 1319e52347bdSJani Nikula oops. 1320e52347bdSJani Nikula 1321e52347bdSJani Nikula ftrace_filter=[function-list] 1322e52347bdSJani Nikula [FTRACE] Limit the functions traced by the function 1323e52347bdSJani Nikula tracer at boot up. function-list is a comma separated 1324e52347bdSJani Nikula list of functions. This list can be changed at run 1325e52347bdSJani Nikula time by the set_ftrace_filter file in the debugfs 1326e52347bdSJani Nikula tracing directory. 1327e52347bdSJani Nikula 1328e52347bdSJani Nikula ftrace_notrace=[function-list] 1329e52347bdSJani Nikula [FTRACE] Do not trace the functions specified in 1330e52347bdSJani Nikula function-list. This list can be changed at run time 1331e52347bdSJani Nikula by the set_ftrace_notrace file in the debugfs 1332e52347bdSJani Nikula tracing directory. 1333e52347bdSJani Nikula 1334e52347bdSJani Nikula ftrace_graph_filter=[function-list] 1335e52347bdSJani Nikula [FTRACE] Limit the top level callers functions traced 1336e52347bdSJani Nikula by the function graph tracer at boot up. 1337e52347bdSJani Nikula function-list is a comma separated list of functions 1338e52347bdSJani Nikula that can be changed at run time by the 1339e52347bdSJani Nikula set_graph_function file in the debugfs tracing directory. 1340e52347bdSJani Nikula 1341e52347bdSJani Nikula ftrace_graph_notrace=[function-list] 1342e52347bdSJani Nikula [FTRACE] Do not trace from the functions specified in 1343e52347bdSJani Nikula function-list. This list is a comma separated list of 1344e52347bdSJani Nikula functions that can be changed at run time by the 1345e52347bdSJani Nikula set_graph_notrace file in the debugfs tracing directory. 1346e52347bdSJani Nikula 134765a50c65STodd Brandt ftrace_graph_max_depth=<uint> 134865a50c65STodd Brandt [FTRACE] Used with the function graph tracer. This is 134965a50c65STodd Brandt the max depth it will trace into a function. This value 135065a50c65STodd Brandt can be changed at run time by the max_graph_depth file 135165a50c65STodd Brandt in the tracefs tracing directory. default: 0 (no limit) 135265a50c65STodd Brandt 1353e52347bdSJani Nikula gamecon.map[2|3]= 1354e52347bdSJani Nikula [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 1355e52347bdSJani Nikula support via parallel port (up to 5 devices per port) 1356e52347bdSJani Nikula Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 13571752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 1358e52347bdSJani Nikula 1359e52347bdSJani Nikula gamma= [HW,DRM] 1360e52347bdSJani Nikula 1361e52347bdSJani Nikula gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 1362e52347bdSJani Nikula Format: off | on 1363e52347bdSJani Nikula default: on 1364e52347bdSJani Nikula 1365e52347bdSJani Nikula gcov_persist= [GCOV] When non-zero (default), profiling data for 1366e52347bdSJani Nikula kernel modules is saved and remains accessible via 1367e52347bdSJani Nikula debugfs, even when the module is unloaded/reloaded. 1368e52347bdSJani Nikula When zero, profiling data is discarded and associated 1369e52347bdSJani Nikula debugfs files are removed at module unload time. 1370e52347bdSJani Nikula 137147512cfdSThomas Gleixner goldfish [X86] Enable the goldfish android emulator platform. 137247512cfdSThomas Gleixner Don't use this when you are not running on the 137347512cfdSThomas Gleixner android emulator 137447512cfdSThomas Gleixner 1375e52347bdSJani Nikula gpt [EFI] Forces disk with valid GPT signature but 1376e52347bdSJani Nikula invalid Protective MBR to be treated as GPT. If the 1377e52347bdSJani Nikula primary GPT is corrupted, it enables the backup/alternate 1378e52347bdSJani Nikula GPT to be used instead. 1379e52347bdSJani Nikula 1380e52347bdSJani Nikula grcan.enable0= [HW] Configuration of physical interface 0. Determines 1381e52347bdSJani Nikula the "Enable 0" bit of the configuration register. 1382e52347bdSJani Nikula Format: 0 | 1 1383e52347bdSJani Nikula Default: 0 1384e52347bdSJani Nikula grcan.enable1= [HW] Configuration of physical interface 1. Determines 1385e52347bdSJani Nikula the "Enable 0" bit of the configuration register. 1386e52347bdSJani Nikula Format: 0 | 1 1387e52347bdSJani Nikula Default: 0 1388e52347bdSJani Nikula grcan.select= [HW] Select which physical interface to use. 1389e52347bdSJani Nikula Format: 0 | 1 1390e52347bdSJani Nikula Default: 0 1391e52347bdSJani Nikula grcan.txsize= [HW] Sets the size of the tx buffer. 1392e52347bdSJani Nikula Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0. 1393e52347bdSJani Nikula Default: 1024 1394e52347bdSJani Nikula grcan.rxsize= [HW] Sets the size of the rx buffer. 1395e52347bdSJani Nikula Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. 1396e52347bdSJani Nikula Default: 1024 1397e52347bdSJani Nikula 1398e52347bdSJani Nikula gpio-mockup.gpio_mockup_ranges 1399e52347bdSJani Nikula [HW] Sets the ranges of gpiochip of for this device. 1400e52347bdSJani Nikula Format: <start1>,<end1>,<start2>,<end2>... 1401e52347bdSJani Nikula 1402e52347bdSJani Nikula hardlockup_all_cpu_backtrace= 1403e52347bdSJani Nikula [KNL] Should the hard-lockup detector generate 1404e52347bdSJani Nikula backtraces on all cpus. 1405e52347bdSJani Nikula Format: <integer> 1406e52347bdSJani Nikula 1407e52347bdSJani Nikula hashdist= [KNL,NUMA] Large hashes allocated during boot 1408e52347bdSJani Nikula are distributed across NUMA nodes. Defaults on 1409e52347bdSJani Nikula for 64-bit NUMA, off otherwise. 1410e52347bdSJani Nikula Format: 0 | 1 (for off | on) 1411e52347bdSJani Nikula 1412e52347bdSJani Nikula hcl= [IA-64] SGI's Hardware Graph compatibility layer 1413e52347bdSJani Nikula 1414e52347bdSJani Nikula hd= [EIDE] (E)IDE hard drive subsystem geometry 1415e52347bdSJani Nikula Format: <cyl>,<head>,<sect> 1416e52347bdSJani Nikula 1417e52347bdSJani Nikula hest_disable [ACPI] 1418e52347bdSJani Nikula Disable Hardware Error Source Table (HEST) support; 1419e52347bdSJani Nikula corresponding firmware-first mode error processing 1420e52347bdSJani Nikula logic will be disabled. 1421e52347bdSJani Nikula 1422e52347bdSJani Nikula highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 1423e52347bdSJani Nikula size of <nn>. This works even on boxes that have no 1424e52347bdSJani Nikula highmem otherwise. This also works to reduce highmem 1425e52347bdSJani Nikula size on bigger boxes. 1426e52347bdSJani Nikula 1427e52347bdSJani Nikula highres= [KNL] Enable/disable high resolution timer mode. 1428e52347bdSJani Nikula Valid parameters: "on", "off" 1429e52347bdSJani Nikula Default: "on" 1430e52347bdSJani Nikula 1431e52347bdSJani Nikula hlt [BUGS=ARM,SH] 1432e52347bdSJani Nikula 1433e52347bdSJani Nikula hpet= [X86-32,HPET] option to control HPET usage 1434e52347bdSJani Nikula Format: { enable (default) | disable | force | 1435e52347bdSJani Nikula verbose } 1436e52347bdSJani Nikula disable: disable HPET and use PIT instead 1437e52347bdSJani Nikula force: allow force enabled of undocumented chips (ICH4, 1438e52347bdSJani Nikula VIA, nVidia) 1439e52347bdSJani Nikula verbose: show contents of HPET registers during setup 1440e52347bdSJani Nikula 1441e52347bdSJani Nikula hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET 1442e52347bdSJani Nikula registers. Default set by CONFIG_HPET_MMAP_DEFAULT. 1443e52347bdSJani Nikula 1444e52347bdSJani Nikula hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. 1445e52347bdSJani Nikula hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. 1446e52347bdSJani Nikula On x86-64 and powerpc, this option can be specified 1447e52347bdSJani Nikula multiple times interleaved with hugepages= to reserve 1448e52347bdSJani Nikula huge pages of different sizes. Valid pages sizes on 1449e52347bdSJani Nikula x86-64 are 2M (when the CPU supports "pse") and 1G 1450e52347bdSJani Nikula (when the CPU supports the "pdpe1gb" cpuinfo flag). 1451e52347bdSJani Nikula 1452a49d9c0aSOmar Sandoval hung_task_panic= 1453a49d9c0aSOmar Sandoval [KNL] Should the hung task detector generate panics. 1454a49d9c0aSOmar Sandoval Format: <integer> 1455a49d9c0aSOmar Sandoval 1456a49d9c0aSOmar Sandoval A nonzero value instructs the kernel to panic when a 1457a49d9c0aSOmar Sandoval hung task is detected. The default value is controlled 1458a49d9c0aSOmar Sandoval by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time 1459a49d9c0aSOmar Sandoval option. The value selected by this boot parameter can 1460a49d9c0aSOmar Sandoval be changed later by the kernel.hung_task_panic sysctl. 1461a49d9c0aSOmar Sandoval 1462e52347bdSJani Nikula hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) 1463e52347bdSJani Nikula terminal devices. Valid values: 0..8 1464e52347bdSJani Nikula hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. 1465e52347bdSJani Nikula If specified, z/VM IUCV HVC accepts connections 1466e52347bdSJani Nikula from listed z/VM user IDs only. 14673a025de6SYi Sun 14683a025de6SYi Sun hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations 14693a025de6SYi Sun which allow the hypervisor to 'idle' the 14703a025de6SYi Sun guest on lock contention. 14713a025de6SYi Sun 1472e52347bdSJani Nikula keep_bootcon [KNL] 1473e52347bdSJani Nikula Do not unregister boot console at start. This is only 1474e52347bdSJani Nikula useful for debugging when something happens in the window 1475e52347bdSJani Nikula between unregistering the boot console and initializing 1476e52347bdSJani Nikula the real console. 1477e52347bdSJani Nikula 1478e52347bdSJani Nikula i2c_bus= [HW] Override the default board specific I2C bus speed 1479e52347bdSJani Nikula or register an additional I2C bus that is not 1480e52347bdSJani Nikula registered from board initialization code. 1481e52347bdSJani Nikula Format: 1482e52347bdSJani Nikula <bus_id>,<clkrate> 1483e52347bdSJani Nikula 1484e52347bdSJani Nikula i8042.debug [HW] Toggle i8042 debug mode 1485e52347bdSJani Nikula i8042.unmask_kbd_data 1486e52347bdSJani Nikula [HW] Enable printing of interrupt data from the KBD port 1487e52347bdSJani Nikula (disabled by default, and as a pre-condition 1488e52347bdSJani Nikula requires that i8042.debug=1 be enabled) 1489e52347bdSJani Nikula i8042.direct [HW] Put keyboard port into non-translated mode 1490e52347bdSJani Nikula i8042.dumbkbd [HW] Pretend that controller can only read data from 1491e52347bdSJani Nikula keyboard and cannot control its state 1492e52347bdSJani Nikula (Don't attempt to blink the leds) 1493e52347bdSJani Nikula i8042.noaux [HW] Don't check for auxiliary (== mouse) port 1494e52347bdSJani Nikula i8042.nokbd [HW] Don't check/create keyboard port 1495e52347bdSJani Nikula i8042.noloop [HW] Disable the AUX Loopback command while probing 1496e52347bdSJani Nikula for the AUX port 1497e52347bdSJani Nikula i8042.nomux [HW] Don't check presence of an active multiplexing 1498e52347bdSJani Nikula controller 1499e52347bdSJani Nikula i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 1500e52347bdSJani Nikula controllers 1501e52347bdSJani Nikula i8042.notimeout [HW] Ignore timeout condition signalled by controller 1502e52347bdSJani Nikula i8042.reset [HW] Reset the controller during init, cleanup and 1503e52347bdSJani Nikula suspend-to-ram transitions, only during s2r 1504e52347bdSJani Nikula transitions, or never reset 1505e52347bdSJani Nikula Format: { 1 | Y | y | 0 | N | n } 1506e52347bdSJani Nikula 1, Y, y: always reset controller 1507e52347bdSJani Nikula 0, N, n: don't ever reset controller 1508e52347bdSJani Nikula Default: only on s2r transitions on x86; most other 1509e52347bdSJani Nikula architectures force reset to be always executed 1510e52347bdSJani Nikula i8042.unlock [HW] Unlock (ignore) the keylock 1511e52347bdSJani Nikula i8042.kbdreset [HW] Reset device connected to KBD port 1512e52347bdSJani Nikula 1513e52347bdSJani Nikula i810= [HW,DRM] 1514e52347bdSJani Nikula 1515e52347bdSJani Nikula i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 1516e52347bdSJani Nikula indicates that the driver is running on unsupported 1517e52347bdSJani Nikula hardware. 1518e52347bdSJani Nikula i8k.force [HW] Activate i8k driver even if SMM BIOS signature 1519e52347bdSJani Nikula does not match list of supported models. 1520e52347bdSJani Nikula i8k.power_status 1521e52347bdSJani Nikula [HW] Report power status in /proc/i8k 1522e52347bdSJani Nikula (disabled by default) 1523e52347bdSJani Nikula i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 1524e52347bdSJani Nikula capability is set. 1525e52347bdSJani Nikula 1526e52347bdSJani Nikula i915.invert_brightness= 1527e52347bdSJani Nikula [DRM] Invert the sense of the variable that is used to 1528e52347bdSJani Nikula set the brightness of the panel backlight. Normally a 1529e52347bdSJani Nikula brightness value of 0 indicates backlight switched off, 1530e52347bdSJani Nikula and the maximum of the brightness value sets the backlight 1531e52347bdSJani Nikula to maximum brightness. If this parameter is set to 0 1532e52347bdSJani Nikula (default) and the machine requires it, or this parameter 1533e52347bdSJani Nikula is set to 1, a brightness value of 0 sets the backlight 1534e52347bdSJani Nikula to maximum brightness, and the maximum of the brightness 1535e52347bdSJani Nikula value switches the backlight off. 1536e52347bdSJani Nikula -1 -- never invert brightness 1537e52347bdSJani Nikula 0 -- machine default 1538e52347bdSJani Nikula 1 -- force brightness inversion 1539e52347bdSJani Nikula 1540e52347bdSJani Nikula icn= [HW,ISDN] 1541e52347bdSJani Nikula Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 1542e52347bdSJani Nikula 1543e52347bdSJani Nikula ide-core.nodma= [HW] (E)IDE subsystem 1544e52347bdSJani Nikula Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc 1545e52347bdSJani Nikula .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr 1546e52347bdSJani Nikula .cdrom .chs .ignore_cable are additional options 1547d7b461c5SMauro Carvalho Chehab See Documentation/ide/ide.rst. 1548e52347bdSJani Nikula 1549e52347bdSJani Nikula ide-generic.probe-mask= [HW] (E)IDE subsystem 1550e52347bdSJani Nikula Format: <int> 1551e52347bdSJani Nikula Probe mask for legacy ISA IDE ports. Depending on 1552e52347bdSJani Nikula platform up to 6 ports are supported, enabled by 1553e52347bdSJani Nikula setting corresponding bits in the mask to 1. The 1554e52347bdSJani Nikula default value is 0x0, which has a special meaning. 1555e52347bdSJani Nikula On systems that have PCI, it triggers scanning the 1556e52347bdSJani Nikula PCI bus for the first and the second port, which 1557e52347bdSJani Nikula are then probed. On systems without PCI the value 1558e52347bdSJani Nikula of 0x0 enables probing the two first ports as if it 1559e52347bdSJani Nikula was 0x3. 1560e52347bdSJani Nikula 1561e52347bdSJani Nikula ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 1562e52347bdSJani Nikula Claim all unknown PCI IDE storage controllers. 1563e52347bdSJani Nikula 1564e52347bdSJani Nikula idle= [X86] 1565e52347bdSJani Nikula Format: idle=poll, idle=halt, idle=nomwait 1566e52347bdSJani Nikula Poll forces a polling idle loop that can slightly 1567e52347bdSJani Nikula improve the performance of waking up a idle CPU, but 1568e52347bdSJani Nikula will use a lot of power and make the system run hot. 1569e52347bdSJani Nikula Not recommended. 1570e52347bdSJani Nikula idle=halt: Halt is forced to be used for CPU idle. 1571e52347bdSJani Nikula In such case C2/C3 won't be used again. 1572e52347bdSJani Nikula idle=nomwait: Disable mwait for CPU C-states 1573e52347bdSJani Nikula 1574e52347bdSJani Nikula ieee754= [MIPS] Select IEEE Std 754 conformance mode 1575e52347bdSJani Nikula Format: { strict | legacy | 2008 | relaxed } 1576e52347bdSJani Nikula Default: strict 1577e52347bdSJani Nikula 1578e52347bdSJani Nikula Choose which programs will be accepted for execution 1579e52347bdSJani Nikula based on the IEEE 754 NaN encoding(s) supported by 1580e52347bdSJani Nikula the FPU and the NaN encoding requested with the value 1581e52347bdSJani Nikula of an ELF file header flag individually set by each 1582e52347bdSJani Nikula binary. Hardware implementations are permitted to 1583e52347bdSJani Nikula support either or both of the legacy and the 2008 NaN 1584e52347bdSJani Nikula encoding mode. 1585e52347bdSJani Nikula 1586e52347bdSJani Nikula Available settings are as follows: 1587e52347bdSJani Nikula strict accept binaries that request a NaN encoding 1588e52347bdSJani Nikula supported by the FPU 1589e52347bdSJani Nikula legacy only accept legacy-NaN binaries, if supported 1590e52347bdSJani Nikula by the FPU 1591e52347bdSJani Nikula 2008 only accept 2008-NaN binaries, if supported 1592e52347bdSJani Nikula by the FPU 1593e52347bdSJani Nikula relaxed accept any binaries regardless of whether 1594e52347bdSJani Nikula supported by the FPU 1595e52347bdSJani Nikula 1596e52347bdSJani Nikula The FPU emulator is always able to support both NaN 1597e52347bdSJani Nikula encodings, so if no FPU hardware is present or it has 1598e52347bdSJani Nikula been disabled with 'nofpu', then the settings of 1599e52347bdSJani Nikula 'legacy' and '2008' strap the emulator accordingly, 1600e52347bdSJani Nikula 'relaxed' straps the emulator for both legacy-NaN and 1601e52347bdSJani Nikula 2008-NaN, whereas 'strict' enables legacy-NaN only on 1602e52347bdSJani Nikula legacy processors and both NaN encodings on MIPS32 or 1603e52347bdSJani Nikula MIPS64 CPUs. 1604e52347bdSJani Nikula 1605e52347bdSJani Nikula The setting for ABS.fmt/NEG.fmt instruction execution 1606e52347bdSJani Nikula mode generally follows that for the NaN encoding, 1607e52347bdSJani Nikula except where unsupported by hardware. 1608e52347bdSJani Nikula 1609e52347bdSJani Nikula ignore_loglevel [KNL] 1610e52347bdSJani Nikula Ignore loglevel setting - this will print /all/ 1611e52347bdSJani Nikula kernel messages to the console. Useful for debugging. 1612e52347bdSJani Nikula We also add it as printk module parameter, so users 1613e52347bdSJani Nikula could change it dynamically, usually by 1614e52347bdSJani Nikula /sys/module/printk/parameters/ignore_loglevel. 1615e52347bdSJani Nikula 1616e52347bdSJani Nikula ignore_rlimit_data 1617e52347bdSJani Nikula Ignore RLIMIT_DATA setting for data mappings, 1618e52347bdSJani Nikula print warning at first misuse. Can be changed via 1619e52347bdSJani Nikula /sys/module/kernel/parameters/ignore_rlimit_data. 1620e52347bdSJani Nikula 1621e52347bdSJani Nikula ihash_entries= [KNL] 1622e52347bdSJani Nikula Set number of hash buckets for inode cache. 1623e52347bdSJani Nikula 1624e52347bdSJani Nikula ima_appraise= [IMA] appraise integrity measurements 1625e52347bdSJani Nikula Format: { "off" | "enforce" | "fix" | "log" } 1626e52347bdSJani Nikula default: "enforce" 1627e52347bdSJani Nikula 162841475a3eSPetr Vorel ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead. 1629e52347bdSJani Nikula The builtin appraise policy appraises all files 1630e52347bdSJani Nikula owned by uid=0. 1631e52347bdSJani Nikula 1632d68a6fe9SMimi Zohar ima_canonical_fmt [IMA] 1633d68a6fe9SMimi Zohar Use the canonical format for the binary runtime 1634d68a6fe9SMimi Zohar measurements, instead of host native format. 1635d68a6fe9SMimi Zohar 1636e52347bdSJani Nikula ima_hash= [IMA] 1637e52347bdSJani Nikula Format: { md5 | sha1 | rmd160 | sha256 | sha384 1638e52347bdSJani Nikula | sha512 | ... } 1639e52347bdSJani Nikula default: "sha1" 1640e52347bdSJani Nikula 1641e52347bdSJani Nikula The list of supported hash algorithms is defined 1642e52347bdSJani Nikula in crypto/hash_info.h. 1643e52347bdSJani Nikula 1644e52347bdSJani Nikula ima_policy= [IMA] 164533ce9549SMimi Zohar The builtin policies to load during IMA setup. 16469e67028eSMimi Zohar Format: "tcb | appraise_tcb | secure_boot | 16479e67028eSMimi Zohar fail_securely" 164833ce9549SMimi Zohar 164933ce9549SMimi Zohar The "tcb" policy measures all programs exec'd, files 165033ce9549SMimi Zohar mmap'd for exec, and all files opened with the read 165133ce9549SMimi Zohar mode bit set by either the effective uid (euid=0) or 165233ce9549SMimi Zohar uid=0. 165333ce9549SMimi Zohar 165433ce9549SMimi Zohar The "appraise_tcb" policy appraises the integrity of 165541475a3eSPetr Vorel all files owned by root. 1656e52347bdSJani Nikula 1657503ceaefSMimi Zohar The "secure_boot" policy appraises the integrity 1658503ceaefSMimi Zohar of files (eg. kexec kernel image, kernel modules, 1659503ceaefSMimi Zohar firmware, policy, etc) based on file signatures. 1660e52347bdSJani Nikula 16619e67028eSMimi Zohar The "fail_securely" policy forces file signature 16629e67028eSMimi Zohar verification failure also on privileged mounted 16639e67028eSMimi Zohar filesystems with the SB_I_UNVERIFIABLE_SIGNATURE 16649e67028eSMimi Zohar flag. 16659e67028eSMimi Zohar 1666e52347bdSJani Nikula ima_tcb [IMA] Deprecated. Use ima_policy= instead. 1667e52347bdSJani Nikula Load a policy which meets the needs of the Trusted 1668e52347bdSJani Nikula Computing Base. This means IMA will measure all 1669e52347bdSJani Nikula programs exec'd, files mmap'd for exec, and all files 1670e52347bdSJani Nikula opened for read by uid=0. 1671e52347bdSJani Nikula 1672e52347bdSJani Nikula ima_template= [IMA] 1673e52347bdSJani Nikula Select one of defined IMA measurements template formats. 1674e52347bdSJani Nikula Formats: { "ima" | "ima-ng" | "ima-sig" } 1675e52347bdSJani Nikula Default: "ima-ng" 1676e52347bdSJani Nikula 1677e52347bdSJani Nikula ima_template_fmt= 1678e52347bdSJani Nikula [IMA] Define a custom template format. 1679e52347bdSJani Nikula Format: { "field1|...|fieldN" } 1680e52347bdSJani Nikula 1681e52347bdSJani Nikula ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage 1682e52347bdSJani Nikula Format: <min_file_size> 1683e52347bdSJani Nikula Set the minimal file size for using asynchronous hash. 1684e52347bdSJani Nikula If left unspecified, ahash usage is disabled. 1685e52347bdSJani Nikula 1686e52347bdSJani Nikula ahash performance varies for different data sizes on 1687e52347bdSJani Nikula different crypto accelerators. This option can be used 1688e52347bdSJani Nikula to achieve the best performance for a particular HW. 1689e52347bdSJani Nikula 1690e52347bdSJani Nikula ima.ahash_bufsize= [IMA] Asynchronous hash buffer size 1691e52347bdSJani Nikula Format: <bufsize> 1692e52347bdSJani Nikula Set hashing buffer size. Default: 4k. 1693e52347bdSJani Nikula 1694e52347bdSJani Nikula ahash performance varies for different chunk sizes on 1695e52347bdSJani Nikula different crypto accelerators. This option can be used 1696e52347bdSJani Nikula to achieve best performance for particular HW. 1697e52347bdSJani Nikula 1698e52347bdSJani Nikula init= [KNL] 1699e52347bdSJani Nikula Format: <full_path> 1700e52347bdSJani Nikula Run specified binary instead of /sbin/init as init 1701e52347bdSJani Nikula process. 1702e52347bdSJani Nikula 1703e52347bdSJani Nikula initcall_debug [KNL] Trace initcalls as they are executed. Useful 1704e52347bdSJani Nikula for working out where the kernel is dying during 1705e52347bdSJani Nikula startup. 1706e52347bdSJani Nikula 1707e52347bdSJani Nikula initcall_blacklist= [KNL] Do not execute a comma-separated list of 1708e52347bdSJani Nikula initcall functions. Useful for debugging built-in 1709e52347bdSJani Nikula modules and initcalls. 1710e52347bdSJani Nikula 1711e52347bdSJani Nikula initrd= [BOOT] Specify the location of the initial ramdisk 1712e52347bdSJani Nikula 17136471384aSAlexander Potapenko init_on_alloc= [MM] Fill newly allocated pages and heap objects with 17146471384aSAlexander Potapenko zeroes. 17156471384aSAlexander Potapenko Format: 0 | 1 17166471384aSAlexander Potapenko Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON. 17176471384aSAlexander Potapenko 17186471384aSAlexander Potapenko init_on_free= [MM] Fill freed pages and heap objects with zeroes. 17196471384aSAlexander Potapenko Format: 0 | 1 17206471384aSAlexander Potapenko Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON. 17216471384aSAlexander Potapenko 1722e52347bdSJani Nikula init_pkru= [x86] Specify the default memory protection keys rights 1723e52347bdSJani Nikula register contents for all processes. 0x55555554 by 1724e52347bdSJani Nikula default (disallow access to all but pkey 0). Can 1725e52347bdSJani Nikula override in debugfs after boot. 1726e52347bdSJani Nikula 1727e52347bdSJani Nikula inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 1728e52347bdSJani Nikula Format: <irq> 1729e52347bdSJani Nikula 1730e52347bdSJani Nikula int_pln_enable [x86] Enable power limit notification interrupt 1731e52347bdSJani Nikula 1732e52347bdSJani Nikula integrity_audit=[IMA] 1733e52347bdSJani Nikula Format: { "0" | "1" } 1734e52347bdSJani Nikula 0 -- basic integrity auditing messages. (Default) 1735e52347bdSJani Nikula 1 -- additional integrity auditing messages. 1736e52347bdSJani Nikula 1737e52347bdSJani Nikula intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 1738e52347bdSJani Nikula on 1739e52347bdSJani Nikula Enable intel iommu driver. 1740e52347bdSJani Nikula off 1741e52347bdSJani Nikula Disable intel iommu driver. 1742e52347bdSJani Nikula igfx_off [Default Off] 1743e52347bdSJani Nikula By default, gfx is mapped as normal device. If a gfx 1744e52347bdSJani Nikula device has a dedicated DMAR unit, the DMAR unit is 1745e52347bdSJani Nikula bypassed by not enabling DMAR with this option. In 1746e52347bdSJani Nikula this case, gfx device will use physical address for 1747e52347bdSJani Nikula DMA. 1748e52347bdSJani Nikula forcedac [x86_64] 1749e52347bdSJani Nikula With this option iommu will not optimize to look 1750e52347bdSJani Nikula for io virtual address below 32-bit forcing dual 1751e52347bdSJani Nikula address cycle on pci bus for cards supporting greater 1752e52347bdSJani Nikula than 32-bit addressing. The default is to look 1753e52347bdSJani Nikula for translation below 32-bit and if not available 1754e52347bdSJani Nikula then look in the higher range. 1755e52347bdSJani Nikula strict [Default Off] 1756e52347bdSJani Nikula With this option on every unmap_single operation will 1757e52347bdSJani Nikula result in a hardware IOTLB flush operation as opposed 1758e52347bdSJani Nikula to batching them for performance. 1759e52347bdSJani Nikula sp_off [Default Off] 1760e52347bdSJani Nikula By default, super page will be supported if Intel IOMMU 1761e52347bdSJani Nikula has the capability. With this option, super page will 1762e52347bdSJani Nikula not be supported. 17638950dcd8SLu Baolu sm_on [Default Off] 17648950dcd8SLu Baolu By default, scalable mode will be disabled even if the 1765765b6a98SLu Baolu hardware advertises that it has support for the scalable 1766765b6a98SLu Baolu mode translation. With this option set, scalable mode 17678950dcd8SLu Baolu will be used on hardware which claims to support it. 1768bfd20f1cSShaohua Li tboot_noforce [Default Off] 1769bfd20f1cSShaohua Li Do not force the Intel IOMMU enabled under tboot. 1770bfd20f1cSShaohua Li By default, tboot will force Intel IOMMU on, which 1771bfd20f1cSShaohua Li could harm performance of some high-throughput 1772bfd20f1cSShaohua Li devices like 40GBit network cards, even if identity 1773bfd20f1cSShaohua Li mapping is enabled. 1774bfd20f1cSShaohua Li Note that using this option lowers the security 1775bfd20f1cSShaohua Li provided by tboot because it makes the system 1776bfd20f1cSShaohua Li vulnerable to DMA attacks. 1777e5e04d05SLu Baolu nobounce [Default off] 1778e5e04d05SLu Baolu Disable bounce buffer for unstrusted devices such as 1779e5e04d05SLu Baolu the Thunderbolt devices. This will treat the untrusted 1780e5e04d05SLu Baolu devices as the trusted ones, hence might expose security 1781e5e04d05SLu Baolu risks of DMA attacks. 1782e52347bdSJani Nikula 1783e52347bdSJani Nikula intel_idle.max_cstate= [KNL,HW,ACPI,X86] 1784e52347bdSJani Nikula 0 disables intel_idle and fall back on acpi_idle. 1785e52347bdSJani Nikula 1 to 9 specify maximum depth of C-state. 1786e52347bdSJani Nikula 1787e52347bdSJani Nikula intel_pstate= [X86] 1788e52347bdSJani Nikula disable 1789e52347bdSJani Nikula Do not enable intel_pstate as the default 1790e52347bdSJani Nikula scaling driver for the supported processors 17917b9dc3f7SLinus Torvalds passive 17927b9dc3f7SLinus Torvalds Use intel_pstate as a scaling driver, but configure it 17937b9dc3f7SLinus Torvalds to work with generic cpufreq governors (instead of 17947b9dc3f7SLinus Torvalds enabling its internal governor). This mode cannot be 17957b9dc3f7SLinus Torvalds used along with the hardware-managed P-states (HWP) 17967b9dc3f7SLinus Torvalds feature. 1797e52347bdSJani Nikula force 1798e52347bdSJani Nikula Enable intel_pstate on systems that prohibit it by default 1799e52347bdSJani Nikula in favor of acpi-cpufreq. Forcing the intel_pstate driver 1800e52347bdSJani Nikula instead of acpi-cpufreq may disable platform features, such 1801e52347bdSJani Nikula as thermal controls and power capping, that rely on ACPI 1802e52347bdSJani Nikula P-States information being indicated to OSPM and therefore 1803e52347bdSJani Nikula should be used with caution. This option does not work with 1804e52347bdSJani Nikula processors that aren't supported by the intel_pstate driver 1805e52347bdSJani Nikula or on platforms that use pcc-cpufreq instead of acpi-cpufreq. 1806e52347bdSJani Nikula no_hwp 1807e52347bdSJani Nikula Do not enable hardware P state control (HWP) 1808e52347bdSJani Nikula if available. 1809e52347bdSJani Nikula hwp_only 1810e52347bdSJani Nikula Only load intel_pstate on systems which support 1811e52347bdSJani Nikula hardware P state control (HWP) if available. 1812e52347bdSJani Nikula support_acpi_ppc 1813e52347bdSJani Nikula Enforce ACPI _PPC performance limits. If the Fixed ACPI 1814e52347bdSJani Nikula Description Table, specifies preferred power management 1815e52347bdSJani Nikula profile as "Enterprise Server" or "Performance Server", 1816e52347bdSJani Nikula then this feature is turned on by default. 18177b9dc3f7SLinus Torvalds per_cpu_perf_limits 18187b9dc3f7SLinus Torvalds Allow per-logical-CPU P-State performance control limits using 18197b9dc3f7SLinus Torvalds cpufreq sysfs interface 1820e52347bdSJani Nikula 1821e52347bdSJani Nikula intremap= [X86-64, Intel-IOMMU] 1822e52347bdSJani Nikula on enable Interrupt Remapping (default) 1823e52347bdSJani Nikula off disable Interrupt Remapping 1824e52347bdSJani Nikula nosid disable Source ID checking 1825e52347bdSJani Nikula no_x2apic_optout 1826e52347bdSJani Nikula BIOS x2APIC opt-out request will be ignored 1827e52347bdSJani Nikula nopost disable Interrupt Posting 1828e52347bdSJani Nikula 1829e52347bdSJani Nikula iomem= Disable strict checking of access to MMIO memory 1830e52347bdSJani Nikula strict regions from userspace. 1831e52347bdSJani Nikula relaxed 1832e52347bdSJani Nikula 1833e52347bdSJani Nikula iommu= [x86] 1834e52347bdSJani Nikula off 1835e52347bdSJani Nikula force 1836e52347bdSJani Nikula noforce 1837e52347bdSJani Nikula biomerge 1838e52347bdSJani Nikula panic 1839e52347bdSJani Nikula nopanic 1840e52347bdSJani Nikula merge 1841e52347bdSJani Nikula nomerge 1842e52347bdSJani Nikula soft 184358d11317SOlof Johansson pt [x86] 184458d11317SOlof Johansson nopt [x86] 1845e52347bdSJani Nikula nobypass [PPC/POWERNV] 1846e52347bdSJani Nikula Disable IOMMU bypass, using IOMMU for PCI devices. 1847e52347bdSJani Nikula 184868a6efe8SZhen Lei iommu.strict= [ARM64] Configure TLB invalidation behaviour 184968a6efe8SZhen Lei Format: { "0" | "1" } 185068a6efe8SZhen Lei 0 - Lazy mode. 185168a6efe8SZhen Lei Request that DMA unmap operations use deferred 185268a6efe8SZhen Lei invalidation of hardware TLBs, for increased 185368a6efe8SZhen Lei throughput at the cost of reduced device isolation. 185468a6efe8SZhen Lei Will fall back to strict mode if not supported by 185568a6efe8SZhen Lei the relevant IOMMU driver. 185668a6efe8SZhen Lei 1 - Strict mode (default). 185768a6efe8SZhen Lei DMA unmap operations invalidate IOMMU hardware TLBs 185868a6efe8SZhen Lei synchronously. 185968a6efe8SZhen Lei 1860fccb4e3bSWill Deacon iommu.passthrough= 1861c8fb436bSJoerg Roedel [ARM64, X86] Configure DMA to bypass the IOMMU by default. 1862fccb4e3bSWill Deacon Format: { "0" | "1" } 1863fccb4e3bSWill Deacon 0 - Use IOMMU translation for DMA. 1864fccb4e3bSWill Deacon 1 - Bypass the IOMMU for DMA. 18659d723b4cSRobin Murphy unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. 1866e52347bdSJani Nikula 1867e52347bdSJani Nikula io7= [HW] IO7 for Marvel based alpha systems 1868e52347bdSJani Nikula See comment before marvel_specify_io7 in 1869e52347bdSJani Nikula arch/alpha/kernel/core_marvel.c. 1870e52347bdSJani Nikula 1871e52347bdSJani Nikula io_delay= [X86] I/O delay method 1872e52347bdSJani Nikula 0x80 1873e52347bdSJani Nikula Standard port 0x80 based delay 1874e52347bdSJani Nikula 0xed 1875e52347bdSJani Nikula Alternate port 0xed based delay (needed on some systems) 1876e52347bdSJani Nikula udelay 1877e52347bdSJani Nikula Simple two microseconds delay 1878e52347bdSJani Nikula none 1879e52347bdSJani Nikula No delay 1880e52347bdSJani Nikula 1881e52347bdSJani Nikula ip= [IP_PNP] 1882e52347bdSJani Nikula See Documentation/filesystems/nfs/nfsroot.txt. 1883e52347bdSJani Nikula 18845ac893b8SWaiman Long ipcmni_extend [KNL] Extend the maximum number of unique System V 18855ac893b8SWaiman Long IPC identifiers from 32,768 to 16,777,216. 18865ac893b8SWaiman Long 1887e52347bdSJani Nikula irqaffinity= [SMP] Set the default irq affinity mask 1888e52347bdSJani Nikula The argument is a cpu list, as described above. 1889e52347bdSJani Nikula 18900962289bSMarc Zyngier irqchip.gicv2_force_probe= 18910962289bSMarc Zyngier [ARM, ARM64] 18920962289bSMarc Zyngier Format: <bool> 18930962289bSMarc Zyngier Force the kernel to look for the second 4kB page 18940962289bSMarc Zyngier of a GICv2 controller even if the memory range 18950962289bSMarc Zyngier exposed by the device tree is too small. 18960962289bSMarc Zyngier 1897f736d65dSMarc Zyngier irqchip.gicv3_nolpi= 1898f736d65dSMarc Zyngier [ARM, ARM64] 1899f736d65dSMarc Zyngier Force the kernel to ignore the availability of 1900f736d65dSMarc Zyngier LPIs (and by consequence ITSs). Intended for system 1901f736d65dSMarc Zyngier that use the kernel as a bootloader, and thus want 1902f736d65dSMarc Zyngier to let secondary kernels in charge of setting up 1903f736d65dSMarc Zyngier LPIs. 1904f736d65dSMarc Zyngier 1905bc3c03ccSJulien Thierry irqchip.gicv3_pseudo_nmi= [ARM64] 1906bc3c03ccSJulien Thierry Enables support for pseudo-NMIs in the kernel. This 1907bc3c03ccSJulien Thierry requires the kernel to be built with 1908bc3c03ccSJulien Thierry CONFIG_ARM64_PSEUDO_NMI. 1909bc3c03ccSJulien Thierry 1910e52347bdSJani Nikula irqfixup [HW] 1911e52347bdSJani Nikula When an interrupt is not handled search all handlers 1912e52347bdSJani Nikula for it. Intended to get systems with badly broken 1913e52347bdSJani Nikula firmware running. 1914e52347bdSJani Nikula 1915e52347bdSJani Nikula irqpoll [HW] 1916e52347bdSJani Nikula When an interrupt is not handled search all handlers 1917e52347bdSJani Nikula for it. Also check all handlers each timer 1918e52347bdSJani Nikula interrupt. Intended to get systems with badly broken 1919e52347bdSJani Nikula firmware running. 1920e52347bdSJani Nikula 1921e52347bdSJani Nikula isapnp= [ISAPNP] 1922e52347bdSJani Nikula Format: <RDP>,<reset>,<pci_scan>,<verbosity> 1923e52347bdSJani Nikula 1924d94d1053SFrederic Weisbecker isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance. 1925b0d40d2bSFrederic Weisbecker [Deprecated - use cpusets instead] 1926b0d40d2bSFrederic Weisbecker Format: [flag-list,]<cpu-list> 1927e52347bdSJani Nikula 1928b0d40d2bSFrederic Weisbecker Specify one or more CPUs to isolate from disturbances 1929b0d40d2bSFrederic Weisbecker specified in the flag list (default: domain): 1930b0d40d2bSFrederic Weisbecker 1931b0d40d2bSFrederic Weisbecker nohz 1932b0d40d2bSFrederic Weisbecker Disable the tick when a single task runs. 1933083c6eeaSFrederic Weisbecker 1934083c6eeaSFrederic Weisbecker A residual 1Hz tick is offloaded to workqueues, which you 1935083c6eeaSFrederic Weisbecker need to affine to housekeeping through the global 1936083c6eeaSFrederic Weisbecker workqueue's affinity configured via the 1937083c6eeaSFrederic Weisbecker /sys/devices/virtual/workqueue/cpumask sysfs file, or 1938083c6eeaSFrederic Weisbecker by using the 'domain' flag described below. 1939083c6eeaSFrederic Weisbecker 1940083c6eeaSFrederic Weisbecker NOTE: by default the global workqueue runs on all CPUs, 1941083c6eeaSFrederic Weisbecker so to protect individual CPUs the 'cpumask' file has to 1942083c6eeaSFrederic Weisbecker be configured manually after bootup. 1943083c6eeaSFrederic Weisbecker 1944b0d40d2bSFrederic Weisbecker domain 1945b0d40d2bSFrederic Weisbecker Isolate from the general SMP balancing and scheduling 1946b0d40d2bSFrederic Weisbecker algorithms. Note that performing domain isolation this way 1947b0d40d2bSFrederic Weisbecker is irreversible: it's not possible to bring back a CPU to 1948b0d40d2bSFrederic Weisbecker the domains once isolated through isolcpus. It's strongly 1949b0d40d2bSFrederic Weisbecker advised to use cpusets instead to disable scheduler load 1950b0d40d2bSFrederic Weisbecker balancing through the "cpuset.sched_load_balance" file. 1951b0d40d2bSFrederic Weisbecker It offers a much more flexible interface where CPUs can 1952b0d40d2bSFrederic Weisbecker move in and out of an isolated set anytime. 1953b0d40d2bSFrederic Weisbecker 1954b0d40d2bSFrederic Weisbecker You can move a process onto or off an "isolated" CPU via 1955b0d40d2bSFrederic Weisbecker the CPU affinity syscalls or cpuset. 1956e52347bdSJani Nikula <cpu number> begins at 0 and the maximum value is 1957e52347bdSJani Nikula "number of CPUs in system - 1". 1958e52347bdSJani Nikula 195911ea68f5SMing Lei managed_irq 196011ea68f5SMing Lei 196111ea68f5SMing Lei Isolate from being targeted by managed interrupts 196211ea68f5SMing Lei which have an interrupt mask containing isolated 196311ea68f5SMing Lei CPUs. The affinity of managed interrupts is 196411ea68f5SMing Lei handled by the kernel and cannot be changed via 196511ea68f5SMing Lei the /proc/irq/* interfaces. 196611ea68f5SMing Lei 196711ea68f5SMing Lei This isolation is best effort and only effective 196811ea68f5SMing Lei if the automatically assigned interrupt mask of a 196911ea68f5SMing Lei device queue contains isolated and housekeeping 197011ea68f5SMing Lei CPUs. If housekeeping CPUs are online then such 197111ea68f5SMing Lei interrupts are directed to the housekeeping CPU 197211ea68f5SMing Lei so that IO submitted on the housekeeping CPU 197311ea68f5SMing Lei cannot disturb the isolated CPU. 197411ea68f5SMing Lei 197511ea68f5SMing Lei If a queue's affinity mask contains only isolated 197611ea68f5SMing Lei CPUs then this parameter has no effect on the 197711ea68f5SMing Lei interrupt routing decision, though interrupts are 197811ea68f5SMing Lei only delivered when tasks running on those 197911ea68f5SMing Lei isolated CPUs submit IO. IO submitted on 198011ea68f5SMing Lei housekeeping CPUs has no influence on those 198111ea68f5SMing Lei queues. 198211ea68f5SMing Lei 1983b0d40d2bSFrederic Weisbecker The format of <cpu-list> is described above. 1984b0d40d2bSFrederic Weisbecker 1985e52347bdSJani Nikula iucv= [HW,NET] 1986e52347bdSJani Nikula 1987e52347bdSJani Nikula ivrs_ioapic [HW,X86_64] 1988e52347bdSJani Nikula Provide an override to the IOAPIC-ID<->DEVICE-ID 1989e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 1990e52347bdSJani Nikula example, to map IOAPIC-ID decimal 10 to 1991e52347bdSJani Nikula PCI device 00:14.0 write the parameter as: 1992e52347bdSJani Nikula ivrs_ioapic[10]=00:14.0 1993e52347bdSJani Nikula 1994e52347bdSJani Nikula ivrs_hpet [HW,X86_64] 1995e52347bdSJani Nikula Provide an override to the HPET-ID<->DEVICE-ID 1996e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 1997e52347bdSJani Nikula example, to map HPET-ID decimal 0 to 1998e52347bdSJani Nikula PCI device 00:14.0 write the parameter as: 1999e52347bdSJani Nikula ivrs_hpet[0]=00:14.0 2000e52347bdSJani Nikula 2001e52347bdSJani Nikula ivrs_acpihid [HW,X86_64] 2002e52347bdSJani Nikula Provide an override to the ACPI-HID:UID<->DEVICE-ID 2003e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 2004e52347bdSJani Nikula example, to map UART-HID:UID AMD0020:0 to 2005e52347bdSJani Nikula PCI device 00:14.5 write the parameter as: 2006e52347bdSJani Nikula ivrs_acpihid[00:14.5]=AMD0020:0 2007e52347bdSJani Nikula 2008e52347bdSJani Nikula js= [HW,JOY] Analog joystick 20091752118dSTom Saeger See Documentation/input/joydev/joystick.rst. 2010e52347bdSJani Nikula 2011e52347bdSJani Nikula nokaslr [KNL] 2012e52347bdSJani Nikula When CONFIG_RANDOMIZE_BASE is set, this disables 2013e52347bdSJani Nikula kernel and module base offset ASLR (Address Space 2014e52347bdSJani Nikula Layout Randomization). 2015e52347bdSJani Nikula 2016b0845ce5SMark Rutland kasan_multi_shot 2017b0845ce5SMark Rutland [KNL] Enforce KASAN (Kernel Address Sanitizer) to print 2018b0845ce5SMark Rutland report on every invalid memory access. Without this 2019b0845ce5SMark Rutland parameter KASAN will print report only for the first 2020b0845ce5SMark Rutland invalid access. 2021b0845ce5SMark Rutland 2022e52347bdSJani Nikula keepinitrd [HW,ARM] 2023e52347bdSJani Nikula 2024e52347bdSJani Nikula kernelcore= [KNL,X86,IA-64,PPC] 2025a5c6d650SDavid Rientjes Format: nn[KMGTPE] | nn% | "mirror" 2026a5c6d650SDavid Rientjes This parameter specifies the amount of memory usable by 2027a5c6d650SDavid Rientjes the kernel for non-movable allocations. The requested 2028a5c6d650SDavid Rientjes amount is spread evenly throughout all nodes in the 2029a5c6d650SDavid Rientjes system as ZONE_NORMAL. The remaining memory is used for 2030a5c6d650SDavid Rientjes movable memory in its own zone, ZONE_MOVABLE. In the 2031a5c6d650SDavid Rientjes event, a node is too small to have both ZONE_NORMAL and 2032a5c6d650SDavid Rientjes ZONE_MOVABLE, kernelcore memory will take priority and 2033a5c6d650SDavid Rientjes other nodes will have a larger ZONE_MOVABLE. 2034a5c6d650SDavid Rientjes 2035a5c6d650SDavid Rientjes ZONE_MOVABLE is used for the allocation of pages that 2036a5c6d650SDavid Rientjes may be reclaimed or moved by the page migration 2037a5c6d650SDavid Rientjes subsystem. Note that allocations like PTEs-from-HighMem 2038a5c6d650SDavid Rientjes still use the HighMem zone if it exists, and the Normal 2039e52347bdSJani Nikula zone if it does not. 2040e52347bdSJani Nikula 2041a5c6d650SDavid Rientjes It is possible to specify the exact amount of memory in 2042a5c6d650SDavid Rientjes the form of "nn[KMGTPE]", a percentage of total system 2043a5c6d650SDavid Rientjes memory in the form of "nn%", or "mirror". If "mirror" 2044e52347bdSJani Nikula option is specified, mirrored (reliable) memory is used 2045e52347bdSJani Nikula for non-movable allocations and remaining memory is used 2046a5c6d650SDavid Rientjes for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" 2047a5c6d650SDavid Rientjes are exclusive, so you cannot specify multiple forms. 2048e52347bdSJani Nikula 2049e52347bdSJani Nikula kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. 2050e52347bdSJani Nikula Format: <Controller#>[,poll interval] 2051e52347bdSJani Nikula The controller # is the number of the ehci usb debug 2052e52347bdSJani Nikula port as it is probed via PCI. The poll interval is 2053e52347bdSJani Nikula optional and is the number seconds in between 2054e52347bdSJani Nikula each poll cycle to the debug port in case you need 2055e52347bdSJani Nikula the functionality for interrupting the kernel with 2056e52347bdSJani Nikula gdb or control-c on the dbgp connection. When 2057e52347bdSJani Nikula not using this parameter you use sysrq-g to break into 2058e52347bdSJani Nikula the kernel debugger. 2059e52347bdSJani Nikula 2060e52347bdSJani Nikula kgdboc= [KGDB,HW] kgdb over consoles. 2061e52347bdSJani Nikula Requires a tty driver that supports console polling, 2062e52347bdSJani Nikula or a supported polling keyboard driver (non-usb). 2063e52347bdSJani Nikula Serial only format: <serial_device>[,baud] 2064e52347bdSJani Nikula keyboard only format: kbd 2065e52347bdSJani Nikula keyboard and serial format: kbd,<serial_device>[,baud] 2066e52347bdSJani Nikula Optional Kernel mode setting: 2067e52347bdSJani Nikula kms, kbd format: kms,kbd 2068e52347bdSJani Nikula kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] 2069e52347bdSJani Nikula 2070e52347bdSJani Nikula kgdbwait [KGDB] Stop kernel execution and enter the 2071e52347bdSJani Nikula kernel debugger at the earliest opportunity. 2072e52347bdSJani Nikula 2073e52347bdSJani Nikula kmac= [MIPS] korina ethernet MAC address. 2074e52347bdSJani Nikula Configure the RouterBoard 532 series on-chip 2075e52347bdSJani Nikula Ethernet adapter MAC address. 2076e52347bdSJani Nikula 2077e52347bdSJani Nikula kmemleak= [KNL] Boot-time kmemleak enable/disable 2078e52347bdSJani Nikula Valid arguments: on, off 2079e52347bdSJani Nikula Default: on 2080e52347bdSJani Nikula Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, 2081e52347bdSJani Nikula the default is off. 2082e52347bdSJani Nikula 2083970988e1SMasami Hiramatsu kprobe_event=[probe-list] 2084970988e1SMasami Hiramatsu [FTRACE] Add kprobe events and enable at boot time. 2085970988e1SMasami Hiramatsu The probe-list is a semicolon delimited list of probe 2086970988e1SMasami Hiramatsu definitions. Each definition is same as kprobe_events 2087970988e1SMasami Hiramatsu interface, but the parameters are comma delimited. 2088970988e1SMasami Hiramatsu For example, to add a kprobe event on vfs_read with 2089970988e1SMasami Hiramatsu arg1 and arg2, add to the command line; 2090970988e1SMasami Hiramatsu 2091970988e1SMasami Hiramatsu kprobe_event=p,vfs_read,$arg1,$arg2 2092970988e1SMasami Hiramatsu 2093970988e1SMasami Hiramatsu See also Documentation/trace/kprobetrace.rst "Kernel 2094970988e1SMasami Hiramatsu Boot Parameter" section. 2095970988e1SMasami Hiramatsu 2096de190555SJeremy Linton kpti= [ARM64] Control page table isolation of user 2097de190555SJeremy Linton and kernel address spaces. 2098de190555SJeremy Linton Default: enabled on cores which need mitigation. 2099de190555SJeremy Linton 0: force disabled 2100de190555SJeremy Linton 1: force enabled 2101de190555SJeremy Linton 2102e52347bdSJani Nikula kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. 2103e52347bdSJani Nikula Default is 0 (don't ignore, but inject #GP) 2104e52347bdSJani Nikula 2105c4ae60e4SLiran Alon kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface. 2106c4ae60e4SLiran Alon Default is false (don't support). 2107c4ae60e4SLiran Alon 2108e52347bdSJani Nikula kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit 2109e52347bdSJani Nikula KVM MMU at runtime. 2110e52347bdSJani Nikula Default is 0 (off) 2111e52347bdSJani Nikula 2112b8e8c830SPaolo Bonzini kvm.nx_huge_pages= 2113b8e8c830SPaolo Bonzini [KVM] Controls the software workaround for the 2114b8e8c830SPaolo Bonzini X86_BUG_ITLB_MULTIHIT bug. 2115b8e8c830SPaolo Bonzini force : Always deploy workaround. 2116b8e8c830SPaolo Bonzini off : Never deploy workaround. 2117b8e8c830SPaolo Bonzini auto : Deploy workaround based on the presence of 2118b8e8c830SPaolo Bonzini X86_BUG_ITLB_MULTIHIT. 2119b8e8c830SPaolo Bonzini 2120b8e8c830SPaolo Bonzini Default is 'auto'. 2121b8e8c830SPaolo Bonzini 2122b8e8c830SPaolo Bonzini If the software workaround is enabled for the host, 2123b8e8c830SPaolo Bonzini guests do need not to enable it for nested guests. 2124b8e8c830SPaolo Bonzini 21251aa9b957SJunaid Shahid kvm.nx_huge_pages_recovery_ratio= 21261aa9b957SJunaid Shahid [KVM] Controls how many 4KiB pages are periodically zapped 21271aa9b957SJunaid Shahid back to huge pages. 0 disables the recovery, otherwise if 21281aa9b957SJunaid Shahid the value is N KVM will zap 1/Nth of the 4KiB pages every 21291aa9b957SJunaid Shahid minute. The default is 60. 21301aa9b957SJunaid Shahid 2131e52347bdSJani Nikula kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. 2132e52347bdSJani Nikula Default is 1 (enabled) 2133e52347bdSJani Nikula 2134e52347bdSJani Nikula kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) 2135e52347bdSJani Nikula for all guests. 2136e52347bdSJani Nikula Default is 1 (enabled) if in 64-bit or 32-bit PAE mode. 2137e52347bdSJani Nikula 2138e23f62f7SMarc Zyngier kvm-arm.vgic_v3_group0_trap= 2139e23f62f7SMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 group-0 2140e23f62f7SMarc Zyngier system registers 2141e23f62f7SMarc Zyngier 2142182936eeSMarc Zyngier kvm-arm.vgic_v3_group1_trap= 2143182936eeSMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 group-1 2144182936eeSMarc Zyngier system registers 2145182936eeSMarc Zyngier 2146ff89511eSMarc Zyngier kvm-arm.vgic_v3_common_trap= 2147ff89511eSMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 common 2148ff89511eSMarc Zyngier system registers 2149ff89511eSMarc Zyngier 2150a7546054SMarc Zyngier kvm-arm.vgic_v4_enable= 2151a7546054SMarc Zyngier [KVM,ARM] Allow use of GICv4 for direct injection of 2152a7546054SMarc Zyngier LPIs. 2153a7546054SMarc Zyngier 2154e52347bdSJani Nikula kvm-intel.ept= [KVM,Intel] Disable extended page tables 2155e52347bdSJani Nikula (virtualized MMU) support on capable Intel chips. 2156e52347bdSJani Nikula Default is 1 (enabled) 2157e52347bdSJani Nikula 2158e52347bdSJani Nikula kvm-intel.emulate_invalid_guest_state= 2159e52347bdSJani Nikula [KVM,Intel] Enable emulation of invalid guest states 2160e52347bdSJani Nikula Default is 0 (disabled) 2161e52347bdSJani Nikula 2162e52347bdSJani Nikula kvm-intel.flexpriority= 2163e52347bdSJani Nikula [KVM,Intel] Disable FlexPriority feature (TPR shadow). 2164e52347bdSJani Nikula Default is 1 (enabled) 2165e52347bdSJani Nikula 2166e52347bdSJani Nikula kvm-intel.nested= 2167e52347bdSJani Nikula [KVM,Intel] Enable VMX nesting (nVMX). 2168e52347bdSJani Nikula Default is 0 (disabled) 2169e52347bdSJani Nikula 2170e52347bdSJani Nikula kvm-intel.unrestricted_guest= 2171e52347bdSJani Nikula [KVM,Intel] Disable unrestricted guest feature 2172e52347bdSJani Nikula (virtualized real and unpaged mode) on capable 2173e52347bdSJani Nikula Intel chips. Default is 1 (enabled) 2174e52347bdSJani Nikula 2175a399477eSKonrad Rzeszutek Wilk kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault 2176a399477eSKonrad Rzeszutek Wilk CVE-2018-3620. 2177a399477eSKonrad Rzeszutek Wilk 2178a399477eSKonrad Rzeszutek Wilk Valid arguments: never, cond, always 2179a399477eSKonrad Rzeszutek Wilk 2180a399477eSKonrad Rzeszutek Wilk always: L1D cache flush on every VMENTER. 2181a399477eSKonrad Rzeszutek Wilk cond: Flush L1D on VMENTER only when the code between 2182a399477eSKonrad Rzeszutek Wilk VMEXIT and VMENTER can leak host memory. 2183a399477eSKonrad Rzeszutek Wilk never: Disables the mitigation 2184a399477eSKonrad Rzeszutek Wilk 2185a399477eSKonrad Rzeszutek Wilk Default is cond (do L1 cache flush in specific instances) 2186a399477eSKonrad Rzeszutek Wilk 2187e52347bdSJani Nikula kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification 2188e52347bdSJani Nikula feature (tagged TLBs) on capable Intel chips. 2189e52347bdSJani Nikula Default is 1 (enabled) 2190e52347bdSJani Nikula 2191d90a7a0eSJiri Kosina l1tf= [X86] Control mitigation of the L1TF vulnerability on 2192d90a7a0eSJiri Kosina affected CPUs 2193d90a7a0eSJiri Kosina 2194d90a7a0eSJiri Kosina The kernel PTE inversion protection is unconditionally 2195d90a7a0eSJiri Kosina enabled and cannot be disabled. 2196d90a7a0eSJiri Kosina 2197d90a7a0eSJiri Kosina full 2198d90a7a0eSJiri Kosina Provides all available mitigations for the 2199d90a7a0eSJiri Kosina L1TF vulnerability. Disables SMT and 2200d90a7a0eSJiri Kosina enables all mitigations in the 2201d90a7a0eSJiri Kosina hypervisors, i.e. unconditional L1D flush. 2202d90a7a0eSJiri Kosina 2203d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2204d90a7a0eSJiri Kosina sysfs interface is still possible after 2205d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2206d90a7a0eSJiri Kosina when the first VM is started in a 2207d90a7a0eSJiri Kosina potentially insecure configuration, 2208d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2209d90a7a0eSJiri Kosina 2210d90a7a0eSJiri Kosina full,force 2211d90a7a0eSJiri Kosina Same as 'full', but disables SMT and L1D 2212d90a7a0eSJiri Kosina flush runtime control. Implies the 2213d90a7a0eSJiri Kosina 'nosmt=force' command line option. 2214d90a7a0eSJiri Kosina (i.e. sysfs control of SMT is disabled.) 2215d90a7a0eSJiri Kosina 2216d90a7a0eSJiri Kosina flush 2217d90a7a0eSJiri Kosina Leaves SMT enabled and enables the default 2218d90a7a0eSJiri Kosina hypervisor mitigation, i.e. conditional 2219d90a7a0eSJiri Kosina L1D flush. 2220d90a7a0eSJiri Kosina 2221d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2222d90a7a0eSJiri Kosina sysfs interface is still possible after 2223d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2224d90a7a0eSJiri Kosina when the first VM is started in a 2225d90a7a0eSJiri Kosina potentially insecure configuration, 2226d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2227d90a7a0eSJiri Kosina 2228d90a7a0eSJiri Kosina flush,nosmt 2229d90a7a0eSJiri Kosina 2230d90a7a0eSJiri Kosina Disables SMT and enables the default 2231d90a7a0eSJiri Kosina hypervisor mitigation. 2232d90a7a0eSJiri Kosina 2233d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2234d90a7a0eSJiri Kosina sysfs interface is still possible after 2235d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2236d90a7a0eSJiri Kosina when the first VM is started in a 2237d90a7a0eSJiri Kosina potentially insecure configuration, 2238d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2239d90a7a0eSJiri Kosina 2240d90a7a0eSJiri Kosina flush,nowarn 2241d90a7a0eSJiri Kosina Same as 'flush', but hypervisors will not 2242d90a7a0eSJiri Kosina warn when a VM is started in a potentially 2243d90a7a0eSJiri Kosina insecure configuration. 2244d90a7a0eSJiri Kosina 2245d90a7a0eSJiri Kosina off 2246d90a7a0eSJiri Kosina Disables hypervisor mitigations and doesn't 2247d90a7a0eSJiri Kosina emit any warnings. 22485b5e4d62SMichal Hocko It also drops the swap size and available 22495b5e4d62SMichal Hocko RAM limit restriction on both hypervisor and 22505b5e4d62SMichal Hocko bare metal. 2251d90a7a0eSJiri Kosina 2252d90a7a0eSJiri Kosina Default is 'flush'. 2253d90a7a0eSJiri Kosina 225465fd4cb6SThomas Gleixner For details see: Documentation/admin-guide/hw-vuln/l1tf.rst 2255d90a7a0eSJiri Kosina 2256e52347bdSJani Nikula l2cr= [PPC] 2257e52347bdSJani Nikula 2258e52347bdSJani Nikula l3cr= [PPC] 2259e52347bdSJani Nikula 2260e52347bdSJani Nikula lapic [X86-32,APIC] Enable the local APIC even if BIOS 2261e52347bdSJani Nikula disabled it. 2262e52347bdSJani Nikula 2263e52347bdSJani Nikula lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline 2264e52347bdSJani Nikula value for LAPIC timer one-shot implementation. Default 2265e52347bdSJani Nikula back to the programmable timer unit in the LAPIC. 2266e52347bdSJani Nikula 2267e52347bdSJani Nikula lapic_timer_c2_ok [X86,APIC] trust the local apic timer 2268e52347bdSJani Nikula in C2 power state. 2269e52347bdSJani Nikula 2270e52347bdSJani Nikula libata.dma= [LIBATA] DMA control 2271e52347bdSJani Nikula libata.dma=0 Disable all PATA and SATA DMA 2272e52347bdSJani Nikula libata.dma=1 PATA and SATA Disk DMA only 2273e52347bdSJani Nikula libata.dma=2 ATAPI (CDROM) DMA only 2274e52347bdSJani Nikula libata.dma=4 Compact Flash DMA only 2275e52347bdSJani Nikula Combinations also work, so libata.dma=3 enables DMA 2276e52347bdSJani Nikula for disks and CDROMs, but not CFs. 2277e52347bdSJani Nikula 2278e52347bdSJani Nikula libata.ignore_hpa= [LIBATA] Ignore HPA limit 2279e52347bdSJani Nikula libata.ignore_hpa=0 keep BIOS limits (default) 2280e52347bdSJani Nikula libata.ignore_hpa=1 ignore limits, using full disk 2281e52347bdSJani Nikula 2282e52347bdSJani Nikula libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 2283e52347bdSJani Nikula when set. 2284e52347bdSJani Nikula Format: <int> 2285e52347bdSJani Nikula 2286e52347bdSJani Nikula libata.force= [LIBATA] Force configurations. The format is comma 2287e52347bdSJani Nikula separated list of "[ID:]VAL" where ID is 2288e52347bdSJani Nikula PORT[.DEVICE]. PORT and DEVICE are decimal numbers 2289e52347bdSJani Nikula matching port, link or device. Basically, it matches 2290e52347bdSJani Nikula the ATA ID string printed on console by libata. If 2291e52347bdSJani Nikula the whole ID part is omitted, the last PORT and DEVICE 2292e52347bdSJani Nikula values are used. If ID hasn't been specified yet, the 2293e52347bdSJani Nikula configuration applies to all ports, links and devices. 2294e52347bdSJani Nikula 2295e52347bdSJani Nikula If only DEVICE is omitted, the parameter applies to 2296e52347bdSJani Nikula the port and all links and devices behind it. DEVICE 2297e52347bdSJani Nikula number of 0 either selects the first device or the 2298e52347bdSJani Nikula first fan-out link behind PMP device. It does not 2299e52347bdSJani Nikula select the host link. DEVICE number of 15 selects the 2300e52347bdSJani Nikula host link and device attached to it. 2301e52347bdSJani Nikula 2302e52347bdSJani Nikula The VAL specifies the configuration to force. As long 2303e52347bdSJani Nikula as there's no ambiguity shortcut notation is allowed. 2304e52347bdSJani Nikula For example, both 1.5 and 1.5G would work for 1.5Gbps. 2305e52347bdSJani Nikula The following configurations can be forced. 2306e52347bdSJani Nikula 2307e52347bdSJani Nikula * Cable type: 40c, 80c, short40c, unk, ign or sata. 2308e52347bdSJani Nikula Any ID with matching PORT is used. 2309e52347bdSJani Nikula 2310e52347bdSJani Nikula * SATA link speed limit: 1.5Gbps or 3.0Gbps. 2311e52347bdSJani Nikula 2312e52347bdSJani Nikula * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 2313e52347bdSJani Nikula udma[/][16,25,33,44,66,100,133] notation is also 2314e52347bdSJani Nikula allowed. 2315e52347bdSJani Nikula 2316e52347bdSJani Nikula * [no]ncq: Turn on or off NCQ. 2317e52347bdSJani Nikula 2318e52347bdSJani Nikula * [no]ncqtrim: Turn off queued DSM TRIM. 2319e52347bdSJani Nikula 2320e52347bdSJani Nikula * nohrst, nosrst, norst: suppress hard, soft 2321e52347bdSJani Nikula and both resets. 2322e52347bdSJani Nikula 2323e52347bdSJani Nikula * rstonce: only attempt one reset during 2324e52347bdSJani Nikula hot-unplug link recovery 2325e52347bdSJani Nikula 2326e52347bdSJani Nikula * dump_id: dump IDENTIFY data. 2327e52347bdSJani Nikula 2328e52347bdSJani Nikula * atapi_dmadir: Enable ATAPI DMADIR bridge support 2329e52347bdSJani Nikula 2330e52347bdSJani Nikula * disable: Disable this device. 2331e52347bdSJani Nikula 2332e52347bdSJani Nikula If there are multiple matching configurations changing 2333e52347bdSJani Nikula the same attribute, the last one is used. 2334e52347bdSJani Nikula 2335e52347bdSJani Nikula memblock=debug [KNL] Enable memblock debug messages. 2336e52347bdSJani Nikula 2337e52347bdSJani Nikula load_ramdisk= [RAM] List of ramdisks to load from floppy 2338e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/ramdisk.rst. 2339e52347bdSJani Nikula 2340e52347bdSJani Nikula lockd.nlm_grace_period=P [NFS] Assign grace period. 2341e52347bdSJani Nikula Format: <integer> 2342e52347bdSJani Nikula 2343e52347bdSJani Nikula lockd.nlm_tcpport=N [NFS] Assign TCP port. 2344e52347bdSJani Nikula Format: <integer> 2345e52347bdSJani Nikula 2346e52347bdSJani Nikula lockd.nlm_timeout=T [NFS] Assign timeout value. 2347e52347bdSJani Nikula Format: <integer> 2348e52347bdSJani Nikula 2349e52347bdSJani Nikula lockd.nlm_udpport=M [NFS] Assign UDP port. 2350e52347bdSJani Nikula Format: <integer> 2351e52347bdSJani Nikula 2352000d388eSMatthew Garrett lockdown= [SECURITY] 2353000d388eSMatthew Garrett { integrity | confidentiality } 2354000d388eSMatthew Garrett Enable the kernel lockdown feature. If set to 2355000d388eSMatthew Garrett integrity, kernel features that allow userland to 2356000d388eSMatthew Garrett modify the running kernel are disabled. If set to 2357000d388eSMatthew Garrett confidentiality, kernel features that allow userland 2358000d388eSMatthew Garrett to extract confidential information from the kernel 2359000d388eSMatthew Garrett are also disabled. 2360000d388eSMatthew Garrett 2361e52347bdSJani Nikula locktorture.nreaders_stress= [KNL] 2362e52347bdSJani Nikula Set the number of locking read-acquisition kthreads. 2363e52347bdSJani Nikula Defaults to being automatically set based on the 2364e52347bdSJani Nikula number of online CPUs. 2365e52347bdSJani Nikula 2366e52347bdSJani Nikula locktorture.nwriters_stress= [KNL] 2367e52347bdSJani Nikula Set the number of locking write-acquisition kthreads. 2368e52347bdSJani Nikula 2369e52347bdSJani Nikula locktorture.onoff_holdoff= [KNL] 2370e52347bdSJani Nikula Set time (s) after boot for CPU-hotplug testing. 2371e52347bdSJani Nikula 2372e52347bdSJani Nikula locktorture.onoff_interval= [KNL] 2373e52347bdSJani Nikula Set time (s) between CPU-hotplug operations, or 2374e52347bdSJani Nikula zero to disable CPU-hotplug testing. 2375e52347bdSJani Nikula 2376e52347bdSJani Nikula locktorture.shuffle_interval= [KNL] 2377e52347bdSJani Nikula Set task-shuffle interval (jiffies). Shuffling 2378e52347bdSJani Nikula tasks allows some CPUs to go into dyntick-idle 2379e52347bdSJani Nikula mode during the locktorture test. 2380e52347bdSJani Nikula 2381e52347bdSJani Nikula locktorture.shutdown_secs= [KNL] 2382e52347bdSJani Nikula Set time (s) after boot system shutdown. This 2383e52347bdSJani Nikula is useful for hands-off automated testing. 2384e52347bdSJani Nikula 2385e52347bdSJani Nikula locktorture.stat_interval= [KNL] 2386e52347bdSJani Nikula Time (s) between statistics printk()s. 2387e52347bdSJani Nikula 2388e52347bdSJani Nikula locktorture.stutter= [KNL] 2389e52347bdSJani Nikula Time (s) to stutter testing, for example, 2390e52347bdSJani Nikula specifying five seconds causes the test to run for 2391e52347bdSJani Nikula five seconds, wait for five seconds, and so on. 2392e52347bdSJani Nikula This tests the locking primitive's ability to 2393e52347bdSJani Nikula transition abruptly to and from idle. 2394e52347bdSJani Nikula 2395e52347bdSJani Nikula locktorture.torture_type= [KNL] 2396e52347bdSJani Nikula Specify the locking implementation to test. 2397e52347bdSJani Nikula 2398e52347bdSJani Nikula locktorture.verbose= [KNL] 2399e52347bdSJani Nikula Enable additional printk() statements. 2400e52347bdSJani Nikula 2401e52347bdSJani Nikula logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 2402e52347bdSJani Nikula Format: <irq> 2403e52347bdSJani Nikula 2404e52347bdSJani Nikula loglevel= All Kernel Messages with a loglevel smaller than the 2405e52347bdSJani Nikula console loglevel will be printed to the console. It can 2406e52347bdSJani Nikula also be changed with klogd or other programs. The 2407e52347bdSJani Nikula loglevels are defined as follows: 2408e52347bdSJani Nikula 2409e52347bdSJani Nikula 0 (KERN_EMERG) system is unusable 2410e52347bdSJani Nikula 1 (KERN_ALERT) action must be taken immediately 2411e52347bdSJani Nikula 2 (KERN_CRIT) critical conditions 2412e52347bdSJani Nikula 3 (KERN_ERR) error conditions 2413e52347bdSJani Nikula 4 (KERN_WARNING) warning conditions 2414e52347bdSJani Nikula 5 (KERN_NOTICE) normal but significant condition 2415e52347bdSJani Nikula 6 (KERN_INFO) informational 2416e52347bdSJani Nikula 7 (KERN_DEBUG) debug-level messages 2417e52347bdSJani Nikula 2418e52347bdSJani Nikula log_buf_len=n[KMG] Sets the size of the printk ring buffer, 2419e52347bdSJani Nikula in bytes. n must be a power of two and greater 2420e52347bdSJani Nikula than the minimal size. The minimal size is defined 2421e52347bdSJani Nikula by LOG_BUF_SHIFT kernel config parameter. There is 2422e52347bdSJani Nikula also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter 2423e52347bdSJani Nikula that allows to increase the default size depending on 2424e52347bdSJani Nikula the number of CPUs. See init/Kconfig for more details. 2425e52347bdSJani Nikula 2426e52347bdSJani Nikula logo.nologo [FB] Disables display of the built-in Linux logo. 2427e52347bdSJani Nikula This may be used to provide more screen space for 2428e52347bdSJani Nikula kernel log messages and is useful when debugging 2429e52347bdSJani Nikula kernel boot problems. 2430e52347bdSJani Nikula 2431e52347bdSJani Nikula lp=0 [LP] Specify parallel ports to use, e.g, 2432e52347bdSJani Nikula lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 2433e52347bdSJani Nikula lp=reset first parallel port). 'lp=0' disables the 2434e52347bdSJani Nikula lp=auto printer driver. 'lp=reset' (which can be 2435e52347bdSJani Nikula specified in addition to the ports) causes 2436e52347bdSJani Nikula attached printers to be reset. Using 2437e52347bdSJani Nikula lp=port1,port2,... specifies the parallel ports 2438e52347bdSJani Nikula to associate lp devices with, starting with 2439e52347bdSJani Nikula lp0. A port specification may be 'none' to skip 2440e52347bdSJani Nikula that lp device, or a parport name such as 2441e52347bdSJani Nikula 'parport0'. Specifying 'lp=auto' instead of a 2442e52347bdSJani Nikula port specification list means that device IDs 2443e52347bdSJani Nikula from each port should be examined, to see if 2444e52347bdSJani Nikula an IEEE 1284-compliant printer is attached; if 2445e52347bdSJani Nikula so, the driver will manage that printer. 2446e52347bdSJani Nikula See also header of drivers/char/lp.c. 2447e52347bdSJani Nikula 2448e52347bdSJani Nikula lpj=n [KNL] 2449e52347bdSJani Nikula Sets loops_per_jiffy to given constant, thus avoiding 2450e52347bdSJani Nikula time-consuming boot-time autodetection (up to 250 ms per 2451e52347bdSJani Nikula CPU). 0 enables autodetection (default). To determine 2452e52347bdSJani Nikula the correct value for your kernel, boot with normal 2453e52347bdSJani Nikula autodetection and see what value is printed. Note that 2454e52347bdSJani Nikula on SMP systems the preset will be applied to all CPUs, 2455e52347bdSJani Nikula which is likely to cause problems if your CPUs need 2456e52347bdSJani Nikula significantly divergent settings. An incorrect value 2457e52347bdSJani Nikula will cause delays in the kernel to be wrong, leading to 2458e52347bdSJani Nikula unpredictable I/O errors and other breakage. Although 2459e52347bdSJani Nikula unlikely, in the extreme case this might damage your 2460e52347bdSJani Nikula hardware. 2461e52347bdSJani Nikula 2462e52347bdSJani Nikula ltpc= [NET] 2463e52347bdSJani Nikula Format: <io>,<irq>,<dma> 2464e52347bdSJani Nikula 24659b8c7c14SKees Cook lsm.debug [SECURITY] Enable LSM initialization debugging output. 24669b8c7c14SKees Cook 246779f7865dSKees Cook lsm=lsm1,...,lsmN 246879f7865dSKees Cook [SECURITY] Choose order of LSM initialization. This 246989a9684eSKees Cook overrides CONFIG_LSM, and the "security=" parameter. 247079f7865dSKees Cook 2471e52347bdSJani Nikula machvec= [IA-64] Force the use of a particular machine-vector 2472e52347bdSJani Nikula (machvec) in a generic kernel. 2473df43acacSChristoph Hellwig Example: machvec=hpzx1 2474e52347bdSJani Nikula 2475e52347bdSJani Nikula machtype= [Loongson] Share the same kernel image file between different 2476e52347bdSJani Nikula yeeloong laptop. 2477e52347bdSJani Nikula Example: machtype=lemote-yeeloong-2f-7inch 2478e52347bdSJani Nikula 2479e52347bdSJani Nikula max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater 2480e52347bdSJani Nikula than or equal to this physical address is ignored. 2481e52347bdSJani Nikula 2482e52347bdSJani Nikula maxcpus= [SMP] Maximum number of processors that an SMP kernel 2483e52347bdSJani Nikula will bring up during bootup. maxcpus=n : n >= 0 limits 2484e52347bdSJani Nikula the kernel to bring up 'n' processors. Surely after 2485e52347bdSJani Nikula bootup you can bring up the other plugged cpu by executing 2486e52347bdSJani Nikula "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus 2487e52347bdSJani Nikula only takes effect during system bootup. 2488e52347bdSJani Nikula While n=0 is a special case, it is equivalent to "nosmp", 2489e52347bdSJani Nikula which also disables the IO APIC. 2490e52347bdSJani Nikula 2491e52347bdSJani Nikula max_loop= [LOOP] The number of loop block devices that get 2492e52347bdSJani Nikula (loop.max_loop) unconditionally pre-created at init time. The default 2493e52347bdSJani Nikula number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead 2494e52347bdSJani Nikula of statically allocating a predefined number, loop 2495e52347bdSJani Nikula devices can be requested on-demand with the 2496e52347bdSJani Nikula /dev/loop-control interface. 2497e52347bdSJani Nikula 2498e52347bdSJani Nikula mce [X86-32] Machine Check Exception 2499e52347bdSJani Nikula 2500cb1aaebeSMauro Carvalho Chehab mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst 2501e52347bdSJani Nikula 2502e52347bdSJani Nikula md= [HW] RAID subsystems devices and level 2503e52347bdSJani Nikula See Documentation/admin-guide/md.rst. 2504e52347bdSJani Nikula 2505e52347bdSJani Nikula mdacon= [MDA] 2506e52347bdSJani Nikula Format: <first>,<last> 2507e52347bdSJani Nikula Specifies range of consoles to be captured by the MDA. 2508e52347bdSJani Nikula 2509bc124170SThomas Gleixner mds= [X86,INTEL] 2510bc124170SThomas Gleixner Control mitigation for the Micro-architectural Data 2511bc124170SThomas Gleixner Sampling (MDS) vulnerability. 2512bc124170SThomas Gleixner 2513bc124170SThomas Gleixner Certain CPUs are vulnerable to an exploit against CPU 2514bc124170SThomas Gleixner internal buffers which can forward information to a 2515bc124170SThomas Gleixner disclosure gadget under certain conditions. 2516bc124170SThomas Gleixner 2517bc124170SThomas Gleixner In vulnerable processors, the speculatively 2518bc124170SThomas Gleixner forwarded data can be used in a cache side channel 2519bc124170SThomas Gleixner attack, to access data to which the attacker does 2520bc124170SThomas Gleixner not have direct access. 2521bc124170SThomas Gleixner 2522bc124170SThomas Gleixner This parameter controls the MDS mitigation. The 2523bc124170SThomas Gleixner options are: 2524bc124170SThomas Gleixner 2525bc124170SThomas Gleixner full - Enable MDS mitigation on vulnerable CPUs 2526d71eb0ceSJosh Poimboeuf full,nosmt - Enable MDS mitigation and disable 2527d71eb0ceSJosh Poimboeuf SMT on vulnerable CPUs 2528bc124170SThomas Gleixner off - Unconditionally disable MDS mitigation 2529bc124170SThomas Gleixner 253064870ed1SWaiman Long On TAA-affected machines, mds=off can be prevented by 253164870ed1SWaiman Long an active TAA mitigation as both vulnerabilities are 253264870ed1SWaiman Long mitigated with the same mechanism so in order to disable 253364870ed1SWaiman Long this mitigation, you need to specify tsx_async_abort=off 253464870ed1SWaiman Long too. 253564870ed1SWaiman Long 2536bc124170SThomas Gleixner Not specifying this option is equivalent to 2537bc124170SThomas Gleixner mds=full. 2538bc124170SThomas Gleixner 25395999bbe7SThomas Gleixner For details see: Documentation/admin-guide/hw-vuln/mds.rst 25405999bbe7SThomas Gleixner 2541e52347bdSJani Nikula mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 2542e52347bdSJani Nikula Amount of memory to be used when the kernel is not able 2543e52347bdSJani Nikula to see the whole system memory or for test. 2544e52347bdSJani Nikula [X86] Work as limiting max address. Use together 2545e52347bdSJani Nikula with memmap= to avoid physical address space collisions. 2546e52347bdSJani Nikula Without memmap= PCI devices could be placed at addresses 2547e52347bdSJani Nikula belonging to unused RAM. 2548e52347bdSJani Nikula 2549e52347bdSJani Nikula mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 2550e52347bdSJani Nikula memory. 2551e52347bdSJani Nikula 2552e52347bdSJani Nikula memchunk=nn[KMG] 2553e52347bdSJani Nikula [KNL,SH] Allow user to override the default size for 2554e52347bdSJani Nikula per-device physically contiguous DMA buffers. 2555e52347bdSJani Nikula 2556e52347bdSJani Nikula memhp_default_state=online/offline 2557e52347bdSJani Nikula [KNL] Set the initial state for the memory hotplug 2558e52347bdSJani Nikula onlining policy. If not specified, the default value is 2559e52347bdSJani Nikula set according to the 2560e52347bdSJani Nikula CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config 2561e52347bdSJani Nikula option. 2562cb1aaebeSMauro Carvalho Chehab See Documentation/admin-guide/mm/memory-hotplug.rst. 2563e52347bdSJani Nikula 2564e52347bdSJani Nikula memmap=exactmap [KNL,X86] Enable setting of an exact 2565e52347bdSJani Nikula E820 memory map, as specified by the user. 2566e52347bdSJani Nikula Such memmap=exactmap lines can be constructed based on 2567e52347bdSJani Nikula BIOS output or other requirements. See the memmap=nn@ss 2568e52347bdSJani Nikula option description. 2569e52347bdSJani Nikula 2570e52347bdSJani Nikula memmap=nn[KMG]@ss[KMG] 2571e52347bdSJani Nikula [KNL] Force usage of a specific region of memory. 2572e52347bdSJani Nikula Region of memory to be used is from ss to ss+nn. 25738fcc9bc3SBaoquan He If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG], 25748fcc9bc3SBaoquan He which limits max address to nn[KMG]. 25758fcc9bc3SBaoquan He Multiple different regions can be specified, 25768fcc9bc3SBaoquan He comma delimited. 25778fcc9bc3SBaoquan He Example: 25788fcc9bc3SBaoquan He memmap=100M@2G,100M#3G,1G!1024G 2579e52347bdSJani Nikula 2580e52347bdSJani Nikula memmap=nn[KMG]#ss[KMG] 2581e52347bdSJani Nikula [KNL,ACPI] Mark specific memory as ACPI data. 2582e52347bdSJani Nikula Region of memory to be marked is from ss to ss+nn. 2583e52347bdSJani Nikula 2584e52347bdSJani Nikula memmap=nn[KMG]$ss[KMG] 2585e52347bdSJani Nikula [KNL,ACPI] Mark specific memory as reserved. 2586e52347bdSJani Nikula Region of memory to be reserved is from ss to ss+nn. 2587e52347bdSJani Nikula Example: Exclude memory from 0x18690000-0x1869ffff 2588e52347bdSJani Nikula memmap=64K$0x18690000 2589e52347bdSJani Nikula or 2590e52347bdSJani Nikula memmap=0x10000$0x18690000 25918fcc9bc3SBaoquan He Some bootloaders may need an escape character before '$', 25928fcc9bc3SBaoquan He like Grub2, otherwise '$' and the following number 25938fcc9bc3SBaoquan He will be eaten. 2594e52347bdSJani Nikula 2595e52347bdSJani Nikula memmap=nn[KMG]!ss[KMG] 2596e52347bdSJani Nikula [KNL,X86] Mark specific memory as protected. 2597e52347bdSJani Nikula Region of memory to be used, from ss to ss+nn. 2598e52347bdSJani Nikula The memory region may be marked as e820 type 12 (0xc) 2599e52347bdSJani Nikula and is NVDIMM or ADR memory. 2600e52347bdSJani Nikula 2601ef61f8a3SJan H. Schönherr memmap=<size>%<offset>-<oldtype>+<newtype> 2602ef61f8a3SJan H. Schönherr [KNL,ACPI] Convert memory within the specified region 2603ef61f8a3SJan H. Schönherr from <oldtype> to <newtype>. If "-<oldtype>" is left 2604ef61f8a3SJan H. Schönherr out, the whole region will be marked as <newtype>, 2605ef61f8a3SJan H. Schönherr even if previously unavailable. If "+<newtype>" is left 2606ef61f8a3SJan H. Schönherr out, matching memory will be removed. Types are 2607ef61f8a3SJan H. Schönherr specified as e820 types, e.g., 1 = RAM, 2 = reserved, 2608ef61f8a3SJan H. Schönherr 3 = ACPI, 12 = PRAM. 2609ef61f8a3SJan H. Schönherr 2610e52347bdSJani Nikula memory_corruption_check=0/1 [X86] 2611e52347bdSJani Nikula Some BIOSes seem to corrupt the first 64k of 2612e52347bdSJani Nikula memory when doing things like suspend/resume. 2613e52347bdSJani Nikula Setting this option will scan the memory 2614e52347bdSJani Nikula looking for corruption. Enabling this will 2615e52347bdSJani Nikula both detect corruption and prevent the kernel 2616e52347bdSJani Nikula from using the memory being corrupted. 2617e52347bdSJani Nikula However, its intended as a diagnostic tool; if 2618e52347bdSJani Nikula repeatable BIOS-originated corruption always 2619e52347bdSJani Nikula affects the same memory, you can use memmap= 2620e52347bdSJani Nikula to prevent the kernel from using that memory. 2621e52347bdSJani Nikula 2622e52347bdSJani Nikula memory_corruption_check_size=size [X86] 2623e52347bdSJani Nikula By default it checks for corruption in the low 2624e52347bdSJani Nikula 64k, making this memory unavailable for normal 2625e52347bdSJani Nikula use. Use this parameter to scan for 2626e52347bdSJani Nikula corruption in more or less memory. 2627e52347bdSJani Nikula 2628e52347bdSJani Nikula memory_corruption_check_period=seconds [X86] 2629e52347bdSJani Nikula By default it checks for corruption every 60 2630e52347bdSJani Nikula seconds. Use this parameter to check at some 2631e52347bdSJani Nikula other rate. 0 disables periodic checking. 2632e52347bdSJani Nikula 2633d90fe2acSChristophe Leroy memtest= [KNL,X86,ARM,PPC] Enable memtest 2634e52347bdSJani Nikula Format: <integer> 2635e52347bdSJani Nikula default : 0 <disable> 2636e52347bdSJani Nikula Specifies the number of memtest passes to be 2637e52347bdSJani Nikula performed. Each pass selects another test 2638e52347bdSJani Nikula pattern from a given set of patterns. Memtest 2639e52347bdSJani Nikula fills the memory with this pattern, validates 2640e52347bdSJani Nikula memory contents and reserves bad memory 2641e52347bdSJani Nikula regions that are detected. 2642e52347bdSJani Nikula 2643c262f3b9STom Lendacky mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control 2644c262f3b9STom Lendacky Valid arguments: on, off 2645c262f3b9STom Lendacky Default (depends on kernel configuration option): 2646c262f3b9STom Lendacky on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y) 2647c262f3b9STom Lendacky off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n) 2648c262f3b9STom Lendacky mem_encrypt=on: Activate SME 2649c262f3b9STom Lendacky mem_encrypt=off: Do not activate SME 2650c262f3b9STom Lendacky 26512f5947dfSChristoph Hellwig Refer to Documentation/virt/kvm/amd-memory-encryption.rst 2652c262f3b9STom Lendacky for details on when memory encryption can be activated. 2653c262f3b9STom Lendacky 26547b9dc3f7SLinus Torvalds mem_sleep_default= [SUSPEND] Default system suspend mode: 26557b9dc3f7SLinus Torvalds s2idle - Suspend-To-Idle 26567b9dc3f7SLinus Torvalds shallow - Power-On Suspend or equivalent (if supported) 26577b9dc3f7SLinus Torvalds deep - Suspend-To-RAM or equivalent (if supported) 265858e7cb9eSRafael J. Wysocki See Documentation/admin-guide/pm/sleep-states.rst. 26597b9dc3f7SLinus Torvalds 2660e52347bdSJani Nikula meye.*= [HW] Set MotionEye Camera parameters 2661a405ed85STom Saeger See Documentation/media/v4l-drivers/meye.rst. 2662e52347bdSJani Nikula 2663e52347bdSJani Nikula mfgpt_irq= [IA-32] Specify the IRQ to use for the 2664e52347bdSJani Nikula Multi-Function General Purpose Timers on AMD Geode 2665e52347bdSJani Nikula platforms. 2666e52347bdSJani Nikula 2667e52347bdSJani Nikula mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 2668e52347bdSJani Nikula the BIOS has incorrectly applied a workaround. TinyBIOS 2669e52347bdSJani Nikula version 0.98 is known to be affected, 0.99 fixes the 2670e52347bdSJani Nikula problem by letting the user disable the workaround. 2671e52347bdSJani Nikula 2672e52347bdSJani Nikula mga= [HW,DRM] 2673e52347bdSJani Nikula 2674e52347bdSJani Nikula min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this 2675e52347bdSJani Nikula physical address is ignored. 2676e52347bdSJani Nikula 2677e52347bdSJani Nikula mini2440= [ARM,HW,KNL] 2678e52347bdSJani Nikula Format:[0..2][b][c][t] 2679e52347bdSJani Nikula Default: "0tb" 2680e52347bdSJani Nikula MINI2440 configuration specification: 2681e52347bdSJani Nikula 0 - The attached screen is the 3.5" TFT 2682e52347bdSJani Nikula 1 - The attached screen is the 7" TFT 2683e52347bdSJani Nikula 2 - The VGA Shield is attached (1024x768) 2684e52347bdSJani Nikula Leaving out the screen size parameter will not load 2685e52347bdSJani Nikula the TFT driver, and the framebuffer will be left 2686e52347bdSJani Nikula unconfigured. 2687e52347bdSJani Nikula b - Enable backlight. The TFT backlight pin will be 2688e52347bdSJani Nikula linked to the kernel VESA blanking code and a GPIO 2689e52347bdSJani Nikula LED. This parameter is not necessary when using the 2690e52347bdSJani Nikula VGA shield. 2691e52347bdSJani Nikula c - Enable the s3c camera interface. 2692e52347bdSJani Nikula t - Reserved for enabling touchscreen support. The 2693e52347bdSJani Nikula touchscreen support is not enabled in the mainstream 2694e52347bdSJani Nikula kernel as of 2.6.30, a preliminary port can be found 2695e52347bdSJani Nikula in the "bleeding edge" mini2440 support kernel at 2696e52347bdSJani Nikula http://repo.or.cz/w/linux-2.6/mini2440.git 2697e52347bdSJani Nikula 269898af8452SJosh Poimboeuf mitigations= 2699a111b7c0SJosh Poimboeuf [X86,PPC,S390,ARM64] Control optional mitigations for 2700a111b7c0SJosh Poimboeuf CPU vulnerabilities. This is a set of curated, 2701d68be4c4SJosh Poimboeuf arch-independent options, each of which is an 2702d68be4c4SJosh Poimboeuf aggregation of existing arch-specific options. 270398af8452SJosh Poimboeuf 270498af8452SJosh Poimboeuf off 270598af8452SJosh Poimboeuf Disable all optional CPU mitigations. This 270698af8452SJosh Poimboeuf improves system performance, but it may also 270798af8452SJosh Poimboeuf expose users to several CPU vulnerabilities. 2708782e69efSJosh Poimboeuf Equivalent to: nopti [X86,PPC] 2709a111b7c0SJosh Poimboeuf kpti=0 [ARM64] 2710a2059825SJosh Poimboeuf nospectre_v1 [X86,PPC] 27110336e04aSJosh Poimboeuf nobp=0 [S390] 2712a111b7c0SJosh Poimboeuf nospectre_v2 [X86,PPC,S390,ARM64] 2713d68be4c4SJosh Poimboeuf spectre_v2_user=off [X86] 2714782e69efSJosh Poimboeuf spec_store_bypass_disable=off [X86,PPC] 2715a111b7c0SJosh Poimboeuf ssbd=force-off [ARM64] 2716d68be4c4SJosh Poimboeuf l1tf=off [X86] 27175c14068fSJosh Poimboeuf mds=off [X86] 2718a7a248c5SPawan Gupta tsx_async_abort=off [X86] 2719b8e8c830SPaolo Bonzini kvm.nx_huge_pages=off [X86] 2720b8e8c830SPaolo Bonzini 2721b8e8c830SPaolo Bonzini Exceptions: 2722b8e8c830SPaolo Bonzini This does not have any effect on 2723b8e8c830SPaolo Bonzini kvm.nx_huge_pages when 2724b8e8c830SPaolo Bonzini kvm.nx_huge_pages=force. 272598af8452SJosh Poimboeuf 272698af8452SJosh Poimboeuf auto (default) 272798af8452SJosh Poimboeuf Mitigate all CPU vulnerabilities, but leave SMT 272898af8452SJosh Poimboeuf enabled, even if it's vulnerable. This is for 272998af8452SJosh Poimboeuf users who don't want to be surprised by SMT 273098af8452SJosh Poimboeuf getting disabled across kernel upgrades, or who 273198af8452SJosh Poimboeuf have other ways of avoiding SMT-based attacks. 2732d68be4c4SJosh Poimboeuf Equivalent to: (default behavior) 273398af8452SJosh Poimboeuf 273498af8452SJosh Poimboeuf auto,nosmt 273598af8452SJosh Poimboeuf Mitigate all CPU vulnerabilities, disabling SMT 273698af8452SJosh Poimboeuf if needed. This is for users who always want to 273798af8452SJosh Poimboeuf be fully mitigated, even if it means losing SMT. 2738d68be4c4SJosh Poimboeuf Equivalent to: l1tf=flush,nosmt [X86] 27395c14068fSJosh Poimboeuf mds=full,nosmt [X86] 2740a7a248c5SPawan Gupta tsx_async_abort=full,nosmt [X86] 274198af8452SJosh Poimboeuf 2742e52347bdSJani Nikula mminit_loglevel= 2743e52347bdSJani Nikula [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 2744e52347bdSJani Nikula parameter allows control of the logging verbosity for 2745e52347bdSJani Nikula the additional memory initialisation checks. A value 2746e52347bdSJani Nikula of 0 disables mminit logging and a level of 4 will 2747e52347bdSJani Nikula log everything. Information is printed at KERN_DEBUG 2748e52347bdSJani Nikula so loglevel=8 may also need to be specified. 2749e52347bdSJani Nikula 2750e52347bdSJani Nikula module.sig_enforce 2751e52347bdSJani Nikula [KNL] When CONFIG_MODULE_SIG is set, this means that 2752e52347bdSJani Nikula modules without (valid) signatures will fail to load. 2753e52347bdSJani Nikula Note that if CONFIG_MODULE_SIG_FORCE is set, that 2754e52347bdSJani Nikula is always true, so this option does nothing. 2755e52347bdSJani Nikula 2756e52347bdSJani Nikula module_blacklist= [KNL] Do not load a comma-separated list of 2757e52347bdSJani Nikula modules. Useful for debugging problem modules. 2758e52347bdSJani Nikula 2759e52347bdSJani Nikula mousedev.tap_time= 2760e52347bdSJani Nikula [MOUSE] Maximum time between finger touching and 2761e52347bdSJani Nikula leaving touchpad surface for touch to be considered 2762e52347bdSJani Nikula a tap and be reported as a left button click (for 2763e52347bdSJani Nikula touchpads working in absolute mode only). 2764e52347bdSJani Nikula Format: <msecs> 2765e52347bdSJani Nikula mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 2766e52347bdSJani Nikula reporting absolute coordinates, such as tablets 2767e52347bdSJani Nikula mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 2768e52347bdSJani Nikula reporting absolute coordinates, such as tablets 2769e52347bdSJani Nikula 2770a5c6d650SDavid Rientjes movablecore= [KNL,X86,IA-64,PPC] 2771a5c6d650SDavid Rientjes Format: nn[KMGTPE] | nn% 2772a5c6d650SDavid Rientjes This parameter is the complement to kernelcore=, it 2773a5c6d650SDavid Rientjes specifies the amount of memory used for migratable 2774a5c6d650SDavid Rientjes allocations. If both kernelcore and movablecore is 2775a5c6d650SDavid Rientjes specified, then kernelcore will be at *least* the 2776a5c6d650SDavid Rientjes specified value but may be more. If movablecore on its 2777a5c6d650SDavid Rientjes own is specified, the administrator must be careful 2778e52347bdSJani Nikula that the amount of memory usable for all allocations 2779e52347bdSJani Nikula is not too small. 2780e52347bdSJani Nikula 2781f70029bbSMichal Hocko movable_node [KNL] Boot-time switch to make hotplugable memory 2782f70029bbSMichal Hocko NUMA nodes to be movable. This means that the memory 2783f70029bbSMichal Hocko of such nodes will be usable only for movable 2784f70029bbSMichal Hocko allocations which rules out almost all kernel 2785f70029bbSMichal Hocko allocations. Use with caution! 2786e52347bdSJani Nikula 2787e52347bdSJani Nikula MTD_Partition= [MTD] 2788e52347bdSJani Nikula Format: <name>,<region-number>,<size>,<offset> 2789e52347bdSJani Nikula 2790e52347bdSJani Nikula MTD_Region= [MTD] Format: 2791e52347bdSJani Nikula <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 2792e52347bdSJani Nikula 2793e52347bdSJani Nikula mtdparts= [MTD] 2794fb251124SJonathan Neuschäfer See drivers/mtd/parsers/cmdlinepart.c 2795e52347bdSJani Nikula 2796e52347bdSJani Nikula multitce=off [PPC] This parameter disables the use of the pSeries 2797e52347bdSJani Nikula firmware feature for updating multiple TCE entries 2798e52347bdSJani Nikula at a time. 2799e52347bdSJani Nikula 2800e52347bdSJani Nikula onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration 2801e52347bdSJani Nikula 2802e52347bdSJani Nikula Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] 2803e52347bdSJani Nikula 2804e52347bdSJani Nikula boundary - index of last SLC block on Flex-OneNAND. 2805e52347bdSJani Nikula The remaining blocks are configured as MLC blocks. 2806e52347bdSJani Nikula lock - Configure if Flex-OneNAND boundary should be locked. 2807e52347bdSJani Nikula Once locked, the boundary cannot be changed. 2808e52347bdSJani Nikula 1 indicates lock status, 0 indicates unlock status. 2809e52347bdSJani Nikula 2810e52347bdSJani Nikula mtdset= [ARM] 2811e52347bdSJani Nikula ARM/S3C2412 JIVE boot control 2812e52347bdSJani Nikula 2813e52347bdSJani Nikula See arch/arm/mach-s3c2412/mach-jive.c 2814e52347bdSJani Nikula 2815e52347bdSJani Nikula mtouchusb.raw_coordinates= 2816e52347bdSJani Nikula [HW] Make the MicroTouch USB driver use raw coordinates 2817e52347bdSJani Nikula ('y', default) or cooked coordinates ('n') 2818e52347bdSJani Nikula 2819e52347bdSJani Nikula mtrr_chunk_size=nn[KMG] [X86] 2820e52347bdSJani Nikula used for mtrr cleanup. It is largest continuous chunk 2821e52347bdSJani Nikula that could hold holes aka. UC entries. 2822e52347bdSJani Nikula 2823e52347bdSJani Nikula mtrr_gran_size=nn[KMG] [X86] 2824e52347bdSJani Nikula Used for mtrr cleanup. It is granularity of mtrr block. 2825e52347bdSJani Nikula Default is 1. 2826e52347bdSJani Nikula Large value could prevent small alignment from 2827e52347bdSJani Nikula using up MTRRs. 2828e52347bdSJani Nikula 2829e52347bdSJani Nikula mtrr_spare_reg_nr=n [X86] 2830e52347bdSJani Nikula Format: <integer> 2831e52347bdSJani Nikula Range: 0,7 : spare reg number 2832e52347bdSJani Nikula Default : 1 2833e52347bdSJani Nikula Used for mtrr cleanup. It is spare mtrr entries number. 2834e52347bdSJani Nikula Set to 2 or more if your graphical card needs more. 2835e52347bdSJani Nikula 2836e52347bdSJani Nikula n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 2837e52347bdSJani Nikula 2838e52347bdSJani Nikula netdev= [NET] Network devices parameters 2839e52347bdSJani Nikula Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 2840e52347bdSJani Nikula Note that mem_start is often overloaded to mean 2841e52347bdSJani Nikula something different and driver-specific. 2842e52347bdSJani Nikula This usage is only documented in each driver source 2843e52347bdSJani Nikula file if at all. 2844e52347bdSJani Nikula 2845e52347bdSJani Nikula nf_conntrack.acct= 2846e52347bdSJani Nikula [NETFILTER] Enable connection tracking flow accounting 2847e52347bdSJani Nikula 0 to disable accounting 2848e52347bdSJani Nikula 1 to enable accounting 2849e52347bdSJani Nikula Default value is 0. 2850e52347bdSJani Nikula 2851e52347bdSJani Nikula nfsaddrs= [NFS] Deprecated. Use ip= instead. 2852e52347bdSJani Nikula See Documentation/filesystems/nfs/nfsroot.txt. 2853e52347bdSJani Nikula 2854e52347bdSJani Nikula nfsroot= [NFS] nfs root filesystem for disk-less boxes. 2855e52347bdSJani Nikula See Documentation/filesystems/nfs/nfsroot.txt. 2856e52347bdSJani Nikula 2857e52347bdSJani Nikula nfsrootdebug [NFS] enable nfsroot debugging messages. 2858e52347bdSJani Nikula See Documentation/filesystems/nfs/nfsroot.txt. 2859e52347bdSJani Nikula 2860e52347bdSJani Nikula nfs.callback_nr_threads= 2861e52347bdSJani Nikula [NFSv4] set the total number of threads that the 2862e52347bdSJani Nikula NFS client will assign to service NFSv4 callback 2863e52347bdSJani Nikula requests. 2864e52347bdSJani Nikula 2865e52347bdSJani Nikula nfs.callback_tcpport= 2866e52347bdSJani Nikula [NFS] set the TCP port on which the NFSv4 callback 2867e52347bdSJani Nikula channel should listen. 2868e52347bdSJani Nikula 2869e52347bdSJani Nikula nfs.cache_getent= 2870e52347bdSJani Nikula [NFS] sets the pathname to the program which is used 2871e52347bdSJani Nikula to update the NFS client cache entries. 2872e52347bdSJani Nikula 2873e52347bdSJani Nikula nfs.cache_getent_timeout= 2874e52347bdSJani Nikula [NFS] sets the timeout after which an attempt to 2875e52347bdSJani Nikula update a cache entry is deemed to have failed. 2876e52347bdSJani Nikula 2877e52347bdSJani Nikula nfs.idmap_cache_timeout= 2878e52347bdSJani Nikula [NFS] set the maximum lifetime for idmapper cache 2879e52347bdSJani Nikula entries. 2880e52347bdSJani Nikula 2881e52347bdSJani Nikula nfs.enable_ino64= 2882e52347bdSJani Nikula [NFS] enable 64-bit inode numbers. 2883e52347bdSJani Nikula If zero, the NFS client will fake up a 32-bit inode 2884e52347bdSJani Nikula number for the readdir() and stat() syscalls instead 2885e52347bdSJani Nikula of returning the full 64-bit number. 2886e52347bdSJani Nikula The default is to return 64-bit inode numbers. 2887e52347bdSJani Nikula 2888e52347bdSJani Nikula nfs.max_session_cb_slots= 2889e52347bdSJani Nikula [NFSv4.1] Sets the maximum number of session 2890e52347bdSJani Nikula slots the client will assign to the callback 2891e52347bdSJani Nikula channel. This determines the maximum number of 2892e52347bdSJani Nikula callbacks the client will process in parallel for 2893e52347bdSJani Nikula a particular server. 2894e52347bdSJani Nikula 2895e52347bdSJani Nikula nfs.max_session_slots= 2896e52347bdSJani Nikula [NFSv4.1] Sets the maximum number of session slots 2897e52347bdSJani Nikula the client will attempt to negotiate with the server. 2898e52347bdSJani Nikula This limits the number of simultaneous RPC requests 2899e52347bdSJani Nikula that the client can send to the NFSv4.1 server. 2900e52347bdSJani Nikula Note that there is little point in setting this 2901e52347bdSJani Nikula value higher than the max_tcp_slot_table_limit. 2902e52347bdSJani Nikula 2903e52347bdSJani Nikula nfs.nfs4_disable_idmapping= 2904e52347bdSJani Nikula [NFSv4] When set to the default of '1', this option 2905e52347bdSJani Nikula ensures that both the RPC level authentication 2906e52347bdSJani Nikula scheme and the NFS level operations agree to use 2907e52347bdSJani Nikula numeric uids/gids if the mount is using the 2908e52347bdSJani Nikula 'sec=sys' security flavour. In effect it is 2909e52347bdSJani Nikula disabling idmapping, which can make migration from 2910e52347bdSJani Nikula legacy NFSv2/v3 systems to NFSv4 easier. 2911e52347bdSJani Nikula Servers that do not support this mode of operation 2912e52347bdSJani Nikula will be autodetected by the client, and it will fall 2913e52347bdSJani Nikula back to using the idmapper. 2914e52347bdSJani Nikula To turn off this behaviour, set the value to '0'. 2915e52347bdSJani Nikula nfs.nfs4_unique_id= 2916e52347bdSJani Nikula [NFS4] Specify an additional fixed unique ident- 2917e52347bdSJani Nikula ification string that NFSv4 clients can insert into 2918e52347bdSJani Nikula their nfs_client_id4 string. This is typically a 2919e52347bdSJani Nikula UUID that is generated at system install time. 2920e52347bdSJani Nikula 2921e52347bdSJani Nikula nfs.send_implementation_id = 2922e52347bdSJani Nikula [NFSv4.1] Send client implementation identification 2923e52347bdSJani Nikula information in exchange_id requests. 2924e52347bdSJani Nikula If zero, no implementation identification information 2925e52347bdSJani Nikula will be sent. 2926e52347bdSJani Nikula The default is to send the implementation identification 2927e52347bdSJani Nikula information. 2928e52347bdSJani Nikula 2929e52347bdSJani Nikula nfs.recover_lost_locks = 2930e52347bdSJani Nikula [NFSv4] Attempt to recover locks that were lost due 2931e52347bdSJani Nikula to a lease timeout on the server. Please note that 2932e52347bdSJani Nikula doing this risks data corruption, since there are 2933e52347bdSJani Nikula no guarantees that the file will remain unchanged 2934e52347bdSJani Nikula after the locks are lost. 2935e52347bdSJani Nikula If you want to enable the kernel legacy behaviour of 2936e52347bdSJani Nikula attempting to recover these locks, then set this 2937e52347bdSJani Nikula parameter to '1'. 2938e52347bdSJani Nikula The default parameter value of '0' causes the kernel 2939e52347bdSJani Nikula not to attempt recovery of lost locks. 2940e52347bdSJani Nikula 2941e52347bdSJani Nikula nfs4.layoutstats_timer = 2942e52347bdSJani Nikula [NFSv4.2] Change the rate at which the kernel sends 2943e52347bdSJani Nikula layoutstats to the pNFS metadata server. 2944e52347bdSJani Nikula 2945e52347bdSJani Nikula Setting this to value to 0 causes the kernel to use 2946e52347bdSJani Nikula whatever value is the default set by the layout 2947e52347bdSJani Nikula driver. A non-zero value sets the minimum interval 2948e52347bdSJani Nikula in seconds between layoutstats transmissions. 2949e52347bdSJani Nikula 2950e52347bdSJani Nikula nfsd.nfs4_disable_idmapping= 2951e52347bdSJani Nikula [NFSv4] When set to the default of '1', the NFSv4 2952e52347bdSJani Nikula server will return only numeric uids and gids to 2953e52347bdSJani Nikula clients using auth_sys, and will accept numeric uids 2954e52347bdSJani Nikula and gids from such clients. This is intended to ease 2955e52347bdSJani Nikula migration from NFSv2/v3. 2956e52347bdSJani Nikula 2957c0c74acbSHans-Christian Noren Egtvedt nmi_debug= [KNL,SH] Specify one or more actions to take 2958e52347bdSJani Nikula when a NMI is triggered. 2959e52347bdSJani Nikula Format: [state][,regs][,debounce][,die] 2960e52347bdSJani Nikula 2961e52347bdSJani Nikula nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels 2962e52347bdSJani Nikula Format: [panic,][nopanic,][num] 2963e52347bdSJani Nikula Valid num: 0 or 1 2964e52347bdSJani Nikula 0 - turn hardlockup detector in nmi_watchdog off 2965e52347bdSJani Nikula 1 - turn hardlockup detector in nmi_watchdog on 2966e52347bdSJani Nikula When panic is specified, panic when an NMI watchdog 296793285c01SZhenzhong Duan timeout occurs (or 'nopanic' to not panic on an NMI 296893285c01SZhenzhong Duan watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) 296993285c01SZhenzhong Duan To disable both hard and soft lockup detectors, 2970e52347bdSJani Nikula please see 'nowatchdog'. 2971e52347bdSJani Nikula This is useful when you use a panic=... timeout and 2972e52347bdSJani Nikula need the box quickly up again. 2973e52347bdSJani Nikula 2974d22881dcSScott Wood These settings can be accessed at runtime via 2975d22881dcSScott Wood the nmi_watchdog and hardlockup_panic sysctls. 2976d22881dcSScott Wood 2977e52347bdSJani Nikula netpoll.carrier_timeout= 2978e52347bdSJani Nikula [NET] Specifies amount of time (in seconds) that 2979e52347bdSJani Nikula netpoll should wait for a carrier. By default netpoll 2980e52347bdSJani Nikula waits 4 seconds. 2981e52347bdSJani Nikula 2982e52347bdSJani Nikula no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 2983e52347bdSJani Nikula emulation library even if a 387 maths coprocessor 2984e52347bdSJani Nikula is present. 2985e52347bdSJani Nikula 2986372fddf7SKirill A. Shutemov no5lvl [X86-64] Disable 5-level paging mode. Forces 2987372fddf7SKirill A. Shutemov kernel to use 4-level paging instead. 2988372fddf7SKirill A. Shutemov 2989e52347bdSJani Nikula no_console_suspend 2990e52347bdSJani Nikula [HW] Never suspend the console 2991e52347bdSJani Nikula Disable suspending of consoles during suspend and 2992e52347bdSJani Nikula hibernate operations. Once disabled, debugging 2993e52347bdSJani Nikula messages can reach various consoles while the rest 2994e52347bdSJani Nikula of the system is being put to sleep (ie, while 2995e52347bdSJani Nikula debugging driver suspend/resume hooks). This may 2996e52347bdSJani Nikula not work reliably with all consoles, but is known 2997e52347bdSJani Nikula to work with serial and VGA consoles. 2998e52347bdSJani Nikula To facilitate more flexible debugging, we also add 2999e52347bdSJani Nikula console_suspend, a printk module parameter to control 3000e52347bdSJani Nikula it. Users could use console_suspend (usually 3001e52347bdSJani Nikula /sys/module/printk/parameters/console_suspend) to 3002e52347bdSJani Nikula turn on/off it dynamically. 3003e52347bdSJani Nikula 3004c6c40533SKairui Song novmcoredd [KNL,KDUMP] 3005c6c40533SKairui Song Disable device dump. Device dump allows drivers to 3006c6c40533SKairui Song append dump data to vmcore so you can collect driver 3007c6c40533SKairui Song specified debug info. Drivers can append the data 3008c6c40533SKairui Song without any limit and this data is stored in memory, 3009c6c40533SKairui Song so this may cause significant memory stress. Disabling 3010c6c40533SKairui Song device dump can help save memory but the driver debug 3011c6c40533SKairui Song data will be no longer available. This parameter 3012c6c40533SKairui Song is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP 3013c6c40533SKairui Song is set. 3014c6c40533SKairui Song 3015e52347bdSJani Nikula noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 3016e52347bdSJani Nikula caches in the slab allocator. Saves per-node memory, 3017e52347bdSJani Nikula but will impact performance. 3018e52347bdSJani Nikula 3019e52347bdSJani Nikula noalign [KNL,ARM] 3020e52347bdSJani Nikula 3021686140a1SVasily Gorbik noaltinstr [S390] Disables alternative instructions patching 3022686140a1SVasily Gorbik (CPU alternatives feature). 3023686140a1SVasily Gorbik 3024e52347bdSJani Nikula noapic [SMP,APIC] Tells the kernel to not make use of any 3025e52347bdSJani Nikula IOAPICs that may be present in the system. 3026e52347bdSJani Nikula 3027e52347bdSJani Nikula noautogroup Disable scheduler automatic task group creation. 3028e52347bdSJani Nikula 3029e52347bdSJani Nikula nobats [PPC] Do not use BATs for mapping kernel lowmem 3030e52347bdSJani Nikula on "Classic" PPC cores. 3031e52347bdSJani Nikula 3032e52347bdSJani Nikula nocache [ARM] 3033e52347bdSJani Nikula 3034e52347bdSJani Nikula noclflush [BUGS=X86] Don't use the CLFLUSH instruction 3035e52347bdSJani Nikula 3036e52347bdSJani Nikula nodelayacct [KNL] Disable per-task delay accounting 3037e52347bdSJani Nikula 3038e52347bdSJani Nikula nodsp [SH] Disable hardware DSP at boot time. 3039e52347bdSJani Nikula 3040e52347bdSJani Nikula noefi Disable EFI runtime services support. 3041e52347bdSJani Nikula 3042e52347bdSJani Nikula noexec [IA-64] 3043e52347bdSJani Nikula 3044e52347bdSJani Nikula noexec [X86] 3045e52347bdSJani Nikula On X86-32 available only on PAE configured kernels. 3046e52347bdSJani Nikula noexec=on: enable non-executable mappings (default) 3047e52347bdSJani Nikula noexec=off: disable non-executable mappings 3048e52347bdSJani Nikula 3049de78a9c4SChristophe Leroy nosmap [X86,PPC] 3050e52347bdSJani Nikula Disable SMAP (Supervisor Mode Access Prevention) 3051e52347bdSJani Nikula even if it is supported by processor. 3052e52347bdSJani Nikula 30530fb1c25aSChristophe Leroy nosmep [X86,PPC] 3054e52347bdSJani Nikula Disable SMEP (Supervisor Mode Execution Prevention) 3055e52347bdSJani Nikula even if it is supported by processor. 3056e52347bdSJani Nikula 3057e52347bdSJani Nikula noexec32 [X86-64] 3058e52347bdSJani Nikula This affects only 32-bit executables. 3059e52347bdSJani Nikula noexec32=on: enable non-executable mappings (default) 3060e52347bdSJani Nikula read doesn't imply executable mappings 3061e52347bdSJani Nikula noexec32=off: disable non-executable mappings 3062e52347bdSJani Nikula read implies executable mappings 3063e52347bdSJani Nikula 3064e52347bdSJani Nikula nofpu [MIPS,SH] Disable hardware FPU at boot time. 3065e52347bdSJani Nikula 3066e52347bdSJani Nikula nofxsr [BUGS=X86-32] Disables x86 floating point extended 3067e52347bdSJani Nikula register save and restore. The kernel will only save 3068e52347bdSJani Nikula legacy floating-point registers on task switch. 3069e52347bdSJani Nikula 3070d909f910SNicholas Piggin nohugeiomap [KNL,x86,PPC] Disable kernel huge I/O mappings. 3071e52347bdSJani Nikula 3072e52347bdSJani Nikula nosmt [KNL,S390] Disable symmetric multithreading (SMT). 3073e52347bdSJani Nikula Equivalent to smt=1. 3074e52347bdSJani Nikula 307505736e4aSThomas Gleixner [KNL,x86] Disable symmetric multithreading (SMT). 3076506a66f3SThomas Gleixner nosmt=force: Force disable SMT, cannot be undone 3077506a66f3SThomas Gleixner via the sysfs control file. 307805736e4aSThomas Gleixner 3079a2059825SJosh Poimboeuf nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1 3080a2059825SJosh Poimboeuf (bounds check bypass). With this option data leaks are 3081a2059825SJosh Poimboeuf possible in the system. 308226cb1f36SDiana Craciun 3083e5ce5e72SJeremy Linton nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for 3084e5ce5e72SJeremy Linton the Spectre variant 2 (indirect branch prediction) 3085e5ce5e72SJeremy Linton vulnerability. System may allow data leaks with this 3086e5ce5e72SJeremy Linton option. 3087da285121SDavid Woodhouse 308824f7fc83SKonrad Rzeszutek Wilk nospec_store_bypass_disable 308924f7fc83SKonrad Rzeszutek Wilk [HW] Disable all mitigations for the Speculative Store Bypass vulnerability 309024f7fc83SKonrad Rzeszutek Wilk 3091e52347bdSJani Nikula noxsave [BUGS=X86] Disables x86 extended register state save 3092e52347bdSJani Nikula and restore using xsave. The kernel will fallback to 3093e52347bdSJani Nikula enabling legacy floating-point and sse state. 3094e52347bdSJani Nikula 3095e52347bdSJani Nikula noxsaveopt [X86] Disables xsaveopt used in saving x86 extended 3096e52347bdSJani Nikula register states. The kernel will fall back to use 3097e52347bdSJani Nikula xsave to save the states. By using this parameter, 3098e52347bdSJani Nikula performance of saving the states is degraded because 3099e52347bdSJani Nikula xsave doesn't support modified optimization while 3100e52347bdSJani Nikula xsaveopt supports it on xsaveopt enabled systems. 3101e52347bdSJani Nikula 3102e52347bdSJani Nikula noxsaves [X86] Disables xsaves and xrstors used in saving and 3103e52347bdSJani Nikula restoring x86 extended register state in compacted 3104e52347bdSJani Nikula form of xsave area. The kernel will fall back to use 3105e52347bdSJani Nikula xsaveopt and xrstor to save and restore the states 3106e52347bdSJani Nikula in standard form of xsave area. By using this 3107e52347bdSJani Nikula parameter, xsave area per process might occupy more 3108e52347bdSJani Nikula memory on xsaves enabled systems. 3109e52347bdSJani Nikula 3110e52347bdSJani Nikula nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or 3111e52347bdSJani Nikula wfi(ARM) instruction doesn't work correctly and not to 3112e52347bdSJani Nikula use it. This is also useful when using JTAG debugger. 3113e52347bdSJani Nikula 3114e52347bdSJani Nikula no_file_caps Tells the kernel not to honor file capabilities. The 3115e52347bdSJani Nikula only way then for a file to be executed with privilege 3116e52347bdSJani Nikula is to be setuid root or executed by root. 3117e52347bdSJani Nikula 3118e52347bdSJani Nikula nohalt [IA-64] Tells the kernel not to use the power saving 3119e52347bdSJani Nikula function PAL_HALT_LIGHT when idle. This increases 3120e52347bdSJani Nikula power-consumption. On the positive side, it reduces 3121e52347bdSJani Nikula interrupt wake-up latency, which may improve performance 3122e52347bdSJani Nikula in certain environments such as networked servers or 3123e52347bdSJani Nikula real-time systems. 3124e52347bdSJani Nikula 3125e52347bdSJani Nikula nohibernate [HIBERNATION] Disable hibernation and resume. 3126e52347bdSJani Nikula 3127e52347bdSJani Nikula nohz= [KNL] Boottime enable/disable dynamic ticks 3128e52347bdSJani Nikula Valid arguments: on, off 3129e52347bdSJani Nikula Default: on 3130e52347bdSJani Nikula 3131d94d1053SFrederic Weisbecker nohz_full= [KNL,BOOT,SMP,ISOL] 3132e52347bdSJani Nikula The argument is a cpu list, as described above. 3133e52347bdSJani Nikula In kernels built with CONFIG_NO_HZ_FULL=y, set 3134e52347bdSJani Nikula the specified list of CPUs whose tick will be stopped 3135e52347bdSJani Nikula whenever possible. The boot CPU will be forced outside 3136f99bcb2cSPaul E. McKenney the range to maintain the timekeeping. Any CPUs 3137f99bcb2cSPaul E. McKenney in this list will have their RCU callbacks offloaded, 3138f99bcb2cSPaul E. McKenney just as if they had also been called out in the 3139f99bcb2cSPaul E. McKenney rcu_nocbs= boot parameter. 3140e52347bdSJani Nikula 3141e52347bdSJani Nikula noiotrap [SH] Disables trapped I/O port accesses. 3142e52347bdSJani Nikula 3143e52347bdSJani Nikula noirqdebug [X86-32] Disables the code which attempts to detect and 3144e52347bdSJani Nikula disable unhandled interrupt sources. 3145e52347bdSJani Nikula 3146e52347bdSJani Nikula no_timer_check [X86,APIC] Disables the code which tests for 3147e52347bdSJani Nikula broken timer IRQ sources. 3148e52347bdSJani Nikula 3149e52347bdSJani Nikula noisapnp [ISAPNP] Disables ISA PnP code. 3150e52347bdSJani Nikula 3151e52347bdSJani Nikula noinitrd [RAM] Tells the kernel not to load any configured 3152e52347bdSJani Nikula initial RAM disk. 3153e52347bdSJani Nikula 3154e52347bdSJani Nikula nointremap [X86-64, Intel-IOMMU] Do not enable interrupt 3155e52347bdSJani Nikula remapping. 3156e52347bdSJani Nikula [Deprecated - use intremap=off] 3157e52347bdSJani Nikula 3158e52347bdSJani Nikula nointroute [IA-64] 3159e52347bdSJani Nikula 3160e52347bdSJani Nikula noinvpcid [X86] Disable the INVPCID cpu feature. 3161e52347bdSJani Nikula 3162e52347bdSJani Nikula nojitter [IA-64] Disables jitter checking for ITC timers. 3163e52347bdSJani Nikula 3164e52347bdSJani Nikula no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver 3165e52347bdSJani Nikula 3166e52347bdSJani Nikula no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page 3167e52347bdSJani Nikula fault handling. 3168e52347bdSJani Nikula 3169e7aa8c2eSLinus Torvalds no-vmw-sched-clock 3170e7aa8c2eSLinus Torvalds [X86,PV_OPS] Disable paravirtualized VMware scheduler 3171e7aa8c2eSLinus Torvalds clock and use the default one. 3172e7aa8c2eSLinus Torvalds 3173e0685fa2SSteven Price no-steal-acc [X86,KVM,ARM64] Disable paravirtualized steal time 3174e0685fa2SSteven Price accounting. steal time is computed, but won't 3175e0685fa2SSteven Price influence scheduler behaviour 3176e52347bdSJani Nikula 3177e52347bdSJani Nikula nolapic [X86-32,APIC] Do not enable or use the local APIC. 3178e52347bdSJani Nikula 3179e52347bdSJani Nikula nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 3180e52347bdSJani Nikula 3181e52347bdSJani Nikula noltlbs [PPC] Do not use large page/tlb entries for kernel 3182e52347bdSJani Nikula lowmem mapping on PPC40x and PPC8xx 3183e52347bdSJani Nikula 3184e52347bdSJani Nikula nomca [IA-64] Disable machine check abort handling 3185e52347bdSJani Nikula 3186e52347bdSJani Nikula nomce [X86-32] Disable Machine Check Exception 3187e52347bdSJani Nikula 3188e52347bdSJani Nikula nomfgpt [X86-32] Disable Multi-Function General Purpose 3189e52347bdSJani Nikula Timer usage (for AMD Geode machines). 3190e52347bdSJani Nikula 3191e52347bdSJani Nikula nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to 3192e52347bdSJani Nikula shutdown the other cpus. Instead use the REBOOT_VECTOR 3193e52347bdSJani Nikula irq. 3194e52347bdSJani Nikula 3195e52347bdSJani Nikula nomodule Disable module load 3196e52347bdSJani Nikula 3197e52347bdSJani Nikula nopat [X86] Disable PAT (page attribute table extension of 3198e52347bdSJani Nikula pagetables) support. 3199e52347bdSJani Nikula 32000790c9aaSAndy Lutomirski nopcid [X86-64] Disable the PCID cpu feature. 32010790c9aaSAndy Lutomirski 3202e52347bdSJani Nikula norandmaps Don't use address space randomization. Equivalent to 3203e52347bdSJani Nikula echo 0 > /proc/sys/kernel/randomize_va_space 3204e52347bdSJani Nikula 3205e52347bdSJani Nikula noreplace-smp [X86-32,SMP] Don't replace SMP instructions 3206e52347bdSJani Nikula with UP alternatives 3207e52347bdSJani Nikula 3208e52347bdSJani Nikula nordrand [X86] Disable kernel use of the RDRAND and 3209e52347bdSJani Nikula RDSEED instructions even if they are supported 3210e52347bdSJani Nikula by the processor. RDRAND and RDSEED are still 3211e52347bdSJani Nikula available to user space applications. 3212e52347bdSJani Nikula 3213e52347bdSJani Nikula noresume [SWSUSP] Disables resume and restores original swap 3214e52347bdSJani Nikula space. 3215e52347bdSJani Nikula 3216e52347bdSJani Nikula no-scroll [VGA] Disables scrollback. 3217e52347bdSJani Nikula This is required for the Braillex ib80-piezo Braille 3218e52347bdSJani Nikula reader made by F.H. Papenmeier (Germany). 3219e52347bdSJani Nikula 3220e52347bdSJani Nikula nosbagart [IA-64] 3221e52347bdSJani Nikula 3222e52347bdSJani Nikula nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 3223e52347bdSJani Nikula 3224e52347bdSJani Nikula nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 3225e52347bdSJani Nikula and disable the IO APIC. legacy for "maxcpus=0". 3226e52347bdSJani Nikula 3227e52347bdSJani Nikula nosoftlockup [KNL] Disable the soft-lockup detector. 3228e52347bdSJani Nikula 3229e52347bdSJani Nikula nosync [HW,M68K] Disables sync negotiation for all devices. 3230e52347bdSJani Nikula 3231e52347bdSJani Nikula nowatchdog [KNL] Disable both lockup detectors, i.e. 3232e52347bdSJani Nikula soft-lockup and NMI watchdog (hard-lockup). 3233e52347bdSJani Nikula 3234e52347bdSJani Nikula nowb [ARM] 3235e52347bdSJani Nikula 3236e52347bdSJani Nikula nox2apic [X86-64,APIC] Do not enable x2APIC mode. 3237e52347bdSJani Nikula 3238e52347bdSJani Nikula cpu0_hotplug [X86] Turn on CPU0 hotplug feature when 3239e52347bdSJani Nikula CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. 3240e52347bdSJani Nikula Some features depend on CPU0. Known dependencies are: 3241e52347bdSJani Nikula 1. Resume from suspend/hibernate depends on CPU0. 3242e52347bdSJani Nikula Suspend/hibernate will fail if CPU0 is offline and you 3243e52347bdSJani Nikula need to online CPU0 before suspend/hibernate. 3244e52347bdSJani Nikula 2. PIC interrupts also depend on CPU0. CPU0 can't be 3245e52347bdSJani Nikula removed if a PIC interrupt is detected. 3246e52347bdSJani Nikula It's said poweroff/reboot may depend on CPU0 on some 3247e52347bdSJani Nikula machines although I haven't seen such issues so far 3248e52347bdSJani Nikula after CPU0 is offline on a few tested machines. 3249e52347bdSJani Nikula If the dependencies are under your control, you can 3250e52347bdSJani Nikula turn on cpu0_hotplug. 3251e52347bdSJani Nikula 325235b55ef2SNoam Camus nps_mtm_hs_ctr= [KNL,ARC] 325335b55ef2SNoam Camus This parameter sets the maximum duration, in 325435b55ef2SNoam Camus cycles, each HW thread of the CTOP can run 325535b55ef2SNoam Camus without interruptions, before HW switches it. 325635b55ef2SNoam Camus The actual maximum duration is 16 times this 325735b55ef2SNoam Camus parameter's value. 325835b55ef2SNoam Camus Format: integer between 1 and 255 325935b55ef2SNoam Camus Default: 255 326035b55ef2SNoam Camus 3261e52347bdSJani Nikula nptcg= [IA-64] Override max number of concurrent global TLB 3262e52347bdSJani Nikula purges which is reported from either PAL_VM_SUMMARY or 3263e52347bdSJani Nikula SAL PALO. 3264e52347bdSJani Nikula 3265e52347bdSJani Nikula nr_cpus= [SMP] Maximum number of processors that an SMP kernel 3266e52347bdSJani Nikula could support. nr_cpus=n : n >= 1 limits the kernel to 3267e52347bdSJani Nikula support 'n' processors. It could be larger than the 3268e52347bdSJani Nikula number of already plugged CPU during bootup, later in 3269e52347bdSJani Nikula runtime you can physically add extra cpu until it reaches 3270e52347bdSJani Nikula n. So during boot up some boot time memory for per-cpu 3271e52347bdSJani Nikula variables need be pre-allocated for later physical cpu 3272e52347bdSJani Nikula hot plugging. 3273e52347bdSJani Nikula 3274e52347bdSJani Nikula nr_uarts= [SERIAL] maximum number of UARTs to be registered. 3275e52347bdSJani Nikula 3276e52347bdSJani Nikula numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing. 3277e52347bdSJani Nikula Allowed values are enable and disable 3278e52347bdSJani Nikula 3279e52347bdSJani Nikula numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 3280c9bff3eeSMichal Hocko 'node', 'default' can be specified 3281e52347bdSJani Nikula This can be set from sysctl after boot. 328257043247SMauro Carvalho Chehab See Documentation/admin-guide/sysctl/vm.rst for details. 3283e52347bdSJani Nikula 3284a3e1d1a7SSaravana Kannan of_devlink [OF, KNL] Create device links between consumer and 3285a3e1d1a7SSaravana Kannan supplier devices by scanning the devictree to infer the 3286a3e1d1a7SSaravana Kannan consumer/supplier relationships. A consumer device 3287a3e1d1a7SSaravana Kannan will not be probed until all the supplier devices have 3288a3e1d1a7SSaravana Kannan probed successfully. 3289a3e1d1a7SSaravana Kannan 3290e52347bdSJani Nikula ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. 3291e52347bdSJani Nikula See Documentation/debugging-via-ohci1394.txt for more 3292e52347bdSJani Nikula info. 3293e52347bdSJani Nikula 3294e52347bdSJani Nikula olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 3295e52347bdSJani Nikula Rather than timing out after 20 ms if an EC 3296e52347bdSJani Nikula command is not properly ACKed, override the length 3297e52347bdSJani Nikula of the timeout. We have interrupts disabled while 3298e52347bdSJani Nikula waiting for the ACK, so if this is set too high 3299e52347bdSJani Nikula interrupts *may* be lost! 3300e52347bdSJani Nikula 3301e52347bdSJani Nikula omap_mux= [OMAP] Override bootloader pin multiplexing. 3302e52347bdSJani Nikula Format: <mux_mode0.mode_name=value>... 3303e52347bdSJani Nikula For example, to override I2C bus2: 3304e52347bdSJani Nikula omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 3305e52347bdSJani Nikula 3306e52347bdSJani Nikula oprofile.timer= [HW] 3307e52347bdSJani Nikula Use timer interrupt instead of performance counters 3308e52347bdSJani Nikula 3309e52347bdSJani Nikula oprofile.cpu_type= Force an oprofile cpu type 3310e52347bdSJani Nikula This might be useful if you have an older oprofile 3311e52347bdSJani Nikula userland or if you want common events. 3312e52347bdSJani Nikula Format: { arch_perfmon } 3313e52347bdSJani Nikula arch_perfmon: [X86] Force use of architectural 3314e52347bdSJani Nikula perfmon on Intel CPUs instead of the 3315e52347bdSJani Nikula CPU specific event set. 3316e52347bdSJani Nikula timer: [X86] Force use of architectural NMI 3317e52347bdSJani Nikula timer mode (see also oprofile.timer 3318e52347bdSJani Nikula for generic hr timer mode) 3319e52347bdSJani Nikula 3320e52347bdSJani Nikula oops=panic Always panic on oopses. Default is to just kill the 3321e52347bdSJani Nikula process, but there is a small probability of 3322e52347bdSJani Nikula deadlocking the machine. 3323e52347bdSJani Nikula This will also cause panics on machine check exceptions. 3324e52347bdSJani Nikula Useful together with panic=30 to trigger a reboot. 3325e52347bdSJani Nikula 3326e900a918SDan Williams page_alloc.shuffle= 3327e900a918SDan Williams [KNL] Boolean flag to control whether the page allocator 3328e900a918SDan Williams should randomize its free lists. The randomization may 3329e900a918SDan Williams be automatically enabled if the kernel detects it is 3330e900a918SDan Williams running on a platform with a direct-mapped memory-side 3331e900a918SDan Williams cache, and this parameter can be used to 3332e900a918SDan Williams override/disable that behavior. The state of the flag 3333e900a918SDan Williams can be read from sysfs at: 3334e900a918SDan Williams /sys/module/page_alloc/parameters/shuffle. 3335e900a918SDan Williams 3336e52347bdSJani Nikula page_owner= [KNL] Boot-time page_owner enabling option. 3337e52347bdSJani Nikula Storage of the information about who allocated 3338e52347bdSJani Nikula each page is disabled in default. With this switch, 3339e52347bdSJani Nikula we can turn it on. 3340e52347bdSJani Nikula on: enable the feature 3341e52347bdSJani Nikula 3342e52347bdSJani Nikula page_poison= [KNL] Boot-time parameter changing the state of 33438c9a134cSKees Cook poisoning on the buddy allocator, available with 33448c9a134cSKees Cook CONFIG_PAGE_POISONING=y. 33458c9a134cSKees Cook off: turn off poisoning (default) 3346e52347bdSJani Nikula on: turn on poisoning 3347e52347bdSJani Nikula 3348e52347bdSJani Nikula panic= [KNL] Kernel behaviour on panic: delay <timeout> 3349e52347bdSJani Nikula timeout > 0: seconds before rebooting 3350e52347bdSJani Nikula timeout = 0: wait forever 3351e52347bdSJani Nikula timeout < 0: reboot immediately 3352e52347bdSJani Nikula Format: <timeout> 3353e52347bdSJani Nikula 3354d999bd93SFeng Tang panic_print= Bitmask for printing system info when panic happens. 3355d999bd93SFeng Tang User can chose combination of the following bits: 3356d999bd93SFeng Tang bit 0: print all tasks info 3357d999bd93SFeng Tang bit 1: print system memory info 3358d999bd93SFeng Tang bit 2: print timer info 3359d999bd93SFeng Tang bit 3: print locks info if CONFIG_LOCKDEP is on 3360d999bd93SFeng Tang bit 4: print ftrace buffer 3361de6da1e8SFeng Tang bit 5: print all printk messages in buffer 3362d999bd93SFeng Tang 3363e52347bdSJani Nikula panic_on_warn panic() instead of WARN(). Useful to cause kdump 3364e52347bdSJani Nikula on a WARN(). 3365e52347bdSJani Nikula 3366e52347bdSJani Nikula crash_kexec_post_notifiers 3367e52347bdSJani Nikula Run kdump after running panic-notifiers and dumping 3368e52347bdSJani Nikula kmsg. This only for the users who doubt kdump always 3369e52347bdSJani Nikula succeeds in any situation. 3370e52347bdSJani Nikula Note that this also increases risks of kdump failure, 3371e52347bdSJani Nikula because some panic notifiers can make the crashed 3372e52347bdSJani Nikula kernel more unstable. 3373e52347bdSJani Nikula 3374e52347bdSJani Nikula parkbd.port= [HW] Parallel port number the keyboard adapter is 3375e52347bdSJani Nikula connected to, default is 0. 3376e52347bdSJani Nikula Format: <parport#> 3377e52347bdSJani Nikula parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 3378e52347bdSJani Nikula 0 for XT, 1 for AT (default is AT). 3379e52347bdSJani Nikula Format: <mode> 3380e52347bdSJani Nikula 3381e52347bdSJani Nikula parport= [HW,PPT] Specify parallel ports. 0 disables. 3382e52347bdSJani Nikula Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 3383e52347bdSJani Nikula Use 'auto' to force the driver to use any 3384e52347bdSJani Nikula IRQ/DMA settings detected (the default is to 3385e52347bdSJani Nikula ignore detected IRQ/DMA settings because of 3386e52347bdSJani Nikula possible conflicts). You can specify the base 3387e52347bdSJani Nikula address, IRQ, and DMA settings; IRQ and DMA 3388e52347bdSJani Nikula should be numbers, or 'auto' (for using detected 3389e52347bdSJani Nikula settings on that particular port), or 'nofifo' 3390e52347bdSJani Nikula (to avoid using a FIFO even if it is detected). 3391e52347bdSJani Nikula Parallel ports are assigned in the order they 3392e52347bdSJani Nikula are specified on the command line, starting 3393e52347bdSJani Nikula with parport0. 3394e52347bdSJani Nikula 3395e52347bdSJani Nikula parport_init_mode= [HW,PPT] 3396e52347bdSJani Nikula Configure VIA parallel port to operate in 3397e52347bdSJani Nikula a specific mode. This is necessary on Pegasos 3398e52347bdSJani Nikula computer where firmware has no options for setting 3399e52347bdSJani Nikula up parallel port mode and sets it to spp. 3400e52347bdSJani Nikula Currently this function knows 686a and 8231 chips. 3401e52347bdSJani Nikula Format: [spp|ps2|epp|ecp|ecpepp] 3402e52347bdSJani Nikula 3403e52347bdSJani Nikula pause_on_oops= 3404e52347bdSJani Nikula Halt all CPUs after the first oops has been printed for 3405e52347bdSJani Nikula the specified number of seconds. This is to be used if 3406e52347bdSJani Nikula your oopses keep scrolling off the screen. 3407e52347bdSJani Nikula 3408e52347bdSJani Nikula pcbit= [HW,ISDN] 3409e52347bdSJani Nikula 3410e52347bdSJani Nikula pcd. [PARIDE] 3411e52347bdSJani Nikula See header of drivers/block/paride/pcd.c. 3412e7751617SMauro Carvalho Chehab See also Documentation/admin-guide/blockdev/paride.rst. 3413e52347bdSJani Nikula 341407d8d7e5SLogan Gunthorpe pci=option[,option...] [PCI] various PCI subsystem options. 341507d8d7e5SLogan Gunthorpe 341607d8d7e5SLogan Gunthorpe Some options herein operate on a specific device 341707d8d7e5SLogan Gunthorpe or a set of devices (<pci_dev>). These are 341807d8d7e5SLogan Gunthorpe specified in one of the following formats: 341907d8d7e5SLogan Gunthorpe 342045db3370SLogan Gunthorpe [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]* 342107d8d7e5SLogan Gunthorpe pci:<vendor>:<device>[:<subvendor>:<subdevice>] 342207d8d7e5SLogan Gunthorpe 342307d8d7e5SLogan Gunthorpe Note: the first format specifies a PCI 342407d8d7e5SLogan Gunthorpe bus/device/function address which may change 342507d8d7e5SLogan Gunthorpe if new hardware is inserted, if motherboard 342607d8d7e5SLogan Gunthorpe firmware changes, or due to changes caused 342707d8d7e5SLogan Gunthorpe by other kernel parameters. If the 342807d8d7e5SLogan Gunthorpe domain is left unspecified, it is 342945db3370SLogan Gunthorpe taken to be zero. Optionally, a path 343045db3370SLogan Gunthorpe to a device through multiple device/function 343145db3370SLogan Gunthorpe addresses can be specified after the base 343245db3370SLogan Gunthorpe address (this is more robust against 343345db3370SLogan Gunthorpe renumbering issues). The second format 343407d8d7e5SLogan Gunthorpe selects devices using IDs from the 343507d8d7e5SLogan Gunthorpe configuration space which may match multiple 343607d8d7e5SLogan Gunthorpe devices in the system. 343707d8d7e5SLogan Gunthorpe 343811eb0e0eSSinan Kaya earlydump dump PCI config space before the kernel 3439e52347bdSJani Nikula changes anything 3440e52347bdSJani Nikula off [X86] don't probe for the PCI bus 3441e52347bdSJani Nikula bios [X86-32] force use of PCI BIOS, don't access 3442e52347bdSJani Nikula the hardware directly. Use this if your machine 3443e52347bdSJani Nikula has a non-standard PCI host bridge. 3444e52347bdSJani Nikula nobios [X86-32] disallow use of PCI BIOS, only direct 3445e52347bdSJani Nikula hardware access methods are allowed. Use this 3446e52347bdSJani Nikula if you experience crashes upon bootup and you 3447e52347bdSJani Nikula suspect they are caused by the BIOS. 3448e52347bdSJani Nikula conf1 [X86] Force use of PCI Configuration Access 3449e52347bdSJani Nikula Mechanism 1 (config address in IO port 0xCF8, 3450e52347bdSJani Nikula data in IO port 0xCFC, both 32-bit). 3451e52347bdSJani Nikula conf2 [X86] Force use of PCI Configuration Access 3452e52347bdSJani Nikula Mechanism 2 (IO port 0xCF8 is an 8-bit port for 3453e52347bdSJani Nikula the function, IO port 0xCFA, also 8-bit, sets 3454e52347bdSJani Nikula bus number. The config space is then accessed 3455e52347bdSJani Nikula through ports 0xC000-0xCFFF). 3456e52347bdSJani Nikula See http://wiki.osdev.org/PCI for more info 3457e52347bdSJani Nikula on the configuration access mechanisms. 3458e52347bdSJani Nikula noaer [PCIE] If the PCIEAER kernel config parameter is 3459e52347bdSJani Nikula enabled, this kernel boot option can be used to 3460e52347bdSJani Nikula disable the use of PCIE advanced error reporting. 3461e52347bdSJani Nikula nodomains [PCI] Disable support for multiple PCI 3462e52347bdSJani Nikula root domains (aka PCI segments, in ACPI-speak). 3463e52347bdSJani Nikula nommconf [X86] Disable use of MMCONFIG for PCI 3464e52347bdSJani Nikula Configuration 3465e52347bdSJani Nikula check_enable_amd_mmconf [X86] check for and enable 3466e52347bdSJani Nikula properly configured MMIO access to PCI 3467e52347bdSJani Nikula config space on AMD family 10h CPU 3468e52347bdSJani Nikula nomsi [MSI] If the PCI_MSI kernel config parameter is 3469e52347bdSJani Nikula enabled, this kernel boot option can be used to 3470e52347bdSJani Nikula disable the use of MSI interrupts system-wide. 3471e52347bdSJani Nikula noioapicquirk [APIC] Disable all boot interrupt quirks. 3472e52347bdSJani Nikula Safety option to keep boot IRQs enabled. This 3473e52347bdSJani Nikula should never be necessary. 3474e52347bdSJani Nikula ioapicreroute [APIC] Enable rerouting of boot IRQs to the 3475e52347bdSJani Nikula primary IO-APIC for bridges that cannot disable 3476e52347bdSJani Nikula boot IRQs. This fixes a source of spurious IRQs 3477e52347bdSJani Nikula when the system masks IRQs. 3478e52347bdSJani Nikula noioapicreroute [APIC] Disable workaround that uses the 3479e52347bdSJani Nikula boot IRQ equivalent of an IRQ that connects to 3480e52347bdSJani Nikula a chipset where boot IRQs cannot be disabled. 3481e52347bdSJani Nikula The opposite of ioapicreroute. 3482e52347bdSJani Nikula biosirq [X86-32] Use PCI BIOS calls to get the interrupt 3483e52347bdSJani Nikula routing table. These calls are known to be buggy 3484e52347bdSJani Nikula on several machines and they hang the machine 3485e52347bdSJani Nikula when used, but on other computers it's the only 3486e52347bdSJani Nikula way to get the interrupt routing table. Try 3487e52347bdSJani Nikula this option if the kernel is unable to allocate 3488e52347bdSJani Nikula IRQs or discover secondary PCI buses on your 3489e52347bdSJani Nikula motherboard. 3490e52347bdSJani Nikula rom [X86] Assign address space to expansion ROMs. 3491e52347bdSJani Nikula Use with caution as certain devices share 3492e52347bdSJani Nikula address decoders between ROMs and other 3493e52347bdSJani Nikula resources. 3494e52347bdSJani Nikula norom [X86] Do not assign address space to 3495e52347bdSJani Nikula expansion ROMs that do not already have 3496e52347bdSJani Nikula BIOS assigned address ranges. 3497e52347bdSJani Nikula nobar [X86] Do not assign address space to the 3498e52347bdSJani Nikula BARs that weren't assigned by the BIOS. 3499e52347bdSJani Nikula irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 3500e52347bdSJani Nikula assigned automatically to PCI devices. You can 3501e52347bdSJani Nikula make the kernel exclude IRQs of your ISA cards 3502e52347bdSJani Nikula this way. 3503e52347bdSJani Nikula pirqaddr=0xAAAAA [X86] Specify the physical address 3504e52347bdSJani Nikula of the PIRQ table (normally generated 3505e52347bdSJani Nikula by the BIOS) if it is outside the 3506e52347bdSJani Nikula F0000h-100000h range. 3507e52347bdSJani Nikula lastbus=N [X86] Scan all buses thru bus #N. Can be 3508e52347bdSJani Nikula useful if the kernel is unable to find your 3509e52347bdSJani Nikula secondary buses and you want to tell it 3510e52347bdSJani Nikula explicitly which ones they are. 3511e52347bdSJani Nikula assign-busses [X86] Always assign all PCI bus 3512e52347bdSJani Nikula numbers ourselves, overriding 3513e52347bdSJani Nikula whatever the firmware may have done. 3514e52347bdSJani Nikula usepirqmask [X86] Honor the possible IRQ mask stored 3515e52347bdSJani Nikula in the BIOS $PIR table. This is needed on 3516e52347bdSJani Nikula some systems with broken BIOSes, notably 3517e52347bdSJani Nikula some HP Pavilion N5400 and Omnibook XE3 3518e52347bdSJani Nikula notebooks. This will have no effect if ACPI 3519e52347bdSJani Nikula IRQ routing is enabled. 3520e52347bdSJani Nikula noacpi [X86] Do not use ACPI for IRQ routing 3521e52347bdSJani Nikula or for PCI scanning. 3522e52347bdSJani Nikula use_crs [X86] Use PCI host bridge window information 3523e52347bdSJani Nikula from ACPI. On BIOSes from 2008 or later, this 3524e52347bdSJani Nikula is enabled by default. If you need to use this, 3525e52347bdSJani Nikula please report a bug. 3526e52347bdSJani Nikula nocrs [X86] Ignore PCI host bridge windows from ACPI. 3527e52347bdSJani Nikula If you need to use this, please report a bug. 3528e52347bdSJani Nikula routeirq Do IRQ routing for all PCI devices. 3529e52347bdSJani Nikula This is normally done in pci_enable_device(), 3530e52347bdSJani Nikula so this option is a temporary workaround 3531e52347bdSJani Nikula for broken drivers that don't call it. 3532e52347bdSJani Nikula skip_isa_align [X86] do not align io start addr, so can 3533e52347bdSJani Nikula handle more pci cards 3534e52347bdSJani Nikula noearly [X86] Don't do any early type 1 scanning. 3535e52347bdSJani Nikula This might help on some broken boards which 3536e52347bdSJani Nikula machine check when some devices' config space 3537e52347bdSJani Nikula is read. But various workarounds are disabled 3538e52347bdSJani Nikula and some IOMMU drivers will not work. 3539e52347bdSJani Nikula bfsort Sort PCI devices into breadth-first order. 3540e52347bdSJani Nikula This sorting is done to get a device 3541e52347bdSJani Nikula order compatible with older (<= 2.4) kernels. 3542e52347bdSJani Nikula nobfsort Don't sort PCI devices into breadth-first order. 3543e52347bdSJani Nikula pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) 3544e52347bdSJani Nikula tuning and use the BIOS-configured MPS defaults. 3545e52347bdSJani Nikula pcie_bus_safe Set every device's MPS to the largest value 3546e52347bdSJani Nikula supported by all devices below the root complex. 3547e52347bdSJani Nikula pcie_bus_perf Set device MPS to the largest allowable MPS 3548e52347bdSJani Nikula based on its parent bus. Also set MRRS (Max 3549e52347bdSJani Nikula Read Request Size) to the largest supported 3550e52347bdSJani Nikula value (no larger than the MPS that the device 3551e52347bdSJani Nikula or bus can support) for best performance. 3552e52347bdSJani Nikula pcie_bus_peer2peer Set every device's MPS to 128B, which 3553e52347bdSJani Nikula every device is guaranteed to support. This 3554e52347bdSJani Nikula configuration allows peer-to-peer DMA between 3555e52347bdSJani Nikula any pair of devices, possibly at the cost of 3556e52347bdSJani Nikula reduced performance. This also guarantees 3557e52347bdSJani Nikula that hot-added devices will work. 3558e52347bdSJani Nikula cbiosize=nn[KMG] The fixed amount of bus space which is 3559e52347bdSJani Nikula reserved for the CardBus bridge's IO window. 3560e52347bdSJani Nikula The default value is 256 bytes. 3561e52347bdSJani Nikula cbmemsize=nn[KMG] The fixed amount of bus space which is 3562e52347bdSJani Nikula reserved for the CardBus bridge's memory 3563e52347bdSJani Nikula window. The default value is 64 megabytes. 3564e52347bdSJani Nikula resource_alignment= 3565e52347bdSJani Nikula Format: 356607d8d7e5SLogan Gunthorpe [<order of align>@]<pci_dev>[; ...] 3567e52347bdSJani Nikula Specifies alignment and device to reassign 356807d8d7e5SLogan Gunthorpe aligned memory resources. How to 356907d8d7e5SLogan Gunthorpe specify the device is described above. 3570e52347bdSJani Nikula If <order of align> is not specified, 3571e52347bdSJani Nikula PAGE_SIZE is used as alignment. 35723b1b1ce3SAlexey Kardashevskiy A PCI-PCI bridge can be specified if resource 3573e52347bdSJani Nikula windows need to be expanded. 3574e52347bdSJani Nikula To specify the alignment for several 3575e52347bdSJani Nikula instances of a device, the PCI vendor, 3576e52347bdSJani Nikula device, subvendor, and subdevice may be 35773b1b1ce3SAlexey Kardashevskiy specified, e.g., 12@pci:8086:9c22:103c:198f 35783b1b1ce3SAlexey Kardashevskiy for 4096-byte alignment. 3579e52347bdSJani Nikula ecrc= Enable/disable PCIe ECRC (transaction layer 3580e52347bdSJani Nikula end-to-end CRC checking). 3581e52347bdSJani Nikula bios: Use BIOS/firmware settings. This is the 3582e52347bdSJani Nikula the default. 3583e52347bdSJani Nikula off: Turn ECRC off 3584e52347bdSJani Nikula on: Turn ECRC on. 3585e52347bdSJani Nikula hpiosize=nn[KMG] The fixed amount of bus space which is 3586e52347bdSJani Nikula reserved for hotplug bridge's IO window. 3587e52347bdSJani Nikula Default size is 256 bytes. 3588d7b8a217SNicholas Johnson hpmmiosize=nn[KMG] The fixed amount of bus space which is 3589d7b8a217SNicholas Johnson reserved for hotplug bridge's MMIO window. 3590d7b8a217SNicholas Johnson Default size is 2 megabytes. 3591d7b8a217SNicholas Johnson hpmmioprefsize=nn[KMG] The fixed amount of bus space which is 3592d7b8a217SNicholas Johnson reserved for hotplug bridge's MMIO_PREF window. 3593d7b8a217SNicholas Johnson Default size is 2 megabytes. 3594e52347bdSJani Nikula hpmemsize=nn[KMG] The fixed amount of bus space which is 3595d7b8a217SNicholas Johnson reserved for hotplug bridge's MMIO and 3596d7b8a217SNicholas Johnson MMIO_PREF window. 3597e52347bdSJani Nikula Default size is 2 megabytes. 3598e52347bdSJani Nikula hpbussize=nn The minimum amount of additional bus numbers 3599e52347bdSJani Nikula reserved for buses below a hotplug bridge. 3600e52347bdSJani Nikula Default is 1. 3601e52347bdSJani Nikula realloc= Enable/disable reallocating PCI bridge resources 3602e52347bdSJani Nikula if allocations done by BIOS are too small to 3603e52347bdSJani Nikula accommodate resources required by all child 3604e52347bdSJani Nikula devices. 3605e52347bdSJani Nikula off: Turn realloc off 3606e52347bdSJani Nikula on: Turn realloc on 3607e52347bdSJani Nikula realloc same as realloc=on 3608e52347bdSJani Nikula noari do not use PCIe ARI. 3609cef74409SGil Kupfer noats [PCIE, Intel-IOMMU, AMD-IOMMU] 3610cef74409SGil Kupfer do not use PCIe ATS (and IOMMU device IOTLB). 3611e52347bdSJani Nikula pcie_scan_all Scan all possible PCIe devices. Otherwise we 3612e52347bdSJani Nikula only look for one device below a PCIe downstream 3613e52347bdSJani Nikula port. 3614f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= big_root_window Try to add a big 64bit memory window to the PCIe 3615f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= root complex on AMD CPUs. Some GFX hardware 3616f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= can resize a BAR to allow access to all VRAM. 3617f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= Adding the window is slightly risky (it may 3618f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= conflict with unreported devices), so this 3619f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= taints the kernel. 3620aaca43fdSLogan Gunthorpe disable_acs_redir=<pci_dev>[; ...] 3621aaca43fdSLogan Gunthorpe Specify one or more PCI devices (in the format 3622aaca43fdSLogan Gunthorpe specified above) separated by semicolons. 3623aaca43fdSLogan Gunthorpe Each device specified will have the PCI ACS 3624aaca43fdSLogan Gunthorpe redirect capabilities forced off which will 3625aaca43fdSLogan Gunthorpe allow P2P traffic between devices through 3626aaca43fdSLogan Gunthorpe bridges without forcing it upstream. Note: 3627aaca43fdSLogan Gunthorpe this removes isolation between devices and 3628aaca43fdSLogan Gunthorpe may put more devices in an IOMMU group. 3629fbfe07d4SSebastian Ott force_floating [S390] Force usage of floating interrupts. 363056271303SSebastian Ott nomio [S390] Do not use MIO instructions. 3631e52347bdSJani Nikula 3632e52347bdSJani Nikula pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 3633e52347bdSJani Nikula Management. 3634e52347bdSJani Nikula off Disable ASPM. 3635e52347bdSJani Nikula force Enable ASPM even on devices that claim not to support it. 3636e52347bdSJani Nikula WARNING: Forcing ASPM on may cause system lockups. 3637e52347bdSJani Nikula 36384c0fd764SBjorn Helgaas pcie_ports= [PCIE] PCIe port services handling: 36394c0fd764SBjorn Helgaas native Use native PCIe services (PME, AER, DPC, PCIe hotplug) 36404c0fd764SBjorn Helgaas even if the platform doesn't give the OS permission to 36414c0fd764SBjorn Helgaas use them. This may cause conflicts if the platform 36424c0fd764SBjorn Helgaas also tries to use these services. 364335a0b237SOlof Johansson dpc-native Use native PCIe service for DPC only. May 364435a0b237SOlof Johansson cause conflicts if firmware uses AER or DPC. 36454c0fd764SBjorn Helgaas compat Disable native PCIe services (PME, AER, DPC, PCIe 36464c0fd764SBjorn Helgaas hotplug). 3647e52347bdSJani Nikula 3648e52347bdSJani Nikula pcie_port_pm= [PCIE] PCIe port power management handling: 3649e52347bdSJani Nikula off Disable power management of all PCIe ports 3650e52347bdSJani Nikula force Forcibly enable power management of all PCIe ports 3651e52347bdSJani Nikula 3652e52347bdSJani Nikula pcie_pme= [PCIE,PM] Native PCIe PME signaling options: 3653e52347bdSJani Nikula nomsi Do not use MSI for native PCIe PME signaling (this makes 3654e52347bdSJani Nikula all PCIe root ports use INTx for all services). 3655e52347bdSJani Nikula 3656e52347bdSJani Nikula pcmv= [HW,PCMCIA] BadgePAD 4 3657e52347bdSJani Nikula 3658e52347bdSJani Nikula pd_ignore_unused 3659e52347bdSJani Nikula [PM] 3660e52347bdSJani Nikula Keep all power-domains already enabled by bootloader on, 3661e52347bdSJani Nikula even if no driver has claimed them. This is useful 3662e52347bdSJani Nikula for debug and development, but should not be 3663e52347bdSJani Nikula needed on a platform with proper driver support. 3664e52347bdSJani Nikula 3665e52347bdSJani Nikula pd. [PARIDE] 3666e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 3667e52347bdSJani Nikula 3668e52347bdSJani Nikula pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 3669e52347bdSJani Nikula boot time. 3670e52347bdSJani Nikula Format: { 0 | 1 } 3671e52347bdSJani Nikula See arch/parisc/kernel/pdc_chassis.c 3672e52347bdSJani Nikula 3673e52347bdSJani Nikula percpu_alloc= Select which percpu first chunk allocator to use. 3674e52347bdSJani Nikula Currently supported values are "embed" and "page". 3675e52347bdSJani Nikula Archs may support subset or none of the selections. 3676e52347bdSJani Nikula See comments in mm/percpu.c for details on each 3677e52347bdSJani Nikula allocator. This parameter is primarily for debugging 3678e52347bdSJani Nikula and performance comparison. 3679e52347bdSJani Nikula 3680e52347bdSJani Nikula pf. [PARIDE] 3681e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 3682e52347bdSJani Nikula 3683e52347bdSJani Nikula pg. [PARIDE] 3684e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 3685e52347bdSJani Nikula 3686e52347bdSJani Nikula pirq= [SMP,APIC] Manual mp-table setup 3687cb1aaebeSMauro Carvalho Chehab See Documentation/x86/i386/IO-APIC.rst. 3688e52347bdSJani Nikula 3689e52347bdSJani Nikula plip= [PPT,NET] Parallel port network link 3690e52347bdSJani Nikula Format: { parport<nr> | timid | 0 } 36913ba9b1b8STom Saeger See also Documentation/admin-guide/parport.rst. 3692e52347bdSJani Nikula 3693e52347bdSJani Nikula pmtmr= [X86] Manual setup of pmtmr I/O Port. 3694e52347bdSJani Nikula Override pmtimer IOPort with a hex value. 3695e52347bdSJani Nikula e.g. pmtmr=0x508 3696e52347bdSJani Nikula 3697e52347bdSJani Nikula pnp.debug=1 [PNP] 3698e52347bdSJani Nikula Enable PNP debug messages (depends on the 3699e52347bdSJani Nikula CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time 3700e52347bdSJani Nikula via /sys/module/pnp/parameters/debug. We always show 3701e52347bdSJani Nikula current resource usage; turning this on also shows 3702e52347bdSJani Nikula possible settings and some assignment information. 3703e52347bdSJani Nikula 3704e52347bdSJani Nikula pnpacpi= [ACPI] 3705e52347bdSJani Nikula { off } 3706e52347bdSJani Nikula 3707e52347bdSJani Nikula pnpbios= [ISAPNP] 3708e52347bdSJani Nikula { on | off | curr | res | no-curr | no-res } 3709e52347bdSJani Nikula 3710e52347bdSJani Nikula pnp_reserve_irq= 3711e52347bdSJani Nikula [ISAPNP] Exclude IRQs for the autoconfiguration 3712e52347bdSJani Nikula 3713e52347bdSJani Nikula pnp_reserve_dma= 3714e52347bdSJani Nikula [ISAPNP] Exclude DMAs for the autoconfiguration 3715e52347bdSJani Nikula 3716e52347bdSJani Nikula pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 3717e52347bdSJani Nikula Ranges are in pairs (I/O port base and size). 3718e52347bdSJani Nikula 3719e52347bdSJani Nikula pnp_reserve_mem= 3720e52347bdSJani Nikula [ISAPNP] Exclude memory regions for the 3721e52347bdSJani Nikula autoconfiguration. 3722e52347bdSJani Nikula Ranges are in pairs (memory base and size). 3723e52347bdSJani Nikula 3724e52347bdSJani Nikula ports= [IP_VS_FTP] IPVS ftp helper module 3725e52347bdSJani Nikula Default is 21. 3726e52347bdSJani Nikula Up to 8 (IP_VS_APP_MAX_PORTS) ports 3727e52347bdSJani Nikula may be specified. 3728e52347bdSJani Nikula Format: <port>,<port>.... 3729e52347bdSJani Nikula 3730c3cbd075SBalbir Singh powersave=off [PPC] This option disables power saving features. 3731c3cbd075SBalbir Singh It specifically disables cpuidle and sets the 3732c3cbd075SBalbir Singh platform machine description specific power_save 3733c3cbd075SBalbir Singh function to NULL. On Idle the CPU just reduces 3734c3cbd075SBalbir Singh execution priority. 3735c3cbd075SBalbir Singh 3736e52347bdSJani Nikula ppc_strict_facility_enable 3737e52347bdSJani Nikula [PPC] This option catches any kernel floating point, 3738e52347bdSJani Nikula Altivec, VSX and SPE outside of regions specifically 3739e52347bdSJani Nikula allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). 3740e52347bdSJani Nikula There is some performance impact when enabling this. 3741e52347bdSJani Nikula 374207fd1761SCyril Bur ppc_tm= [PPC] 374307fd1761SCyril Bur Format: {"off"} 374407fd1761SCyril Bur Disable Hardware Transactional Memory 374507fd1761SCyril Bur 3746e52347bdSJani Nikula print-fatal-signals= 3747e52347bdSJani Nikula [KNL] debug: print fatal signals 3748e52347bdSJani Nikula 3749e52347bdSJani Nikula If enabled, warn about various signal handling 3750e52347bdSJani Nikula related application anomalies: too many signals, 3751e52347bdSJani Nikula too many POSIX.1 timers, fatal signals causing a 3752e52347bdSJani Nikula coredump - etc. 3753e52347bdSJani Nikula 3754e52347bdSJani Nikula If you hit the warning due to signal overflow, 3755e52347bdSJani Nikula you might want to try "ulimit -i unlimited". 3756e52347bdSJani Nikula 3757e52347bdSJani Nikula default: off. 3758e52347bdSJani Nikula 3759e52347bdSJani Nikula printk.always_kmsg_dump= 3760e52347bdSJani Nikula Trigger kmsg_dump for cases other than kernel oops or 3761e52347bdSJani Nikula panics 3762e52347bdSJani Nikula Format: <bool> (1/Y/y=enable, 0/N/n=disable) 3763e52347bdSJani Nikula default: disabled 3764e52347bdSJani Nikula 3765e52347bdSJani Nikula printk.devkmsg={on,off,ratelimit} 3766e52347bdSJani Nikula Control writing to /dev/kmsg. 3767e52347bdSJani Nikula on - unlimited logging to /dev/kmsg from userspace 3768e52347bdSJani Nikula off - logging to /dev/kmsg disabled 3769e52347bdSJani Nikula ratelimit - ratelimit the logging 3770e52347bdSJani Nikula Default: ratelimit 3771e52347bdSJani Nikula 3772e52347bdSJani Nikula printk.time= Show timing data prefixed to each printk message line 3773e52347bdSJani Nikula Format: <bool> (1/Y/y=enable, 0/N/n=disable) 3774e52347bdSJani Nikula 3775e52347bdSJani Nikula processor.max_cstate= [HW,ACPI] 3776e52347bdSJani Nikula Limit processor to maximum C-state 3777e52347bdSJani Nikula max_cstate=9 overrides any DMI blacklist limit. 3778e52347bdSJani Nikula 3779e52347bdSJani Nikula processor.nocst [HW,ACPI] 3780e52347bdSJani Nikula Ignore the _CST method to determine C-states, 3781e52347bdSJani Nikula instead using the legacy FADT method 3782e52347bdSJani Nikula 3783e52347bdSJani Nikula profile= [KNL] Enable kernel profiling via /proc/profile 3784e7e61fc0SRandy Dunlap Format: [<profiletype>,]<number> 3785e7e61fc0SRandy Dunlap Param: <profiletype>: "schedule", "sleep", or "kvm" 3786e7e61fc0SRandy Dunlap [defaults to kernel profiling] 3787e52347bdSJani Nikula Param: "schedule" - profile schedule points. 3788e52347bdSJani Nikula Param: "sleep" - profile D-state sleeping (millisecs). 3789e52347bdSJani Nikula Requires CONFIG_SCHEDSTATS 3790e52347bdSJani Nikula Param: "kvm" - profile VM exits. 3791e7e61fc0SRandy Dunlap Param: <number> - step/bucket size as a power of 2 for 3792e7e61fc0SRandy Dunlap statistical time based profiling. 3793e52347bdSJani Nikula 3794e52347bdSJani Nikula prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 3795e52347bdSJani Nikula before loading. 3796e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/ramdisk.rst. 3797e52347bdSJani Nikula 3798e0c27447SJohannes Weiner psi= [KNL] Enable or disable pressure stall information 3799e0c27447SJohannes Weiner tracking. 3800e0c27447SJohannes Weiner Format: <bool> 3801e0c27447SJohannes Weiner 3802e52347bdSJani Nikula psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 3803e52347bdSJani Nikula probe for; one of (bare|imps|exps|lifebook|any). 3804e52347bdSJani Nikula psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 3805e52347bdSJani Nikula per second. 3806e52347bdSJani Nikula psmouse.resetafter= [HW,MOUSE] 3807e52347bdSJani Nikula Try to reset the device after so many bad packets 3808e52347bdSJani Nikula (0 = never). 3809e52347bdSJani Nikula psmouse.resolution= 3810e52347bdSJani Nikula [HW,MOUSE] Set desired mouse resolution, in dpi. 3811e52347bdSJani Nikula psmouse.smartscroll= 3812e52347bdSJani Nikula [HW,MOUSE] Controls Logitech smartscroll autorepeat. 3813e52347bdSJani Nikula 0 = disabled, 1 = enabled (default). 3814e52347bdSJani Nikula 3815e52347bdSJani Nikula pstore.backend= Specify the name of the pstore backend to use 3816e52347bdSJani Nikula 3817e52347bdSJani Nikula pt. [PARIDE] 3818e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/paride.rst. 3819e52347bdSJani Nikula 382001c9b17bSDave Hansen pti= [X86_64] Control Page Table Isolation of user and 382101c9b17bSDave Hansen kernel address spaces. Disabling this feature 382201c9b17bSDave Hansen removes hardening, but improves performance of 382301c9b17bSDave Hansen system calls and interrupts. 382401c9b17bSDave Hansen 382501c9b17bSDave Hansen on - unconditionally enable 382601c9b17bSDave Hansen off - unconditionally disable 382701c9b17bSDave Hansen auto - kernel detects whether your CPU model is 382801c9b17bSDave Hansen vulnerable to issues that PTI mitigates 382901c9b17bSDave Hansen 383001c9b17bSDave Hansen Not specifying this option is equivalent to pti=auto. 383101c9b17bSDave Hansen 383201c9b17bSDave Hansen nopti [X86_64] 383301c9b17bSDave Hansen Equivalent to pti=off 383441f4c20bSBorislav Petkov 3835e52347bdSJani Nikula pty.legacy_count= 3836e52347bdSJani Nikula [KNL] Number of legacy pty's. Overwrites compiled-in 3837e52347bdSJani Nikula default number. 3838e52347bdSJani Nikula 3839e52347bdSJani Nikula quiet [KNL] Disable most log messages 3840e52347bdSJani Nikula 3841e52347bdSJani Nikula r128= [HW,DRM] 3842e52347bdSJani Nikula 3843e52347bdSJani Nikula raid= [HW,RAID] 3844e52347bdSJani Nikula See Documentation/admin-guide/md.rst. 3845e52347bdSJani Nikula 3846e52347bdSJani Nikula ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 3847e7751617SMauro Carvalho Chehab See Documentation/admin-guide/blockdev/ramdisk.rst. 3848e52347bdSJani Nikula 38499b254366SKees Cook random.trust_cpu={on,off} 38509b254366SKees Cook [KNL] Enable or disable trusting the use of the 38519b254366SKees Cook CPU's random number generator (if available) to 38529b254366SKees Cook fully seed the kernel's CRNG. Default is controlled 38539b254366SKees Cook by CONFIG_RANDOM_TRUST_CPU. 38549b254366SKees Cook 3855011d8261SBorislav Petkov ras=option[,option,...] [KNL] RAS-specific options 3856011d8261SBorislav Petkov 3857011d8261SBorislav Petkov cec_disable [X86] 3858011d8261SBorislav Petkov Disable the Correctable Errors Collector, 3859011d8261SBorislav Petkov see CONFIG_RAS_CEC help text. 3860011d8261SBorislav Petkov 3861e52347bdSJani Nikula rcu_nocbs= [KNL] 3862da8739f2SPaul E. McKenney The argument is a cpu list, as described above, 3863da8739f2SPaul E. McKenney except that the string "all" can be used to 3864da8739f2SPaul E. McKenney specify every CPU on the system. 3865e52347bdSJani Nikula 3866e52347bdSJani Nikula In kernels built with CONFIG_RCU_NOCB_CPU=y, set 3867e52347bdSJani Nikula the specified list of CPUs to be no-callback CPUs. 386877095901SPaul E. McKenney Invocation of these CPUs' RCU callbacks will be 386977095901SPaul E. McKenney offloaded to "rcuox/N" kthreads created for that 387077095901SPaul E. McKenney purpose, where "x" is "p" for RCU-preempt, and 387177095901SPaul E. McKenney "s" for RCU-sched, and "N" is the CPU number. 387277095901SPaul E. McKenney This reduces OS jitter on the offloaded CPUs, 387377095901SPaul E. McKenney which can be useful for HPC and real-time 387477095901SPaul E. McKenney workloads. It can also improve energy efficiency 387577095901SPaul E. McKenney for asymmetric multiprocessors. 3876e52347bdSJani Nikula 3877e52347bdSJani Nikula rcu_nocb_poll [KNL] 3878e52347bdSJani Nikula Rather than requiring that offloaded CPUs 3879e52347bdSJani Nikula (specified by rcu_nocbs= above) explicitly 3880e52347bdSJani Nikula awaken the corresponding "rcuoN" kthreads, 3881e52347bdSJani Nikula make these kthreads poll for callbacks. 3882e52347bdSJani Nikula This improves the real-time response for the 3883e52347bdSJani Nikula offloaded CPUs by relieving them of the need to 3884e52347bdSJani Nikula wake up the corresponding kthread, but degrades 3885e52347bdSJani Nikula energy efficiency by requiring that the kthreads 3886e52347bdSJani Nikula periodically wake up to do the polling. 3887e52347bdSJani Nikula 3888e52347bdSJani Nikula rcutree.blimit= [KNL] 3889e52347bdSJani Nikula Set maximum number of finished RCU callbacks to 3890e52347bdSJani Nikula process in one batch. 3891e52347bdSJani Nikula 3892e52347bdSJani Nikula rcutree.dump_tree= [KNL] 3893e52347bdSJani Nikula Dump the structure of the rcu_node combining tree 3894e52347bdSJani Nikula out at early boot. This is used for diagnostic 3895e52347bdSJani Nikula purposes, to verify correct tree setup. 3896e52347bdSJani Nikula 3897e52347bdSJani Nikula rcutree.gp_cleanup_delay= [KNL] 3898e52347bdSJani Nikula Set the number of jiffies to delay each step of 389990040c9eSPaul E. McKenney RCU grace-period cleanup. 3900e52347bdSJani Nikula 3901e52347bdSJani Nikula rcutree.gp_init_delay= [KNL] 3902e52347bdSJani Nikula Set the number of jiffies to delay each step of 390390040c9eSPaul E. McKenney RCU grace-period initialization. 3904e52347bdSJani Nikula 3905e52347bdSJani Nikula rcutree.gp_preinit_delay= [KNL] 3906e52347bdSJani Nikula Set the number of jiffies to delay each step of 3907e52347bdSJani Nikula RCU grace-period pre-initialization, that is, 3908e52347bdSJani Nikula the propagation of recent CPU-hotplug changes up 390990040c9eSPaul E. McKenney the rcu_node combining tree. 3910e52347bdSJani Nikula 391148d07c04SSebastian Andrzej Siewior rcutree.use_softirq= [KNL] 391248d07c04SSebastian Andrzej Siewior If set to zero, move all RCU_SOFTIRQ processing to 391348d07c04SSebastian Andrzej Siewior per-CPU rcuc kthreads. Defaults to a non-zero 391448d07c04SSebastian Andrzej Siewior value, meaning that RCU_SOFTIRQ is used by default. 391548d07c04SSebastian Andrzej Siewior Specify rcutree.use_softirq=0 to use rcuc kthreads. 391648d07c04SSebastian Andrzej Siewior 3917e52347bdSJani Nikula rcutree.rcu_fanout_exact= [KNL] 3918e52347bdSJani Nikula Disable autobalancing of the rcu_node combining 3919e52347bdSJani Nikula tree. This is used by rcutorture, and might 3920e52347bdSJani Nikula possibly be useful for architectures having high 3921e52347bdSJani Nikula cache-to-cache transfer latencies. 3922e52347bdSJani Nikula 3923e52347bdSJani Nikula rcutree.rcu_fanout_leaf= [KNL] 3924e52347bdSJani Nikula Change the number of CPUs assigned to each 3925e52347bdSJani Nikula leaf rcu_node structure. Useful for very 3926e52347bdSJani Nikula large systems, which will choose the value 64, 3927e52347bdSJani Nikula and for NUMA systems with large remote-access 3928e52347bdSJani Nikula latencies, which will choose a value aligned 3929e52347bdSJani Nikula with the appropriate hardware boundaries. 3930e52347bdSJani Nikula 3931e52347bdSJani Nikula rcutree.jiffies_till_first_fqs= [KNL] 3932e52347bdSJani Nikula Set delay from grace-period initialization to 3933e52347bdSJani Nikula first attempt to force quiescent states. 3934e52347bdSJani Nikula Units are jiffies, minimum value is zero, 3935e52347bdSJani Nikula and maximum value is HZ. 3936e52347bdSJani Nikula 3937e52347bdSJani Nikula rcutree.jiffies_till_next_fqs= [KNL] 3938e52347bdSJani Nikula Set delay between subsequent attempts to force 3939e52347bdSJani Nikula quiescent states. Units are jiffies, minimum 3940e52347bdSJani Nikula value is one, and maximum value is HZ. 3941e52347bdSJani Nikula 39421a4762b9SPaul E. McKenney rcutree.jiffies_till_sched_qs= [KNL] 39431a4762b9SPaul E. McKenney Set required age in jiffies for a 39441a4762b9SPaul E. McKenney given grace period before RCU starts 39451a4762b9SPaul E. McKenney soliciting quiescent-state help from 39461a4762b9SPaul E. McKenney rcu_note_context_switch() and cond_resched(). 39471a4762b9SPaul E. McKenney If not specified, the kernel will calculate 39481a4762b9SPaul E. McKenney a value based on the most recent settings 39491a4762b9SPaul E. McKenney of rcutree.jiffies_till_first_fqs 39501a4762b9SPaul E. McKenney and rcutree.jiffies_till_next_fqs. 39511a4762b9SPaul E. McKenney This calculated value may be viewed in 39521a4762b9SPaul E. McKenney rcutree.jiffies_to_sched_qs. Any attempt to set 39531a4762b9SPaul E. McKenney rcutree.jiffies_to_sched_qs will be cheerfully 39541a4762b9SPaul E. McKenney overwritten. 39551a4762b9SPaul E. McKenney 3956e52347bdSJani Nikula rcutree.kthread_prio= [KNL,BOOT] 3957e52347bdSJani Nikula Set the SCHED_FIFO priority of the RCU per-CPU 3958e52347bdSJani Nikula kthreads (rcuc/N). This value is also used for 3959e52347bdSJani Nikula the priority of the RCU boost threads (rcub/N) 3960e52347bdSJani Nikula and for the RCU grace-period kthreads (rcu_bh, 3961e52347bdSJani Nikula rcu_preempt, and rcu_sched). If RCU_BOOST is 3962e52347bdSJani Nikula set, valid values are 1-99 and the default is 1 3963e52347bdSJani Nikula (the least-favored priority). Otherwise, when 3964e52347bdSJani Nikula RCU_BOOST is not set, valid values are 0-99 and 3965e52347bdSJani Nikula the default is zero (non-realtime operation). 3966e52347bdSJani Nikula 3967f7c612b0SPaul E. McKenney rcutree.rcu_nocb_gp_stride= [KNL] 3968f7c612b0SPaul E. McKenney Set the number of NOCB callback kthreads in 3969f7c612b0SPaul E. McKenney each group, which defaults to the square root 3970f7c612b0SPaul E. McKenney of the number of CPUs. Larger numbers reduce 3971f7c612b0SPaul E. McKenney the wakeup overhead on the global grace-period 3972f7c612b0SPaul E. McKenney kthread, but increases that same overhead on 3973f7c612b0SPaul E. McKenney each group's NOCB grace-period kthread. 3974e52347bdSJani Nikula 3975e52347bdSJani Nikula rcutree.qhimark= [KNL] 3976e52347bdSJani Nikula Set threshold of queued RCU callbacks beyond which 3977e52347bdSJani Nikula batch limiting is disabled. 3978e52347bdSJani Nikula 3979e52347bdSJani Nikula rcutree.qlowmark= [KNL] 3980e52347bdSJani Nikula Set threshold of queued RCU callbacks below which 3981e52347bdSJani Nikula batch limiting is re-enabled. 3982e52347bdSJani Nikula 3983e52347bdSJani Nikula rcutree.rcu_idle_gp_delay= [KNL] 3984e52347bdSJani Nikula Set wakeup interval for idle CPUs that have 3985e52347bdSJani Nikula RCU callbacks (RCU_FAST_NO_HZ=y). 3986e52347bdSJani Nikula 3987e52347bdSJani Nikula rcutree.rcu_idle_lazy_gp_delay= [KNL] 3988e52347bdSJani Nikula Set wakeup interval for idle CPUs that have 3989e52347bdSJani Nikula only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y). 3990e52347bdSJani Nikula Lazy RCU callbacks are those which RCU can 3991e52347bdSJani Nikula prove do nothing more than free memory. 3992e52347bdSJani Nikula 3993e3c50dfbSPaul E. McKenney rcutree.rcu_kick_kthreads= [KNL] 3994e3c50dfbSPaul E. McKenney Cause the grace-period kthread to get an extra 3995e3c50dfbSPaul E. McKenney wake_up() if it sleeps three times longer than 3996e3c50dfbSPaul E. McKenney it should at force-quiescent-state time. 3997e3c50dfbSPaul E. McKenney This wake_up() will be accompanied by a 3998e3c50dfbSPaul E. McKenney WARN_ONCE() splat and an ftrace_dump(). 3999e3c50dfbSPaul E. McKenney 40002ccaff10SPaul E. McKenney rcutree.sysrq_rcu= [KNL] 40012ccaff10SPaul E. McKenney Commandeer a sysrq key to dump out Tree RCU's 40022ccaff10SPaul E. McKenney rcu_node tree with an eye towards determining 40032ccaff10SPaul E. McKenney why a new grace period has not yet started. 40042ccaff10SPaul E. McKenney 4005881ed593SPaul E. McKenney rcuperf.gp_async= [KNL] 4006881ed593SPaul E. McKenney Measure performance of asynchronous 4007881ed593SPaul E. McKenney grace-period primitives such as call_rcu(). 4008881ed593SPaul E. McKenney 4009881ed593SPaul E. McKenney rcuperf.gp_async_max= [KNL] 4010881ed593SPaul E. McKenney Specify the maximum number of outstanding 4011881ed593SPaul E. McKenney callbacks per writer thread. When a writer 4012881ed593SPaul E. McKenney thread exceeds this limit, it invokes the 4013881ed593SPaul E. McKenney corresponding flavor of rcu_barrier() to allow 4014881ed593SPaul E. McKenney previously posted callbacks to drain. 4015881ed593SPaul E. McKenney 4016e52347bdSJani Nikula rcuperf.gp_exp= [KNL] 4017e52347bdSJani Nikula Measure performance of expedited synchronous 4018e52347bdSJani Nikula grace-period primitives. 4019e52347bdSJani Nikula 4020e52347bdSJani Nikula rcuperf.holdoff= [KNL] 4021e52347bdSJani Nikula Set test-start holdoff period. The purpose of 4022e52347bdSJani Nikula this parameter is to delay the start of the 4023e52347bdSJani Nikula test until boot completes in order to avoid 4024e52347bdSJani Nikula interference. 4025e52347bdSJani Nikula 4026e6e78b00SJoel Fernandes (Google) rcuperf.kfree_rcu_test= [KNL] 4027e6e78b00SJoel Fernandes (Google) Set to measure performance of kfree_rcu() flooding. 4028e6e78b00SJoel Fernandes (Google) 4029e6e78b00SJoel Fernandes (Google) rcuperf.kfree_nthreads= [KNL] 4030e6e78b00SJoel Fernandes (Google) The number of threads running loops of kfree_rcu(). 4031e6e78b00SJoel Fernandes (Google) 4032e6e78b00SJoel Fernandes (Google) rcuperf.kfree_alloc_num= [KNL] 4033e6e78b00SJoel Fernandes (Google) Number of allocations and frees done in an iteration. 4034e6e78b00SJoel Fernandes (Google) 4035e6e78b00SJoel Fernandes (Google) rcuperf.kfree_loops= [KNL] 4036e6e78b00SJoel Fernandes (Google) Number of loops doing rcuperf.kfree_alloc_num number 4037e6e78b00SJoel Fernandes (Google) of allocations and frees. 4038e6e78b00SJoel Fernandes (Google) 4039e52347bdSJani Nikula rcuperf.nreaders= [KNL] 4040e52347bdSJani Nikula Set number of RCU readers. The value -1 selects 4041e52347bdSJani Nikula N, where N is the number of CPUs. A value 4042e52347bdSJani Nikula "n" less than -1 selects N-n+1, where N is again 4043e52347bdSJani Nikula the number of CPUs. For example, -2 selects N 4044e52347bdSJani Nikula (the number of CPUs), -3 selects N+1, and so on. 4045e52347bdSJani Nikula A value of "n" less than or equal to -N selects 4046e52347bdSJani Nikula a single reader. 4047e52347bdSJani Nikula 4048e52347bdSJani Nikula rcuperf.nwriters= [KNL] 4049e52347bdSJani Nikula Set number of RCU writers. The values operate 4050e52347bdSJani Nikula the same as for rcuperf.nreaders. 4051e52347bdSJani Nikula N, where N is the number of CPUs 4052e52347bdSJani Nikula 4053820687a7SPaul E. McKenney rcuperf.perf_type= [KNL] 4054820687a7SPaul E. McKenney Specify the RCU implementation to test. 4055820687a7SPaul E. McKenney 4056e52347bdSJani Nikula rcuperf.shutdown= [KNL] 4057e52347bdSJani Nikula Shut the system down after performance tests 4058e52347bdSJani Nikula complete. This is useful for hands-off automated 4059e52347bdSJani Nikula testing. 4060e52347bdSJani Nikula 4061e52347bdSJani Nikula rcuperf.verbose= [KNL] 4062e52347bdSJani Nikula Enable additional printk() statements. 4063e52347bdSJani Nikula 4064820687a7SPaul E. McKenney rcuperf.writer_holdoff= [KNL] 4065820687a7SPaul E. McKenney Write-side holdoff between grace periods, 4066820687a7SPaul E. McKenney in microseconds. The default of zero says 4067820687a7SPaul E. McKenney no holdoff. 4068820687a7SPaul E. McKenney 4069e52347bdSJani Nikula rcutorture.fqs_duration= [KNL] 4070e52347bdSJani Nikula Set duration of force_quiescent_state bursts 4071e52347bdSJani Nikula in microseconds. 4072e52347bdSJani Nikula 4073e52347bdSJani Nikula rcutorture.fqs_holdoff= [KNL] 4074e52347bdSJani Nikula Set holdoff time within force_quiescent_state bursts 4075e52347bdSJani Nikula in microseconds. 4076e52347bdSJani Nikula 4077e52347bdSJani Nikula rcutorture.fqs_stutter= [KNL] 4078e52347bdSJani Nikula Set wait time between force_quiescent_state bursts 4079e52347bdSJani Nikula in seconds. 4080e52347bdSJani Nikula 4081ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress= [KNL] 4082ed8f6fb2SPaul E. McKenney Enable RCU grace-period forward-progress testing 4083ed8f6fb2SPaul E. McKenney for the types of RCU supporting this notion. 4084ed8f6fb2SPaul E. McKenney 4085ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_div= [KNL] 4086ed8f6fb2SPaul E. McKenney Specify the fraction of a CPU-stall-warning 4087ed8f6fb2SPaul E. McKenney period to do tight-loop forward-progress testing. 4088ed8f6fb2SPaul E. McKenney 4089ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_holdoff= [KNL] 4090ed8f6fb2SPaul E. McKenney Number of seconds to wait between successive 4091ed8f6fb2SPaul E. McKenney forward-progress tests. 4092ed8f6fb2SPaul E. McKenney 4093ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_need_resched= [KNL] 4094ed8f6fb2SPaul E. McKenney Enclose cond_resched() calls within checks for 4095ed8f6fb2SPaul E. McKenney need_resched() during tight-loop forward-progress 4096ed8f6fb2SPaul E. McKenney testing. 4097ed8f6fb2SPaul E. McKenney 4098e52347bdSJani Nikula rcutorture.gp_cond= [KNL] 4099e52347bdSJani Nikula Use conditional/asynchronous update-side 4100e52347bdSJani Nikula primitives, if available. 4101e52347bdSJani Nikula 4102e52347bdSJani Nikula rcutorture.gp_exp= [KNL] 4103e52347bdSJani Nikula Use expedited update-side primitives, if available. 4104e52347bdSJani Nikula 4105e52347bdSJani Nikula rcutorture.gp_normal= [KNL] 4106e52347bdSJani Nikula Use normal (non-expedited) asynchronous 4107e52347bdSJani Nikula update-side primitives, if available. 4108e52347bdSJani Nikula 4109e52347bdSJani Nikula rcutorture.gp_sync= [KNL] 4110e52347bdSJani Nikula Use normal (non-expedited) synchronous 4111e52347bdSJani Nikula update-side primitives, if available. If all 4112e52347bdSJani Nikula of rcutorture.gp_cond=, rcutorture.gp_exp=, 4113e52347bdSJani Nikula rcutorture.gp_normal=, and rcutorture.gp_sync= 4114e52347bdSJani Nikula are zero, rcutorture acts as if is interpreted 4115e52347bdSJani Nikula they are all non-zero. 4116e52347bdSJani Nikula 4117e52347bdSJani Nikula rcutorture.n_barrier_cbs= [KNL] 4118e52347bdSJani Nikula Set callbacks/threads for rcu_barrier() testing. 4119e52347bdSJani Nikula 4120e52347bdSJani Nikula rcutorture.nfakewriters= [KNL] 4121e52347bdSJani Nikula Set number of concurrent RCU writers. These just 4122e52347bdSJani Nikula stress RCU, they don't participate in the actual 4123e52347bdSJani Nikula test, hence the "fake". 4124e52347bdSJani Nikula 4125e52347bdSJani Nikula rcutorture.nreaders= [KNL] 4126e52347bdSJani Nikula Set number of RCU readers. The value -1 selects 4127e52347bdSJani Nikula N-1, where N is the number of CPUs. A value 4128e52347bdSJani Nikula "n" less than -1 selects N-n-2, where N is again 4129e52347bdSJani Nikula the number of CPUs. For example, -2 selects N 4130e52347bdSJani Nikula (the number of CPUs), -3 selects N+1, and so on. 4131e52347bdSJani Nikula 4132e52347bdSJani Nikula rcutorture.object_debug= [KNL] 4133e52347bdSJani Nikula Enable debug-object double-call_rcu() testing. 4134e52347bdSJani Nikula 4135e52347bdSJani Nikula rcutorture.onoff_holdoff= [KNL] 4136e52347bdSJani Nikula Set time (s) after boot for CPU-hotplug testing. 4137e52347bdSJani Nikula 4138e52347bdSJani Nikula rcutorture.onoff_interval= [KNL] 4139028be12bSPaul E. McKenney Set time (jiffies) between CPU-hotplug operations, 4140028be12bSPaul E. McKenney or zero to disable CPU-hotplug testing. 4141e52347bdSJani Nikula 4142e52347bdSJani Nikula rcutorture.shuffle_interval= [KNL] 4143e52347bdSJani Nikula Set task-shuffle interval (s). Shuffling tasks 4144e52347bdSJani Nikula allows some CPUs to go into dyntick-idle mode 4145e52347bdSJani Nikula during the rcutorture test. 4146e52347bdSJani Nikula 4147e52347bdSJani Nikula rcutorture.shutdown_secs= [KNL] 4148e52347bdSJani Nikula Set time (s) after boot system shutdown. This 4149e52347bdSJani Nikula is useful for hands-off automated testing. 4150e52347bdSJani Nikula 4151e52347bdSJani Nikula rcutorture.stall_cpu= [KNL] 4152e52347bdSJani Nikula Duration of CPU stall (s) to test RCU CPU stall 4153e52347bdSJani Nikula warnings, zero to disable. 4154e52347bdSJani Nikula 4155e52347bdSJani Nikula rcutorture.stall_cpu_holdoff= [KNL] 4156e52347bdSJani Nikula Time to wait (s) after boot before inducing stall. 4157e52347bdSJani Nikula 41582b1516e5SPaul E. McKenney rcutorture.stall_cpu_irqsoff= [KNL] 41592b1516e5SPaul E. McKenney Disable interrupts while stalling if set. 41602b1516e5SPaul E. McKenney 4161e52347bdSJani Nikula rcutorture.stat_interval= [KNL] 4162e52347bdSJani Nikula Time (s) between statistics printk()s. 4163e52347bdSJani Nikula 4164e52347bdSJani Nikula rcutorture.stutter= [KNL] 4165e52347bdSJani Nikula Time (s) to stutter testing, for example, specifying 4166e52347bdSJani Nikula five seconds causes the test to run for five seconds, 4167e52347bdSJani Nikula wait for five seconds, and so on. This tests RCU's 4168e52347bdSJani Nikula ability to transition abruptly to and from idle. 4169e52347bdSJani Nikula 4170e52347bdSJani Nikula rcutorture.test_boost= [KNL] 4171e52347bdSJani Nikula Test RCU priority boosting? 0=no, 1=maybe, 2=yes. 4172e52347bdSJani Nikula "Maybe" means test if the RCU implementation 4173e52347bdSJani Nikula under test support RCU priority boosting. 4174e52347bdSJani Nikula 4175e52347bdSJani Nikula rcutorture.test_boost_duration= [KNL] 4176e52347bdSJani Nikula Duration (s) of each individual boost test. 4177e52347bdSJani Nikula 4178e52347bdSJani Nikula rcutorture.test_boost_interval= [KNL] 4179e52347bdSJani Nikula Interval (s) between each boost test. 4180e52347bdSJani Nikula 4181e52347bdSJani Nikula rcutorture.test_no_idle_hz= [KNL] 4182e52347bdSJani Nikula Test RCU's dyntick-idle handling. See also the 4183e52347bdSJani Nikula rcutorture.shuffle_interval parameter. 4184e52347bdSJani Nikula 4185e52347bdSJani Nikula rcutorture.torture_type= [KNL] 4186e52347bdSJani Nikula Specify the RCU implementation to test. 4187e52347bdSJani Nikula 4188e52347bdSJani Nikula rcutorture.verbose= [KNL] 4189e52347bdSJani Nikula Enable additional printk() statements. 4190e52347bdSJani Nikula 4191cdc694b2SPaul E. McKenney rcupdate.rcu_cpu_stall_ftrace_dump= [KNL] 4192cdc694b2SPaul E. McKenney Dump ftrace buffer after reporting RCU CPU 4193cdc694b2SPaul E. McKenney stall warning. 4194cdc694b2SPaul E. McKenney 4195e52347bdSJani Nikula rcupdate.rcu_cpu_stall_suppress= [KNL] 4196e52347bdSJani Nikula Suppress RCU CPU stall warning messages. 4197e52347bdSJani Nikula 4198e52347bdSJani Nikula rcupdate.rcu_cpu_stall_timeout= [KNL] 4199e52347bdSJani Nikula Set timeout for RCU CPU stall warning messages. 4200e52347bdSJani Nikula 4201e52347bdSJani Nikula rcupdate.rcu_expedited= [KNL] 4202e52347bdSJani Nikula Use expedited grace-period primitives, for 4203e52347bdSJani Nikula example, synchronize_rcu_expedited() instead 4204e52347bdSJani Nikula of synchronize_rcu(). This reduces latency, 4205e52347bdSJani Nikula but can increase CPU utilization, degrade 4206e52347bdSJani Nikula real-time latency, and degrade energy efficiency. 4207e52347bdSJani Nikula No effect on CONFIG_TINY_RCU kernels. 4208e52347bdSJani Nikula 4209e52347bdSJani Nikula rcupdate.rcu_normal= [KNL] 4210e52347bdSJani Nikula Use only normal grace-period primitives, 4211e52347bdSJani Nikula for example, synchronize_rcu() instead of 4212e52347bdSJani Nikula synchronize_rcu_expedited(). This improves 4213e52347bdSJani Nikula real-time latency, CPU utilization, and 4214e52347bdSJani Nikula energy efficiency, but can expose users to 4215e52347bdSJani Nikula increased grace-period latency. This parameter 4216e52347bdSJani Nikula overrides rcupdate.rcu_expedited. No effect on 4217e52347bdSJani Nikula CONFIG_TINY_RCU kernels. 4218e52347bdSJani Nikula 4219e52347bdSJani Nikula rcupdate.rcu_normal_after_boot= [KNL] 4220e52347bdSJani Nikula Once boot has completed (that is, after 4221e52347bdSJani Nikula rcu_end_inkernel_boot() has been invoked), use 4222e52347bdSJani Nikula only normal grace-period primitives. No effect 4223e52347bdSJani Nikula on CONFIG_TINY_RCU kernels. 4224e52347bdSJani Nikula 4225e52347bdSJani Nikula rcupdate.rcu_task_stall_timeout= [KNL] 4226e52347bdSJani Nikula Set timeout in jiffies for RCU task stall warning 4227e52347bdSJani Nikula messages. Disable with a value less than or equal 4228e52347bdSJani Nikula to zero. 4229e52347bdSJani Nikula 4230e52347bdSJani Nikula rcupdate.rcu_self_test= [KNL] 4231e52347bdSJani Nikula Run the RCU early boot self tests 4232e52347bdSJani Nikula 4233e52347bdSJani Nikula rdinit= [KNL] 4234e52347bdSJani Nikula Format: <full_path> 4235e52347bdSJani Nikula Run specified binary instead of /init from the ramdisk, 4236e52347bdSJani Nikula used for early userspace startup. See initrd. 4237e52347bdSJani Nikula 4238c49a0a80STom Lendacky rdrand= [X86] 4239c49a0a80STom Lendacky force - Override the decision by the kernel to hide the 4240c49a0a80STom Lendacky advertisement of RDRAND support (this affects 4241c49a0a80STom Lendacky certain AMD processors because of buggy BIOS 4242c49a0a80STom Lendacky support, specifically around the suspend/resume 4243c49a0a80STom Lendacky path). 4244c49a0a80STom Lendacky 42451d9807fcSTony Luck rdt= [HW,X86,RDT] 42461d9807fcSTony Luck Turn on/off individual RDT features. List is: 424731516de3SFenghua Yu cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp, 424831516de3SFenghua Yu mba. 42491d9807fcSTony Luck E.g. to turn on cmt and turn off mba use: 42501d9807fcSTony Luck rdt=cmt,!mba 42511d9807fcSTony Luck 4252e52347bdSJani Nikula reboot= [KNL] 4253e52347bdSJani Nikula Format (x86 or x86_64): 4254e52347bdSJani Nikula [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \ 4255e52347bdSJani Nikula [[,]s[mp]#### \ 4256e52347bdSJani Nikula [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ 4257e52347bdSJani Nikula [[,]f[orce] 4258b287a25aSAaro Koskinen Where reboot_mode is one of warm (soft) or cold (hard) or gpio 4259b287a25aSAaro Koskinen (prefix with 'panic_' to set mode for panic 4260b287a25aSAaro Koskinen reboot only), 4261e52347bdSJani Nikula reboot_type is one of bios, acpi, kbd, triple, efi, or pci, 4262e52347bdSJani Nikula reboot_force is either force or not specified, 4263e52347bdSJani Nikula reboot_cpu is s[mp]#### with #### being the processor 4264e52347bdSJani Nikula to be used for rebooting. 4265e52347bdSJani Nikula 4266e52347bdSJani Nikula relax_domain_level= 4267e52347bdSJani Nikula [KNL, SMP] Set scheduler's default relax_domain_level. 4268da82c92fSMauro Carvalho Chehab See Documentation/admin-guide/cgroup-v1/cpusets.rst. 4269e52347bdSJani Nikula 4270ffd2e8dfSBjorn Helgaas reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory 4271ffd2e8dfSBjorn Helgaas Format: <base1>,<size1>[,<base2>,<size2>,...] 4272ffd2e8dfSBjorn Helgaas Reserve I/O ports or memory so the kernel won't use 4273ffd2e8dfSBjorn Helgaas them. If <base> is less than 0x10000, the region 4274ffd2e8dfSBjorn Helgaas is assumed to be I/O ports; otherwise it is memory. 4275e52347bdSJani Nikula 4276e52347bdSJani Nikula reservetop= [X86-32] 4277e52347bdSJani Nikula Format: nn[KMG] 4278e52347bdSJani Nikula Reserves a hole at the top of the kernel virtual 4279e52347bdSJani Nikula address space. 4280e52347bdSJani Nikula 4281e52347bdSJani Nikula reservelow= [X86] 4282e52347bdSJani Nikula Format: nn[K] 4283e52347bdSJani Nikula Set the amount of memory to reserve for BIOS at 4284e52347bdSJani Nikula the bottom of the address space. 4285e52347bdSJani Nikula 4286e52347bdSJani Nikula reset_devices [KNL] Force drivers to reset the underlying device 4287e52347bdSJani Nikula during initialization. 4288e52347bdSJani Nikula 4289e52347bdSJani Nikula resume= [SWSUSP] 4290e52347bdSJani Nikula Specify the partition device for software suspend 4291e52347bdSJani Nikula Format: 4292e52347bdSJani Nikula {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>} 4293e52347bdSJani Nikula 4294e52347bdSJani Nikula resume_offset= [SWSUSP] 4295e52347bdSJani Nikula Specify the offset from the beginning of the partition 4296e52347bdSJani Nikula given by "resume=" at which the swap header is located, 4297e52347bdSJani Nikula in <PAGE_SIZE> units (needed only for swap files). 4298151f4e2bSMauro Carvalho Chehab See Documentation/power/swsusp-and-swap-files.rst 4299e52347bdSJani Nikula 4300e52347bdSJani Nikula resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to 4301e52347bdSJani Nikula read the resume files 4302e52347bdSJani Nikula 4303e52347bdSJani Nikula resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up. 4304e52347bdSJani Nikula Useful for devices that are detected asynchronously 4305e52347bdSJani Nikula (e.g. USB and MMC devices). 4306e52347bdSJani Nikula 4307e52347bdSJani Nikula hibernate= [HIBERNATION] 4308e52347bdSJani Nikula noresume Don't check if there's a hibernation image 4309e52347bdSJani Nikula present during boot. 4310e52347bdSJani Nikula nocompress Don't compress/decompress hibernation images. 4311e52347bdSJani Nikula no Disable hibernation and resume. 4312e52347bdSJani Nikula protect_image Turn on image protection during restoration 4313e52347bdSJani Nikula (that will set all pages holding image data 4314e52347bdSJani Nikula during restoration read-only). 4315e52347bdSJani Nikula 4316e52347bdSJani Nikula retain_initrd [RAM] Keep initrd memory after extraction 4317e52347bdSJani Nikula 4318e52347bdSJani Nikula rfkill.default_state= 4319e52347bdSJani Nikula 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, 4320e52347bdSJani Nikula etc. communication is blocked by default. 4321e52347bdSJani Nikula 1 Unblocked. 4322e52347bdSJani Nikula 4323e52347bdSJani Nikula rfkill.master_switch_mode= 4324e52347bdSJani Nikula 0 The "airplane mode" button does nothing. 4325e52347bdSJani Nikula 1 The "airplane mode" button toggles between everything 4326e52347bdSJani Nikula blocked and the previous configuration. 4327e52347bdSJani Nikula 2 The "airplane mode" button toggles between everything 4328e52347bdSJani Nikula blocked and everything unblocked. 4329e52347bdSJani Nikula 4330e52347bdSJani Nikula rhash_entries= [KNL,NET] 4331e52347bdSJani Nikula Set number of hash buckets for route cache 4332e52347bdSJani Nikula 4333e16fd002SGrzegorz Andrejczuk ring3mwait=disable 4334e16fd002SGrzegorz Andrejczuk [KNL] Disable ring 3 MONITOR/MWAIT feature on supported 4335e16fd002SGrzegorz Andrejczuk CPUs. 4336e16fd002SGrzegorz Andrejczuk 4337e52347bdSJani Nikula ro [KNL] Mount root device read-only on boot 4338e52347bdSJani Nikula 4339e52347bdSJani Nikula rodata= [KNL] 4340e52347bdSJani Nikula on Mark read-only kernel memory as read-only (default). 4341e52347bdSJani Nikula off Leave read-only kernel memory writable for debugging. 4342e52347bdSJani Nikula 4343e52347bdSJani Nikula rockchip.usb_uart 4344e52347bdSJani Nikula Enable the uart passthrough on the designated usb port 4345e52347bdSJani Nikula on Rockchip SoCs. When active, the signals of the 4346e52347bdSJani Nikula debug-uart get routed to the D+ and D- pins of the usb 4347e52347bdSJani Nikula port and the regular usb controller gets disabled. 4348e52347bdSJani Nikula 4349e52347bdSJani Nikula root= [KNL] Root filesystem 4350e52347bdSJani Nikula See name_to_dev_t comment in init/do_mounts.c. 4351e52347bdSJani Nikula 4352e52347bdSJani Nikula rootdelay= [KNL] Delay (in seconds) to pause before attempting to 4353e52347bdSJani Nikula mount the root filesystem 4354e52347bdSJani Nikula 4355e52347bdSJani Nikula rootflags= [KNL] Set root filesystem mount option string 4356e52347bdSJani Nikula 4357e52347bdSJani Nikula rootfstype= [KNL] Set root filesystem type 4358e52347bdSJani Nikula 4359e52347bdSJani Nikula rootwait [KNL] Wait (indefinitely) for root device to show up. 4360e52347bdSJani Nikula Useful for devices that are detected asynchronously 4361e52347bdSJani Nikula (e.g. USB and MMC devices). 4362e52347bdSJani Nikula 4363e52347bdSJani Nikula rproc_mem=nn[KMG][@address] 4364e52347bdSJani Nikula [KNL,ARM,CMA] Remoteproc physical memory block. 4365e52347bdSJani Nikula Memory area to be used by remote processor image, 4366e52347bdSJani Nikula managed by CMA. 4367e52347bdSJani Nikula 4368e52347bdSJani Nikula rw [KNL] Mount root device read-write on boot 4369e52347bdSJani Nikula 4370e52347bdSJani Nikula S [KNL] Run init in single mode 4371e52347bdSJani Nikula 4372e52347bdSJani Nikula s390_iommu= [HW,S390] 4373e52347bdSJani Nikula Set s390 IOTLB flushing mode 4374e52347bdSJani Nikula strict 4375e52347bdSJani Nikula With strict flushing every unmap operation will result in 4376e52347bdSJani Nikula an IOTLB flush. Default is lazy flushing before reuse, 4377e52347bdSJani Nikula which is faster. 4378e52347bdSJani Nikula 4379e52347bdSJani Nikula sa1100ir [NET] 4380e52347bdSJani Nikula See drivers/net/irda/sa1100_ir.c. 4381e52347bdSJani Nikula 4382e52347bdSJani Nikula sbni= [NET] Granch SBNI12 leased line adapter 4383e52347bdSJani Nikula 4384e52347bdSJani Nikula sched_debug [KNL] Enables verbose scheduler debug messages. 4385e52347bdSJani Nikula 4386e52347bdSJani Nikula schedstats= [KNL,X86] Enable or disable scheduled statistics. 4387e52347bdSJani Nikula Allowed values are enable and disable. This feature 4388e52347bdSJani Nikula incurs a small amount of overhead in the scheduler 4389e52347bdSJani Nikula but is useful for debugging and performance tuning. 4390e52347bdSJani Nikula 4391e52347bdSJani Nikula skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate 4392e52347bdSJani Nikula xtime_lock contention on larger systems, and/or RCU lock 4393e52347bdSJani Nikula contention on all systems with CONFIG_MAXSMP set. 4394e52347bdSJani Nikula Format: { "0" | "1" } 4395e52347bdSJani Nikula 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1" 4396e52347bdSJani Nikula 1 -- enable. 4397e52347bdSJani Nikula Note: increases power consumption, thus should only be 4398e52347bdSJani Nikula enabled if running jitter sensitive (HPC/RT) workloads. 4399e52347bdSJani Nikula 440089a9684eSKees Cook security= [SECURITY] Choose a legacy "major" security module to 440189a9684eSKees Cook enable at boot. This has been deprecated by the 440289a9684eSKees Cook "lsm=" parameter. 4403e52347bdSJani Nikula 4404e52347bdSJani Nikula selinux= [SELINUX] Disable or enable SELinux at boot time. 4405e52347bdSJani Nikula Format: { "0" | "1" } 4406e52347bdSJani Nikula See security/selinux/Kconfig help text. 4407e52347bdSJani Nikula 0 -- disable. 4408e52347bdSJani Nikula 1 -- enable. 4409d41415ebSStephen Smalley Default value is 1. 4410e52347bdSJani Nikula 4411e52347bdSJani Nikula apparmor= [APPARMOR] Disable or enable AppArmor at boot time 4412e52347bdSJani Nikula Format: { "0" | "1" } 4413e52347bdSJani Nikula See security/apparmor/Kconfig help text 4414e52347bdSJani Nikula 0 -- disable. 4415e52347bdSJani Nikula 1 -- enable. 4416e52347bdSJani Nikula Default value is set via kernel config option. 4417e52347bdSJani Nikula 4418e52347bdSJani Nikula serialnumber [BUGS=X86-32] 4419e52347bdSJani Nikula 4420e52347bdSJani Nikula shapers= [NET] 4421e52347bdSJani Nikula Maximal number of shapers. 4422e52347bdSJani Nikula 4423e52347bdSJani Nikula simeth= [IA-64] 4424e52347bdSJani Nikula simscsi= 4425e52347bdSJani Nikula 4426e52347bdSJani Nikula slram= [HW,MTD] 4427e52347bdSJani Nikula 4428e52347bdSJani Nikula slab_nomerge [MM] 4429e52347bdSJani Nikula Disable merging of slabs with similar size. May be 4430e52347bdSJani Nikula necessary if there is some reason to distinguish 44317660a6fdSKees Cook allocs to different slabs, especially in hardened 44327660a6fdSKees Cook environments where the risk of heap overflows and 44337660a6fdSKees Cook layout control by attackers can usually be 44347660a6fdSKees Cook frustrated by disabling merging. This will reduce 44357660a6fdSKees Cook most of the exposure of a heap attack to a single 44367660a6fdSKees Cook cache (risks via metadata attacks are mostly 44377660a6fdSKees Cook unchanged). Debug options disable merging on their 44387660a6fdSKees Cook own. 4439ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 4440e52347bdSJani Nikula 4441e52347bdSJani Nikula slab_max_order= [MM, SLAB] 4442e52347bdSJani Nikula Determines the maximum allowed order for slabs. 4443e52347bdSJani Nikula A high setting may cause OOMs due to memory 4444e52347bdSJani Nikula fragmentation. Defaults to 1 for systems with 4445e52347bdSJani Nikula more than 32MB of RAM, 0 otherwise. 4446e52347bdSJani Nikula 4447e52347bdSJani Nikula slub_debug[=options[,slabs]] [MM, SLUB] 4448e52347bdSJani Nikula Enabling slub_debug allows one to determine the 4449e52347bdSJani Nikula culprit if slab objects become corrupted. Enabling 4450e52347bdSJani Nikula slub_debug can create guard zones around objects and 4451e52347bdSJani Nikula may poison objects when not in use. Also tracks the 4452e52347bdSJani Nikula last alloc / free. For more information see 4453ad56b738SMike Rapoport Documentation/vm/slub.rst. 4454e52347bdSJani Nikula 44551663f26dSTejun Heo slub_memcg_sysfs= [MM, SLUB] 44561663f26dSTejun Heo Determines whether to enable sysfs directories for 44571663f26dSTejun Heo memory cgroup sub-caches. 1 to enable, 0 to disable. 44581663f26dSTejun Heo The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON. 44591663f26dSTejun Heo Enabling this can lead to a very high number of debug 44601663f26dSTejun Heo directories and files being created under 44611663f26dSTejun Heo /sys/kernel/slub. 44621663f26dSTejun Heo 4463e52347bdSJani Nikula slub_max_order= [MM, SLUB] 4464e52347bdSJani Nikula Determines the maximum allowed order for slabs. 4465e52347bdSJani Nikula A high setting may cause OOMs due to memory 4466e52347bdSJani Nikula fragmentation. For more information see 4467ad56b738SMike Rapoport Documentation/vm/slub.rst. 4468e52347bdSJani Nikula 4469e52347bdSJani Nikula slub_min_objects= [MM, SLUB] 4470e52347bdSJani Nikula The minimum number of objects per slab. SLUB will 4471e52347bdSJani Nikula increase the slab order up to slub_max_order to 4472e52347bdSJani Nikula generate a sufficiently large slab able to contain 4473e52347bdSJani Nikula the number of objects indicated. The higher the number 4474e52347bdSJani Nikula of objects the smaller the overhead of tracking slabs 4475e52347bdSJani Nikula and the less frequently locks need to be acquired. 4476ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 4477e52347bdSJani Nikula 4478e52347bdSJani Nikula slub_min_order= [MM, SLUB] 4479e52347bdSJani Nikula Determines the minimum page order for slabs. Must be 4480e52347bdSJani Nikula lower than slub_max_order. 4481ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 4482e52347bdSJani Nikula 4483e52347bdSJani Nikula slub_nomerge [MM, SLUB] 4484e52347bdSJani Nikula Same with slab_nomerge. This is supported for legacy. 4485e52347bdSJani Nikula See slab_nomerge for more information. 4486e52347bdSJani Nikula 4487e52347bdSJani Nikula smart2= [HW] 4488e52347bdSJani Nikula Format: <io1>[,<io2>[,...,<io8>]] 4489e52347bdSJani Nikula 4490e52347bdSJani Nikula smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 4491e52347bdSJani Nikula smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 4492e52347bdSJani Nikula smsc-ircc2.ircc_sir= [HW] SIR base I/O port 4493e52347bdSJani Nikula smsc-ircc2.ircc_fir= [HW] FIR base I/O port 4494e52347bdSJani Nikula smsc-ircc2.ircc_irq= [HW] IRQ line 4495e52347bdSJani Nikula smsc-ircc2.ircc_dma= [HW] DMA channel 4496e52347bdSJani Nikula smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 4497e52347bdSJani Nikula 0: Toshiba Satellite 1800 (GP data pin select) 4498e52347bdSJani Nikula 1: Fast pin select (default) 4499e52347bdSJani Nikula 2: ATC IRMode 4500e52347bdSJani Nikula 4501e52347bdSJani Nikula smt [KNL,S390] Set the maximum number of threads (logical 4502e52347bdSJani Nikula CPUs) to use per physical CPU on systems capable of 4503e52347bdSJani Nikula symmetric multithreading (SMT). Will be capped to the 4504e52347bdSJani Nikula actual hardware limit. 4505e52347bdSJani Nikula Format: <integer> 4506e52347bdSJani Nikula Default: -1 (no limit) 4507e52347bdSJani Nikula 4508e52347bdSJani Nikula softlockup_panic= 4509e52347bdSJani Nikula [KNL] Should the soft-lockup detector generate panics. 4510e52347bdSJani Nikula Format: <integer> 4511e52347bdSJani Nikula 45123ce62385SBorislav Petkov A nonzero value instructs the soft-lockup detector 45133ce62385SBorislav Petkov to panic the machine when a soft-lockup occurs. This 45143ce62385SBorislav Petkov is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC 45153ce62385SBorislav Petkov which is the respective build-time switch to that 45163ce62385SBorislav Petkov functionality. 45173ce62385SBorislav Petkov 4518e52347bdSJani Nikula softlockup_all_cpu_backtrace= 4519e52347bdSJani Nikula [KNL] Should the soft-lockup detector generate 4520e52347bdSJani Nikula backtraces on all cpus. 4521e52347bdSJani Nikula Format: <integer> 4522e52347bdSJani Nikula 4523e52347bdSJani Nikula sonypi.*= [HW] Sony Programmable I/O Control Device driver 45249e1cbedeSMauro Carvalho Chehab See Documentation/admin-guide/laptops/sonypi.rst 4525e52347bdSJani Nikula 4526da285121SDavid Woodhouse spectre_v2= [X86] Control mitigation of Spectre variant 2 4527da285121SDavid Woodhouse (indirect branch speculation) vulnerability. 4528fa1202efSThomas Gleixner The default operation protects the kernel from 4529fa1202efSThomas Gleixner user space attacks. 4530da285121SDavid Woodhouse 4531fa1202efSThomas Gleixner on - unconditionally enable, implies 4532fa1202efSThomas Gleixner spectre_v2_user=on 4533fa1202efSThomas Gleixner off - unconditionally disable, implies 4534fa1202efSThomas Gleixner spectre_v2_user=off 4535da285121SDavid Woodhouse auto - kernel detects whether your CPU model is 4536da285121SDavid Woodhouse vulnerable 4537da285121SDavid Woodhouse 4538da285121SDavid Woodhouse Selecting 'on' will, and 'auto' may, choose a 4539da285121SDavid Woodhouse mitigation method at run time according to the 4540da285121SDavid Woodhouse CPU, the available microcode, the setting of the 4541da285121SDavid Woodhouse CONFIG_RETPOLINE configuration option, and the 4542da285121SDavid Woodhouse compiler with which the kernel was built. 4543da285121SDavid Woodhouse 4544fa1202efSThomas Gleixner Selecting 'on' will also enable the mitigation 4545fa1202efSThomas Gleixner against user space to user space task attacks. 4546fa1202efSThomas Gleixner 4547fa1202efSThomas Gleixner Selecting 'off' will disable both the kernel and 4548fa1202efSThomas Gleixner the user space protections. 4549fa1202efSThomas Gleixner 4550da285121SDavid Woodhouse Specific mitigations can also be selected manually: 4551da285121SDavid Woodhouse 4552da285121SDavid Woodhouse retpoline - replace indirect branches 4553da285121SDavid Woodhouse retpoline,generic - google's original retpoline 4554da285121SDavid Woodhouse retpoline,amd - AMD-specific minimal thunk 4555da285121SDavid Woodhouse 4556da285121SDavid Woodhouse Not specifying this option is equivalent to 4557da285121SDavid Woodhouse spectre_v2=auto. 4558da285121SDavid Woodhouse 4559fa1202efSThomas Gleixner spectre_v2_user= 4560fa1202efSThomas Gleixner [X86] Control mitigation of Spectre variant 2 4561fa1202efSThomas Gleixner (indirect branch speculation) vulnerability between 4562fa1202efSThomas Gleixner user space tasks 4563fa1202efSThomas Gleixner 4564fa1202efSThomas Gleixner on - Unconditionally enable mitigations. Is 4565fa1202efSThomas Gleixner enforced by spectre_v2=on 4566fa1202efSThomas Gleixner 4567fa1202efSThomas Gleixner off - Unconditionally disable mitigations. Is 4568fa1202efSThomas Gleixner enforced by spectre_v2=off 4569fa1202efSThomas Gleixner 45707cc765a6SThomas Gleixner prctl - Indirect branch speculation is enabled, 45717cc765a6SThomas Gleixner but mitigation can be enabled via prctl 45727cc765a6SThomas Gleixner per thread. The mitigation control state 45737cc765a6SThomas Gleixner is inherited on fork. 45747cc765a6SThomas Gleixner 457555a97402SThomas Gleixner prctl,ibpb 457655a97402SThomas Gleixner - Like "prctl" above, but only STIBP is 457755a97402SThomas Gleixner controlled per thread. IBPB is issued 457855a97402SThomas Gleixner always when switching between different user 457955a97402SThomas Gleixner space processes. 458055a97402SThomas Gleixner 45816b3e64c2SThomas Gleixner seccomp 45826b3e64c2SThomas Gleixner - Same as "prctl" above, but all seccomp 45836b3e64c2SThomas Gleixner threads will enable the mitigation unless 45846b3e64c2SThomas Gleixner they explicitly opt out. 45856b3e64c2SThomas Gleixner 458655a97402SThomas Gleixner seccomp,ibpb 458755a97402SThomas Gleixner - Like "seccomp" above, but only STIBP is 458855a97402SThomas Gleixner controlled per thread. IBPB is issued 458955a97402SThomas Gleixner always when switching between different 459055a97402SThomas Gleixner user space processes. 459155a97402SThomas Gleixner 4592fa1202efSThomas Gleixner auto - Kernel selects the mitigation depending on 4593fa1202efSThomas Gleixner the available CPU features and vulnerability. 45946b3e64c2SThomas Gleixner 45956b3e64c2SThomas Gleixner Default mitigation: 45966b3e64c2SThomas Gleixner If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl" 4597fa1202efSThomas Gleixner 4598fa1202efSThomas Gleixner Not specifying this option is equivalent to 4599fa1202efSThomas Gleixner spectre_v2_user=auto. 4600fa1202efSThomas Gleixner 460124f7fc83SKonrad Rzeszutek Wilk spec_store_bypass_disable= 460224f7fc83SKonrad Rzeszutek Wilk [HW] Control Speculative Store Bypass (SSB) Disable mitigation 460324f7fc83SKonrad Rzeszutek Wilk (Speculative Store Bypass vulnerability) 460424f7fc83SKonrad Rzeszutek Wilk 460524f7fc83SKonrad Rzeszutek Wilk Certain CPUs are vulnerable to an exploit against a 460624f7fc83SKonrad Rzeszutek Wilk a common industry wide performance optimization known 460724f7fc83SKonrad Rzeszutek Wilk as "Speculative Store Bypass" in which recent stores 460824f7fc83SKonrad Rzeszutek Wilk to the same memory location may not be observed by 460924f7fc83SKonrad Rzeszutek Wilk later loads during speculative execution. The idea 461024f7fc83SKonrad Rzeszutek Wilk is that such stores are unlikely and that they can 461124f7fc83SKonrad Rzeszutek Wilk be detected prior to instruction retirement at the 461224f7fc83SKonrad Rzeszutek Wilk end of a particular speculation execution window. 461324f7fc83SKonrad Rzeszutek Wilk 461424f7fc83SKonrad Rzeszutek Wilk In vulnerable processors, the speculatively forwarded 461524f7fc83SKonrad Rzeszutek Wilk store can be used in a cache side channel attack, for 461624f7fc83SKonrad Rzeszutek Wilk example to read memory to which the attacker does not 461724f7fc83SKonrad Rzeszutek Wilk directly have access (e.g. inside sandboxed code). 461824f7fc83SKonrad Rzeszutek Wilk 461924f7fc83SKonrad Rzeszutek Wilk This parameter controls whether the Speculative Store 462024f7fc83SKonrad Rzeszutek Wilk Bypass optimization is used. 462124f7fc83SKonrad Rzeszutek Wilk 46226b4c1360SMichael Ellerman On x86 the options are: 46236b4c1360SMichael Ellerman 462424f7fc83SKonrad Rzeszutek Wilk on - Unconditionally disable Speculative Store Bypass 462524f7fc83SKonrad Rzeszutek Wilk off - Unconditionally enable Speculative Store Bypass 462624f7fc83SKonrad Rzeszutek Wilk auto - Kernel detects whether the CPU model contains an 462724f7fc83SKonrad Rzeszutek Wilk implementation of Speculative Store Bypass and 4628f21b53b2SKees Cook picks the most appropriate mitigation. If the 4629f21b53b2SKees Cook CPU is not vulnerable, "off" is selected. If the 4630f21b53b2SKees Cook CPU is vulnerable the default mitigation is 4631f21b53b2SKees Cook architecture and Kconfig dependent. See below. 4632a73ec77eSThomas Gleixner prctl - Control Speculative Store Bypass per thread 4633a73ec77eSThomas Gleixner via prctl. Speculative Store Bypass is enabled 4634a73ec77eSThomas Gleixner for a process by default. The state of the control 4635a73ec77eSThomas Gleixner is inherited on fork. 4636f21b53b2SKees Cook seccomp - Same as "prctl" above, but all seccomp threads 4637f21b53b2SKees Cook will disable SSB unless they explicitly opt out. 463824f7fc83SKonrad Rzeszutek Wilk 4639f21b53b2SKees Cook Default mitigations: 4640f21b53b2SKees Cook X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl" 4641f21b53b2SKees Cook 46426b4c1360SMichael Ellerman On powerpc the options are: 46436b4c1360SMichael Ellerman 46446b4c1360SMichael Ellerman on,auto - On Power8 and Power9 insert a store-forwarding 46456b4c1360SMichael Ellerman barrier on kernel entry and exit. On Power7 46466b4c1360SMichael Ellerman perform a software flush on kernel entry and 46476b4c1360SMichael Ellerman exit. 46486b4c1360SMichael Ellerman off - No action. 46496b4c1360SMichael Ellerman 46506b4c1360SMichael Ellerman Not specifying this option is equivalent to 46516b4c1360SMichael Ellerman spec_store_bypass_disable=auto. 46526b4c1360SMichael Ellerman 4653e52347bdSJani Nikula spia_io_base= [HW,MTD] 4654e52347bdSJani Nikula spia_fio_base= 4655e52347bdSJani Nikula spia_pedr= 4656e52347bdSJani Nikula spia_peddr= 4657e52347bdSJani Nikula 4658c350c008SPaul E. McKenney srcutree.counter_wrap_check [KNL] 4659c350c008SPaul E. McKenney Specifies how frequently to check for 4660c350c008SPaul E. McKenney grace-period sequence counter wrap for the 4661c350c008SPaul E. McKenney srcu_data structure's ->srcu_gp_seq_needed field. 4662c350c008SPaul E. McKenney The greater the number of bits set in this kernel 4663c350c008SPaul E. McKenney parameter, the less frequently counter wrap will 4664c350c008SPaul E. McKenney be checked for. Note that the bottom two bits 4665c350c008SPaul E. McKenney are ignored. 4666c350c008SPaul E. McKenney 466722607d66SPaul E. McKenney srcutree.exp_holdoff [KNL] 466822607d66SPaul E. McKenney Specifies how many nanoseconds must elapse 466922607d66SPaul E. McKenney since the end of the last SRCU grace period for 467022607d66SPaul E. McKenney a given srcu_struct until the next normal SRCU 467122607d66SPaul E. McKenney grace period will be considered for automatic 467222607d66SPaul E. McKenney expediting. Set to zero to disable automatic 467322607d66SPaul E. McKenney expediting. 467422607d66SPaul E. McKenney 4675a43ae4dfSMarc Zyngier ssbd= [ARM64,HW] 4676a43ae4dfSMarc Zyngier Speculative Store Bypass Disable control 4677a43ae4dfSMarc Zyngier 4678a43ae4dfSMarc Zyngier On CPUs that are vulnerable to the Speculative 4679a43ae4dfSMarc Zyngier Store Bypass vulnerability and offer a 4680a43ae4dfSMarc Zyngier firmware based mitigation, this parameter 4681a43ae4dfSMarc Zyngier indicates how the mitigation should be used: 4682a43ae4dfSMarc Zyngier 4683a43ae4dfSMarc Zyngier force-on: Unconditionally enable mitigation for 4684a43ae4dfSMarc Zyngier for both kernel and userspace 4685a43ae4dfSMarc Zyngier force-off: Unconditionally disable mitigation for 4686a43ae4dfSMarc Zyngier for both kernel and userspace 4687a43ae4dfSMarc Zyngier kernel: Always enable mitigation in the 4688a43ae4dfSMarc Zyngier kernel, and offer a prctl interface 4689a43ae4dfSMarc Zyngier to allow userspace to register its 4690a43ae4dfSMarc Zyngier interest in being mitigated too. 4691a43ae4dfSMarc Zyngier 46921be7107fSHugh Dickins stack_guard_gap= [MM] 46931be7107fSHugh Dickins override the default stack gap protection. The value 46941be7107fSHugh Dickins is in page units and it defines how many pages prior 46951be7107fSHugh Dickins to (for stacks growing down) resp. after (for stacks 46961be7107fSHugh Dickins growing up) the main stack are reserved for no other 46971be7107fSHugh Dickins mapping. Default value is 256 pages. 46981be7107fSHugh Dickins 4699e52347bdSJani Nikula stacktrace [FTRACE] 4700e52347bdSJani Nikula Enabled the stack tracer on boot up. 4701e52347bdSJani Nikula 4702e52347bdSJani Nikula stacktrace_filter=[function-list] 4703e52347bdSJani Nikula [FTRACE] Limit the functions that the stack tracer 4704e52347bdSJani Nikula will trace at boot up. function-list is a comma separated 4705e52347bdSJani Nikula list of functions. This list can be changed at run 4706e52347bdSJani Nikula time by the stack_trace_filter file in the debugfs 4707e52347bdSJani Nikula tracing directory. Note, this enables stack tracing 4708e52347bdSJani Nikula and the stacktrace above is not needed. 4709e52347bdSJani Nikula 4710e52347bdSJani Nikula sti= [PARISC,HW] 4711e52347bdSJani Nikula Format: <num> 4712e52347bdSJani Nikula Set the STI (builtin display/keyboard on the HP-PARISC 4713e52347bdSJani Nikula machines) console (graphic card) which should be used 4714e52347bdSJani Nikula as the initial boot-console. 4715e52347bdSJani Nikula See also comment in drivers/video/console/sticore.c. 4716e52347bdSJani Nikula 4717e52347bdSJani Nikula sti_font= [HW] 4718e52347bdSJani Nikula See comment in drivers/video/console/sticore.c. 4719e52347bdSJani Nikula 4720e52347bdSJani Nikula stifb= [HW] 4721e52347bdSJani Nikula Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 4722e52347bdSJani Nikula 4723e52347bdSJani Nikula sunrpc.min_resvport= 4724e52347bdSJani Nikula sunrpc.max_resvport= 4725e52347bdSJani Nikula [NFS,SUNRPC] 4726e52347bdSJani Nikula SunRPC servers often require that client requests 4727e52347bdSJani Nikula originate from a privileged port (i.e. a port in the 4728e52347bdSJani Nikula range 0 < portnr < 1024). 4729e52347bdSJani Nikula An administrator who wishes to reserve some of these 4730e52347bdSJani Nikula ports for other uses may adjust the range that the 4731e52347bdSJani Nikula kernel's sunrpc client considers to be privileged 4732e52347bdSJani Nikula using these two parameters to set the minimum and 4733e52347bdSJani Nikula maximum port values. 4734e52347bdSJani Nikula 4735e52347bdSJani Nikula sunrpc.svc_rpc_per_connection_limit= 4736e52347bdSJani Nikula [NFS,SUNRPC] 4737e52347bdSJani Nikula Limit the number of requests that the server will 4738e52347bdSJani Nikula process in parallel from a single connection. 4739e52347bdSJani Nikula The default value is 0 (no limit). 4740e52347bdSJani Nikula 4741e52347bdSJani Nikula sunrpc.pool_mode= 4742e52347bdSJani Nikula [NFS] 4743e52347bdSJani Nikula Control how the NFS server code allocates CPUs to 4744e52347bdSJani Nikula service thread pools. Depending on how many NICs 4745e52347bdSJani Nikula you have and where their interrupts are bound, this 4746e52347bdSJani Nikula option will affect which CPUs will do NFS serving. 4747e52347bdSJani Nikula Note: this parameter cannot be changed while the 4748e52347bdSJani Nikula NFS server is running. 4749e52347bdSJani Nikula 4750e52347bdSJani Nikula auto the server chooses an appropriate mode 4751e52347bdSJani Nikula automatically using heuristics 4752e52347bdSJani Nikula global a single global pool contains all CPUs 4753e52347bdSJani Nikula percpu one pool for each CPU 4754e52347bdSJani Nikula pernode one pool for each NUMA node (equivalent 4755e52347bdSJani Nikula to global on non-NUMA machines) 4756e52347bdSJani Nikula 4757e52347bdSJani Nikula sunrpc.tcp_slot_table_entries= 4758e52347bdSJani Nikula sunrpc.udp_slot_table_entries= 4759e52347bdSJani Nikula [NFS,SUNRPC] 4760e52347bdSJani Nikula Sets the upper limit on the number of simultaneous 4761e52347bdSJani Nikula RPC calls that can be sent from the client to a 4762e52347bdSJani Nikula server. Increasing these values may allow you to 4763e52347bdSJani Nikula improve throughput, but will also increase the 4764e52347bdSJani Nikula amount of memory reserved for use by the client. 4765e52347bdSJani Nikula 4766e52347bdSJani Nikula suspend.pm_test_delay= 4767e52347bdSJani Nikula [SUSPEND] 4768e52347bdSJani Nikula Sets the number of seconds to remain in a suspend test 4769e52347bdSJani Nikula mode before resuming the system (see 4770e52347bdSJani Nikula /sys/power/pm_test). Only available when CONFIG_PM_DEBUG 4771e52347bdSJani Nikula is set. Default value is 5. 4772e52347bdSJani Nikula 47736a9c930bSRam Pai svm= [PPC] 47746a9c930bSRam Pai Format: { on | off | y | n | 1 | 0 } 47756a9c930bSRam Pai This parameter controls use of the Protected 47766a9c930bSRam Pai Execution Facility on pSeries. 47776a9c930bSRam Pai 4778e52347bdSJani Nikula swapaccount=[0|1] 4779e52347bdSJani Nikula [KNL] Enable accounting of swap in memory resource 4780e52347bdSJani Nikula controller if no parameter or 1 is given or disable 4781da82c92fSMauro Carvalho Chehab it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst) 4782e52347bdSJani Nikula 4783e52347bdSJani Nikula swiotlb= [ARM,IA-64,PPC,MIPS,X86] 4784fff5d992SGeert Uytterhoeven Format: { <int> | force | noforce } 4785e52347bdSJani Nikula <int> -- Number of I/O TLB slabs 4786e52347bdSJani Nikula force -- force using of bounce buffers even if they 4787e52347bdSJani Nikula wouldn't be automatically used by the kernel 4788fff5d992SGeert Uytterhoeven noforce -- Never use bounce buffers (for debugging) 4789e52347bdSJani Nikula 4790e52347bdSJani Nikula switches= [HW,M68k] 4791e52347bdSJani Nikula 4792e52347bdSJani Nikula sysfs.deprecated=0|1 [KNL] 4793e52347bdSJani Nikula Enable/disable old style sysfs layout for old udev 4794e52347bdSJani Nikula on older distributions. When this option is enabled 4795e52347bdSJani Nikula very new udev will not work anymore. When this option 4796e52347bdSJani Nikula is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) 4797e52347bdSJani Nikula in older udev will not work anymore. 4798e52347bdSJani Nikula Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in 4799e52347bdSJani Nikula the kernel configuration. 4800e52347bdSJani Nikula 4801e52347bdSJani Nikula sysrq_always_enabled 4802e52347bdSJani Nikula [KNL] 4803e52347bdSJani Nikula Ignore sysrq setting - this boot parameter will 4804e52347bdSJani Nikula neutralize any effect of /proc/sys/kernel/sysrq. 4805e52347bdSJani Nikula Useful for debugging. 4806e52347bdSJani Nikula 4807e52347bdSJani Nikula tcpmhash_entries= [KNL,NET] 4808e52347bdSJani Nikula Set the number of tcp_metrics_hash slots. 4809e52347bdSJani Nikula Default value is 8192 or 16384 depending on total 4810e52347bdSJani Nikula ram pages. This is used to specify the TCP metrics 4811e52347bdSJani Nikula cache size. See Documentation/networking/ip-sysctl.txt 4812e52347bdSJani Nikula "tcp_no_metrics_save" section for more details. 4813e52347bdSJani Nikula 4814e52347bdSJani Nikula tdfx= [HW,DRM] 4815e52347bdSJani Nikula 4816e52347bdSJani Nikula test_suspend= [SUSPEND][,N] 4817e52347bdSJani Nikula Specify "mem" (for Suspend-to-RAM) or "standby" (for 4818e52347bdSJani Nikula standby suspend) or "freeze" (for suspend type freeze) 4819e52347bdSJani Nikula as the system sleep state during system startup with 4820e52347bdSJani Nikula the optional capability to repeat N number of times. 4821e52347bdSJani Nikula The system is woken from this state using a 4822e52347bdSJani Nikula wakeup-capable RTC alarm. 4823e52347bdSJani Nikula 4824e52347bdSJani Nikula thash_entries= [KNL,NET] 4825e52347bdSJani Nikula Set number of hash buckets for TCP connection 4826e52347bdSJani Nikula 4827e52347bdSJani Nikula thermal.act= [HW,ACPI] 4828e52347bdSJani Nikula -1: disable all active trip points in all thermal zones 4829e52347bdSJani Nikula <degrees C>: override all lowest active trip points 4830e52347bdSJani Nikula 4831e52347bdSJani Nikula thermal.crt= [HW,ACPI] 4832e52347bdSJani Nikula -1: disable all critical trip points in all thermal zones 4833e52347bdSJani Nikula <degrees C>: override all critical trip points 4834e52347bdSJani Nikula 4835e52347bdSJani Nikula thermal.nocrt= [HW,ACPI] 4836e52347bdSJani Nikula Set to disable actions on ACPI thermal zone 4837e52347bdSJani Nikula critical and hot trip points. 4838e52347bdSJani Nikula 4839e52347bdSJani Nikula thermal.off= [HW,ACPI] 4840e52347bdSJani Nikula 1: disable ACPI thermal control 4841e52347bdSJani Nikula 4842e52347bdSJani Nikula thermal.psv= [HW,ACPI] 4843e52347bdSJani Nikula -1: disable all passive trip points 4844e52347bdSJani Nikula <degrees C>: override all passive trip points to this 4845e52347bdSJani Nikula value 4846e52347bdSJani Nikula 4847e52347bdSJani Nikula thermal.tzp= [HW,ACPI] 4848e52347bdSJani Nikula Specify global default ACPI thermal zone polling rate 4849e52347bdSJani Nikula <deci-seconds>: poll all this frequency 4850e52347bdSJani Nikula 0: no polling (default) 4851e52347bdSJani Nikula 4852e52347bdSJani Nikula threadirqs [KNL] 4853e52347bdSJani Nikula Force threading of all interrupt handlers except those 4854e52347bdSJani Nikula marked explicitly IRQF_NO_THREAD. 4855e52347bdSJani Nikula 4856e52347bdSJani Nikula topology= [S390] 4857e52347bdSJani Nikula Format: {off | on} 4858e52347bdSJani Nikula Specify if the kernel should make use of the cpu 4859e52347bdSJani Nikula topology information if the hardware supports this. 4860e52347bdSJani Nikula The scheduler will make use of this information and 4861e52347bdSJani Nikula e.g. base its process migration decisions on it. 4862e52347bdSJani Nikula Default is on. 4863e52347bdSJani Nikula 4864e52347bdSJani Nikula topology_updates= [KNL, PPC, NUMA] 4865e52347bdSJani Nikula Format: {off} 4866e52347bdSJani Nikula Specify if the kernel should ignore (off) 4867e52347bdSJani Nikula topology updates sent by the hypervisor to this 4868e52347bdSJani Nikula LPAR. 4869e52347bdSJani Nikula 4870e52347bdSJani Nikula tp720= [HW,PS2] 4871e52347bdSJani Nikula 4872e52347bdSJani Nikula tpm_suspend_pcr=[HW,TPM] 4873e52347bdSJani Nikula Format: integer pcr id 4874e52347bdSJani Nikula Specify that at suspend time, the tpm driver 4875e52347bdSJani Nikula should extend the specified pcr with zeros, 4876e52347bdSJani Nikula as a workaround for some chips which fail to 4877e52347bdSJani Nikula flush the last written pcr on TPM_SaveState. 4878e52347bdSJani Nikula This will guarantee that all the other pcrs 4879e52347bdSJani Nikula are saved. 4880e52347bdSJani Nikula 4881e52347bdSJani Nikula trace_buf_size=nn[KMG] 4882e52347bdSJani Nikula [FTRACE] will set tracing buffer size on each cpu. 4883e52347bdSJani Nikula 4884e52347bdSJani Nikula trace_event=[event-list] 4885e52347bdSJani Nikula [FTRACE] Set and start specified trace events in order 4886e52347bdSJani Nikula to facilitate early boot debugging. The event-list is a 4887e52347bdSJani Nikula comma separated list of trace events to enable. See 48885fb94e9cSMauro Carvalho Chehab also Documentation/trace/events.rst 4889e52347bdSJani Nikula 4890e52347bdSJani Nikula trace_options=[option-list] 4891e52347bdSJani Nikula [FTRACE] Enable or disable tracer options at boot. 4892e52347bdSJani Nikula The option-list is a comma delimited list of options 4893e52347bdSJani Nikula that can be enabled or disabled just as if you were 4894e52347bdSJani Nikula to echo the option name into 4895e52347bdSJani Nikula 4896e52347bdSJani Nikula /sys/kernel/debug/tracing/trace_options 4897e52347bdSJani Nikula 4898e52347bdSJani Nikula For example, to enable stacktrace option (to dump the 4899e52347bdSJani Nikula stack trace of each event), add to the command line: 4900e52347bdSJani Nikula 4901e52347bdSJani Nikula trace_options=stacktrace 4902e52347bdSJani Nikula 49035fb94e9cSMauro Carvalho Chehab See also Documentation/trace/ftrace.rst "trace options" 4904e52347bdSJani Nikula section. 4905e52347bdSJani Nikula 4906e52347bdSJani Nikula tp_printk[FTRACE] 4907e52347bdSJani Nikula Have the tracepoints sent to printk as well as the 4908e52347bdSJani Nikula tracing ring buffer. This is useful for early boot up 4909e52347bdSJani Nikula where the system hangs or reboots and does not give the 4910e52347bdSJani Nikula option for reading the tracing buffer or performing a 4911e52347bdSJani Nikula ftrace_dump_on_oops. 4912e52347bdSJani Nikula 4913e52347bdSJani Nikula To turn off having tracepoints sent to printk, 4914e52347bdSJani Nikula echo 0 > /proc/sys/kernel/tracepoint_printk 4915e52347bdSJani Nikula Note, echoing 1 into this file without the 4916e52347bdSJani Nikula tracepoint_printk kernel cmdline option has no effect. 4917e52347bdSJani Nikula 4918e52347bdSJani Nikula ** CAUTION ** 4919e52347bdSJani Nikula 4920e52347bdSJani Nikula Having tracepoints sent to printk() and activating high 4921e52347bdSJani Nikula frequency tracepoints such as irq or sched, can cause 4922e52347bdSJani Nikula the system to live lock. 4923e52347bdSJani Nikula 4924e52347bdSJani Nikula traceoff_on_warning 4925e52347bdSJani Nikula [FTRACE] enable this option to disable tracing when a 4926e52347bdSJani Nikula warning is hit. This turns off "tracing_on". Tracing can 4927e52347bdSJani Nikula be enabled again by echoing '1' into the "tracing_on" 4928e52347bdSJani Nikula file located in /sys/kernel/debug/tracing/ 4929e52347bdSJani Nikula 4930e52347bdSJani Nikula This option is useful, as it disables the trace before 4931e52347bdSJani Nikula the WARNING dump is called, which prevents the trace to 4932e52347bdSJani Nikula be filled with content caused by the warning output. 4933e52347bdSJani Nikula 4934e52347bdSJani Nikula This option can also be set at run time via the sysctl 4935e52347bdSJani Nikula option: kernel/traceoff_on_warning 4936e52347bdSJani Nikula 4937e52347bdSJani Nikula transparent_hugepage= 4938e52347bdSJani Nikula [KNL] 4939e52347bdSJani Nikula Format: [always|madvise|never] 4940e52347bdSJani Nikula Can be used to control the default behavior of the system 4941e52347bdSJani Nikula with respect to transparent hugepages. 494245c9a74fSMike Rapoport See Documentation/admin-guide/mm/transhuge.rst 494345c9a74fSMike Rapoport for more details. 4944e52347bdSJani Nikula 4945e52347bdSJani Nikula tsc= Disable clocksource stability checks for TSC. 4946e52347bdSJani Nikula Format: <string> 4947e52347bdSJani Nikula [x86] reliable: mark tsc clocksource as reliable, this 4948e52347bdSJani Nikula disables clocksource verification at runtime, as well 4949e52347bdSJani Nikula as the stability checks done at bootup. Used to enable 4950e52347bdSJani Nikula high-resolution timer mode on older hardware, and in 4951e52347bdSJani Nikula virtualized environment. 4952e52347bdSJani Nikula [x86] noirqtime: Do not use TSC to do irq accounting. 4953e52347bdSJani Nikula Used to run time disable IRQ_TIME_ACCOUNTING on any 4954e52347bdSJani Nikula platforms where RDTSC is slow and this accounting 4955e52347bdSJani Nikula can add overhead. 49566be53520SDou Liyang [x86] unstable: mark the TSC clocksource as unstable, this 49576be53520SDou Liyang marks the TSC unconditionally unstable at bootup and 49586be53520SDou Liyang avoids any further wobbles once the TSC watchdog notices. 49590f0b7e1cSJuri Lelli [x86] nowatchdog: disable clocksource watchdog. Used 49600f0b7e1cSJuri Lelli in situations with strict latency requirements (where 49610f0b7e1cSJuri Lelli interruptions from clocksource watchdog are not 49620f0b7e1cSJuri Lelli acceptable). 4963e52347bdSJani Nikula 496495c5824fSPawan Gupta tsx= [X86] Control Transactional Synchronization 496595c5824fSPawan Gupta Extensions (TSX) feature in Intel processors that 496695c5824fSPawan Gupta support TSX control. 496795c5824fSPawan Gupta 496895c5824fSPawan Gupta This parameter controls the TSX feature. The options are: 496995c5824fSPawan Gupta 497095c5824fSPawan Gupta on - Enable TSX on the system. Although there are 497195c5824fSPawan Gupta mitigations for all known security vulnerabilities, 497295c5824fSPawan Gupta TSX has been known to be an accelerator for 497395c5824fSPawan Gupta several previous speculation-related CVEs, and 497495c5824fSPawan Gupta so there may be unknown security risks associated 497595c5824fSPawan Gupta with leaving it enabled. 497695c5824fSPawan Gupta 497795c5824fSPawan Gupta off - Disable TSX on the system. (Note that this 497895c5824fSPawan Gupta option takes effect only on newer CPUs which are 497995c5824fSPawan Gupta not vulnerable to MDS, i.e., have 498095c5824fSPawan Gupta MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get 498195c5824fSPawan Gupta the new IA32_TSX_CTRL MSR through a microcode 498295c5824fSPawan Gupta update. This new MSR allows for the reliable 498395c5824fSPawan Gupta deactivation of the TSX functionality.) 498495c5824fSPawan Gupta 49857531a359SPawan Gupta auto - Disable TSX if X86_BUG_TAA is present, 49867531a359SPawan Gupta otherwise enable TSX on the system. 49877531a359SPawan Gupta 498895c5824fSPawan Gupta Not specifying this option is equivalent to tsx=off. 498995c5824fSPawan Gupta 499095c5824fSPawan Gupta See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst 499195c5824fSPawan Gupta for more details. 499295c5824fSPawan Gupta 4993a7a248c5SPawan Gupta tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async 4994a7a248c5SPawan Gupta Abort (TAA) vulnerability. 4995a7a248c5SPawan Gupta 4996a7a248c5SPawan Gupta Similar to Micro-architectural Data Sampling (MDS) 4997a7a248c5SPawan Gupta certain CPUs that support Transactional 4998a7a248c5SPawan Gupta Synchronization Extensions (TSX) are vulnerable to an 4999a7a248c5SPawan Gupta exploit against CPU internal buffers which can forward 5000a7a248c5SPawan Gupta information to a disclosure gadget under certain 5001a7a248c5SPawan Gupta conditions. 5002a7a248c5SPawan Gupta 5003a7a248c5SPawan Gupta In vulnerable processors, the speculatively forwarded 5004a7a248c5SPawan Gupta data can be used in a cache side channel attack, to 5005a7a248c5SPawan Gupta access data to which the attacker does not have direct 5006a7a248c5SPawan Gupta access. 5007a7a248c5SPawan Gupta 5008a7a248c5SPawan Gupta This parameter controls the TAA mitigation. The 5009a7a248c5SPawan Gupta options are: 5010a7a248c5SPawan Gupta 5011a7a248c5SPawan Gupta full - Enable TAA mitigation on vulnerable CPUs 5012a7a248c5SPawan Gupta if TSX is enabled. 5013a7a248c5SPawan Gupta 5014a7a248c5SPawan Gupta full,nosmt - Enable TAA mitigation and disable SMT on 5015a7a248c5SPawan Gupta vulnerable CPUs. If TSX is disabled, SMT 5016a7a248c5SPawan Gupta is not disabled because CPU is not 5017a7a248c5SPawan Gupta vulnerable to cross-thread TAA attacks. 5018a7a248c5SPawan Gupta off - Unconditionally disable TAA mitigation 5019a7a248c5SPawan Gupta 502064870ed1SWaiman Long On MDS-affected machines, tsx_async_abort=off can be 502164870ed1SWaiman Long prevented by an active MDS mitigation as both vulnerabilities 502264870ed1SWaiman Long are mitigated with the same mechanism so in order to disable 502364870ed1SWaiman Long this mitigation, you need to specify mds=off too. 502464870ed1SWaiman Long 5025a7a248c5SPawan Gupta Not specifying this option is equivalent to 5026a7a248c5SPawan Gupta tsx_async_abort=full. On CPUs which are MDS affected 5027a7a248c5SPawan Gupta and deploy MDS mitigation, TAA mitigation is not 5028a7a248c5SPawan Gupta required and doesn't provide any additional 5029a7a248c5SPawan Gupta mitigation. 5030a7a248c5SPawan Gupta 5031a7a248c5SPawan Gupta For details see: 5032a7a248c5SPawan Gupta Documentation/admin-guide/hw-vuln/tsx_async_abort.rst 5033a7a248c5SPawan Gupta 5034e52347bdSJani Nikula turbografx.map[2|3]= [HW,JOY] 5035e52347bdSJani Nikula TurboGraFX parallel port interface 5036e52347bdSJani Nikula Format: 5037e52347bdSJani Nikula <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 50381752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 5039e52347bdSJani Nikula 5040e52347bdSJani Nikula udbg-immortal [PPC] When debugging early kernel crashes that 5041e52347bdSJani Nikula happen after console_init() and before a proper 5042e52347bdSJani Nikula console driver takes over, this boot options might 5043e52347bdSJani Nikula help "seeing" what's going on. 5044e52347bdSJani Nikula 5045e52347bdSJani Nikula uhash_entries= [KNL,NET] 5046e52347bdSJani Nikula Set number of hash buckets for UDP/UDP-Lite connections 5047e52347bdSJani Nikula 5048e52347bdSJani Nikula uhci-hcd.ignore_oc= 5049e52347bdSJani Nikula [USB] Ignore overcurrent events (default N). 5050e52347bdSJani Nikula Some badly-designed motherboards generate lots of 5051e52347bdSJani Nikula bogus events, for ports that aren't wired to 5052e52347bdSJani Nikula anything. Set this parameter to avoid log spamming. 5053e52347bdSJani Nikula Note that genuine overcurrent events won't be 5054e52347bdSJani Nikula reported either. 5055e52347bdSJani Nikula 5056e52347bdSJani Nikula unknown_nmi_panic 5057e52347bdSJani Nikula [X86] Cause panic on unknown NMI. 5058e52347bdSJani Nikula 5059e52347bdSJani Nikula usbcore.authorized_default= 5060e52347bdSJani Nikula [USB] Default USB device authorization: 5061e52347bdSJani Nikula (default -1 = authorized except for wireless USB, 50627bae0432SDmitry Torokhov 0 = not authorized, 1 = authorized, 2 = authorized 50637bae0432SDmitry Torokhov if device connected to internal port) 5064e52347bdSJani Nikula 5065e52347bdSJani Nikula usbcore.autosuspend= 5066e52347bdSJani Nikula [USB] The autosuspend time delay (in seconds) used 5067e52347bdSJani Nikula for newly-detected USB devices (default 2). This 5068e52347bdSJani Nikula is the time required before an idle device will be 5069e52347bdSJani Nikula autosuspended. Devices for which the delay is set 5070e52347bdSJani Nikula to a negative value won't be autosuspended at all. 5071e52347bdSJani Nikula 5072e52347bdSJani Nikula usbcore.usbfs_snoop= 5073e52347bdSJani Nikula [USB] Set to log all usbfs traffic (default 0 = off). 5074e52347bdSJani Nikula 5075e52347bdSJani Nikula usbcore.usbfs_snoop_max= 5076e52347bdSJani Nikula [USB] Maximum number of bytes to snoop in each URB 5077e52347bdSJani Nikula (default = 65536). 5078e52347bdSJani Nikula 5079e52347bdSJani Nikula usbcore.blinkenlights= 5080e52347bdSJani Nikula [USB] Set to cycle leds on hubs (default 0 = off). 5081e52347bdSJani Nikula 5082e52347bdSJani Nikula usbcore.old_scheme_first= 5083e52347bdSJani Nikula [USB] Start with the old device initialization 5084bd0e6c96SZeng Tao scheme, applies only to low and full-speed devices 5085bd0e6c96SZeng Tao (default 0 = off). 5086e52347bdSJani Nikula 5087e52347bdSJani Nikula usbcore.usbfs_memory_mb= 5088e52347bdSJani Nikula [USB] Memory limit (in MB) for buffers allocated by 5089e52347bdSJani Nikula usbfs (default = 16, 0 = max = 2047). 5090e52347bdSJani Nikula 5091e52347bdSJani Nikula usbcore.use_both_schemes= 5092e52347bdSJani Nikula [USB] Try the other device initialization scheme 5093e52347bdSJani Nikula if the first one fails (default 1 = enabled). 5094e52347bdSJani Nikula 5095e52347bdSJani Nikula usbcore.initial_descriptor_timeout= 5096e52347bdSJani Nikula [USB] Specifies timeout for the initial 64-byte 5097e52347bdSJani Nikula USB_REQ_GET_DESCRIPTOR request in milliseconds 5098e52347bdSJani Nikula (default 5000 = 5.0 seconds). 5099e52347bdSJani Nikula 5100e52347bdSJani Nikula usbcore.nousb [USB] Disable the USB subsystem 5101e52347bdSJani Nikula 5102027bd6caSKai-Heng Feng usbcore.quirks= 5103027bd6caSKai-Heng Feng [USB] A list of quirk entries to augment the built-in 5104027bd6caSKai-Heng Feng usb core quirk list. List entries are separated by 5105027bd6caSKai-Heng Feng commas. Each entry has the form 5106027bd6caSKai-Heng Feng VendorID:ProductID:Flags. The IDs are 4-digit hex 5107027bd6caSKai-Heng Feng numbers and Flags is a set of letters. Each letter 5108027bd6caSKai-Heng Feng will change the built-in quirk; setting it if it is 5109027bd6caSKai-Heng Feng clear and clearing it if it is set. The letters have 5110027bd6caSKai-Heng Feng the following meanings: 5111027bd6caSKai-Heng Feng a = USB_QUIRK_STRING_FETCH_255 (string 5112027bd6caSKai-Heng Feng descriptors must not be fetched using 5113027bd6caSKai-Heng Feng a 255-byte read); 5114027bd6caSKai-Heng Feng b = USB_QUIRK_RESET_RESUME (device can't resume 5115027bd6caSKai-Heng Feng correctly so reset it instead); 5116027bd6caSKai-Heng Feng c = USB_QUIRK_NO_SET_INTF (device can't handle 5117027bd6caSKai-Heng Feng Set-Interface requests); 5118027bd6caSKai-Heng Feng d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't 5119027bd6caSKai-Heng Feng handle its Configuration or Interface 5120027bd6caSKai-Heng Feng strings); 5121027bd6caSKai-Heng Feng e = USB_QUIRK_RESET (device can't be reset 5122027bd6caSKai-Heng Feng (e.g morph devices), don't use reset); 5123027bd6caSKai-Heng Feng f = USB_QUIRK_HONOR_BNUMINTERFACES (device has 5124027bd6caSKai-Heng Feng more interface descriptions than the 5125027bd6caSKai-Heng Feng bNumInterfaces count, and can't handle 5126027bd6caSKai-Heng Feng talking to these interfaces); 5127027bd6caSKai-Heng Feng g = USB_QUIRK_DELAY_INIT (device needs a pause 5128027bd6caSKai-Heng Feng during initialization, after we read 5129027bd6caSKai-Heng Feng the device descriptor); 5130027bd6caSKai-Heng Feng h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For 5131027bd6caSKai-Heng Feng high speed and super speed interrupt 5132027bd6caSKai-Heng Feng endpoints, the USB 2.0 and USB 3.0 spec 5133027bd6caSKai-Heng Feng require the interval in microframes (1 5134027bd6caSKai-Heng Feng microframe = 125 microseconds) to be 5135027bd6caSKai-Heng Feng calculated as interval = 2 ^ 5136027bd6caSKai-Heng Feng (bInterval-1). 5137027bd6caSKai-Heng Feng Devices with this quirk report their 5138027bd6caSKai-Heng Feng bInterval as the result of this 5139027bd6caSKai-Heng Feng calculation instead of the exponent 5140027bd6caSKai-Heng Feng variable used in the calculation); 5141027bd6caSKai-Heng Feng i = USB_QUIRK_DEVICE_QUALIFIER (device can't 5142027bd6caSKai-Heng Feng handle device_qualifier descriptor 5143027bd6caSKai-Heng Feng requests); 5144027bd6caSKai-Heng Feng j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device 5145027bd6caSKai-Heng Feng generates spurious wakeup, ignore 5146027bd6caSKai-Heng Feng remote wakeup capability); 5147027bd6caSKai-Heng Feng k = USB_QUIRK_NO_LPM (device can't handle Link 5148027bd6caSKai-Heng Feng Power Management); 5149027bd6caSKai-Heng Feng l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL 5150027bd6caSKai-Heng Feng (Device reports its bInterval as linear 5151027bd6caSKai-Heng Feng frames instead of the USB 2.0 5152027bd6caSKai-Heng Feng calculation); 5153027bd6caSKai-Heng Feng m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs 5154027bd6caSKai-Heng Feng to be disconnected before suspend to 51554d8d5a39SKai-Heng Feng prevent spurious wakeup); 51564d8d5a39SKai-Heng Feng n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a 51574d8d5a39SKai-Heng Feng pause after every control message); 5158781f0766SKai-Heng Feng o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra 5159781f0766SKai-Heng Feng delay after resetting its port); 5160027bd6caSKai-Heng Feng Example: quirks=0781:5580:bk,0a5c:5834:gij 5161027bd6caSKai-Heng Feng 5162e52347bdSJani Nikula usbhid.mousepoll= 5163e52347bdSJani Nikula [USBHID] The interval which mice are to be polled at. 5164e52347bdSJani Nikula 5165933bfe4dSTobias Jakobi usbhid.jspoll= 5166933bfe4dSTobias Jakobi [USBHID] The interval which joysticks are to be polled at. 5167933bfe4dSTobias Jakobi 51682ddc8e2dSFilip Alac usbhid.kbpoll= 51692ddc8e2dSFilip Alac [USBHID] The interval which keyboards are to be polled at. 51702ddc8e2dSFilip Alac 5171e52347bdSJani Nikula usb-storage.delay_use= 5172e52347bdSJani Nikula [UMS] The delay in seconds before a new device is 5173e52347bdSJani Nikula scanned for Logical Units (default 1). 5174e52347bdSJani Nikula 5175e52347bdSJani Nikula usb-storage.quirks= 5176e52347bdSJani Nikula [UMS] A list of quirks entries to supplement or 5177e52347bdSJani Nikula override the built-in unusual_devs list. List 5178e52347bdSJani Nikula entries are separated by commas. Each entry has 5179e52347bdSJani Nikula the form VID:PID:Flags where VID and PID are Vendor 5180e52347bdSJani Nikula and Product ID values (4-digit hex numbers) and 5181e52347bdSJani Nikula Flags is a set of characters, each corresponding 5182e52347bdSJani Nikula to a common usb-storage quirk flag as follows: 5183e52347bdSJani Nikula a = SANE_SENSE (collect more than 18 bytes 518465cc8bf9SOliver Neukum of sense data, not on uas); 5185e52347bdSJani Nikula b = BAD_SENSE (don't collect more than 18 518665cc8bf9SOliver Neukum bytes of sense data, not on uas); 5187e52347bdSJani Nikula c = FIX_CAPACITY (decrease the reported 5188e52347bdSJani Nikula device capacity by one sector); 5189e52347bdSJani Nikula d = NO_READ_DISC_INFO (don't use 519065cc8bf9SOliver Neukum READ_DISC_INFO command, not on uas); 5191e52347bdSJani Nikula e = NO_READ_CAPACITY_16 (don't use 5192e52347bdSJani Nikula READ_CAPACITY_16 command); 5193e52347bdSJani Nikula f = NO_REPORT_OPCODES (don't use report opcodes 5194e52347bdSJani Nikula command, uas only); 5195e52347bdSJani Nikula g = MAX_SECTORS_240 (don't transfer more than 5196e52347bdSJani Nikula 240 sectors at a time, uas only); 5197e52347bdSJani Nikula h = CAPACITY_HEURISTICS (decrease the 5198e52347bdSJani Nikula reported device capacity by one 5199e52347bdSJani Nikula sector if the number is odd); 5200e52347bdSJani Nikula i = IGNORE_DEVICE (don't bind to this 5201e52347bdSJani Nikula device); 5202e52347bdSJani Nikula j = NO_REPORT_LUNS (don't use report luns 5203e52347bdSJani Nikula command, uas only); 5204e52347bdSJani Nikula l = NOT_LOCKABLE (don't try to lock and 520565cc8bf9SOliver Neukum unlock ejectable media, not on uas); 5206e52347bdSJani Nikula m = MAX_SECTORS_64 (don't transfer more 520765cc8bf9SOliver Neukum than 64 sectors = 32 KB at a time, 520865cc8bf9SOliver Neukum not on uas); 5209e52347bdSJani Nikula n = INITIAL_READ10 (force a retry of the 521065cc8bf9SOliver Neukum initial READ(10) command, not on uas); 5211e52347bdSJani Nikula o = CAPACITY_OK (accept the capacity 521265cc8bf9SOliver Neukum reported by the device, not on uas); 5213e52347bdSJani Nikula p = WRITE_CACHE (the device cache is ON 521465cc8bf9SOliver Neukum by default, not on uas); 5215e52347bdSJani Nikula r = IGNORE_RESIDUE (the device reports 521665cc8bf9SOliver Neukum bogus residue values, not on uas); 5217e52347bdSJani Nikula s = SINGLE_LUN (the device has only one 5218e52347bdSJani Nikula Logical Unit); 5219e52347bdSJani Nikula t = NO_ATA_1X (don't allow ATA(12) and ATA(16) 5220e52347bdSJani Nikula commands, uas only); 5221e52347bdSJani Nikula u = IGNORE_UAS (don't bind to the uas driver); 5222e52347bdSJani Nikula w = NO_WP_DETECT (don't test whether the 5223e52347bdSJani Nikula medium is write-protected). 5224e52347bdSJani Nikula y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE 522565cc8bf9SOliver Neukum even if the device claims no cache, 522665cc8bf9SOliver Neukum not on uas) 5227e52347bdSJani Nikula Example: quirks=0419:aaf5:rl,0421:0433:rc 5228e52347bdSJani Nikula 5229e52347bdSJani Nikula user_debug= [KNL,ARM] 5230e52347bdSJani Nikula Format: <int> 5231e52347bdSJani Nikula See arch/arm/Kconfig.debug help text. 5232e52347bdSJani Nikula 1 - undefined instruction events 5233e52347bdSJani Nikula 2 - system calls 5234e52347bdSJani Nikula 4 - invalid data aborts 5235e52347bdSJani Nikula 8 - SIGSEGV faults 5236e52347bdSJani Nikula 16 - SIGBUS faults 5237e52347bdSJani Nikula Example: user_debug=31 5238e52347bdSJani Nikula 5239e52347bdSJani Nikula userpte= 5240e52347bdSJani Nikula [X86] Flags controlling user PTE allocations. 5241e52347bdSJani Nikula 5242e52347bdSJani Nikula nohigh = do not allocate PTE pages in 5243e52347bdSJani Nikula HIGHMEM regardless of setting 5244e52347bdSJani Nikula of CONFIG_HIGHPTE. 5245e52347bdSJani Nikula 5246e52347bdSJani Nikula vdso= [X86,SH] 5247e52347bdSJani Nikula On X86_32, this is an alias for vdso32=. Otherwise: 5248e52347bdSJani Nikula 5249e52347bdSJani Nikula vdso=1: enable VDSO (the default) 5250e52347bdSJani Nikula vdso=0: disable VDSO mapping 5251e52347bdSJani Nikula 5252e52347bdSJani Nikula vdso32= [X86] Control the 32-bit vDSO 5253e52347bdSJani Nikula vdso32=1: enable 32-bit VDSO 5254e52347bdSJani Nikula vdso32=0 or vdso32=2: disable 32-bit VDSO 5255e52347bdSJani Nikula 5256e52347bdSJani Nikula See the help text for CONFIG_COMPAT_VDSO for more 5257e52347bdSJani Nikula details. If CONFIG_COMPAT_VDSO is set, the default is 5258e52347bdSJani Nikula vdso32=0; otherwise, the default is vdso32=1. 5259e52347bdSJani Nikula 5260e52347bdSJani Nikula For compatibility with older kernels, vdso32=2 is an 5261e52347bdSJani Nikula alias for vdso32=0. 5262e52347bdSJani Nikula 5263e52347bdSJani Nikula Try vdso32=0 if you encounter an error that says: 5264e52347bdSJani Nikula dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! 5265e52347bdSJani Nikula 5266e52347bdSJani Nikula vector= [IA-64,SMP] 5267e52347bdSJani Nikula vector=percpu: enable percpu vector domain 5268e52347bdSJani Nikula 5269e52347bdSJani Nikula video= [FB] Frame buffer configuration 5270ab42b818SMauro Carvalho Chehab See Documentation/fb/modedb.rst. 5271e52347bdSJani Nikula 5272e52347bdSJani Nikula video.brightness_switch_enabled= [0,1] 5273e52347bdSJani Nikula If set to 1, on receiving an ACPI notify event 5274e52347bdSJani Nikula generated by hotkey, video driver will adjust brightness 5275e52347bdSJani Nikula level and then send out the event to user space through 5276e52347bdSJani Nikula the allocated input device; If set to 0, video driver 5277e52347bdSJani Nikula will only send out the event without touching backlight 5278e52347bdSJani Nikula brightness level. 5279e52347bdSJani Nikula default: 1 5280e52347bdSJani Nikula 5281e52347bdSJani Nikula virtio_mmio.device= 5282e52347bdSJani Nikula [VMMIO] Memory mapped virtio (platform) device. 5283e52347bdSJani Nikula 5284e52347bdSJani Nikula <size>@<baseaddr>:<irq>[:<id>] 5285e52347bdSJani Nikula where: 5286e52347bdSJani Nikula <size> := size (can use standard suffixes 5287e52347bdSJani Nikula like K, M and G) 5288e52347bdSJani Nikula <baseaddr> := physical base address 5289e52347bdSJani Nikula <irq> := interrupt number (as passed to 5290e52347bdSJani Nikula request_irq()) 5291e52347bdSJani Nikula <id> := (optional) platform device id 5292e52347bdSJani Nikula example: 5293e52347bdSJani Nikula virtio_mmio.device=1K@0x100b0000:48:7 5294e52347bdSJani Nikula 5295e52347bdSJani Nikula Can be used multiple times for multiple devices. 5296e52347bdSJani Nikula 5297e52347bdSJani Nikula vga= [BOOT,X86-32] Select a particular video mode 5298cb1aaebeSMauro Carvalho Chehab See Documentation/x86/boot.rst and 52994f4cfa6cSMauro Carvalho Chehab Documentation/admin-guide/svga.rst. 5300e52347bdSJani Nikula Use vga=ask for menu. 5301e52347bdSJani Nikula This is actually a boot loader parameter; the value is 5302e52347bdSJani Nikula passed to the kernel using a special protocol. 5303e52347bdSJani Nikula 5304f682a97aSAlexander Duyck vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y. 5305f682a97aSAlexander Duyck May slow down system boot speed, especially when 5306f682a97aSAlexander Duyck enabled on systems with a large amount of memory. 5307f682a97aSAlexander Duyck All options are enabled by default, and this 5308f682a97aSAlexander Duyck interface is meant to allow for selectively 5309f682a97aSAlexander Duyck enabling or disabling specific virtual memory 5310f682a97aSAlexander Duyck debugging features. 5311f682a97aSAlexander Duyck 5312f682a97aSAlexander Duyck Available options are: 5313f682a97aSAlexander Duyck P Enable page structure init time poisoning 5314f682a97aSAlexander Duyck - Disable all of the above options 5315f682a97aSAlexander Duyck 5316e52347bdSJani Nikula vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 5317e52347bdSJani Nikula size of <nn>. This can be used to increase the 5318e52347bdSJani Nikula minimum size (128MB on x86). It can also be used to 5319e52347bdSJani Nikula decrease the size and leave more room for directly 5320e52347bdSJani Nikula mapped kernel RAM. 5321e52347bdSJani Nikula 53223f429842SHeiko Carstens vmcp_cma=nn[MG] [KNL,S390] 53233f429842SHeiko Carstens Sets the memory size reserved for contiguous memory 53243f429842SHeiko Carstens allocations for the vmcp device driver. 53253f429842SHeiko Carstens 5326e52347bdSJani Nikula vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 5327e52347bdSJani Nikula Format: <command> 5328e52347bdSJani Nikula 5329e52347bdSJani Nikula vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 5330e52347bdSJani Nikula Format: <command> 5331e52347bdSJani Nikula 5332e52347bdSJani Nikula vmpoff= [KNL,S390] Perform z/VM CP command after power off. 5333e52347bdSJani Nikula Format: <command> 5334e52347bdSJani Nikula 5335e52347bdSJani Nikula vsyscall= [X86-64] 5336e52347bdSJani Nikula Controls the behavior of vsyscalls (i.e. calls to 5337e52347bdSJani Nikula fixed addresses of 0xffffffffff600x00 from legacy 5338e52347bdSJani Nikula code). Most statically-linked binaries and older 5339e52347bdSJani Nikula versions of glibc use these calls. Because these 5340e52347bdSJani Nikula functions are at fixed addresses, they make nice 5341e52347bdSJani Nikula targets for exploits that can control RIP. 5342e52347bdSJani Nikula 5343e52347bdSJani Nikula emulate [default] Vsyscalls turn into traps and are 5344bd49e16eSAndy Lutomirski emulated reasonably safely. The vsyscall 5345bd49e16eSAndy Lutomirski page is readable. 5346e52347bdSJani Nikula 5347bd49e16eSAndy Lutomirski xonly Vsyscalls turn into traps and are 5348bd49e16eSAndy Lutomirski emulated reasonably safely. The vsyscall 5349bd49e16eSAndy Lutomirski page is not readable. 5350e52347bdSJani Nikula 5351e52347bdSJani Nikula none Vsyscalls don't work at all. This makes 5352e52347bdSJani Nikula them quite hard to use for exploits but 5353e52347bdSJani Nikula might break your system. 5354e52347bdSJani Nikula 5355e52347bdSJani Nikula vt.color= [VT] Default text color. 5356e52347bdSJani Nikula Format: 0xYX, X = foreground, Y = background. 5357e52347bdSJani Nikula Default: 0x07 = light gray on black. 5358e52347bdSJani Nikula 5359e52347bdSJani Nikula vt.cur_default= [VT] Default cursor shape. 5360e52347bdSJani Nikula Format: 0xCCBBAA, where AA, BB, and CC are the same as 5361e52347bdSJani Nikula the parameters of the <Esc>[?A;B;Cc escape sequence; 5362e52347bdSJani Nikula see VGA-softcursor.txt. Default: 2 = underline. 5363e52347bdSJani Nikula 5364e52347bdSJani Nikula vt.default_blu= [VT] 5365e52347bdSJani Nikula Format: <blue0>,<blue1>,<blue2>,...,<blue15> 5366e52347bdSJani Nikula Change the default blue palette of the console. 5367e52347bdSJani Nikula This is a 16-member array composed of values 5368e52347bdSJani Nikula ranging from 0-255. 5369e52347bdSJani Nikula 5370e52347bdSJani Nikula vt.default_grn= [VT] 5371e52347bdSJani Nikula Format: <green0>,<green1>,<green2>,...,<green15> 5372e52347bdSJani Nikula Change the default green palette of the console. 5373e52347bdSJani Nikula This is a 16-member array composed of values 5374e52347bdSJani Nikula ranging from 0-255. 5375e52347bdSJani Nikula 5376e52347bdSJani Nikula vt.default_red= [VT] 5377e52347bdSJani Nikula Format: <red0>,<red1>,<red2>,...,<red15> 5378e52347bdSJani Nikula Change the default red palette of the console. 5379e52347bdSJani Nikula This is a 16-member array composed of values 5380e52347bdSJani Nikula ranging from 0-255. 5381e52347bdSJani Nikula 5382e52347bdSJani Nikula vt.default_utf8= 5383e52347bdSJani Nikula [VT] 5384e52347bdSJani Nikula Format=<0|1> 5385e52347bdSJani Nikula Set system-wide default UTF-8 mode for all tty's. 5386e52347bdSJani Nikula Default is 1, i.e. UTF-8 mode is enabled for all 5387e52347bdSJani Nikula newly opened terminals. 5388e52347bdSJani Nikula 5389e52347bdSJani Nikula vt.global_cursor_default= 5390e52347bdSJani Nikula [VT] 5391e52347bdSJani Nikula Format=<-1|0|1> 5392e52347bdSJani Nikula Set system-wide default for whether a cursor 5393e52347bdSJani Nikula is shown on new VTs. Default is -1, 5394e52347bdSJani Nikula i.e. cursors will be created by default unless 5395e52347bdSJani Nikula overridden by individual drivers. 0 will hide 5396e52347bdSJani Nikula cursors, 1 will display them. 5397e52347bdSJani Nikula 5398e52347bdSJani Nikula vt.italic= [VT] Default color for italic text; 0-15. 5399e52347bdSJani Nikula Default: 2 = green. 5400e52347bdSJani Nikula 5401e52347bdSJani Nikula vt.underline= [VT] Default color for underlined text; 0-15. 5402e52347bdSJani Nikula Default: 3 = cyan. 5403e52347bdSJani Nikula 5404e52347bdSJani Nikula watchdog timers [HW,WDT] For information on watchdog timers, 5405cc2a2d19SMauro Carvalho Chehab see Documentation/watchdog/watchdog-parameters.rst 5406e52347bdSJani Nikula or other driver-specific files in the 5407e52347bdSJani Nikula Documentation/watchdog/ directory. 5408e52347bdSJani Nikula 540911295055SLaurence Oberman watchdog_thresh= 541011295055SLaurence Oberman [KNL] 541111295055SLaurence Oberman Set the hard lockup detector stall duration 541211295055SLaurence Oberman threshold in seconds. The soft lockup detector 541311295055SLaurence Oberman threshold is set to twice the value. A value of 0 541411295055SLaurence Oberman disables both lockup detectors. Default is 10 541511295055SLaurence Oberman seconds. 541611295055SLaurence Oberman 5417e52347bdSJani Nikula workqueue.watchdog_thresh= 5418e52347bdSJani Nikula If CONFIG_WQ_WATCHDOG is configured, workqueue can 5419e52347bdSJani Nikula warn stall conditions and dump internal state to 5420e52347bdSJani Nikula help debugging. 0 disables workqueue stall 5421e52347bdSJani Nikula detection; otherwise, it's the stall threshold 5422e52347bdSJani Nikula duration in seconds. The default value is 30 and 5423e52347bdSJani Nikula it can be updated at runtime by writing to the 5424e52347bdSJani Nikula corresponding sysfs file. 5425e52347bdSJani Nikula 5426e52347bdSJani Nikula workqueue.disable_numa 5427e52347bdSJani Nikula By default, all work items queued to unbound 5428e52347bdSJani Nikula workqueues are affine to the NUMA nodes they're 5429e52347bdSJani Nikula issued on, which results in better behavior in 5430e52347bdSJani Nikula general. If NUMA affinity needs to be disabled for 5431e52347bdSJani Nikula whatever reason, this option can be used. Note 5432e52347bdSJani Nikula that this also can be controlled per-workqueue for 5433e52347bdSJani Nikula workqueues visible under /sys/bus/workqueue/. 5434e52347bdSJani Nikula 5435e52347bdSJani Nikula workqueue.power_efficient 5436e52347bdSJani Nikula Per-cpu workqueues are generally preferred because 5437e52347bdSJani Nikula they show better performance thanks to cache 5438e52347bdSJani Nikula locality; unfortunately, per-cpu workqueues tend to 5439e52347bdSJani Nikula be more power hungry than unbound workqueues. 5440e52347bdSJani Nikula 5441e52347bdSJani Nikula Enabling this makes the per-cpu workqueues which 5442e52347bdSJani Nikula were observed to contribute significantly to power 5443e52347bdSJani Nikula consumption unbound, leading to measurably lower 5444e52347bdSJani Nikula power usage at the cost of small performance 5445e52347bdSJani Nikula overhead. 5446e52347bdSJani Nikula 5447e52347bdSJani Nikula The default value of this parameter is determined by 5448e52347bdSJani Nikula the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. 5449e52347bdSJani Nikula 5450e52347bdSJani Nikula workqueue.debug_force_rr_cpu 5451e52347bdSJani Nikula Workqueue used to implicitly guarantee that work 5452e52347bdSJani Nikula items queued without explicit CPU specified are put 5453e52347bdSJani Nikula on the local CPU. This guarantee is no longer true 5454e52347bdSJani Nikula and while local CPU is still preferred work items 5455e52347bdSJani Nikula may be put on foreign CPUs. This debug option 5456e52347bdSJani Nikula forces round-robin CPU selection to flush out 5457e52347bdSJani Nikula usages which depend on the now broken guarantee. 5458e52347bdSJani Nikula When enabled, memory and cache locality will be 5459e52347bdSJani Nikula impacted. 5460e52347bdSJani Nikula 5461e52347bdSJani Nikula x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 5462e52347bdSJani Nikula default x2apic cluster mode on platforms 5463e52347bdSJani Nikula supporting x2apic. 5464e52347bdSJani Nikula 5465e52347bdSJani Nikula x86_intel_mid_timer= [X86-32,APBT] 5466e52347bdSJani Nikula Choose timer option for x86 Intel MID platform. 5467e52347bdSJani Nikula Two valid options are apbt timer only and lapic timer 5468e52347bdSJani Nikula plus one apbt timer for broadcast timer. 5469e52347bdSJani Nikula x86_intel_mid_timer=apbt_only | lapic_and_apbt 5470e52347bdSJani Nikula 5471e52347bdSJani Nikula xen_512gb_limit [KNL,X86-64,XEN] 5472e52347bdSJani Nikula Restricts the kernel running paravirtualized under Xen 5473e52347bdSJani Nikula to use only up to 512 GB of RAM. The reason to do so is 5474e52347bdSJani Nikula crash analysis tools and Xen tools for doing domain 5475e52347bdSJani Nikula save/restore/migration must be enabled to handle larger 5476e52347bdSJani Nikula domains. 5477e52347bdSJani Nikula 5478e52347bdSJani Nikula xen_emul_unplug= [HW,X86,XEN] 5479e52347bdSJani Nikula Unplug Xen emulated devices 5480e52347bdSJani Nikula Format: [unplug0,][unplug1] 5481e52347bdSJani Nikula ide-disks -- unplug primary master IDE devices 5482e52347bdSJani Nikula aux-ide-disks -- unplug non-primary-master IDE devices 5483e52347bdSJani Nikula nics -- unplug network devices 5484e52347bdSJani Nikula all -- unplug all emulated devices (NICs and IDE disks) 5485e52347bdSJani Nikula unnecessary -- unplugging emulated devices is 5486e52347bdSJani Nikula unnecessary even if the host did not respond to 5487e52347bdSJani Nikula the unplug protocol 5488e52347bdSJani Nikula never -- do not unplug even if version check succeeds 5489e52347bdSJani Nikula 5490c6875f3aSBoris Ostrovsky xen_legacy_crash [X86,XEN] 5491c6875f3aSBoris Ostrovsky Crash from Xen panic notifier, without executing late 5492c6875f3aSBoris Ostrovsky panic() code such as dumping handler. 5493c6875f3aSBoris Ostrovsky 5494e52347bdSJani Nikula xen_nopvspin [X86,XEN] 5495e52347bdSJani Nikula Disables the ticketlock slowpath using Xen PV 5496e52347bdSJani Nikula optimizations. 5497e52347bdSJani Nikula 5498e52347bdSJani Nikula xen_nopv [X86] 5499e52347bdSJani Nikula Disables the PV optimizations forcing the HVM guest to 5500e52347bdSJani Nikula run as generic HVM guest with no PV drivers. 5501b39b0497SZhenzhong Duan This option is obsoleted by the "nopv" option, which 5502b39b0497SZhenzhong Duan has equivalent effect for XEN platform. 5503e52347bdSJani Nikula 5504197ecb38SMarek Marczykowski-Górecki xen_scrub_pages= [XEN] 5505197ecb38SMarek Marczykowski-Górecki Boolean option to control scrubbing pages before giving them back 5506197ecb38SMarek Marczykowski-Górecki to Xen, for use by other domains. Can be also changed at runtime 5507197ecb38SMarek Marczykowski-Górecki with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. 5508197ecb38SMarek Marczykowski-Górecki Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. 5509197ecb38SMarek Marczykowski-Górecki 55102ec16bc0SRyan Thibodeaux xen_timer_slop= [X86-64,XEN] 55112ec16bc0SRyan Thibodeaux Set the timer slop (in nanoseconds) for the virtual Xen 55122ec16bc0SRyan Thibodeaux timers (default is 100000). This adjusts the minimum 55132ec16bc0SRyan Thibodeaux delta of virtualized Xen timers, where lower values 55142ec16bc0SRyan Thibodeaux improve timer resolution at the expense of processing 55152ec16bc0SRyan Thibodeaux more timer interrupts. 55162ec16bc0SRyan Thibodeaux 551730978346SZhenzhong Duan nopv= [X86,XEN,KVM,HYPER_V,VMWARE] 551830978346SZhenzhong Duan Disables the PV optimizations forcing the guest to run 551930978346SZhenzhong Duan as generic guest with no PV drivers. Currently support 552030978346SZhenzhong Duan XEN HVM, KVM, HYPER_V and VMWARE guest. 552130978346SZhenzhong Duan 5522e52347bdSJani Nikula xirc2ps_cs= [NET,PCMCIA] 5523e52347bdSJani Nikula Format: 5524e52347bdSJani Nikula <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 5525c0addc9aSLaurentiu Tudor 5526ba45cff6SMichael Neuling xive= [PPC] 5527ba45cff6SMichael Neuling By default on POWER9 and above, the kernel will 5528ba45cff6SMichael Neuling natively use the XIVE interrupt controller. This option 5529ba45cff6SMichael Neuling allows the fallback firmware mode to be used: 5530ba45cff6SMichael Neuling 5531ba45cff6SMichael Neuling off Fallback to firmware control of XIVE interrupt 5532ba45cff6SMichael Neuling controller on both pseries and powernv 5533ba45cff6SMichael Neuling platforms. Only useful on POWER9 and above. 5534ba45cff6SMichael Neuling 5535c0addc9aSLaurentiu Tudor xhci-hcd.quirks [USB,KNL] 5536c0addc9aSLaurentiu Tudor A hex value specifying bitmask with supplemental xhci 5537c0addc9aSLaurentiu Tudor host controller quirks. Meaning of each bit can be 5538c0addc9aSLaurentiu Tudor consulted in header drivers/usb/host/xhci.h. 55396278f55bSGustavo Romero 55406278f55bSGustavo Romero xmon [PPC] 55416278f55bSGustavo Romero Format: { early | on | rw | ro | off } 55426278f55bSGustavo Romero Controls if xmon debugger is enabled. Default is off. 55436278f55bSGustavo Romero Passing only "xmon" is equivalent to "xmon=early". 55446278f55bSGustavo Romero early Call xmon as early as possible on boot; xmon 55456278f55bSGustavo Romero debugger is called from setup_arch(). 55466278f55bSGustavo Romero on xmon debugger hooks will be installed so xmon 55476278f55bSGustavo Romero is only called on a kernel crash. Default mode, 55486278f55bSGustavo Romero i.e. either "ro" or "rw" mode, is controlled 55496278f55bSGustavo Romero with CONFIG_XMON_DEFAULT_RO_MODE. 55506278f55bSGustavo Romero rw xmon debugger hooks will be installed so xmon 55516278f55bSGustavo Romero is called only on a kernel crash, mode is write, 55526278f55bSGustavo Romero meaning SPR registers, memory and, other data 55536278f55bSGustavo Romero can be written using xmon commands. 55546278f55bSGustavo Romero ro same as "rw" option above but SPR registers, 55556278f55bSGustavo Romero memory, and other data can't be written using 55566278f55bSGustavo Romero xmon commands. 55576278f55bSGustavo Romero off xmon is disabled. 5558