Parametry wiersza poleceń jądra-dokumentacja jądra Linux (2024)

Listy procesorów:¶

Niektóre parametry jądra przedstawiają listę procesorów jako wartość, np.Isolcpus, nohz_full, irqinficty, rcu_nocbs.Format tej listy to:

, ...,

Lub

- (musi być dodatnim zakresem w kolejności rosnącej)

lub mieszanka

, ..., -

Należy zauważyć, że w specjalnym przypadku zakresu można podzielić zakres na grupy o równych rozmiarach, a dla każdej grupy używają pewnej ilości od początku tej grupy:

-: /

Na przykład można dodać do wiersza polecenia następującego parametru:

IsolCpus = 1,2,10-20,100-2000: 2/25

gdzie końcowy element reprezentuje procesor 100 101,125,126, 150,151, ...

Wartość „N” może być użyta do reprezentowania numerycznie ostatniego procesora w systemie, tj. „FOO_CPUS = 16-N” byłby równoważny „16-31” w systemie 32.

Należy pamiętać, że „N” jest dynamiczny, więc jeśli zmiany systemu powodują zmianę szerokości bitmapu, na przykład mniej rdzeni na liście procesora, a następnie N i wszelkie zakresy za pomocą NWILL również się zmieniają.Użyj tego samego w małym 4 podstawowym systemie, a „16-N” staje się „16-3”, a teraz to samo wejście rozruchowe zostanie oznaczone jako nieprawidłowe (Start> End).

Specjalna nazwa grupy tolerancyjnej „All” ma znaczenie wyboru wszystkich procesorów, tak że „nohz_full = all” jest odpowiednikiem „nohz_full = 0-n”.

Semantyka „N” i „All” jest obsługiwana na poziomie bitmap i posiada użytkowników Bitmap_parseList ().

Ten dokument może nie być całkowicie aktualny i kompleksowy.Polecenie „modinfo -p $ {moduleName}” pokazuje bieżącą listę wszystkich parametrów loadableModule.Moduły załadowane, po załadowaniu do bieżącego jądra, alSoreVeal ich parametry w/sys/module/$ {moduleName}/parametry/.Niektóre z tych odp*rności można zmienić w czasie wykonywania przez polecenieEcho -N $ {wartość} > /sys/module/$ {moduleName}/parameters/$ {parm}.

Parametry wymienione poniżej są prawidłowe tylko wtedy, gdy włączono określoną opcję opcji kompilacji jądra i jeśli obecny jest odpowiedni sprzęt.Ta lista powinna być utrzymywana w porządku alfabetycznym.Tekst w nawiasach kwadratowych na początku każdego opisu stwierdza ograniczenia, w których obowiązują parametr:

Obsługa ACPI ACPI jest włączonaArm64 Architektura jest włączona .x25 Odpowiedni AX.25 Obsługa jest włącza.Wcześniej wbudowane w initrd.edd BIOS Unvanced Dis Drive Services (EDD) jest włączane Particing EFI Particing (GPT) jest włączony Extenved MODULEFB Urządzenie bufora ramek jest włączone. Włączanie funkcji FTRACE Włączone. GCOV GCOV Profirilin jest włączony..Hw odpowiedni sprzęt jest włączony. Hyperv obsługa Hyperv jest włączona. AIA-64 IA-64 Architektura jest włączona.Kod jest włączony. ISDN Odpowiednia obsługa ISDN jest włączona. ISOL Izolacja CPU jest włączona. Joy Odpowiednie obsługa joysticka jest włączona. Kgdb Zastępca obsługa debuggera jest włączona. Enabled Obsługa maszyny KVM.Obsługa urządzenia LOOPBACK jest włączona. Obsługa drukarki LP jest włączona. M68K M68K Architektura jest włączona.Te opcje mają bardziej szczegółowy opis w wewnętrznej stronie dokumentacji/Arch/M68K/Kernel-Options.rst.MDA MDA Obsługa konsoli jest włączona. MIPS MIPS Envaild. MOUSE WŁAŚCIWE WSPÓLNOŚCI MOILE.(Urządzenie technologii pamięci) Obsługa jest włączanaObsługa PCI PCI Express jest włączonaObsługa dysku RAM RAM jest włączona.Wiele sterowników ma swoje opcje opisane w dokumentacji/ SCSI/ sub-Directory. Włączono różne modele bezpieczeństwa. Włączono obsługę SELINUX SELINUX. Włączono obsługę szeregową..SPARC SPARC Architektura jest włączona. SYSTEM SYSTEM SYSTEM STATY ZAMYLANE są Włączone. SPRAWIEDZE SPRAWIEDZI SPORTUUNKI SPRAWIEDZI SPRAWIEDZI Włączono. Włączono sterowniki TPM.Włączone. V4L dla obsługi Linux jest włączone. VGA Konsola VGA została włączona. Dynerka MMMIO dla urządzeń wirtualnych mapowanych na pamięci jest włączona. W obsłudze wirtualnej terminali wirtualnej.Architektura jest włączona. X86-64 x86-64 jest włączona.Więcej opcji rozruchu x86-64 można znaleźć w dokumentacji/arch/x86/x86_64/boot-options.rst.x86 albo 32-bit lub 64-bit x86 (taki sam jak x86-32+x86-64) x86_UV SGI UV Obsługa UV IS ISenabled.xen Xen Obsługa jest włączona EnabledxTensa XTensa Architektura.

Ponadto następujący tekst wskazuje, że opcja:

Boot jest parametrem ładowarki rozruchowej. Bugs = odnosi się do możliwych błędów procesora na wspomnianym procesor.knl jest parametrem rozruchu jądra.

Parametry oznaczone za pomocą rozruchu są faktycznie interpretowane przez bootloader i nie mają znaczenia dla jądra bezpośrednioProtokół rozruchowy Linux/x86>.

Istnieją również parametry jądra specyficzne dla arcyOpcje rozruchu określone przez AMD64>.

Należy zauważyć, że wszystkie wymienione poniżej parametry jądra są wrażliwe na literę, a to, że trakta = na nazwie dowolnego parametru stwierdza, że ten parametr zostanie wprowadzony jako zmienna środowiskowa, podczas gdy jego brak wskazuje, że pojawi się jako argument jądra czytelny za pośrednictwem /proc /cmdlineprogramy, gdy system się stanie.

Liczba parametrów jądra nie jest ograniczona, ale długość linii poleceń kompletnych (parametry, w tym przestrzenie itp.) Jest ograniczona do ustalonej liczby znaków.Limit ten zależy od architektury i wynosi od 256 do 4096 znaków.Jest zdefiniowany w pliku ./include/uapi/asm-geneeric/setUp.h jako Command_Line_Size.

Wreszcie sufiks [KMG] jest powszechnie opisywany po wielu wartościach jądra.Te litery „K”, „M” i „G” reprezentują _binary_multipliers „Kilo”, „Mega” i „Giga”, równa się odpowiednio 2^10, 2^20 i 2^30Bytes.Takie listy sufiksów można również całkowicie pominąć:

 accept_memory= [MM] Format: { eager | lazy } default: lazy By default, unaccepted memory is accepted lazily to avoid prolonged boot times. The lazy option will add some runtime overhead until all memory is eventually accepted. In most cases the overhead is negligible. For some workloads or for debugging purposes accept_memory=eager can be used to accept all memory at once during boot. acpi= [HW,ACPI,X86,ARM64,RISCV64,EARLY] Advanced Configuration and Power Interface Format: { force | on | off | strict | noirq | rsdt | copy_dsdt } force -- enable ACPI if default was off on -- enable ACPI but allow fallback to DT [arm64,riscv64] off -- disable ACPI if default was on noirq -- do not use ACPI for IRQ routing strict -- Be less tolerant of platforms that are not strictly ACPI specification compliant. rsdt -- prefer RSDT over (default) XSDT copy_dsdt -- copy DSDT to memory For ARM64 and RISCV64, ONLY "acpi=off", "acpi=on" or "acpi=force" are available See also Documentation/power/runtime_pm.rst, pci=noacpi acpi_apic_instance= [ACPI,IOAPIC,EARLY] Format:  2: use 2nd APIC table, if available 1,0: use 1st APIC table default: 0 acpi_backlight= [HW,ACPI] { vendor | video | native | none } If set to vendor, prefer vendor-specific driver (e.g. thinkpad_acpi, sony_acpi, etc.) instead of the ACPI video.ko driver. If set to video, use the ACPI video.ko driver. If set to native, use the device's native backlight mode. If set to none, disable the ACPI backlight interface. acpi_force_32bit_fadt_addr [ACPI,EARLY] force FADT to use 32 bit addresses rather than the 64 bit X_* addresses. Some firmware have broken 64 bit addresses for force ACPI ignore these and use the older legacy 32 bit addresses. acpica_no_return_repair [HW, ACPI] Disable AML predefined validation mechanism This mechanism can repair the evaluation result to make the return objects more ACPI specification compliant. This option is useful for developers to identify the root cause of an AML interpreter issue when the issue has something to do with the repair mechanism. acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] acpi.debug_level= [HW,ACPI,ACPI_DEBUG] Format:  CONFIG_ACPI_DEBUG must be enabled to produce any ACPI debug output. Bits in debug_layer correspond to a _COMPONENT in an ACPI source file, e.g., #define _COMPONENT ACPI_EVENTS Bits in debug_level correspond to a level in ACPI_DEBUG_PRINT statements, e.g., ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... The debug_level mask defaults to "info". See Documentation/firmware-guide/acpi/debug.rst for more information about debug layers and levels. Enable processor driver info messages: acpi.debug_layer=0x20000000 Enable AML "Debug" output, i.e., stores to the Debug object while interpreting AML: acpi.debug_layer=0xffffffff acpi.debug_level=0x2 Enable all messages related to ACPI hardware: acpi.debug_layer=0x2 acpi.debug_level=0xffffffff Some values produce so much output that the system is unusable. The "log_buf_len" parameter may be useful if you need to capture more output. acpi_enforce_resources= [ACPI] { strict | lax | no } Check for resource conflicts between native drivers and ACPI OperationRegions (SystemIO and SystemMemory only). IO ports and memory declared in ACPI might be used by the ACPI subsystem in arbitrary AML code and can interfere with legacy drivers. strict (default): access to resources claimed by ACPI is denied; legacy drivers trying to access reserved resources will fail to bind to device using them. lax: access to resources claimed by ACPI is allowed; legacy drivers trying to access reserved resources will bind successfully but a warning message is logged. no: ACPI OperationRegions are not marked as reserved, no further checks are performed. acpi_force_table_verification [HW,ACPI,EARLY] Enable table checksum verification during early stage. By default, this is disabled due to x86 early mapping size limitation. acpi_irq_balance [HW,ACPI] ACPI will balance active IRQs default in APIC mode acpi_irq_nobalance [HW,ACPI] ACPI will not move active IRQs (default) default in PIC mode acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA Format: ,... acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for use by PCI Format: ,... acpi_mask_gpe= [HW,ACPI] Due to the existence of _Lxx/_Exx, some GPEs triggered by unsupported hardware/firmware features can result in GPE floodings that cannot be automatically disabled by the GPE dispatcher. This facility can be used to prevent such uncontrolled GPE floodings. Format:  or  acpi_no_auto_serialize [HW,ACPI] Disable auto-serialization of AML methods AML control methods that contain the opcodes to create named objects will be marked as "Serialized" by the auto-serialization feature. This feature is enabled by default. This option allows to turn off the feature. acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump kernels. acpi_no_static_ssdt [HW,ACPI,EARLY] Disable installation of static SSDTs at early boot time By default, SSDTs contained in the RSDT/XSDT will be installed automatically and they will appear under /sys/firmware/acpi/tables. This option turns off this feature. Note that specifying this option does not affect dynamic table installation which will install SSDT tables to /sys/firmware/acpi/tables/dynamic. acpi_no_watchdog [HW,ACPI,WDT] Ignore the ACPI-based watchdog interface (WDAT) and let a native driver control the watchdog device instead. acpi_rsdp= [ACPI,EFI,KEXEC,EARLY] Pass the RSDP address to the kernel, mostly used on machines running EFI runtime service to boot the second kernel for kdump. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS Format: To spoof as Windows 98: ="Microsoft Windows" acpi_rev_override [ACPI] Override the _REV object to return 5 (instead of 2 which is mandated by ACPI 6) as the supported ACPI specification revision (when using this switch, it may be necessary to carry out a cold reboot _twice_ in a row to make it take effect on the platform firmware). acpi_osi= [HW,ACPI] Modify list of supported OS interface strings acpi_osi="string1" # add string1 acpi_osi="!string2" # remove string2 acpi_osi=!* # remove all strings acpi_osi=! # disable all built-in OS vendor strings acpi_osi=!! # enable all built-in OS vendor strings acpi_osi= # disable all strings 'acpi_osi=!' can be used in combination with single or multiple 'acpi_osi="string1"' to support specific OS vendor string(s). Note that such command can only affect the default state of the OS vendor strings, thus it cannot affect the default state of the feature group strings and the current state of the OS vendor strings, specifying it multiple times through kernel command line is meaningless. This command is useful when one do not care about the state of the feature group strings which should be controlled by the OSPM. Examples: 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent to 'acpi_osi="Windows 2000" acpi_osi=!', they all can make '_OSI("Windows 2000")' TRUE. 'acpi_osi=' cannot be used in combination with other 'acpi_osi=' command lines, the _OSI method will not exist in the ACPI namespace. NOTE that such command can only affect the _OSI support state, thus specifying it multiple times through kernel command line is also meaningless. Examples: 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' FALSE. 'acpi_osi=!*' can be used in combination with single or multiple 'acpi_osi="string1"' to support specific string(s). Note that such command can affect the current state of both the OS vendor strings and the feature group strings, thus specifying it multiple times through kernel command line is meaningful. But it may still not able to affect the final state of a string if there are quirks related to this string. This command is useful when one want to control the state of the feature group strings to debug BIOS issues related to the OSPM features. Examples: 1. 'acpi_osi="Module Device" acpi_osi=!*' can make '_OSI("Module Device")' FALSE. 2. 'acpi_osi=!* acpi_osi="Module Device"' can make '_OSI("Module Device")' TRUE. 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is equivalent to 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' and 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', they all will make '_OSI("Windows 2000")' TRUE. acpi_pm_good [X86] Override the pmtimer bug detection: force the kernel to assume that this machine's pmtimer latches its value and always returns good values. acpi_sci= [HW,ACPI,EARLY] ACPI System Control Interrupt trigger mode Format: { level | edge | high | low } acpi_skip_timer_override [HW,ACPI,EARLY] Recognize and ignore IRQ0/pin2 Interrupt Override. For broken nForce2 BIOS resulting in XT-PIC timer. acpi_sleep= [HW,ACPI] Sleep options Format: { s3_bios, s3_mode, s3_beep, s4_hwsig, s4_nohwsig, old_ordering, nonvs, sci_force_enable, nobl } See Documentation/power/video.rst for information on s3_bios and s3_mode. s3_beep is for debugging; it makes the PC's speaker beep as soon as the kernel's real-mode entry point is called. s4_hwsig causes the kernel to check the ACPI hardware signature during resume from hibernation, and gracefully refuse to resume if it has changed. This complies with the ACPI specification but not with reality, since Windows does not do this and many laptops do change it on docking. So the default behaviour is to allow resume and simply warn when the signature changes, unless the s4_hwsig option is enabled. s4_nohwsig prevents ACPI hardware signature from being used (or even warned about) during resume. old_ordering causes the ACPI 1.0 ordering of the _PTS control method, with respect to putting devices into low power states, to be enforced (the ACPI 2.0 ordering of _PTS is used by default). nonvs prevents the kernel from saving/restoring the ACPI NVS memory during suspend/hibernation and resume. sci_force_enable causes the kernel to set SCI_EN directly on resume from S1/S3 (which is against the ACPI spec, but some broken systems don't work without it). nobl causes the internal blacklist of systems known to behave incorrectly in some ways with respect to system suspend and resume to be ignored (use wisely). acpi_use_timer_override [HW,ACPI,EARLY] Use timer override. For some broken Nvidia NF5 boards that require a timer override, but don't have HPET add_efi_memmap [EFI,X86,EARLY] Include EFI memory map in kernel's map of available physical RAM. agp= [AGP] { off | try_unsupported } off: disable AGP support try_unsupported: try to drive unsupported chipsets (may crash computer or cause data corruption) ALSA [HW,ALSA] See Documentation/sound/alsa-configuration.rst alignment= [KNL,ARM] Allow the default userspace alignment fault handler behaviour to be specified. Bit 0 enables warnings, bit 1 enables fixups, and bit 2 sends a segfault. align_va_addr= [X86-64] Align virtual addresses by clearing slice [14:12] when allocating a VMA at process creation time. This option gives you up to 3% performance improvement on AMD F15h machines (where it is enabled by default) for a CPU-intensive style benchmark, and it can vary highly in a microbenchmark depending on workload and compiler. 32: only for 32-bit processes 64: only for 64-bit processes on: enable for both 32- and 64-bit processes off: disable for both 32- and 64-bit processes alloc_snapshot [FTRACE] Allocate the ftrace snapshot buffer on boot up when the main buffer is allocated. This is handy if debugging and you need to use tracing_snapshot() on boot up, and do not want to use tracing_snapshot_alloc() as it needs to be done where GFP_KERNEL allocations are allowed. allow_mismatched_32bit_el0 [ARM64,EARLY] Allow execve() of 32-bit applications and setting of the PER_LINUX32 personality on systems where only a strict subset of the CPUs support 32-bit EL0. When this parameter is present, the set of CPUs supporting 32-bit EL0 is indicated by /sys/devices/system/cpu/aarch32_el0 and hot-unplug operations may be restricted. See Documentation/arch/arm64/asymmetric-32bit.rst for more information. amd_iommu= [HW,X86-64] Pass parameters to the AMD IOMMU driver in the system. Possible values are: fullflush - Deprecated, equivalent to iommu.strict=1 off - do not initialize any AMD IOMMU found in the system force_isolation - Force device isolation for all devices. The IOMMU driver is not allowed anymore to lift isolation requirements as needed. This option does not override iommu=pt force_enable - Force enable the IOMMU on platforms known to be buggy with IOMMU enabled. Use this option with care. pgtbl_v1 - Use v1 page table for DMA-API (Default). pgtbl_v2 - Use v2 page table for DMA-API. irtcachedis - Disable Interrupt Remapping Table (IRT) caching. amd_iommu_dump= [HW,X86-64] Enable AMD IOMMU driver option to dump the ACPI table for AMD IOMMU. With this option enabled, AMD IOMMU driver will print ACPI tables for AMD IOMMU during IOMMU initialization. amd_iommu_intr= [HW,X86-64] Specifies one of the following AMD IOMMU interrupt remapping modes: legacy - Use legacy interrupt remapping mode. vapic - Use virtual APIC mode, which allows IOMMU to inject interrupts directly into guest. This mode requires kvm-amd.avic=1. (Default when IOMMU HW support is present.) amd_pstate= [X86,EARLY] disable Do not enable amd_pstate as the default scaling driver for the supported processors passive Use amd_pstate with passive mode as a scaling driver. In this mode autonomous selection is disabled. Driver requests a desired performance level and platform tries to match the same performance level if it is satisfied by guaranteed performance level. active Use amd_pstate_epp driver instance as the scaling driver, driver provides a hint to the hardware if software wants to bias toward performance (0x0) or energy efficiency (0xff) to the CPPC firmware. then CPPC power algorithm will calculate the runtime workload and adjust the realtime cores frequency. guided Activate guided autonomous mode. Driver requests minimum and maximum performance level and the platform autonomously selects a performance level in this range and appropriate to the current workload. amd_prefcore= [X86] disable Disable amd-pstate preferred core. amijoy.map= [HW,JOY] Amiga joystick support Map of devices attached to JOY0DAT and JOY1DAT Format: , See also Documentation/input/joydev/joystick.rst analog.map= [HW,JOY] Analog joystick and gamepad support Specifies type or capabilities of an analog joystick connected to one of 16 gameports Format: ,,.. apc= [HW,SPARC] Power management functions (SPARCstation-4/5 + deriv.) Format: noidle Disable APC CPU standby support. SPARCstation-Fox does not play well with APC CPU idle - disable it if you have APC and your system crashes randomly. apic= [APIC,X86,EARLY] Advanced Programmable Interrupt Controller Change the output verbosity while booting Format: { quiet (default) | verbose | debug } Change the amount of debugging information output when initialising the APIC and IO-APIC components. For X86-32, this can also be used to specify an APIC driver name. Format: apic=driver_name Examples: apic=bigsmp apic_extnmi= [APIC,X86,EARLY] External NMI delivery setting Format: { bsp (default) | all | none } bsp: External NMI is delivered only to CPU 0 all: External NMIs are broadcast to all CPUs as a backup of CPU 0 none: External NMI is masked for all CPUs. This is useful so that a dump capture kernel won't be shot down by NMI autoconf= [IPV6] See Documentation/networking/ipv6.rst. apm= [APM] Advanced Power Management See header of arch/x86/kernel/apm_32.c. apparmor= [APPARMOR] Disable or enable AppArmor at boot time Format: { "0" | "1" } See security/apparmor/Kconfig help text 0 -- disable. 1 -- enable. Default value is set via kernel config option. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards Format: ,, arm64.nobti [ARM64] Unconditionally disable Branch Target Identification support arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory Set instructions support arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension support arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication support arm64.nosme [ARM64] Unconditionally disable Scalable Matrix Extension support arm64.nosve [ARM64] Unconditionally disable Scalable Vector Extension support ataflop= [HW,M68k] atarimouse= [HW,MOUSE] Atari Mouse atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, EzKey and similar keyboards atkbd.reset= [HW] Reset keyboard during initialization atkbd.set= [HW] Select keyboard code set Format:  (2 = AT (default), 3 = PS/2) atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar keyboards atkbd.softraw= [HW] Choose between synthetic and real raw mode Format:  (0 = real, 1 = synthetic (default)) atkbd.softrepeat= [HW] Use software keyboard repeat audit= [KNL] Enable the audit sub-system Format: { "0" | "1" | "off" | "on" } 0 | off - kernel audit is disabled and can not be enabled until the next reboot unset - kernel audit is initialized but disabled and will be fully enabled by the userspace auditd. 1 | on - kernel audit is initialized and partially enabled, storing at most audit_backlog_limit messages in RAM until it is fully enabled by the userspace auditd. Default: unset audit_backlog_limit= [KNL] Set the audit queue size limit. Format:  (must be >=0) Default: 64 bau= [X86_UV] Enable the BAU on SGI UV. The default behavior is to disable the BAU (i.e. bau=0). Format: { "0" | "1" } 0 - Disable the BAU. 1 - Enable the BAU. unset - Disable the BAU. baycom_epp= [HW,AX25] Format: , baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem Format: , See header of drivers/net/hamradio/baycom_par.c. baycom_ser_fdx= [HW,AX25] BayCom Serial Port AX.25 Modem (Full Duplex Mode) Format: ,,[,] See header of drivers/net/hamradio/baycom_ser_fdx.c. baycom_ser_hdx= [HW,AX25] BayCom Serial Port AX.25 Modem (Half Duplex Mode) Format: ,, See header of drivers/net/hamradio/baycom_ser_hdx.c. bert_disable [ACPI] Disable BERT OS support on buggy BIOSes. bgrt_disable [ACPI,X86,EARLY] Disable BGRT to avoid flickering OEM logo. blkdevparts= Manual partition parsing of block device(s) for embedded devices based on command line input. See Documentation/block/cmdline-partition.rst boot_delay= [KNL,EARLY] Milliseconds to delay each printk during boot. Only works if CONFIG_BOOT_PRINTK_DELAY is enabled, and you may also have to specify "lpj=". Boot_delay values larger than 10 seconds (10000) are assumed erroneous and ignored. Format: integer bootconfig [KNL,EARLY] Extended command line options can be added to an initrd and this will cause the kernel to look for it. See Documentation/admin-guide/bootconfig.rst bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) bttv.radio= Most important insmod options are available as kernel args too. bttv.pll= See Documentation/admin-guide/media/bttv.rst bttv.tuner= bulk_remove=off [PPC] This parameter disables the use of the pSeries firmware feature for flushing multiple hpte entries at a time. c101= [NET] Moxa C101 synchronous serial card cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. Sometimes CPU hardware bugs make them report the cache size incorrectly. The kernel will attempt work arounds to fix known problems, but for some CPUs it is not possible to determine what the correct size should be. This option provides an override for these situations. carrier_timeout= [NET] Specifies amount of time (in seconds) that the kernel should wait for a network carrier. By default it waits 120 seconds. ca_keys= [KEYS] This parameter identifies a specific key(s) on the system trusted keyring to be used for certificate trust validation. format: { id: | builtin } cca= [MIPS,EARLY] Override the kernel pages' cache coherency algorithm. Accepted values range from 0 to 7 inclusive. See arch/mips/include/asm/pgtable-bits.h for platform specific values (SB1, Loongson3 and others). ccw_timeout_log [S390] See Documentation/arch/s390/common_io.rst for details. cgroup_disable= [KNL] Disable a particular controller or optional feature Format: {name of the controller(s) or feature(s) to disable} The effects of cgroup_disable=foo are: - foo isn't auto-mounted if you mount all cgroups in a single hierarchy - foo isn't visible as an individually mountable subsystem - if foo is an optional feature then the feature is disabled and corresponding cgroup files are not created {Currently only "memory" controller deal with this and cut the overhead, others just disable the usage. So only cgroup_disable=memory is actually worthy} Specifying "pressure" disables per-cgroup pressure stall information accounting feature cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1 Format: { { controller | "all" | "named" } [,{ controller | "all" | "named" }...] } Like cgroup_disable, but only applies to cgroup v1; the blacklisted controllers remain available in cgroup2. "all" blacklists all controllers and "named" disables named mounts. Specifying both "all" and "named" disables all v1 hierarchies. cgroup_favordynmods= [KNL] Enable or Disable favordynmods. Format: { "true" | "false" } Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS. cgroup.memory= [KNL] Pass options to the cgroup memory controller. Format:  nosocket -- Disable socket memory accounting. nokmem -- Disable kernel memory accounting. nobpf -- Disable BPF memory accounting. checkreqprot= [SELINUX] Set initial checkreqprot flag value. Format: { "0" | "1" } See security/selinux/Kconfig help text. 0 -- check protection applied by kernel (includes any implied execute protection). 1 -- check protection requested by application. Default value is set via a kernel config option. Value can be changed at runtime via /sys/fs/selinux/checkreqprot. Setting checkreqprot to 1 is deprecated. cio_ignore= [S390] See Documentation/arch/s390/common_io.rst for details. clearcpuid=X[,X...] [X86] Disable CPUID feature X for the kernel. See arch/x86/include/asm/cpufeatures.h for the valid bit numbers X. Note the Linux-specific bits are not necessarily stable over kernel options, but the vendor-specific ones should be. X can also be a string as appearing in the flags: line in /proc/cpuinfo which does not have the above instability issue. However, not all features have names in /proc/cpuinfo. Note that using this option will taint your kernel. Also note that user programs calling CPUID directly or using the feature without checking anything will still see it. This just prevents it from being used by the kernel or shown in /proc/cpuinfo. Also note the kernel might malfunction if you disable some critical bits. clk_ignore_unused [CLK] Prevents the clock framework from automatically gating clocks that have not been explicitly enabled by a Linux device driver but are enabled in hardware at reset or by the bootloader/firmware. Note that this does not force such clocks to be always-on nor does it reserve those clocks in any way. This parameter is useful for debug and development, but should not be needed on a platform with proper driver support. For more information, see Documentation/driver-api/clk.rst. clock= [BUGS=X86-32, HW] gettimeofday clocksource override. [Deprecated] Forces specified clocksource (if available) to be used when calculating gettimeofday(). If specified clocksource is not available, it defaults to PIT. Format: { pit | tsc | cyclone | pmtmr } clocksource= Override the default clocksource Format:  Override the default clocksource and use the clocksource with the name specified. Some clocksource names to choose from, depending on the platform: [all] jiffies (this is the base, fallback clocksource) [ACPI] acpi_pm [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, pxa_timer,timer3,32k_counter,timer0_1 [X86-32] pit,hpet,tsc; scx200_hrt on Geode; cyclone on IBM x440 [MIPS] MIPS [PARISC] cr16 [S390] tod [SH] SuperH [SPARC64] tick [X86-64] hpet,tsc clocksource.arm_arch_timer.evtstrm= [ARM,ARM64,EARLY] Format:  Enable/disable the eventstream feature of the ARM architected timer so that code using WFE-based polling loops can be debugged more effectively on production systems. clocksource.verify_n_cpus= [KNL] Limit the number of CPUs checked for clocksources marked with CLOCK_SOURCE_VERIFY_PERCPU that are marked unstable due to excessive skew. A negative value says to check all CPUs, while zero says not to check any. Values larger than nr_cpu_ids are silently truncated to nr_cpu_ids. The actual CPUs are chosen randomly, with no replacement if the same CPU is chosen twice. clocksource-wdtest.holdoff= [KNL] Set the time in seconds that the clocksource watchdog test waits before commencing its tests. Defaults to zero when built as a module and to 10 seconds when built into the kernel. cma=nn[MG]@[start[MG][-end[MG]]] [KNL,CMA,EARLY] Sets the size of kernel global memory area for contiguous memory allocations and optionally the placement constraint by the physical address range of memory allocations. A value of 0 disables CMA altogether. For more information, see kernel/dma/contiguous.c cma_pernuma=nn[MG] [KNL,CMA,EARLY] Sets the size of kernel per-numa memory area for contiguous memory allocations. A value of 0 disables per-numa CMA altogether. And If this option is not specified, the default value is 0. With per-numa CMA enabled, DMA users on node nid will first try to allocate buffer from the pernuma area which is located in node nid, if the allocation fails, they will fallback to the global default memory area. numa_cma=:nn[MG][,:nn[MG]] [KNL,CMA,EARLY] Sets the size of kernel numa memory area for contiguous memory allocations. It will reserve CMA area for the specified node. With numa CMA enabled, DMA users on node nid will first try to allocate buffer from the numa area which is located in node nid, if the allocation fails, they will fallback to the global default memory area. cmo_free_hint= [PPC] Format: { yes | no } Specify whether pages are marked as being inactive when they are freed. This is used in CMO environments to determine OS memory pressure for page stealing by a hypervisor. Default: yes coherent_pool=nn[KMG] [ARM,KNL,EARLY] Sets the size of memory pool for coherent, atomic dma allocations, by default set to 256K. com20020= [HW,NET] ARCnet - COM20020 chipset Format: [,[,[,[,[,]]]]] com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) Format: [,] com90xx= [HW,NET] ARCnet - COM90xx chipset (memory-mapped buffers) Format: [,[,]] condev= [HW,S390] console device conmode= con3215_drop= [S390,EARLY] 3215 console drop mode. Format: y|n|Y|N|1|0 When set to true, drop data on the 3215 console when the console buffer is full. In this case the operator using a 3270 terminal emulator (for example x3270) does not have to enter the clear key for the console output to advance and the kernel to continue. This leads to a much faster boot time when a 3270 terminal emulator is active. If no 3270 terminal emulator is used, this parameter has no effect. console= [KNL] Output console device and options. tty Use the virtual console device . ttyS[,options] ttyUSB0[,options] Use the specified serial port. The options are of the form "bbbbpnf", where "bbbb" is the baud rate, "p" is parity ("n", "o", or "e"), "n" is number of bits, and "f" is flow control ("r" for RTS or omit it). Default is "9600n8". See Documentation/admin-guide/serial-console.rst for more information. See Documentation/networking/netconsole.rst for an alternative. uart[8250],io,[,options] uart[8250],mmio,[,options] uart[8250],mmio16,[,options] uart[8250],mmio32,[,options] uart[8250],0x[,options] Start an early, polled-mode console on the 8250/16550 UART at the specified I/O port or MMIO address, switching to the matching ttyS device later. MMIO inter-register address stride is either 8-bit (mmio), 16-bit (mmio16), or 32-bit (mmio32). If none of [io|mmio|mmio16|mmio32],  is assumed to be equivalent to 'mmio'. 'options' are specified in the same format described for ttyS above; if unspecified, the h/w is not re-initialized. hvc Use the hypervisor console device . This is for both Xen and PowerPC hypervisors. { null | "" } Use to disable console output, i.e., to have kernel console messages discarded. This must be the only console= parameter used on the kernel command line. If the device connected to the port is not a TTY but a braille device, prepend "brl," before the device type, for instance console=brl,ttyS0 For now, only VisioBraille is supported. console_msg_format= [KNL] Change console messages format default By default we print messages on consoles in "[time stamp] text\n" format (time stamp may not be printed, depending on CONFIG_PRINTK_TIME or `printk_time' param). syslog Switch to syslog format: "<%u>[time stamp] text\n" IOW, each message will have a facility and loglevel prefix. The format is similar to one used by syslog() syscall, or to executing "dmesg -S --raw" or to reading from /proc/kmsg. consoleblank= [KNL] The console blank (screen saver) timeout in seconds. A value of 0 disables the blank timer. Defaults to 0. coredump_filter= [KNL] Change the default value for /proc//coredump_filter. See also Documentation/filesystems/proc.rst. coresight_cpu_debug.enable [ARM,ARM64] Format:  Enable/disable the CPU sampling based debugging. 0: default value, disable debugging 1: enable debugging at boot time cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver Format: ,,,[,] cpuidle.off=1 [CPU_IDLE] disable the cpuidle sub-system cpuidle.governor= [CPU_IDLE] Name of the cpuidle governor to use. cpufreq.off=1 [CPU_FREQ] disable the cpufreq sub-system cpufreq.default_governor= [CPU_FREQ] Name of the default cpufreq governor or policy to use. This governor must be registered in the kernel before the cpufreq driver probes. cpu_init_udelay=N [X86,EARLY] Delay for N microsec between assert and de-assert of APIC INIT to start processors. This delay occurs on every CPU online, such as boot, and resume from suspend. Default: 10000 cpuhp.parallel= [SMP] Enable/disable parallel bringup of secondary CPUs Format:  Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise the parameter has no effect. crash_kexec_post_notifiers Run kdump after running panic-notifiers and dumping kmsg. This only for the users who doubt kdump always succeeds in any situation. Note that this also increases risks of kdump failure, because some panic notifiers can make the crashed kernel more unstable. crashkernel=size[KMG][@offset[KMG]] [KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel' upon panic. This parameter reserves the physical memory region [offset, offset + size] for that kernel image. If '@offset' is omitted, then a suitable offset is selected automatically. [KNL, X86-64, ARM64, RISCV, LoongArch] Select a region under 4G first, and fall back to reserve region above 4G when '@offset' hasn't been specified. See Documentation/admin-guide/kdump/kdump.rst for further details. crashkernel=range1:size1[,range2:size2,...][@offset] [KNL] Same as above, but depends on the memory in the running system. The syntax of range is start-[end] where start and end are both a memory unit (amount[KMG]). See also Documentation/admin-guide/kdump/kdump.rst for an example. crashkernel=size[KMG],high [KNL, X86-64, ARM64, RISCV, LoongArch] range could be above 4G. Allow kernel to allocate physical memory region from top, so could be above 4G if system have more than 4G ram installed. Otherwise memory region will be allocated below 4G, if available. It will be ignored if crashkernel=X is specified. crashkernel=size[KMG],low [KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G. When crashkernel=X,high is passed, kernel could allocate physical memory region above 4G, that cause second kernel crash on system that require some amount of low memory, e.g. swiotlb requires at least 64M+32K low memory, also enough extra low memory is needed to make sure DMA buffers for 32-bit devices won't run out. Kernel would try to allocate default size of memory below 4G automatically. The default size is platform dependent. --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB) --> arm64: 128MiB --> riscv: 128MiB --> loongarch: 128MiB This one lets the user specify own low range under 4G for second kernel instead. 0: to disable low allocation. It will be ignored when crashkernel=X,high is not used or memory reserved is below 4G. cryptomgr.notests [KNL] Disable crypto self-tests cs89x0_dma= [HW,NET] Format:  cs89x0_media= [HW,NET] Format: { rj45 | aui | bnc } csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU function call handling. When switched on, additional debug data is printed to the console in case a hanging CPU is detected, and that CPU is pinged again in order to try to resolve the hang situation. The default value of this option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT Kconfig option. dasd= [HW,NET] See header of drivers/s390/block/dasd_devmap.c. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port (one device per port) Format: , See also Documentation/input/devices/joystick-parport.rst debug [KNL,EARLY] Enable kernel debugging (events log level). debug_boot_weak_hash [KNL,EARLY] Enable printing [hashed] pointers early in the boot sequence. If enabled, we use a weak hash instead of siphash to hash pointers. Use this option if you are seeing instances of '(___ptrval___)') and need to see a value (hashed pointer) instead. Cryptographically insecure, please do not use on production kernels. debug_locks_verbose= [KNL] verbose locking self-tests Format:  Print debugging info while doing the locking API self-tests. Bitmask for the various LOCKTYPE_ tests. Defaults to 0 (no extra messages), setting it to -1 (all bits set) will print _a_lot_ more information - normally only useful to lockdep developers. debug_objects [KNL,EARLY] Enable object debugging debug_guardpage_minorder= [KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this parameter allows control of the order of pages that will be intentionally kept free (and hence protected) by the buddy allocator. Bigger value increase the probability of catching random memory corruption, but reduce the amount of memory for normal system use. The maximum possible value is MAX_PAGE_ORDER/2. Setting this parameter to 1 or 2 should be enough to identify most random memory corruption problems caused by bugs in kernel or driver code when a CPU writes to (or reads from) a random memory location. Note that there exists a class of memory corruptions problems caused by buggy H/W or F/W or by drivers badly programming DMA (basically when memory is written at bus level and the CPU MMU is bypassed) which are not detectable by CONFIG_DEBUG_PAGEALLOC, hence this option will not help tracking down these problems. debug_pagealloc= [KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this parameter enables the feature at boot time. By default, it is disabled and the system will work mostly the same as a kernel built without CONFIG_DEBUG_PAGEALLOC. Note: to get most of debug_pagealloc error reports, it's useful to also enable the page_owner functionality. on: enable the feature debugfs= [KNL,EARLY] This parameter enables what is exposed to userspace and debugfs internal clients. Format: { on, no-mount, off } on: All functions are enabled. no-mount: Filesystem is not registered but kernel clients can access APIs and a crashkernel can be used to read its content. There is nothing to mount. off: Filesystem is not registered and clients get a -EPERM as result when trying to register files or directories within debugfs. This is equivalent of the runtime functionality if debugfs was not enabled in the kernel at all. Default value is set in build-time with a kernel configuration. debugpat [X86] Enable PAT debugging default_hugepagesz= [HW] The size of the default HugeTLB page. This is the size represented by the legacy /proc/ hugepages APIs. In addition, this is the default hugetlb size used for shmget(), mmap() and mounting hugetlbfs filesystems. If not specified, defaults to the architecture's default huge page size. Huge page sizes are architecture dependent. See also Documentation/admin-guide/mm/hugetlbpage.rst. Format: size[KMG] deferred_probe_timeout= [KNL] Debugging option to set a timeout in seconds for deferred probe to give up waiting on dependencies to probe. Only specific dependencies (subsystems or drivers) that have opted in will be ignored. A timeout of 0 will timeout at the end of initcalls. If the time out hasn't expired, it'll be restarted by each successful driver registration. This option will also dump out devices still on the deferred probe list after retrying. delayacct [KNL] Enable per-task delay accounting dell_smm_hwmon.ignore_dmi= [HW] Continue probing hardware even if DMI data indicates that the driver is running on unsupported hardware. dell_smm_hwmon.force= [HW] Activate driver even if SMM BIOS signature does not match list of supported models and enable otherwise blacklisted features. dell_smm_hwmon.power_status= [HW] Report power status in /proc/i8k (disabled by default). dell_smm_hwmon.restricted= [HW] Allow controlling fans only if SYS_ADMIN capability is set. dell_smm_hwmon.fan_mult= [HW] Factor to multiply fan speed with. dell_smm_hwmon.fan_max= [HW] Maximum configurable fan speed. dfltcc= [HW,S390] Format: { on | off | def_only | inf_only | always } on: s390 zlib hardware support for compression on level 1 and decompression (default) off: No s390 zlib hardware support def_only: s390 zlib hardware support for deflate only (compression on level 1) inf_only: s390 zlib hardware support for inflate only (decompression) always: Same as 'on' but ignores the selected compression level always using hardware support (used for debugging) dhash_entries= [KNL] Set number of hash buckets for dentry cache. disable_1tb_segments [PPC,EARLY] Disables the use of 1TB hash page table segments. This causes the kernel to fall back to 256MB segments which can be useful when debugging issues that require an SLB miss to occur. disable= [IPV6] See Documentation/networking/ipv6.rst. disable_radix [PPC,EARLY] Disable RADIX MMU mode on POWER9 disable_tlbie [PPC] Disable TLBIE instruction. Currently does not work with KVM, with HASH MMU, or with coherent accelerators. disable_ddw [PPC/PSERIES,EARLY] Disable Dynamic DMA Window support. Use this to workaround buggy firmware. disable_ipv6= [IPV6] See Documentation/networking/ipv6.rst. disable_mtrr_cleanup [X86,EARLY] The kernel tries to adjust MTRR layout from continuous to discrete, to make X server driver able to add WB entry later. This parameter disables that. disable_mtrr_trim [X86, Intel and AMD only,EARLY] By default the kernel will trim any uncacheable memory out of your available memory pool based on MTRR settings. This parameter disables that behavior, possibly causing your machine to run very slowly. disable_timer_pin_1 [X86,EARLY] Disable PIN 1 of APIC timer Can be useful to work around chipset bugs. dis_ucode_ldr [X86] Disable the microcode loader. dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, this option disables the debugging code at boot. dma_debug_entries= This option allows to tune the number of preallocated entries for DMA-API debugging code. One entry is required per DMA-API allocation. Use this if the DMA-API debugging code disables itself because the architectural default is too low. dma_debug_driver= With this option the DMA-API debugging driver filter feature can be enabled at boot time. Just pass the driver to filter for as the parameter. The filter can be disabled or changed to another driver later using sysfs. reg_file_data_sampling= [X86] Controls mitigation for Register File Data Sampling (RFDS) vulnerability. RFDS is a CPU vulnerability which may allow userspace to infer kernel data values previously stored in floating point registers, vector registers, or integer registers. RFDS only affects Intel Atom processors. on: Turns ON the mitigation. off: Turns OFF the mitigation. This parameter overrides the compile time default set by CONFIG_MITIGATION_RFDS. Mitigation cannot be disabled when other VERW based mitigations (like MDS) are enabled. In order to disable RFDS mitigation all VERW based mitigations need to be disabled. For details see: Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst driver_async_probe= [KNL] List of driver names to be probed asynchronously. * matches with all driver names. If * is specified, the rest of the listed driver names are those that will NOT match the *. Format: ,... drm.edid_firmware=[:][,[:]] Broken monitors, graphic adapters, KVMs and EDIDless panels may send no or incorrect EDID data sets. This parameter allows to specify an EDID data sets in the /lib/firmware directory that are used instead. An EDID data set will only be used for a particular connector, if its name and a colon are prepended to the EDID name. Each connector may use a unique EDID data set by separating the files with a comma. An EDID data set with no connector name will be used for any connectors not explicitly specified. dscc4.setup= [NET] dt_cpu_ftrs= [PPC,EARLY] Format: {"off" | "known"} Control how the dt_cpu_ftrs device-tree binding is used for CPU feature discovery and setup (if it exists). off: Do not use it, fall back to legacy cpu table. known: Do not pass through unknown features to guests or userspace, only those that the kernel is aware of. dump_apple_properties [X86] Dump name and content of EFI device properties on x86 Macs. Useful for driver authors to determine what data is available or for reverse-engineering. dyndbg[="val"] [KNL,DYNAMIC_DEBUG] .dyndbg[="val"] Enable debug messages at boot time. See Documentation/admin-guide/dynamic-debug-howto.rst for details. early_ioremap_debug [KNL,EARLY] Enable debug messages in early_ioremap support. This is useful for tracking down temporary early mappings which are not unmapped. earlycon= [KNL,EARLY] Output early console device and options. When used with no options, the early console is determined by stdout-path property in device tree's chosen node or the ACPI SPCR table if supported by the platform. cdns,[,options] Start an early, polled-mode console on a Cadence (xuartps) serial port at the specified address. Only supported option is baud rate. If baud rate is not specified, the serial port must already be setup and configured. uart[8250],io,[,options[,uartclk]] uart[8250],mmio,[,options[,uartclk]] uart[8250],mmio32,[,options[,uartclk]] uart[8250],mmio32be,[,options[,uartclk]] uart[8250],0x[,options] Start an early, polled-mode console on the 8250/16550 UART at the specified I/O port or MMIO address. MMIO inter-register address stride is either 8-bit (mmio) or 32-bit (mmio32 or mmio32be). If none of [io|mmio|mmio32|mmio32be],  is assumed to be equivalent to 'mmio'. 'options' are specified in the same format described for "console=ttyS"; if unspecified, the h/w is not initialized. 'uartclk' is the uart clock frequency; if unspecified, it is set to 'BASE_BAUD' * 16. pl011, pl011,mmio32, Start an early, polled-mode console on a pl011 serial port at the specified address. The pl011 serial port must already be setup and configured. Options are not yet supported. If 'mmio32' is specified, then only the driver will use only 32-bit accessors to read/write the device registers. liteuart, Start an early console on a litex serial port at the specified address. The serial port must already be setup and configured. Options are not yet supported. meson, Start an early, polled-mode console on a meson serial port at the specified address. The serial port must already be setup and configured. Options are not yet supported. msm_serial, Start an early, polled-mode console on an msm serial port at the specified address. The serial port must already be setup and configured. Options are not yet supported. msm_serial_dm, Start an early, polled-mode console on an msm serial dm port at the specified address. The serial port must already be setup and configured. Options are not yet supported. owl, Start an early, polled-mode console on a serial port of an Actions Semi SoC, such as S500 or S900, at the specified address. The serial port must already be setup and configured. Options are not yet supported. rda, Start an early, polled-mode console on a serial port of an RDA Micro SoC, such as RDA8810PL, at the specified address. The serial port must already be setup and configured. Options are not yet supported. sbi Use RISC-V SBI (Supervisor Binary Interface) for early console. smh Use ARM semihosting calls for early console. s3c2410, s3c2412, s3c2440, s3c6400, s5pv210, exynos4210, Use early console provided by serial driver available on Samsung SoCs, requires selecting proper type and a correct base address of the selected UART port. The serial port must already be setup and configured. Options are not yet supported. lantiq, Start an early, polled-mode console on a lantiq serial (lqasc) port at the specified address. The serial port must already be setup and configured. Options are not yet supported. lpuart, lpuart32, Use early console provided by Freescale LP UART driver found on Freescale Vybrid and QorIQ LS1021A processors. A valid base address must be provided, and the serial port must already be setup and configured. ec_imx21, ec_imx6q, Start an early, polled-mode, output-only console on the Freescale i.MX UART at the specified address. The UART must already be setup and configured. ar3700_uart, Start an early, polled-mode console on the Armada 3700 serial port at the specified address. The serial port must already be setup and configured. Options are not yet supported. qcom_geni, Start an early, polled-mode console on a Qualcomm Generic Interface (GENI) based serial port at the specified address. The serial port must already be setup and configured. Options are not yet supported. efifb,[options] Start an early, unaccelerated console on the EFI memory mapped framebuffer (if available). On cache coherent non-x86 systems that use system memory for the framebuffer, pass the 'ram' option so that it is mapped with the correct attributes. linflex, Use early console provided by Freescale LINFlexD UART serial driver for NXP S32V234 SoCs. A valid base address must be provided, and the serial port must already be setup and configured. earlyprintk= [X86,SH,ARM,M68k,S390,UM,EARLY] earlyprintk=vga earlyprintk=sclp earlyprintk=xen earlyprintk=serial[,ttySn[,baudrate]] earlyprintk=serial[,0x...[,baudrate]] earlyprintk=ttySn[,baudrate] earlyprintk=dbgp[debugController#] earlyprintk=pciserial[,force],bus:device.function[,baudrate] earlyprintk=xdbc[xhciController#] earlyprintk=bios earlyprintk is useful when the kernel crashes before the normal console is initialized. It is not enabled by default because it has some cosmetic problems. Append ",keep" to not disable it when the real console takes over. Only one of vga, serial, or usb debug port can be used at a time. Currently only ttyS0 and ttyS1 may be specified by name. Other I/O ports may be explicitly specified on some architectures (x86 and arm at least) by replacing ttySn with an I/O port address, like this: earlyprintk=serial,0x1008,115200 You can find the port for a given device in /proc/tty/driver/serial: 2: uart:ST16650V2 port:00001008 irq:18 ... Interaction with the standard serial driver is not very good. The VGA output is eventually overwritten by the real console. The xen option can only be used in Xen domains. The sclp output can only be used on s390. The bios output can only be used on SuperH. The optional "force" to "pciserial" enables use of a PCI device even when its classcode is not of the UART class. edac_report= [HW,EDAC] Control how to report EDAC event Format: {"on" | "off" | "force"} on: enable EDAC to report H/W event. May be overridden by other higher priority error reporting module. off: disable H/W event reporting through EDAC. force: enforce the use of EDAC to report H/W event. default: on. edd= [EDD] Format: {"off" | "on" | "skip[mbr]"} efi= [EFI,EARLY] Format: { "debug", "disable_early_pci_dma", "nochunk", "noruntime", "nosoftreserve", "novamap", "no_disable_early_pci_dma" } debug: enable misc debug output. disable_early_pci_dma: disable the busmaster bit on all PCI bridges while in the EFI boot stub. nochunk: disable reading files in "chunks" in the EFI boot stub, as chunking can cause problems with some firmware implementations. noruntime : disable EFI runtime services support nosoftreserve: The EFI_MEMORY_SP (Specific Purpose) attribute may cause the kernel to reserve the memory range for a memory mapping driver to claim. Specify efi=nosoftreserve to disable this reservation and treat the memory by its base type (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM"). novamap: do not call SetVirtualAddressMap(). no_disable_early_pci_dma: Leave the busmaster bit set on all PCI bridges while in the EFI boot stub efi_no_storage_paranoia [EFI,X86,EARLY] Using this parameter you can use more than 50% of your efi variable storage. Use this parameter only if you are really sure that your UEFI does sane gc and fulfills the spec otherwise your board may brick. efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI,X86,EARLY] Add arbitrary attribute to specific memory range by updating original EFI memory map. Region of memory which aa attribute is added to is from ss to ss+nn. If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) attribute is added to range 0x100000000-0x180000000 and 0x10a0000000-0x1120000000. If efi_fake_mem=8G@9G:0x40000 is specified, the EFI_MEMORY_SP(0x40000) attribute is added to range 0x240000000-0x43fffffff. Using this parameter you can do debugging of EFI memmap related features. For example, you can do debugging of Address Range Mirroring feature even if your box doesn't support it, or mark specific memory as "soft reserved". efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT that is to be dynamically loaded by Linux. If there are multiple variables with the same name but with different vendor GUIDs, all of them will be loaded. See Documentation/admin-guide/acpi/ssdt-overlays.rst for details. eisa_irq_edge= [PARISC,HW] See header of drivers/parisc/eisa.c. ekgdboc= [X86,KGDB,EARLY] Allow early kernel console debugging Format: ekgdboc=kbd This is designed to be used in conjunction with the boot argument: earlyprintk=vga This parameter works in place of the kgdboc parameter but can only be used if the backing tty is available very early in the boot process. For early debugging via a serial port see kgdboc_earlycon instead. elanfreq= [X86-32] See comment before function elanfreq_setup() in arch/x86/kernel/cpu/cpufreq/elanfreq.c. elfcorehdr=[size[KMG]@]offset[KMG] [PPC,SH,X86,S390,EARLY] Specifies physical address of start of kernel core image elf header and optionally the size. Generally kexec loader will pass this option to capture kernel. See Documentation/admin-guide/kdump/kdump.rst for details. enable_mtrr_cleanup [X86,EARLY] The kernel tries to adjust MTRR layout from continuous to discrete, to make X server driver able to add WB entry later. This parameter enables that. enable_timer_pin_1 [X86] Enable PIN 1 of APIC timer Can be useful to work around chipset bugs (in particular on some ATI chipsets). The kernel tries to set a reasonable default. enforcing= [SELINUX] Set initial enforcing status. Format: {"0" | "1"} See security/selinux/Kconfig help text. 0 -- permissive (log only, no denials). 1 -- enforcing (deny and log). Default value is 0. Value can be changed at runtime via /sys/fs/selinux/enforce. erst_disable [ACPI] Disable Error Record Serialization Table (ERST) support. ether= [HW,NET] Ethernet cards parameters This option is obsoleted by the "netdev=" option, which has equivalent usage. See its documentation for details. evm= [EVM] Format: { "fix" } Permit 'security.evm' to be updated regardless of current integrity status. early_page_ext [KNL,EARLY] Enforces page_ext initialization to earlier stages so cover more early boot allocations. Please note that as side effect some optimizations might be disabled to achieve that (e.g. parallelized memory initialization is disabled) so the boot process might take longer, especially on systems with a lot of memory. Available with CONFIG_PAGE_EXTENSION=y. failslab= fail_usercopy= fail_page_alloc= fail_make_request=[KNL] General fault injection mechanism. Format: ,,, See also Documentation/fault-injection/. fb_tunnels= [NET] Format: { initns | none } See Documentation/admin-guide/sysctl/net.rst for fb_tunnels_only_for_init_ns floppy= [HW] See Documentation/admin-guide/blockdev/floppy.rst. forcepae [X86-32] Forcefully enable Physical Address Extension (PAE). Many Pentium M systems disable PAE but may have a functionally usable PAE implementation. Warning: use of this parameter will taint the kernel and may cause unknown problems. fred= [X86-64] Enable/disable Flexible Return and Event Delivery. Format: { on | off } on: enable FRED when it's present. off: disable FRED, the default setting. ftrace=[tracer] [FTRACE] will set and start the specified tracer as early as possible in order to facilitate early boot debugging. ftrace_boot_snapshot [FTRACE] On boot up, a snapshot will be taken of the ftrace ring buffer that can be read at: /sys/kernel/tracing/snapshot. This is useful if you need tracing information from kernel boot up that is likely to be overridden by user space start up functionality. Optionally, the snapshot can also be defined for a tracing instance that was created by the trace_instance= command line parameter. trace_instance=foo,sched_switch ftrace_boot_snapshot=foo The above will cause the "foo" tracing instance to trigger a snapshot at the end of boot up. ftrace_dump_on_oops[=2(orig_cpu) | =][, | ,=2(orig_cpu)] [FTRACE] will dump the trace buffers on oops. If no parameter is passed, ftrace will dump global buffers of all CPUs, if you pass 2 or orig_cpu, it will dump only the buffer of the CPU that triggered the oops, or the specific instance will be dumped if its name is passed. Multiple instance dump is also supported, and instances are separated by commas. Each instance supports only dump on CPU that triggered the oops by passing 2 or orig_cpu to it. ftrace_dump_on_oops=foo=orig_cpu The above will dump only the buffer of "foo" instance on CPU that triggered the oops. ftrace_dump_on_oops,foo,bar=orig_cpu The above will dump global buffer on all CPUs, the buffer of "foo" instance on all CPUs and the buffer of "bar" instance on CPU that triggered the oops. ftrace_filter=[function-list] [FTRACE] Limit the functions traced by the function tracer at boot up. function-list is a comma-separated list of functions. This list can be changed at run time by the set_ftrace_filter file in the debugfs tracing directory. ftrace_notrace=[function-list] [FTRACE] Do not trace the functions specified in function-list. This list can be changed at run time by the set_ftrace_notrace file in the debugfs tracing directory. ftrace_graph_filter=[function-list] [FTRACE] Limit the top level callers functions traced by the function graph tracer at boot up. function-list is a comma-separated list of functions that can be changed at run time by the set_graph_function file in the debugfs tracing directory. ftrace_graph_notrace=[function-list] [FTRACE] Do not trace from the functions specified in function-list. This list is a comma-separated list of functions that can be changed at run time by the set_graph_notrace file in the debugfs tracing directory. ftrace_graph_max_depth= [FTRACE] Used with the function graph tracer. This is the max depth it will trace into a function. This value can be changed at run time by the max_graph_depth file in the tracefs tracing directory. default: 0 (no limit) fw_devlink= [KNL,EARLY] Create device links between consumer and supplier devices by scanning the firmware to infer the consumer/supplier relationships. This feature is especially useful when drivers are loaded as modules as it ensures proper ordering of tasks like device probing (suppliers first, then consumers), supplier boot state clean up (only after all consumers have probed), suspend/resume & runtime PM (consumers first, then suppliers). Format: { off | permissive | on | rpm } off -- Don't create device links from firmware info. permissive -- Create device links from firmware info but use it only for ordering boot state clean up (sync_state() calls). on -- Create device links from firmware info and use it to enforce probe and suspend/resume ordering. rpm -- Like "on", but also use to order runtime PM. fw_devlink.strict= [KNL,EARLY] Treat all inferred dependencies as mandatory dependencies. This only applies for fw_devlink=on|rpm. Format:  fw_devlink.sync_state = [KNL,EARLY] When all devices that could probe have finished probing, this parameter controls what to do with devices that haven't yet received their sync_state() calls. Format: { strict | timeout } strict -- Default. Continue waiting on consumers to probe successfully. timeout -- Give up waiting on consumers and call sync_state() on any devices that haven't yet received their sync_state() calls after deferred_probe_timeout has expired or by late_initcall() if !CONFIG_MODULES. gamecon.map[2|3]= [HW,JOY] Multisystem joystick and NES/SNES/PSX pad support via parallel port (up to 5 devices per port) Format: ,,,,, See also Documentation/input/devices/joystick-parport.rst gamma= [HW,DRM] gart_fix_e820= [X86-64,EARLY] disable the fix e820 for K8 GART Format: off | on default: on gather_data_sampling= [X86,INTEL,EARLY] Control the Gather Data Sampling (GDS) mitigation. Gather Data Sampling is a hardware vulnerability which allows unprivileged speculative access to data which was previously stored in vector registers. This issue is mitigated by default in updated microcode. The mitigation may have a performance impact but can be disabled. On systems without the microcode mitigation disabling AVX serves as a mitigation. force: Disable AVX to mitigate systems without microcode mitigation. No effect if the microcode mitigation is present. Known to cause crashes in userspace with buggy AVX enumeration. off: Disable GDS mitigation. gcov_persist= [GCOV] When non-zero (default), profiling data for kernel modules is saved and remains accessible via debugfs, even when the module is unloaded/reloaded. When zero, profiling data is discarded and associated debugfs files are removed at module unload time. goldfish [X86] Enable the goldfish android emulator platform. Don't use this when you are not running on the android emulator gpio-mockup.gpio_mockup_ranges [HW] Sets the ranges of gpiochip of for this device. Format: ,,,... gpio-mockup.gpio_mockup_named_lines [HW] Let the driver know GPIO lines should be named. gpt [EFI] Forces disk with valid GPT signature but invalid Protective MBR to be treated as GPT. If the primary GPT is corrupted, it enables the backup/alternate GPT to be used instead. grcan.enable0= [HW] Configuration of physical interface 0. Determines the "Enable 0" bit of the configuration register. Format: 0 | 1 Default: 0 grcan.enable1= [HW] Configuration of physical interface 1. Determines the "Enable 0" bit of the configuration register. Format: 0 | 1 Default: 0 grcan.select= [HW] Select which physical interface to use. Format: 0 | 1 Default: 0 grcan.txsize= [HW] Sets the size of the tx buffer. Format:  such that (txsize & ~0x1fffc0) == 0. Default: 1024 grcan.rxsize= [HW] Sets the size of the rx buffer. Format:  such that (rxsize & ~0x1fffc0) == 0. Default: 1024 hardened_usercopy= [KNL] Under CONFIG_HARDENED_USERCOPY, whether hardening is enabled for this boot. Hardened usercopy checking is used to protect the kernel from reading or writing beyond known memory allocation boundaries as a proactive defense against bounds-checking flaws in the kernel's copy_to_user()/copy_from_user() interface. on Perform hardened usercopy checks (default). off Disable hardened usercopy checks. hardlockup_all_cpu_backtrace= [KNL] Should the hard-lockup detector generate backtraces on all cpus. Format: 0 | 1 hashdist= [KNL,NUMA] Large hashes allocated during boot are distributed across NUMA nodes. Defaults on for 64-bit NUMA, off otherwise. Format: 0 | 1 (for off | on) hcl= [IA-64] SGI's Hardware Graph compatibility layer hd= [EIDE] (E)IDE hard drive subsystem geometry Format: ,, hest_disable [ACPI] Disable Hardware Error Source Table (HEST) support; corresponding firmware-first mode error processing logic will be disabled. hibernate= [HIBERNATION] noresume Don't check if there's a hibernation image present during boot. nocompress Don't compress/decompress hibernation images. no Disable hibernation and resume. protect_image Turn on image protection during restoration (that will set all pages holding image data during restoration read-only). hibernate.compressor= [HIBERNATION] Compression algorithm to be used with hibernation. Format: { lzo | lz4 } Default: lzo lzo: Select LZO compression algorithm to compress/decompress hibernation image. lz4: Select LZ4 compression algorithm to compress/decompress hibernation image. highmem=nn[KMG] [KNL,BOOT,EARLY] forces the highmem zone to have an exact size of . This works even on boxes that have no highmem otherwise. This also works to reduce highmem size on bigger boxes. highres= [KNL] Enable/disable high resolution timer mode. Valid parameters: "on", "off" Default: "on" hlt [BUGS=ARM,SH] hostname= [KNL,EARLY] Set the hostname (aka UTS nodename). Format:  This allows setting the system's hostname during early startup. This sets the name returned by gethostname. Using this parameter to set the hostname makes it possible to ensure the hostname is correctly set before any userspace processes run, avoiding the possibility that a process may call gethostname before the hostname has been explicitly set, resulting in the calling process getting an incorrect result. The string must not exceed the maximum allowed hostname length (usually 64 characters) and will be truncated otherwise. hpet= [X86-32,HPET] option to control HPET usage Format: { enable (default) | disable | force | verbose } disable: disable HPET and use PIT instead force: allow force enabled of undocumented chips (ICH4, VIA, nVidia) verbose: show contents of HPET registers during setup hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET registers. Default set by CONFIG_HPET_MMAP_DEFAULT. hugepages= [HW] Number of HugeTLB pages to allocate at boot. If this follows hugepagesz (below), it specifies the number of pages of hugepagesz to be allocated. If this is the first HugeTLB parameter on the command line, it specifies the number of pages to allocate for the default huge page size. If using node format, the number of pages to allocate per-node can be specified. See also Documentation/admin-guide/mm/hugetlbpage.rst. Format:  or (node format) :[,:] hugepagesz= [HW] The size of the HugeTLB pages. This is used in conjunction with hugepages (above) to allocate huge pages of a specific size at boot. The pair hugepagesz=X hugepages=Y can be specified once for each supported huge page size. Huge page sizes are architecture dependent. See also Documentation/admin-guide/mm/hugetlbpage.rst. Format: size[KMG] hugetlb_cma= [HW,CMA,EARLY] The size of a CMA area used for allocation of gigantic hugepages. Or using node format, the size of a CMA area per node can be specified. Format: nn[KMGTPE] or (node format) :nn[KMGTPE][,:nn[KMGTPE]] Reserve a CMA area of given size and allocate gigantic hugepages using the CMA allocator. If enabled, the boot-time allocation of gigantic hugepages is skipped. hugetlb_free_vmemmap= [KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP enabled. Control if HugeTLB Vmemmap Optimization (HVO) is enabled. Allows heavy hugetlb users to free up some more memory (7 * PAGE_SIZE for each 2MB hugetlb page). Format: { on | off (default) } on: enable HVO off: disable HVO Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y, the default is on. Note that the vmemmap pages may be allocated from the added memory block itself when memory_hotplug.memmap_on_memory is enabled, those vmemmap pages cannot be optimized even if this feature is enabled. Other vmemmap pages not allocated from the added memory block itself do not be affected. hung_task_panic= [KNL] Should the hung task detector generate panics. Format: 0 | 1 A value of 1 instructs the kernel to panic when a hung task is detected. The default value is controlled by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time option. The value selected by this boot parameter can be changed later by the kernel.hung_task_panic sysctl. hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) terminal devices. Valid values: 0..8 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. If specified, z/VM IUCV HVC accepts connections from listed z/VM user IDs only. hv_nopvspin [X86,HYPER_V,EARLY] Disables the paravirt spinlock optimizations which allow the hypervisor to 'idle' the guest on lock contention. i2c_bus= [HW] Override the default board specific I2C bus speed or register an additional I2C bus that is not registered from board initialization code. Format: , i8042.debug [HW] Toggle i8042 debug mode i8042.unmask_kbd_data [HW] Enable printing of interrupt data from the KBD port (disabled by default, and as a pre-condition requires that i8042.debug=1 be enabled) i8042.direct [HW] Put keyboard port into non-translated mode i8042.dumbkbd [HW] Pretend that controller can only read data from keyboard and cannot control its state (Don't attempt to blink the leds) i8042.noaux [HW] Don't check for auxiliary (== mouse) port i8042.nokbd [HW] Don't check/create keyboard port i8042.noloop [HW] Disable the AUX Loopback command while probing for the AUX port i8042.nomux [HW] Don't check presence of an active multiplexing controller i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX controllers i8042.notimeout [HW] Ignore timeout condition signalled by controller i8042.reset [HW] Reset the controller during init, cleanup and suspend-to-ram transitions, only during s2r transitions, or never reset Format: { 1 | Y | y | 0 | N | n } 1, Y, y: always reset controller 0, N, n: don't ever reset controller Default: only on s2r transitions on x86; most other architectures force reset to be always executed i8042.unlock [HW] Unlock (ignore) the keylock i8042.kbdreset [HW] Reset device connected to KBD port i8042.probe_defer [HW] Allow deferred probing upon i8042 probe errors i810= [HW,DRM] i915.invert_brightness= [DRM] Invert the sense of the variable that is used to set the brightness of the panel backlight. Normally a brightness value of 0 indicates backlight switched off, and the maximum of the brightness value sets the backlight to maximum brightness. If this parameter is set to 0 (default) and the machine requires it, or this parameter is set to 1, a brightness value of 0 sets the backlight to maximum brightness, and the maximum of the brightness value switches the backlight off. -1 -- never invert brightness 0 -- machine default 1 -- force brightness inversion ia32_emulation= [X86-64] Format:  When true, allows loading 32-bit programs and executing 32-bit syscalls, essentially overriding IA32_EMULATION_DEFAULT_DISABLED at boot time. When false, unconditionally disables IA32 emulation. icn= [HW,ISDN] Format: [,[,[,]]] idle= [X86,EARLY] Format: idle=poll, idle=halt, idle=nomwait Poll forces a polling idle loop that can slightly improve the performance of waking up a idle CPU, but will use a lot of power and make the system run hot. Not recommended. idle=halt: Halt is forced to be used for CPU idle. In such case C2/C3 won't be used again. idle=nomwait: Disable mwait for CPU C-states idxd.sva= [HW] Format:  Allow force disabling of Shared Virtual Memory (SVA) support for the idxd driver. By default it is set to true (1). idxd.tc_override= [HW] Format:  Allow override of default traffic class configuration for the device. By default it is set to false (0). ieee754= [MIPS] Select IEEE Std 754 conformance mode Format: { strict | legacy | 2008 | relaxed } Default: strict Choose which programs will be accepted for execution based on the IEEE 754 NaN encoding(s) supported by the FPU and the NaN encoding requested with the value of an ELF file header flag individually set by each binary. Hardware implementations are permitted to support either or both of the legacy and the 2008 NaN encoding mode. Available settings are as follows: strict accept binaries that request a NaN encoding supported by the FPU legacy only accept legacy-NaN binaries, if supported by the FPU 2008 only accept 2008-NaN binaries, if supported by the FPU relaxed accept any binaries regardless of whether supported by the FPU The FPU emulator is always able to support both NaN encodings, so if no FPU hardware is present or it has been disabled with 'nofpu', then the settings of 'legacy' and '2008' strap the emulator accordingly, 'relaxed' straps the emulator for both legacy-NaN and 2008-NaN, whereas 'strict' enables legacy-NaN only on legacy processors and both NaN encodings on MIPS32 or MIPS64 CPUs. The setting for ABS.fmt/NEG.fmt instruction execution mode generally follows that for the NaN encoding, except where unsupported by hardware. ignore_loglevel [KNL,EARLY] Ignore loglevel setting - this will print /all/ kernel messages to the console. Useful for debugging. We also add it as printk module parameter, so users could change it dynamically, usually by /sys/module/printk/parameters/ignore_loglevel. ignore_rlimit_data Ignore RLIMIT_DATA setting for data mappings, print warning at first misuse. Can be changed via /sys/module/kernel/parameters/ignore_rlimit_data. ihash_entries= [KNL] Set number of hash buckets for inode cache. ima_appraise= [IMA] appraise integrity measurements Format: { "off" | "enforce" | "fix" | "log" } default: "enforce" ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead. The builtin appraise policy appraises all files owned by uid=0. ima_canonical_fmt [IMA] Use the canonical format for the binary runtime measurements, instead of host native format. ima_hash= [IMA] Format: { md5 | sha1 | rmd160 | sha256 | sha384 | sha512 | ... } default: "sha1" The list of supported hash algorithms is defined in crypto/hash_info.h. ima_policy= [IMA] The builtin policies to load during IMA setup. Format: "tcb | appraise_tcb | secure_boot | fail_securely | critical_data" The "tcb" policy measures all programs exec'd, files mmap'd for exec, and all files opened with the read mode bit set by either the effective uid (euid=0) or uid=0. The "appraise_tcb" policy appraises the integrity of all files owned by root. The "secure_boot" policy appraises the integrity of files (eg. kexec kernel image, kernel modules, firmware, policy, etc) based on file signatures. The "fail_securely" policy forces file signature verification failure also on privileged mounted filesystems with the SB_I_UNVERIFIABLE_SIGNATURE flag. The "critical_data" policy measures kernel integrity critical data. ima_tcb [IMA] Deprecated. Use ima_policy= instead. Load a policy which meets the needs of the Trusted Computing Base. This means IMA will measure all programs exec'd, files mmap'd for exec, and all files opened for read by uid=0. ima_template= [IMA] Select one of defined IMA measurements template formats. Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" | "ima-sigv2" } Default: "ima-ng" ima_template_fmt= [IMA] Define a custom template format. Format: { "field1|...|fieldN" } ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage Format:  Set the minimal file size for using asynchronous hash. If left unspecified, ahash usage is disabled. ahash performance varies for different data sizes on different crypto accelerators. This option can be used to achieve the best performance for a particular HW. ima.ahash_bufsize= [IMA] Asynchronous hash buffer size Format:  Set hashing buffer size. Default: 4k. ahash performance varies for different chunk sizes on different crypto accelerators. This option can be used to achieve best performance for particular HW. init= [KNL] Format:  Run specified binary instead of /sbin/init as init process. initcall_debug [KNL] Trace initcalls as they are executed. Useful for working out where the kernel is dying during startup. initcall_blacklist= [KNL] Do not execute a comma-separated list of initcall functions. Useful for debugging built-in modules and initcalls. initramfs_async= [KNL] Format:  Default: 1 This parameter controls whether the initramfs image is unpacked asynchronously, concurrently with devices being probed and initialized. This should normally just work, but as a debugging aid, one can get the historical behaviour of the initramfs unpacking being completed before device_ and late_ initcalls. initrd= [BOOT,EARLY] Specify the location of the initial ramdisk initrdmem= [KNL,EARLY] Specify a physical address and size from which to load the initrd. If an initrd is compiled in or specified in the bootparams, it takes priority over this setting. Format: ss[KMG],nn[KMG] Default is 0, 0 init_on_alloc= [MM,EARLY] Fill newly allocated pages and heap objects with zeroes. Format: 0 | 1 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON. init_on_free= [MM,EARLY] Fill freed pages and heap objects with zeroes. Format: 0 | 1 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON. init_pkru= [X86] Specify the default memory protection keys rights register contents for all processes. 0x55555554 by default (disallow access to all but pkey 0). Can override in debugfs after boot. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver Format:  int_pln_enable [X86] Enable power limit notification interrupt integrity_audit=[IMA] Format: { "0" | "1" } 0 -- basic integrity auditing messages. (Default) 1 -- additional integrity auditing messages. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option on Enable intel iommu driver. off Disable intel iommu driver. igfx_off [Default Off] By default, gfx is mapped as normal device. If a gfx device has a dedicated DMAR unit, the DMAR unit is bypassed by not enabling DMAR with this option. In this case, gfx device will use physical address for DMA. strict [Default Off] Deprecated, equivalent to iommu.strict=1. sp_off [Default Off] By default, super page will be supported if Intel IOMMU has the capability. With this option, super page will not be supported. sm_on Enable the Intel IOMMU scalable mode if the hardware advertises that it has support for the scalable mode translation. sm_off Disallow use of the Intel IOMMU scalable mode. tboot_noforce [Default Off] Do not force the Intel IOMMU enabled under tboot. By default, tboot will force Intel IOMMU on, which could harm performance of some high-throughput devices like 40GBit network cards, even if identity mapping is enabled. Note that using this option lowers the security provided by tboot because it makes the system vulnerable to DMA attacks. intel_idle.max_cstate= [KNL,HW,ACPI,X86] 0 disables intel_idle and fall back on acpi_idle. 1 to 9 specify maximum depth of C-state. intel_pstate= [X86,EARLY] disable Do not enable intel_pstate as the default scaling driver for the supported processors active Use intel_pstate driver to bypass the scaling governors layer of cpufreq and provides it own algorithms for p-state selection. There are two P-state selection algorithms provided by intel_pstate in the active mode: powersave and performance. The way they both operate depends on whether or not the hardware managed P-states (HWP) feature has been enabled in the processor and possibly on the processor model. passive Use intel_pstate as a scaling driver, but configure it to work with generic cpufreq governors (instead of enabling its internal governor). This mode cannot be used along with the hardware-managed P-states (HWP) feature. force Enable intel_pstate on systems that prohibit it by default in favor of acpi-cpufreq. Forcing the intel_pstate driver instead of acpi-cpufreq may disable platform features, such as thermal controls and power capping, that rely on ACPI P-States information being indicated to OSPM and therefore should be used with caution. This option does not work with processors that aren't supported by the intel_pstate driver or on platforms that use pcc-cpufreq instead of acpi-cpufreq. no_hwp Do not enable hardware P state control (HWP) if available. hwp_only Only load intel_pstate on systems which support hardware P state control (HWP) if available. support_acpi_ppc Enforce ACPI _PPC performance limits. If the Fixed ACPI Description Table, specifies preferred power management profile as "Enterprise Server" or "Performance Server", then this feature is turned on by default. per_cpu_perf_limits Allow per-logical-CPU P-State performance control limits using cpufreq sysfs interface intremap= [X86-64,Intel-IOMMU,EARLY] on enable Interrupt Remapping (default) off disable Interrupt Remapping nosid disable Source ID checking no_x2apic_optout BIOS x2APIC opt-out request will be ignored nopost disable Interrupt Posting iomem= Disable strict checking of access to MMIO memory strict regions from userspace. relaxed iommu= [X86,EARLY] off force noforce biomerge panic nopanic merge nomerge soft pt [X86] nopt [X86] nobypass [PPC/POWERNV] Disable IOMMU bypass, using IOMMU for PCI devices. iommu.forcedac= [ARM64,X86,EARLY] Control IOVA allocation for PCI devices. Format: { "0" | "1" } 0 - Try to allocate a 32-bit DMA address first, before falling back to the full range if needed. 1 - Allocate directly from the full usable range, forcing Dual Address Cycle for PCI cards supporting greater than 32-bit addressing. iommu.strict= [ARM64,X86,S390,EARLY] Configure TLB invalidation behaviour Format: { "0" | "1" } 0 - Lazy mode. Request that DMA unmap operations use deferred invalidation of hardware TLBs, for increased throughput at the cost of reduced device isolation. Will fall back to strict mode if not supported by the relevant IOMMU driver. 1 - Strict mode. DMA unmap operations invalidate IOMMU hardware TLBs synchronously. unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}. Note: on x86, strict mode specified via one of the legacy driver-specific options takes precedence. iommu.passthrough= [ARM64,X86,EARLY] Configure DMA to bypass the IOMMU by default. Format: { "0" | "1" } 0 - Use IOMMU translation for DMA. 1 - Bypass the IOMMU for DMA. unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. io7= [HW] IO7 for Marvel-based Alpha systems See comment before marvel_specify_io7 in arch/alpha/kernel/core_marvel.c. io_delay= [X86,EARLY] I/O delay method 0x80 Standard port 0x80 based delay 0xed Alternate port 0xed based delay (needed on some systems) udelay Simple two microseconds delay none No delay ip= [IP_PNP] See Documentation/admin-guide/nfs/nfsroot.rst. ipcmni_extend [KNL,EARLY] Extend the maximum number of unique System V IPC identifiers from 32,768 to 16,777,216. irqaffinity= [SMP] Set the default irq affinity mask The argument is a cpu list, as described above. irqchip.gicv2_force_probe= [ARM,ARM64,EARLY] Format:  Force the kernel to look for the second 4kB page of a GICv2 controller even if the memory range exposed by the device tree is too small. irqchip.gicv3_nolpi= [ARM,ARM64,EARLY] Force the kernel to ignore the availability of LPIs (and by consequence ITSs). Intended for system that use the kernel as a bootloader, and thus want to let secondary kernels in charge of setting up LPIs. irqchip.gicv3_pseudo_nmi= [ARM64,EARLY] Enables support for pseudo-NMIs in the kernel. This requires the kernel to be built with CONFIG_ARM64_PSEUDO_NMI. irqfixup [HW] When an interrupt is not handled search all handlers for it. Intended to get systems with badly broken firmware running. irqpoll [HW] When an interrupt is not handled search all handlers for it. Also check all handlers each timer interrupt. Intended to get systems with badly broken firmware running. isapnp= [ISAPNP] Format: ,,, isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance. [Deprecated - use cpusets instead] Format: [flag-list,] Specify one or more CPUs to isolate from disturbances specified in the flag list (default: domain): nohz Disable the tick when a single task runs. A residual 1Hz tick is offloaded to workqueues, which you need to affine to housekeeping through the global workqueue's affinity configured via the /sys/devices/virtual/workqueue/cpumask sysfs file, or by using the 'domain' flag described below. NOTE: by default the global workqueue runs on all CPUs, so to protect individual CPUs the 'cpumask' file has to be configured manually after bootup. domain Isolate from the general SMP balancing and scheduling algorithms. Note that performing domain isolation this way is irreversible: it's not possible to bring back a CPU to the domains once isolated through isolcpus. It's strongly advised to use cpusets instead to disable scheduler load balancing through the "cpuset.sched_load_balance" file. It offers a much more flexible interface where CPUs can move in and out of an isolated set anytime. You can move a process onto or off an "isolated" CPU via the CPU affinity syscalls or cpuset.  begins at 0 and the maximum value is "number of CPUs in system - 1". managed_irq Isolate from being targeted by managed interrupts which have an interrupt mask containing isolated CPUs. The affinity of managed interrupts is handled by the kernel and cannot be changed via the /proc/irq/* interfaces. This isolation is best effort and only effective if the automatically assigned interrupt mask of a device queue contains isolated and housekeeping CPUs. If housekeeping CPUs are online then such interrupts are directed to the housekeeping CPU so that IO submitted on the housekeeping CPU cannot disturb the isolated CPU. If a queue's affinity mask contains only isolated CPUs then this parameter has no effect on the interrupt routing decision, though interrupts are only delivered when tasks running on those isolated CPUs submit IO. IO submitted on housekeeping CPUs has no influence on those queues. The format of  is described above. iucv= [HW,NET] ivrs_ioapic [HW,X86-64] Provide an override to the IOAPIC-ID<->DEVICE-ID mapping provided in the IVRS ACPI table. By default, PCI segment is 0, and can be omitted. For example, to map IOAPIC-ID decimal 10 to PCI segment 0x1 and PCI device 00:14.0, write the parameter as: ivrs_ioapic=10@0001:00:14.0 Deprecated formats: * To map IOAPIC-ID decimal 10 to PCI device 00:14.0 write the parameter as: ivrs_ioapic[10]=00:14.0 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and PCI device 00:14.0 write the parameter as: ivrs_ioapic[10]=0001:00:14.0 ivrs_hpet [HW,X86-64] Provide an override to the HPET-ID<->DEVICE-ID mapping provided in the IVRS ACPI table. By default, PCI segment is 0, and can be omitted. For example, to map HPET-ID decimal 10 to PCI segment 0x1 and PCI device 00:14.0, write the parameter as: ivrs_hpet=10@0001:00:14.0 Deprecated formats: * To map HPET-ID decimal 0 to PCI device 00:14.0 write the parameter as: ivrs_hpet[0]=00:14.0 * To map HPET-ID decimal 10 to PCI segment 0x1 and PCI device 00:14.0 write the parameter as: ivrs_ioapic[10]=0001:00:14.0 ivrs_acpihid [HW,X86-64] Provide an override to the ACPI-HID:UID<->DEVICE-ID mapping provided in the IVRS ACPI table. By default, PCI segment is 0, and can be omitted. For example, to map UART-HID:UID AMD0020:0 to PCI segment 0x1 and PCI device ID 00:14.5, write the parameter as: ivrs_acpihid=AMD0020:0@0001:00:14.5 Deprecated formats: * To map UART-HID:UID AMD0020:0 to PCI segment is 0, PCI device ID 00:14.5, write the parameter as: ivrs_acpihid[00:14.5]=AMD0020:0 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and PCI device ID 00:14.5, write the parameter as: ivrs_acpihid[0001:00:14.5]=AMD0020:0 js= [HW,JOY] Analog joystick See Documentation/input/joydev/joystick.rst. kasan_multi_shot [KNL] Enforce KASAN (Kernel Address Sanitizer) to print report on every invalid memory access. Without this parameter KASAN will print report only for the first invalid access. keep_bootcon [KNL,EARLY] Do not unregister boot console at start. This is only useful for debugging when something happens in the window between unregistering the boot console and initializing the real console. keepinitrd [HW,ARM] See retain_initrd. kernelcore= [KNL,X86,IA-64,PPC,EARLY] Format: nn[KMGTPE] | nn% | "mirror" This parameter specifies the amount of memory usable by the kernel for non-movable allocations. The requested amount is spread evenly throughout all nodes in the system as ZONE_NORMAL. The remaining memory is used for movable memory in its own zone, ZONE_MOVABLE. In the event, a node is too small to have both ZONE_NORMAL and ZONE_MOVABLE, kernelcore memory will take priority and other nodes will have a larger ZONE_MOVABLE. ZONE_MOVABLE is used for the allocation of pages that may be reclaimed or moved by the page migration subsystem. Note that allocations like PTEs-from-HighMem still use the HighMem zone if it exists, and the Normal zone if it does not. It is possible to specify the exact amount of memory in the form of "nn[KMGTPE]", a percentage of total system memory in the form of "nn%", or "mirror". If "mirror" option is specified, mirrored (reliable) memory is used for non-movable allocations and remaining memory is used for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" are exclusive, so you cannot specify multiple forms. kgdbdbgp= [KGDB,HW,EARLY] kgdb over EHCI usb debug port. Format: [,poll interval] The controller # is the number of the ehci usb debug port as it is probed via PCI. The poll interval is optional and is the number seconds in between each poll cycle to the debug port in case you need the functionality for interrupting the kernel with gdb or control-c on the dbgp connection. When not using this parameter you use sysrq-g to break into the kernel debugger. kgdboc= [KGDB,HW] kgdb over consoles. Requires a tty driver that supports console polling, or a supported polling keyboard driver (non-usb). Serial only format: [,baud] keyboard only format: kbd keyboard and serial format: kbd,[,baud] Optional Kernel mode setting: kms, kbd format: kms,kbd kms, kbd and serial format: kms,kbd,[,baud] kgdboc_earlycon= [KGDB,HW,EARLY] If the boot console provides the ability to read characters and can work in polling mode, you can use this parameter to tell kgdb to use it as a backend until the normal console is registered. Intended to be used together with the kgdboc parameter which specifies the normal console to transition to. The name of the early console should be specified as the value of this parameter. Note that the name of the early console might be different than the tty name passed to kgdboc. It's OK to leave the value blank and the first boot console that implements read() will be picked. kgdbwait [KGDB,EARLY] Stop kernel execution and enter the kernel debugger at the earliest opportunity. kmac= [MIPS] Korina ethernet MAC address. Configure the RouterBoard 532 series on-chip Ethernet adapter MAC address. kmemleak= [KNL,EARLY] Boot-time kmemleak enable/disable Valid arguments: on, off Default: on Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, the default is off. kprobe_event=[probe-list] [FTRACE] Add kprobe events and enable at boot time. The probe-list is a semicolon delimited list of probe definitions. Each definition is same as kprobe_events interface, but the parameters are comma delimited. For example, to add a kprobe event on vfs_read with arg1 and arg2, add to the command line; kprobe_event=p,vfs_read,$arg1,$arg2 See also Documentation/trace/kprobetrace.rst "Kernel Boot Parameter" section. kpti= [ARM64,EARLY] Control page table isolation of user and kernel address spaces. Default: enabled on cores which need mitigation. 0: force disabled 1: force enabled kunit.enable= [KUNIT] Enable executing KUnit tests. Requires CONFIG_KUNIT to be set to be fully enabled. The default value can be overridden via KUNIT_DEFAULT_ENABLED. Default is 1 (enabled) kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. Default is 0 (don't ignore, but inject #GP) kvm.eager_page_split= [KVM,X86] Controls whether or not KVM will try to proactively split all huge pages during dirty logging. Eager page splitting reduces interruptions to vCPU execution by eliminating the write-protection faults and MMU lock contention that would otherwise be required to split huge pages lazily. VM workloads that rarely perform writes or that write only to a small region of VM memory may benefit from disabling eager page splitting to allow huge pages to still be used for reads. The behavior of eager page splitting depends on whether KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If disabled, all huge pages in a memslot will be eagerly split when dirty logging is enabled on that memslot. If enabled, eager page splitting will be performed during the KVM_CLEAR_DIRTY ioctl, and only for the pages being cleared. Eager page splitting is only supported when kvm.tdp_mmu=Y. Default is Y (on). kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface. Default is false (don't support). kvm.nx_huge_pages= [KVM] Controls the software workaround for the X86_BUG_ITLB_MULTIHIT bug. force : Always deploy workaround. off : Never deploy workaround. auto : Deploy workaround based on the presence of X86_BUG_ITLB_MULTIHIT. Default is 'auto'. If the software workaround is enabled for the host, guests do need not to enable it for nested guests. kvm.nx_huge_pages_recovery_ratio= [KVM] Controls how many 4KiB pages are periodically zapped back to huge pages. 0 disables the recovery, otherwise if the value is N KVM will zap 1/Nth of the 4KiB pages every period (see below). The default is 60. kvm.nx_huge_pages_recovery_period_ms= [KVM] Controls the time period at which KVM zaps 4KiB pages back to huge pages. If the value is a non-zero N, KVM will zap a portion (see ratio above) of the pages every N msecs. If the value is 0 (the default), KVM will pick a period based on the ratio, such that a page is zapped after 1 hour on average. kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in KVM/SVM. Default is 1 (enabled). kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables, a.k.a. Two-Dimensional Page Tables. Default is 1 (enabled). Disable by KVM if hardware lacks support for NPT. kvm-arm.mode= [KVM,ARM,EARLY] Select one of KVM/arm64's modes of operation. none: Forcefully disable KVM. nvhe: Standard nVHE-based mode, without support for protected guests. protected: nVHE-based mode with support for guests whose state is kept private from the host. nested: VHE-based mode with support for nested virtualization. Requires at least ARMv8.3 hardware. Defaults to VHE/nVHE based on hardware support. Setting mode to "protected" will disable kexec and hibernation for the host. "nested" is experimental and should be used with extreme caution. kvm-arm.vgic_v3_group0_trap= [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0 system registers kvm-arm.vgic_v3_group1_trap= [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-1 system registers kvm-arm.vgic_v3_common_trap= [KVM,ARM,EARLY] Trap guest accesses to GICv3 common system registers kvm-arm.vgic_v4_enable= [KVM,ARM,EARLY] Allow use of GICv4 for direct injection of LPIs. kvm_cma_resv_ratio=n [PPC,EARLY] Reserves given percentage from system memory area for contiguous memory allocation for KVM hash pagetable allocation. By default it reserves 5% of total system memory. Format:  Default: 5 kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables, a.k.a. Two-Dimensional Page Tables. Default is 1 (enabled). Disable by KVM if hardware lacks support for EPT. kvm-intel.emulate_invalid_guest_state= [KVM,Intel] Control whether to emulate invalid guest state. Ignored if kvm-intel.enable_unrestricted_guest=1, as guest state is never invalid for unrestricted guests. This param doesn't apply to nested guests (L2), as KVM never emulates invalid L2 guest state. Default is 1 (enabled). kvm-intel.flexpriority= [KVM,Intel] Control KVM's use of FlexPriority feature (TPR shadow). Default is 1 (enabled). Disable by KVM if hardware lacks support for it. kvm-intel.nested= [KVM,Intel] Control nested virtualization feature in KVM/VMX. Default is 1 (enabled). kvm-intel.unrestricted_guest= [KVM,Intel] Control KVM's use of unrestricted guest feature (virtualized real and unpaged mode). Default is 1 (enabled). Disable by KVM if EPT is disabled or hardware lacks support for it. kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault CVE-2018-3620. Valid arguments: never, cond, always always: L1D cache flush on every VMENTER. cond: Flush L1D on VMENTER only when the code between VMEXIT and VMENTER can leak host memory. never: Disables the mitigation Default is cond (do L1 cache flush in specific instances) kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor Identification feature (tagged TLBs). Default is 1 (enabled). Disable by KVM if hardware lacks support for it. l1d_flush= [X86,INTEL,EARLY] Control mitigation for L1D based snooping vulnerability. Certain CPUs are vulnerable to an exploit against CPU internal buffers which can forward information to a disclosure gadget under certain conditions. In vulnerable processors, the speculatively forwarded data can be used in a cache side channel attack, to access data to which the attacker does not have direct access. This parameter controls the mitigation. The options are: on - enable the interface for the mitigation l1tf= [X86,EARLY] Control mitigation of the L1TF vulnerability on affected CPUs The kernel PTE inversion protection is unconditionally enabled and cannot be disabled. full Provides all available mitigations for the L1TF vulnerability. Disables SMT and enables all mitigations in the hypervisors, i.e. unconditional L1D flush. SMT control and L1D flush control via the sysfs interface is still possible after boot. Hypervisors will issue a warning when the first VM is started in a potentially insecure configuration, i.e. SMT enabled or L1D flush disabled. full,force Same as 'full', but disables SMT and L1D flush runtime control. Implies the 'nosmt=force' command line option. (i.e. sysfs control of SMT is disabled.) flush Leaves SMT enabled and enables the default hypervisor mitigation, i.e. conditional L1D flush. SMT control and L1D flush control via the sysfs interface is still possible after boot. Hypervisors will issue a warning when the first VM is started in a potentially insecure configuration, i.e. SMT enabled or L1D flush disabled. flush,nosmt Disables SMT and enables the default hypervisor mitigation. SMT control and L1D flush control via the sysfs interface is still possible after boot. Hypervisors will issue a warning when the first VM is started in a potentially insecure configuration, i.e. SMT enabled or L1D flush disabled. flush,nowarn Same as 'flush', but hypervisors will not warn when a VM is started in a potentially insecure configuration. off Disables hypervisor mitigations and doesn't emit any warnings. It also drops the swap size and available RAM limit restriction on both hypervisor and bare metal. Default is 'flush'. For details see: Documentation/admin-guide/hw-vuln/l1tf.rst l2cr= [PPC] l3cr= [PPC] lapic [X86-32,APIC,EARLY] Enable the local APIC even if BIOS disabled it. lapic= [X86,APIC] Do not use TSC deadline value for LAPIC timer one-shot implementation. Default back to the programmable timer unit in the LAPIC. Format: notscdeadline lapic_timer_c2_ok [X86,APIC,EARLY] trust the local apic timer in C2 power state. libata.dma= [LIBATA] DMA control libata.dma=0 Disable all PATA and SATA DMA libata.dma=1 PATA and SATA Disk DMA only libata.dma=2 ATAPI (CDROM) DMA only libata.dma=4 Compact Flash DMA only Combinations also work, so libata.dma=3 enables DMA for disks and CDROMs, but not CFs. libata.ignore_hpa= [LIBATA] Ignore HPA limit libata.ignore_hpa=0 keep BIOS limits (default) libata.ignore_hpa=1 ignore limits, using full disk libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume when set. Format:  libata.force= [LIBATA] Force configurations. The format is a comma- separated list of "[ID:]VAL" where ID is PORT[.DEVICE]. PORT and DEVICE are decimal numbers matching port, link or device. Basically, it matches the ATA ID string printed on console by libata. If the whole ID part is omitted, the last PORT and DEVICE values are used. If ID hasn't been specified yet, the configuration applies to all ports, links and devices. If only DEVICE is omitted, the parameter applies to the port and all links and devices behind it. DEVICE number of 0 either selects the first device or the first fan-out link behind PMP device. It does not select the host link. DEVICE number of 15 selects the host link and device attached to it. The VAL specifies the configuration to force. As long as there is no ambiguity, shortcut notation is allowed. For example, both 1.5 and 1.5G would work for 1.5Gbps. The following configurations can be forced. * Cable type: 40c, 80c, short40c, unk, ign or sata. Any ID with matching PORT is used. * SATA link speed limit: 1.5Gbps or 3.0Gbps. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. udma[/][16,25,33,44,66,100,133] notation is also allowed. * nohrst, nosrst, norst: suppress hard, soft and both resets. * rstonce: only attempt one reset during hot-unplug link recovery. * [no]dbdelay: Enable or disable the extra 200ms delay before debouncing a link PHY and device presence detection. * [no]ncq: Turn on or off NCQ. * [no]ncqtrim: Enable or disable queued DSM TRIM. * [no]ncqati: Enable or disable NCQ trim on ATI chipset. * [no]trim: Enable or disable (unqueued) TRIM. * trim_zero: Indicate that TRIM command zeroes data. * max_trim_128m: Set 128M maximum trim size limit. * [no]dma: Turn on or off DMA transfers. * atapi_dmadir: Enable ATAPI DMADIR bridge support. * atapi_mod16_dma: Enable the use of ATAPI DMA for commands that are not a multiple of 16 bytes. * [no]dmalog: Enable or disable the use of the READ LOG DMA EXT command to access logs. * [no]iddevlog: Enable or disable access to the identify device data log. * [no]logdir: Enable or disable access to the general purpose log directory. * max_sec_128: Set transfer size limit to 128 sectors. * max_sec_1024: Set or clear transfer size limit to 1024 sectors. * max_sec_lba48: Set or clear transfer size limit to 65535 sectors. * [no]lpm: Enable or disable link power management. * [no]setxfer: Indicate if transfer speed mode setting should be skipped. * [no]fua: Disable or enable FUA (Force Unit Access) support for devices supporting this feature. * dump_id: Dump IDENTIFY data. * disable: Disable this device. If there are multiple matching configurations changing the same attribute, the last one is used. load_ramdisk= [RAM] [Deprecated] lockd.nlm_grace_period=P [NFS] Assign grace period. Format:  lockd.nlm_tcpport=N [NFS] Assign TCP port. Format:  lockd.nlm_timeout=T [NFS] Assign timeout value. Format:  lockd.nlm_udpport=M [NFS] Assign UDP port. Format:  lockdown= [SECURITY,EARLY] { integrity | confidentiality } Enable the kernel lockdown feature. If set to integrity, kernel features that allow userland to modify the running kernel are disabled. If set to confidentiality, kernel features that allow userland to extract confidential information from the kernel are also disabled. locktorture.acq_writer_lim= [KNL] Set the time limit in jiffies for a lock acquisition. Acquisitions exceeding this limit will result in a splat once they do complete. locktorture.bind_readers= [KNL] Specify the list of CPUs to which the readers are to be bound. locktorture.bind_writers= [KNL] Specify the list of CPUs to which the writers are to be bound. locktorture.call_rcu_chains= [KNL] Specify the number of self-propagating call_rcu() chains to set up. These are used to ensure that there is a high probability of an RCU grace period in progress at any given time. Defaults to 0, which disables these call_rcu() chains. locktorture.long_hold= [KNL] Specify the duration in milliseconds for the occasional long-duration lock hold time. Defaults to 100 milliseconds. Select 0 to disable. locktorture.nested_locks= [KNL] Specify the maximum lock nesting depth that locktorture is to exercise, up to a limit of 8 (MAX_NESTED_LOCKS). Specify zero to disable. Note that this parameter is ineffective on types of locks that do not support nested acquisition. locktorture.nreaders_stress= [KNL] Set the number of locking read-acquisition kthreads. Defaults to being automatically set based on the number of online CPUs. locktorture.nwriters_stress= [KNL] Set the number of locking write-acquisition kthreads. locktorture.onoff_holdoff= [KNL] Set time (s) after boot for CPU-hotplug testing. locktorture.onoff_interval= [KNL] Set time (s) between CPU-hotplug operations, or zero to disable CPU-hotplug testing. locktorture.rt_boost= [KNL] Do periodic testing of real-time lock priority boosting. Select 0 to disable, 1 to boost only rt_mutex, and 2 to boost unconditionally. Defaults to 2, which might seem to be an odd choice, but which should be harmless for non-real-time spinlocks, due to their disabling of preemption. Note that non-realtime mutexes disable boosting. locktorture.rt_boost_factor= [KNL] Number that determines how often and for how long priority boosting is exercised. This is scaled down by the number of writers, so that the number of boosts per unit time remains roughly constant as the number of writers increases. On the other hand, the duration of each boost increases with the number of writers. locktorture.shuffle_interval= [KNL] Set task-shuffle interval (jiffies). Shuffling tasks allows some CPUs to go into dyntick-idle mode during the locktorture test. locktorture.shutdown_secs= [KNL] Set time (s) after boot system shutdown. This is useful for hands-off automated testing. locktorture.stat_interval= [KNL] Time (s) between statistics printk()s. locktorture.stutter= [KNL] Time (s) to stutter testing, for example, specifying five seconds causes the test to run for five seconds, wait for five seconds, and so on. This tests the locking primitive's ability to transition abruptly to and from idle. locktorture.torture_type= [KNL] Specify the locking implementation to test. locktorture.verbose= [KNL] Enable additional printk() statements. locktorture.writer_fifo= [KNL] Run the write-side locktorture kthreads at sched_set_fifo() real-time priority. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver Format:  loglevel= [KNL,EARLY] All Kernel Messages with a loglevel smaller than the console loglevel will be printed to the console. It can also be changed with klogd or other programs. The loglevels are defined as follows: 0 (KERN_EMERG) system is unusable 1 (KERN_ALERT) action must be taken immediately 2 (KERN_CRIT) critical conditions 3 (KERN_ERR) error conditions 4 (KERN_WARNING) warning conditions 5 (KERN_NOTICE) normal but significant condition 6 (KERN_INFO) informational 7 (KERN_DEBUG) debug-level messages log_buf_len=n[KMG] [KNL,EARLY] Sets the size of the printk ring buffer, in bytes. n must be a power of two and greater than the minimal size. The minimal size is defined by LOG_BUF_SHIFT kernel config parameter. There is also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter that allows to increase the default size depending on the number of CPUs. See init/Kconfig for more details. logo.nologo [FB] Disables display of the built-in Linux logo. This may be used to provide more screen space for kernel log messages and is useful when debugging kernel boot problems. lp=0 [LP] Specify parallel ports to use, e.g, lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses lp=reset first parallel port). 'lp=0' disables the lp=auto printer driver. 'lp=reset' (which can be specified in addition to the ports) causes attached printers to be reset. Using lp=port1,port2,... specifies the parallel ports to associate lp devices with, starting with lp0. A port specification may be 'none' to skip that lp device, or a parport name such as 'parport0'. Specifying 'lp=auto' instead of a port specification list means that device IDs from each port should be examined, to see if an IEEE 1284-compliant printer is attached; if so, the driver will manage that printer. See also header of drivers/char/lp.c. lpj=n [KNL] Sets loops_per_jiffy to given constant, thus avoiding time-consuming boot-time autodetection (up to 250 ms per CPU). 0 enables autodetection (default). To determine the correct value for your kernel, boot with normal autodetection and see what value is printed. Note that on SMP systems the preset will be applied to all CPUs, which is likely to cause problems if your CPUs need significantly divergent settings. An incorrect value will cause delays in the kernel to be wrong, leading to unpredictable I/O errors and other breakage. Although unlikely, in the extreme case this might damage your hardware. ltpc= [NET] Format: ,, lsm.debug [SECURITY] Enable LSM initialization debugging output. lsm=lsm1,...,lsmN [SECURITY] Choose order of LSM initialization. This overrides CONFIG_LSM, and the "security=" parameter. machvec= [IA-64] Force the use of a particular machine-vector (machvec) in a generic kernel. Example: machvec=hpzx1 machtype= [Loongson] Share the same kernel image file between different yeeloong laptops. Example: machtype=lemote-yeeloong-2f-7inch max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater than or equal to this physical address is ignored. maxcpus= [SMP,EARLY] Maximum number of processors that an SMP kernel will bring up during bootup. maxcpus=n : n >= 0 limits the kernel to bring up 'n' processors. Surely after bootup you can bring up the other plugged cpu by executing "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus only takes effect during system bootup. While n=0 is a special case, it is equivalent to "nosmp", which also disables the IO APIC. max_loop= [LOOP] The number of loop block devices that get (loop.max_loop) unconditionally pre-created at init time. The default number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead of statically allocating a predefined number, loop devices can be requested on-demand with the /dev/loop-control interface. mce [X86-32] Machine Check Exception mce=option [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst md= [HW] RAID subsystems devices and level See Documentation/admin-guide/md.rst. mdacon= [MDA] Format: , Specifies range of consoles to be captured by the MDA. mds= [X86,INTEL,EARLY] Control mitigation for the Micro-architectural Data Sampling (MDS) vulnerability. Certain CPUs are vulnerable to an exploit against CPU internal buffers which can forward information to a disclosure gadget under certain conditions. In vulnerable processors, the speculatively forwarded data can be used in a cache side channel attack, to access data to which the attacker does not have direct access. This parameter controls the MDS mitigation. The options are: full - Enable MDS mitigation on vulnerable CPUs full,nosmt - Enable MDS mitigation and disable SMT on vulnerable CPUs off - Unconditionally disable MDS mitigation On TAA-affected machines, mds=off can be prevented by an active TAA mitigation as both vulnerabilities are mitigated with the same mechanism so in order to disable this mitigation, you need to specify tsx_async_abort=off too. Not specifying this option is equivalent to mds=full. For details see: Documentation/admin-guide/hw-vuln/mds.rst mem=nn[KMG] [HEXAGON,EARLY] Set the memory size. Must be specified, otherwise memory size will be 0. mem=nn[KMG] [KNL,BOOT,EARLY] Force usage of a specific amount of memory Amount of memory to be used in cases as follows: 1 for test; 2 when the kernel is not able to see the whole system memory; 3 memory that lies after 'mem=' boundary is excluded from the hypervisor, then assigned to KVM guests. 4 to limit the memory available for kdump kernel. [ARC,MICROBLAZE] - the limit applies only to low memory, high memory is not affected. [ARM64] - only limits memory covered by the linear mapping. The NOMAP regions are not affected. [X86] Work as limiting max address. Use together with memmap= to avoid physical address space collisions. Without memmap= PCI devices could be placed at addresses belonging to unused RAM. Note that this only takes effects during boot time since in above case 3, memory may need be hot added after boot if system memory of hypervisor is not sufficient. mem=nn[KMG]@ss[KMG] [ARM,MIPS,EARLY] - override the memory layout reported by firmware. Define a memory region of size nn[KMG] starting at ss[KMG]. Multiple different regions can be specified with multiple mem= parameters on the command line. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel memory. memblock=debug [KNL,EARLY] Enable memblock debug messages. memchunk=nn[KMG] [KNL,SH] Allow user to override the default size for per-device physically contiguous DMA buffers. memhp_default_state=online/offline/online_kernel/online_movable [KNL] Set the initial state for the memory hotplug onlining policy. If not specified, the default value is set according to the CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config option. See Documentation/admin-guide/mm/memory-hotplug.rst. memmap=exactmap [KNL,X86,EARLY] Enable setting of an exact E820 memory map, as specified by the user. Such memmap=exactmap lines can be constructed based on BIOS output or other requirements. See the memmap=nn@ss option description. memmap=nn[KMG]@ss[KMG] [KNL, X86,MIPS,XTENSA,EARLY] Force usage of a specific region of memory. Region of memory to be used is from ss to ss+nn. If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG], which limits max address to nn[KMG]. Multiple different regions can be specified, comma delimited. Example: memmap=100M@2G,100M#3G,1G!1024G memmap=nn[KMG]#ss[KMG] [KNL,ACPI,EARLY] Mark specific memory as ACPI data. Region of memory to be marked is from ss to ss+nn. memmap=nn[KMG]$ss[KMG] [KNL,ACPI,EARLY] Mark specific memory as reserved. Region of memory to be reserved is from ss to ss+nn. Example: Exclude memory from 0x18690000-0x1869ffff memmap=64K$0x18690000 or memmap=0x10000$0x18690000 Some bootloaders may need an escape character before '$', like Grub2, otherwise '$' and the following number will be eaten. memmap=nn[KMG]!ss[KMG,EARLY] [KNL,X86] Mark specific memory as protected. Region of memory to be used, from ss to ss+nn. The memory region may be marked as e820 type 12 (0xc) and is NVDIMM or ADR memory. memmap=%-+ [KNL,ACPI,EARLY] Convert memory within the specified region from  to . If "-" is left out, the whole region will be marked as , even if previously unavailable. If "+" is left out, matching memory will be removed. Types are specified as e820 types, e.g., 1 = RAM, 2 = reserved, 3 = ACPI, 12 = PRAM. memory_corruption_check=0/1 [X86,EARLY] Some BIOSes seem to corrupt the first 64k of memory when doing things like suspend/resume. Setting this option will scan the memory looking for corruption. Enabling this will both detect corruption and prevent the kernel from using the memory being corrupted. However, its intended as a diagnostic tool; if repeatable BIOS-originated corruption always affects the same memory, you can use memmap= to prevent the kernel from using that memory. memory_corruption_check_size=size [X86,EARLY] By default it checks for corruption in the low 64k, making this memory unavailable for normal use. Use this parameter to scan for corruption in more or less memory. memory_corruption_check_period=seconds [X86,EARLY] By default it checks for corruption every 60 seconds. Use this parameter to check at some other rate. 0 disables periodic checking. memory_hotplug.memmap_on_memory [KNL,X86,ARM] Boolean flag to enable this feature. Format: {on | off (default)} When enabled, runtime hotplugged memory will allocate its internal metadata (struct pages, those vmemmap pages cannot be optimized even if hugetlb_free_vmemmap is enabled) from the hotadded memory which will allow to hotadd a lot of memory without requiring additional memory to do so. This feature is disabled by default because it has some implication on large (e.g. GB) allocations in some configurations (e.g. small memory blocks). The state of the flag can be read in /sys/module/memory_hotplug/parameters/memmap_on_memory. Note that even when enabled, there are a few cases where the feature is not effective. memtest= [KNL,X86,ARM,M68K,PPC,RISCV,EARLY] Enable memtest Format:  default : 0  Specifies the number of memtest passes to be performed. Each pass selects another test pattern from a given set of patterns. Memtest fills the memory with this pattern, validates memory contents and reserves bad memory regions that are detected. mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control Valid arguments: on, off Default: off mem_encrypt=on: Activate SME mem_encrypt=off: Do not activate SME Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst for details on when memory encryption can be activated. mem_sleep_default= [SUSPEND] Default system suspend mode: s2idle - Suspend-To-Idle shallow - Power-On Suspend or equivalent (if supported) deep - Suspend-To-RAM or equivalent (if supported) See Documentation/admin-guide/pm/sleep-states.rst. mfgpt_irq= [IA-32] Specify the IRQ to use for the Multi-Function General Purpose Timers on AMD Geode platforms. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when the BIOS has incorrectly applied a workaround. TinyBIOS version 0.98 is known to be affected, 0.99 fixes the problem by letting the user disable the workaround. mga= [HW,DRM] microcode.force_minrev= [X86] Format:  Enable or disable the microcode minimal revision enforcement for the runtime microcode loader. min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this physical address is ignored. mini2440= [ARM,HW,KNL] Format:[0..2][b][c][t] Default: "0tb" MINI2440 configuration specification: 0 - The attached screen is the 3.5" TFT 1 - The attached screen is the 7" TFT 2 - The VGA Shield is attached (1024x768) Leaving out the screen size parameter will not load the TFT driver, and the framebuffer will be left unconfigured. b - Enable backlight. The TFT backlight pin will be linked to the kernel VESA blanking code and a GPIO LED. This parameter is not necessary when using the VGA shield. c - Enable the s3c camera interface. t - Reserved for enabling touchscreen support. The touchscreen support is not enabled in the mainstream kernel as of 2.6.30, a preliminary port can be found in the "bleeding edge" mini2440 support kernel at https://repo.or.cz/w/linux-2.6/mini2440.git mitigations= [X86,PPC,S390,ARM64,EARLY] Control optional mitigations for CPU vulnerabilities. This is a set of curated, arch-independent options, each of which is an aggregation of existing arch-specific options. Note, "mitigations" is supported if and only if the kernel was built with CPU_MITIGATIONS=y. off Disable all optional CPU mitigations. This improves system performance, but it may also expose users to several CPU vulnerabilities. Equivalent to: if nokaslr then kpti=0 [ARM64] gather_data_sampling=off [X86] kvm.nx_huge_pages=off [X86] l1tf=off [X86] mds=off [X86] mmio_stale_data=off [X86] no_entry_flush [PPC] no_uaccess_flush [PPC] nobp=0 [S390] nopti [X86,PPC] nospectre_bhb [ARM64] nospectre_v1 [X86,PPC] nospectre_v2 [X86,PPC,S390,ARM64] reg_file_data_sampling=off [X86] retbleed=off [X86] spec_rstack_overflow=off [X86] spec_store_bypass_disable=off [X86,PPC] spectre_bhi=off [X86] spectre_v2_user=off [X86] srbds=off [X86,INTEL] ssbd=force-off [ARM64] tsx_async_abort=off [X86] Exceptions: This does not have any effect on kvm.nx_huge_pages when kvm.nx_huge_pages=force. auto (default) Mitigate all CPU vulnerabilities, but leave SMT enabled, even if it's vulnerable. This is for users who don't want to be surprised by SMT getting disabled across kernel upgrades, or who have other ways of avoiding SMT-based attacks. Equivalent to: (default behavior) auto,nosmt Mitigate all CPU vulnerabilities, disabling SMT if needed. This is for users who always want to be fully mitigated, even if it means losing SMT. Equivalent to: l1tf=flush,nosmt [X86] mds=full,nosmt [X86] tsx_async_abort=full,nosmt [X86] mmio_stale_data=full,nosmt [X86] retbleed=auto,nosmt [X86] mminit_loglevel= [KNL,EARLY] When CONFIG_DEBUG_MEMORY_INIT is set, this parameter allows control of the logging verbosity for the additional memory initialisation checks. A value of 0 disables mminit logging and a level of 4 will log everything. Information is printed at KERN_DEBUG so loglevel=8 may also need to be specified. mmio_stale_data= [X86,INTEL,EARLY] Control mitigation for the Processor MMIO Stale Data vulnerabilities. Processor MMIO Stale Data is a class of vulnerabilities that may expose data after an MMIO operation. Exposed data could originate or end in the same CPU buffers as affected by MDS and TAA. Therefore, similar to MDS and TAA, the mitigation is to clear the affected CPU buffers. This parameter controls the mitigation. The options are: full - Enable mitigation on vulnerable CPUs full,nosmt - Enable mitigation and disable SMT on vulnerable CPUs. off - Unconditionally disable mitigation On MDS or TAA affected machines, mmio_stale_data=off can be prevented by an active MDS or TAA mitigation as these vulnerabilities are mitigated with the same mechanism so in order to disable this mitigation, you need to specify mds=off and tsx_async_abort=off too. Not specifying this option is equivalent to mmio_stale_data=full. For details see: Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst .async_probe[=] [KNL] If no  value is specified or if the value specified is not a valid , enable asynchronous probe on this module. Otherwise, enable/disable asynchronous probe on this module as indicated by the  value. See also: module.async_probe module.async_probe= [KNL] When set to true, modules will use async probing by default. To enable/disable async probing for a specific module, use the module specific control that is documented under .async_probe. When both module.async_probe and .async_probe are specified, .async_probe takes precedence for the specific module. module.enable_dups_trace [KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set, this means that duplicate request_module() calls will trigger a WARN_ON() instead of a pr_warn(). Note that if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s will always be issued and this option does nothing. module.sig_enforce [KNL] When CONFIG_MODULE_SIG is set, this means that modules without (valid) signatures will fail to load. Note that if CONFIG_MODULE_SIG_FORCE is set, that is always true, so this option does nothing. module_blacklist= [KNL] Do not load a comma-separated list of modules. Useful for debugging problem modules. mousedev.tap_time= [MOUSE] Maximum time between finger touching and leaving touchpad surface for touch to be considered a tap and be reported as a left button click (for touchpads working in absolute mode only). Format:  mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices reporting absolute coordinates, such as tablets mousedev.yres= [MOUSE] Vertical screen resolution, used for devices reporting absolute coordinates, such as tablets movablecore= [KNL,X86,IA-64,PPC,EARLY] Format: nn[KMGTPE] | nn% This parameter is the complement to kernelcore=, it specifies the amount of memory used for migratable allocations. If both kernelcore and movablecore is specified, then kernelcore will be at *least* the specified value but may be more. If movablecore on its own is specified, the administrator must be careful that the amount of memory usable for all allocations is not too small. movable_node [KNL,EARLY] Boot-time switch to make hotplugable memory NUMA nodes to be movable. This means that the memory of such nodes will be usable only for movable allocations which rules out almost all kernel allocations. Use with caution! MTD_Partition= [MTD] Format: ,,, MTD_Region= [MTD] Format: ,[,,,,] mtdparts= [MTD] See drivers/mtd/parsers/cmdlinepart.c mtdset= [ARM] ARM/S3C2412 JIVE boot control See arch/arm/mach-s3c/mach-jive.c mtouchusb.raw_coordinates= [HW] Make the MicroTouch USB driver use raw coordinates ('y', default) or cooked coordinates ('n') mtrr=debug [X86,EARLY] Enable printing debug information related to MTRR registers at boot time. mtrr_chunk_size=nn[KMG,X86,EARLY] used for mtrr cleanup. It is largest continuous chunk that could hold holes aka. UC entries. mtrr_gran_size=nn[KMG,X86,EARLY] Used for mtrr cleanup. It is granularity of mtrr block. Default is 1. Large value could prevent small alignment from using up MTRRs. mtrr_spare_reg_nr=n [X86,EARLY] Format:  Range: 0,7 : spare reg number Default : 1 Used for mtrr cleanup. It is spare mtrr entries number. Set to 2 or more if your graphical card needs more. multitce=off [PPC] This parameter disables the use of the pSeries firmware feature for updating multiple TCE entries at a time. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card netdev= [NET] Network devices parameters Format: ,,,, Note that mem_start is often overloaded to mean something different and driver-specific. This usage is only documented in each driver source file if at all. netpoll.carrier_timeout= [NET] Specifies amount of time (in seconds) that netpoll should wait for a carrier. By default netpoll waits 4 seconds. nf_conntrack.acct= [NETFILTER] Enable connection tracking flow accounting 0 to disable accounting 1 to enable accounting Default value is 0. nfs.cache_getent= [NFS] sets the pathname to the program which is used to update the NFS client cache entries. nfs.cache_getent_timeout= [NFS] sets the timeout after which an attempt to update a cache entry is deemed to have failed. nfs.callback_nr_threads= [NFSv4] set the total number of threads that the NFS client will assign to service NFSv4 callback requests. nfs.callback_tcpport= [NFS] set the TCP port on which the NFSv4 callback channel should listen. nfs.delay_retrans= [NFS] specifies the number of times the NFSv4 client retries the request before returning an EAGAIN error, after a reply of NFS4ERR_DELAY from the server. Only applies if the softerr mount option is enabled, and the specified value is >= 0. nfs.enable_ino64= [NFS] enable 64-bit inode numbers. If zero, the NFS client will fake up a 32-bit inode number for the readdir() and stat() syscalls instead of returning the full 64-bit number. The default is to return 64-bit inode numbers. nfs.idmap_cache_timeout= [NFS] set the maximum lifetime for idmapper cache entries. nfs.max_session_cb_slots= [NFSv4.1] Sets the maximum number of session slots the client will assign to the callback channel. This determines the maximum number of callbacks the client will process in parallel for a particular server. nfs.max_session_slots= [NFSv4.1] Sets the maximum number of session slots the client will attempt to negotiate with the server. This limits the number of simultaneous RPC requests that the client can send to the NFSv4.1 server. Note that there is little point in setting this value higher than the max_tcp_slot_table_limit. nfs.nfs4_disable_idmapping= [NFSv4] When set to the default of '1', this option ensures that both the RPC level authentication scheme and the NFS level operations agree to use numeric uids/gids if the mount is using the 'sec=sys' security flavour. In effect it is disabling idmapping, which can make migration from legacy NFSv2/v3 systems to NFSv4 easier. Servers that do not support this mode of operation will be autodetected by the client, and it will fall back to using the idmapper. To turn off this behaviour, set the value to '0'. nfs.nfs4_unique_id= [NFS4] Specify an additional fixed unique ident- ification string that NFSv4 clients can insert into their nfs_client_id4 string. This is typically a UUID that is generated at system install time. nfs.recover_lost_locks= [NFSv4] Attempt to recover locks that were lost due to a lease timeout on the server. Please note that doing this risks data corruption, since there are no guarantees that the file will remain unchanged after the locks are lost. If you want to enable the kernel legacy behaviour of attempting to recover these locks, then set this parameter to '1'. The default parameter value of '0' causes the kernel not to attempt recovery of lost locks. nfs.send_implementation_id= [NFSv4.1] Send client implementation identification information in exchange_id requests. If zero, no implementation identification information will be sent. The default is to send the implementation identification information. nfs4.layoutstats_timer= [NFSv4.2] Change the rate at which the kernel sends layoutstats to the pNFS metadata server. Setting this to value to 0 causes the kernel to use whatever value is the default set by the layout driver. A non-zero value sets the minimum interval in seconds between layoutstats transmissions. nfsd.inter_copy_offload_enable= [NFSv4.2] When set to 1, the server will support server-to-server copies for which this server is the destination of the copy. nfsd.nfs4_disable_idmapping= [NFSv4] When set to the default of '1', the NFSv4 server will return only numeric uids and gids to clients using auth_sys, and will accept numeric uids and gids from such clients. This is intended to ease migration from NFSv2/v3. nfsd.nfsd4_ssc_umount_timeout= [NFSv4.2] When used as the destination of a server-to-server copy, knfsd temporarily mounts the source server. It caches the mount in case it will be needed again, and discards it if not used for the number of milliseconds specified by this parameter. nfsaddrs= [NFS] Deprecated. Use ip= instead. See Documentation/admin-guide/nfs/nfsroot.rst. nfsroot= [NFS] nfs root filesystem for disk-less boxes. See Documentation/admin-guide/nfs/nfsroot.rst. nfsrootdebug [NFS] enable nfsroot debugging messages. See Documentation/admin-guide/nfs/nfsroot.rst. nmi_backtrace.backtrace_idle [KNL] Dump stacks even of idle CPUs in response to an NMI stack-backtrace request. nmi_debug= [KNL,SH] Specify one or more actions to take when a NMI is triggered. Format: [state][,regs][,debounce][,die] nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels Format: [panic,][nopanic,][num] Valid num: 0 or 1 0 - turn hardlockup detector in nmi_watchdog off 1 - turn hardlockup detector in nmi_watchdog on When panic is specified, panic when an NMI watchdog timeout occurs (or 'nopanic' to not panic on an NMI watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) To disable both hard and soft lockup detectors, please see 'nowatchdog'. This is useful when you use a panic=... timeout and need the box quickly up again. These settings can be accessed at runtime via the nmi_watchdog and hardlockup_panic sysctls. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths emulation library even if a 387 maths coprocessor is present. no4lvl [RISCV,EARLY] Disable 4-level and 5-level paging modes. Forces kernel to use 3-level paging instead. no5lvl [X86-64,RISCV,EARLY] Disable 5-level paging mode. Forces kernel to use 4-level paging instead. noalign [KNL,ARM] noaltinstr [S390,EARLY] Disables alternative instructions patching (CPU alternatives feature). noapic [SMP,APIC,EARLY] Tells the kernel to not make use of any IOAPICs that may be present in the system. noautogroup Disable scheduler automatic task group creation. nocache [ARM,EARLY] no_console_suspend [HW] Never suspend the console Disable suspending of consoles during suspend and hibernate operations. Once disabled, debugging messages can reach various consoles while the rest of the system is being put to sleep (ie, while debugging driver suspend/resume hooks). This may not work reliably with all consoles, but is known to work with serial and VGA consoles. To facilitate more flexible debugging, we also add console_suspend, a printk module parameter to control it. Users could use console_suspend (usually /sys/module/printk/parameters/console_suspend) to turn on/off it dynamically. no_debug_objects [KNL,EARLY] Disable object debugging nodsp [SH] Disable hardware DSP at boot time. noefi [EFI,EARLY] Disable EFI runtime services support. no_entry_flush [PPC,EARLY] Don't flush the L1-D cache when entering the kernel. noexec [IA-64] noexec32 [X86-64] This affects only 32-bit executables. noexec32=on: enable non-executable mappings (default) read doesn't imply executable mappings noexec32=off: disable non-executable mappings read implies executable mappings no_file_caps Tells the kernel not to honor file capabilities. The only way then for a file to be executed with privilege is to be setuid root or executed by root. nofpu [MIPS,SH] Disable hardware FPU at boot time. nofsgsbase [X86] Disables FSGSBASE instructions. nofxsr [BUGS=X86-32] Disables x86 floating point extended register save and restore. The kernel will only save legacy floating-point registers on task switch. nohalt [IA-64] Tells the kernel not to use the power saving function PAL_HALT_LIGHT when idle. This increases power-consumption. On the positive side, it reduces interrupt wake-up latency, which may improve performance in certain environments such as networked servers or real-time systems. no_hash_pointers [KNL,EARLY] Force pointers printed to the console or buffers to be unhashed. By default, when a pointer is printed via %p format string, that pointer is "hashed", i.e. obscured by hashing the pointer value. This is a security feature that hides actual kernel addresses from unprivileged users, but it also makes debugging the kernel more difficult since unequal pointers can no longer be compared. However, if this command-line option is specified, then all normal pointers will have their true value printed. This option should only be specified when debugging the kernel. Please do not use on production kernels. nohibernate [HIBERNATION] Disable hibernation and resume. nohlt [ARM,ARM64,MICROBLAZE,MIPS,PPC,SH] Forces the kernel to busy wait in do_idle() and not use the arch_cpu_idle() implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP to be effective. This is useful on platforms where the sleep(SH) or wfi(ARM,ARM64) instructions do not work correctly or when doing power measurements to evaluate the impact of the sleep instructions. This is also useful when using JTAG debugger. nohugeiomap [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings. nohugevmalloc [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings. nohz= [KNL] Boottime enable/disable dynamic ticks Valid arguments: on, off Default: on nohz_full= [KNL,BOOT,SMP,ISOL] The argument is a cpu list, as described above. In kernels built with CONFIG_NO_HZ_FULL=y, set the specified list of CPUs whose tick will be stopped whenever possible. The boot CPU will be forced outside the range to maintain the timekeeping. Any CPUs in this list will have their RCU callbacks offloaded, just as if they had also been called out in the rcu_nocbs= boot parameter. Note that this argument takes precedence over the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option. noinitrd [RAM] Tells the kernel not to load any configured initial RAM disk. nointremap [X86-64,Intel-IOMMU,EARLY] Do not enable interrupt remapping. [Deprecated - use intremap=off] nointroute [IA-64] noinvpcid [X86,EARLY] Disable the INVPCID cpu feature. noiotrap [SH] Disables trapped I/O port accesses. noirqdebug [X86-32] Disables the code which attempts to detect and disable unhandled interrupt sources. noisapnp [ISAPNP] Disables ISA PnP code. nojitter [IA-64] Disables jitter checking for ITC timers. nokaslr [KNL,EARLY] When CONFIG_RANDOMIZE_BASE is set, this disables kernel and module base offset ASLR (Address Space Layout Randomization). no-kvmapf [X86,KVM,EARLY] Disable paravirtualized asynchronous page fault handling. no-kvmclock [X86,KVM,EARLY] Disable paravirtualized KVM clock driver nolapic [X86-32,APIC,EARLY] Do not enable or use the local APIC. nolapic_timer [X86-32,APIC,EARLY] Do not use the local APIC timer. nomca [IA-64] Disable machine check abort handling nomce [X86-32] Disable Machine Check Exception nomfgpt [X86-32] Disable Multi-Function General Purpose Timer usage (for AMD Geode machines). nomodeset Disable kernel modesetting. Most systems' firmware sets up a display mode and provides framebuffer memory for output. With nomodeset, DRM and fbdev drivers will not load if they could possibly displace the pre- initialized output. Only the system framebuffer will be available for use. The respective drivers will not perform display-mode changes or accelerated rendering. Useful as error fallback, or for testing and debugging. nomodule Disable module load nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to shutdown the other cpus. Instead use the REBOOT_VECTOR irq. nopat [X86,EARLY] Disable PAT (page attribute table extension of pagetables) support. nopcid [X86-64,EARLY] Disable the PCID cpu feature. nopku [X86] Disable Memory Protection Keys CPU feature found in some Intel CPUs. nopti [X86-64,EARLY] Equivalent to pti=off nopv= [X86,XEN,KVM,HYPER_V,VMWARE,EARLY] Disables the PV optimizations forcing the guest to run as generic guest with no PV drivers. Currently support XEN HVM, KVM, HYPER_V and VMWARE guest. nopvspin [X86,XEN,KVM,EARLY] Disables the qspinlock slow path using PV optimizations which allow the hypervisor to 'idle' the guest on lock contention. norandmaps Don't use address space randomization. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space noreplace-smp [X86-32,SMP] Don't replace SMP instructions with UP alternatives noresume [SWSUSP] Disables resume and restores original swap space. nosbagart [IA-64] no-scroll [VGA] Disables scrollback. This is required for the Braillex ib80-piezo Braille reader made by F.H. Papenmeier (Germany). nosgx [X86-64,SGX,EARLY] Disables Intel SGX kernel support. nosmap [PPC,EARLY] Disable SMAP (Supervisor Mode Access Prevention) even if it is supported by processor. nosmep [PPC64s,EARLY] Disable SMEP (Supervisor Mode Execution Prevention) even if it is supported by processor. nosmp [SMP,EARLY] Tells an SMP kernel to act as a UP kernel, and disable the IO APIC. legacy for "maxcpus=0". nosmt [KNL,MIPS,PPC,S390,EARLY] Disable symmetric multithreading (SMT). Equivalent to smt=1. [KNL,X86,PPC] Disable symmetric multithreading (SMT). nosmt=force: Force disable SMT, cannot be undone via the sysfs control file. nosoftlockup [KNL] Disable the soft-lockup detector. nospec_store_bypass_disable [HW,EARLY] Disable all mitigations for the Speculative Store Bypass vulnerability nospectre_bhb [ARM64,EARLY] Disable all mitigations for Spectre-BHB (branch history injection) vulnerability. System may allow data leaks with this option. nospectre_v1 [X86,PPC,EARLY] Disable mitigations for Spectre Variant 1 (bounds check bypass). With this option data leaks are possible in the system. nospectre_v2 [X86,PPC_E500,ARM64,EARLY] Disable all mitigations for the Spectre variant 2 (indirect branch prediction) vulnerability. System may allow data leaks with this option. no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,EARLY] Disable paravirtualized steal time accounting. steal time is computed, but won't influence scheduler behaviour nosync [HW,M68K] Disables sync negotiation for all devices. no_timer_check [X86,APIC] Disables the code which tests for broken timer IRQ sources. no_uaccess_flush [PPC,EARLY] Don't flush the L1-D cache after accessing user data. novmcoredd [KNL,KDUMP] Disable device dump. Device dump allows drivers to append dump data to vmcore so you can collect driver specified debug info. Drivers can append the data without any limit and this data is stored in memory, so this may cause significant memory stress. Disabling device dump can help save memory but the driver debug data will be no longer available. This parameter is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP is set. no-vmw-sched-clock [X86,PV_OPS,EARLY] Disable paravirtualized VMware scheduler clock and use the default one. nowatchdog [KNL] Disable both lockup detectors, i.e. soft-lockup and NMI watchdog (hard-lockup). nowb [ARM,EARLY] nox2apic [X86-64,APIC,EARLY] Do not enable x2APIC mode. NOTE: this parameter will be ignored on systems with the LEGACY_XAPIC_DISABLED bit set in the IA32_XAPIC_DISABLE_STATUS MSR. noxsave [BUGS=X86] Disables x86 extended register state save and restore using xsave. The kernel will fallback to enabling legacy floating-point and sse state. noxsaveopt [X86] Disables xsaveopt used in saving x86 extended register states. The kernel will fall back to use xsave to save the states. By using this parameter, performance of saving the states is degraded because xsave doesn't support modified optimization while xsaveopt supports it on xsaveopt enabled systems. noxsaves [X86] Disables xsaves and xrstors used in saving and restoring x86 extended register state in compacted form of xsave area. The kernel will fall back to use xsaveopt and xrstor to save and restore the states in standard form of xsave area. By using this parameter, xsave area per process might occupy more memory on xsaves enabled systems. nps_mtm_hs_ctr= [KNL,ARC] This parameter sets the maximum duration, in cycles, each HW thread of the CTOP can run without interruptions, before HW switches it. The actual maximum duration is 16 times this parameter's value. Format: integer between 1 and 255 Default: 255 nptcg= [IA-64] Override max number of concurrent global TLB purges which is reported from either PAL_VM_SUMMARY or SAL PALO. nr_cpus= [SMP,EARLY] Maximum number of processors that an SMP kernel could support. nr_cpus=n : n >= 1 limits the kernel to support 'n' processors. It could be larger than the number of already plugged CPU during bootup, later in runtime you can physically add extra cpu until it reaches n. So during boot up some boot time memory for per-cpu variables need be pre-allocated for later physical cpu hot plugging. nr_uarts= [SERIAL] maximum number of UARTs to be registered. numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86, EARLY] Disable NUMA, Only set up a single NUMA node spanning all memory. numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic NUMA balancing. Allowed values are enable and disable numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 'node', 'default' can be specified This can be set from sysctl after boot. See Documentation/admin-guide/sysctl/vm.rst for details. ohci1394_dma=early [HW,EARLY] enable debugging via the ohci1394 driver. See Documentation/core-api/debugging-via-ohci1394.rst for more info. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands Rather than timing out after 20 ms if an EC command is not properly ACKed, override the length of the timeout. We have interrupts disabled while waiting for the ACK, so if this is set too high interrupts *may* be lost! omap_mux= [OMAP] Override bootloader pin multiplexing. Format: ... For example, to override I2C bus2: omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] boundary - index of last SLC block on Flex-OneNAND. The remaining blocks are configured as MLC blocks. lock - Configure if Flex-OneNAND boundary should be locked. Once locked, the boundary cannot be changed. 1 indicates lock status, 0 indicates unlock status. oops=panic [KNL,EARLY] Always panic on oopses. Default is to just kill the process, but there is a small probability of deadlocking the machine. This will also cause panics on machine check exceptions. Useful together with panic=30 to trigger a reboot. page_alloc.shuffle= [KNL] Boolean flag to control whether the page allocator should randomize its free lists. The randomization may be automatically enabled if the kernel detects it is running on a platform with a direct-mapped memory-side cache, and this parameter can be used to override/disable that behavior. The state of the flag can be read from sysfs at: /sys/module/page_alloc/parameters/shuffle. page_owner= [KNL,EARLY] Boot-time page_owner enabling option. Storage of the information about who allocated each page is disabled in default. With this switch, we can turn it on. on: enable the feature page_poison= [KNL,EARLY] Boot-time parameter changing the state of poisoning on the buddy allocator, available with CONFIG_PAGE_POISONING=y. off: turn off poisoning (default) on: turn on poisoning page_reporting.page_reporting_order= [KNL] Minimal page reporting order Format:  Adjust the minimal page reporting order. The page reporting is disabled when it exceeds MAX_PAGE_ORDER. panic= [KNL] Kernel behaviour on panic: delay  timeout > 0: seconds before rebooting timeout = 0: wait forever timeout < 0: reboot immediately Format:  panic_on_taint= [KNL,EARLY] Bitmask for conditionally calling panic() in add_taint() Format: [,nousertaint] Hexadecimal bitmask representing the set of TAINT flags that will cause the kernel to panic when add_taint() is called with any of the flags in this set. The optional switch "nousertaint" can be utilized to prevent userspace forced crashes by writing to sysctl /proc/sys/kernel/tainted any flagset matching with the bitmask set on panic_on_taint. See Documentation/admin-guide/tainted-kernels.rst for extra details on the taint flags that users can pick to compose the bitmask to assign to panic_on_taint. panic_on_warn=1 panic() instead of WARN(). Useful to cause kdump on a WARN(). panic_print= Bitmask for printing system info when panic happens. User can chose combination of the following bits: bit 0: print all tasks info bit 1: print system memory info bit 2: print timer info bit 3: print locks info if CONFIG_LOCKDEP is on bit 4: print ftrace buffer bit 5: print all printk messages in buffer bit 6: print all CPUs backtrace (if available in the arch) bit 7: print only tasks in uninterruptible (blocked) state *Be aware* that this option may print a _lot_ of lines, so there are risks of losing older messages in the log. Use this option carefully, maybe worth to setup a bigger log buffer with "log_buf_len" along with this. parkbd.port= [HW] Parallel port number the keyboard adapter is connected to, default is 0. Format:  parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 0 for XT, 1 for AT (default is AT). Format:  parport= [HW,PPT] Specify parallel ports. 0 disables. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } Use 'auto' to force the driver to use any IRQ/DMA settings detected (the default is to ignore detected IRQ/DMA settings because of possible conflicts). You can specify the base address, IRQ, and DMA settings; IRQ and DMA should be numbers, or 'auto' (for using detected settings on that particular port), or 'nofifo' (to avoid using a FIFO even if it is detected). Parallel ports are assigned in the order they are specified on the command line, starting with parport0. parport_init_mode= [HW,PPT] Configure VIA parallel port to operate in a specific mode. This is necessary on Pegasos computer where firmware has no options for setting up parallel port mode and sets it to spp. Currently this function knows 686a and 8231 chips. Format: [spp|ps2|epp|ecp|ecpepp] pata_legacy.all= [HW,LIBATA] Format:  Set to non-zero to probe primary and secondary ISA port ranges on PCI systems where no PCI PATA device has been found at either range. Disabled by default. pata_legacy.autospeed= [HW,LIBATA] Format:  Set to non-zero if a chip is present that snoops speed changes. Disabled by default. pata_legacy.ht6560a= [HW,LIBATA] Format:  Set to 1, 2, or 3 for HT 6560A on the primary channel, the secondary channel, or both channels respectively. Disabled by default. pata_legacy.ht6560b= [HW,LIBATA] Format:  Set to 1, 2, or 3 for HT 6560B on the primary channel, the secondary channel, or both channels respectively. Disabled by default. pata_legacy.iordy_mask= [HW,LIBATA] Format:  IORDY enable mask. Set individual bits to allow IORDY for the respective channel. Bit 0 is for the first legacy channel handled by this driver, bit 1 is for the second channel, and so on. The sequence will often correspond to the primary legacy channel, the secondary legacy channel, and so on, but the handling of a PCI bus and the use of other driver options may interfere with the sequence. By default IORDY is allowed across all channels. pata_legacy.opti82c46x= [HW,LIBATA] Format:  Set to 1, 2, or 3 for Opti 82c611A on the primary channel, the secondary channel, or both channels respectively. Disabled by default. pata_legacy.opti82c611a= [HW,LIBATA] Format:  Set to 1, 2, or 3 for Opti 82c465MV on the primary channel, the secondary channel, or both channels respectively. Disabled by default. pata_legacy.pio_mask= [HW,LIBATA] Format:  PIO mode mask for autospeed devices. Set individual bits to allow the use of the respective PIO modes. Bit 0 is for mode 0, bit 1 is for mode 1, and so on. All modes allowed by default. pata_legacy.probe_all= [HW,LIBATA] Format:  Set to non-zero to probe tertiary and further ISA port ranges on PCI systems. Disabled by default. pata_legacy.probe_mask= [HW,LIBATA] Format:  Probe mask for legacy ISA PATA ports. Depending on platform configuration and the use of other driver options up to 6 legacy ports are supported: 0x1f0, 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing of individual ports can be disabled by setting the corresponding bits in the mask to 1. Bit 0 is for the first port in the list above (0x1f0), and so on. By default all supported ports are probed. pata_legacy.qdi= [HW,LIBATA] Format:  Set to non-zero to probe QDI controllers. By default set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise. pata_legacy.winbond= [HW,LIBATA] Format:  Set to non-zero to probe Winbond controllers. Use the standard I/O port (0x130) if 1, otherwise the value given is the I/O port to use (typically 0x1b0). By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE, 0 otherwise. pata_platform.pio_mask= [HW,LIBATA] Format:  Supported PIO mode mask. Set individual bits to allow the use of the respective PIO modes. Bit 0 is for mode 0, bit 1 is for mode 1, and so on. Mode 0 only allowed by default. pause_on_oops= Halt all CPUs after the first oops has been printed for the specified number of seconds. This is to be used if your oopses keep scrolling off the screen. pcbit= [HW,ISDN] pci=option[,option...] [PCI,EARLY] various PCI subsystem options. Some options herein operate on a specific device or a set of devices (). These are specified in one of the following formats: [:]:.[/.]* pci::[::] Note: the first format specifies a PCI bus/device/function address which may change if new hardware is inserted, if motherboard firmware changes, or due to changes caused by other kernel parameters. If the domain is left unspecified, it is taken to be zero. Optionally, a path to a device through multiple device/function addresses can be specified after the base address (this is more robust against renumbering issues). The second format selects devices using IDs from the configuration space which may match multiple devices in the system. earlydump dump PCI config space before the kernel changes anything off [X86] don't probe for the PCI bus bios [X86-32] force use of PCI BIOS, don't access the hardware directly. Use this if your machine has a non-standard PCI host bridge. nobios [X86-32] disallow use of PCI BIOS, only direct hardware access methods are allowed. Use this if you experience crashes upon bootup and you suspect they are caused by the BIOS. conf1 [X86] Force use of PCI Configuration Access Mechanism 1 (config address in IO port 0xCF8, data in IO port 0xCFC, both 32-bit). conf2 [X86] Force use of PCI Configuration Access Mechanism 2 (IO port 0xCF8 is an 8-bit port for the function, IO port 0xCFA, also 8-bit, sets bus number. The config space is then accessed through ports 0xC000-0xCFFF). See http://wiki.osdev.org/PCI for more info on the configuration access mechanisms. noaer [PCIE] If the PCIEAER kernel config parameter is enabled, this kernel boot option can be used to disable the use of PCIE advanced error reporting. nodomains [PCI] Disable support for multiple PCI root domains (aka PCI segments, in ACPI-speak). nommconf [X86] Disable use of MMCONFIG for PCI Configuration check_enable_amd_mmconf [X86] check for and enable properly configured MMIO access to PCI config space on AMD family 10h CPU nomsi [MSI] If the PCI_MSI kernel config parameter is enabled, this kernel boot option can be used to disable the use of MSI interrupts system-wide. noioapicquirk [APIC] Disable all boot interrupt quirks. Safety option to keep boot IRQs enabled. This should never be necessary. ioapicreroute [APIC] Enable rerouting of boot IRQs to the primary IO-APIC for bridges that cannot disable boot IRQs. This fixes a source of spurious IRQs when the system masks IRQs. noioapicreroute [APIC] Disable workaround that uses the boot IRQ equivalent of an IRQ that connects to a chipset where boot IRQs cannot be disabled. The opposite of ioapicreroute. biosirq [X86-32] Use PCI BIOS calls to get the interrupt routing table. These calls are known to be buggy on several machines and they hang the machine when used, but on other computers it's the only way to get the interrupt routing table. Try this option if the kernel is unable to allocate IRQs or discover secondary PCI buses on your motherboard. rom [X86] Assign address space to expansion ROMs. Use with caution as certain devices share address decoders between ROMs and other resources. norom [X86] Do not assign address space to expansion ROMs that do not already have BIOS assigned address ranges. nobar [X86] Do not assign address space to the BARs that weren't assigned by the BIOS. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be assigned automatically to PCI devices. You can make the kernel exclude IRQs of your ISA cards this way. pirqaddr=0xAAAAA [X86] Specify the physical address of the PIRQ table (normally generated by the BIOS) if it is outside the F0000h-100000h range. lastbus=N [X86] Scan all buses thru bus #N. Can be useful if the kernel is unable to find your secondary buses and you want to tell it explicitly which ones they are. assign-busses [X86] Always assign all PCI bus numbers ourselves, overriding whatever the firmware may have done. usepirqmask [X86] Honor the possible IRQ mask stored in the BIOS $PIR table. This is needed on some systems with broken BIOSes, notably some HP Pavilion N5400 and Omnibook XE3 notebooks. This will have no effect if ACPI IRQ routing is enabled. noacpi [X86] Do not use ACPI for IRQ routing or for PCI scanning. use_crs [X86] Use PCI host bridge window information from ACPI. On BIOSes from 2008 or later, this is enabled by default. If you need to use this, please report a bug. nocrs [X86] Ignore PCI host bridge windows from ACPI. If you need to use this, please report a bug. use_e820 [X86] Use E820 reservations to exclude parts of PCI host bridge windows. This is a workaround for BIOS defects in host bridge _CRS methods. If you need to use this, please report a bug to