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 16e52347bdSJani Nikula See also Documentation/power/runtime_pm.txt, 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 56e52347bdSJani Nikula Documentation/acpi/debug.txt 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. 1169c4aa1eeSLv Zheng Format: <int> 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 } 226e52347bdSJani Nikula See Documentation/power/video.txt 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. 433e52347bdSJani Nikula See Documentation/block/cmdline-partition.txt 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 440e52347bdSJani Nikula bootmem_debug [KNL] Enable bootmem allocator debug messages. 441e52347bdSJani Nikula 442e52347bdSJani Nikula bert_disable [ACPI] 443e52347bdSJani Nikula Disable BERT OS support on buggy BIOSes. 444e52347bdSJani Nikula 445e52347bdSJani Nikula bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 446e52347bdSJani Nikula bttv.radio= Most important insmod options are available as 447e52347bdSJani Nikula kernel args too. 448a405ed85STom Saeger bttv.pll= See Documentation/media/v4l-drivers/bttv.rst 449e52347bdSJani Nikula bttv.tuner= 450e52347bdSJani Nikula 451e52347bdSJani Nikula bulk_remove=off [PPC] This parameter disables the use of the pSeries 452e52347bdSJani Nikula firmware feature for flushing multiple hpte entries 453e52347bdSJani Nikula at a time. 454e52347bdSJani Nikula 455e52347bdSJani Nikula c101= [NET] Moxa C101 synchronous serial card 456e52347bdSJani Nikula 457e52347bdSJani Nikula cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 458e52347bdSJani Nikula Sometimes CPU hardware bugs make them report the cache 459e52347bdSJani Nikula size incorrectly. The kernel will attempt work arounds 460e52347bdSJani Nikula to fix known problems, but for some CPUs it is not 461e52347bdSJani Nikula possible to determine what the correct size should be. 462e52347bdSJani Nikula This option provides an override for these situations. 463e52347bdSJani Nikula 464e52347bdSJani Nikula ca_keys= [KEYS] This parameter identifies a specific key(s) on 465e52347bdSJani Nikula the system trusted keyring to be used for certificate 466e52347bdSJani Nikula trust validation. 467e52347bdSJani Nikula format: { id:<keyid> | builtin } 468e52347bdSJani Nikula 469e52347bdSJani Nikula cca= [MIPS] Override the kernel pages' cache coherency 470e52347bdSJani Nikula algorithm. Accepted values range from 0 to 7 471e52347bdSJani Nikula inclusive. See arch/mips/include/asm/pgtable-bits.h 472e52347bdSJani Nikula for platform specific values (SB1, Loongson3 and 473e52347bdSJani Nikula others). 474e52347bdSJani Nikula 475e52347bdSJani Nikula ccw_timeout_log [S390] 476e52347bdSJani Nikula See Documentation/s390/CommonIO for details. 477e52347bdSJani Nikula 478e52347bdSJani Nikula cgroup_disable= [KNL] Disable a particular controller 479e52347bdSJani Nikula Format: {name of the controller(s) to disable} 480e52347bdSJani Nikula The effects of cgroup_disable=foo are: 481e52347bdSJani Nikula - foo isn't auto-mounted if you mount all cgroups in 482e52347bdSJani Nikula a single hierarchy 483e52347bdSJani Nikula - foo isn't visible as an individually mountable 484e52347bdSJani Nikula subsystem 485e52347bdSJani Nikula {Currently only "memory" controller deal with this and 486e52347bdSJani Nikula cut the overhead, others just disable the usage. So 487e52347bdSJani Nikula only cgroup_disable=memory is actually worthy} 488e52347bdSJani Nikula 4893fc9c12dSTejun Heo cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1 4903fc9c12dSTejun Heo Format: { { controller | "all" | "named" } 4913fc9c12dSTejun Heo [,{ controller | "all" | "named" }...] } 492e52347bdSJani Nikula Like cgroup_disable, but only applies to cgroup v1; 493e52347bdSJani Nikula the blacklisted controllers remain available in cgroup2. 4943fc9c12dSTejun Heo "all" blacklists all controllers and "named" disables 4953fc9c12dSTejun Heo named mounts. Specifying both "all" and "named" disables 4963fc9c12dSTejun Heo all v1 hierarchies. 497e52347bdSJani Nikula 498e52347bdSJani Nikula cgroup.memory= [KNL] Pass options to the cgroup memory controller. 499e52347bdSJani Nikula Format: <string> 500e52347bdSJani Nikula nosocket -- Disable socket memory accounting. 501e52347bdSJani Nikula nokmem -- Disable kernel memory accounting. 502e52347bdSJani Nikula 503e52347bdSJani Nikula checkreqprot [SELINUX] Set initial checkreqprot flag value. 504e52347bdSJani Nikula Format: { "0" | "1" } 505e52347bdSJani Nikula See security/selinux/Kconfig help text. 506e52347bdSJani Nikula 0 -- check protection applied by kernel (includes 507e52347bdSJani Nikula any implied execute protection). 508e52347bdSJani Nikula 1 -- check protection requested by application. 509e52347bdSJani Nikula Default value is set via a kernel config option. 510e52347bdSJani Nikula Value can be changed at runtime via 511e52347bdSJani Nikula /selinux/checkreqprot. 512e52347bdSJani Nikula 513e52347bdSJani Nikula cio_ignore= [S390] 514e52347bdSJani Nikula See Documentation/s390/CommonIO for details. 515e52347bdSJani Nikula clk_ignore_unused 516e52347bdSJani Nikula [CLK] 517e52347bdSJani Nikula Prevents the clock framework from automatically gating 518e52347bdSJani Nikula clocks that have not been explicitly enabled by a Linux 519e52347bdSJani Nikula device driver but are enabled in hardware at reset or 520e52347bdSJani Nikula by the bootloader/firmware. Note that this does not 521e52347bdSJani Nikula force such clocks to be always-on nor does it reserve 522e52347bdSJani Nikula those clocks in any way. This parameter is useful for 523e52347bdSJani Nikula debug and development, but should not be needed on a 524e52347bdSJani Nikula platform with proper driver support. For more 52518bcaa4eSMauro Carvalho Chehab information, see Documentation/driver-api/clk.rst. 526e52347bdSJani Nikula 527e52347bdSJani Nikula clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 528e52347bdSJani Nikula [Deprecated] 529e52347bdSJani Nikula Forces specified clocksource (if available) to be used 530e52347bdSJani Nikula when calculating gettimeofday(). If specified 531e52347bdSJani Nikula clocksource is not available, it defaults to PIT. 532e52347bdSJani Nikula Format: { pit | tsc | cyclone | pmtmr } 533e52347bdSJani Nikula 534e52347bdSJani Nikula clocksource= Override the default clocksource 535e52347bdSJani Nikula Format: <string> 536e52347bdSJani Nikula Override the default clocksource and use the clocksource 537e52347bdSJani Nikula with the name specified. 538e52347bdSJani Nikula Some clocksource names to choose from, depending on 539e52347bdSJani Nikula the platform: 540e52347bdSJani Nikula [all] jiffies (this is the base, fallback clocksource) 541e52347bdSJani Nikula [ACPI] acpi_pm 542e52347bdSJani Nikula [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 543e52347bdSJani Nikula pxa_timer,timer3,32k_counter,timer0_1 544e52347bdSJani Nikula [X86-32] pit,hpet,tsc; 545e52347bdSJani Nikula scx200_hrt on Geode; cyclone on IBM x440 546e52347bdSJani Nikula [MIPS] MIPS 547e52347bdSJani Nikula [PARISC] cr16 548e52347bdSJani Nikula [S390] tod 549e52347bdSJani Nikula [SH] SuperH 550e52347bdSJani Nikula [SPARC64] tick 551e52347bdSJani Nikula [X86-64] hpet,tsc 552e52347bdSJani Nikula 553e52347bdSJani Nikula clocksource.arm_arch_timer.evtstrm= 554e52347bdSJani Nikula [ARM,ARM64] 555e52347bdSJani Nikula Format: <bool> 556e52347bdSJani Nikula Enable/disable the eventstream feature of the ARM 557e52347bdSJani Nikula architected timer so that code using WFE-based polling 558e52347bdSJani Nikula loops can be debugged more effectively on production 559e52347bdSJani Nikula systems. 560e52347bdSJani Nikula 561e52347bdSJani Nikula clearcpuid=BITNUM [X86] 562e52347bdSJani Nikula Disable CPUID feature X for the kernel. See 563e52347bdSJani Nikula arch/x86/include/asm/cpufeatures.h for the valid bit 564e52347bdSJani Nikula numbers. Note the Linux specific bits are not necessarily 565e52347bdSJani Nikula stable over kernel options, but the vendor specific 566e52347bdSJani Nikula ones should be. 567e52347bdSJani Nikula Also note that user programs calling CPUID directly 568e52347bdSJani Nikula or using the feature without checking anything 569e52347bdSJani Nikula will still see it. This just prevents it from 570e52347bdSJani Nikula being used by the kernel or shown in /proc/cpuinfo. 571e52347bdSJani Nikula Also note the kernel might malfunction if you disable 572e52347bdSJani Nikula some critical bits. 573e52347bdSJani Nikula 574e52347bdSJani Nikula cma=nn[MG]@[start[MG][-end[MG]]] 575e52347bdSJani Nikula [ARM,X86,KNL] 576e52347bdSJani Nikula Sets the size of kernel global memory area for 577e52347bdSJani Nikula contiguous memory allocations and optionally the 578e52347bdSJani Nikula placement constraint by the physical address range of 579e52347bdSJani Nikula memory allocations. A value of 0 disables CMA 580e52347bdSJani Nikula altogether. For more information, see 581e52347bdSJani Nikula include/linux/dma-contiguous.h 582e52347bdSJani Nikula 583e52347bdSJani Nikula cmo_free_hint= [PPC] Format: { yes | no } 584e52347bdSJani Nikula Specify whether pages are marked as being inactive 585e52347bdSJani Nikula when they are freed. This is used in CMO environments 586e52347bdSJani Nikula to determine OS memory pressure for page stealing by 587e52347bdSJani Nikula a hypervisor. 588e52347bdSJani Nikula Default: yes 589e52347bdSJani Nikula 590e52347bdSJani Nikula coherent_pool=nn[KMG] [ARM,KNL] 591e52347bdSJani Nikula Sets the size of memory pool for coherent, atomic dma 592e52347bdSJani Nikula allocations, by default set to 256K. 593e52347bdSJani Nikula 594e52347bdSJani Nikula com20020= [HW,NET] ARCnet - COM20020 chipset 595e52347bdSJani Nikula Format: 596e52347bdSJani Nikula <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 597e52347bdSJani Nikula 598e52347bdSJani Nikula com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 599e52347bdSJani Nikula Format: <io>[,<irq>] 600e52347bdSJani Nikula 601e52347bdSJani Nikula com90xx= [HW,NET] 602e52347bdSJani Nikula ARCnet - COM90xx chipset (memory-mapped buffers) 603e52347bdSJani Nikula Format: <io>[,<irq>[,<memstart>]] 604e52347bdSJani Nikula 605e52347bdSJani Nikula condev= [HW,S390] console device 606e52347bdSJani Nikula conmode= 607e52347bdSJani Nikula 608e52347bdSJani Nikula console= [KNL] Output console device and options. 609e52347bdSJani Nikula 610e52347bdSJani Nikula tty<n> Use the virtual console device <n>. 611e52347bdSJani Nikula 612e52347bdSJani Nikula ttyS<n>[,options] 613e52347bdSJani Nikula ttyUSB0[,options] 614e52347bdSJani Nikula Use the specified serial port. The options are of 615e52347bdSJani Nikula the form "bbbbpnf", where "bbbb" is the baud rate, 616e52347bdSJani Nikula "p" is parity ("n", "o", or "e"), "n" is number of 617e52347bdSJani Nikula bits, and "f" is flow control ("r" for RTS or 618e52347bdSJani Nikula omit it). Default is "9600n8". 619e52347bdSJani Nikula 620e52347bdSJani Nikula See Documentation/admin-guide/serial-console.rst for more 621e52347bdSJani Nikula information. See 622e52347bdSJani Nikula Documentation/networking/netconsole.txt for an 623e52347bdSJani Nikula alternative. 624e52347bdSJani Nikula 625e52347bdSJani Nikula uart[8250],io,<addr>[,options] 626e52347bdSJani Nikula uart[8250],mmio,<addr>[,options] 627e52347bdSJani Nikula uart[8250],mmio16,<addr>[,options] 628e52347bdSJani Nikula uart[8250],mmio32,<addr>[,options] 629e52347bdSJani Nikula uart[8250],0x<addr>[,options] 630e52347bdSJani Nikula Start an early, polled-mode console on the 8250/16550 631e52347bdSJani Nikula UART at the specified I/O port or MMIO address, 632e52347bdSJani Nikula switching to the matching ttyS device later. 633e52347bdSJani Nikula MMIO inter-register address stride is either 8-bit 634e52347bdSJani Nikula (mmio), 16-bit (mmio16), or 32-bit (mmio32). 635e52347bdSJani Nikula If none of [io|mmio|mmio16|mmio32], <addr> is assumed 636e52347bdSJani Nikula to be equivalent to 'mmio'. 'options' are specified in 637e52347bdSJani Nikula the same format described for ttyS above; if unspecified, 638e52347bdSJani Nikula the h/w is not re-initialized. 639e52347bdSJani Nikula 640e52347bdSJani Nikula hvc<n> Use the hypervisor console device <n>. This is for 641e52347bdSJani Nikula both Xen and PowerPC hypervisors. 642e52347bdSJani Nikula 643e52347bdSJani Nikula If the device connected to the port is not a TTY but a braille 644e52347bdSJani Nikula device, prepend "brl," before the device type, for instance 645e52347bdSJani Nikula console=brl,ttyS0 646e52347bdSJani Nikula For now, only VisioBraille is supported. 647e52347bdSJani Nikula 648cca10d58SSergey Senozhatsky console_msg_format= 649cca10d58SSergey Senozhatsky [KNL] Change console messages format 650cca10d58SSergey Senozhatsky default 651cca10d58SSergey Senozhatsky By default we print messages on consoles in 652cca10d58SSergey Senozhatsky "[time stamp] text\n" format (time stamp may not be 653cca10d58SSergey Senozhatsky printed, depending on CONFIG_PRINTK_TIME or 654cca10d58SSergey Senozhatsky `printk_time' param). 655cca10d58SSergey Senozhatsky syslog 656cca10d58SSergey Senozhatsky Switch to syslog format: "<%u>[time stamp] text\n" 657cca10d58SSergey Senozhatsky IOW, each message will have a facility and loglevel 658cca10d58SSergey Senozhatsky prefix. The format is similar to one used by syslog() 659cca10d58SSergey Senozhatsky syscall, or to executing "dmesg -S --raw" or to reading 660cca10d58SSergey Senozhatsky from /proc/kmsg. 661cca10d58SSergey Senozhatsky 662e52347bdSJani Nikula consoleblank= [KNL] The console blank (screen saver) timeout in 663ac0a314cSDaniel Xu seconds. A value of 0 disables the blank timer. 664ac0a314cSDaniel Xu Defaults to 0. 665e52347bdSJani Nikula 666e52347bdSJani Nikula coredump_filter= 667e52347bdSJani Nikula [KNL] Change the default value for 668e52347bdSJani Nikula /proc/<pid>/coredump_filter. 669e52347bdSJani Nikula See also Documentation/filesystems/proc.txt. 670e52347bdSJani Nikula 67162a31ce1SLeo Yan coresight_cpu_debug.enable 67262a31ce1SLeo Yan [ARM,ARM64] 67362a31ce1SLeo Yan Format: <bool> 67462a31ce1SLeo Yan Enable/disable the CPU sampling based debugging. 67562a31ce1SLeo Yan 0: default value, disable debugging 67662a31ce1SLeo Yan 1: enable debugging at boot time 67762a31ce1SLeo Yan 678e52347bdSJani Nikula cpuidle.off=1 [CPU_IDLE] 679e52347bdSJani Nikula disable the cpuidle sub-system 680e52347bdSJani Nikula 68161cb5758SRafael J. Wysocki cpuidle.governor= 68261cb5758SRafael J. Wysocki [CPU_IDLE] Name of the cpuidle governor to use. 68361cb5758SRafael J. Wysocki 684d82f2692SLen Brown cpufreq.off=1 [CPU_FREQ] 685d82f2692SLen Brown disable the cpufreq sub-system 686d82f2692SLen Brown 687e52347bdSJani Nikula cpu_init_udelay=N 688e52347bdSJani Nikula [X86] Delay for N microsec between assert and de-assert 689e52347bdSJani Nikula of APIC INIT to start processors. This delay occurs 690e52347bdSJani Nikula on every CPU online, such as boot, and resume from suspend. 691e52347bdSJani Nikula Default: 10000 692e52347bdSJani Nikula 693e52347bdSJani Nikula cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 694e52347bdSJani Nikula Format: 695e52347bdSJani Nikula <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 696e52347bdSJani Nikula 697e52347bdSJani Nikula crashkernel=size[KMG][@offset[KMG]] 698e52347bdSJani Nikula [KNL] Using kexec, Linux can switch to a 'crash kernel' 699e52347bdSJani Nikula upon panic. This parameter reserves the physical 700e52347bdSJani Nikula memory region [offset, offset + size] for that kernel 701e52347bdSJani Nikula image. If '@offset' is omitted, then a suitable offset 702e52347bdSJani Nikula is selected automatically. Check 703e52347bdSJani Nikula Documentation/kdump/kdump.txt for further details. 704e52347bdSJani Nikula 705e52347bdSJani Nikula crashkernel=range1:size1[,range2:size2,...][@offset] 706e52347bdSJani Nikula [KNL] Same as above, but depends on the memory 707e52347bdSJani Nikula in the running system. The syntax of range is 708e52347bdSJani Nikula start-[end] where start and end are both 709e52347bdSJani Nikula a memory unit (amount[KMG]). See also 710e52347bdSJani Nikula Documentation/kdump/kdump.txt for an example. 711e52347bdSJani Nikula 712e52347bdSJani Nikula crashkernel=size[KMG],high 713e52347bdSJani Nikula [KNL, x86_64] range could be above 4G. Allow kernel 714e52347bdSJani Nikula to allocate physical memory region from top, so could 715e52347bdSJani Nikula be above 4G if system have more than 4G ram installed. 716e52347bdSJani Nikula Otherwise memory region will be allocated below 4G, if 717e52347bdSJani Nikula available. 718e52347bdSJani Nikula It will be ignored if crashkernel=X is specified. 719e52347bdSJani Nikula crashkernel=size[KMG],low 720e52347bdSJani Nikula [KNL, x86_64] range under 4G. When crashkernel=X,high 721e52347bdSJani Nikula is passed, kernel could allocate physical memory region 722e52347bdSJani Nikula above 4G, that cause second kernel crash on system 723e52347bdSJani Nikula that require some amount of low memory, e.g. swiotlb 724e52347bdSJani Nikula requires at least 64M+32K low memory, also enough extra 725e52347bdSJani Nikula low memory is needed to make sure DMA buffers for 32-bit 726e52347bdSJani Nikula devices won't run out. Kernel would try to allocate at 727e52347bdSJani Nikula at least 256M below 4G automatically. 728e52347bdSJani Nikula This one let user to specify own low range under 4G 729e52347bdSJani Nikula for second kernel instead. 730e52347bdSJani Nikula 0: to disable low allocation. 731e52347bdSJani Nikula It will be ignored when crashkernel=X,high is not used 732e52347bdSJani Nikula or memory reserved is below 4G. 733e52347bdSJani Nikula 734e52347bdSJani Nikula cryptomgr.notests 735e52347bdSJani Nikula [KNL] Disable crypto self-tests 736e52347bdSJani Nikula 737e52347bdSJani Nikula cs89x0_dma= [HW,NET] 738e52347bdSJani Nikula Format: <dma> 739e52347bdSJani Nikula 740e52347bdSJani Nikula cs89x0_media= [HW,NET] 741e52347bdSJani Nikula Format: { rj45 | aui | bnc } 742e52347bdSJani Nikula 743e52347bdSJani Nikula dasd= [HW,NET] 744e52347bdSJani Nikula See header of drivers/s390/block/dasd_devmap.c. 745e52347bdSJani Nikula 746e52347bdSJani Nikula db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 747e52347bdSJani Nikula (one device per port) 748e52347bdSJani Nikula Format: <port#>,<type> 7491752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 750e52347bdSJani Nikula 751e52347bdSJani Nikula ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot 752787e3075SSteffen Maier time. See 753787e3075SSteffen Maier Documentation/admin-guide/dynamic-debug-howto.rst for 754e52347bdSJani Nikula details. Deprecated, see dyndbg. 755e52347bdSJani Nikula 756e52347bdSJani Nikula debug [KNL] Enable kernel debugging (events log level). 757e52347bdSJani Nikula 7583672476eSTobin C. Harding debug_boot_weak_hash 7593672476eSTobin C. Harding [KNL] Enable printing [hashed] pointers early in the 7603672476eSTobin C. Harding boot sequence. If enabled, we use a weak hash instead 7613672476eSTobin C. Harding of siphash to hash pointers. Use this option if you are 7623672476eSTobin C. Harding seeing instances of '(___ptrval___)') and need to see a 7633672476eSTobin C. Harding value (hashed pointer) instead. Cryptographically 7643672476eSTobin C. Harding insecure, please do not use on production kernels. 7653672476eSTobin C. Harding 766e52347bdSJani Nikula debug_locks_verbose= 767e52347bdSJani Nikula [KNL] verbose self-tests 768e52347bdSJani Nikula Format=<0|1> 769e52347bdSJani Nikula Print debugging info while doing the locking API 770e52347bdSJani Nikula self-tests. 771e52347bdSJani Nikula We default to 0 (no extra messages), setting it to 772e52347bdSJani Nikula 1 will print _a lot_ more information - normally 773e52347bdSJani Nikula only useful to kernel developers. 774e52347bdSJani Nikula 775e52347bdSJani Nikula debug_objects [KNL] Enable object debugging 776e52347bdSJani Nikula 777e52347bdSJani Nikula no_debug_objects 778e52347bdSJani Nikula [KNL] Disable object debugging 779e52347bdSJani Nikula 780e52347bdSJani Nikula debug_guardpage_minorder= 781e52347bdSJani Nikula [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this 782e52347bdSJani Nikula parameter allows control of the order of pages that will 783e52347bdSJani Nikula be intentionally kept free (and hence protected) by the 784e52347bdSJani Nikula buddy allocator. Bigger value increase the probability 785e52347bdSJani Nikula of catching random memory corruption, but reduce the 786e52347bdSJani Nikula amount of memory for normal system use. The maximum 787e52347bdSJani Nikula possible value is MAX_ORDER/2. Setting this parameter 788e52347bdSJani Nikula to 1 or 2 should be enough to identify most random 789e52347bdSJani Nikula memory corruption problems caused by bugs in kernel or 790e52347bdSJani Nikula driver code when a CPU writes to (or reads from) a 791e52347bdSJani Nikula random memory location. Note that there exists a class 792e52347bdSJani Nikula of memory corruptions problems caused by buggy H/W or 793e52347bdSJani Nikula F/W or by drivers badly programing DMA (basically when 794e52347bdSJani Nikula memory is written at bus level and the CPU MMU is 795e52347bdSJani Nikula bypassed) which are not detectable by 796e52347bdSJani Nikula CONFIG_DEBUG_PAGEALLOC, hence this option will not help 797e52347bdSJani Nikula tracking down these problems. 798e52347bdSJani Nikula 799e52347bdSJani Nikula debug_pagealloc= 800e52347bdSJani Nikula [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this 801e52347bdSJani Nikula parameter enables the feature at boot time. In 802e52347bdSJani Nikula default, it is disabled. We can avoid allocating huge 803e52347bdSJani Nikula chunk of memory for debug pagealloc if we don't enable 804e52347bdSJani Nikula it at boot time and the system will work mostly same 805e52347bdSJani Nikula with the kernel built without CONFIG_DEBUG_PAGEALLOC. 806e52347bdSJani Nikula on: enable the feature 807e52347bdSJani Nikula 808e52347bdSJani Nikula debugpat [X86] Enable PAT debugging 809e52347bdSJani Nikula 810e52347bdSJani Nikula decnet.addr= [HW,NET] 811e52347bdSJani Nikula Format: <area>[,<node>] 812e52347bdSJani Nikula See also Documentation/networking/decnet.txt. 813e52347bdSJani Nikula 814e52347bdSJani Nikula default_hugepagesz= 815e52347bdSJani Nikula [same as hugepagesz=] The size of the default 816e52347bdSJani Nikula HugeTLB page size. This is the size represented by 817e52347bdSJani Nikula the legacy /proc/ hugepages APIs, used for SHM, and 818e52347bdSJani Nikula default size when mounting hugetlbfs filesystems. 819e52347bdSJani Nikula Defaults to the default architecture's huge page size 820e52347bdSJani Nikula if not specified. 821e52347bdSJani Nikula 82225b4e70dSRob Herring deferred_probe_timeout= 82325b4e70dSRob Herring [KNL] Debugging option to set a timeout in seconds for 82425b4e70dSRob Herring deferred probe to give up waiting on dependencies to 82525b4e70dSRob Herring probe. Only specific dependencies (subsystems or 82625b4e70dSRob Herring drivers) that have opted in will be ignored. A timeout of 0 82725b4e70dSRob Herring will timeout at the end of initcalls. This option will also 82825b4e70dSRob Herring dump out devices still on the deferred probe list after 82925b4e70dSRob Herring retrying. 83025b4e70dSRob Herring 831e52347bdSJani Nikula dhash_entries= [KNL] 832e52347bdSJani Nikula Set number of hash buckets for dentry cache. 833e52347bdSJani Nikula 834e52347bdSJani Nikula disable_1tb_segments [PPC] 835e52347bdSJani Nikula Disables the use of 1TB hash page table segments. This 836e52347bdSJani Nikula causes the kernel to fall back to 256MB segments which 837e52347bdSJani Nikula can be useful when debugging issues that require an SLB 838e52347bdSJani Nikula miss to occur. 839e52347bdSJani Nikula 840e52347bdSJani Nikula disable= [IPV6] 841e52347bdSJani Nikula See Documentation/networking/ipv6.txt. 842e52347bdSJani Nikula 843b5cb15d9SChris von Recklinghausen hardened_usercopy= 844b5cb15d9SChris von Recklinghausen [KNL] Under CONFIG_HARDENED_USERCOPY, whether 845b5cb15d9SChris von Recklinghausen hardening is enabled for this boot. Hardened 846b5cb15d9SChris von Recklinghausen usercopy checking is used to protect the kernel 847b5cb15d9SChris von Recklinghausen from reading or writing beyond known memory 848b5cb15d9SChris von Recklinghausen allocation boundaries as a proactive defense 849b5cb15d9SChris von Recklinghausen against bounds-checking flaws in the kernel's 850b5cb15d9SChris von Recklinghausen copy_to_user()/copy_from_user() interface. 851b5cb15d9SChris von Recklinghausen on Perform hardened usercopy checks (default). 852b5cb15d9SChris von Recklinghausen off Disable hardened usercopy checks. 853b5cb15d9SChris von Recklinghausen 854e52347bdSJani Nikula disable_radix [PPC] 855e52347bdSJani Nikula Disable RADIX MMU mode on POWER9 856e52347bdSJani Nikula 857e52347bdSJani Nikula disable_cpu_apicid= [X86,APIC,SMP] 858e52347bdSJani Nikula Format: <int> 859e52347bdSJani Nikula The number of initial APIC ID for the 860e52347bdSJani Nikula corresponding CPU to be disabled at boot, 861e52347bdSJani Nikula mostly used for the kdump 2nd kernel to 862e52347bdSJani Nikula disable BSP to wake up multiple CPUs without 863e52347bdSJani Nikula causing system reset or hang due to sending 864e52347bdSJani Nikula INIT from AP to BSP. 865e52347bdSJani Nikula 8662a5bf23dSPeter Zijlstra perf_v4_pmi= [X86,INTEL] 8672a5bf23dSPeter Zijlstra Format: <bool> 868af3bdb99SAndi Kleen Disable Intel PMU counter freezing feature. 869af3bdb99SAndi Kleen The feature only exists starting from 870af3bdb99SAndi Kleen Arch Perfmon v4 (Skylake and newer). 871af3bdb99SAndi Kleen 872e52347bdSJani Nikula disable_ddw [PPC/PSERIES] 873e52347bdSJani Nikula Disable Dynamic DMA Window support. Use this if 874e52347bdSJani Nikula to workaround buggy firmware. 875e52347bdSJani Nikula 876e52347bdSJani Nikula disable_ipv6= [IPV6] 877e52347bdSJani Nikula See Documentation/networking/ipv6.txt. 878e52347bdSJani Nikula 879e52347bdSJani Nikula disable_mtrr_cleanup [X86] 880e52347bdSJani Nikula The kernel tries to adjust MTRR layout from continuous 881e52347bdSJani Nikula to discrete, to make X server driver able to add WB 882e52347bdSJani Nikula entry later. This parameter disables that. 883e52347bdSJani Nikula 884e52347bdSJani Nikula disable_mtrr_trim [X86, Intel and AMD only] 885e52347bdSJani Nikula By default the kernel will trim any uncacheable 886e52347bdSJani Nikula memory out of your available memory pool based on 887e52347bdSJani Nikula MTRR settings. This parameter disables that behavior, 888e52347bdSJani Nikula possibly causing your machine to run very slowly. 889e52347bdSJani Nikula 890e52347bdSJani Nikula disable_timer_pin_1 [X86] 891e52347bdSJani Nikula Disable PIN 1 of APIC timer 892e52347bdSJani Nikula Can be useful to work around chipset bugs. 893e52347bdSJani Nikula 894e52347bdSJani Nikula dis_ucode_ldr [X86] Disable the microcode loader. 895e52347bdSJani Nikula 896e52347bdSJani Nikula dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, 897e52347bdSJani Nikula this option disables the debugging code at boot. 898e52347bdSJani Nikula 899e52347bdSJani Nikula dma_debug_entries=<number> 900e52347bdSJani Nikula This option allows to tune the number of preallocated 901e52347bdSJani Nikula entries for DMA-API debugging code. One entry is 902e52347bdSJani Nikula required per DMA-API allocation. Use this if the 903e52347bdSJani Nikula DMA-API debugging code disables itself because the 904e52347bdSJani Nikula architectural default is too low. 905e52347bdSJani Nikula 906e52347bdSJani Nikula dma_debug_driver=<driver_name> 907e52347bdSJani Nikula With this option the DMA-API debugging driver 908e52347bdSJani Nikula filter feature can be enabled at boot time. Just 909e52347bdSJani Nikula pass the driver to filter for as the parameter. 910e52347bdSJani Nikula The filter can be disabled or changed to another 911e52347bdSJani Nikula driver later using sysfs. 912e52347bdSJani Nikula 91353fd40a9SJani Nikula drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] 914e52347bdSJani Nikula Broken monitors, graphic adapters, KVMs and EDIDless 915e52347bdSJani Nikula panels may send no or incorrect EDID data sets. 916e52347bdSJani Nikula This parameter allows to specify an EDID data sets 917e52347bdSJani Nikula in the /lib/firmware directory that are used instead. 918e52347bdSJani Nikula Generic built-in EDID data sets are used, if one of 919e52347bdSJani Nikula edid/1024x768.bin, edid/1280x1024.bin, 920e52347bdSJani Nikula edid/1680x1050.bin, or edid/1920x1080.bin is given 921e52347bdSJani Nikula and no file with the same name exists. Details and 922e52347bdSJani Nikula instructions how to build your own EDID data are 923e52347bdSJani Nikula available in Documentation/EDID/HOWTO.txt. An EDID 924e52347bdSJani Nikula data set will only be used for a particular connector, 925e52347bdSJani Nikula if its name and a colon are prepended to the EDID 926e52347bdSJani Nikula name. Each connector may use a unique EDID data 927e52347bdSJani Nikula set by separating the files with a comma. An EDID 928e52347bdSJani Nikula data set with no connector name will be used for 929e52347bdSJani Nikula any connectors not explicitly specified. 930e52347bdSJani Nikula 931e52347bdSJani Nikula dscc4.setup= [NET] 932e52347bdSJani Nikula 933a2b05b7aSNicholas Piggin dt_cpu_ftrs= [PPC] 934a2b05b7aSNicholas Piggin Format: {"off" | "known"} 935a2b05b7aSNicholas Piggin Control how the dt_cpu_ftrs device-tree binding is 936a2b05b7aSNicholas Piggin used for CPU feature discovery and setup (if it 937a2b05b7aSNicholas Piggin exists). 938a2b05b7aSNicholas Piggin off: Do not use it, fall back to legacy cpu table. 939a2b05b7aSNicholas Piggin known: Do not pass through unknown features to guests 940a2b05b7aSNicholas Piggin or userspace, only those that the kernel is aware of. 941a2b05b7aSNicholas Piggin 942e7aa8c2eSLinus Torvalds dump_apple_properties [X86] 943e7aa8c2eSLinus Torvalds Dump name and content of EFI device properties on 944e7aa8c2eSLinus Torvalds x86 Macs. Useful for driver authors to determine 945e7aa8c2eSLinus Torvalds what data is available or for reverse-engineering. 946e7aa8c2eSLinus Torvalds 947e52347bdSJani Nikula dyndbg[="val"] [KNL,DYNAMIC_DEBUG] 948e52347bdSJani Nikula module.dyndbg[="val"] 949e52347bdSJani Nikula Enable debug messages at boot time. See 950787e3075SSteffen Maier Documentation/admin-guide/dynamic-debug-howto.rst 951787e3075SSteffen Maier for details. 952e52347bdSJani Nikula 953e52347bdSJani Nikula nompx [X86] Disables Intel Memory Protection Extensions. 954e52347bdSJani Nikula See Documentation/x86/intel_mpx.txt for more 955e52347bdSJani Nikula information about the feature. 956e52347bdSJani Nikula 957e52347bdSJani Nikula nopku [X86] Disable Memory Protection Keys CPU feature found 958e52347bdSJani Nikula in some Intel CPUs. 959e52347bdSJani Nikula 960e52347bdSJani Nikula module.async_probe [KNL] 961e52347bdSJani Nikula Enable asynchronous probe on this module. 962e52347bdSJani Nikula 963e52347bdSJani Nikula early_ioremap_debug [KNL] 964e52347bdSJani Nikula Enable debug messages in early_ioremap support. This 965e52347bdSJani Nikula is useful for tracking down temporary early mappings 966e52347bdSJani Nikula which are not unmapped. 967e52347bdSJani Nikula 968e52347bdSJani Nikula earlycon= [KNL] Output early console device and options. 969e52347bdSJani Nikula 9700231d000SPrarit Bhargava [ARM64] The early console is determined by the 9710231d000SPrarit Bhargava stdout-path property in device tree's chosen node, 9720231d000SPrarit Bhargava or determined by the ACPI SPCR table. 9730231d000SPrarit Bhargava 9740231d000SPrarit Bhargava [X86] When used with no options the early console is 9750231d000SPrarit Bhargava determined by the ACPI SPCR table. 976e52347bdSJani Nikula 977e52347bdSJani Nikula cdns,<addr>[,options] 978e52347bdSJani Nikula Start an early, polled-mode console on a Cadence 979e52347bdSJani Nikula (xuartps) serial port at the specified address. Only 980e52347bdSJani Nikula supported option is baud rate. If baud rate is not 981e52347bdSJani Nikula specified, the serial port must already be setup and 982e52347bdSJani Nikula configured. 983e52347bdSJani Nikula 984e52347bdSJani Nikula uart[8250],io,<addr>[,options] 985e52347bdSJani Nikula uart[8250],mmio,<addr>[,options] 986e52347bdSJani Nikula uart[8250],mmio32,<addr>[,options] 987e52347bdSJani Nikula uart[8250],mmio32be,<addr>[,options] 988e52347bdSJani Nikula uart[8250],0x<addr>[,options] 989e52347bdSJani Nikula Start an early, polled-mode console on the 8250/16550 990e52347bdSJani Nikula UART at the specified I/O port or MMIO address. 991e52347bdSJani Nikula MMIO inter-register address stride is either 8-bit 992e52347bdSJani Nikula (mmio) or 32-bit (mmio32 or mmio32be). 993e52347bdSJani Nikula If none of [io|mmio|mmio32|mmio32be], <addr> is assumed 994e52347bdSJani Nikula to be equivalent to 'mmio'. 'options' are specified 995e52347bdSJani Nikula in the same format described for "console=ttyS<n>"; if 996e52347bdSJani Nikula unspecified, the h/w is not initialized. 997e52347bdSJani Nikula 998e52347bdSJani Nikula pl011,<addr> 999e52347bdSJani Nikula pl011,mmio32,<addr> 1000e52347bdSJani Nikula Start an early, polled-mode console on a pl011 serial 1001e52347bdSJani Nikula port at the specified address. The pl011 serial port 1002e52347bdSJani Nikula must already be setup and configured. Options are not 1003e52347bdSJani Nikula yet supported. If 'mmio32' is specified, then only 1004e52347bdSJani Nikula the driver will use only 32-bit accessors to read/write 1005e52347bdSJani Nikula the device registers. 1006e52347bdSJani Nikula 1007e52347bdSJani Nikula meson,<addr> 1008e52347bdSJani Nikula Start an early, polled-mode console on a meson serial 1009e52347bdSJani Nikula port at the specified address. The serial port must 1010e52347bdSJani Nikula already be setup and configured. Options are not yet 1011e52347bdSJani Nikula supported. 1012e52347bdSJani Nikula 1013e52347bdSJani Nikula msm_serial,<addr> 1014e52347bdSJani Nikula Start an early, polled-mode console on an msm serial 1015e52347bdSJani Nikula port at the specified address. The serial port 1016e52347bdSJani Nikula must already be setup and configured. Options are not 1017e52347bdSJani Nikula yet supported. 1018e52347bdSJani Nikula 1019e52347bdSJani Nikula msm_serial_dm,<addr> 1020e52347bdSJani Nikula Start an early, polled-mode console on an msm serial 1021e52347bdSJani Nikula dm port at the specified address. The serial port 1022e52347bdSJani Nikula must already be setup and configured. Options are not 1023e52347bdSJani Nikula yet supported. 1024e52347bdSJani Nikula 1025e36361d7SAndreas Färber owl,<addr> 1026e36361d7SAndreas Färber Start an early, polled-mode console on a serial port 1027e36361d7SAndreas Färber of an Actions Semi SoC, such as S500 or S900, at the 1028e36361d7SAndreas Färber specified address. The serial port must already be 1029e36361d7SAndreas Färber setup and configured. Options are not yet supported. 1030e36361d7SAndreas Färber 1031c10b1332SManivannan Sadhasivam rda,<addr> 1032c10b1332SManivannan Sadhasivam Start an early, polled-mode console on a serial port 1033c10b1332SManivannan Sadhasivam of an RDA Micro SoC, such as RDA8810PL, at the 1034c10b1332SManivannan Sadhasivam specified address. The serial port must already be 1035c10b1332SManivannan Sadhasivam setup and configured. Options are not yet supported. 1036c10b1332SManivannan Sadhasivam 1037e52347bdSJani Nikula smh Use ARM semihosting calls for early console. 1038e52347bdSJani Nikula 1039e52347bdSJani Nikula s3c2410,<addr> 1040e52347bdSJani Nikula s3c2412,<addr> 1041e52347bdSJani Nikula s3c2440,<addr> 1042e52347bdSJani Nikula s3c6400,<addr> 1043e52347bdSJani Nikula s5pv210,<addr> 1044e52347bdSJani Nikula exynos4210,<addr> 1045e52347bdSJani Nikula Use early console provided by serial driver available 1046e52347bdSJani Nikula on Samsung SoCs, requires selecting proper type and 1047e52347bdSJani Nikula a correct base address of the selected UART port. The 1048e52347bdSJani Nikula serial port must already be setup and configured. 1049e52347bdSJani Nikula Options are not yet supported. 1050e52347bdSJani Nikula 1051ec84aa0aSMartin Blumenstingl lantiq,<addr> 1052ec84aa0aSMartin Blumenstingl Start an early, polled-mode console on a lantiq serial 1053ec84aa0aSMartin Blumenstingl (lqasc) port at the specified address. The serial port 1054ec84aa0aSMartin Blumenstingl must already be setup and configured. Options are not 1055ec84aa0aSMartin Blumenstingl yet supported. 1056ec84aa0aSMartin Blumenstingl 1057e52347bdSJani Nikula lpuart,<addr> 1058e52347bdSJani Nikula lpuart32,<addr> 1059e52347bdSJani Nikula Use early console provided by Freescale LP UART driver 1060e52347bdSJani Nikula found on Freescale Vybrid and QorIQ LS1021A processors. 1061e52347bdSJani Nikula A valid base address must be provided, and the serial 1062e52347bdSJani Nikula port must already be setup and configured. 1063e52347bdSJani Nikula 1064f7c864e7SAndre Przywara ar3700_uart,<addr> 1065e52347bdSJani Nikula Start an early, polled-mode console on the 1066e52347bdSJani Nikula Armada 3700 serial port at the specified 1067e52347bdSJani Nikula address. The serial port must already be setup 1068e52347bdSJani Nikula and configured. Options are not yet supported. 1069e52347bdSJani Nikula 107043f1831bSKarthikeyan Ramasubramanian qcom_geni,<addr> 107143f1831bSKarthikeyan Ramasubramanian Start an early, polled-mode console on a Qualcomm 107243f1831bSKarthikeyan Ramasubramanian Generic Interface (GENI) based serial port at the 107343f1831bSKarthikeyan Ramasubramanian specified address. The serial port must already be 107443f1831bSKarthikeyan Ramasubramanian setup and configured. Options are not yet supported. 107543f1831bSKarthikeyan Ramasubramanian 10764ba66a97SArnd Bergmann earlyprintk= [X86,SH,ARM,M68k,S390] 1077e52347bdSJani Nikula earlyprintk=vga 1078e52347bdSJani Nikula earlyprintk=efi 107989175cf7SHeiko Carstens earlyprintk=sclp 1080e52347bdSJani Nikula earlyprintk=xen 1081e52347bdSJani Nikula earlyprintk=serial[,ttySn[,baudrate]] 1082e52347bdSJani Nikula earlyprintk=serial[,0x...[,baudrate]] 1083e52347bdSJani Nikula earlyprintk=ttySn[,baudrate] 1084e52347bdSJani Nikula earlyprintk=dbgp[debugController#] 1085d2266bbfSFeng Tang earlyprintk=pciserial[,force],bus:device.function[,baudrate] 10861b5aeebfSLu Baolu earlyprintk=xdbc[xhciController#] 1087e52347bdSJani Nikula 1088e52347bdSJani Nikula earlyprintk is useful when the kernel crashes before 1089e52347bdSJani Nikula the normal console is initialized. It is not enabled by 1090e52347bdSJani Nikula default because it has some cosmetic problems. 1091e52347bdSJani Nikula 1092e52347bdSJani Nikula Append ",keep" to not disable it when the real console 1093e52347bdSJani Nikula takes over. 1094e52347bdSJani Nikula 1095e52347bdSJani Nikula Only one of vga, efi, serial, or usb debug port can 1096e52347bdSJani Nikula be used at a time. 1097e52347bdSJani Nikula 1098e52347bdSJani Nikula Currently only ttyS0 and ttyS1 may be specified by 1099e52347bdSJani Nikula name. Other I/O ports may be explicitly specified 1100e52347bdSJani Nikula on some architectures (x86 and arm at least) by 1101e52347bdSJani Nikula replacing ttySn with an I/O port address, like this: 1102e52347bdSJani Nikula earlyprintk=serial,0x1008,115200 1103e52347bdSJani Nikula You can find the port for a given device in 1104e52347bdSJani Nikula /proc/tty/driver/serial: 1105e52347bdSJani Nikula 2: uart:ST16650V2 port:00001008 irq:18 ... 1106e52347bdSJani Nikula 1107e52347bdSJani Nikula Interaction with the standard serial driver is not 1108e52347bdSJani Nikula very good. 1109e52347bdSJani Nikula 1110e52347bdSJani Nikula The VGA and EFI output is eventually overwritten by 1111e52347bdSJani Nikula the real console. 1112e52347bdSJani Nikula 1113e52347bdSJani Nikula The xen output can only be used by Xen PV guests. 1114e52347bdSJani Nikula 111589175cf7SHeiko Carstens The sclp output can only be used on s390. 111689175cf7SHeiko Carstens 1117d2266bbfSFeng Tang The optional "force" to "pciserial" enables use of a 1118d2266bbfSFeng Tang PCI device even when its classcode is not of the 1119d2266bbfSFeng Tang UART class. 1120d2266bbfSFeng Tang 1121e52347bdSJani Nikula edac_report= [HW,EDAC] Control how to report EDAC event 1122e52347bdSJani Nikula Format: {"on" | "off" | "force"} 1123e52347bdSJani Nikula on: enable EDAC to report H/W event. May be overridden 1124e52347bdSJani Nikula by other higher priority error reporting module. 1125e52347bdSJani Nikula off: disable H/W event reporting through EDAC. 1126e52347bdSJani Nikula force: enforce the use of EDAC to report H/W event. 1127e52347bdSJani Nikula default: on. 1128e52347bdSJani Nikula 1129e52347bdSJani Nikula ekgdboc= [X86,KGDB] Allow early kernel console debugging 1130e52347bdSJani Nikula ekgdboc=kbd 1131e52347bdSJani Nikula 1132e52347bdSJani Nikula This is designed to be used in conjunction with 1133e52347bdSJani Nikula the boot argument: earlyprintk=vga 1134e52347bdSJani Nikula 1135e52347bdSJani Nikula edd= [EDD] 1136e52347bdSJani Nikula Format: {"off" | "on" | "skip[mbr]"} 1137e52347bdSJani Nikula 1138e52347bdSJani Nikula efi= [EFI] 1139e52347bdSJani Nikula Format: { "old_map", "nochunk", "noruntime", "debug" } 1140e52347bdSJani Nikula old_map [X86-64]: switch to the old ioremap-based EFI 1141e52347bdSJani Nikula runtime services mapping. 32-bit still uses this one by 1142e52347bdSJani Nikula default. 1143e52347bdSJani Nikula nochunk: disable reading files in "chunks" in the EFI 1144e52347bdSJani Nikula boot stub, as chunking can cause problems with some 1145e52347bdSJani Nikula firmware implementations. 1146e52347bdSJani Nikula noruntime : disable EFI runtime services support 1147e52347bdSJani Nikula debug: enable misc debug output 1148e52347bdSJani Nikula 1149e52347bdSJani Nikula efi_no_storage_paranoia [EFI; X86] 1150e52347bdSJani Nikula Using this parameter you can use more than 50% of 1151e52347bdSJani Nikula your efi variable storage. Use this parameter only if 1152e52347bdSJani Nikula you are really sure that your UEFI does sane gc and 1153e52347bdSJani Nikula fulfills the spec otherwise your board may brick. 1154e52347bdSJani Nikula 1155e52347bdSJani Nikula efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] 1156e52347bdSJani Nikula Add arbitrary attribute to specific memory range by 1157e52347bdSJani Nikula updating original EFI memory map. 1158e52347bdSJani Nikula Region of memory which aa attribute is added to is 1159e52347bdSJani Nikula from ss to ss+nn. 1160e52347bdSJani Nikula If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 1161e52347bdSJani Nikula is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) 1162e52347bdSJani Nikula attribute is added to range 0x100000000-0x180000000 and 1163e52347bdSJani Nikula 0x10a0000000-0x1120000000. 1164e52347bdSJani Nikula 1165e52347bdSJani Nikula Using this parameter you can do debugging of EFI memmap 1166e52347bdSJani Nikula related feature. For example, you can do debugging of 1167e52347bdSJani Nikula Address Range Mirroring feature even if your box 1168e52347bdSJani Nikula doesn't support it. 1169e52347bdSJani Nikula 1170e52347bdSJani Nikula efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT 1171e52347bdSJani Nikula that is to be dynamically loaded by Linux. If there are 1172e52347bdSJani Nikula multiple variables with the same name but with different 1173e52347bdSJani Nikula vendor GUIDs, all of them will be loaded. See 1174e52347bdSJani Nikula Documentation/acpi/ssdt-overlays.txt for details. 1175e52347bdSJani Nikula 1176e52347bdSJani Nikula 1177e52347bdSJani Nikula eisa_irq_edge= [PARISC,HW] 1178e52347bdSJani Nikula See header of drivers/parisc/eisa.c. 1179e52347bdSJani Nikula 1180e52347bdSJani Nikula elanfreq= [X86-32] 1181e52347bdSJani Nikula See comment before function elanfreq_setup() in 1182e52347bdSJani Nikula arch/x86/kernel/cpu/cpufreq/elanfreq.c. 1183e52347bdSJani Nikula 1184e52347bdSJani Nikula elevator= [IOSCHED] 118531dcbbefSOtto Sabart Format: { "mq-deadline" | "kyber" | "bfq" } 118631dcbbefSOtto Sabart See Documentation/block/deadline-iosched.txt, 118731dcbbefSOtto Sabart Documentation/block/kyber-iosched.txt and 118831dcbbefSOtto Sabart Documentation/block/bfq-iosched.txt for details. 1189e52347bdSJani Nikula 1190e52347bdSJani Nikula elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] 1191e52347bdSJani Nikula Specifies physical address of start of kernel core 1192e52347bdSJani Nikula image elf header and optionally the size. Generally 1193e52347bdSJani Nikula kexec loader will pass this option to capture kernel. 1194e52347bdSJani Nikula See Documentation/kdump/kdump.txt for details. 1195e52347bdSJani Nikula 1196e52347bdSJani Nikula enable_mtrr_cleanup [X86] 1197e52347bdSJani Nikula The kernel tries to adjust MTRR layout from continuous 1198e52347bdSJani Nikula to discrete, to make X server driver able to add WB 1199e52347bdSJani Nikula entry later. This parameter enables that. 1200e52347bdSJani Nikula 1201e52347bdSJani Nikula enable_timer_pin_1 [X86] 1202e52347bdSJani Nikula Enable PIN 1 of APIC timer 1203e52347bdSJani Nikula Can be useful to work around chipset bugs 1204e52347bdSJani Nikula (in particular on some ATI chipsets). 1205e52347bdSJani Nikula The kernel tries to set a reasonable default. 1206e52347bdSJani Nikula 1207e52347bdSJani Nikula enforcing [SELINUX] Set initial enforcing status. 1208e52347bdSJani Nikula Format: {"0" | "1"} 1209e52347bdSJani Nikula See security/selinux/Kconfig help text. 1210e52347bdSJani Nikula 0 -- permissive (log only, no denials). 1211e52347bdSJani Nikula 1 -- enforcing (deny and log). 1212e52347bdSJani Nikula Default value is 0. 1213e52347bdSJani Nikula Value can be changed at runtime via /selinux/enforce. 1214e52347bdSJani Nikula 1215e52347bdSJani Nikula erst_disable [ACPI] 1216e52347bdSJani Nikula Disable Error Record Serialization Table (ERST) 1217e52347bdSJani Nikula support. 1218e52347bdSJani Nikula 1219e52347bdSJani Nikula ether= [HW,NET] Ethernet cards parameters 1220e52347bdSJani Nikula This option is obsoleted by the "netdev=" option, which 1221e52347bdSJani Nikula has equivalent usage. See its documentation for details. 1222e52347bdSJani Nikula 1223e52347bdSJani Nikula evm= [EVM] 1224e52347bdSJani Nikula Format: { "fix" } 1225e52347bdSJani Nikula Permit 'security.evm' to be updated regardless of 1226e52347bdSJani Nikula current integrity status. 1227e52347bdSJani Nikula 1228e52347bdSJani Nikula failslab= 1229e52347bdSJani Nikula fail_page_alloc= 1230e52347bdSJani Nikula fail_make_request=[KNL] 1231e52347bdSJani Nikula General fault injection mechanism. 1232e52347bdSJani Nikula Format: <interval>,<probability>,<space>,<times> 1233e52347bdSJani Nikula See also Documentation/fault-injection/. 1234e52347bdSJani Nikula 1235e52347bdSJani Nikula floppy= [HW] 1236e52347bdSJani Nikula See Documentation/blockdev/floppy.txt. 1237e52347bdSJani Nikula 1238e52347bdSJani Nikula force_pal_cache_flush 1239e52347bdSJani Nikula [IA-64] Avoid check_sal_cache_flush which may hang on 1240e52347bdSJani Nikula buggy SAL_CACHE_FLUSH implementations. Using this 1241e52347bdSJani Nikula parameter will force ia64_sal_cache_flush to call 1242e52347bdSJani Nikula ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 1243e52347bdSJani Nikula 1244e52347bdSJani Nikula forcepae [X86-32] 1245e52347bdSJani Nikula Forcefully enable Physical Address Extension (PAE). 1246e52347bdSJani Nikula Many Pentium M systems disable PAE but may have a 1247e52347bdSJani Nikula functionally usable PAE implementation. 1248e52347bdSJani Nikula Warning: use of this parameter will taint the kernel 1249e52347bdSJani Nikula and may cause unknown problems. 1250e52347bdSJani Nikula 1251e52347bdSJani Nikula ftrace=[tracer] 1252e52347bdSJani Nikula [FTRACE] will set and start the specified tracer 1253e52347bdSJani Nikula as early as possible in order to facilitate early 1254e52347bdSJani Nikula boot debugging. 1255e52347bdSJani Nikula 1256e52347bdSJani Nikula ftrace_dump_on_oops[=orig_cpu] 1257e52347bdSJani Nikula [FTRACE] will dump the trace buffers on oops. 1258e52347bdSJani Nikula If no parameter is passed, ftrace will dump 1259e52347bdSJani Nikula buffers of all CPUs, but if you pass orig_cpu, it will 1260e52347bdSJani Nikula dump only the buffer of the CPU that triggered the 1261e52347bdSJani Nikula oops. 1262e52347bdSJani Nikula 1263e52347bdSJani Nikula ftrace_filter=[function-list] 1264e52347bdSJani Nikula [FTRACE] Limit the functions traced by the function 1265e52347bdSJani Nikula tracer at boot up. function-list is a comma separated 1266e52347bdSJani Nikula list of functions. This list can be changed at run 1267e52347bdSJani Nikula time by the set_ftrace_filter file in the debugfs 1268e52347bdSJani Nikula tracing directory. 1269e52347bdSJani Nikula 1270e52347bdSJani Nikula ftrace_notrace=[function-list] 1271e52347bdSJani Nikula [FTRACE] Do not trace the functions specified in 1272e52347bdSJani Nikula function-list. This list can be changed at run time 1273e52347bdSJani Nikula by the set_ftrace_notrace file in the debugfs 1274e52347bdSJani Nikula tracing directory. 1275e52347bdSJani Nikula 1276e52347bdSJani Nikula ftrace_graph_filter=[function-list] 1277e52347bdSJani Nikula [FTRACE] Limit the top level callers functions traced 1278e52347bdSJani Nikula by the function graph tracer at boot up. 1279e52347bdSJani Nikula function-list is a comma separated list of functions 1280e52347bdSJani Nikula that can be changed at run time by the 1281e52347bdSJani Nikula set_graph_function file in the debugfs tracing directory. 1282e52347bdSJani Nikula 1283e52347bdSJani Nikula ftrace_graph_notrace=[function-list] 1284e52347bdSJani Nikula [FTRACE] Do not trace from the functions specified in 1285e52347bdSJani Nikula function-list. This list is a comma separated list of 1286e52347bdSJani Nikula functions that can be changed at run time by the 1287e52347bdSJani Nikula set_graph_notrace file in the debugfs tracing directory. 1288e52347bdSJani Nikula 128965a50c65STodd Brandt ftrace_graph_max_depth=<uint> 129065a50c65STodd Brandt [FTRACE] Used with the function graph tracer. This is 129165a50c65STodd Brandt the max depth it will trace into a function. This value 129265a50c65STodd Brandt can be changed at run time by the max_graph_depth file 129365a50c65STodd Brandt in the tracefs tracing directory. default: 0 (no limit) 129465a50c65STodd Brandt 1295e52347bdSJani Nikula gamecon.map[2|3]= 1296e52347bdSJani Nikula [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 1297e52347bdSJani Nikula support via parallel port (up to 5 devices per port) 1298e52347bdSJani Nikula Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 12991752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 1300e52347bdSJani Nikula 1301e52347bdSJani Nikula gamma= [HW,DRM] 1302e52347bdSJani Nikula 1303e52347bdSJani Nikula gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 1304e52347bdSJani Nikula Format: off | on 1305e52347bdSJani Nikula default: on 1306e52347bdSJani Nikula 1307e52347bdSJani Nikula gcov_persist= [GCOV] When non-zero (default), profiling data for 1308e52347bdSJani Nikula kernel modules is saved and remains accessible via 1309e52347bdSJani Nikula debugfs, even when the module is unloaded/reloaded. 1310e52347bdSJani Nikula When zero, profiling data is discarded and associated 1311e52347bdSJani Nikula debugfs files are removed at module unload time. 1312e52347bdSJani Nikula 131347512cfdSThomas Gleixner goldfish [X86] Enable the goldfish android emulator platform. 131447512cfdSThomas Gleixner Don't use this when you are not running on the 131547512cfdSThomas Gleixner android emulator 131647512cfdSThomas Gleixner 1317e52347bdSJani Nikula gpt [EFI] Forces disk with valid GPT signature but 1318e52347bdSJani Nikula invalid Protective MBR to be treated as GPT. If the 1319e52347bdSJani Nikula primary GPT is corrupted, it enables the backup/alternate 1320e52347bdSJani Nikula GPT to be used instead. 1321e52347bdSJani Nikula 1322e52347bdSJani Nikula grcan.enable0= [HW] Configuration of physical interface 0. Determines 1323e52347bdSJani Nikula the "Enable 0" bit of the configuration register. 1324e52347bdSJani Nikula Format: 0 | 1 1325e52347bdSJani Nikula Default: 0 1326e52347bdSJani Nikula grcan.enable1= [HW] Configuration of physical interface 1. Determines 1327e52347bdSJani Nikula the "Enable 0" bit of the configuration register. 1328e52347bdSJani Nikula Format: 0 | 1 1329e52347bdSJani Nikula Default: 0 1330e52347bdSJani Nikula grcan.select= [HW] Select which physical interface to use. 1331e52347bdSJani Nikula Format: 0 | 1 1332e52347bdSJani Nikula Default: 0 1333e52347bdSJani Nikula grcan.txsize= [HW] Sets the size of the tx buffer. 1334e52347bdSJani Nikula Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0. 1335e52347bdSJani Nikula Default: 1024 1336e52347bdSJani Nikula grcan.rxsize= [HW] Sets the size of the rx buffer. 1337e52347bdSJani Nikula Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. 1338e52347bdSJani Nikula Default: 1024 1339e52347bdSJani Nikula 1340e52347bdSJani Nikula gpio-mockup.gpio_mockup_ranges 1341e52347bdSJani Nikula [HW] Sets the ranges of gpiochip of for this device. 1342e52347bdSJani Nikula Format: <start1>,<end1>,<start2>,<end2>... 1343e52347bdSJani Nikula 1344e52347bdSJani Nikula hardlockup_all_cpu_backtrace= 1345e52347bdSJani Nikula [KNL] Should the hard-lockup detector generate 1346e52347bdSJani Nikula backtraces on all cpus. 1347e52347bdSJani Nikula Format: <integer> 1348e52347bdSJani Nikula 1349e52347bdSJani Nikula hashdist= [KNL,NUMA] Large hashes allocated during boot 1350e52347bdSJani Nikula are distributed across NUMA nodes. Defaults on 1351e52347bdSJani Nikula for 64-bit NUMA, off otherwise. 1352e52347bdSJani Nikula Format: 0 | 1 (for off | on) 1353e52347bdSJani Nikula 1354e52347bdSJani Nikula hcl= [IA-64] SGI's Hardware Graph compatibility layer 1355e52347bdSJani Nikula 1356e52347bdSJani Nikula hd= [EIDE] (E)IDE hard drive subsystem geometry 1357e52347bdSJani Nikula Format: <cyl>,<head>,<sect> 1358e52347bdSJani Nikula 1359e52347bdSJani Nikula hest_disable [ACPI] 1360e52347bdSJani Nikula Disable Hardware Error Source Table (HEST) support; 1361e52347bdSJani Nikula corresponding firmware-first mode error processing 1362e52347bdSJani Nikula logic will be disabled. 1363e52347bdSJani Nikula 1364e52347bdSJani Nikula highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 1365e52347bdSJani Nikula size of <nn>. This works even on boxes that have no 1366e52347bdSJani Nikula highmem otherwise. This also works to reduce highmem 1367e52347bdSJani Nikula size on bigger boxes. 1368e52347bdSJani Nikula 1369e52347bdSJani Nikula highres= [KNL] Enable/disable high resolution timer mode. 1370e52347bdSJani Nikula Valid parameters: "on", "off" 1371e52347bdSJani Nikula Default: "on" 1372e52347bdSJani Nikula 1373e52347bdSJani Nikula hisax= [HW,ISDN] 1374e52347bdSJani Nikula See Documentation/isdn/README.HiSax. 1375e52347bdSJani Nikula 1376e52347bdSJani Nikula hlt [BUGS=ARM,SH] 1377e52347bdSJani Nikula 1378e52347bdSJani Nikula hpet= [X86-32,HPET] option to control HPET usage 1379e52347bdSJani Nikula Format: { enable (default) | disable | force | 1380e52347bdSJani Nikula verbose } 1381e52347bdSJani Nikula disable: disable HPET and use PIT instead 1382e52347bdSJani Nikula force: allow force enabled of undocumented chips (ICH4, 1383e52347bdSJani Nikula VIA, nVidia) 1384e52347bdSJani Nikula verbose: show contents of HPET registers during setup 1385e52347bdSJani Nikula 1386e52347bdSJani Nikula hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET 1387e52347bdSJani Nikula registers. Default set by CONFIG_HPET_MMAP_DEFAULT. 1388e52347bdSJani Nikula 1389e52347bdSJani Nikula hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. 1390e52347bdSJani Nikula hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. 1391e52347bdSJani Nikula On x86-64 and powerpc, this option can be specified 1392e52347bdSJani Nikula multiple times interleaved with hugepages= to reserve 1393e52347bdSJani Nikula huge pages of different sizes. Valid pages sizes on 1394e52347bdSJani Nikula x86-64 are 2M (when the CPU supports "pse") and 1G 1395e52347bdSJani Nikula (when the CPU supports the "pdpe1gb" cpuinfo flag). 1396e52347bdSJani Nikula 1397a49d9c0aSOmar Sandoval hung_task_panic= 1398a49d9c0aSOmar Sandoval [KNL] Should the hung task detector generate panics. 1399a49d9c0aSOmar Sandoval Format: <integer> 1400a49d9c0aSOmar Sandoval 1401a49d9c0aSOmar Sandoval A nonzero value instructs the kernel to panic when a 1402a49d9c0aSOmar Sandoval hung task is detected. The default value is controlled 1403a49d9c0aSOmar Sandoval by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time 1404a49d9c0aSOmar Sandoval option. The value selected by this boot parameter can 1405a49d9c0aSOmar Sandoval be changed later by the kernel.hung_task_panic sysctl. 1406a49d9c0aSOmar Sandoval 1407e52347bdSJani Nikula hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) 1408e52347bdSJani Nikula terminal devices. Valid values: 0..8 1409e52347bdSJani Nikula hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. 1410e52347bdSJani Nikula If specified, z/VM IUCV HVC accepts connections 1411e52347bdSJani Nikula from listed z/VM user IDs only. 14123a025de6SYi Sun 14133a025de6SYi Sun hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations 14143a025de6SYi Sun which allow the hypervisor to 'idle' the 14153a025de6SYi Sun guest on lock contention. 14163a025de6SYi Sun 1417e52347bdSJani Nikula keep_bootcon [KNL] 1418e52347bdSJani Nikula Do not unregister boot console at start. This is only 1419e52347bdSJani Nikula useful for debugging when something happens in the window 1420e52347bdSJani Nikula between unregistering the boot console and initializing 1421e52347bdSJani Nikula the real console. 1422e52347bdSJani Nikula 1423e52347bdSJani Nikula i2c_bus= [HW] Override the default board specific I2C bus speed 1424e52347bdSJani Nikula or register an additional I2C bus that is not 1425e52347bdSJani Nikula registered from board initialization code. 1426e52347bdSJani Nikula Format: 1427e52347bdSJani Nikula <bus_id>,<clkrate> 1428e52347bdSJani Nikula 1429e52347bdSJani Nikula i8042.debug [HW] Toggle i8042 debug mode 1430e52347bdSJani Nikula i8042.unmask_kbd_data 1431e52347bdSJani Nikula [HW] Enable printing of interrupt data from the KBD port 1432e52347bdSJani Nikula (disabled by default, and as a pre-condition 1433e52347bdSJani Nikula requires that i8042.debug=1 be enabled) 1434e52347bdSJani Nikula i8042.direct [HW] Put keyboard port into non-translated mode 1435e52347bdSJani Nikula i8042.dumbkbd [HW] Pretend that controller can only read data from 1436e52347bdSJani Nikula keyboard and cannot control its state 1437e52347bdSJani Nikula (Don't attempt to blink the leds) 1438e52347bdSJani Nikula i8042.noaux [HW] Don't check for auxiliary (== mouse) port 1439e52347bdSJani Nikula i8042.nokbd [HW] Don't check/create keyboard port 1440e52347bdSJani Nikula i8042.noloop [HW] Disable the AUX Loopback command while probing 1441e52347bdSJani Nikula for the AUX port 1442e52347bdSJani Nikula i8042.nomux [HW] Don't check presence of an active multiplexing 1443e52347bdSJani Nikula controller 1444e52347bdSJani Nikula i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 1445e52347bdSJani Nikula controllers 1446e52347bdSJani Nikula i8042.notimeout [HW] Ignore timeout condition signalled by controller 1447e52347bdSJani Nikula i8042.reset [HW] Reset the controller during init, cleanup and 1448e52347bdSJani Nikula suspend-to-ram transitions, only during s2r 1449e52347bdSJani Nikula transitions, or never reset 1450e52347bdSJani Nikula Format: { 1 | Y | y | 0 | N | n } 1451e52347bdSJani Nikula 1, Y, y: always reset controller 1452e52347bdSJani Nikula 0, N, n: don't ever reset controller 1453e52347bdSJani Nikula Default: only on s2r transitions on x86; most other 1454e52347bdSJani Nikula architectures force reset to be always executed 1455e52347bdSJani Nikula i8042.unlock [HW] Unlock (ignore) the keylock 1456e52347bdSJani Nikula i8042.kbdreset [HW] Reset device connected to KBD port 1457e52347bdSJani Nikula 1458e52347bdSJani Nikula i810= [HW,DRM] 1459e52347bdSJani Nikula 1460e52347bdSJani Nikula i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 1461e52347bdSJani Nikula indicates that the driver is running on unsupported 1462e52347bdSJani Nikula hardware. 1463e52347bdSJani Nikula i8k.force [HW] Activate i8k driver even if SMM BIOS signature 1464e52347bdSJani Nikula does not match list of supported models. 1465e52347bdSJani Nikula i8k.power_status 1466e52347bdSJani Nikula [HW] Report power status in /proc/i8k 1467e52347bdSJani Nikula (disabled by default) 1468e52347bdSJani Nikula i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 1469e52347bdSJani Nikula capability is set. 1470e52347bdSJani Nikula 1471e52347bdSJani Nikula i915.invert_brightness= 1472e52347bdSJani Nikula [DRM] Invert the sense of the variable that is used to 1473e52347bdSJani Nikula set the brightness of the panel backlight. Normally a 1474e52347bdSJani Nikula brightness value of 0 indicates backlight switched off, 1475e52347bdSJani Nikula and the maximum of the brightness value sets the backlight 1476e52347bdSJani Nikula to maximum brightness. If this parameter is set to 0 1477e52347bdSJani Nikula (default) and the machine requires it, or this parameter 1478e52347bdSJani Nikula is set to 1, a brightness value of 0 sets the backlight 1479e52347bdSJani Nikula to maximum brightness, and the maximum of the brightness 1480e52347bdSJani Nikula value switches the backlight off. 1481e52347bdSJani Nikula -1 -- never invert brightness 1482e52347bdSJani Nikula 0 -- machine default 1483e52347bdSJani Nikula 1 -- force brightness inversion 1484e52347bdSJani Nikula 1485e52347bdSJani Nikula icn= [HW,ISDN] 1486e52347bdSJani Nikula Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 1487e52347bdSJani Nikula 1488e52347bdSJani Nikula ide-core.nodma= [HW] (E)IDE subsystem 1489e52347bdSJani Nikula Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc 1490e52347bdSJani Nikula .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr 1491e52347bdSJani Nikula .cdrom .chs .ignore_cable are additional options 1492e52347bdSJani Nikula See Documentation/ide/ide.txt. 1493e52347bdSJani Nikula 1494e52347bdSJani Nikula ide-generic.probe-mask= [HW] (E)IDE subsystem 1495e52347bdSJani Nikula Format: <int> 1496e52347bdSJani Nikula Probe mask for legacy ISA IDE ports. Depending on 1497e52347bdSJani Nikula platform up to 6 ports are supported, enabled by 1498e52347bdSJani Nikula setting corresponding bits in the mask to 1. The 1499e52347bdSJani Nikula default value is 0x0, which has a special meaning. 1500e52347bdSJani Nikula On systems that have PCI, it triggers scanning the 1501e52347bdSJani Nikula PCI bus for the first and the second port, which 1502e52347bdSJani Nikula are then probed. On systems without PCI the value 1503e52347bdSJani Nikula of 0x0 enables probing the two first ports as if it 1504e52347bdSJani Nikula was 0x3. 1505e52347bdSJani Nikula 1506e52347bdSJani Nikula ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 1507e52347bdSJani Nikula Claim all unknown PCI IDE storage controllers. 1508e52347bdSJani Nikula 1509e52347bdSJani Nikula idle= [X86] 1510e52347bdSJani Nikula Format: idle=poll, idle=halt, idle=nomwait 1511e52347bdSJani Nikula Poll forces a polling idle loop that can slightly 1512e52347bdSJani Nikula improve the performance of waking up a idle CPU, but 1513e52347bdSJani Nikula will use a lot of power and make the system run hot. 1514e52347bdSJani Nikula Not recommended. 1515e52347bdSJani Nikula idle=halt: Halt is forced to be used for CPU idle. 1516e52347bdSJani Nikula In such case C2/C3 won't be used again. 1517e52347bdSJani Nikula idle=nomwait: Disable mwait for CPU C-states 1518e52347bdSJani Nikula 1519e52347bdSJani Nikula ieee754= [MIPS] Select IEEE Std 754 conformance mode 1520e52347bdSJani Nikula Format: { strict | legacy | 2008 | relaxed } 1521e52347bdSJani Nikula Default: strict 1522e52347bdSJani Nikula 1523e52347bdSJani Nikula Choose which programs will be accepted for execution 1524e52347bdSJani Nikula based on the IEEE 754 NaN encoding(s) supported by 1525e52347bdSJani Nikula the FPU and the NaN encoding requested with the value 1526e52347bdSJani Nikula of an ELF file header flag individually set by each 1527e52347bdSJani Nikula binary. Hardware implementations are permitted to 1528e52347bdSJani Nikula support either or both of the legacy and the 2008 NaN 1529e52347bdSJani Nikula encoding mode. 1530e52347bdSJani Nikula 1531e52347bdSJani Nikula Available settings are as follows: 1532e52347bdSJani Nikula strict accept binaries that request a NaN encoding 1533e52347bdSJani Nikula supported by the FPU 1534e52347bdSJani Nikula legacy only accept legacy-NaN binaries, if supported 1535e52347bdSJani Nikula by the FPU 1536e52347bdSJani Nikula 2008 only accept 2008-NaN binaries, if supported 1537e52347bdSJani Nikula by the FPU 1538e52347bdSJani Nikula relaxed accept any binaries regardless of whether 1539e52347bdSJani Nikula supported by the FPU 1540e52347bdSJani Nikula 1541e52347bdSJani Nikula The FPU emulator is always able to support both NaN 1542e52347bdSJani Nikula encodings, so if no FPU hardware is present or it has 1543e52347bdSJani Nikula been disabled with 'nofpu', then the settings of 1544e52347bdSJani Nikula 'legacy' and '2008' strap the emulator accordingly, 1545e52347bdSJani Nikula 'relaxed' straps the emulator for both legacy-NaN and 1546e52347bdSJani Nikula 2008-NaN, whereas 'strict' enables legacy-NaN only on 1547e52347bdSJani Nikula legacy processors and both NaN encodings on MIPS32 or 1548e52347bdSJani Nikula MIPS64 CPUs. 1549e52347bdSJani Nikula 1550e52347bdSJani Nikula The setting for ABS.fmt/NEG.fmt instruction execution 1551e52347bdSJani Nikula mode generally follows that for the NaN encoding, 1552e52347bdSJani Nikula except where unsupported by hardware. 1553e52347bdSJani Nikula 1554e52347bdSJani Nikula ignore_loglevel [KNL] 1555e52347bdSJani Nikula Ignore loglevel setting - this will print /all/ 1556e52347bdSJani Nikula kernel messages to the console. Useful for debugging. 1557e52347bdSJani Nikula We also add it as printk module parameter, so users 1558e52347bdSJani Nikula could change it dynamically, usually by 1559e52347bdSJani Nikula /sys/module/printk/parameters/ignore_loglevel. 1560e52347bdSJani Nikula 1561e52347bdSJani Nikula ignore_rlimit_data 1562e52347bdSJani Nikula Ignore RLIMIT_DATA setting for data mappings, 1563e52347bdSJani Nikula print warning at first misuse. Can be changed via 1564e52347bdSJani Nikula /sys/module/kernel/parameters/ignore_rlimit_data. 1565e52347bdSJani Nikula 1566e52347bdSJani Nikula ihash_entries= [KNL] 1567e52347bdSJani Nikula Set number of hash buckets for inode cache. 1568e52347bdSJani Nikula 1569e52347bdSJani Nikula ima_appraise= [IMA] appraise integrity measurements 1570e52347bdSJani Nikula Format: { "off" | "enforce" | "fix" | "log" } 1571e52347bdSJani Nikula default: "enforce" 1572e52347bdSJani Nikula 1573e52347bdSJani Nikula ima_appraise_tcb [IMA] 1574e52347bdSJani Nikula The builtin appraise policy appraises all files 1575e52347bdSJani Nikula owned by uid=0. 1576e52347bdSJani Nikula 1577d68a6fe9SMimi Zohar ima_canonical_fmt [IMA] 1578d68a6fe9SMimi Zohar Use the canonical format for the binary runtime 1579d68a6fe9SMimi Zohar measurements, instead of host native format. 1580d68a6fe9SMimi Zohar 1581e52347bdSJani Nikula ima_hash= [IMA] 1582e52347bdSJani Nikula Format: { md5 | sha1 | rmd160 | sha256 | sha384 1583e52347bdSJani Nikula | sha512 | ... } 1584e52347bdSJani Nikula default: "sha1" 1585e52347bdSJani Nikula 1586e52347bdSJani Nikula The list of supported hash algorithms is defined 1587e52347bdSJani Nikula in crypto/hash_info.h. 1588e52347bdSJani Nikula 1589e52347bdSJani Nikula ima_policy= [IMA] 159033ce9549SMimi Zohar The builtin policies to load during IMA setup. 15919e67028eSMimi Zohar Format: "tcb | appraise_tcb | secure_boot | 15929e67028eSMimi Zohar fail_securely" 159333ce9549SMimi Zohar 159433ce9549SMimi Zohar The "tcb" policy measures all programs exec'd, files 159533ce9549SMimi Zohar mmap'd for exec, and all files opened with the read 159633ce9549SMimi Zohar mode bit set by either the effective uid (euid=0) or 159733ce9549SMimi Zohar uid=0. 159833ce9549SMimi Zohar 159933ce9549SMimi Zohar The "appraise_tcb" policy appraises the integrity of 160033ce9549SMimi Zohar all files owned by root. (This is the equivalent 160133ce9549SMimi Zohar of ima_appraise_tcb.) 1602e52347bdSJani Nikula 1603503ceaefSMimi Zohar The "secure_boot" policy appraises the integrity 1604503ceaefSMimi Zohar of files (eg. kexec kernel image, kernel modules, 1605503ceaefSMimi Zohar firmware, policy, etc) based on file signatures. 1606e52347bdSJani Nikula 16079e67028eSMimi Zohar The "fail_securely" policy forces file signature 16089e67028eSMimi Zohar verification failure also on privileged mounted 16099e67028eSMimi Zohar filesystems with the SB_I_UNVERIFIABLE_SIGNATURE 16109e67028eSMimi Zohar flag. 16119e67028eSMimi Zohar 1612e52347bdSJani Nikula ima_tcb [IMA] Deprecated. Use ima_policy= instead. 1613e52347bdSJani Nikula Load a policy which meets the needs of the Trusted 1614e52347bdSJani Nikula Computing Base. This means IMA will measure all 1615e52347bdSJani Nikula programs exec'd, files mmap'd for exec, and all files 1616e52347bdSJani Nikula opened for read by uid=0. 1617e52347bdSJani Nikula 1618e52347bdSJani Nikula ima_template= [IMA] 1619e52347bdSJani Nikula Select one of defined IMA measurements template formats. 1620e52347bdSJani Nikula Formats: { "ima" | "ima-ng" | "ima-sig" } 1621e52347bdSJani Nikula Default: "ima-ng" 1622e52347bdSJani Nikula 1623e52347bdSJani Nikula ima_template_fmt= 1624e52347bdSJani Nikula [IMA] Define a custom template format. 1625e52347bdSJani Nikula Format: { "field1|...|fieldN" } 1626e52347bdSJani Nikula 1627e52347bdSJani Nikula ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage 1628e52347bdSJani Nikula Format: <min_file_size> 1629e52347bdSJani Nikula Set the minimal file size for using asynchronous hash. 1630e52347bdSJani Nikula If left unspecified, ahash usage is disabled. 1631e52347bdSJani Nikula 1632e52347bdSJani Nikula ahash performance varies for different data sizes on 1633e52347bdSJani Nikula different crypto accelerators. This option can be used 1634e52347bdSJani Nikula to achieve the best performance for a particular HW. 1635e52347bdSJani Nikula 1636e52347bdSJani Nikula ima.ahash_bufsize= [IMA] Asynchronous hash buffer size 1637e52347bdSJani Nikula Format: <bufsize> 1638e52347bdSJani Nikula Set hashing buffer size. Default: 4k. 1639e52347bdSJani Nikula 1640e52347bdSJani Nikula ahash performance varies for different chunk sizes on 1641e52347bdSJani Nikula different crypto accelerators. This option can be used 1642e52347bdSJani Nikula to achieve best performance for particular HW. 1643e52347bdSJani Nikula 1644e52347bdSJani Nikula init= [KNL] 1645e52347bdSJani Nikula Format: <full_path> 1646e52347bdSJani Nikula Run specified binary instead of /sbin/init as init 1647e52347bdSJani Nikula process. 1648e52347bdSJani Nikula 1649e52347bdSJani Nikula initcall_debug [KNL] Trace initcalls as they are executed. Useful 1650e52347bdSJani Nikula for working out where the kernel is dying during 1651e52347bdSJani Nikula startup. 1652e52347bdSJani Nikula 1653e52347bdSJani Nikula initcall_blacklist= [KNL] Do not execute a comma-separated list of 1654e52347bdSJani Nikula initcall functions. Useful for debugging built-in 1655e52347bdSJani Nikula modules and initcalls. 1656e52347bdSJani Nikula 1657e52347bdSJani Nikula initrd= [BOOT] Specify the location of the initial ramdisk 1658e52347bdSJani Nikula 1659e52347bdSJani Nikula init_pkru= [x86] Specify the default memory protection keys rights 1660e52347bdSJani Nikula register contents for all processes. 0x55555554 by 1661e52347bdSJani Nikula default (disallow access to all but pkey 0). Can 1662e52347bdSJani Nikula override in debugfs after boot. 1663e52347bdSJani Nikula 1664e52347bdSJani Nikula inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 1665e52347bdSJani Nikula Format: <irq> 1666e52347bdSJani Nikula 1667e52347bdSJani Nikula int_pln_enable [x86] Enable power limit notification interrupt 1668e52347bdSJani Nikula 1669e52347bdSJani Nikula integrity_audit=[IMA] 1670e52347bdSJani Nikula Format: { "0" | "1" } 1671e52347bdSJani Nikula 0 -- basic integrity auditing messages. (Default) 1672e52347bdSJani Nikula 1 -- additional integrity auditing messages. 1673e52347bdSJani Nikula 1674e52347bdSJani Nikula intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 1675e52347bdSJani Nikula on 1676e52347bdSJani Nikula Enable intel iommu driver. 1677e52347bdSJani Nikula off 1678e52347bdSJani Nikula Disable intel iommu driver. 1679e52347bdSJani Nikula igfx_off [Default Off] 1680e52347bdSJani Nikula By default, gfx is mapped as normal device. If a gfx 1681e52347bdSJani Nikula device has a dedicated DMAR unit, the DMAR unit is 1682e52347bdSJani Nikula bypassed by not enabling DMAR with this option. In 1683e52347bdSJani Nikula this case, gfx device will use physical address for 1684e52347bdSJani Nikula DMA. 1685e52347bdSJani Nikula forcedac [x86_64] 1686e52347bdSJani Nikula With this option iommu will not optimize to look 1687e52347bdSJani Nikula for io virtual address below 32-bit forcing dual 1688e52347bdSJani Nikula address cycle on pci bus for cards supporting greater 1689e52347bdSJani Nikula than 32-bit addressing. The default is to look 1690e52347bdSJani Nikula for translation below 32-bit and if not available 1691e52347bdSJani Nikula then look in the higher range. 1692e52347bdSJani Nikula strict [Default Off] 1693e52347bdSJani Nikula With this option on every unmap_single operation will 1694e52347bdSJani Nikula result in a hardware IOTLB flush operation as opposed 1695e52347bdSJani Nikula to batching them for performance. 1696e52347bdSJani Nikula sp_off [Default Off] 1697e52347bdSJani Nikula By default, super page will be supported if Intel IOMMU 1698e52347bdSJani Nikula has the capability. With this option, super page will 1699e52347bdSJani Nikula not be supported. 1700765b6a98SLu Baolu sm_off [Default Off] 1701765b6a98SLu Baolu By default, scalable mode will be supported if the 1702765b6a98SLu Baolu hardware advertises that it has support for the scalable 1703765b6a98SLu Baolu mode translation. With this option set, scalable mode 1704765b6a98SLu Baolu will not be used even on hardware which claims to support 1705765b6a98SLu Baolu it. 1706bfd20f1cSShaohua Li tboot_noforce [Default Off] 1707bfd20f1cSShaohua Li Do not force the Intel IOMMU enabled under tboot. 1708bfd20f1cSShaohua Li By default, tboot will force Intel IOMMU on, which 1709bfd20f1cSShaohua Li could harm performance of some high-throughput 1710bfd20f1cSShaohua Li devices like 40GBit network cards, even if identity 1711bfd20f1cSShaohua Li mapping is enabled. 1712bfd20f1cSShaohua Li Note that using this option lowers the security 1713bfd20f1cSShaohua Li provided by tboot because it makes the system 1714bfd20f1cSShaohua Li vulnerable to DMA attacks. 1715e52347bdSJani Nikula 1716e52347bdSJani Nikula intel_idle.max_cstate= [KNL,HW,ACPI,X86] 1717e52347bdSJani Nikula 0 disables intel_idle and fall back on acpi_idle. 1718e52347bdSJani Nikula 1 to 9 specify maximum depth of C-state. 1719e52347bdSJani Nikula 1720e52347bdSJani Nikula intel_pstate= [X86] 1721e52347bdSJani Nikula disable 1722e52347bdSJani Nikula Do not enable intel_pstate as the default 1723e52347bdSJani Nikula scaling driver for the supported processors 17247b9dc3f7SLinus Torvalds passive 17257b9dc3f7SLinus Torvalds Use intel_pstate as a scaling driver, but configure it 17267b9dc3f7SLinus Torvalds to work with generic cpufreq governors (instead of 17277b9dc3f7SLinus Torvalds enabling its internal governor). This mode cannot be 17287b9dc3f7SLinus Torvalds used along with the hardware-managed P-states (HWP) 17297b9dc3f7SLinus Torvalds feature. 1730e52347bdSJani Nikula force 1731e52347bdSJani Nikula Enable intel_pstate on systems that prohibit it by default 1732e52347bdSJani Nikula in favor of acpi-cpufreq. Forcing the intel_pstate driver 1733e52347bdSJani Nikula instead of acpi-cpufreq may disable platform features, such 1734e52347bdSJani Nikula as thermal controls and power capping, that rely on ACPI 1735e52347bdSJani Nikula P-States information being indicated to OSPM and therefore 1736e52347bdSJani Nikula should be used with caution. This option does not work with 1737e52347bdSJani Nikula processors that aren't supported by the intel_pstate driver 1738e52347bdSJani Nikula or on platforms that use pcc-cpufreq instead of acpi-cpufreq. 1739e52347bdSJani Nikula no_hwp 1740e52347bdSJani Nikula Do not enable hardware P state control (HWP) 1741e52347bdSJani Nikula if available. 1742e52347bdSJani Nikula hwp_only 1743e52347bdSJani Nikula Only load intel_pstate on systems which support 1744e52347bdSJani Nikula hardware P state control (HWP) if available. 1745e52347bdSJani Nikula support_acpi_ppc 1746e52347bdSJani Nikula Enforce ACPI _PPC performance limits. If the Fixed ACPI 1747e52347bdSJani Nikula Description Table, specifies preferred power management 1748e52347bdSJani Nikula profile as "Enterprise Server" or "Performance Server", 1749e52347bdSJani Nikula then this feature is turned on by default. 17507b9dc3f7SLinus Torvalds per_cpu_perf_limits 17517b9dc3f7SLinus Torvalds Allow per-logical-CPU P-State performance control limits using 17527b9dc3f7SLinus Torvalds cpufreq sysfs interface 1753e52347bdSJani Nikula 1754e52347bdSJani Nikula intremap= [X86-64, Intel-IOMMU] 1755e52347bdSJani Nikula on enable Interrupt Remapping (default) 1756e52347bdSJani Nikula off disable Interrupt Remapping 1757e52347bdSJani Nikula nosid disable Source ID checking 1758e52347bdSJani Nikula no_x2apic_optout 1759e52347bdSJani Nikula BIOS x2APIC opt-out request will be ignored 1760e52347bdSJani Nikula nopost disable Interrupt Posting 1761e52347bdSJani Nikula 1762e52347bdSJani Nikula iomem= Disable strict checking of access to MMIO memory 1763e52347bdSJani Nikula strict regions from userspace. 1764e52347bdSJani Nikula relaxed 1765e52347bdSJani Nikula 1766e52347bdSJani Nikula iommu= [x86] 1767e52347bdSJani Nikula off 1768e52347bdSJani Nikula force 1769e52347bdSJani Nikula noforce 1770e52347bdSJani Nikula biomerge 1771e52347bdSJani Nikula panic 1772e52347bdSJani Nikula nopanic 1773e52347bdSJani Nikula merge 1774e52347bdSJani Nikula nomerge 1775e52347bdSJani Nikula soft 177658d11317SOlof Johansson pt [x86] 177758d11317SOlof Johansson nopt [x86] 1778e52347bdSJani Nikula nobypass [PPC/POWERNV] 1779e52347bdSJani Nikula Disable IOMMU bypass, using IOMMU for PCI devices. 1780e52347bdSJani Nikula 178168a6efe8SZhen Lei iommu.strict= [ARM64] Configure TLB invalidation behaviour 178268a6efe8SZhen Lei Format: { "0" | "1" } 178368a6efe8SZhen Lei 0 - Lazy mode. 178468a6efe8SZhen Lei Request that DMA unmap operations use deferred 178568a6efe8SZhen Lei invalidation of hardware TLBs, for increased 178668a6efe8SZhen Lei throughput at the cost of reduced device isolation. 178768a6efe8SZhen Lei Will fall back to strict mode if not supported by 178868a6efe8SZhen Lei the relevant IOMMU driver. 178968a6efe8SZhen Lei 1 - Strict mode (default). 179068a6efe8SZhen Lei DMA unmap operations invalidate IOMMU hardware TLBs 179168a6efe8SZhen Lei synchronously. 179268a6efe8SZhen Lei 1793fccb4e3bSWill Deacon iommu.passthrough= 1794fccb4e3bSWill Deacon [ARM64] Configure DMA to bypass the IOMMU by default. 1795fccb4e3bSWill Deacon Format: { "0" | "1" } 1796fccb4e3bSWill Deacon 0 - Use IOMMU translation for DMA. 1797fccb4e3bSWill Deacon 1 - Bypass the IOMMU for DMA. 17989d723b4cSRobin Murphy unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. 1799e52347bdSJani Nikula 1800e52347bdSJani Nikula io7= [HW] IO7 for Marvel based alpha systems 1801e52347bdSJani Nikula See comment before marvel_specify_io7 in 1802e52347bdSJani Nikula arch/alpha/kernel/core_marvel.c. 1803e52347bdSJani Nikula 1804e52347bdSJani Nikula io_delay= [X86] I/O delay method 1805e52347bdSJani Nikula 0x80 1806e52347bdSJani Nikula Standard port 0x80 based delay 1807e52347bdSJani Nikula 0xed 1808e52347bdSJani Nikula Alternate port 0xed based delay (needed on some systems) 1809e52347bdSJani Nikula udelay 1810e52347bdSJani Nikula Simple two microseconds delay 1811e52347bdSJani Nikula none 1812e52347bdSJani Nikula No delay 1813e52347bdSJani Nikula 1814e52347bdSJani Nikula ip= [IP_PNP] 1815e52347bdSJani Nikula See Documentation/filesystems/nfs/nfsroot.txt. 1816e52347bdSJani Nikula 1817e52347bdSJani Nikula irqaffinity= [SMP] Set the default irq affinity mask 1818e52347bdSJani Nikula The argument is a cpu list, as described above. 1819e52347bdSJani Nikula 18200962289bSMarc Zyngier irqchip.gicv2_force_probe= 18210962289bSMarc Zyngier [ARM, ARM64] 18220962289bSMarc Zyngier Format: <bool> 18230962289bSMarc Zyngier Force the kernel to look for the second 4kB page 18240962289bSMarc Zyngier of a GICv2 controller even if the memory range 18250962289bSMarc Zyngier exposed by the device tree is too small. 18260962289bSMarc Zyngier 1827f736d65dSMarc Zyngier irqchip.gicv3_nolpi= 1828f736d65dSMarc Zyngier [ARM, ARM64] 1829f736d65dSMarc Zyngier Force the kernel to ignore the availability of 1830f736d65dSMarc Zyngier LPIs (and by consequence ITSs). Intended for system 1831f736d65dSMarc Zyngier that use the kernel as a bootloader, and thus want 1832f736d65dSMarc Zyngier to let secondary kernels in charge of setting up 1833f736d65dSMarc Zyngier LPIs. 1834f736d65dSMarc Zyngier 1835e52347bdSJani Nikula irqfixup [HW] 1836e52347bdSJani Nikula When an interrupt is not handled search all handlers 1837e52347bdSJani Nikula for it. Intended to get systems with badly broken 1838e52347bdSJani Nikula firmware running. 1839e52347bdSJani Nikula 1840e52347bdSJani Nikula irqpoll [HW] 1841e52347bdSJani Nikula When an interrupt is not handled search all handlers 1842e52347bdSJani Nikula for it. Also check all handlers each timer 1843e52347bdSJani Nikula interrupt. Intended to get systems with badly broken 1844e52347bdSJani Nikula firmware running. 1845e52347bdSJani Nikula 1846e52347bdSJani Nikula isapnp= [ISAPNP] 1847e52347bdSJani Nikula Format: <RDP>,<reset>,<pci_scan>,<verbosity> 1848e52347bdSJani Nikula 1849d94d1053SFrederic Weisbecker isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance. 1850b0d40d2bSFrederic Weisbecker [Deprecated - use cpusets instead] 1851b0d40d2bSFrederic Weisbecker Format: [flag-list,]<cpu-list> 1852e52347bdSJani Nikula 1853b0d40d2bSFrederic Weisbecker Specify one or more CPUs to isolate from disturbances 1854b0d40d2bSFrederic Weisbecker specified in the flag list (default: domain): 1855b0d40d2bSFrederic Weisbecker 1856b0d40d2bSFrederic Weisbecker nohz 1857b0d40d2bSFrederic Weisbecker Disable the tick when a single task runs. 1858083c6eeaSFrederic Weisbecker 1859083c6eeaSFrederic Weisbecker A residual 1Hz tick is offloaded to workqueues, which you 1860083c6eeaSFrederic Weisbecker need to affine to housekeeping through the global 1861083c6eeaSFrederic Weisbecker workqueue's affinity configured via the 1862083c6eeaSFrederic Weisbecker /sys/devices/virtual/workqueue/cpumask sysfs file, or 1863083c6eeaSFrederic Weisbecker by using the 'domain' flag described below. 1864083c6eeaSFrederic Weisbecker 1865083c6eeaSFrederic Weisbecker NOTE: by default the global workqueue runs on all CPUs, 1866083c6eeaSFrederic Weisbecker so to protect individual CPUs the 'cpumask' file has to 1867083c6eeaSFrederic Weisbecker be configured manually after bootup. 1868083c6eeaSFrederic Weisbecker 1869b0d40d2bSFrederic Weisbecker domain 1870b0d40d2bSFrederic Weisbecker Isolate from the general SMP balancing and scheduling 1871b0d40d2bSFrederic Weisbecker algorithms. Note that performing domain isolation this way 1872b0d40d2bSFrederic Weisbecker is irreversible: it's not possible to bring back a CPU to 1873b0d40d2bSFrederic Weisbecker the domains once isolated through isolcpus. It's strongly 1874b0d40d2bSFrederic Weisbecker advised to use cpusets instead to disable scheduler load 1875b0d40d2bSFrederic Weisbecker balancing through the "cpuset.sched_load_balance" file. 1876b0d40d2bSFrederic Weisbecker It offers a much more flexible interface where CPUs can 1877b0d40d2bSFrederic Weisbecker move in and out of an isolated set anytime. 1878b0d40d2bSFrederic Weisbecker 1879b0d40d2bSFrederic Weisbecker You can move a process onto or off an "isolated" CPU via 1880b0d40d2bSFrederic Weisbecker the CPU affinity syscalls or cpuset. 1881e52347bdSJani Nikula <cpu number> begins at 0 and the maximum value is 1882e52347bdSJani Nikula "number of CPUs in system - 1". 1883e52347bdSJani Nikula 1884b0d40d2bSFrederic Weisbecker The format of <cpu-list> is described above. 1885b0d40d2bSFrederic Weisbecker 1886b0d40d2bSFrederic Weisbecker 1887e52347bdSJani Nikula 1888e52347bdSJani Nikula iucv= [HW,NET] 1889e52347bdSJani Nikula 1890e52347bdSJani Nikula ivrs_ioapic [HW,X86_64] 1891e52347bdSJani Nikula Provide an override to the IOAPIC-ID<->DEVICE-ID 1892e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 1893e52347bdSJani Nikula example, to map IOAPIC-ID decimal 10 to 1894e52347bdSJani Nikula PCI device 00:14.0 write the parameter as: 1895e52347bdSJani Nikula ivrs_ioapic[10]=00:14.0 1896e52347bdSJani Nikula 1897e52347bdSJani Nikula ivrs_hpet [HW,X86_64] 1898e52347bdSJani Nikula Provide an override to the HPET-ID<->DEVICE-ID 1899e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 1900e52347bdSJani Nikula example, to map HPET-ID decimal 0 to 1901e52347bdSJani Nikula PCI device 00:14.0 write the parameter as: 1902e52347bdSJani Nikula ivrs_hpet[0]=00:14.0 1903e52347bdSJani Nikula 1904e52347bdSJani Nikula ivrs_acpihid [HW,X86_64] 1905e52347bdSJani Nikula Provide an override to the ACPI-HID:UID<->DEVICE-ID 1906e52347bdSJani Nikula mapping provided in the IVRS ACPI table. For 1907e52347bdSJani Nikula example, to map UART-HID:UID AMD0020:0 to 1908e52347bdSJani Nikula PCI device 00:14.5 write the parameter as: 1909e52347bdSJani Nikula ivrs_acpihid[00:14.5]=AMD0020:0 1910e52347bdSJani Nikula 1911e52347bdSJani Nikula js= [HW,JOY] Analog joystick 19121752118dSTom Saeger See Documentation/input/joydev/joystick.rst. 1913e52347bdSJani Nikula 1914e52347bdSJani Nikula nokaslr [KNL] 1915e52347bdSJani Nikula When CONFIG_RANDOMIZE_BASE is set, this disables 1916e52347bdSJani Nikula kernel and module base offset ASLR (Address Space 1917e52347bdSJani Nikula Layout Randomization). 1918e52347bdSJani Nikula 1919b0845ce5SMark Rutland kasan_multi_shot 1920b0845ce5SMark Rutland [KNL] Enforce KASAN (Kernel Address Sanitizer) to print 1921b0845ce5SMark Rutland report on every invalid memory access. Without this 1922b0845ce5SMark Rutland parameter KASAN will print report only for the first 1923b0845ce5SMark Rutland invalid access. 1924b0845ce5SMark Rutland 1925e52347bdSJani Nikula keepinitrd [HW,ARM] 1926e52347bdSJani Nikula 1927e52347bdSJani Nikula kernelcore= [KNL,X86,IA-64,PPC] 1928a5c6d650SDavid Rientjes Format: nn[KMGTPE] | nn% | "mirror" 1929a5c6d650SDavid Rientjes This parameter specifies the amount of memory usable by 1930a5c6d650SDavid Rientjes the kernel for non-movable allocations. The requested 1931a5c6d650SDavid Rientjes amount is spread evenly throughout all nodes in the 1932a5c6d650SDavid Rientjes system as ZONE_NORMAL. The remaining memory is used for 1933a5c6d650SDavid Rientjes movable memory in its own zone, ZONE_MOVABLE. In the 1934a5c6d650SDavid Rientjes event, a node is too small to have both ZONE_NORMAL and 1935a5c6d650SDavid Rientjes ZONE_MOVABLE, kernelcore memory will take priority and 1936a5c6d650SDavid Rientjes other nodes will have a larger ZONE_MOVABLE. 1937a5c6d650SDavid Rientjes 1938a5c6d650SDavid Rientjes ZONE_MOVABLE is used for the allocation of pages that 1939a5c6d650SDavid Rientjes may be reclaimed or moved by the page migration 1940a5c6d650SDavid Rientjes subsystem. Note that allocations like PTEs-from-HighMem 1941a5c6d650SDavid Rientjes still use the HighMem zone if it exists, and the Normal 1942e52347bdSJani Nikula zone if it does not. 1943e52347bdSJani Nikula 1944a5c6d650SDavid Rientjes It is possible to specify the exact amount of memory in 1945a5c6d650SDavid Rientjes the form of "nn[KMGTPE]", a percentage of total system 1946a5c6d650SDavid Rientjes memory in the form of "nn%", or "mirror". If "mirror" 1947e52347bdSJani Nikula option is specified, mirrored (reliable) memory is used 1948e52347bdSJani Nikula for non-movable allocations and remaining memory is used 1949a5c6d650SDavid Rientjes for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" 1950a5c6d650SDavid Rientjes are exclusive, so you cannot specify multiple forms. 1951e52347bdSJani Nikula 1952e52347bdSJani Nikula kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. 1953e52347bdSJani Nikula Format: <Controller#>[,poll interval] 1954e52347bdSJani Nikula The controller # is the number of the ehci usb debug 1955e52347bdSJani Nikula port as it is probed via PCI. The poll interval is 1956e52347bdSJani Nikula optional and is the number seconds in between 1957e52347bdSJani Nikula each poll cycle to the debug port in case you need 1958e52347bdSJani Nikula the functionality for interrupting the kernel with 1959e52347bdSJani Nikula gdb or control-c on the dbgp connection. When 1960e52347bdSJani Nikula not using this parameter you use sysrq-g to break into 1961e52347bdSJani Nikula the kernel debugger. 1962e52347bdSJani Nikula 1963e52347bdSJani Nikula kgdboc= [KGDB,HW] kgdb over consoles. 1964e52347bdSJani Nikula Requires a tty driver that supports console polling, 1965e52347bdSJani Nikula or a supported polling keyboard driver (non-usb). 1966e52347bdSJani Nikula Serial only format: <serial_device>[,baud] 1967e52347bdSJani Nikula keyboard only format: kbd 1968e52347bdSJani Nikula keyboard and serial format: kbd,<serial_device>[,baud] 1969e52347bdSJani Nikula Optional Kernel mode setting: 1970e52347bdSJani Nikula kms, kbd format: kms,kbd 1971e52347bdSJani Nikula kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] 1972e52347bdSJani Nikula 1973e52347bdSJani Nikula kgdbwait [KGDB] Stop kernel execution and enter the 1974e52347bdSJani Nikula kernel debugger at the earliest opportunity. 1975e52347bdSJani Nikula 1976e52347bdSJani Nikula kmac= [MIPS] korina ethernet MAC address. 1977e52347bdSJani Nikula Configure the RouterBoard 532 series on-chip 1978e52347bdSJani Nikula Ethernet adapter MAC address. 1979e52347bdSJani Nikula 1980e52347bdSJani Nikula kmemleak= [KNL] Boot-time kmemleak enable/disable 1981e52347bdSJani Nikula Valid arguments: on, off 1982e52347bdSJani Nikula Default: on 1983e52347bdSJani Nikula Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, 1984e52347bdSJani Nikula the default is off. 1985e52347bdSJani Nikula 1986e52347bdSJani Nikula kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. 1987e52347bdSJani Nikula Default is 0 (don't ignore, but inject #GP) 1988e52347bdSJani Nikula 1989c4ae60e4SLiran Alon kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface. 1990c4ae60e4SLiran Alon Default is false (don't support). 1991c4ae60e4SLiran Alon 1992e52347bdSJani Nikula kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit 1993e52347bdSJani Nikula KVM MMU at runtime. 1994e52347bdSJani Nikula Default is 0 (off) 1995e52347bdSJani Nikula 1996e52347bdSJani Nikula kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. 1997e52347bdSJani Nikula Default is 1 (enabled) 1998e52347bdSJani Nikula 1999e52347bdSJani Nikula kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) 2000e52347bdSJani Nikula for all guests. 2001e52347bdSJani Nikula Default is 1 (enabled) if in 64-bit or 32-bit PAE mode. 2002e52347bdSJani Nikula 2003e23f62f7SMarc Zyngier kvm-arm.vgic_v3_group0_trap= 2004e23f62f7SMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 group-0 2005e23f62f7SMarc Zyngier system registers 2006e23f62f7SMarc Zyngier 2007182936eeSMarc Zyngier kvm-arm.vgic_v3_group1_trap= 2008182936eeSMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 group-1 2009182936eeSMarc Zyngier system registers 2010182936eeSMarc Zyngier 2011ff89511eSMarc Zyngier kvm-arm.vgic_v3_common_trap= 2012ff89511eSMarc Zyngier [KVM,ARM] Trap guest accesses to GICv3 common 2013ff89511eSMarc Zyngier system registers 2014ff89511eSMarc Zyngier 2015a7546054SMarc Zyngier kvm-arm.vgic_v4_enable= 2016a7546054SMarc Zyngier [KVM,ARM] Allow use of GICv4 for direct injection of 2017a7546054SMarc Zyngier LPIs. 2018a7546054SMarc Zyngier 2019e52347bdSJani Nikula kvm-intel.ept= [KVM,Intel] Disable extended page tables 2020e52347bdSJani Nikula (virtualized MMU) support on capable Intel chips. 2021e52347bdSJani Nikula Default is 1 (enabled) 2022e52347bdSJani Nikula 2023e52347bdSJani Nikula kvm-intel.emulate_invalid_guest_state= 2024e52347bdSJani Nikula [KVM,Intel] Enable emulation of invalid guest states 2025e52347bdSJani Nikula Default is 0 (disabled) 2026e52347bdSJani Nikula 2027e52347bdSJani Nikula kvm-intel.flexpriority= 2028e52347bdSJani Nikula [KVM,Intel] Disable FlexPriority feature (TPR shadow). 2029e52347bdSJani Nikula Default is 1 (enabled) 2030e52347bdSJani Nikula 2031e52347bdSJani Nikula kvm-intel.nested= 2032e52347bdSJani Nikula [KVM,Intel] Enable VMX nesting (nVMX). 2033e52347bdSJani Nikula Default is 0 (disabled) 2034e52347bdSJani Nikula 2035e52347bdSJani Nikula kvm-intel.unrestricted_guest= 2036e52347bdSJani Nikula [KVM,Intel] Disable unrestricted guest feature 2037e52347bdSJani Nikula (virtualized real and unpaged mode) on capable 2038e52347bdSJani Nikula Intel chips. Default is 1 (enabled) 2039e52347bdSJani Nikula 2040a399477eSKonrad Rzeszutek Wilk kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault 2041a399477eSKonrad Rzeszutek Wilk CVE-2018-3620. 2042a399477eSKonrad Rzeszutek Wilk 2043a399477eSKonrad Rzeszutek Wilk Valid arguments: never, cond, always 2044a399477eSKonrad Rzeszutek Wilk 2045a399477eSKonrad Rzeszutek Wilk always: L1D cache flush on every VMENTER. 2046a399477eSKonrad Rzeszutek Wilk cond: Flush L1D on VMENTER only when the code between 2047a399477eSKonrad Rzeszutek Wilk VMEXIT and VMENTER can leak host memory. 2048a399477eSKonrad Rzeszutek Wilk never: Disables the mitigation 2049a399477eSKonrad Rzeszutek Wilk 2050a399477eSKonrad Rzeszutek Wilk Default is cond (do L1 cache flush in specific instances) 2051a399477eSKonrad Rzeszutek Wilk 2052e52347bdSJani Nikula kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification 2053e52347bdSJani Nikula feature (tagged TLBs) on capable Intel chips. 2054e52347bdSJani Nikula Default is 1 (enabled) 2055e52347bdSJani Nikula 2056d90a7a0eSJiri Kosina l1tf= [X86] Control mitigation of the L1TF vulnerability on 2057d90a7a0eSJiri Kosina affected CPUs 2058d90a7a0eSJiri Kosina 2059d90a7a0eSJiri Kosina The kernel PTE inversion protection is unconditionally 2060d90a7a0eSJiri Kosina enabled and cannot be disabled. 2061d90a7a0eSJiri Kosina 2062d90a7a0eSJiri Kosina full 2063d90a7a0eSJiri Kosina Provides all available mitigations for the 2064d90a7a0eSJiri Kosina L1TF vulnerability. Disables SMT and 2065d90a7a0eSJiri Kosina enables all mitigations in the 2066d90a7a0eSJiri Kosina hypervisors, i.e. unconditional L1D flush. 2067d90a7a0eSJiri Kosina 2068d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2069d90a7a0eSJiri Kosina sysfs interface is still possible after 2070d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2071d90a7a0eSJiri Kosina when the first VM is started in a 2072d90a7a0eSJiri Kosina potentially insecure configuration, 2073d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2074d90a7a0eSJiri Kosina 2075d90a7a0eSJiri Kosina full,force 2076d90a7a0eSJiri Kosina Same as 'full', but disables SMT and L1D 2077d90a7a0eSJiri Kosina flush runtime control. Implies the 2078d90a7a0eSJiri Kosina 'nosmt=force' command line option. 2079d90a7a0eSJiri Kosina (i.e. sysfs control of SMT is disabled.) 2080d90a7a0eSJiri Kosina 2081d90a7a0eSJiri Kosina flush 2082d90a7a0eSJiri Kosina Leaves SMT enabled and enables the default 2083d90a7a0eSJiri Kosina hypervisor mitigation, i.e. conditional 2084d90a7a0eSJiri Kosina L1D flush. 2085d90a7a0eSJiri Kosina 2086d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2087d90a7a0eSJiri Kosina sysfs interface is still possible after 2088d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2089d90a7a0eSJiri Kosina when the first VM is started in a 2090d90a7a0eSJiri Kosina potentially insecure configuration, 2091d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2092d90a7a0eSJiri Kosina 2093d90a7a0eSJiri Kosina flush,nosmt 2094d90a7a0eSJiri Kosina 2095d90a7a0eSJiri Kosina Disables SMT and enables the default 2096d90a7a0eSJiri Kosina hypervisor mitigation. 2097d90a7a0eSJiri Kosina 2098d90a7a0eSJiri Kosina SMT control and L1D flush control via the 2099d90a7a0eSJiri Kosina sysfs interface is still possible after 2100d90a7a0eSJiri Kosina boot. Hypervisors will issue a warning 2101d90a7a0eSJiri Kosina when the first VM is started in a 2102d90a7a0eSJiri Kosina potentially insecure configuration, 2103d90a7a0eSJiri Kosina i.e. SMT enabled or L1D flush disabled. 2104d90a7a0eSJiri Kosina 2105d90a7a0eSJiri Kosina flush,nowarn 2106d90a7a0eSJiri Kosina Same as 'flush', but hypervisors will not 2107d90a7a0eSJiri Kosina warn when a VM is started in a potentially 2108d90a7a0eSJiri Kosina insecure configuration. 2109d90a7a0eSJiri Kosina 2110d90a7a0eSJiri Kosina off 2111d90a7a0eSJiri Kosina Disables hypervisor mitigations and doesn't 2112d90a7a0eSJiri Kosina emit any warnings. 21135b5e4d62SMichal Hocko It also drops the swap size and available 21145b5e4d62SMichal Hocko RAM limit restriction on both hypervisor and 21155b5e4d62SMichal Hocko bare metal. 2116d90a7a0eSJiri Kosina 2117d90a7a0eSJiri Kosina Default is 'flush'. 2118d90a7a0eSJiri Kosina 2119d90a7a0eSJiri Kosina For details see: Documentation/admin-guide/l1tf.rst 2120d90a7a0eSJiri Kosina 2121e52347bdSJani Nikula l2cr= [PPC] 2122e52347bdSJani Nikula 2123e52347bdSJani Nikula l3cr= [PPC] 2124e52347bdSJani Nikula 2125e52347bdSJani Nikula lapic [X86-32,APIC] Enable the local APIC even if BIOS 2126e52347bdSJani Nikula disabled it. 2127e52347bdSJani Nikula 2128e52347bdSJani Nikula lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline 2129e52347bdSJani Nikula value for LAPIC timer one-shot implementation. Default 2130e52347bdSJani Nikula back to the programmable timer unit in the LAPIC. 2131e52347bdSJani Nikula 2132e52347bdSJani Nikula lapic_timer_c2_ok [X86,APIC] trust the local apic timer 2133e52347bdSJani Nikula in C2 power state. 2134e52347bdSJani Nikula 2135e52347bdSJani Nikula libata.dma= [LIBATA] DMA control 2136e52347bdSJani Nikula libata.dma=0 Disable all PATA and SATA DMA 2137e52347bdSJani Nikula libata.dma=1 PATA and SATA Disk DMA only 2138e52347bdSJani Nikula libata.dma=2 ATAPI (CDROM) DMA only 2139e52347bdSJani Nikula libata.dma=4 Compact Flash DMA only 2140e52347bdSJani Nikula Combinations also work, so libata.dma=3 enables DMA 2141e52347bdSJani Nikula for disks and CDROMs, but not CFs. 2142e52347bdSJani Nikula 2143e52347bdSJani Nikula libata.ignore_hpa= [LIBATA] Ignore HPA limit 2144e52347bdSJani Nikula libata.ignore_hpa=0 keep BIOS limits (default) 2145e52347bdSJani Nikula libata.ignore_hpa=1 ignore limits, using full disk 2146e52347bdSJani Nikula 2147e52347bdSJani Nikula libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 2148e52347bdSJani Nikula when set. 2149e52347bdSJani Nikula Format: <int> 2150e52347bdSJani Nikula 2151e52347bdSJani Nikula libata.force= [LIBATA] Force configurations. The format is comma 2152e52347bdSJani Nikula separated list of "[ID:]VAL" where ID is 2153e52347bdSJani Nikula PORT[.DEVICE]. PORT and DEVICE are decimal numbers 2154e52347bdSJani Nikula matching port, link or device. Basically, it matches 2155e52347bdSJani Nikula the ATA ID string printed on console by libata. If 2156e52347bdSJani Nikula the whole ID part is omitted, the last PORT and DEVICE 2157e52347bdSJani Nikula values are used. If ID hasn't been specified yet, the 2158e52347bdSJani Nikula configuration applies to all ports, links and devices. 2159e52347bdSJani Nikula 2160e52347bdSJani Nikula If only DEVICE is omitted, the parameter applies to 2161e52347bdSJani Nikula the port and all links and devices behind it. DEVICE 2162e52347bdSJani Nikula number of 0 either selects the first device or the 2163e52347bdSJani Nikula first fan-out link behind PMP device. It does not 2164e52347bdSJani Nikula select the host link. DEVICE number of 15 selects the 2165e52347bdSJani Nikula host link and device attached to it. 2166e52347bdSJani Nikula 2167e52347bdSJani Nikula The VAL specifies the configuration to force. As long 2168e52347bdSJani Nikula as there's no ambiguity shortcut notation is allowed. 2169e52347bdSJani Nikula For example, both 1.5 and 1.5G would work for 1.5Gbps. 2170e52347bdSJani Nikula The following configurations can be forced. 2171e52347bdSJani Nikula 2172e52347bdSJani Nikula * Cable type: 40c, 80c, short40c, unk, ign or sata. 2173e52347bdSJani Nikula Any ID with matching PORT is used. 2174e52347bdSJani Nikula 2175e52347bdSJani Nikula * SATA link speed limit: 1.5Gbps or 3.0Gbps. 2176e52347bdSJani Nikula 2177e52347bdSJani Nikula * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 2178e52347bdSJani Nikula udma[/][16,25,33,44,66,100,133] notation is also 2179e52347bdSJani Nikula allowed. 2180e52347bdSJani Nikula 2181e52347bdSJani Nikula * [no]ncq: Turn on or off NCQ. 2182e52347bdSJani Nikula 2183e52347bdSJani Nikula * [no]ncqtrim: Turn off queued DSM TRIM. 2184e52347bdSJani Nikula 2185e52347bdSJani Nikula * nohrst, nosrst, norst: suppress hard, soft 2186e52347bdSJani Nikula and both resets. 2187e52347bdSJani Nikula 2188e52347bdSJani Nikula * rstonce: only attempt one reset during 2189e52347bdSJani Nikula hot-unplug link recovery 2190e52347bdSJani Nikula 2191e52347bdSJani Nikula * dump_id: dump IDENTIFY data. 2192e52347bdSJani Nikula 2193e52347bdSJani Nikula * atapi_dmadir: Enable ATAPI DMADIR bridge support 2194e52347bdSJani Nikula 2195e52347bdSJani Nikula * disable: Disable this device. 2196e52347bdSJani Nikula 2197e52347bdSJani Nikula If there are multiple matching configurations changing 2198e52347bdSJani Nikula the same attribute, the last one is used. 2199e52347bdSJani Nikula 2200e52347bdSJani Nikula memblock=debug [KNL] Enable memblock debug messages. 2201e52347bdSJani Nikula 2202e52347bdSJani Nikula load_ramdisk= [RAM] List of ramdisks to load from floppy 2203e52347bdSJani Nikula See Documentation/blockdev/ramdisk.txt. 2204e52347bdSJani Nikula 2205e52347bdSJani Nikula lockd.nlm_grace_period=P [NFS] Assign grace period. 2206e52347bdSJani Nikula Format: <integer> 2207e52347bdSJani Nikula 2208e52347bdSJani Nikula lockd.nlm_tcpport=N [NFS] Assign TCP port. 2209e52347bdSJani Nikula Format: <integer> 2210e52347bdSJani Nikula 2211e52347bdSJani Nikula lockd.nlm_timeout=T [NFS] Assign timeout value. 2212e52347bdSJani Nikula Format: <integer> 2213e52347bdSJani Nikula 2214e52347bdSJani Nikula lockd.nlm_udpport=M [NFS] Assign UDP port. 2215e52347bdSJani Nikula Format: <integer> 2216e52347bdSJani Nikula 2217e52347bdSJani Nikula locktorture.nreaders_stress= [KNL] 2218e52347bdSJani Nikula Set the number of locking read-acquisition kthreads. 2219e52347bdSJani Nikula Defaults to being automatically set based on the 2220e52347bdSJani Nikula number of online CPUs. 2221e52347bdSJani Nikula 2222e52347bdSJani Nikula locktorture.nwriters_stress= [KNL] 2223e52347bdSJani Nikula Set the number of locking write-acquisition kthreads. 2224e52347bdSJani Nikula 2225e52347bdSJani Nikula locktorture.onoff_holdoff= [KNL] 2226e52347bdSJani Nikula Set time (s) after boot for CPU-hotplug testing. 2227e52347bdSJani Nikula 2228e52347bdSJani Nikula locktorture.onoff_interval= [KNL] 2229e52347bdSJani Nikula Set time (s) between CPU-hotplug operations, or 2230e52347bdSJani Nikula zero to disable CPU-hotplug testing. 2231e52347bdSJani Nikula 2232e52347bdSJani Nikula locktorture.shuffle_interval= [KNL] 2233e52347bdSJani Nikula Set task-shuffle interval (jiffies). Shuffling 2234e52347bdSJani Nikula tasks allows some CPUs to go into dyntick-idle 2235e52347bdSJani Nikula mode during the locktorture test. 2236e52347bdSJani Nikula 2237e52347bdSJani Nikula locktorture.shutdown_secs= [KNL] 2238e52347bdSJani Nikula Set time (s) after boot system shutdown. This 2239e52347bdSJani Nikula is useful for hands-off automated testing. 2240e52347bdSJani Nikula 2241e52347bdSJani Nikula locktorture.stat_interval= [KNL] 2242e52347bdSJani Nikula Time (s) between statistics printk()s. 2243e52347bdSJani Nikula 2244e52347bdSJani Nikula locktorture.stutter= [KNL] 2245e52347bdSJani Nikula Time (s) to stutter testing, for example, 2246e52347bdSJani Nikula specifying five seconds causes the test to run for 2247e52347bdSJani Nikula five seconds, wait for five seconds, and so on. 2248e52347bdSJani Nikula This tests the locking primitive's ability to 2249e52347bdSJani Nikula transition abruptly to and from idle. 2250e52347bdSJani Nikula 2251e52347bdSJani Nikula locktorture.torture_type= [KNL] 2252e52347bdSJani Nikula Specify the locking implementation to test. 2253e52347bdSJani Nikula 2254e52347bdSJani Nikula locktorture.verbose= [KNL] 2255e52347bdSJani Nikula Enable additional printk() statements. 2256e52347bdSJani Nikula 2257e52347bdSJani Nikula logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 2258e52347bdSJani Nikula Format: <irq> 2259e52347bdSJani Nikula 2260e52347bdSJani Nikula loglevel= All Kernel Messages with a loglevel smaller than the 2261e52347bdSJani Nikula console loglevel will be printed to the console. It can 2262e52347bdSJani Nikula also be changed with klogd or other programs. The 2263e52347bdSJani Nikula loglevels are defined as follows: 2264e52347bdSJani Nikula 2265e52347bdSJani Nikula 0 (KERN_EMERG) system is unusable 2266e52347bdSJani Nikula 1 (KERN_ALERT) action must be taken immediately 2267e52347bdSJani Nikula 2 (KERN_CRIT) critical conditions 2268e52347bdSJani Nikula 3 (KERN_ERR) error conditions 2269e52347bdSJani Nikula 4 (KERN_WARNING) warning conditions 2270e52347bdSJani Nikula 5 (KERN_NOTICE) normal but significant condition 2271e52347bdSJani Nikula 6 (KERN_INFO) informational 2272e52347bdSJani Nikula 7 (KERN_DEBUG) debug-level messages 2273e52347bdSJani Nikula 2274e52347bdSJani Nikula log_buf_len=n[KMG] Sets the size of the printk ring buffer, 2275e52347bdSJani Nikula in bytes. n must be a power of two and greater 2276e52347bdSJani Nikula than the minimal size. The minimal size is defined 2277e52347bdSJani Nikula by LOG_BUF_SHIFT kernel config parameter. There is 2278e52347bdSJani Nikula also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter 2279e52347bdSJani Nikula that allows to increase the default size depending on 2280e52347bdSJani Nikula the number of CPUs. See init/Kconfig for more details. 2281e52347bdSJani Nikula 2282e52347bdSJani Nikula logo.nologo [FB] Disables display of the built-in Linux logo. 2283e52347bdSJani Nikula This may be used to provide more screen space for 2284e52347bdSJani Nikula kernel log messages and is useful when debugging 2285e52347bdSJani Nikula kernel boot problems. 2286e52347bdSJani Nikula 2287e52347bdSJani Nikula lp=0 [LP] Specify parallel ports to use, e.g, 2288e52347bdSJani Nikula lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 2289e52347bdSJani Nikula lp=reset first parallel port). 'lp=0' disables the 2290e52347bdSJani Nikula lp=auto printer driver. 'lp=reset' (which can be 2291e52347bdSJani Nikula specified in addition to the ports) causes 2292e52347bdSJani Nikula attached printers to be reset. Using 2293e52347bdSJani Nikula lp=port1,port2,... specifies the parallel ports 2294e52347bdSJani Nikula to associate lp devices with, starting with 2295e52347bdSJani Nikula lp0. A port specification may be 'none' to skip 2296e52347bdSJani Nikula that lp device, or a parport name such as 2297e52347bdSJani Nikula 'parport0'. Specifying 'lp=auto' instead of a 2298e52347bdSJani Nikula port specification list means that device IDs 2299e52347bdSJani Nikula from each port should be examined, to see if 2300e52347bdSJani Nikula an IEEE 1284-compliant printer is attached; if 2301e52347bdSJani Nikula so, the driver will manage that printer. 2302e52347bdSJani Nikula See also header of drivers/char/lp.c. 2303e52347bdSJani Nikula 2304e52347bdSJani Nikula lpj=n [KNL] 2305e52347bdSJani Nikula Sets loops_per_jiffy to given constant, thus avoiding 2306e52347bdSJani Nikula time-consuming boot-time autodetection (up to 250 ms per 2307e52347bdSJani Nikula CPU). 0 enables autodetection (default). To determine 2308e52347bdSJani Nikula the correct value for your kernel, boot with normal 2309e52347bdSJani Nikula autodetection and see what value is printed. Note that 2310e52347bdSJani Nikula on SMP systems the preset will be applied to all CPUs, 2311e52347bdSJani Nikula which is likely to cause problems if your CPUs need 2312e52347bdSJani Nikula significantly divergent settings. An incorrect value 2313e52347bdSJani Nikula will cause delays in the kernel to be wrong, leading to 2314e52347bdSJani Nikula unpredictable I/O errors and other breakage. Although 2315e52347bdSJani Nikula unlikely, in the extreme case this might damage your 2316e52347bdSJani Nikula hardware. 2317e52347bdSJani Nikula 2318e52347bdSJani Nikula ltpc= [NET] 2319e52347bdSJani Nikula Format: <io>,<irq>,<dma> 2320e52347bdSJani Nikula 23219b8c7c14SKees Cook lsm.debug [SECURITY] Enable LSM initialization debugging output. 23229b8c7c14SKees Cook 2323e52347bdSJani Nikula machvec= [IA-64] Force the use of a particular machine-vector 2324e52347bdSJani Nikula (machvec) in a generic kernel. 2325e52347bdSJani Nikula Example: machvec=hpzx1_swiotlb 2326e52347bdSJani Nikula 2327e52347bdSJani Nikula machtype= [Loongson] Share the same kernel image file between different 2328e52347bdSJani Nikula yeeloong laptop. 2329e52347bdSJani Nikula Example: machtype=lemote-yeeloong-2f-7inch 2330e52347bdSJani Nikula 2331e52347bdSJani Nikula max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater 2332e52347bdSJani Nikula than or equal to this physical address is ignored. 2333e52347bdSJani Nikula 2334e52347bdSJani Nikula maxcpus= [SMP] Maximum number of processors that an SMP kernel 2335e52347bdSJani Nikula will bring up during bootup. maxcpus=n : n >= 0 limits 2336e52347bdSJani Nikula the kernel to bring up 'n' processors. Surely after 2337e52347bdSJani Nikula bootup you can bring up the other plugged cpu by executing 2338e52347bdSJani Nikula "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus 2339e52347bdSJani Nikula only takes effect during system bootup. 2340e52347bdSJani Nikula While n=0 is a special case, it is equivalent to "nosmp", 2341e52347bdSJani Nikula which also disables the IO APIC. 2342e52347bdSJani Nikula 2343e52347bdSJani Nikula max_loop= [LOOP] The number of loop block devices that get 2344e52347bdSJani Nikula (loop.max_loop) unconditionally pre-created at init time. The default 2345e52347bdSJani Nikula number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead 2346e52347bdSJani Nikula of statically allocating a predefined number, loop 2347e52347bdSJani Nikula devices can be requested on-demand with the 2348e52347bdSJani Nikula /dev/loop-control interface. 2349e52347bdSJani Nikula 2350e52347bdSJani Nikula mce [X86-32] Machine Check Exception 2351e52347bdSJani Nikula 2352e52347bdSJani Nikula mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt 2353e52347bdSJani Nikula 2354e52347bdSJani Nikula md= [HW] RAID subsystems devices and level 2355e52347bdSJani Nikula See Documentation/admin-guide/md.rst. 2356e52347bdSJani Nikula 2357e52347bdSJani Nikula mdacon= [MDA] 2358e52347bdSJani Nikula Format: <first>,<last> 2359e52347bdSJani Nikula Specifies range of consoles to be captured by the MDA. 2360e52347bdSJani Nikula 2361e52347bdSJani Nikula mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 2362e52347bdSJani Nikula Amount of memory to be used when the kernel is not able 2363e52347bdSJani Nikula to see the whole system memory or for test. 2364e52347bdSJani Nikula [X86] Work as limiting max address. Use together 2365e52347bdSJani Nikula with memmap= to avoid physical address space collisions. 2366e52347bdSJani Nikula Without memmap= PCI devices could be placed at addresses 2367e52347bdSJani Nikula belonging to unused RAM. 2368e52347bdSJani Nikula 2369e52347bdSJani Nikula mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 2370e52347bdSJani Nikula memory. 2371e52347bdSJani Nikula 2372e52347bdSJani Nikula memchunk=nn[KMG] 2373e52347bdSJani Nikula [KNL,SH] Allow user to override the default size for 2374e52347bdSJani Nikula per-device physically contiguous DMA buffers. 2375e52347bdSJani Nikula 2376e52347bdSJani Nikula memhp_default_state=online/offline 2377e52347bdSJani Nikula [KNL] Set the initial state for the memory hotplug 2378e52347bdSJani Nikula onlining policy. If not specified, the default value is 2379e52347bdSJani Nikula set according to the 2380e52347bdSJani Nikula CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config 2381e52347bdSJani Nikula option. 2382e52347bdSJani Nikula See Documentation/memory-hotplug.txt. 2383e52347bdSJani Nikula 2384e52347bdSJani Nikula memmap=exactmap [KNL,X86] Enable setting of an exact 2385e52347bdSJani Nikula E820 memory map, as specified by the user. 2386e52347bdSJani Nikula Such memmap=exactmap lines can be constructed based on 2387e52347bdSJani Nikula BIOS output or other requirements. See the memmap=nn@ss 2388e52347bdSJani Nikula option description. 2389e52347bdSJani Nikula 2390e52347bdSJani Nikula memmap=nn[KMG]@ss[KMG] 2391e52347bdSJani Nikula [KNL] Force usage of a specific region of memory. 2392e52347bdSJani Nikula Region of memory to be used is from ss to ss+nn. 23938fcc9bc3SBaoquan He If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG], 23948fcc9bc3SBaoquan He which limits max address to nn[KMG]. 23958fcc9bc3SBaoquan He Multiple different regions can be specified, 23968fcc9bc3SBaoquan He comma delimited. 23978fcc9bc3SBaoquan He Example: 23988fcc9bc3SBaoquan He memmap=100M@2G,100M#3G,1G!1024G 2399e52347bdSJani Nikula 2400e52347bdSJani Nikula memmap=nn[KMG]#ss[KMG] 2401e52347bdSJani Nikula [KNL,ACPI] Mark specific memory as ACPI data. 2402e52347bdSJani Nikula Region of memory to be marked is from ss to ss+nn. 2403e52347bdSJani Nikula 2404e52347bdSJani Nikula memmap=nn[KMG]$ss[KMG] 2405e52347bdSJani Nikula [KNL,ACPI] Mark specific memory as reserved. 2406e52347bdSJani Nikula Region of memory to be reserved is from ss to ss+nn. 2407e52347bdSJani Nikula Example: Exclude memory from 0x18690000-0x1869ffff 2408e52347bdSJani Nikula memmap=64K$0x18690000 2409e52347bdSJani Nikula or 2410e52347bdSJani Nikula memmap=0x10000$0x18690000 24118fcc9bc3SBaoquan He Some bootloaders may need an escape character before '$', 24128fcc9bc3SBaoquan He like Grub2, otherwise '$' and the following number 24138fcc9bc3SBaoquan He will be eaten. 2414e52347bdSJani Nikula 2415e52347bdSJani Nikula memmap=nn[KMG]!ss[KMG] 2416e52347bdSJani Nikula [KNL,X86] Mark specific memory as protected. 2417e52347bdSJani Nikula Region of memory to be used, from ss to ss+nn. 2418e52347bdSJani Nikula The memory region may be marked as e820 type 12 (0xc) 2419e52347bdSJani Nikula and is NVDIMM or ADR memory. 2420e52347bdSJani Nikula 2421ef61f8a3SJan H. Schönherr memmap=<size>%<offset>-<oldtype>+<newtype> 2422ef61f8a3SJan H. Schönherr [KNL,ACPI] Convert memory within the specified region 2423ef61f8a3SJan H. Schönherr from <oldtype> to <newtype>. If "-<oldtype>" is left 2424ef61f8a3SJan H. Schönherr out, the whole region will be marked as <newtype>, 2425ef61f8a3SJan H. Schönherr even if previously unavailable. If "+<newtype>" is left 2426ef61f8a3SJan H. Schönherr out, matching memory will be removed. Types are 2427ef61f8a3SJan H. Schönherr specified as e820 types, e.g., 1 = RAM, 2 = reserved, 2428ef61f8a3SJan H. Schönherr 3 = ACPI, 12 = PRAM. 2429ef61f8a3SJan H. Schönherr 2430e52347bdSJani Nikula memory_corruption_check=0/1 [X86] 2431e52347bdSJani Nikula Some BIOSes seem to corrupt the first 64k of 2432e52347bdSJani Nikula memory when doing things like suspend/resume. 2433e52347bdSJani Nikula Setting this option will scan the memory 2434e52347bdSJani Nikula looking for corruption. Enabling this will 2435e52347bdSJani Nikula both detect corruption and prevent the kernel 2436e52347bdSJani Nikula from using the memory being corrupted. 2437e52347bdSJani Nikula However, its intended as a diagnostic tool; if 2438e52347bdSJani Nikula repeatable BIOS-originated corruption always 2439e52347bdSJani Nikula affects the same memory, you can use memmap= 2440e52347bdSJani Nikula to prevent the kernel from using that memory. 2441e52347bdSJani Nikula 2442e52347bdSJani Nikula memory_corruption_check_size=size [X86] 2443e52347bdSJani Nikula By default it checks for corruption in the low 2444e52347bdSJani Nikula 64k, making this memory unavailable for normal 2445e52347bdSJani Nikula use. Use this parameter to scan for 2446e52347bdSJani Nikula corruption in more or less memory. 2447e52347bdSJani Nikula 2448e52347bdSJani Nikula memory_corruption_check_period=seconds [X86] 2449e52347bdSJani Nikula By default it checks for corruption every 60 2450e52347bdSJani Nikula seconds. Use this parameter to check at some 2451e52347bdSJani Nikula other rate. 0 disables periodic checking. 2452e52347bdSJani Nikula 2453d90fe2acSChristophe Leroy memtest= [KNL,X86,ARM,PPC] Enable memtest 2454e52347bdSJani Nikula Format: <integer> 2455e52347bdSJani Nikula default : 0 <disable> 2456e52347bdSJani Nikula Specifies the number of memtest passes to be 2457e52347bdSJani Nikula performed. Each pass selects another test 2458e52347bdSJani Nikula pattern from a given set of patterns. Memtest 2459e52347bdSJani Nikula fills the memory with this pattern, validates 2460e52347bdSJani Nikula memory contents and reserves bad memory 2461e52347bdSJani Nikula regions that are detected. 2462e52347bdSJani Nikula 2463c262f3b9STom Lendacky mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control 2464c262f3b9STom Lendacky Valid arguments: on, off 2465c262f3b9STom Lendacky Default (depends on kernel configuration option): 2466c262f3b9STom Lendacky on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y) 2467c262f3b9STom Lendacky off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n) 2468c262f3b9STom Lendacky mem_encrypt=on: Activate SME 2469c262f3b9STom Lendacky mem_encrypt=off: Do not activate SME 2470c262f3b9STom Lendacky 2471c262f3b9STom Lendacky Refer to Documentation/x86/amd-memory-encryption.txt 2472c262f3b9STom Lendacky for details on when memory encryption can be activated. 2473c262f3b9STom Lendacky 24747b9dc3f7SLinus Torvalds mem_sleep_default= [SUSPEND] Default system suspend mode: 24757b9dc3f7SLinus Torvalds s2idle - Suspend-To-Idle 24767b9dc3f7SLinus Torvalds shallow - Power-On Suspend or equivalent (if supported) 24777b9dc3f7SLinus Torvalds deep - Suspend-To-RAM or equivalent (if supported) 247858e7cb9eSRafael J. Wysocki See Documentation/admin-guide/pm/sleep-states.rst. 24797b9dc3f7SLinus Torvalds 2480e52347bdSJani Nikula meye.*= [HW] Set MotionEye Camera parameters 2481a405ed85STom Saeger See Documentation/media/v4l-drivers/meye.rst. 2482e52347bdSJani Nikula 2483e52347bdSJani Nikula mfgpt_irq= [IA-32] Specify the IRQ to use for the 2484e52347bdSJani Nikula Multi-Function General Purpose Timers on AMD Geode 2485e52347bdSJani Nikula platforms. 2486e52347bdSJani Nikula 2487e52347bdSJani Nikula mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 2488e52347bdSJani Nikula the BIOS has incorrectly applied a workaround. TinyBIOS 2489e52347bdSJani Nikula version 0.98 is known to be affected, 0.99 fixes the 2490e52347bdSJani Nikula problem by letting the user disable the workaround. 2491e52347bdSJani Nikula 2492e52347bdSJani Nikula mga= [HW,DRM] 2493e52347bdSJani Nikula 2494e52347bdSJani Nikula min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this 2495e52347bdSJani Nikula physical address is ignored. 2496e52347bdSJani Nikula 2497e52347bdSJani Nikula mini2440= [ARM,HW,KNL] 2498e52347bdSJani Nikula Format:[0..2][b][c][t] 2499e52347bdSJani Nikula Default: "0tb" 2500e52347bdSJani Nikula MINI2440 configuration specification: 2501e52347bdSJani Nikula 0 - The attached screen is the 3.5" TFT 2502e52347bdSJani Nikula 1 - The attached screen is the 7" TFT 2503e52347bdSJani Nikula 2 - The VGA Shield is attached (1024x768) 2504e52347bdSJani Nikula Leaving out the screen size parameter will not load 2505e52347bdSJani Nikula the TFT driver, and the framebuffer will be left 2506e52347bdSJani Nikula unconfigured. 2507e52347bdSJani Nikula b - Enable backlight. The TFT backlight pin will be 2508e52347bdSJani Nikula linked to the kernel VESA blanking code and a GPIO 2509e52347bdSJani Nikula LED. This parameter is not necessary when using the 2510e52347bdSJani Nikula VGA shield. 2511e52347bdSJani Nikula c - Enable the s3c camera interface. 2512e52347bdSJani Nikula t - Reserved for enabling touchscreen support. The 2513e52347bdSJani Nikula touchscreen support is not enabled in the mainstream 2514e52347bdSJani Nikula kernel as of 2.6.30, a preliminary port can be found 2515e52347bdSJani Nikula in the "bleeding edge" mini2440 support kernel at 2516e52347bdSJani Nikula http://repo.or.cz/w/linux-2.6/mini2440.git 2517e52347bdSJani Nikula 2518e52347bdSJani Nikula mminit_loglevel= 2519e52347bdSJani Nikula [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 2520e52347bdSJani Nikula parameter allows control of the logging verbosity for 2521e52347bdSJani Nikula the additional memory initialisation checks. A value 2522e52347bdSJani Nikula of 0 disables mminit logging and a level of 4 will 2523e52347bdSJani Nikula log everything. Information is printed at KERN_DEBUG 2524e52347bdSJani Nikula so loglevel=8 may also need to be specified. 2525e52347bdSJani Nikula 2526e52347bdSJani Nikula module.sig_enforce 2527e52347bdSJani Nikula [KNL] When CONFIG_MODULE_SIG is set, this means that 2528e52347bdSJani Nikula modules without (valid) signatures will fail to load. 2529e52347bdSJani Nikula Note that if CONFIG_MODULE_SIG_FORCE is set, that 2530e52347bdSJani Nikula is always true, so this option does nothing. 2531e52347bdSJani Nikula 2532e52347bdSJani Nikula module_blacklist= [KNL] Do not load a comma-separated list of 2533e52347bdSJani Nikula modules. Useful for debugging problem modules. 2534e52347bdSJani Nikula 2535e52347bdSJani Nikula mousedev.tap_time= 2536e52347bdSJani Nikula [MOUSE] Maximum time between finger touching and 2537e52347bdSJani Nikula leaving touchpad surface for touch to be considered 2538e52347bdSJani Nikula a tap and be reported as a left button click (for 2539e52347bdSJani Nikula touchpads working in absolute mode only). 2540e52347bdSJani Nikula Format: <msecs> 2541e52347bdSJani Nikula mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 2542e52347bdSJani Nikula reporting absolute coordinates, such as tablets 2543e52347bdSJani Nikula mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 2544e52347bdSJani Nikula reporting absolute coordinates, such as tablets 2545e52347bdSJani Nikula 2546a5c6d650SDavid Rientjes movablecore= [KNL,X86,IA-64,PPC] 2547a5c6d650SDavid Rientjes Format: nn[KMGTPE] | nn% 2548a5c6d650SDavid Rientjes This parameter is the complement to kernelcore=, it 2549a5c6d650SDavid Rientjes specifies the amount of memory used for migratable 2550a5c6d650SDavid Rientjes allocations. If both kernelcore and movablecore is 2551a5c6d650SDavid Rientjes specified, then kernelcore will be at *least* the 2552a5c6d650SDavid Rientjes specified value but may be more. If movablecore on its 2553a5c6d650SDavid Rientjes own is specified, the administrator must be careful 2554e52347bdSJani Nikula that the amount of memory usable for all allocations 2555e52347bdSJani Nikula is not too small. 2556e52347bdSJani Nikula 2557f70029bbSMichal Hocko movable_node [KNL] Boot-time switch to make hotplugable memory 2558f70029bbSMichal Hocko NUMA nodes to be movable. This means that the memory 2559f70029bbSMichal Hocko of such nodes will be usable only for movable 2560f70029bbSMichal Hocko allocations which rules out almost all kernel 2561f70029bbSMichal Hocko allocations. Use with caution! 2562e52347bdSJani Nikula 2563e52347bdSJani Nikula MTD_Partition= [MTD] 2564e52347bdSJani Nikula Format: <name>,<region-number>,<size>,<offset> 2565e52347bdSJani Nikula 2566e52347bdSJani Nikula MTD_Region= [MTD] Format: 2567e52347bdSJani Nikula <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 2568e52347bdSJani Nikula 2569e52347bdSJani Nikula mtdparts= [MTD] 2570e52347bdSJani Nikula See drivers/mtd/cmdlinepart.c. 2571e52347bdSJani Nikula 2572e52347bdSJani Nikula multitce=off [PPC] This parameter disables the use of the pSeries 2573e52347bdSJani Nikula firmware feature for updating multiple TCE entries 2574e52347bdSJani Nikula at a time. 2575e52347bdSJani Nikula 2576e52347bdSJani Nikula onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration 2577e52347bdSJani Nikula 2578e52347bdSJani Nikula Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] 2579e52347bdSJani Nikula 2580e52347bdSJani Nikula boundary - index of last SLC block on Flex-OneNAND. 2581e52347bdSJani Nikula The remaining blocks are configured as MLC blocks. 2582e52347bdSJani Nikula lock - Configure if Flex-OneNAND boundary should be locked. 2583e52347bdSJani Nikula Once locked, the boundary cannot be changed. 2584e52347bdSJani Nikula 1 indicates lock status, 0 indicates unlock status. 2585e52347bdSJani Nikula 2586e52347bdSJani Nikula mtdset= [ARM] 2587e52347bdSJani Nikula ARM/S3C2412 JIVE boot control 2588e52347bdSJani Nikula 2589e52347bdSJani Nikula See arch/arm/mach-s3c2412/mach-jive.c 2590e52347bdSJani Nikula 2591e52347bdSJani Nikula mtouchusb.raw_coordinates= 2592e52347bdSJani Nikula [HW] Make the MicroTouch USB driver use raw coordinates 2593e52347bdSJani Nikula ('y', default) or cooked coordinates ('n') 2594e52347bdSJani Nikula 2595e52347bdSJani Nikula mtrr_chunk_size=nn[KMG] [X86] 2596e52347bdSJani Nikula used for mtrr cleanup. It is largest continuous chunk 2597e52347bdSJani Nikula that could hold holes aka. UC entries. 2598e52347bdSJani Nikula 2599e52347bdSJani Nikula mtrr_gran_size=nn[KMG] [X86] 2600e52347bdSJani Nikula Used for mtrr cleanup. It is granularity of mtrr block. 2601e52347bdSJani Nikula Default is 1. 2602e52347bdSJani Nikula Large value could prevent small alignment from 2603e52347bdSJani Nikula using up MTRRs. 2604e52347bdSJani Nikula 2605e52347bdSJani Nikula mtrr_spare_reg_nr=n [X86] 2606e52347bdSJani Nikula Format: <integer> 2607e52347bdSJani Nikula Range: 0,7 : spare reg number 2608e52347bdSJani Nikula Default : 1 2609e52347bdSJani Nikula Used for mtrr cleanup. It is spare mtrr entries number. 2610e52347bdSJani Nikula Set to 2 or more if your graphical card needs more. 2611e52347bdSJani Nikula 2612e52347bdSJani Nikula n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 2613e52347bdSJani Nikula 2614e52347bdSJani Nikula netdev= [NET] Network devices parameters 2615e52347bdSJani Nikula Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 2616e52347bdSJani Nikula Note that mem_start is often overloaded to mean 2617e52347bdSJani Nikula something different and driver-specific. 2618e52347bdSJani Nikula This usage is only documented in each driver source 2619e52347bdSJani Nikula file if at all. 2620e52347bdSJani Nikula 2621e52347bdSJani Nikula nf_conntrack.acct= 2622e52347bdSJani Nikula [NETFILTER] Enable connection tracking flow accounting 2623e52347bdSJani Nikula 0 to disable accounting 2624e52347bdSJani Nikula 1 to enable accounting 2625e52347bdSJani Nikula Default value is 0. 2626e52347bdSJani Nikula 2627e52347bdSJani Nikula nfsaddrs= [NFS] Deprecated. Use ip= instead. 2628e52347bdSJani Nikula See Documentation/filesystems/nfs/nfsroot.txt. 2629e52347bdSJani Nikula 2630e52347bdSJani Nikula nfsroot= [NFS] nfs root filesystem for disk-less boxes. 2631e52347bdSJani Nikula See Documentation/filesystems/nfs/nfsroot.txt. 2632e52347bdSJani Nikula 2633e52347bdSJani Nikula nfsrootdebug [NFS] enable nfsroot debugging messages. 2634e52347bdSJani Nikula See Documentation/filesystems/nfs/nfsroot.txt. 2635e52347bdSJani Nikula 2636e52347bdSJani Nikula nfs.callback_nr_threads= 2637e52347bdSJani Nikula [NFSv4] set the total number of threads that the 2638e52347bdSJani Nikula NFS client will assign to service NFSv4 callback 2639e52347bdSJani Nikula requests. 2640e52347bdSJani Nikula 2641e52347bdSJani Nikula nfs.callback_tcpport= 2642e52347bdSJani Nikula [NFS] set the TCP port on which the NFSv4 callback 2643e52347bdSJani Nikula channel should listen. 2644e52347bdSJani Nikula 2645e52347bdSJani Nikula nfs.cache_getent= 2646e52347bdSJani Nikula [NFS] sets the pathname to the program which is used 2647e52347bdSJani Nikula to update the NFS client cache entries. 2648e52347bdSJani Nikula 2649e52347bdSJani Nikula nfs.cache_getent_timeout= 2650e52347bdSJani Nikula [NFS] sets the timeout after which an attempt to 2651e52347bdSJani Nikula update a cache entry is deemed to have failed. 2652e52347bdSJani Nikula 2653e52347bdSJani Nikula nfs.idmap_cache_timeout= 2654e52347bdSJani Nikula [NFS] set the maximum lifetime for idmapper cache 2655e52347bdSJani Nikula entries. 2656e52347bdSJani Nikula 2657e52347bdSJani Nikula nfs.enable_ino64= 2658e52347bdSJani Nikula [NFS] enable 64-bit inode numbers. 2659e52347bdSJani Nikula If zero, the NFS client will fake up a 32-bit inode 2660e52347bdSJani Nikula number for the readdir() and stat() syscalls instead 2661e52347bdSJani Nikula of returning the full 64-bit number. 2662e52347bdSJani Nikula The default is to return 64-bit inode numbers. 2663e52347bdSJani Nikula 2664e52347bdSJani Nikula nfs.max_session_cb_slots= 2665e52347bdSJani Nikula [NFSv4.1] Sets the maximum number of session 2666e52347bdSJani Nikula slots the client will assign to the callback 2667e52347bdSJani Nikula channel. This determines the maximum number of 2668e52347bdSJani Nikula callbacks the client will process in parallel for 2669e52347bdSJani Nikula a particular server. 2670e52347bdSJani Nikula 2671e52347bdSJani Nikula nfs.max_session_slots= 2672e52347bdSJani Nikula [NFSv4.1] Sets the maximum number of session slots 2673e52347bdSJani Nikula the client will attempt to negotiate with the server. 2674e52347bdSJani Nikula This limits the number of simultaneous RPC requests 2675e52347bdSJani Nikula that the client can send to the NFSv4.1 server. 2676e52347bdSJani Nikula Note that there is little point in setting this 2677e52347bdSJani Nikula value higher than the max_tcp_slot_table_limit. 2678e52347bdSJani Nikula 2679e52347bdSJani Nikula nfs.nfs4_disable_idmapping= 2680e52347bdSJani Nikula [NFSv4] When set to the default of '1', this option 2681e52347bdSJani Nikula ensures that both the RPC level authentication 2682e52347bdSJani Nikula scheme and the NFS level operations agree to use 2683e52347bdSJani Nikula numeric uids/gids if the mount is using the 2684e52347bdSJani Nikula 'sec=sys' security flavour. In effect it is 2685e52347bdSJani Nikula disabling idmapping, which can make migration from 2686e52347bdSJani Nikula legacy NFSv2/v3 systems to NFSv4 easier. 2687e52347bdSJani Nikula Servers that do not support this mode of operation 2688e52347bdSJani Nikula will be autodetected by the client, and it will fall 2689e52347bdSJani Nikula back to using the idmapper. 2690e52347bdSJani Nikula To turn off this behaviour, set the value to '0'. 2691e52347bdSJani Nikula nfs.nfs4_unique_id= 2692e52347bdSJani Nikula [NFS4] Specify an additional fixed unique ident- 2693e52347bdSJani Nikula ification string that NFSv4 clients can insert into 2694e52347bdSJani Nikula their nfs_client_id4 string. This is typically a 2695e52347bdSJani Nikula UUID that is generated at system install time. 2696e52347bdSJani Nikula 2697e52347bdSJani Nikula nfs.send_implementation_id = 2698e52347bdSJani Nikula [NFSv4.1] Send client implementation identification 2699e52347bdSJani Nikula information in exchange_id requests. 2700e52347bdSJani Nikula If zero, no implementation identification information 2701e52347bdSJani Nikula will be sent. 2702e52347bdSJani Nikula The default is to send the implementation identification 2703e52347bdSJani Nikula information. 2704e52347bdSJani Nikula 2705e52347bdSJani Nikula nfs.recover_lost_locks = 2706e52347bdSJani Nikula [NFSv4] Attempt to recover locks that were lost due 2707e52347bdSJani Nikula to a lease timeout on the server. Please note that 2708e52347bdSJani Nikula doing this risks data corruption, since there are 2709e52347bdSJani Nikula no guarantees that the file will remain unchanged 2710e52347bdSJani Nikula after the locks are lost. 2711e52347bdSJani Nikula If you want to enable the kernel legacy behaviour of 2712e52347bdSJani Nikula attempting to recover these locks, then set this 2713e52347bdSJani Nikula parameter to '1'. 2714e52347bdSJani Nikula The default parameter value of '0' causes the kernel 2715e52347bdSJani Nikula not to attempt recovery of lost locks. 2716e52347bdSJani Nikula 2717e52347bdSJani Nikula nfs4.layoutstats_timer = 2718e52347bdSJani Nikula [NFSv4.2] Change the rate at which the kernel sends 2719e52347bdSJani Nikula layoutstats to the pNFS metadata server. 2720e52347bdSJani Nikula 2721e52347bdSJani Nikula Setting this to value to 0 causes the kernel to use 2722e52347bdSJani Nikula whatever value is the default set by the layout 2723e52347bdSJani Nikula driver. A non-zero value sets the minimum interval 2724e52347bdSJani Nikula in seconds between layoutstats transmissions. 2725e52347bdSJani Nikula 2726e52347bdSJani Nikula nfsd.nfs4_disable_idmapping= 2727e52347bdSJani Nikula [NFSv4] When set to the default of '1', the NFSv4 2728e52347bdSJani Nikula server will return only numeric uids and gids to 2729e52347bdSJani Nikula clients using auth_sys, and will accept numeric uids 2730e52347bdSJani Nikula and gids from such clients. This is intended to ease 2731e52347bdSJani Nikula migration from NFSv2/v3. 2732e52347bdSJani Nikula 2733c0c74acbSHans-Christian Noren Egtvedt nmi_debug= [KNL,SH] Specify one or more actions to take 2734e52347bdSJani Nikula when a NMI is triggered. 2735e52347bdSJani Nikula Format: [state][,regs][,debounce][,die] 2736e52347bdSJani Nikula 2737e52347bdSJani Nikula nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels 2738e52347bdSJani Nikula Format: [panic,][nopanic,][num] 2739e52347bdSJani Nikula Valid num: 0 or 1 2740e52347bdSJani Nikula 0 - turn hardlockup detector in nmi_watchdog off 2741e52347bdSJani Nikula 1 - turn hardlockup detector in nmi_watchdog on 2742e52347bdSJani Nikula When panic is specified, panic when an NMI watchdog 2743e52347bdSJani Nikula timeout occurs (or 'nopanic' to override the opposite 2744e52347bdSJani Nikula default). To disable both hard and soft lockup detectors, 2745e52347bdSJani Nikula please see 'nowatchdog'. 2746e52347bdSJani Nikula This is useful when you use a panic=... timeout and 2747e52347bdSJani Nikula need the box quickly up again. 2748e52347bdSJani Nikula 2749d22881dcSScott Wood These settings can be accessed at runtime via 2750d22881dcSScott Wood the nmi_watchdog and hardlockup_panic sysctls. 2751d22881dcSScott Wood 2752e52347bdSJani Nikula netpoll.carrier_timeout= 2753e52347bdSJani Nikula [NET] Specifies amount of time (in seconds) that 2754e52347bdSJani Nikula netpoll should wait for a carrier. By default netpoll 2755e52347bdSJani Nikula waits 4 seconds. 2756e52347bdSJani Nikula 2757e52347bdSJani Nikula no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 2758e52347bdSJani Nikula emulation library even if a 387 maths coprocessor 2759e52347bdSJani Nikula is present. 2760e52347bdSJani Nikula 2761372fddf7SKirill A. Shutemov no5lvl [X86-64] Disable 5-level paging mode. Forces 2762372fddf7SKirill A. Shutemov kernel to use 4-level paging instead. 2763372fddf7SKirill A. Shutemov 2764e52347bdSJani Nikula no_console_suspend 2765e52347bdSJani Nikula [HW] Never suspend the console 2766e52347bdSJani Nikula Disable suspending of consoles during suspend and 2767e52347bdSJani Nikula hibernate operations. Once disabled, debugging 2768e52347bdSJani Nikula messages can reach various consoles while the rest 2769e52347bdSJani Nikula of the system is being put to sleep (ie, while 2770e52347bdSJani Nikula debugging driver suspend/resume hooks). This may 2771e52347bdSJani Nikula not work reliably with all consoles, but is known 2772e52347bdSJani Nikula to work with serial and VGA consoles. 2773e52347bdSJani Nikula To facilitate more flexible debugging, we also add 2774e52347bdSJani Nikula console_suspend, a printk module parameter to control 2775e52347bdSJani Nikula it. Users could use console_suspend (usually 2776e52347bdSJani Nikula /sys/module/printk/parameters/console_suspend) to 2777e52347bdSJani Nikula turn on/off it dynamically. 2778e52347bdSJani Nikula 2779e52347bdSJani Nikula noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 2780e52347bdSJani Nikula caches in the slab allocator. Saves per-node memory, 2781e52347bdSJani Nikula but will impact performance. 2782e52347bdSJani Nikula 2783e52347bdSJani Nikula noalign [KNL,ARM] 2784e52347bdSJani Nikula 2785686140a1SVasily Gorbik noaltinstr [S390] Disables alternative instructions patching 2786686140a1SVasily Gorbik (CPU alternatives feature). 2787686140a1SVasily Gorbik 2788e52347bdSJani Nikula noapic [SMP,APIC] Tells the kernel to not make use of any 2789e52347bdSJani Nikula IOAPICs that may be present in the system. 2790e52347bdSJani Nikula 2791e52347bdSJani Nikula noautogroup Disable scheduler automatic task group creation. 2792e52347bdSJani Nikula 2793e52347bdSJani Nikula nobats [PPC] Do not use BATs for mapping kernel lowmem 2794e52347bdSJani Nikula on "Classic" PPC cores. 2795e52347bdSJani Nikula 2796e52347bdSJani Nikula nocache [ARM] 2797e52347bdSJani Nikula 2798e52347bdSJani Nikula noclflush [BUGS=X86] Don't use the CLFLUSH instruction 2799e52347bdSJani Nikula 2800e52347bdSJani Nikula nodelayacct [KNL] Disable per-task delay accounting 2801e52347bdSJani Nikula 2802e52347bdSJani Nikula nodsp [SH] Disable hardware DSP at boot time. 2803e52347bdSJani Nikula 2804e52347bdSJani Nikula noefi Disable EFI runtime services support. 2805e52347bdSJani Nikula 2806e52347bdSJani Nikula noexec [IA-64] 2807e52347bdSJani Nikula 2808e52347bdSJani Nikula noexec [X86] 2809e52347bdSJani Nikula On X86-32 available only on PAE configured kernels. 2810e52347bdSJani Nikula noexec=on: enable non-executable mappings (default) 2811e52347bdSJani Nikula noexec=off: disable non-executable mappings 2812e52347bdSJani Nikula 2813e52347bdSJani Nikula nosmap [X86] 2814e52347bdSJani Nikula Disable SMAP (Supervisor Mode Access Prevention) 2815e52347bdSJani Nikula even if it is supported by processor. 2816e52347bdSJani Nikula 2817e52347bdSJani Nikula nosmep [X86] 2818e52347bdSJani Nikula Disable SMEP (Supervisor Mode Execution Prevention) 2819e52347bdSJani Nikula even if it is supported by processor. 2820e52347bdSJani Nikula 2821e52347bdSJani Nikula noexec32 [X86-64] 2822e52347bdSJani Nikula This affects only 32-bit executables. 2823e52347bdSJani Nikula noexec32=on: enable non-executable mappings (default) 2824e52347bdSJani Nikula read doesn't imply executable mappings 2825e52347bdSJani Nikula noexec32=off: disable non-executable mappings 2826e52347bdSJani Nikula read implies executable mappings 2827e52347bdSJani Nikula 2828e52347bdSJani Nikula nofpu [MIPS,SH] Disable hardware FPU at boot time. 2829e52347bdSJani Nikula 2830e52347bdSJani Nikula nofxsr [BUGS=X86-32] Disables x86 floating point extended 2831e52347bdSJani Nikula register save and restore. The kernel will only save 2832e52347bdSJani Nikula legacy floating-point registers on task switch. 2833e52347bdSJani Nikula 2834e52347bdSJani Nikula nohugeiomap [KNL,x86] Disable kernel huge I/O mappings. 2835e52347bdSJani Nikula 2836e52347bdSJani Nikula nosmt [KNL,S390] Disable symmetric multithreading (SMT). 2837e52347bdSJani Nikula Equivalent to smt=1. 2838e52347bdSJani Nikula 283905736e4aSThomas Gleixner [KNL,x86] Disable symmetric multithreading (SMT). 2840506a66f3SThomas Gleixner nosmt=force: Force disable SMT, cannot be undone 2841506a66f3SThomas Gleixner via the sysfs control file. 284205736e4aSThomas Gleixner 284326cb1f36SDiana Craciun nospectre_v1 [PPC] Disable mitigations for Spectre Variant 1 (bounds 284426cb1f36SDiana Craciun check bypass). With this option data leaks are possible 284526cb1f36SDiana Craciun in the system. 284626cb1f36SDiana Craciun 2847e59f5bd7SDiana Craciun nospectre_v2 [X86,PPC_FSL_BOOK3E] Disable all mitigations for the Spectre variant 2 2848da285121SDavid Woodhouse (indirect branch prediction) vulnerability. System may 2849da285121SDavid Woodhouse allow data leaks with this option, which is equivalent 2850da285121SDavid Woodhouse to spectre_v2=off. 2851da285121SDavid Woodhouse 285224f7fc83SKonrad Rzeszutek Wilk nospec_store_bypass_disable 285324f7fc83SKonrad Rzeszutek Wilk [HW] Disable all mitigations for the Speculative Store Bypass vulnerability 285424f7fc83SKonrad Rzeszutek Wilk 2855e52347bdSJani Nikula noxsave [BUGS=X86] Disables x86 extended register state save 2856e52347bdSJani Nikula and restore using xsave. The kernel will fallback to 2857e52347bdSJani Nikula enabling legacy floating-point and sse state. 2858e52347bdSJani Nikula 2859e52347bdSJani Nikula noxsaveopt [X86] Disables xsaveopt used in saving x86 extended 2860e52347bdSJani Nikula register states. The kernel will fall back to use 2861e52347bdSJani Nikula xsave to save the states. By using this parameter, 2862e52347bdSJani Nikula performance of saving the states is degraded because 2863e52347bdSJani Nikula xsave doesn't support modified optimization while 2864e52347bdSJani Nikula xsaveopt supports it on xsaveopt enabled systems. 2865e52347bdSJani Nikula 2866e52347bdSJani Nikula noxsaves [X86] Disables xsaves and xrstors used in saving and 2867e52347bdSJani Nikula restoring x86 extended register state in compacted 2868e52347bdSJani Nikula form of xsave area. The kernel will fall back to use 2869e52347bdSJani Nikula xsaveopt and xrstor to save and restore the states 2870e52347bdSJani Nikula in standard form of xsave area. By using this 2871e52347bdSJani Nikula parameter, xsave area per process might occupy more 2872e52347bdSJani Nikula memory on xsaves enabled systems. 2873e52347bdSJani Nikula 2874e52347bdSJani Nikula nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or 2875e52347bdSJani Nikula wfi(ARM) instruction doesn't work correctly and not to 2876e52347bdSJani Nikula use it. This is also useful when using JTAG debugger. 2877e52347bdSJani Nikula 2878e52347bdSJani Nikula no_file_caps Tells the kernel not to honor file capabilities. The 2879e52347bdSJani Nikula only way then for a file to be executed with privilege 2880e52347bdSJani Nikula is to be setuid root or executed by root. 2881e52347bdSJani Nikula 2882e52347bdSJani Nikula nohalt [IA-64] Tells the kernel not to use the power saving 2883e52347bdSJani Nikula function PAL_HALT_LIGHT when idle. This increases 2884e52347bdSJani Nikula power-consumption. On the positive side, it reduces 2885e52347bdSJani Nikula interrupt wake-up latency, which may improve performance 2886e52347bdSJani Nikula in certain environments such as networked servers or 2887e52347bdSJani Nikula real-time systems. 2888e52347bdSJani Nikula 2889e52347bdSJani Nikula nohibernate [HIBERNATION] Disable hibernation and resume. 2890e52347bdSJani Nikula 2891e52347bdSJani Nikula nohz= [KNL] Boottime enable/disable dynamic ticks 2892e52347bdSJani Nikula Valid arguments: on, off 2893e52347bdSJani Nikula Default: on 2894e52347bdSJani Nikula 2895d94d1053SFrederic Weisbecker nohz_full= [KNL,BOOT,SMP,ISOL] 2896e52347bdSJani Nikula The argument is a cpu list, as described above. 2897e52347bdSJani Nikula In kernels built with CONFIG_NO_HZ_FULL=y, set 2898e52347bdSJani Nikula the specified list of CPUs whose tick will be stopped 2899e52347bdSJani Nikula whenever possible. The boot CPU will be forced outside 2900f99bcb2cSPaul E. McKenney the range to maintain the timekeeping. Any CPUs 2901f99bcb2cSPaul E. McKenney in this list will have their RCU callbacks offloaded, 2902f99bcb2cSPaul E. McKenney just as if they had also been called out in the 2903f99bcb2cSPaul E. McKenney rcu_nocbs= boot parameter. 2904e52347bdSJani Nikula 2905e52347bdSJani Nikula noiotrap [SH] Disables trapped I/O port accesses. 2906e52347bdSJani Nikula 2907e52347bdSJani Nikula noirqdebug [X86-32] Disables the code which attempts to detect and 2908e52347bdSJani Nikula disable unhandled interrupt sources. 2909e52347bdSJani Nikula 2910e52347bdSJani Nikula no_timer_check [X86,APIC] Disables the code which tests for 2911e52347bdSJani Nikula broken timer IRQ sources. 2912e52347bdSJani Nikula 2913e52347bdSJani Nikula noisapnp [ISAPNP] Disables ISA PnP code. 2914e52347bdSJani Nikula 2915e52347bdSJani Nikula noinitrd [RAM] Tells the kernel not to load any configured 2916e52347bdSJani Nikula initial RAM disk. 2917e52347bdSJani Nikula 2918e52347bdSJani Nikula nointremap [X86-64, Intel-IOMMU] Do not enable interrupt 2919e52347bdSJani Nikula remapping. 2920e52347bdSJani Nikula [Deprecated - use intremap=off] 2921e52347bdSJani Nikula 2922e52347bdSJani Nikula nointroute [IA-64] 2923e52347bdSJani Nikula 2924e52347bdSJani Nikula noinvpcid [X86] Disable the INVPCID cpu feature. 2925e52347bdSJani Nikula 2926e52347bdSJani Nikula nojitter [IA-64] Disables jitter checking for ITC timers. 2927e52347bdSJani Nikula 2928e52347bdSJani Nikula no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver 2929e52347bdSJani Nikula 2930e52347bdSJani Nikula no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page 2931e52347bdSJani Nikula fault handling. 2932e52347bdSJani Nikula 2933e7aa8c2eSLinus Torvalds no-vmw-sched-clock 2934e7aa8c2eSLinus Torvalds [X86,PV_OPS] Disable paravirtualized VMware scheduler 2935e7aa8c2eSLinus Torvalds clock and use the default one. 2936e7aa8c2eSLinus Torvalds 2937e52347bdSJani Nikula no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting. 2938e52347bdSJani Nikula steal time is computed, but won't influence scheduler 2939e52347bdSJani Nikula behaviour 2940e52347bdSJani Nikula 2941e52347bdSJani Nikula nolapic [X86-32,APIC] Do not enable or use the local APIC. 2942e52347bdSJani Nikula 2943e52347bdSJani Nikula nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 2944e52347bdSJani Nikula 2945e52347bdSJani Nikula noltlbs [PPC] Do not use large page/tlb entries for kernel 2946e52347bdSJani Nikula lowmem mapping on PPC40x and PPC8xx 2947e52347bdSJani Nikula 2948e52347bdSJani Nikula nomca [IA-64] Disable machine check abort handling 2949e52347bdSJani Nikula 2950e52347bdSJani Nikula nomce [X86-32] Disable Machine Check Exception 2951e52347bdSJani Nikula 2952e52347bdSJani Nikula nomfgpt [X86-32] Disable Multi-Function General Purpose 2953e52347bdSJani Nikula Timer usage (for AMD Geode machines). 2954e52347bdSJani Nikula 2955e52347bdSJani Nikula nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to 2956e52347bdSJani Nikula shutdown the other cpus. Instead use the REBOOT_VECTOR 2957e52347bdSJani Nikula irq. 2958e52347bdSJani Nikula 2959e52347bdSJani Nikula nomodule Disable module load 2960e52347bdSJani Nikula 2961e52347bdSJani Nikula nopat [X86] Disable PAT (page attribute table extension of 2962e52347bdSJani Nikula pagetables) support. 2963e52347bdSJani Nikula 29640790c9aaSAndy Lutomirski nopcid [X86-64] Disable the PCID cpu feature. 29650790c9aaSAndy Lutomirski 2966e52347bdSJani Nikula norandmaps Don't use address space randomization. Equivalent to 2967e52347bdSJani Nikula echo 0 > /proc/sys/kernel/randomize_va_space 2968e52347bdSJani Nikula 2969e52347bdSJani Nikula noreplace-smp [X86-32,SMP] Don't replace SMP instructions 2970e52347bdSJani Nikula with UP alternatives 2971e52347bdSJani Nikula 2972e52347bdSJani Nikula nordrand [X86] Disable kernel use of the RDRAND and 2973e52347bdSJani Nikula RDSEED instructions even if they are supported 2974e52347bdSJani Nikula by the processor. RDRAND and RDSEED are still 2975e52347bdSJani Nikula available to user space applications. 2976e52347bdSJani Nikula 2977e52347bdSJani Nikula noresume [SWSUSP] Disables resume and restores original swap 2978e52347bdSJani Nikula space. 2979e52347bdSJani Nikula 2980e52347bdSJani Nikula no-scroll [VGA] Disables scrollback. 2981e52347bdSJani Nikula This is required for the Braillex ib80-piezo Braille 2982e52347bdSJani Nikula reader made by F.H. Papenmeier (Germany). 2983e52347bdSJani Nikula 2984e52347bdSJani Nikula nosbagart [IA-64] 2985e52347bdSJani Nikula 2986e52347bdSJani Nikula nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 2987e52347bdSJani Nikula 2988e52347bdSJani Nikula nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 2989e52347bdSJani Nikula and disable the IO APIC. legacy for "maxcpus=0". 2990e52347bdSJani Nikula 2991e52347bdSJani Nikula nosoftlockup [KNL] Disable the soft-lockup detector. 2992e52347bdSJani Nikula 2993e52347bdSJani Nikula nosync [HW,M68K] Disables sync negotiation for all devices. 2994e52347bdSJani Nikula 2995e52347bdSJani Nikula nowatchdog [KNL] Disable both lockup detectors, i.e. 2996e52347bdSJani Nikula soft-lockup and NMI watchdog (hard-lockup). 2997e52347bdSJani Nikula 2998e52347bdSJani Nikula nowb [ARM] 2999e52347bdSJani Nikula 3000e52347bdSJani Nikula nox2apic [X86-64,APIC] Do not enable x2APIC mode. 3001e52347bdSJani Nikula 3002e52347bdSJani Nikula cpu0_hotplug [X86] Turn on CPU0 hotplug feature when 3003e52347bdSJani Nikula CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. 3004e52347bdSJani Nikula Some features depend on CPU0. Known dependencies are: 3005e52347bdSJani Nikula 1. Resume from suspend/hibernate depends on CPU0. 3006e52347bdSJani Nikula Suspend/hibernate will fail if CPU0 is offline and you 3007e52347bdSJani Nikula need to online CPU0 before suspend/hibernate. 3008e52347bdSJani Nikula 2. PIC interrupts also depend on CPU0. CPU0 can't be 3009e52347bdSJani Nikula removed if a PIC interrupt is detected. 3010e52347bdSJani Nikula It's said poweroff/reboot may depend on CPU0 on some 3011e52347bdSJani Nikula machines although I haven't seen such issues so far 3012e52347bdSJani Nikula after CPU0 is offline on a few tested machines. 3013e52347bdSJani Nikula If the dependencies are under your control, you can 3014e52347bdSJani Nikula turn on cpu0_hotplug. 3015e52347bdSJani Nikula 301635b55ef2SNoam Camus nps_mtm_hs_ctr= [KNL,ARC] 301735b55ef2SNoam Camus This parameter sets the maximum duration, in 301835b55ef2SNoam Camus cycles, each HW thread of the CTOP can run 301935b55ef2SNoam Camus without interruptions, before HW switches it. 302035b55ef2SNoam Camus The actual maximum duration is 16 times this 302135b55ef2SNoam Camus parameter's value. 302235b55ef2SNoam Camus Format: integer between 1 and 255 302335b55ef2SNoam Camus Default: 255 302435b55ef2SNoam Camus 3025e52347bdSJani Nikula nptcg= [IA-64] Override max number of concurrent global TLB 3026e52347bdSJani Nikula purges which is reported from either PAL_VM_SUMMARY or 3027e52347bdSJani Nikula SAL PALO. 3028e52347bdSJani Nikula 3029e52347bdSJani Nikula nr_cpus= [SMP] Maximum number of processors that an SMP kernel 3030e52347bdSJani Nikula could support. nr_cpus=n : n >= 1 limits the kernel to 3031e52347bdSJani Nikula support 'n' processors. It could be larger than the 3032e52347bdSJani Nikula number of already plugged CPU during bootup, later in 3033e52347bdSJani Nikula runtime you can physically add extra cpu until it reaches 3034e52347bdSJani Nikula n. So during boot up some boot time memory for per-cpu 3035e52347bdSJani Nikula variables need be pre-allocated for later physical cpu 3036e52347bdSJani Nikula hot plugging. 3037e52347bdSJani Nikula 3038e52347bdSJani Nikula nr_uarts= [SERIAL] maximum number of UARTs to be registered. 3039e52347bdSJani Nikula 3040e52347bdSJani Nikula numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing. 3041e52347bdSJani Nikula Allowed values are enable and disable 3042e52347bdSJani Nikula 3043e52347bdSJani Nikula numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 3044c9bff3eeSMichal Hocko 'node', 'default' can be specified 3045e52347bdSJani Nikula This can be set from sysctl after boot. 3046e52347bdSJani Nikula See Documentation/sysctl/vm.txt for details. 3047e52347bdSJani Nikula 3048e52347bdSJani Nikula ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. 3049e52347bdSJani Nikula See Documentation/debugging-via-ohci1394.txt for more 3050e52347bdSJani Nikula info. 3051e52347bdSJani Nikula 3052e52347bdSJani Nikula olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 3053e52347bdSJani Nikula Rather than timing out after 20 ms if an EC 3054e52347bdSJani Nikula command is not properly ACKed, override the length 3055e52347bdSJani Nikula of the timeout. We have interrupts disabled while 3056e52347bdSJani Nikula waiting for the ACK, so if this is set too high 3057e52347bdSJani Nikula interrupts *may* be lost! 3058e52347bdSJani Nikula 3059e52347bdSJani Nikula omap_mux= [OMAP] Override bootloader pin multiplexing. 3060e52347bdSJani Nikula Format: <mux_mode0.mode_name=value>... 3061e52347bdSJani Nikula For example, to override I2C bus2: 3062e52347bdSJani Nikula omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 3063e52347bdSJani Nikula 3064e52347bdSJani Nikula oprofile.timer= [HW] 3065e52347bdSJani Nikula Use timer interrupt instead of performance counters 3066e52347bdSJani Nikula 3067e52347bdSJani Nikula oprofile.cpu_type= Force an oprofile cpu type 3068e52347bdSJani Nikula This might be useful if you have an older oprofile 3069e52347bdSJani Nikula userland or if you want common events. 3070e52347bdSJani Nikula Format: { arch_perfmon } 3071e52347bdSJani Nikula arch_perfmon: [X86] Force use of architectural 3072e52347bdSJani Nikula perfmon on Intel CPUs instead of the 3073e52347bdSJani Nikula CPU specific event set. 3074e52347bdSJani Nikula timer: [X86] Force use of architectural NMI 3075e52347bdSJani Nikula timer mode (see also oprofile.timer 3076e52347bdSJani Nikula for generic hr timer mode) 3077e52347bdSJani Nikula 3078e52347bdSJani Nikula oops=panic Always panic on oopses. Default is to just kill the 3079e52347bdSJani Nikula process, but there is a small probability of 3080e52347bdSJani Nikula deadlocking the machine. 3081e52347bdSJani Nikula This will also cause panics on machine check exceptions. 3082e52347bdSJani Nikula Useful together with panic=30 to trigger a reboot. 3083e52347bdSJani Nikula 3084e52347bdSJani Nikula page_owner= [KNL] Boot-time page_owner enabling option. 3085e52347bdSJani Nikula Storage of the information about who allocated 3086e52347bdSJani Nikula each page is disabled in default. With this switch, 3087e52347bdSJani Nikula we can turn it on. 3088e52347bdSJani Nikula on: enable the feature 3089e52347bdSJani Nikula 3090e52347bdSJani Nikula page_poison= [KNL] Boot-time parameter changing the state of 30918c9a134cSKees Cook poisoning on the buddy allocator, available with 30928c9a134cSKees Cook CONFIG_PAGE_POISONING=y. 30938c9a134cSKees Cook off: turn off poisoning (default) 3094e52347bdSJani Nikula on: turn on poisoning 3095e52347bdSJani Nikula 3096e52347bdSJani Nikula panic= [KNL] Kernel behaviour on panic: delay <timeout> 3097e52347bdSJani Nikula timeout > 0: seconds before rebooting 3098e52347bdSJani Nikula timeout = 0: wait forever 3099e52347bdSJani Nikula timeout < 0: reboot immediately 3100e52347bdSJani Nikula Format: <timeout> 3101e52347bdSJani Nikula 3102d999bd93SFeng Tang panic_print= Bitmask for printing system info when panic happens. 3103d999bd93SFeng Tang User can chose combination of the following bits: 3104d999bd93SFeng Tang bit 0: print all tasks info 3105d999bd93SFeng Tang bit 1: print system memory info 3106d999bd93SFeng Tang bit 2: print timer info 3107d999bd93SFeng Tang bit 3: print locks info if CONFIG_LOCKDEP is on 3108d999bd93SFeng Tang bit 4: print ftrace buffer 3109d999bd93SFeng Tang 3110e52347bdSJani Nikula panic_on_warn panic() instead of WARN(). Useful to cause kdump 3111e52347bdSJani Nikula on a WARN(). 3112e52347bdSJani Nikula 3113e52347bdSJani Nikula crash_kexec_post_notifiers 3114e52347bdSJani Nikula Run kdump after running panic-notifiers and dumping 3115e52347bdSJani Nikula kmsg. This only for the users who doubt kdump always 3116e52347bdSJani Nikula succeeds in any situation. 3117e52347bdSJani Nikula Note that this also increases risks of kdump failure, 3118e52347bdSJani Nikula because some panic notifiers can make the crashed 3119e52347bdSJani Nikula kernel more unstable. 3120e52347bdSJani Nikula 3121e52347bdSJani Nikula parkbd.port= [HW] Parallel port number the keyboard adapter is 3122e52347bdSJani Nikula connected to, default is 0. 3123e52347bdSJani Nikula Format: <parport#> 3124e52347bdSJani Nikula parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 3125e52347bdSJani Nikula 0 for XT, 1 for AT (default is AT). 3126e52347bdSJani Nikula Format: <mode> 3127e52347bdSJani Nikula 3128e52347bdSJani Nikula parport= [HW,PPT] Specify parallel ports. 0 disables. 3129e52347bdSJani Nikula Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 3130e52347bdSJani Nikula Use 'auto' to force the driver to use any 3131e52347bdSJani Nikula IRQ/DMA settings detected (the default is to 3132e52347bdSJani Nikula ignore detected IRQ/DMA settings because of 3133e52347bdSJani Nikula possible conflicts). You can specify the base 3134e52347bdSJani Nikula address, IRQ, and DMA settings; IRQ and DMA 3135e52347bdSJani Nikula should be numbers, or 'auto' (for using detected 3136e52347bdSJani Nikula settings on that particular port), or 'nofifo' 3137e52347bdSJani Nikula (to avoid using a FIFO even if it is detected). 3138e52347bdSJani Nikula Parallel ports are assigned in the order they 3139e52347bdSJani Nikula are specified on the command line, starting 3140e52347bdSJani Nikula with parport0. 3141e52347bdSJani Nikula 3142e52347bdSJani Nikula parport_init_mode= [HW,PPT] 3143e52347bdSJani Nikula Configure VIA parallel port to operate in 3144e52347bdSJani Nikula a specific mode. This is necessary on Pegasos 3145e52347bdSJani Nikula computer where firmware has no options for setting 3146e52347bdSJani Nikula up parallel port mode and sets it to spp. 3147e52347bdSJani Nikula Currently this function knows 686a and 8231 chips. 3148e52347bdSJani Nikula Format: [spp|ps2|epp|ecp|ecpepp] 3149e52347bdSJani Nikula 3150e52347bdSJani Nikula pause_on_oops= 3151e52347bdSJani Nikula Halt all CPUs after the first oops has been printed for 3152e52347bdSJani Nikula the specified number of seconds. This is to be used if 3153e52347bdSJani Nikula your oopses keep scrolling off the screen. 3154e52347bdSJani Nikula 3155e52347bdSJani Nikula pcbit= [HW,ISDN] 3156e52347bdSJani Nikula 3157e52347bdSJani Nikula pcd. [PARIDE] 3158e52347bdSJani Nikula See header of drivers/block/paride/pcd.c. 3159e52347bdSJani Nikula See also Documentation/blockdev/paride.txt. 3160e52347bdSJani Nikula 316107d8d7e5SLogan Gunthorpe pci=option[,option...] [PCI] various PCI subsystem options. 316207d8d7e5SLogan Gunthorpe 316307d8d7e5SLogan Gunthorpe Some options herein operate on a specific device 316407d8d7e5SLogan Gunthorpe or a set of devices (<pci_dev>). These are 316507d8d7e5SLogan Gunthorpe specified in one of the following formats: 316607d8d7e5SLogan Gunthorpe 316745db3370SLogan Gunthorpe [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]* 316807d8d7e5SLogan Gunthorpe pci:<vendor>:<device>[:<subvendor>:<subdevice>] 316907d8d7e5SLogan Gunthorpe 317007d8d7e5SLogan Gunthorpe Note: the first format specifies a PCI 317107d8d7e5SLogan Gunthorpe bus/device/function address which may change 317207d8d7e5SLogan Gunthorpe if new hardware is inserted, if motherboard 317307d8d7e5SLogan Gunthorpe firmware changes, or due to changes caused 317407d8d7e5SLogan Gunthorpe by other kernel parameters. If the 317507d8d7e5SLogan Gunthorpe domain is left unspecified, it is 317645db3370SLogan Gunthorpe taken to be zero. Optionally, a path 317745db3370SLogan Gunthorpe to a device through multiple device/function 317845db3370SLogan Gunthorpe addresses can be specified after the base 317945db3370SLogan Gunthorpe address (this is more robust against 318045db3370SLogan Gunthorpe renumbering issues). The second format 318107d8d7e5SLogan Gunthorpe selects devices using IDs from the 318207d8d7e5SLogan Gunthorpe configuration space which may match multiple 318307d8d7e5SLogan Gunthorpe devices in the system. 318407d8d7e5SLogan Gunthorpe 318511eb0e0eSSinan Kaya earlydump dump PCI config space before the kernel 3186e52347bdSJani Nikula changes anything 3187e52347bdSJani Nikula off [X86] don't probe for the PCI bus 3188e52347bdSJani Nikula bios [X86-32] force use of PCI BIOS, don't access 3189e52347bdSJani Nikula the hardware directly. Use this if your machine 3190e52347bdSJani Nikula has a non-standard PCI host bridge. 3191e52347bdSJani Nikula nobios [X86-32] disallow use of PCI BIOS, only direct 3192e52347bdSJani Nikula hardware access methods are allowed. Use this 3193e52347bdSJani Nikula if you experience crashes upon bootup and you 3194e52347bdSJani Nikula suspect they are caused by the BIOS. 3195e52347bdSJani Nikula conf1 [X86] Force use of PCI Configuration Access 3196e52347bdSJani Nikula Mechanism 1 (config address in IO port 0xCF8, 3197e52347bdSJani Nikula data in IO port 0xCFC, both 32-bit). 3198e52347bdSJani Nikula conf2 [X86] Force use of PCI Configuration Access 3199e52347bdSJani Nikula Mechanism 2 (IO port 0xCF8 is an 8-bit port for 3200e52347bdSJani Nikula the function, IO port 0xCFA, also 8-bit, sets 3201e52347bdSJani Nikula bus number. The config space is then accessed 3202e52347bdSJani Nikula through ports 0xC000-0xCFFF). 3203e52347bdSJani Nikula See http://wiki.osdev.org/PCI for more info 3204e52347bdSJani Nikula on the configuration access mechanisms. 3205e52347bdSJani Nikula noaer [PCIE] If the PCIEAER kernel config parameter is 3206e52347bdSJani Nikula enabled, this kernel boot option can be used to 3207e52347bdSJani Nikula disable the use of PCIE advanced error reporting. 3208e52347bdSJani Nikula nodomains [PCI] Disable support for multiple PCI 3209e52347bdSJani Nikula root domains (aka PCI segments, in ACPI-speak). 3210e52347bdSJani Nikula nommconf [X86] Disable use of MMCONFIG for PCI 3211e52347bdSJani Nikula Configuration 3212e52347bdSJani Nikula check_enable_amd_mmconf [X86] check for and enable 3213e52347bdSJani Nikula properly configured MMIO access to PCI 3214e52347bdSJani Nikula config space on AMD family 10h CPU 3215e52347bdSJani Nikula nomsi [MSI] If the PCI_MSI kernel config parameter is 3216e52347bdSJani Nikula enabled, this kernel boot option can be used to 3217e52347bdSJani Nikula disable the use of MSI interrupts system-wide. 3218e52347bdSJani Nikula noioapicquirk [APIC] Disable all boot interrupt quirks. 3219e52347bdSJani Nikula Safety option to keep boot IRQs enabled. This 3220e52347bdSJani Nikula should never be necessary. 3221e52347bdSJani Nikula ioapicreroute [APIC] Enable rerouting of boot IRQs to the 3222e52347bdSJani Nikula primary IO-APIC for bridges that cannot disable 3223e52347bdSJani Nikula boot IRQs. This fixes a source of spurious IRQs 3224e52347bdSJani Nikula when the system masks IRQs. 3225e52347bdSJani Nikula noioapicreroute [APIC] Disable workaround that uses the 3226e52347bdSJani Nikula boot IRQ equivalent of an IRQ that connects to 3227e52347bdSJani Nikula a chipset where boot IRQs cannot be disabled. 3228e52347bdSJani Nikula The opposite of ioapicreroute. 3229e52347bdSJani Nikula biosirq [X86-32] Use PCI BIOS calls to get the interrupt 3230e52347bdSJani Nikula routing table. These calls are known to be buggy 3231e52347bdSJani Nikula on several machines and they hang the machine 3232e52347bdSJani Nikula when used, but on other computers it's the only 3233e52347bdSJani Nikula way to get the interrupt routing table. Try 3234e52347bdSJani Nikula this option if the kernel is unable to allocate 3235e52347bdSJani Nikula IRQs or discover secondary PCI buses on your 3236e52347bdSJani Nikula motherboard. 3237e52347bdSJani Nikula rom [X86] Assign address space to expansion ROMs. 3238e52347bdSJani Nikula Use with caution as certain devices share 3239e52347bdSJani Nikula address decoders between ROMs and other 3240e52347bdSJani Nikula resources. 3241e52347bdSJani Nikula norom [X86] Do not assign address space to 3242e52347bdSJani Nikula expansion ROMs that do not already have 3243e52347bdSJani Nikula BIOS assigned address ranges. 3244e52347bdSJani Nikula nobar [X86] Do not assign address space to the 3245e52347bdSJani Nikula BARs that weren't assigned by the BIOS. 3246e52347bdSJani Nikula irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 3247e52347bdSJani Nikula assigned automatically to PCI devices. You can 3248e52347bdSJani Nikula make the kernel exclude IRQs of your ISA cards 3249e52347bdSJani Nikula this way. 3250e52347bdSJani Nikula pirqaddr=0xAAAAA [X86] Specify the physical address 3251e52347bdSJani Nikula of the PIRQ table (normally generated 3252e52347bdSJani Nikula by the BIOS) if it is outside the 3253e52347bdSJani Nikula F0000h-100000h range. 3254e52347bdSJani Nikula lastbus=N [X86] Scan all buses thru bus #N. Can be 3255e52347bdSJani Nikula useful if the kernel is unable to find your 3256e52347bdSJani Nikula secondary buses and you want to tell it 3257e52347bdSJani Nikula explicitly which ones they are. 3258e52347bdSJani Nikula assign-busses [X86] Always assign all PCI bus 3259e52347bdSJani Nikula numbers ourselves, overriding 3260e52347bdSJani Nikula whatever the firmware may have done. 3261e52347bdSJani Nikula usepirqmask [X86] Honor the possible IRQ mask stored 3262e52347bdSJani Nikula in the BIOS $PIR table. This is needed on 3263e52347bdSJani Nikula some systems with broken BIOSes, notably 3264e52347bdSJani Nikula some HP Pavilion N5400 and Omnibook XE3 3265e52347bdSJani Nikula notebooks. This will have no effect if ACPI 3266e52347bdSJani Nikula IRQ routing is enabled. 3267e52347bdSJani Nikula noacpi [X86] Do not use ACPI for IRQ routing 3268e52347bdSJani Nikula or for PCI scanning. 3269e52347bdSJani Nikula use_crs [X86] Use PCI host bridge window information 3270e52347bdSJani Nikula from ACPI. On BIOSes from 2008 or later, this 3271e52347bdSJani Nikula is enabled by default. If you need to use this, 3272e52347bdSJani Nikula please report a bug. 3273e52347bdSJani Nikula nocrs [X86] Ignore PCI host bridge windows from ACPI. 3274e52347bdSJani Nikula If you need to use this, please report a bug. 3275e52347bdSJani Nikula routeirq Do IRQ routing for all PCI devices. 3276e52347bdSJani Nikula This is normally done in pci_enable_device(), 3277e52347bdSJani Nikula so this option is a temporary workaround 3278e52347bdSJani Nikula for broken drivers that don't call it. 3279e52347bdSJani Nikula skip_isa_align [X86] do not align io start addr, so can 3280e52347bdSJani Nikula handle more pci cards 3281e52347bdSJani Nikula noearly [X86] Don't do any early type 1 scanning. 3282e52347bdSJani Nikula This might help on some broken boards which 3283e52347bdSJani Nikula machine check when some devices' config space 3284e52347bdSJani Nikula is read. But various workarounds are disabled 3285e52347bdSJani Nikula and some IOMMU drivers will not work. 3286e52347bdSJani Nikula bfsort Sort PCI devices into breadth-first order. 3287e52347bdSJani Nikula This sorting is done to get a device 3288e52347bdSJani Nikula order compatible with older (<= 2.4) kernels. 3289e52347bdSJani Nikula nobfsort Don't sort PCI devices into breadth-first order. 3290e52347bdSJani Nikula pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) 3291e52347bdSJani Nikula tuning and use the BIOS-configured MPS defaults. 3292e52347bdSJani Nikula pcie_bus_safe Set every device's MPS to the largest value 3293e52347bdSJani Nikula supported by all devices below the root complex. 3294e52347bdSJani Nikula pcie_bus_perf Set device MPS to the largest allowable MPS 3295e52347bdSJani Nikula based on its parent bus. Also set MRRS (Max 3296e52347bdSJani Nikula Read Request Size) to the largest supported 3297e52347bdSJani Nikula value (no larger than the MPS that the device 3298e52347bdSJani Nikula or bus can support) for best performance. 3299e52347bdSJani Nikula pcie_bus_peer2peer Set every device's MPS to 128B, which 3300e52347bdSJani Nikula every device is guaranteed to support. This 3301e52347bdSJani Nikula configuration allows peer-to-peer DMA between 3302e52347bdSJani Nikula any pair of devices, possibly at the cost of 3303e52347bdSJani Nikula reduced performance. This also guarantees 3304e52347bdSJani Nikula that hot-added devices will work. 3305e52347bdSJani Nikula cbiosize=nn[KMG] The fixed amount of bus space which is 3306e52347bdSJani Nikula reserved for the CardBus bridge's IO window. 3307e52347bdSJani Nikula The default value is 256 bytes. 3308e52347bdSJani Nikula cbmemsize=nn[KMG] The fixed amount of bus space which is 3309e52347bdSJani Nikula reserved for the CardBus bridge's memory 3310e52347bdSJani Nikula window. The default value is 64 megabytes. 3311e52347bdSJani Nikula resource_alignment= 3312e52347bdSJani Nikula Format: 331307d8d7e5SLogan Gunthorpe [<order of align>@]<pci_dev>[; ...] 3314e52347bdSJani Nikula Specifies alignment and device to reassign 331507d8d7e5SLogan Gunthorpe aligned memory resources. How to 331607d8d7e5SLogan Gunthorpe specify the device is described above. 3317e52347bdSJani Nikula If <order of align> is not specified, 3318e52347bdSJani Nikula PAGE_SIZE is used as alignment. 3319e52347bdSJani Nikula PCI-PCI bridge can be specified, if resource 3320e52347bdSJani Nikula windows need to be expanded. 3321e52347bdSJani Nikula To specify the alignment for several 3322e52347bdSJani Nikula instances of a device, the PCI vendor, 3323e52347bdSJani Nikula device, subvendor, and subdevice may be 3324e52347bdSJani Nikula specified, e.g., 4096@pci:8086:9c22:103c:198f 3325e52347bdSJani Nikula ecrc= Enable/disable PCIe ECRC (transaction layer 3326e52347bdSJani Nikula end-to-end CRC checking). 3327e52347bdSJani Nikula bios: Use BIOS/firmware settings. This is the 3328e52347bdSJani Nikula the default. 3329e52347bdSJani Nikula off: Turn ECRC off 3330e52347bdSJani Nikula on: Turn ECRC on. 3331e52347bdSJani Nikula hpiosize=nn[KMG] The fixed amount of bus space which is 3332e52347bdSJani Nikula reserved for hotplug bridge's IO window. 3333e52347bdSJani Nikula Default size is 256 bytes. 3334e52347bdSJani Nikula hpmemsize=nn[KMG] The fixed amount of bus space which is 3335e52347bdSJani Nikula reserved for hotplug bridge's memory window. 3336e52347bdSJani Nikula Default size is 2 megabytes. 3337e52347bdSJani Nikula hpbussize=nn The minimum amount of additional bus numbers 3338e52347bdSJani Nikula reserved for buses below a hotplug bridge. 3339e52347bdSJani Nikula Default is 1. 3340e52347bdSJani Nikula realloc= Enable/disable reallocating PCI bridge resources 3341e52347bdSJani Nikula if allocations done by BIOS are too small to 3342e52347bdSJani Nikula accommodate resources required by all child 3343e52347bdSJani Nikula devices. 3344e52347bdSJani Nikula off: Turn realloc off 3345e52347bdSJani Nikula on: Turn realloc on 3346e52347bdSJani Nikula realloc same as realloc=on 3347e52347bdSJani Nikula noari do not use PCIe ARI. 3348cef74409SGil Kupfer noats [PCIE, Intel-IOMMU, AMD-IOMMU] 3349cef74409SGil Kupfer do not use PCIe ATS (and IOMMU device IOTLB). 3350e52347bdSJani Nikula pcie_scan_all Scan all possible PCIe devices. Otherwise we 3351e52347bdSJani Nikula only look for one device below a PCIe downstream 3352e52347bdSJani Nikula port. 3353f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= big_root_window Try to add a big 64bit memory window to the PCIe 3354f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= root complex on AMD CPUs. Some GFX hardware 3355f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= can resize a BAR to allow access to all VRAM. 3356f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= Adding the window is slightly risky (it may 3357f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= conflict with unreported devices), so this 3358f32ab754S=?UTF-8?q?Christian=20K=C3=B6nig?= taints the kernel. 3359aaca43fdSLogan Gunthorpe disable_acs_redir=<pci_dev>[; ...] 3360aaca43fdSLogan Gunthorpe Specify one or more PCI devices (in the format 3361aaca43fdSLogan Gunthorpe specified above) separated by semicolons. 3362aaca43fdSLogan Gunthorpe Each device specified will have the PCI ACS 3363aaca43fdSLogan Gunthorpe redirect capabilities forced off which will 3364aaca43fdSLogan Gunthorpe allow P2P traffic between devices through 3365aaca43fdSLogan Gunthorpe bridges without forcing it upstream. Note: 3366aaca43fdSLogan Gunthorpe this removes isolation between devices and 3367aaca43fdSLogan Gunthorpe may put more devices in an IOMMU group. 3368e52347bdSJani Nikula 3369e52347bdSJani Nikula pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 3370e52347bdSJani Nikula Management. 3371e52347bdSJani Nikula off Disable ASPM. 3372e52347bdSJani Nikula force Enable ASPM even on devices that claim not to support it. 3373e52347bdSJani Nikula WARNING: Forcing ASPM on may cause system lockups. 3374e52347bdSJani Nikula 33754c0fd764SBjorn Helgaas pcie_ports= [PCIE] PCIe port services handling: 33764c0fd764SBjorn Helgaas native Use native PCIe services (PME, AER, DPC, PCIe hotplug) 33774c0fd764SBjorn Helgaas even if the platform doesn't give the OS permission to 33784c0fd764SBjorn Helgaas use them. This may cause conflicts if the platform 33794c0fd764SBjorn Helgaas also tries to use these services. 33804c0fd764SBjorn Helgaas compat Disable native PCIe services (PME, AER, DPC, PCIe 33814c0fd764SBjorn Helgaas hotplug). 3382e52347bdSJani Nikula 3383e52347bdSJani Nikula pcie_port_pm= [PCIE] PCIe port power management handling: 3384e52347bdSJani Nikula off Disable power management of all PCIe ports 3385e52347bdSJani Nikula force Forcibly enable power management of all PCIe ports 3386e52347bdSJani Nikula 3387e52347bdSJani Nikula pcie_pme= [PCIE,PM] Native PCIe PME signaling options: 3388e52347bdSJani Nikula nomsi Do not use MSI for native PCIe PME signaling (this makes 3389e52347bdSJani Nikula all PCIe root ports use INTx for all services). 3390e52347bdSJani Nikula 3391e52347bdSJani Nikula pcmv= [HW,PCMCIA] BadgePAD 4 3392e52347bdSJani Nikula 3393e52347bdSJani Nikula pd_ignore_unused 3394e52347bdSJani Nikula [PM] 3395e52347bdSJani Nikula Keep all power-domains already enabled by bootloader on, 3396e52347bdSJani Nikula even if no driver has claimed them. This is useful 3397e52347bdSJani Nikula for debug and development, but should not be 3398e52347bdSJani Nikula needed on a platform with proper driver support. 3399e52347bdSJani Nikula 3400e52347bdSJani Nikula pd. [PARIDE] 3401e52347bdSJani Nikula See Documentation/blockdev/paride.txt. 3402e52347bdSJani Nikula 3403e52347bdSJani Nikula pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 3404e52347bdSJani Nikula boot time. 3405e52347bdSJani Nikula Format: { 0 | 1 } 3406e52347bdSJani Nikula See arch/parisc/kernel/pdc_chassis.c 3407e52347bdSJani Nikula 3408e52347bdSJani Nikula percpu_alloc= Select which percpu first chunk allocator to use. 3409e52347bdSJani Nikula Currently supported values are "embed" and "page". 3410e52347bdSJani Nikula Archs may support subset or none of the selections. 3411e52347bdSJani Nikula See comments in mm/percpu.c for details on each 3412e52347bdSJani Nikula allocator. This parameter is primarily for debugging 3413e52347bdSJani Nikula and performance comparison. 3414e52347bdSJani Nikula 3415e52347bdSJani Nikula pf. [PARIDE] 3416e52347bdSJani Nikula See Documentation/blockdev/paride.txt. 3417e52347bdSJani Nikula 3418e52347bdSJani Nikula pg. [PARIDE] 3419e52347bdSJani Nikula See Documentation/blockdev/paride.txt. 3420e52347bdSJani Nikula 3421e52347bdSJani Nikula pirq= [SMP,APIC] Manual mp-table setup 3422e52347bdSJani Nikula See Documentation/x86/i386/IO-APIC.txt. 3423e52347bdSJani Nikula 3424e52347bdSJani Nikula plip= [PPT,NET] Parallel port network link 3425e52347bdSJani Nikula Format: { parport<nr> | timid | 0 } 34263ba9b1b8STom Saeger See also Documentation/admin-guide/parport.rst. 3427e52347bdSJani Nikula 3428e52347bdSJani Nikula pmtmr= [X86] Manual setup of pmtmr I/O Port. 3429e52347bdSJani Nikula Override pmtimer IOPort with a hex value. 3430e52347bdSJani Nikula e.g. pmtmr=0x508 3431e52347bdSJani Nikula 3432e52347bdSJani Nikula pnp.debug=1 [PNP] 3433e52347bdSJani Nikula Enable PNP debug messages (depends on the 3434e52347bdSJani Nikula CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time 3435e52347bdSJani Nikula via /sys/module/pnp/parameters/debug. We always show 3436e52347bdSJani Nikula current resource usage; turning this on also shows 3437e52347bdSJani Nikula possible settings and some assignment information. 3438e52347bdSJani Nikula 3439e52347bdSJani Nikula pnpacpi= [ACPI] 3440e52347bdSJani Nikula { off } 3441e52347bdSJani Nikula 3442e52347bdSJani Nikula pnpbios= [ISAPNP] 3443e52347bdSJani Nikula { on | off | curr | res | no-curr | no-res } 3444e52347bdSJani Nikula 3445e52347bdSJani Nikula pnp_reserve_irq= 3446e52347bdSJani Nikula [ISAPNP] Exclude IRQs for the autoconfiguration 3447e52347bdSJani Nikula 3448e52347bdSJani Nikula pnp_reserve_dma= 3449e52347bdSJani Nikula [ISAPNP] Exclude DMAs for the autoconfiguration 3450e52347bdSJani Nikula 3451e52347bdSJani Nikula pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 3452e52347bdSJani Nikula Ranges are in pairs (I/O port base and size). 3453e52347bdSJani Nikula 3454e52347bdSJani Nikula pnp_reserve_mem= 3455e52347bdSJani Nikula [ISAPNP] Exclude memory regions for the 3456e52347bdSJani Nikula autoconfiguration. 3457e52347bdSJani Nikula Ranges are in pairs (memory base and size). 3458e52347bdSJani Nikula 3459e52347bdSJani Nikula ports= [IP_VS_FTP] IPVS ftp helper module 3460e52347bdSJani Nikula Default is 21. 3461e52347bdSJani Nikula Up to 8 (IP_VS_APP_MAX_PORTS) ports 3462e52347bdSJani Nikula may be specified. 3463e52347bdSJani Nikula Format: <port>,<port>.... 3464e52347bdSJani Nikula 3465c3cbd075SBalbir Singh powersave=off [PPC] This option disables power saving features. 3466c3cbd075SBalbir Singh It specifically disables cpuidle and sets the 3467c3cbd075SBalbir Singh platform machine description specific power_save 3468c3cbd075SBalbir Singh function to NULL. On Idle the CPU just reduces 3469c3cbd075SBalbir Singh execution priority. 3470c3cbd075SBalbir Singh 3471e52347bdSJani Nikula ppc_strict_facility_enable 3472e52347bdSJani Nikula [PPC] This option catches any kernel floating point, 3473e52347bdSJani Nikula Altivec, VSX and SPE outside of regions specifically 3474e52347bdSJani Nikula allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). 3475e52347bdSJani Nikula There is some performance impact when enabling this. 3476e52347bdSJani Nikula 347707fd1761SCyril Bur ppc_tm= [PPC] 347807fd1761SCyril Bur Format: {"off"} 347907fd1761SCyril Bur Disable Hardware Transactional Memory 348007fd1761SCyril Bur 3481e52347bdSJani Nikula print-fatal-signals= 3482e52347bdSJani Nikula [KNL] debug: print fatal signals 3483e52347bdSJani Nikula 3484e52347bdSJani Nikula If enabled, warn about various signal handling 3485e52347bdSJani Nikula related application anomalies: too many signals, 3486e52347bdSJani Nikula too many POSIX.1 timers, fatal signals causing a 3487e52347bdSJani Nikula coredump - etc. 3488e52347bdSJani Nikula 3489e52347bdSJani Nikula If you hit the warning due to signal overflow, 3490e52347bdSJani Nikula you might want to try "ulimit -i unlimited". 3491e52347bdSJani Nikula 3492e52347bdSJani Nikula default: off. 3493e52347bdSJani Nikula 3494e52347bdSJani Nikula printk.always_kmsg_dump= 3495e52347bdSJani Nikula Trigger kmsg_dump for cases other than kernel oops or 3496e52347bdSJani Nikula panics 3497e52347bdSJani Nikula Format: <bool> (1/Y/y=enable, 0/N/n=disable) 3498e52347bdSJani Nikula default: disabled 3499e52347bdSJani Nikula 3500e52347bdSJani Nikula printk.devkmsg={on,off,ratelimit} 3501e52347bdSJani Nikula Control writing to /dev/kmsg. 3502e52347bdSJani Nikula on - unlimited logging to /dev/kmsg from userspace 3503e52347bdSJani Nikula off - logging to /dev/kmsg disabled 3504e52347bdSJani Nikula ratelimit - ratelimit the logging 3505e52347bdSJani Nikula Default: ratelimit 3506e52347bdSJani Nikula 3507e52347bdSJani Nikula printk.time= Show timing data prefixed to each printk message line 3508e52347bdSJani Nikula Format: <bool> (1/Y/y=enable, 0/N/n=disable) 3509e52347bdSJani Nikula 3510e52347bdSJani Nikula processor.max_cstate= [HW,ACPI] 3511e52347bdSJani Nikula Limit processor to maximum C-state 3512e52347bdSJani Nikula max_cstate=9 overrides any DMI blacklist limit. 3513e52347bdSJani Nikula 3514e52347bdSJani Nikula processor.nocst [HW,ACPI] 3515e52347bdSJani Nikula Ignore the _CST method to determine C-states, 3516e52347bdSJani Nikula instead using the legacy FADT method 3517e52347bdSJani Nikula 3518e52347bdSJani Nikula profile= [KNL] Enable kernel profiling via /proc/profile 3519e7e61fc0SRandy Dunlap Format: [<profiletype>,]<number> 3520e7e61fc0SRandy Dunlap Param: <profiletype>: "schedule", "sleep", or "kvm" 3521e7e61fc0SRandy Dunlap [defaults to kernel profiling] 3522e52347bdSJani Nikula Param: "schedule" - profile schedule points. 3523e52347bdSJani Nikula Param: "sleep" - profile D-state sleeping (millisecs). 3524e52347bdSJani Nikula Requires CONFIG_SCHEDSTATS 3525e52347bdSJani Nikula Param: "kvm" - profile VM exits. 3526e7e61fc0SRandy Dunlap Param: <number> - step/bucket size as a power of 2 for 3527e7e61fc0SRandy Dunlap statistical time based profiling. 3528e52347bdSJani Nikula 3529e52347bdSJani Nikula prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 3530e52347bdSJani Nikula before loading. 3531e52347bdSJani Nikula See Documentation/blockdev/ramdisk.txt. 3532e52347bdSJani Nikula 3533e0c27447SJohannes Weiner psi= [KNL] Enable or disable pressure stall information 3534e0c27447SJohannes Weiner tracking. 3535e0c27447SJohannes Weiner Format: <bool> 3536e0c27447SJohannes Weiner 3537e52347bdSJani Nikula psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 3538e52347bdSJani Nikula probe for; one of (bare|imps|exps|lifebook|any). 3539e52347bdSJani Nikula psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 3540e52347bdSJani Nikula per second. 3541e52347bdSJani Nikula psmouse.resetafter= [HW,MOUSE] 3542e52347bdSJani Nikula Try to reset the device after so many bad packets 3543e52347bdSJani Nikula (0 = never). 3544e52347bdSJani Nikula psmouse.resolution= 3545e52347bdSJani Nikula [HW,MOUSE] Set desired mouse resolution, in dpi. 3546e52347bdSJani Nikula psmouse.smartscroll= 3547e52347bdSJani Nikula [HW,MOUSE] Controls Logitech smartscroll autorepeat. 3548e52347bdSJani Nikula 0 = disabled, 1 = enabled (default). 3549e52347bdSJani Nikula 3550e52347bdSJani Nikula pstore.backend= Specify the name of the pstore backend to use 3551e52347bdSJani Nikula 3552e52347bdSJani Nikula pt. [PARIDE] 3553e52347bdSJani Nikula See Documentation/blockdev/paride.txt. 3554e52347bdSJani Nikula 355501c9b17bSDave Hansen pti= [X86_64] Control Page Table Isolation of user and 355601c9b17bSDave Hansen kernel address spaces. Disabling this feature 355701c9b17bSDave Hansen removes hardening, but improves performance of 355801c9b17bSDave Hansen system calls and interrupts. 355901c9b17bSDave Hansen 356001c9b17bSDave Hansen on - unconditionally enable 356101c9b17bSDave Hansen off - unconditionally disable 356201c9b17bSDave Hansen auto - kernel detects whether your CPU model is 356301c9b17bSDave Hansen vulnerable to issues that PTI mitigates 356401c9b17bSDave Hansen 356501c9b17bSDave Hansen Not specifying this option is equivalent to pti=auto. 356601c9b17bSDave Hansen 356701c9b17bSDave Hansen nopti [X86_64] 356801c9b17bSDave Hansen Equivalent to pti=off 356941f4c20bSBorislav Petkov 3570e52347bdSJani Nikula pty.legacy_count= 3571e52347bdSJani Nikula [KNL] Number of legacy pty's. Overwrites compiled-in 3572e52347bdSJani Nikula default number. 3573e52347bdSJani Nikula 3574e52347bdSJani Nikula quiet [KNL] Disable most log messages 3575e52347bdSJani Nikula 3576e52347bdSJani Nikula r128= [HW,DRM] 3577e52347bdSJani Nikula 3578e52347bdSJani Nikula raid= [HW,RAID] 3579e52347bdSJani Nikula See Documentation/admin-guide/md.rst. 3580e52347bdSJani Nikula 3581e52347bdSJani Nikula ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 3582e52347bdSJani Nikula See Documentation/blockdev/ramdisk.txt. 3583e52347bdSJani Nikula 35849b254366SKees Cook random.trust_cpu={on,off} 35859b254366SKees Cook [KNL] Enable or disable trusting the use of the 35869b254366SKees Cook CPU's random number generator (if available) to 35879b254366SKees Cook fully seed the kernel's CRNG. Default is controlled 35889b254366SKees Cook by CONFIG_RANDOM_TRUST_CPU. 35899b254366SKees Cook 3590011d8261SBorislav Petkov ras=option[,option,...] [KNL] RAS-specific options 3591011d8261SBorislav Petkov 3592011d8261SBorislav Petkov cec_disable [X86] 3593011d8261SBorislav Petkov Disable the Correctable Errors Collector, 3594011d8261SBorislav Petkov see CONFIG_RAS_CEC help text. 3595011d8261SBorislav Petkov 3596e52347bdSJani Nikula rcu_nocbs= [KNL] 3597e52347bdSJani Nikula The argument is a cpu list, as described above. 3598e52347bdSJani Nikula 3599e52347bdSJani Nikula In kernels built with CONFIG_RCU_NOCB_CPU=y, set 3600e52347bdSJani Nikula the specified list of CPUs to be no-callback CPUs. 360177095901SPaul E. McKenney Invocation of these CPUs' RCU callbacks will be 360277095901SPaul E. McKenney offloaded to "rcuox/N" kthreads created for that 360377095901SPaul E. McKenney purpose, where "x" is "p" for RCU-preempt, and 360477095901SPaul E. McKenney "s" for RCU-sched, and "N" is the CPU number. 360577095901SPaul E. McKenney This reduces OS jitter on the offloaded CPUs, 360677095901SPaul E. McKenney which can be useful for HPC and real-time 360777095901SPaul E. McKenney workloads. It can also improve energy efficiency 360877095901SPaul E. McKenney for asymmetric multiprocessors. 3609e52347bdSJani Nikula 3610e52347bdSJani Nikula rcu_nocb_poll [KNL] 3611e52347bdSJani Nikula Rather than requiring that offloaded CPUs 3612e52347bdSJani Nikula (specified by rcu_nocbs= above) explicitly 3613e52347bdSJani Nikula awaken the corresponding "rcuoN" kthreads, 3614e52347bdSJani Nikula make these kthreads poll for callbacks. 3615e52347bdSJani Nikula This improves the real-time response for the 3616e52347bdSJani Nikula offloaded CPUs by relieving them of the need to 3617e52347bdSJani Nikula wake up the corresponding kthread, but degrades 3618e52347bdSJani Nikula energy efficiency by requiring that the kthreads 3619e52347bdSJani Nikula periodically wake up to do the polling. 3620e52347bdSJani Nikula 3621e52347bdSJani Nikula rcutree.blimit= [KNL] 3622e52347bdSJani Nikula Set maximum number of finished RCU callbacks to 3623e52347bdSJani Nikula process in one batch. 3624e52347bdSJani Nikula 3625e52347bdSJani Nikula rcutree.dump_tree= [KNL] 3626e52347bdSJani Nikula Dump the structure of the rcu_node combining tree 3627e52347bdSJani Nikula out at early boot. This is used for diagnostic 3628e52347bdSJani Nikula purposes, to verify correct tree setup. 3629e52347bdSJani Nikula 3630e52347bdSJani Nikula rcutree.gp_cleanup_delay= [KNL] 3631e52347bdSJani Nikula Set the number of jiffies to delay each step of 363290040c9eSPaul E. McKenney RCU grace-period cleanup. 3633e52347bdSJani Nikula 3634e52347bdSJani Nikula rcutree.gp_init_delay= [KNL] 3635e52347bdSJani Nikula Set the number of jiffies to delay each step of 363690040c9eSPaul E. McKenney RCU grace-period initialization. 3637e52347bdSJani Nikula 3638e52347bdSJani Nikula rcutree.gp_preinit_delay= [KNL] 3639e52347bdSJani Nikula Set the number of jiffies to delay each step of 3640e52347bdSJani Nikula RCU grace-period pre-initialization, that is, 3641e52347bdSJani Nikula the propagation of recent CPU-hotplug changes up 364290040c9eSPaul E. McKenney the rcu_node combining tree. 3643e52347bdSJani Nikula 3644e52347bdSJani Nikula rcutree.rcu_fanout_exact= [KNL] 3645e52347bdSJani Nikula Disable autobalancing of the rcu_node combining 3646e52347bdSJani Nikula tree. This is used by rcutorture, and might 3647e52347bdSJani Nikula possibly be useful for architectures having high 3648e52347bdSJani Nikula cache-to-cache transfer latencies. 3649e52347bdSJani Nikula 3650e52347bdSJani Nikula rcutree.rcu_fanout_leaf= [KNL] 3651e52347bdSJani Nikula Change the number of CPUs assigned to each 3652e52347bdSJani Nikula leaf rcu_node structure. Useful for very 3653e52347bdSJani Nikula large systems, which will choose the value 64, 3654e52347bdSJani Nikula and for NUMA systems with large remote-access 3655e52347bdSJani Nikula latencies, which will choose a value aligned 3656e52347bdSJani Nikula with the appropriate hardware boundaries. 3657e52347bdSJani Nikula 3658e52347bdSJani Nikula rcutree.jiffies_till_sched_qs= [KNL] 3659e52347bdSJani Nikula Set required age in jiffies for a 3660e52347bdSJani Nikula given grace period before RCU starts 3661e52347bdSJani Nikula soliciting quiescent-state help from 3662c06aed0eSPaul E. McKenney rcu_note_context_switch(). If not specified, the 3663c06aed0eSPaul E. McKenney kernel will calculate a value based on the most 3664c06aed0eSPaul E. McKenney recent settings of rcutree.jiffies_till_first_fqs 3665c06aed0eSPaul E. McKenney and rcutree.jiffies_till_next_fqs. 3666c06aed0eSPaul E. McKenney This calculated value may be viewed in 3667c06aed0eSPaul E. McKenney rcutree.jiffies_to_sched_qs. Any attempt to 3668c06aed0eSPaul E. McKenney set rcutree.jiffies_to_sched_qs will be 3669c06aed0eSPaul E. McKenney cheerfully overwritten. 3670e52347bdSJani Nikula 3671e52347bdSJani Nikula rcutree.jiffies_till_first_fqs= [KNL] 3672e52347bdSJani Nikula Set delay from grace-period initialization to 3673e52347bdSJani Nikula first attempt to force quiescent states. 3674e52347bdSJani Nikula Units are jiffies, minimum value is zero, 3675e52347bdSJani Nikula and maximum value is HZ. 3676e52347bdSJani Nikula 3677e52347bdSJani Nikula rcutree.jiffies_till_next_fqs= [KNL] 3678e52347bdSJani Nikula Set delay between subsequent attempts to force 3679e52347bdSJani Nikula quiescent states. Units are jiffies, minimum 3680e52347bdSJani Nikula value is one, and maximum value is HZ. 3681e52347bdSJani Nikula 3682e52347bdSJani Nikula rcutree.kthread_prio= [KNL,BOOT] 3683e52347bdSJani Nikula Set the SCHED_FIFO priority of the RCU per-CPU 3684e52347bdSJani Nikula kthreads (rcuc/N). This value is also used for 3685e52347bdSJani Nikula the priority of the RCU boost threads (rcub/N) 3686e52347bdSJani Nikula and for the RCU grace-period kthreads (rcu_bh, 3687e52347bdSJani Nikula rcu_preempt, and rcu_sched). If RCU_BOOST is 3688e52347bdSJani Nikula set, valid values are 1-99 and the default is 1 3689e52347bdSJani Nikula (the least-favored priority). Otherwise, when 3690e52347bdSJani Nikula RCU_BOOST is not set, valid values are 0-99 and 3691e52347bdSJani Nikula the default is zero (non-realtime operation). 3692e52347bdSJani Nikula 3693e52347bdSJani Nikula rcutree.rcu_nocb_leader_stride= [KNL] 3694e52347bdSJani Nikula Set the number of NOCB kthread groups, which 3695e52347bdSJani Nikula defaults to the square root of the number of 3696e52347bdSJani Nikula CPUs. Larger numbers reduces the wakeup overhead 3697e52347bdSJani Nikula on the per-CPU grace-period kthreads, but increases 3698e52347bdSJani Nikula that same overhead on each group's leader. 3699e52347bdSJani Nikula 3700e52347bdSJani Nikula rcutree.qhimark= [KNL] 3701e52347bdSJani Nikula Set threshold of queued RCU callbacks beyond which 3702e52347bdSJani Nikula batch limiting is disabled. 3703e52347bdSJani Nikula 3704e52347bdSJani Nikula rcutree.qlowmark= [KNL] 3705e52347bdSJani Nikula Set threshold of queued RCU callbacks below which 3706e52347bdSJani Nikula batch limiting is re-enabled. 3707e52347bdSJani Nikula 3708e52347bdSJani Nikula rcutree.rcu_idle_gp_delay= [KNL] 3709e52347bdSJani Nikula Set wakeup interval for idle CPUs that have 3710e52347bdSJani Nikula RCU callbacks (RCU_FAST_NO_HZ=y). 3711e52347bdSJani Nikula 3712e52347bdSJani Nikula rcutree.rcu_idle_lazy_gp_delay= [KNL] 3713e52347bdSJani Nikula Set wakeup interval for idle CPUs that have 3714e52347bdSJani Nikula only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y). 3715e52347bdSJani Nikula Lazy RCU callbacks are those which RCU can 3716e52347bdSJani Nikula prove do nothing more than free memory. 3717e52347bdSJani Nikula 3718e3c50dfbSPaul E. McKenney rcutree.rcu_kick_kthreads= [KNL] 3719e3c50dfbSPaul E. McKenney Cause the grace-period kthread to get an extra 3720e3c50dfbSPaul E. McKenney wake_up() if it sleeps three times longer than 3721e3c50dfbSPaul E. McKenney it should at force-quiescent-state time. 3722e3c50dfbSPaul E. McKenney This wake_up() will be accompanied by a 3723e3c50dfbSPaul E. McKenney WARN_ONCE() splat and an ftrace_dump(). 3724e3c50dfbSPaul E. McKenney 3725881ed593SPaul E. McKenney rcuperf.gp_async= [KNL] 3726881ed593SPaul E. McKenney Measure performance of asynchronous 3727881ed593SPaul E. McKenney grace-period primitives such as call_rcu(). 3728881ed593SPaul E. McKenney 3729881ed593SPaul E. McKenney rcuperf.gp_async_max= [KNL] 3730881ed593SPaul E. McKenney Specify the maximum number of outstanding 3731881ed593SPaul E. McKenney callbacks per writer thread. When a writer 3732881ed593SPaul E. McKenney thread exceeds this limit, it invokes the 3733881ed593SPaul E. McKenney corresponding flavor of rcu_barrier() to allow 3734881ed593SPaul E. McKenney previously posted callbacks to drain. 3735881ed593SPaul E. McKenney 3736e52347bdSJani Nikula rcuperf.gp_exp= [KNL] 3737e52347bdSJani Nikula Measure performance of expedited synchronous 3738e52347bdSJani Nikula grace-period primitives. 3739e52347bdSJani Nikula 3740e52347bdSJani Nikula rcuperf.holdoff= [KNL] 3741e52347bdSJani Nikula Set test-start holdoff period. The purpose of 3742e52347bdSJani Nikula this parameter is to delay the start of the 3743e52347bdSJani Nikula test until boot completes in order to avoid 3744e52347bdSJani Nikula interference. 3745e52347bdSJani Nikula 3746e52347bdSJani Nikula rcuperf.nreaders= [KNL] 3747e52347bdSJani Nikula Set number of RCU readers. The value -1 selects 3748e52347bdSJani Nikula N, where N is the number of CPUs. A value 3749e52347bdSJani Nikula "n" less than -1 selects N-n+1, where N is again 3750e52347bdSJani Nikula the number of CPUs. For example, -2 selects N 3751e52347bdSJani Nikula (the number of CPUs), -3 selects N+1, and so on. 3752e52347bdSJani Nikula A value of "n" less than or equal to -N selects 3753e52347bdSJani Nikula a single reader. 3754e52347bdSJani Nikula 3755e52347bdSJani Nikula rcuperf.nwriters= [KNL] 3756e52347bdSJani Nikula Set number of RCU writers. The values operate 3757e52347bdSJani Nikula the same as for rcuperf.nreaders. 3758e52347bdSJani Nikula N, where N is the number of CPUs 3759e52347bdSJani Nikula 3760820687a7SPaul E. McKenney rcuperf.perf_type= [KNL] 3761820687a7SPaul E. McKenney Specify the RCU implementation to test. 3762820687a7SPaul E. McKenney 3763e52347bdSJani Nikula rcuperf.shutdown= [KNL] 3764e52347bdSJani Nikula Shut the system down after performance tests 3765e52347bdSJani Nikula complete. This is useful for hands-off automated 3766e52347bdSJani Nikula testing. 3767e52347bdSJani Nikula 3768e52347bdSJani Nikula rcuperf.verbose= [KNL] 3769e52347bdSJani Nikula Enable additional printk() statements. 3770e52347bdSJani Nikula 3771820687a7SPaul E. McKenney rcuperf.writer_holdoff= [KNL] 3772820687a7SPaul E. McKenney Write-side holdoff between grace periods, 3773820687a7SPaul E. McKenney in microseconds. The default of zero says 3774820687a7SPaul E. McKenney no holdoff. 3775820687a7SPaul E. McKenney 3776e52347bdSJani Nikula rcutorture.fqs_duration= [KNL] 3777e52347bdSJani Nikula Set duration of force_quiescent_state bursts 3778e52347bdSJani Nikula in microseconds. 3779e52347bdSJani Nikula 3780e52347bdSJani Nikula rcutorture.fqs_holdoff= [KNL] 3781e52347bdSJani Nikula Set holdoff time within force_quiescent_state bursts 3782e52347bdSJani Nikula in microseconds. 3783e52347bdSJani Nikula 3784e52347bdSJani Nikula rcutorture.fqs_stutter= [KNL] 3785e52347bdSJani Nikula Set wait time between force_quiescent_state bursts 3786e52347bdSJani Nikula in seconds. 3787e52347bdSJani Nikula 3788ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress= [KNL] 3789ed8f6fb2SPaul E. McKenney Enable RCU grace-period forward-progress testing 3790ed8f6fb2SPaul E. McKenney for the types of RCU supporting this notion. 3791ed8f6fb2SPaul E. McKenney 3792ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_div= [KNL] 3793ed8f6fb2SPaul E. McKenney Specify the fraction of a CPU-stall-warning 3794ed8f6fb2SPaul E. McKenney period to do tight-loop forward-progress testing. 3795ed8f6fb2SPaul E. McKenney 3796ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_holdoff= [KNL] 3797ed8f6fb2SPaul E. McKenney Number of seconds to wait between successive 3798ed8f6fb2SPaul E. McKenney forward-progress tests. 3799ed8f6fb2SPaul E. McKenney 3800ed8f6fb2SPaul E. McKenney rcutorture.fwd_progress_need_resched= [KNL] 3801ed8f6fb2SPaul E. McKenney Enclose cond_resched() calls within checks for 3802ed8f6fb2SPaul E. McKenney need_resched() during tight-loop forward-progress 3803ed8f6fb2SPaul E. McKenney testing. 3804ed8f6fb2SPaul E. McKenney 3805e52347bdSJani Nikula rcutorture.gp_cond= [KNL] 3806e52347bdSJani Nikula Use conditional/asynchronous update-side 3807e52347bdSJani Nikula primitives, if available. 3808e52347bdSJani Nikula 3809e52347bdSJani Nikula rcutorture.gp_exp= [KNL] 3810e52347bdSJani Nikula Use expedited update-side primitives, if available. 3811e52347bdSJani Nikula 3812e52347bdSJani Nikula rcutorture.gp_normal= [KNL] 3813e52347bdSJani Nikula Use normal (non-expedited) asynchronous 3814e52347bdSJani Nikula update-side primitives, if available. 3815e52347bdSJani Nikula 3816e52347bdSJani Nikula rcutorture.gp_sync= [KNL] 3817e52347bdSJani Nikula Use normal (non-expedited) synchronous 3818e52347bdSJani Nikula update-side primitives, if available. If all 3819e52347bdSJani Nikula of rcutorture.gp_cond=, rcutorture.gp_exp=, 3820e52347bdSJani Nikula rcutorture.gp_normal=, and rcutorture.gp_sync= 3821e52347bdSJani Nikula are zero, rcutorture acts as if is interpreted 3822e52347bdSJani Nikula they are all non-zero. 3823e52347bdSJani Nikula 3824e52347bdSJani Nikula rcutorture.n_barrier_cbs= [KNL] 3825e52347bdSJani Nikula Set callbacks/threads for rcu_barrier() testing. 3826e52347bdSJani Nikula 3827e52347bdSJani Nikula rcutorture.nfakewriters= [KNL] 3828e52347bdSJani Nikula Set number of concurrent RCU writers. These just 3829e52347bdSJani Nikula stress RCU, they don't participate in the actual 3830e52347bdSJani Nikula test, hence the "fake". 3831e52347bdSJani Nikula 3832e52347bdSJani Nikula rcutorture.nreaders= [KNL] 3833e52347bdSJani Nikula Set number of RCU readers. The value -1 selects 3834e52347bdSJani Nikula N-1, where N is the number of CPUs. A value 3835e52347bdSJani Nikula "n" less than -1 selects N-n-2, where N is again 3836e52347bdSJani Nikula the number of CPUs. For example, -2 selects N 3837e52347bdSJani Nikula (the number of CPUs), -3 selects N+1, and so on. 3838e52347bdSJani Nikula 3839e52347bdSJani Nikula rcutorture.object_debug= [KNL] 3840e52347bdSJani Nikula Enable debug-object double-call_rcu() testing. 3841e52347bdSJani Nikula 3842e52347bdSJani Nikula rcutorture.onoff_holdoff= [KNL] 3843e52347bdSJani Nikula Set time (s) after boot for CPU-hotplug testing. 3844e52347bdSJani Nikula 3845e52347bdSJani Nikula rcutorture.onoff_interval= [KNL] 3846028be12bSPaul E. McKenney Set time (jiffies) between CPU-hotplug operations, 3847028be12bSPaul E. McKenney or zero to disable CPU-hotplug testing. 3848e52347bdSJani Nikula 3849e52347bdSJani Nikula rcutorture.shuffle_interval= [KNL] 3850e52347bdSJani Nikula Set task-shuffle interval (s). Shuffling tasks 3851e52347bdSJani Nikula allows some CPUs to go into dyntick-idle mode 3852e52347bdSJani Nikula during the rcutorture test. 3853e52347bdSJani Nikula 3854e52347bdSJani Nikula rcutorture.shutdown_secs= [KNL] 3855e52347bdSJani Nikula Set time (s) after boot system shutdown. This 3856e52347bdSJani Nikula is useful for hands-off automated testing. 3857e52347bdSJani Nikula 3858e52347bdSJani Nikula rcutorture.stall_cpu= [KNL] 3859e52347bdSJani Nikula Duration of CPU stall (s) to test RCU CPU stall 3860e52347bdSJani Nikula warnings, zero to disable. 3861e52347bdSJani Nikula 3862e52347bdSJani Nikula rcutorture.stall_cpu_holdoff= [KNL] 3863e52347bdSJani Nikula Time to wait (s) after boot before inducing stall. 3864e52347bdSJani Nikula 38652b1516e5SPaul E. McKenney rcutorture.stall_cpu_irqsoff= [KNL] 38662b1516e5SPaul E. McKenney Disable interrupts while stalling if set. 38672b1516e5SPaul E. McKenney 3868e52347bdSJani Nikula rcutorture.stat_interval= [KNL] 3869e52347bdSJani Nikula Time (s) between statistics printk()s. 3870e52347bdSJani Nikula 3871e52347bdSJani Nikula rcutorture.stutter= [KNL] 3872e52347bdSJani Nikula Time (s) to stutter testing, for example, specifying 3873e52347bdSJani Nikula five seconds causes the test to run for five seconds, 3874e52347bdSJani Nikula wait for five seconds, and so on. This tests RCU's 3875e52347bdSJani Nikula ability to transition abruptly to and from idle. 3876e52347bdSJani Nikula 3877e52347bdSJani Nikula rcutorture.test_boost= [KNL] 3878e52347bdSJani Nikula Test RCU priority boosting? 0=no, 1=maybe, 2=yes. 3879e52347bdSJani Nikula "Maybe" means test if the RCU implementation 3880e52347bdSJani Nikula under test support RCU priority boosting. 3881e52347bdSJani Nikula 3882e52347bdSJani Nikula rcutorture.test_boost_duration= [KNL] 3883e52347bdSJani Nikula Duration (s) of each individual boost test. 3884e52347bdSJani Nikula 3885e52347bdSJani Nikula rcutorture.test_boost_interval= [KNL] 3886e52347bdSJani Nikula Interval (s) between each boost test. 3887e52347bdSJani Nikula 3888e52347bdSJani Nikula rcutorture.test_no_idle_hz= [KNL] 3889e52347bdSJani Nikula Test RCU's dyntick-idle handling. See also the 3890e52347bdSJani Nikula rcutorture.shuffle_interval parameter. 3891e52347bdSJani Nikula 3892e52347bdSJani Nikula rcutorture.torture_type= [KNL] 3893e52347bdSJani Nikula Specify the RCU implementation to test. 3894e52347bdSJani Nikula 3895e52347bdSJani Nikula rcutorture.verbose= [KNL] 3896e52347bdSJani Nikula Enable additional printk() statements. 3897e52347bdSJani Nikula 3898e52347bdSJani Nikula rcupdate.rcu_cpu_stall_suppress= [KNL] 3899e52347bdSJani Nikula Suppress RCU CPU stall warning messages. 3900e52347bdSJani Nikula 3901e52347bdSJani Nikula rcupdate.rcu_cpu_stall_timeout= [KNL] 3902e52347bdSJani Nikula Set timeout for RCU CPU stall warning messages. 3903e52347bdSJani Nikula 3904e52347bdSJani Nikula rcupdate.rcu_expedited= [KNL] 3905e52347bdSJani Nikula Use expedited grace-period primitives, for 3906e52347bdSJani Nikula example, synchronize_rcu_expedited() instead 3907e52347bdSJani Nikula of synchronize_rcu(). This reduces latency, 3908e52347bdSJani Nikula but can increase CPU utilization, degrade 3909e52347bdSJani Nikula real-time latency, and degrade energy efficiency. 3910e52347bdSJani Nikula No effect on CONFIG_TINY_RCU kernels. 3911e52347bdSJani Nikula 3912e52347bdSJani Nikula rcupdate.rcu_normal= [KNL] 3913e52347bdSJani Nikula Use only normal grace-period primitives, 3914e52347bdSJani Nikula for example, synchronize_rcu() instead of 3915e52347bdSJani Nikula synchronize_rcu_expedited(). This improves 3916e52347bdSJani Nikula real-time latency, CPU utilization, and 3917e52347bdSJani Nikula energy efficiency, but can expose users to 3918e52347bdSJani Nikula increased grace-period latency. This parameter 3919e52347bdSJani Nikula overrides rcupdate.rcu_expedited. No effect on 3920e52347bdSJani Nikula CONFIG_TINY_RCU kernels. 3921e52347bdSJani Nikula 3922e52347bdSJani Nikula rcupdate.rcu_normal_after_boot= [KNL] 3923e52347bdSJani Nikula Once boot has completed (that is, after 3924e52347bdSJani Nikula rcu_end_inkernel_boot() has been invoked), use 3925e52347bdSJani Nikula only normal grace-period primitives. No effect 3926e52347bdSJani Nikula on CONFIG_TINY_RCU kernels. 3927e52347bdSJani Nikula 3928e52347bdSJani Nikula rcupdate.rcu_task_stall_timeout= [KNL] 3929e52347bdSJani Nikula Set timeout in jiffies for RCU task stall warning 3930e52347bdSJani Nikula messages. Disable with a value less than or equal 3931e52347bdSJani Nikula to zero. 3932e52347bdSJani Nikula 3933e52347bdSJani Nikula rcupdate.rcu_self_test= [KNL] 3934e52347bdSJani Nikula Run the RCU early boot self tests 3935e52347bdSJani Nikula 3936e52347bdSJani Nikula rdinit= [KNL] 3937e52347bdSJani Nikula Format: <full_path> 3938e52347bdSJani Nikula Run specified binary instead of /init from the ramdisk, 3939e52347bdSJani Nikula used for early userspace startup. See initrd. 3940e52347bdSJani Nikula 39411d9807fcSTony Luck rdt= [HW,X86,RDT] 39421d9807fcSTony Luck Turn on/off individual RDT features. List is: 394331516de3SFenghua Yu cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp, 394431516de3SFenghua Yu mba. 39451d9807fcSTony Luck E.g. to turn on cmt and turn off mba use: 39461d9807fcSTony Luck rdt=cmt,!mba 39471d9807fcSTony Luck 3948e52347bdSJani Nikula reboot= [KNL] 3949e52347bdSJani Nikula Format (x86 or x86_64): 3950e52347bdSJani Nikula [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \ 3951e52347bdSJani Nikula [[,]s[mp]#### \ 3952e52347bdSJani Nikula [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ 3953e52347bdSJani Nikula [[,]f[orce] 3954e52347bdSJani Nikula Where reboot_mode is one of warm (soft) or cold (hard) or gpio, 3955e52347bdSJani Nikula reboot_type is one of bios, acpi, kbd, triple, efi, or pci, 3956e52347bdSJani Nikula reboot_force is either force or not specified, 3957e52347bdSJani Nikula reboot_cpu is s[mp]#### with #### being the processor 3958e52347bdSJani Nikula to be used for rebooting. 3959e52347bdSJani Nikula 3960e52347bdSJani Nikula relax_domain_level= 3961e52347bdSJani Nikula [KNL, SMP] Set scheduler's default relax_domain_level. 3962e52347bdSJani Nikula See Documentation/cgroup-v1/cpusets.txt. 3963e52347bdSJani Nikula 3964ffd2e8dfSBjorn Helgaas reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory 3965ffd2e8dfSBjorn Helgaas Format: <base1>,<size1>[,<base2>,<size2>,...] 3966ffd2e8dfSBjorn Helgaas Reserve I/O ports or memory so the kernel won't use 3967ffd2e8dfSBjorn Helgaas them. If <base> is less than 0x10000, the region 3968ffd2e8dfSBjorn Helgaas is assumed to be I/O ports; otherwise it is memory. 3969e52347bdSJani Nikula 3970e52347bdSJani Nikula reservetop= [X86-32] 3971e52347bdSJani Nikula Format: nn[KMG] 3972e52347bdSJani Nikula Reserves a hole at the top of the kernel virtual 3973e52347bdSJani Nikula address space. 3974e52347bdSJani Nikula 3975e52347bdSJani Nikula reservelow= [X86] 3976e52347bdSJani Nikula Format: nn[K] 3977e52347bdSJani Nikula Set the amount of memory to reserve for BIOS at 3978e52347bdSJani Nikula the bottom of the address space. 3979e52347bdSJani Nikula 3980e52347bdSJani Nikula reset_devices [KNL] Force drivers to reset the underlying device 3981e52347bdSJani Nikula during initialization. 3982e52347bdSJani Nikula 3983e52347bdSJani Nikula resume= [SWSUSP] 3984e52347bdSJani Nikula Specify the partition device for software suspend 3985e52347bdSJani Nikula Format: 3986e52347bdSJani Nikula {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>} 3987e52347bdSJani Nikula 3988e52347bdSJani Nikula resume_offset= [SWSUSP] 3989e52347bdSJani Nikula Specify the offset from the beginning of the partition 3990e52347bdSJani Nikula given by "resume=" at which the swap header is located, 3991e52347bdSJani Nikula in <PAGE_SIZE> units (needed only for swap files). 3992e52347bdSJani Nikula See Documentation/power/swsusp-and-swap-files.txt 3993e52347bdSJani Nikula 3994e52347bdSJani Nikula resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to 3995e52347bdSJani Nikula read the resume files 3996e52347bdSJani Nikula 3997e52347bdSJani Nikula resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up. 3998e52347bdSJani Nikula Useful for devices that are detected asynchronously 3999e52347bdSJani Nikula (e.g. USB and MMC devices). 4000e52347bdSJani Nikula 4001e52347bdSJani Nikula hibernate= [HIBERNATION] 4002e52347bdSJani Nikula noresume Don't check if there's a hibernation image 4003e52347bdSJani Nikula present during boot. 4004e52347bdSJani Nikula nocompress Don't compress/decompress hibernation images. 4005e52347bdSJani Nikula no Disable hibernation and resume. 4006e52347bdSJani Nikula protect_image Turn on image protection during restoration 4007e52347bdSJani Nikula (that will set all pages holding image data 4008e52347bdSJani Nikula during restoration read-only). 4009e52347bdSJani Nikula 4010e52347bdSJani Nikula retain_initrd [RAM] Keep initrd memory after extraction 4011e52347bdSJani Nikula 4012e52347bdSJani Nikula rfkill.default_state= 4013e52347bdSJani Nikula 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, 4014e52347bdSJani Nikula etc. communication is blocked by default. 4015e52347bdSJani Nikula 1 Unblocked. 4016e52347bdSJani Nikula 4017e52347bdSJani Nikula rfkill.master_switch_mode= 4018e52347bdSJani Nikula 0 The "airplane mode" button does nothing. 4019e52347bdSJani Nikula 1 The "airplane mode" button toggles between everything 4020e52347bdSJani Nikula blocked and the previous configuration. 4021e52347bdSJani Nikula 2 The "airplane mode" button toggles between everything 4022e52347bdSJani Nikula blocked and everything unblocked. 4023e52347bdSJani Nikula 4024e52347bdSJani Nikula rhash_entries= [KNL,NET] 4025e52347bdSJani Nikula Set number of hash buckets for route cache 4026e52347bdSJani Nikula 4027e16fd002SGrzegorz Andrejczuk ring3mwait=disable 4028e16fd002SGrzegorz Andrejczuk [KNL] Disable ring 3 MONITOR/MWAIT feature on supported 4029e16fd002SGrzegorz Andrejczuk CPUs. 4030e16fd002SGrzegorz Andrejczuk 4031e52347bdSJani Nikula ro [KNL] Mount root device read-only on boot 4032e52347bdSJani Nikula 4033e52347bdSJani Nikula rodata= [KNL] 4034e52347bdSJani Nikula on Mark read-only kernel memory as read-only (default). 4035e52347bdSJani Nikula off Leave read-only kernel memory writable for debugging. 4036e52347bdSJani Nikula 4037e52347bdSJani Nikula rockchip.usb_uart 4038e52347bdSJani Nikula Enable the uart passthrough on the designated usb port 4039e52347bdSJani Nikula on Rockchip SoCs. When active, the signals of the 4040e52347bdSJani Nikula debug-uart get routed to the D+ and D- pins of the usb 4041e52347bdSJani Nikula port and the regular usb controller gets disabled. 4042e52347bdSJani Nikula 4043e52347bdSJani Nikula root= [KNL] Root filesystem 4044e52347bdSJani Nikula See name_to_dev_t comment in init/do_mounts.c. 4045e52347bdSJani Nikula 4046e52347bdSJani Nikula rootdelay= [KNL] Delay (in seconds) to pause before attempting to 4047e52347bdSJani Nikula mount the root filesystem 4048e52347bdSJani Nikula 4049e52347bdSJani Nikula rootflags= [KNL] Set root filesystem mount option string 4050e52347bdSJani Nikula 4051e52347bdSJani Nikula rootfstype= [KNL] Set root filesystem type 4052e52347bdSJani Nikula 4053e52347bdSJani Nikula rootwait [KNL] Wait (indefinitely) for root device to show up. 4054e52347bdSJani Nikula Useful for devices that are detected asynchronously 4055e52347bdSJani Nikula (e.g. USB and MMC devices). 4056e52347bdSJani Nikula 4057e52347bdSJani Nikula rproc_mem=nn[KMG][@address] 4058e52347bdSJani Nikula [KNL,ARM,CMA] Remoteproc physical memory block. 4059e52347bdSJani Nikula Memory area to be used by remote processor image, 4060e52347bdSJani Nikula managed by CMA. 4061e52347bdSJani Nikula 4062e52347bdSJani Nikula rw [KNL] Mount root device read-write on boot 4063e52347bdSJani Nikula 4064e52347bdSJani Nikula S [KNL] Run init in single mode 4065e52347bdSJani Nikula 4066e52347bdSJani Nikula s390_iommu= [HW,S390] 4067e52347bdSJani Nikula Set s390 IOTLB flushing mode 4068e52347bdSJani Nikula strict 4069e52347bdSJani Nikula With strict flushing every unmap operation will result in 4070e52347bdSJani Nikula an IOTLB flush. Default is lazy flushing before reuse, 4071e52347bdSJani Nikula which is faster. 4072e52347bdSJani Nikula 4073e52347bdSJani Nikula sa1100ir [NET] 4074e52347bdSJani Nikula See drivers/net/irda/sa1100_ir.c. 4075e52347bdSJani Nikula 4076e52347bdSJani Nikula sbni= [NET] Granch SBNI12 leased line adapter 4077e52347bdSJani Nikula 4078e52347bdSJani Nikula sched_debug [KNL] Enables verbose scheduler debug messages. 4079e52347bdSJani Nikula 4080e52347bdSJani Nikula schedstats= [KNL,X86] Enable or disable scheduled statistics. 4081e52347bdSJani Nikula Allowed values are enable and disable. This feature 4082e52347bdSJani Nikula incurs a small amount of overhead in the scheduler 4083e52347bdSJani Nikula but is useful for debugging and performance tuning. 4084e52347bdSJani Nikula 4085e52347bdSJani Nikula skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate 4086e52347bdSJani Nikula xtime_lock contention on larger systems, and/or RCU lock 4087e52347bdSJani Nikula contention on all systems with CONFIG_MAXSMP set. 4088e52347bdSJani Nikula Format: { "0" | "1" } 4089e52347bdSJani Nikula 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1" 4090e52347bdSJani Nikula 1 -- enable. 4091e52347bdSJani Nikula Note: increases power consumption, thus should only be 4092e52347bdSJani Nikula enabled if running jitter sensitive (HPC/RT) workloads. 4093e52347bdSJani Nikula 4094e52347bdSJani Nikula security= [SECURITY] Choose a security module to enable at boot. 4095e52347bdSJani Nikula If this boot parameter is not specified, only the first 4096e52347bdSJani Nikula security module asking for security registration will be 4097e52347bdSJani Nikula loaded. An invalid security module name will be treated 4098e52347bdSJani Nikula as if no module has been chosen. 4099e52347bdSJani Nikula 4100e52347bdSJani Nikula selinux= [SELINUX] Disable or enable SELinux at boot time. 4101e52347bdSJani Nikula Format: { "0" | "1" } 4102e52347bdSJani Nikula See security/selinux/Kconfig help text. 4103e52347bdSJani Nikula 0 -- disable. 4104e52347bdSJani Nikula 1 -- enable. 4105e52347bdSJani Nikula Default value is set via kernel config option. 4106e52347bdSJani Nikula If enabled at boot time, /selinux/disable can be used 4107e52347bdSJani Nikula later to disable prior to initial policy load. 4108e52347bdSJani Nikula 4109e52347bdSJani Nikula apparmor= [APPARMOR] Disable or enable AppArmor at boot time 4110e52347bdSJani Nikula Format: { "0" | "1" } 4111e52347bdSJani Nikula See security/apparmor/Kconfig help text 4112e52347bdSJani Nikula 0 -- disable. 4113e52347bdSJani Nikula 1 -- enable. 4114e52347bdSJani Nikula Default value is set via kernel config option. 4115e52347bdSJani Nikula 4116e52347bdSJani Nikula serialnumber [BUGS=X86-32] 4117e52347bdSJani Nikula 4118e52347bdSJani Nikula shapers= [NET] 4119e52347bdSJani Nikula Maximal number of shapers. 4120e52347bdSJani Nikula 4121e52347bdSJani Nikula simeth= [IA-64] 4122e52347bdSJani Nikula simscsi= 4123e52347bdSJani Nikula 4124e52347bdSJani Nikula slram= [HW,MTD] 4125e52347bdSJani Nikula 4126e52347bdSJani Nikula slab_nomerge [MM] 4127e52347bdSJani Nikula Disable merging of slabs with similar size. May be 4128e52347bdSJani Nikula necessary if there is some reason to distinguish 41297660a6fdSKees Cook allocs to different slabs, especially in hardened 41307660a6fdSKees Cook environments where the risk of heap overflows and 41317660a6fdSKees Cook layout control by attackers can usually be 41327660a6fdSKees Cook frustrated by disabling merging. This will reduce 41337660a6fdSKees Cook most of the exposure of a heap attack to a single 41347660a6fdSKees Cook cache (risks via metadata attacks are mostly 41357660a6fdSKees Cook unchanged). Debug options disable merging on their 41367660a6fdSKees Cook own. 4137ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 4138e52347bdSJani Nikula 4139e52347bdSJani Nikula slab_max_order= [MM, SLAB] 4140e52347bdSJani Nikula Determines the maximum allowed order for slabs. 4141e52347bdSJani Nikula A high setting may cause OOMs due to memory 4142e52347bdSJani Nikula fragmentation. Defaults to 1 for systems with 4143e52347bdSJani Nikula more than 32MB of RAM, 0 otherwise. 4144e52347bdSJani Nikula 4145e52347bdSJani Nikula slub_debug[=options[,slabs]] [MM, SLUB] 4146e52347bdSJani Nikula Enabling slub_debug allows one to determine the 4147e52347bdSJani Nikula culprit if slab objects become corrupted. Enabling 4148e52347bdSJani Nikula slub_debug can create guard zones around objects and 4149e52347bdSJani Nikula may poison objects when not in use. Also tracks the 4150e52347bdSJani Nikula last alloc / free. For more information see 4151ad56b738SMike Rapoport Documentation/vm/slub.rst. 4152e52347bdSJani Nikula 41531663f26dSTejun Heo slub_memcg_sysfs= [MM, SLUB] 41541663f26dSTejun Heo Determines whether to enable sysfs directories for 41551663f26dSTejun Heo memory cgroup sub-caches. 1 to enable, 0 to disable. 41561663f26dSTejun Heo The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON. 41571663f26dSTejun Heo Enabling this can lead to a very high number of debug 41581663f26dSTejun Heo directories and files being created under 41591663f26dSTejun Heo /sys/kernel/slub. 41601663f26dSTejun Heo 4161e52347bdSJani Nikula slub_max_order= [MM, SLUB] 4162e52347bdSJani Nikula Determines the maximum allowed order for slabs. 4163e52347bdSJani Nikula A high setting may cause OOMs due to memory 4164e52347bdSJani Nikula fragmentation. For more information see 4165ad56b738SMike Rapoport Documentation/vm/slub.rst. 4166e52347bdSJani Nikula 4167e52347bdSJani Nikula slub_min_objects= [MM, SLUB] 4168e52347bdSJani Nikula The minimum number of objects per slab. SLUB will 4169e52347bdSJani Nikula increase the slab order up to slub_max_order to 4170e52347bdSJani Nikula generate a sufficiently large slab able to contain 4171e52347bdSJani Nikula the number of objects indicated. The higher the number 4172e52347bdSJani Nikula of objects the smaller the overhead of tracking slabs 4173e52347bdSJani Nikula and the less frequently locks need to be acquired. 4174ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 4175e52347bdSJani Nikula 4176e52347bdSJani Nikula slub_min_order= [MM, SLUB] 4177e52347bdSJani Nikula Determines the minimum page order for slabs. Must be 4178e52347bdSJani Nikula lower than slub_max_order. 4179ad56b738SMike Rapoport For more information see Documentation/vm/slub.rst. 4180e52347bdSJani Nikula 4181e52347bdSJani Nikula slub_nomerge [MM, SLUB] 4182e52347bdSJani Nikula Same with slab_nomerge. This is supported for legacy. 4183e52347bdSJani Nikula See slab_nomerge for more information. 4184e52347bdSJani Nikula 4185e52347bdSJani Nikula smart2= [HW] 4186e52347bdSJani Nikula Format: <io1>[,<io2>[,...,<io8>]] 4187e52347bdSJani Nikula 4188e52347bdSJani Nikula smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 4189e52347bdSJani Nikula smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 4190e52347bdSJani Nikula smsc-ircc2.ircc_sir= [HW] SIR base I/O port 4191e52347bdSJani Nikula smsc-ircc2.ircc_fir= [HW] FIR base I/O port 4192e52347bdSJani Nikula smsc-ircc2.ircc_irq= [HW] IRQ line 4193e52347bdSJani Nikula smsc-ircc2.ircc_dma= [HW] DMA channel 4194e52347bdSJani Nikula smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 4195e52347bdSJani Nikula 0: Toshiba Satellite 1800 (GP data pin select) 4196e52347bdSJani Nikula 1: Fast pin select (default) 4197e52347bdSJani Nikula 2: ATC IRMode 4198e52347bdSJani Nikula 4199e52347bdSJani Nikula smt [KNL,S390] Set the maximum number of threads (logical 4200e52347bdSJani Nikula CPUs) to use per physical CPU on systems capable of 4201e52347bdSJani Nikula symmetric multithreading (SMT). Will be capped to the 4202e52347bdSJani Nikula actual hardware limit. 4203e52347bdSJani Nikula Format: <integer> 4204e52347bdSJani Nikula Default: -1 (no limit) 4205e52347bdSJani Nikula 4206e52347bdSJani Nikula softlockup_panic= 4207e52347bdSJani Nikula [KNL] Should the soft-lockup detector generate panics. 4208e52347bdSJani Nikula Format: <integer> 4209e52347bdSJani Nikula 42103ce62385SBorislav Petkov A nonzero value instructs the soft-lockup detector 42113ce62385SBorislav Petkov to panic the machine when a soft-lockup occurs. This 42123ce62385SBorislav Petkov is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC 42133ce62385SBorislav Petkov which is the respective build-time switch to that 42143ce62385SBorislav Petkov functionality. 42153ce62385SBorislav Petkov 4216e52347bdSJani Nikula softlockup_all_cpu_backtrace= 4217e52347bdSJani Nikula [KNL] Should the soft-lockup detector generate 4218e52347bdSJani Nikula backtraces on all cpus. 4219e52347bdSJani Nikula Format: <integer> 4220e52347bdSJani Nikula 4221e52347bdSJani Nikula sonypi.*= [HW] Sony Programmable I/O Control Device driver 4222e52347bdSJani Nikula See Documentation/laptops/sonypi.txt 4223e52347bdSJani Nikula 4224da285121SDavid Woodhouse spectre_v2= [X86] Control mitigation of Spectre variant 2 4225da285121SDavid Woodhouse (indirect branch speculation) vulnerability. 4226fa1202efSThomas Gleixner The default operation protects the kernel from 4227fa1202efSThomas Gleixner user space attacks. 4228da285121SDavid Woodhouse 4229fa1202efSThomas Gleixner on - unconditionally enable, implies 4230fa1202efSThomas Gleixner spectre_v2_user=on 4231fa1202efSThomas Gleixner off - unconditionally disable, implies 4232fa1202efSThomas Gleixner spectre_v2_user=off 4233da285121SDavid Woodhouse auto - kernel detects whether your CPU model is 4234da285121SDavid Woodhouse vulnerable 4235da285121SDavid Woodhouse 4236da285121SDavid Woodhouse Selecting 'on' will, and 'auto' may, choose a 4237da285121SDavid Woodhouse mitigation method at run time according to the 4238da285121SDavid Woodhouse CPU, the available microcode, the setting of the 4239da285121SDavid Woodhouse CONFIG_RETPOLINE configuration option, and the 4240da285121SDavid Woodhouse compiler with which the kernel was built. 4241da285121SDavid Woodhouse 4242fa1202efSThomas Gleixner Selecting 'on' will also enable the mitigation 4243fa1202efSThomas Gleixner against user space to user space task attacks. 4244fa1202efSThomas Gleixner 4245fa1202efSThomas Gleixner Selecting 'off' will disable both the kernel and 4246fa1202efSThomas Gleixner the user space protections. 4247fa1202efSThomas Gleixner 4248da285121SDavid Woodhouse Specific mitigations can also be selected manually: 4249da285121SDavid Woodhouse 4250da285121SDavid Woodhouse retpoline - replace indirect branches 4251da285121SDavid Woodhouse retpoline,generic - google's original retpoline 4252da285121SDavid Woodhouse retpoline,amd - AMD-specific minimal thunk 4253da285121SDavid Woodhouse 4254da285121SDavid Woodhouse Not specifying this option is equivalent to 4255da285121SDavid Woodhouse spectre_v2=auto. 4256da285121SDavid Woodhouse 4257fa1202efSThomas Gleixner spectre_v2_user= 4258fa1202efSThomas Gleixner [X86] Control mitigation of Spectre variant 2 4259fa1202efSThomas Gleixner (indirect branch speculation) vulnerability between 4260fa1202efSThomas Gleixner user space tasks 4261fa1202efSThomas Gleixner 4262fa1202efSThomas Gleixner on - Unconditionally enable mitigations. Is 4263fa1202efSThomas Gleixner enforced by spectre_v2=on 4264fa1202efSThomas Gleixner 4265fa1202efSThomas Gleixner off - Unconditionally disable mitigations. Is 4266fa1202efSThomas Gleixner enforced by spectre_v2=off 4267fa1202efSThomas Gleixner 42687cc765a6SThomas Gleixner prctl - Indirect branch speculation is enabled, 42697cc765a6SThomas Gleixner but mitigation can be enabled via prctl 42707cc765a6SThomas Gleixner per thread. The mitigation control state 42717cc765a6SThomas Gleixner is inherited on fork. 42727cc765a6SThomas Gleixner 427355a97402SThomas Gleixner prctl,ibpb 427455a97402SThomas Gleixner - Like "prctl" above, but only STIBP is 427555a97402SThomas Gleixner controlled per thread. IBPB is issued 427655a97402SThomas Gleixner always when switching between different user 427755a97402SThomas Gleixner space processes. 427855a97402SThomas Gleixner 42796b3e64c2SThomas Gleixner seccomp 42806b3e64c2SThomas Gleixner - Same as "prctl" above, but all seccomp 42816b3e64c2SThomas Gleixner threads will enable the mitigation unless 42826b3e64c2SThomas Gleixner they explicitly opt out. 42836b3e64c2SThomas Gleixner 428455a97402SThomas Gleixner seccomp,ibpb 428555a97402SThomas Gleixner - Like "seccomp" above, but only STIBP is 428655a97402SThomas Gleixner controlled per thread. IBPB is issued 428755a97402SThomas Gleixner always when switching between different 428855a97402SThomas Gleixner user space processes. 428955a97402SThomas Gleixner 4290fa1202efSThomas Gleixner auto - Kernel selects the mitigation depending on 4291fa1202efSThomas Gleixner the available CPU features and vulnerability. 42926b3e64c2SThomas Gleixner 42936b3e64c2SThomas Gleixner Default mitigation: 42946b3e64c2SThomas Gleixner If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl" 4295fa1202efSThomas Gleixner 4296fa1202efSThomas Gleixner Not specifying this option is equivalent to 4297fa1202efSThomas Gleixner spectre_v2_user=auto. 4298fa1202efSThomas Gleixner 429924f7fc83SKonrad Rzeszutek Wilk spec_store_bypass_disable= 430024f7fc83SKonrad Rzeszutek Wilk [HW] Control Speculative Store Bypass (SSB) Disable mitigation 430124f7fc83SKonrad Rzeszutek Wilk (Speculative Store Bypass vulnerability) 430224f7fc83SKonrad Rzeszutek Wilk 430324f7fc83SKonrad Rzeszutek Wilk Certain CPUs are vulnerable to an exploit against a 430424f7fc83SKonrad Rzeszutek Wilk a common industry wide performance optimization known 430524f7fc83SKonrad Rzeszutek Wilk as "Speculative Store Bypass" in which recent stores 430624f7fc83SKonrad Rzeszutek Wilk to the same memory location may not be observed by 430724f7fc83SKonrad Rzeszutek Wilk later loads during speculative execution. The idea 430824f7fc83SKonrad Rzeszutek Wilk is that such stores are unlikely and that they can 430924f7fc83SKonrad Rzeszutek Wilk be detected prior to instruction retirement at the 431024f7fc83SKonrad Rzeszutek Wilk end of a particular speculation execution window. 431124f7fc83SKonrad Rzeszutek Wilk 431224f7fc83SKonrad Rzeszutek Wilk In vulnerable processors, the speculatively forwarded 431324f7fc83SKonrad Rzeszutek Wilk store can be used in a cache side channel attack, for 431424f7fc83SKonrad Rzeszutek Wilk example to read memory to which the attacker does not 431524f7fc83SKonrad Rzeszutek Wilk directly have access (e.g. inside sandboxed code). 431624f7fc83SKonrad Rzeszutek Wilk 431724f7fc83SKonrad Rzeszutek Wilk This parameter controls whether the Speculative Store 431824f7fc83SKonrad Rzeszutek Wilk Bypass optimization is used. 431924f7fc83SKonrad Rzeszutek Wilk 43206b4c1360SMichael Ellerman On x86 the options are: 43216b4c1360SMichael Ellerman 432224f7fc83SKonrad Rzeszutek Wilk on - Unconditionally disable Speculative Store Bypass 432324f7fc83SKonrad Rzeszutek Wilk off - Unconditionally enable Speculative Store Bypass 432424f7fc83SKonrad Rzeszutek Wilk auto - Kernel detects whether the CPU model contains an 432524f7fc83SKonrad Rzeszutek Wilk implementation of Speculative Store Bypass and 4326f21b53b2SKees Cook picks the most appropriate mitigation. If the 4327f21b53b2SKees Cook CPU is not vulnerable, "off" is selected. If the 4328f21b53b2SKees Cook CPU is vulnerable the default mitigation is 4329f21b53b2SKees Cook architecture and Kconfig dependent. See below. 4330a73ec77eSThomas Gleixner prctl - Control Speculative Store Bypass per thread 4331a73ec77eSThomas Gleixner via prctl. Speculative Store Bypass is enabled 4332a73ec77eSThomas Gleixner for a process by default. The state of the control 4333a73ec77eSThomas Gleixner is inherited on fork. 4334f21b53b2SKees Cook seccomp - Same as "prctl" above, but all seccomp threads 4335f21b53b2SKees Cook will disable SSB unless they explicitly opt out. 433624f7fc83SKonrad Rzeszutek Wilk 4337f21b53b2SKees Cook Default mitigations: 4338f21b53b2SKees Cook X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl" 4339f21b53b2SKees Cook 43406b4c1360SMichael Ellerman On powerpc the options are: 43416b4c1360SMichael Ellerman 43426b4c1360SMichael Ellerman on,auto - On Power8 and Power9 insert a store-forwarding 43436b4c1360SMichael Ellerman barrier on kernel entry and exit. On Power7 43446b4c1360SMichael Ellerman perform a software flush on kernel entry and 43456b4c1360SMichael Ellerman exit. 43466b4c1360SMichael Ellerman off - No action. 43476b4c1360SMichael Ellerman 43486b4c1360SMichael Ellerman Not specifying this option is equivalent to 43496b4c1360SMichael Ellerman spec_store_bypass_disable=auto. 43506b4c1360SMichael Ellerman 4351e52347bdSJani Nikula spia_io_base= [HW,MTD] 4352e52347bdSJani Nikula spia_fio_base= 4353e52347bdSJani Nikula spia_pedr= 4354e52347bdSJani Nikula spia_peddr= 4355e52347bdSJani Nikula 4356c350c008SPaul E. McKenney srcutree.counter_wrap_check [KNL] 4357c350c008SPaul E. McKenney Specifies how frequently to check for 4358c350c008SPaul E. McKenney grace-period sequence counter wrap for the 4359c350c008SPaul E. McKenney srcu_data structure's ->srcu_gp_seq_needed field. 4360c350c008SPaul E. McKenney The greater the number of bits set in this kernel 4361c350c008SPaul E. McKenney parameter, the less frequently counter wrap will 4362c350c008SPaul E. McKenney be checked for. Note that the bottom two bits 4363c350c008SPaul E. McKenney are ignored. 4364c350c008SPaul E. McKenney 436522607d66SPaul E. McKenney srcutree.exp_holdoff [KNL] 436622607d66SPaul E. McKenney Specifies how many nanoseconds must elapse 436722607d66SPaul E. McKenney since the end of the last SRCU grace period for 436822607d66SPaul E. McKenney a given srcu_struct until the next normal SRCU 436922607d66SPaul E. McKenney grace period will be considered for automatic 437022607d66SPaul E. McKenney expediting. Set to zero to disable automatic 437122607d66SPaul E. McKenney expediting. 437222607d66SPaul E. McKenney 4373a43ae4dfSMarc Zyngier ssbd= [ARM64,HW] 4374a43ae4dfSMarc Zyngier Speculative Store Bypass Disable control 4375a43ae4dfSMarc Zyngier 4376a43ae4dfSMarc Zyngier On CPUs that are vulnerable to the Speculative 4377a43ae4dfSMarc Zyngier Store Bypass vulnerability and offer a 4378a43ae4dfSMarc Zyngier firmware based mitigation, this parameter 4379a43ae4dfSMarc Zyngier indicates how the mitigation should be used: 4380a43ae4dfSMarc Zyngier 4381a43ae4dfSMarc Zyngier force-on: Unconditionally enable mitigation for 4382a43ae4dfSMarc Zyngier for both kernel and userspace 4383a43ae4dfSMarc Zyngier force-off: Unconditionally disable mitigation for 4384a43ae4dfSMarc Zyngier for both kernel and userspace 4385a43ae4dfSMarc Zyngier kernel: Always enable mitigation in the 4386a43ae4dfSMarc Zyngier kernel, and offer a prctl interface 4387a43ae4dfSMarc Zyngier to allow userspace to register its 4388a43ae4dfSMarc Zyngier interest in being mitigated too. 4389a43ae4dfSMarc Zyngier 43901be7107fSHugh Dickins stack_guard_gap= [MM] 43911be7107fSHugh Dickins override the default stack gap protection. The value 43921be7107fSHugh Dickins is in page units and it defines how many pages prior 43931be7107fSHugh Dickins to (for stacks growing down) resp. after (for stacks 43941be7107fSHugh Dickins growing up) the main stack are reserved for no other 43951be7107fSHugh Dickins mapping. Default value is 256 pages. 43961be7107fSHugh Dickins 4397e52347bdSJani Nikula stacktrace [FTRACE] 4398e52347bdSJani Nikula Enabled the stack tracer on boot up. 4399e52347bdSJani Nikula 4400e52347bdSJani Nikula stacktrace_filter=[function-list] 4401e52347bdSJani Nikula [FTRACE] Limit the functions that the stack tracer 4402e52347bdSJani Nikula will trace at boot up. function-list is a comma separated 4403e52347bdSJani Nikula list of functions. This list can be changed at run 4404e52347bdSJani Nikula time by the stack_trace_filter file in the debugfs 4405e52347bdSJani Nikula tracing directory. Note, this enables stack tracing 4406e52347bdSJani Nikula and the stacktrace above is not needed. 4407e52347bdSJani Nikula 4408e52347bdSJani Nikula sti= [PARISC,HW] 4409e52347bdSJani Nikula Format: <num> 4410e52347bdSJani Nikula Set the STI (builtin display/keyboard on the HP-PARISC 4411e52347bdSJani Nikula machines) console (graphic card) which should be used 4412e52347bdSJani Nikula as the initial boot-console. 4413e52347bdSJani Nikula See also comment in drivers/video/console/sticore.c. 4414e52347bdSJani Nikula 4415e52347bdSJani Nikula sti_font= [HW] 4416e52347bdSJani Nikula See comment in drivers/video/console/sticore.c. 4417e52347bdSJani Nikula 4418e52347bdSJani Nikula stifb= [HW] 4419e52347bdSJani Nikula Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 4420e52347bdSJani Nikula 4421e52347bdSJani Nikula sunrpc.min_resvport= 4422e52347bdSJani Nikula sunrpc.max_resvport= 4423e52347bdSJani Nikula [NFS,SUNRPC] 4424e52347bdSJani Nikula SunRPC servers often require that client requests 4425e52347bdSJani Nikula originate from a privileged port (i.e. a port in the 4426e52347bdSJani Nikula range 0 < portnr < 1024). 4427e52347bdSJani Nikula An administrator who wishes to reserve some of these 4428e52347bdSJani Nikula ports for other uses may adjust the range that the 4429e52347bdSJani Nikula kernel's sunrpc client considers to be privileged 4430e52347bdSJani Nikula using these two parameters to set the minimum and 4431e52347bdSJani Nikula maximum port values. 4432e52347bdSJani Nikula 4433e52347bdSJani Nikula sunrpc.svc_rpc_per_connection_limit= 4434e52347bdSJani Nikula [NFS,SUNRPC] 4435e52347bdSJani Nikula Limit the number of requests that the server will 4436e52347bdSJani Nikula process in parallel from a single connection. 4437e52347bdSJani Nikula The default value is 0 (no limit). 4438e52347bdSJani Nikula 4439e52347bdSJani Nikula sunrpc.pool_mode= 4440e52347bdSJani Nikula [NFS] 4441e52347bdSJani Nikula Control how the NFS server code allocates CPUs to 4442e52347bdSJani Nikula service thread pools. Depending on how many NICs 4443e52347bdSJani Nikula you have and where their interrupts are bound, this 4444e52347bdSJani Nikula option will affect which CPUs will do NFS serving. 4445e52347bdSJani Nikula Note: this parameter cannot be changed while the 4446e52347bdSJani Nikula NFS server is running. 4447e52347bdSJani Nikula 4448e52347bdSJani Nikula auto the server chooses an appropriate mode 4449e52347bdSJani Nikula automatically using heuristics 4450e52347bdSJani Nikula global a single global pool contains all CPUs 4451e52347bdSJani Nikula percpu one pool for each CPU 4452e52347bdSJani Nikula pernode one pool for each NUMA node (equivalent 4453e52347bdSJani Nikula to global on non-NUMA machines) 4454e52347bdSJani Nikula 4455e52347bdSJani Nikula sunrpc.tcp_slot_table_entries= 4456e52347bdSJani Nikula sunrpc.udp_slot_table_entries= 4457e52347bdSJani Nikula [NFS,SUNRPC] 4458e52347bdSJani Nikula Sets the upper limit on the number of simultaneous 4459e52347bdSJani Nikula RPC calls that can be sent from the client to a 4460e52347bdSJani Nikula server. Increasing these values may allow you to 4461e52347bdSJani Nikula improve throughput, but will also increase the 4462e52347bdSJani Nikula amount of memory reserved for use by the client. 4463e52347bdSJani Nikula 4464e52347bdSJani Nikula suspend.pm_test_delay= 4465e52347bdSJani Nikula [SUSPEND] 4466e52347bdSJani Nikula Sets the number of seconds to remain in a suspend test 4467e52347bdSJani Nikula mode before resuming the system (see 4468e52347bdSJani Nikula /sys/power/pm_test). Only available when CONFIG_PM_DEBUG 4469e52347bdSJani Nikula is set. Default value is 5. 4470e52347bdSJani Nikula 4471e52347bdSJani Nikula swapaccount=[0|1] 4472e52347bdSJani Nikula [KNL] Enable accounting of swap in memory resource 4473e52347bdSJani Nikula controller if no parameter or 1 is given or disable 4474e52347bdSJani Nikula it if 0 is given (See Documentation/cgroup-v1/memory.txt) 4475e52347bdSJani Nikula 4476e52347bdSJani Nikula swiotlb= [ARM,IA-64,PPC,MIPS,X86] 4477fff5d992SGeert Uytterhoeven Format: { <int> | force | noforce } 4478e52347bdSJani Nikula <int> -- Number of I/O TLB slabs 4479e52347bdSJani Nikula force -- force using of bounce buffers even if they 4480e52347bdSJani Nikula wouldn't be automatically used by the kernel 4481fff5d992SGeert Uytterhoeven noforce -- Never use bounce buffers (for debugging) 4482e52347bdSJani Nikula 4483e52347bdSJani Nikula switches= [HW,M68k] 4484e52347bdSJani Nikula 4485e52347bdSJani Nikula sysfs.deprecated=0|1 [KNL] 4486e52347bdSJani Nikula Enable/disable old style sysfs layout for old udev 4487e52347bdSJani Nikula on older distributions. When this option is enabled 4488e52347bdSJani Nikula very new udev will not work anymore. When this option 4489e52347bdSJani Nikula is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) 4490e52347bdSJani Nikula in older udev will not work anymore. 4491e52347bdSJani Nikula Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in 4492e52347bdSJani Nikula the kernel configuration. 4493e52347bdSJani Nikula 4494e52347bdSJani Nikula sysrq_always_enabled 4495e52347bdSJani Nikula [KNL] 4496e52347bdSJani Nikula Ignore sysrq setting - this boot parameter will 4497e52347bdSJani Nikula neutralize any effect of /proc/sys/kernel/sysrq. 4498e52347bdSJani Nikula Useful for debugging. 4499e52347bdSJani Nikula 4500e52347bdSJani Nikula tcpmhash_entries= [KNL,NET] 4501e52347bdSJani Nikula Set the number of tcp_metrics_hash slots. 4502e52347bdSJani Nikula Default value is 8192 or 16384 depending on total 4503e52347bdSJani Nikula ram pages. This is used to specify the TCP metrics 4504e52347bdSJani Nikula cache size. See Documentation/networking/ip-sysctl.txt 4505e52347bdSJani Nikula "tcp_no_metrics_save" section for more details. 4506e52347bdSJani Nikula 4507e52347bdSJani Nikula tdfx= [HW,DRM] 4508e52347bdSJani Nikula 4509e52347bdSJani Nikula test_suspend= [SUSPEND][,N] 4510e52347bdSJani Nikula Specify "mem" (for Suspend-to-RAM) or "standby" (for 4511e52347bdSJani Nikula standby suspend) or "freeze" (for suspend type freeze) 4512e52347bdSJani Nikula as the system sleep state during system startup with 4513e52347bdSJani Nikula the optional capability to repeat N number of times. 4514e52347bdSJani Nikula The system is woken from this state using a 4515e52347bdSJani Nikula wakeup-capable RTC alarm. 4516e52347bdSJani Nikula 4517e52347bdSJani Nikula thash_entries= [KNL,NET] 4518e52347bdSJani Nikula Set number of hash buckets for TCP connection 4519e52347bdSJani Nikula 4520e52347bdSJani Nikula thermal.act= [HW,ACPI] 4521e52347bdSJani Nikula -1: disable all active trip points in all thermal zones 4522e52347bdSJani Nikula <degrees C>: override all lowest active trip points 4523e52347bdSJani Nikula 4524e52347bdSJani Nikula thermal.crt= [HW,ACPI] 4525e52347bdSJani Nikula -1: disable all critical trip points in all thermal zones 4526e52347bdSJani Nikula <degrees C>: override all critical trip points 4527e52347bdSJani Nikula 4528e52347bdSJani Nikula thermal.nocrt= [HW,ACPI] 4529e52347bdSJani Nikula Set to disable actions on ACPI thermal zone 4530e52347bdSJani Nikula critical and hot trip points. 4531e52347bdSJani Nikula 4532e52347bdSJani Nikula thermal.off= [HW,ACPI] 4533e52347bdSJani Nikula 1: disable ACPI thermal control 4534e52347bdSJani Nikula 4535e52347bdSJani Nikula thermal.psv= [HW,ACPI] 4536e52347bdSJani Nikula -1: disable all passive trip points 4537e52347bdSJani Nikula <degrees C>: override all passive trip points to this 4538e52347bdSJani Nikula value 4539e52347bdSJani Nikula 4540e52347bdSJani Nikula thermal.tzp= [HW,ACPI] 4541e52347bdSJani Nikula Specify global default ACPI thermal zone polling rate 4542e52347bdSJani Nikula <deci-seconds>: poll all this frequency 4543e52347bdSJani Nikula 0: no polling (default) 4544e52347bdSJani Nikula 4545e52347bdSJani Nikula threadirqs [KNL] 4546e52347bdSJani Nikula Force threading of all interrupt handlers except those 4547e52347bdSJani Nikula marked explicitly IRQF_NO_THREAD. 4548e52347bdSJani Nikula 4549e52347bdSJani Nikula tmem [KNL,XEN] 4550e52347bdSJani Nikula Enable the Transcendent memory driver if built-in. 4551e52347bdSJani Nikula 4552e52347bdSJani Nikula tmem.cleancache=0|1 [KNL, XEN] 4553e52347bdSJani Nikula Default is on (1). Disable the usage of the cleancache 4554e52347bdSJani Nikula API to send anonymous pages to the hypervisor. 4555e52347bdSJani Nikula 4556e52347bdSJani Nikula tmem.frontswap=0|1 [KNL, XEN] 4557e52347bdSJani Nikula Default is on (1). Disable the usage of the frontswap 4558e52347bdSJani Nikula API to send swap pages to the hypervisor. If disabled 4559e52347bdSJani Nikula the selfballooning and selfshrinking are force disabled. 4560e52347bdSJani Nikula 4561e52347bdSJani Nikula tmem.selfballooning=0|1 [KNL, XEN] 4562e52347bdSJani Nikula Default is on (1). Disable the driving of swap pages 4563e52347bdSJani Nikula to the hypervisor. 4564e52347bdSJani Nikula 4565e52347bdSJani Nikula tmem.selfshrinking=0|1 [KNL, XEN] 4566e52347bdSJani Nikula Default is on (1). Partial swapoff that immediately 4567e52347bdSJani Nikula transfers pages from Xen hypervisor back to the 4568e52347bdSJani Nikula kernel based on different criteria. 4569e52347bdSJani Nikula 4570e52347bdSJani Nikula topology= [S390] 4571e52347bdSJani Nikula Format: {off | on} 4572e52347bdSJani Nikula Specify if the kernel should make use of the cpu 4573e52347bdSJani Nikula topology information if the hardware supports this. 4574e52347bdSJani Nikula The scheduler will make use of this information and 4575e52347bdSJani Nikula e.g. base its process migration decisions on it. 4576e52347bdSJani Nikula Default is on. 4577e52347bdSJani Nikula 4578e52347bdSJani Nikula topology_updates= [KNL, PPC, NUMA] 4579e52347bdSJani Nikula Format: {off} 4580e52347bdSJani Nikula Specify if the kernel should ignore (off) 4581e52347bdSJani Nikula topology updates sent by the hypervisor to this 4582e52347bdSJani Nikula LPAR. 4583e52347bdSJani Nikula 4584e52347bdSJani Nikula tp720= [HW,PS2] 4585e52347bdSJani Nikula 4586e52347bdSJani Nikula tpm_suspend_pcr=[HW,TPM] 4587e52347bdSJani Nikula Format: integer pcr id 4588e52347bdSJani Nikula Specify that at suspend time, the tpm driver 4589e52347bdSJani Nikula should extend the specified pcr with zeros, 4590e52347bdSJani Nikula as a workaround for some chips which fail to 4591e52347bdSJani Nikula flush the last written pcr on TPM_SaveState. 4592e52347bdSJani Nikula This will guarantee that all the other pcrs 4593e52347bdSJani Nikula are saved. 4594e52347bdSJani Nikula 4595e52347bdSJani Nikula trace_buf_size=nn[KMG] 4596e52347bdSJani Nikula [FTRACE] will set tracing buffer size on each cpu. 4597e52347bdSJani Nikula 4598e52347bdSJani Nikula trace_event=[event-list] 4599e52347bdSJani Nikula [FTRACE] Set and start specified trace events in order 4600e52347bdSJani Nikula to facilitate early boot debugging. The event-list is a 4601e52347bdSJani Nikula comma separated list of trace events to enable. See 46025fb94e9cSMauro Carvalho Chehab also Documentation/trace/events.rst 4603e52347bdSJani Nikula 4604e52347bdSJani Nikula trace_options=[option-list] 4605e52347bdSJani Nikula [FTRACE] Enable or disable tracer options at boot. 4606e52347bdSJani Nikula The option-list is a comma delimited list of options 4607e52347bdSJani Nikula that can be enabled or disabled just as if you were 4608e52347bdSJani Nikula to echo the option name into 4609e52347bdSJani Nikula 4610e52347bdSJani Nikula /sys/kernel/debug/tracing/trace_options 4611e52347bdSJani Nikula 4612e52347bdSJani Nikula For example, to enable stacktrace option (to dump the 4613e52347bdSJani Nikula stack trace of each event), add to the command line: 4614e52347bdSJani Nikula 4615e52347bdSJani Nikula trace_options=stacktrace 4616e52347bdSJani Nikula 46175fb94e9cSMauro Carvalho Chehab See also Documentation/trace/ftrace.rst "trace options" 4618e52347bdSJani Nikula section. 4619e52347bdSJani Nikula 4620e52347bdSJani Nikula tp_printk[FTRACE] 4621e52347bdSJani Nikula Have the tracepoints sent to printk as well as the 4622e52347bdSJani Nikula tracing ring buffer. This is useful for early boot up 4623e52347bdSJani Nikula where the system hangs or reboots and does not give the 4624e52347bdSJani Nikula option for reading the tracing buffer or performing a 4625e52347bdSJani Nikula ftrace_dump_on_oops. 4626e52347bdSJani Nikula 4627e52347bdSJani Nikula To turn off having tracepoints sent to printk, 4628e52347bdSJani Nikula echo 0 > /proc/sys/kernel/tracepoint_printk 4629e52347bdSJani Nikula Note, echoing 1 into this file without the 4630e52347bdSJani Nikula tracepoint_printk kernel cmdline option has no effect. 4631e52347bdSJani Nikula 4632e52347bdSJani Nikula ** CAUTION ** 4633e52347bdSJani Nikula 4634e52347bdSJani Nikula Having tracepoints sent to printk() and activating high 4635e52347bdSJani Nikula frequency tracepoints such as irq or sched, can cause 4636e52347bdSJani Nikula the system to live lock. 4637e52347bdSJani Nikula 4638e52347bdSJani Nikula traceoff_on_warning 4639e52347bdSJani Nikula [FTRACE] enable this option to disable tracing when a 4640e52347bdSJani Nikula warning is hit. This turns off "tracing_on". Tracing can 4641e52347bdSJani Nikula be enabled again by echoing '1' into the "tracing_on" 4642e52347bdSJani Nikula file located in /sys/kernel/debug/tracing/ 4643e52347bdSJani Nikula 4644e52347bdSJani Nikula This option is useful, as it disables the trace before 4645e52347bdSJani Nikula the WARNING dump is called, which prevents the trace to 4646e52347bdSJani Nikula be filled with content caused by the warning output. 4647e52347bdSJani Nikula 4648e52347bdSJani Nikula This option can also be set at run time via the sysctl 4649e52347bdSJani Nikula option: kernel/traceoff_on_warning 4650e52347bdSJani Nikula 4651e52347bdSJani Nikula transparent_hugepage= 4652e52347bdSJani Nikula [KNL] 4653e52347bdSJani Nikula Format: [always|madvise|never] 4654e52347bdSJani Nikula Can be used to control the default behavior of the system 4655e52347bdSJani Nikula with respect to transparent hugepages. 465645c9a74fSMike Rapoport See Documentation/admin-guide/mm/transhuge.rst 465745c9a74fSMike Rapoport for more details. 4658e52347bdSJani Nikula 4659e52347bdSJani Nikula tsc= Disable clocksource stability checks for TSC. 4660e52347bdSJani Nikula Format: <string> 4661e52347bdSJani Nikula [x86] reliable: mark tsc clocksource as reliable, this 4662e52347bdSJani Nikula disables clocksource verification at runtime, as well 4663e52347bdSJani Nikula as the stability checks done at bootup. Used to enable 4664e52347bdSJani Nikula high-resolution timer mode on older hardware, and in 4665e52347bdSJani Nikula virtualized environment. 4666e52347bdSJani Nikula [x86] noirqtime: Do not use TSC to do irq accounting. 4667e52347bdSJani Nikula Used to run time disable IRQ_TIME_ACCOUNTING on any 4668e52347bdSJani Nikula platforms where RDTSC is slow and this accounting 4669e52347bdSJani Nikula can add overhead. 46706be53520SDou Liyang [x86] unstable: mark the TSC clocksource as unstable, this 46716be53520SDou Liyang marks the TSC unconditionally unstable at bootup and 46726be53520SDou Liyang avoids any further wobbles once the TSC watchdog notices. 4673e52347bdSJani Nikula 4674e52347bdSJani Nikula turbografx.map[2|3]= [HW,JOY] 4675e52347bdSJani Nikula TurboGraFX parallel port interface 4676e52347bdSJani Nikula Format: 4677e52347bdSJani Nikula <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 46781752118dSTom Saeger See also Documentation/input/devices/joystick-parport.rst 4679e52347bdSJani Nikula 4680e52347bdSJani Nikula udbg-immortal [PPC] When debugging early kernel crashes that 4681e52347bdSJani Nikula happen after console_init() and before a proper 4682e52347bdSJani Nikula console driver takes over, this boot options might 4683e52347bdSJani Nikula help "seeing" what's going on. 4684e52347bdSJani Nikula 4685e52347bdSJani Nikula uhash_entries= [KNL,NET] 4686e52347bdSJani Nikula Set number of hash buckets for UDP/UDP-Lite connections 4687e52347bdSJani Nikula 4688e52347bdSJani Nikula uhci-hcd.ignore_oc= 4689e52347bdSJani Nikula [USB] Ignore overcurrent events (default N). 4690e52347bdSJani Nikula Some badly-designed motherboards generate lots of 4691e52347bdSJani Nikula bogus events, for ports that aren't wired to 4692e52347bdSJani Nikula anything. Set this parameter to avoid log spamming. 4693e52347bdSJani Nikula Note that genuine overcurrent events won't be 4694e52347bdSJani Nikula reported either. 4695e52347bdSJani Nikula 4696e52347bdSJani Nikula unknown_nmi_panic 4697e52347bdSJani Nikula [X86] Cause panic on unknown NMI. 4698e52347bdSJani Nikula 4699e52347bdSJani Nikula usbcore.authorized_default= 4700e52347bdSJani Nikula [USB] Default USB device authorization: 4701e52347bdSJani Nikula (default -1 = authorized except for wireless USB, 4702e52347bdSJani Nikula 0 = not authorized, 1 = authorized) 4703e52347bdSJani Nikula 4704e52347bdSJani Nikula usbcore.autosuspend= 4705e52347bdSJani Nikula [USB] The autosuspend time delay (in seconds) used 4706e52347bdSJani Nikula for newly-detected USB devices (default 2). This 4707e52347bdSJani Nikula is the time required before an idle device will be 4708e52347bdSJani Nikula autosuspended. Devices for which the delay is set 4709e52347bdSJani Nikula to a negative value won't be autosuspended at all. 4710e52347bdSJani Nikula 4711e52347bdSJani Nikula usbcore.usbfs_snoop= 4712e52347bdSJani Nikula [USB] Set to log all usbfs traffic (default 0 = off). 4713e52347bdSJani Nikula 4714e52347bdSJani Nikula usbcore.usbfs_snoop_max= 4715e52347bdSJani Nikula [USB] Maximum number of bytes to snoop in each URB 4716e52347bdSJani Nikula (default = 65536). 4717e52347bdSJani Nikula 4718e52347bdSJani Nikula usbcore.blinkenlights= 4719e52347bdSJani Nikula [USB] Set to cycle leds on hubs (default 0 = off). 4720e52347bdSJani Nikula 4721e52347bdSJani Nikula usbcore.old_scheme_first= 4722e52347bdSJani Nikula [USB] Start with the old device initialization 4723bd0e6c96SZeng Tao scheme, applies only to low and full-speed devices 4724bd0e6c96SZeng Tao (default 0 = off). 4725e52347bdSJani Nikula 4726e52347bdSJani Nikula usbcore.usbfs_memory_mb= 4727e52347bdSJani Nikula [USB] Memory limit (in MB) for buffers allocated by 4728e52347bdSJani Nikula usbfs (default = 16, 0 = max = 2047). 4729e52347bdSJani Nikula 4730e52347bdSJani Nikula usbcore.use_both_schemes= 4731e52347bdSJani Nikula [USB] Try the other device initialization scheme 4732e52347bdSJani Nikula if the first one fails (default 1 = enabled). 4733e52347bdSJani Nikula 4734e52347bdSJani Nikula usbcore.initial_descriptor_timeout= 4735e52347bdSJani Nikula [USB] Specifies timeout for the initial 64-byte 4736e52347bdSJani Nikula USB_REQ_GET_DESCRIPTOR request in milliseconds 4737e52347bdSJani Nikula (default 5000 = 5.0 seconds). 4738e52347bdSJani Nikula 4739e52347bdSJani Nikula usbcore.nousb [USB] Disable the USB subsystem 4740e52347bdSJani Nikula 4741027bd6caSKai-Heng Feng usbcore.quirks= 4742027bd6caSKai-Heng Feng [USB] A list of quirk entries to augment the built-in 4743027bd6caSKai-Heng Feng usb core quirk list. List entries are separated by 4744027bd6caSKai-Heng Feng commas. Each entry has the form 4745027bd6caSKai-Heng Feng VendorID:ProductID:Flags. The IDs are 4-digit hex 4746027bd6caSKai-Heng Feng numbers and Flags is a set of letters. Each letter 4747027bd6caSKai-Heng Feng will change the built-in quirk; setting it if it is 4748027bd6caSKai-Heng Feng clear and clearing it if it is set. The letters have 4749027bd6caSKai-Heng Feng the following meanings: 4750027bd6caSKai-Heng Feng a = USB_QUIRK_STRING_FETCH_255 (string 4751027bd6caSKai-Heng Feng descriptors must not be fetched using 4752027bd6caSKai-Heng Feng a 255-byte read); 4753027bd6caSKai-Heng Feng b = USB_QUIRK_RESET_RESUME (device can't resume 4754027bd6caSKai-Heng Feng correctly so reset it instead); 4755027bd6caSKai-Heng Feng c = USB_QUIRK_NO_SET_INTF (device can't handle 4756027bd6caSKai-Heng Feng Set-Interface requests); 4757027bd6caSKai-Heng Feng d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't 4758027bd6caSKai-Heng Feng handle its Configuration or Interface 4759027bd6caSKai-Heng Feng strings); 4760027bd6caSKai-Heng Feng e = USB_QUIRK_RESET (device can't be reset 4761027bd6caSKai-Heng Feng (e.g morph devices), don't use reset); 4762027bd6caSKai-Heng Feng f = USB_QUIRK_HONOR_BNUMINTERFACES (device has 4763027bd6caSKai-Heng Feng more interface descriptions than the 4764027bd6caSKai-Heng Feng bNumInterfaces count, and can't handle 4765027bd6caSKai-Heng Feng talking to these interfaces); 4766027bd6caSKai-Heng Feng g = USB_QUIRK_DELAY_INIT (device needs a pause 4767027bd6caSKai-Heng Feng during initialization, after we read 4768027bd6caSKai-Heng Feng the device descriptor); 4769027bd6caSKai-Heng Feng h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For 4770027bd6caSKai-Heng Feng high speed and super speed interrupt 4771027bd6caSKai-Heng Feng endpoints, the USB 2.0 and USB 3.0 spec 4772027bd6caSKai-Heng Feng require the interval in microframes (1 4773027bd6caSKai-Heng Feng microframe = 125 microseconds) to be 4774027bd6caSKai-Heng Feng calculated as interval = 2 ^ 4775027bd6caSKai-Heng Feng (bInterval-1). 4776027bd6caSKai-Heng Feng Devices with this quirk report their 4777027bd6caSKai-Heng Feng bInterval as the result of this 4778027bd6caSKai-Heng Feng calculation instead of the exponent 4779027bd6caSKai-Heng Feng variable used in the calculation); 4780027bd6caSKai-Heng Feng i = USB_QUIRK_DEVICE_QUALIFIER (device can't 4781027bd6caSKai-Heng Feng handle device_qualifier descriptor 4782027bd6caSKai-Heng Feng requests); 4783027bd6caSKai-Heng Feng j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device 4784027bd6caSKai-Heng Feng generates spurious wakeup, ignore 4785027bd6caSKai-Heng Feng remote wakeup capability); 4786027bd6caSKai-Heng Feng k = USB_QUIRK_NO_LPM (device can't handle Link 4787027bd6caSKai-Heng Feng Power Management); 4788027bd6caSKai-Heng Feng l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL 4789027bd6caSKai-Heng Feng (Device reports its bInterval as linear 4790027bd6caSKai-Heng Feng frames instead of the USB 2.0 4791027bd6caSKai-Heng Feng calculation); 4792027bd6caSKai-Heng Feng m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs 4793027bd6caSKai-Heng Feng to be disconnected before suspend to 47944d8d5a39SKai-Heng Feng prevent spurious wakeup); 47954d8d5a39SKai-Heng Feng n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a 47964d8d5a39SKai-Heng Feng pause after every control message); 4797781f0766SKai-Heng Feng o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra 4798781f0766SKai-Heng Feng delay after resetting its port); 4799027bd6caSKai-Heng Feng Example: quirks=0781:5580:bk,0a5c:5834:gij 4800027bd6caSKai-Heng Feng 4801e52347bdSJani Nikula usbhid.mousepoll= 4802e52347bdSJani Nikula [USBHID] The interval which mice are to be polled at. 4803e52347bdSJani Nikula 4804933bfe4dSTobias Jakobi usbhid.jspoll= 4805933bfe4dSTobias Jakobi [USBHID] The interval which joysticks are to be polled at. 4806933bfe4dSTobias Jakobi 48072ddc8e2dSFilip Alac usbhid.kbpoll= 48082ddc8e2dSFilip Alac [USBHID] The interval which keyboards are to be polled at. 48092ddc8e2dSFilip Alac 4810e52347bdSJani Nikula usb-storage.delay_use= 4811e52347bdSJani Nikula [UMS] The delay in seconds before a new device is 4812e52347bdSJani Nikula scanned for Logical Units (default 1). 4813e52347bdSJani Nikula 4814e52347bdSJani Nikula usb-storage.quirks= 4815e52347bdSJani Nikula [UMS] A list of quirks entries to supplement or 4816e52347bdSJani Nikula override the built-in unusual_devs list. List 4817e52347bdSJani Nikula entries are separated by commas. Each entry has 4818e52347bdSJani Nikula the form VID:PID:Flags where VID and PID are Vendor 4819e52347bdSJani Nikula and Product ID values (4-digit hex numbers) and 4820e52347bdSJani Nikula Flags is a set of characters, each corresponding 4821e52347bdSJani Nikula to a common usb-storage quirk flag as follows: 4822e52347bdSJani Nikula a = SANE_SENSE (collect more than 18 bytes 4823e52347bdSJani Nikula of sense data); 4824e52347bdSJani Nikula b = BAD_SENSE (don't collect more than 18 4825e52347bdSJani Nikula bytes of sense data); 4826e52347bdSJani Nikula c = FIX_CAPACITY (decrease the reported 4827e52347bdSJani Nikula device capacity by one sector); 4828e52347bdSJani Nikula d = NO_READ_DISC_INFO (don't use 4829e52347bdSJani Nikula READ_DISC_INFO command); 4830e52347bdSJani Nikula e = NO_READ_CAPACITY_16 (don't use 4831e52347bdSJani Nikula READ_CAPACITY_16 command); 4832e52347bdSJani Nikula f = NO_REPORT_OPCODES (don't use report opcodes 4833e52347bdSJani Nikula command, uas only); 4834e52347bdSJani Nikula g = MAX_SECTORS_240 (don't transfer more than 4835e52347bdSJani Nikula 240 sectors at a time, uas only); 4836e52347bdSJani Nikula h = CAPACITY_HEURISTICS (decrease the 4837e52347bdSJani Nikula reported device capacity by one 4838e52347bdSJani Nikula sector if the number is odd); 4839e52347bdSJani Nikula i = IGNORE_DEVICE (don't bind to this 4840e52347bdSJani Nikula device); 4841e52347bdSJani Nikula j = NO_REPORT_LUNS (don't use report luns 4842e52347bdSJani Nikula command, uas only); 4843e52347bdSJani Nikula l = NOT_LOCKABLE (don't try to lock and 4844e52347bdSJani Nikula unlock ejectable media); 4845e52347bdSJani Nikula m = MAX_SECTORS_64 (don't transfer more 4846e52347bdSJani Nikula than 64 sectors = 32 KB at a time); 4847e52347bdSJani Nikula n = INITIAL_READ10 (force a retry of the 4848e52347bdSJani Nikula initial READ(10) command); 4849e52347bdSJani Nikula o = CAPACITY_OK (accept the capacity 4850e52347bdSJani Nikula reported by the device); 4851e52347bdSJani Nikula p = WRITE_CACHE (the device cache is ON 4852e52347bdSJani Nikula by default); 4853e52347bdSJani Nikula r = IGNORE_RESIDUE (the device reports 4854e52347bdSJani Nikula bogus residue values); 4855e52347bdSJani Nikula s = SINGLE_LUN (the device has only one 4856e52347bdSJani Nikula Logical Unit); 4857e52347bdSJani Nikula t = NO_ATA_1X (don't allow ATA(12) and ATA(16) 4858e52347bdSJani Nikula commands, uas only); 4859e52347bdSJani Nikula u = IGNORE_UAS (don't bind to the uas driver); 4860e52347bdSJani Nikula w = NO_WP_DETECT (don't test whether the 4861e52347bdSJani Nikula medium is write-protected). 4862e52347bdSJani Nikula y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE 4863e52347bdSJani Nikula even if the device claims no cache) 4864e52347bdSJani Nikula Example: quirks=0419:aaf5:rl,0421:0433:rc 4865e52347bdSJani Nikula 4866e52347bdSJani Nikula user_debug= [KNL,ARM] 4867e52347bdSJani Nikula Format: <int> 4868e52347bdSJani Nikula See arch/arm/Kconfig.debug help text. 4869e52347bdSJani Nikula 1 - undefined instruction events 4870e52347bdSJani Nikula 2 - system calls 4871e52347bdSJani Nikula 4 - invalid data aborts 4872e52347bdSJani Nikula 8 - SIGSEGV faults 4873e52347bdSJani Nikula 16 - SIGBUS faults 4874e52347bdSJani Nikula Example: user_debug=31 4875e52347bdSJani Nikula 4876e52347bdSJani Nikula userpte= 4877e52347bdSJani Nikula [X86] Flags controlling user PTE allocations. 4878e52347bdSJani Nikula 4879e52347bdSJani Nikula nohigh = do not allocate PTE pages in 4880e52347bdSJani Nikula HIGHMEM regardless of setting 4881e52347bdSJani Nikula of CONFIG_HIGHPTE. 4882e52347bdSJani Nikula 4883e52347bdSJani Nikula vdso= [X86,SH] 4884e52347bdSJani Nikula On X86_32, this is an alias for vdso32=. Otherwise: 4885e52347bdSJani Nikula 4886e52347bdSJani Nikula vdso=1: enable VDSO (the default) 4887e52347bdSJani Nikula vdso=0: disable VDSO mapping 4888e52347bdSJani Nikula 4889e52347bdSJani Nikula vdso32= [X86] Control the 32-bit vDSO 4890e52347bdSJani Nikula vdso32=1: enable 32-bit VDSO 4891e52347bdSJani Nikula vdso32=0 or vdso32=2: disable 32-bit VDSO 4892e52347bdSJani Nikula 4893e52347bdSJani Nikula See the help text for CONFIG_COMPAT_VDSO for more 4894e52347bdSJani Nikula details. If CONFIG_COMPAT_VDSO is set, the default is 4895e52347bdSJani Nikula vdso32=0; otherwise, the default is vdso32=1. 4896e52347bdSJani Nikula 4897e52347bdSJani Nikula For compatibility with older kernels, vdso32=2 is an 4898e52347bdSJani Nikula alias for vdso32=0. 4899e52347bdSJani Nikula 4900e52347bdSJani Nikula Try vdso32=0 if you encounter an error that says: 4901e52347bdSJani Nikula dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! 4902e52347bdSJani Nikula 4903e52347bdSJani Nikula vector= [IA-64,SMP] 4904e52347bdSJani Nikula vector=percpu: enable percpu vector domain 4905e52347bdSJani Nikula 4906e52347bdSJani Nikula video= [FB] Frame buffer configuration 4907e52347bdSJani Nikula See Documentation/fb/modedb.txt. 4908e52347bdSJani Nikula 4909e52347bdSJani Nikula video.brightness_switch_enabled= [0,1] 4910e52347bdSJani Nikula If set to 1, on receiving an ACPI notify event 4911e52347bdSJani Nikula generated by hotkey, video driver will adjust brightness 4912e52347bdSJani Nikula level and then send out the event to user space through 4913e52347bdSJani Nikula the allocated input device; If set to 0, video driver 4914e52347bdSJani Nikula will only send out the event without touching backlight 4915e52347bdSJani Nikula brightness level. 4916e52347bdSJani Nikula default: 1 4917e52347bdSJani Nikula 4918e52347bdSJani Nikula virtio_mmio.device= 4919e52347bdSJani Nikula [VMMIO] Memory mapped virtio (platform) device. 4920e52347bdSJani Nikula 4921e52347bdSJani Nikula <size>@<baseaddr>:<irq>[:<id>] 4922e52347bdSJani Nikula where: 4923e52347bdSJani Nikula <size> := size (can use standard suffixes 4924e52347bdSJani Nikula like K, M and G) 4925e52347bdSJani Nikula <baseaddr> := physical base address 4926e52347bdSJani Nikula <irq> := interrupt number (as passed to 4927e52347bdSJani Nikula request_irq()) 4928e52347bdSJani Nikula <id> := (optional) platform device id 4929e52347bdSJani Nikula example: 4930e52347bdSJani Nikula virtio_mmio.device=1K@0x100b0000:48:7 4931e52347bdSJani Nikula 4932e52347bdSJani Nikula Can be used multiple times for multiple devices. 4933e52347bdSJani Nikula 4934e52347bdSJani Nikula vga= [BOOT,X86-32] Select a particular video mode 4935e52347bdSJani Nikula See Documentation/x86/boot.txt and 4936e52347bdSJani Nikula Documentation/svga.txt. 4937e52347bdSJani Nikula Use vga=ask for menu. 4938e52347bdSJani Nikula This is actually a boot loader parameter; the value is 4939e52347bdSJani Nikula passed to the kernel using a special protocol. 4940e52347bdSJani Nikula 4941f682a97aSAlexander Duyck vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y. 4942f682a97aSAlexander Duyck May slow down system boot speed, especially when 4943f682a97aSAlexander Duyck enabled on systems with a large amount of memory. 4944f682a97aSAlexander Duyck All options are enabled by default, and this 4945f682a97aSAlexander Duyck interface is meant to allow for selectively 4946f682a97aSAlexander Duyck enabling or disabling specific virtual memory 4947f682a97aSAlexander Duyck debugging features. 4948f682a97aSAlexander Duyck 4949f682a97aSAlexander Duyck Available options are: 4950f682a97aSAlexander Duyck P Enable page structure init time poisoning 4951f682a97aSAlexander Duyck - Disable all of the above options 4952f682a97aSAlexander Duyck 4953e52347bdSJani Nikula vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 4954e52347bdSJani Nikula size of <nn>. This can be used to increase the 4955e52347bdSJani Nikula minimum size (128MB on x86). It can also be used to 4956e52347bdSJani Nikula decrease the size and leave more room for directly 4957e52347bdSJani Nikula mapped kernel RAM. 4958e52347bdSJani Nikula 49593f429842SHeiko Carstens vmcp_cma=nn[MG] [KNL,S390] 49603f429842SHeiko Carstens Sets the memory size reserved for contiguous memory 49613f429842SHeiko Carstens allocations for the vmcp device driver. 49623f429842SHeiko Carstens 4963e52347bdSJani Nikula vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 4964e52347bdSJani Nikula Format: <command> 4965e52347bdSJani Nikula 4966e52347bdSJani Nikula vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 4967e52347bdSJani Nikula Format: <command> 4968e52347bdSJani Nikula 4969e52347bdSJani Nikula vmpoff= [KNL,S390] Perform z/VM CP command after power off. 4970e52347bdSJani Nikula Format: <command> 4971e52347bdSJani Nikula 4972e52347bdSJani Nikula vsyscall= [X86-64] 4973e52347bdSJani Nikula Controls the behavior of vsyscalls (i.e. calls to 4974e52347bdSJani Nikula fixed addresses of 0xffffffffff600x00 from legacy 4975e52347bdSJani Nikula code). Most statically-linked binaries and older 4976e52347bdSJani Nikula versions of glibc use these calls. Because these 4977e52347bdSJani Nikula functions are at fixed addresses, they make nice 4978e52347bdSJani Nikula targets for exploits that can control RIP. 4979e52347bdSJani Nikula 4980e52347bdSJani Nikula emulate [default] Vsyscalls turn into traps and are 4981e52347bdSJani Nikula emulated reasonably safely. 4982e52347bdSJani Nikula 4983e52347bdSJani Nikula native Vsyscalls are native syscall instructions. 4984e52347bdSJani Nikula This is a little bit faster than trapping 4985e52347bdSJani Nikula and makes a few dynamic recompilers work 4986e52347bdSJani Nikula better than they would in emulation mode. 4987e52347bdSJani Nikula It also makes exploits much easier to write. 4988e52347bdSJani Nikula 4989e52347bdSJani Nikula none Vsyscalls don't work at all. This makes 4990e52347bdSJani Nikula them quite hard to use for exploits but 4991e52347bdSJani Nikula might break your system. 4992e52347bdSJani Nikula 4993e52347bdSJani Nikula vt.color= [VT] Default text color. 4994e52347bdSJani Nikula Format: 0xYX, X = foreground, Y = background. 4995e52347bdSJani Nikula Default: 0x07 = light gray on black. 4996e52347bdSJani Nikula 4997e52347bdSJani Nikula vt.cur_default= [VT] Default cursor shape. 4998e52347bdSJani Nikula Format: 0xCCBBAA, where AA, BB, and CC are the same as 4999e52347bdSJani Nikula the parameters of the <Esc>[?A;B;Cc escape sequence; 5000e52347bdSJani Nikula see VGA-softcursor.txt. Default: 2 = underline. 5001e52347bdSJani Nikula 5002e52347bdSJani Nikula vt.default_blu= [VT] 5003e52347bdSJani Nikula Format: <blue0>,<blue1>,<blue2>,...,<blue15> 5004e52347bdSJani Nikula Change the default blue palette of the console. 5005e52347bdSJani Nikula This is a 16-member array composed of values 5006e52347bdSJani Nikula ranging from 0-255. 5007e52347bdSJani Nikula 5008e52347bdSJani Nikula vt.default_grn= [VT] 5009e52347bdSJani Nikula Format: <green0>,<green1>,<green2>,...,<green15> 5010e52347bdSJani Nikula Change the default green palette of the console. 5011e52347bdSJani Nikula This is a 16-member array composed of values 5012e52347bdSJani Nikula ranging from 0-255. 5013e52347bdSJani Nikula 5014e52347bdSJani Nikula vt.default_red= [VT] 5015e52347bdSJani Nikula Format: <red0>,<red1>,<red2>,...,<red15> 5016e52347bdSJani Nikula Change the default red palette of the console. 5017e52347bdSJani Nikula This is a 16-member array composed of values 5018e52347bdSJani Nikula ranging from 0-255. 5019e52347bdSJani Nikula 5020e52347bdSJani Nikula vt.default_utf8= 5021e52347bdSJani Nikula [VT] 5022e52347bdSJani Nikula Format=<0|1> 5023e52347bdSJani Nikula Set system-wide default UTF-8 mode for all tty's. 5024e52347bdSJani Nikula Default is 1, i.e. UTF-8 mode is enabled for all 5025e52347bdSJani Nikula newly opened terminals. 5026e52347bdSJani Nikula 5027e52347bdSJani Nikula vt.global_cursor_default= 5028e52347bdSJani Nikula [VT] 5029e52347bdSJani Nikula Format=<-1|0|1> 5030e52347bdSJani Nikula Set system-wide default for whether a cursor 5031e52347bdSJani Nikula is shown on new VTs. Default is -1, 5032e52347bdSJani Nikula i.e. cursors will be created by default unless 5033e52347bdSJani Nikula overridden by individual drivers. 0 will hide 5034e52347bdSJani Nikula cursors, 1 will display them. 5035e52347bdSJani Nikula 5036e52347bdSJani Nikula vt.italic= [VT] Default color for italic text; 0-15. 5037e52347bdSJani Nikula Default: 2 = green. 5038e52347bdSJani Nikula 5039e52347bdSJani Nikula vt.underline= [VT] Default color for underlined text; 0-15. 5040e52347bdSJani Nikula Default: 3 = cyan. 5041e52347bdSJani Nikula 5042e52347bdSJani Nikula watchdog timers [HW,WDT] For information on watchdog timers, 5043e52347bdSJani Nikula see Documentation/watchdog/watchdog-parameters.txt 5044e52347bdSJani Nikula or other driver-specific files in the 5045e52347bdSJani Nikula Documentation/watchdog/ directory. 5046e52347bdSJani Nikula 5047e52347bdSJani Nikula workqueue.watchdog_thresh= 5048e52347bdSJani Nikula If CONFIG_WQ_WATCHDOG is configured, workqueue can 5049e52347bdSJani Nikula warn stall conditions and dump internal state to 5050e52347bdSJani Nikula help debugging. 0 disables workqueue stall 5051e52347bdSJani Nikula detection; otherwise, it's the stall threshold 5052e52347bdSJani Nikula duration in seconds. The default value is 30 and 5053e52347bdSJani Nikula it can be updated at runtime by writing to the 5054e52347bdSJani Nikula corresponding sysfs file. 5055e52347bdSJani Nikula 5056e52347bdSJani Nikula workqueue.disable_numa 5057e52347bdSJani Nikula By default, all work items queued to unbound 5058e52347bdSJani Nikula workqueues are affine to the NUMA nodes they're 5059e52347bdSJani Nikula issued on, which results in better behavior in 5060e52347bdSJani Nikula general. If NUMA affinity needs to be disabled for 5061e52347bdSJani Nikula whatever reason, this option can be used. Note 5062e52347bdSJani Nikula that this also can be controlled per-workqueue for 5063e52347bdSJani Nikula workqueues visible under /sys/bus/workqueue/. 5064e52347bdSJani Nikula 5065e52347bdSJani Nikula workqueue.power_efficient 5066e52347bdSJani Nikula Per-cpu workqueues are generally preferred because 5067e52347bdSJani Nikula they show better performance thanks to cache 5068e52347bdSJani Nikula locality; unfortunately, per-cpu workqueues tend to 5069e52347bdSJani Nikula be more power hungry than unbound workqueues. 5070e52347bdSJani Nikula 5071e52347bdSJani Nikula Enabling this makes the per-cpu workqueues which 5072e52347bdSJani Nikula were observed to contribute significantly to power 5073e52347bdSJani Nikula consumption unbound, leading to measurably lower 5074e52347bdSJani Nikula power usage at the cost of small performance 5075e52347bdSJani Nikula overhead. 5076e52347bdSJani Nikula 5077e52347bdSJani Nikula The default value of this parameter is determined by 5078e52347bdSJani Nikula the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. 5079e52347bdSJani Nikula 5080e52347bdSJani Nikula workqueue.debug_force_rr_cpu 5081e52347bdSJani Nikula Workqueue used to implicitly guarantee that work 5082e52347bdSJani Nikula items queued without explicit CPU specified are put 5083e52347bdSJani Nikula on the local CPU. This guarantee is no longer true 5084e52347bdSJani Nikula and while local CPU is still preferred work items 5085e52347bdSJani Nikula may be put on foreign CPUs. This debug option 5086e52347bdSJani Nikula forces round-robin CPU selection to flush out 5087e52347bdSJani Nikula usages which depend on the now broken guarantee. 5088e52347bdSJani Nikula When enabled, memory and cache locality will be 5089e52347bdSJani Nikula impacted. 5090e52347bdSJani Nikula 5091e52347bdSJani Nikula x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 5092e52347bdSJani Nikula default x2apic cluster mode on platforms 5093e52347bdSJani Nikula supporting x2apic. 5094e52347bdSJani Nikula 5095e52347bdSJani Nikula x86_intel_mid_timer= [X86-32,APBT] 5096e52347bdSJani Nikula Choose timer option for x86 Intel MID platform. 5097e52347bdSJani Nikula Two valid options are apbt timer only and lapic timer 5098e52347bdSJani Nikula plus one apbt timer for broadcast timer. 5099e52347bdSJani Nikula x86_intel_mid_timer=apbt_only | lapic_and_apbt 5100e52347bdSJani Nikula 5101e52347bdSJani Nikula xen_512gb_limit [KNL,X86-64,XEN] 5102e52347bdSJani Nikula Restricts the kernel running paravirtualized under Xen 5103e52347bdSJani Nikula to use only up to 512 GB of RAM. The reason to do so is 5104e52347bdSJani Nikula crash analysis tools and Xen tools for doing domain 5105e52347bdSJani Nikula save/restore/migration must be enabled to handle larger 5106e52347bdSJani Nikula domains. 5107e52347bdSJani Nikula 5108e52347bdSJani Nikula xen_emul_unplug= [HW,X86,XEN] 5109e52347bdSJani Nikula Unplug Xen emulated devices 5110e52347bdSJani Nikula Format: [unplug0,][unplug1] 5111e52347bdSJani Nikula ide-disks -- unplug primary master IDE devices 5112e52347bdSJani Nikula aux-ide-disks -- unplug non-primary-master IDE devices 5113e52347bdSJani Nikula nics -- unplug network devices 5114e52347bdSJani Nikula all -- unplug all emulated devices (NICs and IDE disks) 5115e52347bdSJani Nikula unnecessary -- unplugging emulated devices is 5116e52347bdSJani Nikula unnecessary even if the host did not respond to 5117e52347bdSJani Nikula the unplug protocol 5118e52347bdSJani Nikula never -- do not unplug even if version check succeeds 5119e52347bdSJani Nikula 5120e52347bdSJani Nikula xen_nopvspin [X86,XEN] 5121e52347bdSJani Nikula Disables the ticketlock slowpath using Xen PV 5122e52347bdSJani Nikula optimizations. 5123e52347bdSJani Nikula 5124e52347bdSJani Nikula xen_nopv [X86] 5125e52347bdSJani Nikula Disables the PV optimizations forcing the HVM guest to 5126e52347bdSJani Nikula run as generic HVM guest with no PV drivers. 5127e52347bdSJani Nikula 5128197ecb38SMarek Marczykowski-Górecki xen_scrub_pages= [XEN] 5129197ecb38SMarek Marczykowski-Górecki Boolean option to control scrubbing pages before giving them back 5130197ecb38SMarek Marczykowski-Górecki to Xen, for use by other domains. Can be also changed at runtime 5131197ecb38SMarek Marczykowski-Górecki with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. 5132197ecb38SMarek Marczykowski-Górecki Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. 5133197ecb38SMarek Marczykowski-Górecki 5134e52347bdSJani Nikula xirc2ps_cs= [NET,PCMCIA] 5135e52347bdSJani Nikula Format: 5136e52347bdSJani Nikula <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 5137c0addc9aSLaurentiu Tudor 5138c0addc9aSLaurentiu Tudor xhci-hcd.quirks [USB,KNL] 5139c0addc9aSLaurentiu Tudor A hex value specifying bitmask with supplemental xhci 5140c0addc9aSLaurentiu Tudor host controller quirks. Meaning of each bit can be 5141c0addc9aSLaurentiu Tudor consulted in header drivers/usb/host/xhci.h. 5142