Documentation/admin-guide/kernel-parameters.txt

acpi=		[HW,ACPI,X86,ARM64,RISCV64]
		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]
		Format: <int>
		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
		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: <int>
		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]
		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: <irq>,<irq>...

acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
		use by PCI
		Format: <irq>,<irq>...

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: <byte> or <bitmap-list>

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]
		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]
		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] ACPI System Control Interrupt trigger mode
		Format: { level | edge | high | low }

acpi_skip_timer_override [HW,ACPI]
		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]
		Use timer override. For some broken Nvidia NF5 boards
		that require a timer override, but don't have HPET

add_efi_memmap	[EFI; X86] 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]
		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]
		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.

amijoy.map=	[HW,JOY] Amiga joystick support
		Map of devices attached to JOY0DAT and JOY1DAT
		Format: <a>,<b>
		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: <type1>,<type2>,..<type16>

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] 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] 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: <io>,<irq>,<nodeID>

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: <int> (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: <bool> (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: <int> (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: <io>,<mode>

baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
		Format: <io>,<mode>
		See header of drivers/net/hamradio/baycom_par.c.

baycom_ser_fdx=	[HW,AX25]
		BayCom Serial Port AX.25 Modem (Full Duplex Mode)
		Format: <io>,<irq>,<mode>[,<baud>]
		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: <io>,<irq>,<mode>
		See header of drivers/net/hamradio/baycom_ser_hdx.c.

bert_disable	[ACPI]
		Disable BERT OS support on buggy BIOSes.

bgrt_disable	[ACPI][X86]
		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=	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]
		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:<keyid> | builtin }

cca=		[MIPS] 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.memory=	[KNL] Pass options to the cgroup memory controller.
		Format: <string>
		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: <string>
		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]
		Format: <bool>
		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.max_cswd_read_retries= [KNL]
		Number of clocksource_watchdog() retries due to
		external delays before the clock will be marked
		unstable.  Defaults to two retries, that is,
		three attempts to read the clock under test.

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]
		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]
		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=<node>:nn[MG][,<node>:nn[MG]]
		[KNL,CMA]
		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]
		Sets the size of memory pool for coherent, atomic dma
		allocations, by default set to 256K.

com20020=	[HW,NET] ARCnet - COM20020 chipset
		Format:
		<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]

com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
		Format: <io>[,<irq>]

com90xx=	[HW,NET]
		ARCnet - COM90xx chipset (memory-mapped buffers)
		Format: <io>[,<irq>[,<memstart>]]

condev=		[HW,S390] console device
conmode=

con3215_drop=	[S390] 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<n>	Use the virtual console device <n>.

	ttyS<n>[,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,<addr>[,options]
	uart[8250],mmio,<addr>[,options]
	uart[8250],mmio16,<addr>[,options]
	uart[8250],mmio32,<addr>[,options]
	uart[8250],0x<addr>[,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], <addr> 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<n>	Use the hypervisor console device <n>. 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/<pid>/coredump_filter.
		See also Documentation/filesystems/proc.rst.

coresight_cpu_debug.enable
		[ARM,ARM64]
		Format: <bool>
		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:
		<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]

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] 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: <bool>
		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] 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] 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] 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] 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
		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: <dma>

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: <port#>,<type>
		See also Documentation/input/devices/joystick-parport.rst

debug		[KNL] Enable kernel debugging (events log level).

debug_boot_weak_hash
		[KNL] 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: <int>
		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] Enable object debugging

debug_guardpage_minorder=
		[KNL] 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_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] 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] 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]
		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]
		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_cpu_apicid= [X86,APIC,SMP]
		Format: <int>
		The number of initial APIC ID for the
		corresponding CPU to be disabled at boot,
		mostly used for the kdump 2nd kernel to
		disable BSP to wake up multiple CPUs without
		causing system reset or hang due to sending
		INIT from AP to BSP.

disable_ddw	[PPC/PSERIES]
		Disable Dynamic DMA Window support. Use this
		to workaround buggy firmware.

disable_ipv6=	[IPV6]
		See Documentation/networking/ipv6.rst.

disable_mtrr_cleanup [X86]
		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]
		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]
		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=<number>
		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=<driver_name>
		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.

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: <driver_name1>,<driver_name2>...

drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
		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.
		Generic built-in EDID data sets are used, if one of
		edid/1024x768.bin, edid/1280x1024.bin,
		edid/1680x1050.bin, or edid/1920x1080.bin is given
		and no file with the same name exists. Details and
		instructions how to build your own EDID data are
		available in Documentation/admin-guide/edid.rst. 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]
		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]
<module>.dyndbg[="val"]
		Enable debug messages at boot time.  See
		Documentation/admin-guide/dynamic-debug-howto.rst
		for details.

early_ioremap_debug [KNL]
		Enable debug messages in early_ioremap support. This
		is useful for tracking down temporary early mappings
		which are not unmapped.

earlycon=	[KNL] 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,<addr>[,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,<addr>[,options[,uartclk]]
	uart[8250],mmio,<addr>[,options[,uartclk]]
	uart[8250],mmio32,<addr>[,options[,uartclk]]
	uart[8250],mmio32be,<addr>[,options[,uartclk]]
	uart[8250],0x<addr>[,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], <addr> is assumed
		to be equivalent to 'mmio'. 'options' are specified
		in the same format described for "console=ttyS<n>"; if
		unspecified, the h/w is not initialized. 'uartclk' is
		the uart clock frequency; if unspecified, it is set
		to 'BASE_BAUD' * 16.

	pl011,<addr>
	pl011,mmio32,<addr>
		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,<addr>
		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,<addr>
		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,<addr>
		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,<addr>
		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,<addr>
		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,<addr>
		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,<addr>
	s3c2412,<addr>
	s3c2440,<addr>
	s3c6400,<addr>
	s5pv210,<addr>
	exynos4210,<addr>
		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,<addr>
		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,<addr>
	lpuart32,<addr>
		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,<addr>
	ec_imx6q,<addr>
		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,<addr>
		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,<addr>
		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,<addr>
		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]
		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 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 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]
		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]
		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]
		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] 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] [IA64,PPC,SH,X86,S390]
		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]
		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] 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: <interval>,<probability>,<space>,<times>
		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.

force_pal_cache_flush
		[IA-64] Avoid check_sal_cache_flush which may hang on
		buggy SAL_CACHE_FLUSH implementations. Using this
		parameter will force ia64_sal_cache_flush to call
		ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.

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.

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[=orig_cpu]
		[FTRACE] will dump the trace buffers on oops.
		If no parameter is passed, ftrace will dump
		buffers of all CPUs, but if you pass orig_cpu, it will
		dump only the buffer of the 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=<uint>
		[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] 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=<bool>
		[KNL] Treat all inferred dependencies as mandatory
		dependencies. This only applies for fw_devlink=on|rpm.
		Format: <bool>

fw_devlink.sync_state =
		[KNL] 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: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
		See also Documentation/input/devices/joystick-parport.rst

gamma=		[HW,DRM]

gart_fix_e820=	[X86-64] disable the fix e820 for K8 GART
		Format: off | on
		default: on

gather_data_sampling=
		[X86,INTEL] 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: <start1>,<end1>,<start2>,<end2>...
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: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
		Default: 1024
grcan.rxsize=	[HW] Sets the size of the rx buffer.
		Format: <unsigned int> 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: <cyl>,<head>,<sect>

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).

highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
		size of <nn>. 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] Set the hostname (aka UTS nodename).
		Format: <string>
		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: <integer> or (node format)
			<node>:<integer>[,<node>:<integer>]

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] 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)
			<node>:nn[KMGTPE][,<node>: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] 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:
			<bus_id>,<clkrate>

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

icn=		[HW,ISDN]
		Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]


idle=		[X86]
		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: <bool>
		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: <bool>
		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]
		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: <min_file_size>
		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: <bufsize>
		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: <full_path>
		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: <bool>
		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] Specify the location of the initial ramdisk

initrdmem=	[KNL] 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] 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] 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: <irq>

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]
		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]
		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]
	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] 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] 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] 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] 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] 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]
		Format: <bool>
		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]
		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]
		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: <RDP>,<reset>,<pci_scan>,<verbosity>

isolcpus=	[KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
		[Deprecated - use cpusets instead]
		Format: [flag-list,]<cpu-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.
		  <cpu number> 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 <cpu-list> 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]
		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]

kernelcore=	[KNL,X86,IA-64,PPC]
		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] kgdb over EHCI usb debug port.
		Format: <Controller#>[,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: <serial_device>[,baud]
		 keyboard only format: kbd
		 keyboard and serial format: kbd,<serial_device>[,baud]
		Optional Kernel mode setting:
		 kms, kbd format: kms,kbd
		 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]

kgdboc_earlycon=	[KGDB,HW]
		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] 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] 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] 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] 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] Trap guest accesses to GICv3 group-0
		system registers

kvm-arm.vgic_v3_group1_trap=
		[KVM,ARM] Trap guest accesses to GICv3 group-1
		system registers

kvm-arm.vgic_v3_common_trap=
		[KVM,ARM] Trap guest accesses to GICv3 common
		system registers

kvm-arm.vgic_v4_enable=
		[KVM,ARM] Allow use of GICv4 for direct injection of
		LPIs.

kvm_cma_resv_ratio=n [PPC]
		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: <integer>
		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]
		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] 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] 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] 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: <int>

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: <integer>

lockd.nlm_tcpport=N	[NFS] Assign TCP port.
		Format: <integer>

lockd.nlm_timeout=T	[NFS] Assign timeout value.
		Format: <integer>

lockd.nlm_udpport=M	[NFS] Assign UDP port.
		Format: <integer>

lockdown=	[SECURITY]
		{ 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.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.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.writer_fifo= [KNL]
		Run the write-side locktorture kthreads at
		sched_set_fifo() real-time priority.

locktorture.verbose= [KNL]
		Enable additional printk() statements.

logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
		Format: <irq>

loglevel=	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]	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: <io>,<irq>,<dma>

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] 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: <first>,<last>
		Specifies range of consoles to be captured by the MDA.

mds=		[X86,INTEL]
		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] Set the memory size.
		Must be specified, otherwise memory size will be 0.

mem=nn[KMG]	[KNL,BOOT] 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] - 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] 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] 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] 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] 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] 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]
		[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=<size>%<offset>-<oldtype>+<newtype>
		[KNL,ACPI] Convert memory within the specified region
		from <oldtype> to <newtype>. If "-<oldtype>" is left
		out, the whole region will be marked as <newtype>,
		even if previously unavailable. If "+<newtype>" 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]
		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]
		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]
		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] Enable memtest
		Format: <integer>
		default : 0 <disable>
		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 (depends on kernel configuration option):
		  on  (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
		  off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
		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.

mem.devmem=	Activate the /dev/mem device
		Format: <bool>  (1/Y/y=enable, 0/N/n=disable)

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]

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] 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.

		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]
				       retbleed=off [X86]
				       spec_store_bypass_disable=off [X86,PPC]
				       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] 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] 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

<module>.async_probe[=<bool>] [KNL]
		If no <bool> value is specified or if the value
		specified is not a valid <bool>, enable asynchronous
		probe on this module.  Otherwise, enable/disable
		asynchronous probe on this module as indicated by the
		<bool> value. See also: module.async_probe

module.async_probe=<bool>
		[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 <module>.async_probe. When both
		module.async_probe and <module>.async_probe are
		specified, <module>.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: <msecs>
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]
		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] 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: <name>,<region-number>,<size>,<offset>

MTD_Region=	[MTD] Format:
		<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]

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]
		Enable printing debug information related to MTRR
		registers at boot time.

mtrr_chunk_size=nn[KMG] [X86]
		used for mtrr cleanup. It is largest continuous chunk
		that could hold holes aka. UC entries.

mtrr_gran_size=nn[KMG] [X86]
		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]
		Format: <integer>
		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: <irq>,<io>,<mem_start>,<mem_end>,<name>
		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.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] Disable 4-level and 5-level paging modes. Forces
		kernel to use 3-level paging instead.

no5lvl		[X86-64,RISCV] Disable 5-level paging mode. Forces
		kernel to use 4-level paging instead.

noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
		caches in the slab allocator.  Saves per-node memory,
		but will impact performance.

noalign		[KNL,ARM]

noaltinstr	[S390] Disables alternative instructions patching
		(CPU alternatives feature).

noapic		[SMP,APIC] 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]

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] Disable object debugging

nodsp		[SH] Disable hardware DSP at boot time.

noefi		Disable EFI runtime services support.

no_entry_flush  [PPC] 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
		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] Disable kernel huge I/O mappings.

nohugevmalloc	[KNL,X86,PPC,ARM64] 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] Do not enable interrupt
		remapping.
		[Deprecated - use intremap=off]

nointroute	[IA-64]

noinvpcid	[X86] 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]
		When CONFIG_RANDOMIZE_BASE is set, this disables
		kernel and module base offset ASLR (Address Space
		Layout Randomization).

no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
		fault handling.

no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver

nolapic		[X86-32,APIC] Do not enable or use the local APIC.

nolapic_timer	[X86-32,APIC] 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] Disable PAT (page attribute table extension of
		pagetables) support.

nopcid		[X86-64] Disable the PCID cpu feature.

nopku		[X86] Disable Memory Protection Keys CPU feature found
		in some Intel CPUs.

nopti		[X86-64]
		Equivalent to pti=off

nopv=		[X86,XEN,KVM,HYPER_V,VMWARE]
		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]
		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] Disables Intel SGX kernel support.

nosmap		[PPC]
		Disable SMAP (Supervisor Mode Access Prevention)
		even if it is supported by processor.

nosmep		[PPC64s]
		Disable SMEP (Supervisor Mode Execution Prevention)
		even if it is supported by processor.

nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
		and disable the IO APIC.  legacy for "maxcpus=0".

nosmt		[KNL,MIPS,PPC,S390] 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] Disable all mitigations for the Speculative Store Bypass vulnerability

nospectre_bhb	[ARM64] Disable all mitigations for Spectre-BHB (branch
		history injection) vulnerability. System may allow data leaks
		with this option.

nospectre_v1	[X86,PPC] 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] 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] 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] 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] 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]

nox2apic	[X86-64,APIC] 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] 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] 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] 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: <mux_mode0.mode_name=value>...
		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	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] 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] 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: <integer>
		Adjust the minimal page reporting order. The page
		reporting is disabled when it exceeds MAX_ORDER.

panic=		[KNL] Kernel behaviour on panic: delay <timeout>
		timeout > 0: seconds before rebooting
		timeout = 0: wait forever
		timeout < 0: reboot immediately
		Format: <timeout>

panic_on_taint=	Bitmask for conditionally calling panic() in add_taint()
		Format: <hex>[,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)
		*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: <parport#>
parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
		0 for XT, 1 for AT (default is AT).
		Format: <mode>

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: <int>
		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: <int>
		Set to non-zero if a chip is present that snoops speed
		changes.  Disabled by default.

pata_legacy.ht6560a=	[HW,LIBATA]
		Format: <int>
		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: <int>
		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: <int>
		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: <int>
		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: <int>
		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: <int>
		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: <int>
		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: <int>
		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: <int>
		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: <int>
		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: <int>
		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=<int>
		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] various PCI subsystem options.

			Some options herein operate on a specific device
			or a set of devices (<pci_dev>). These are
			specified in one of the following formats:

			[<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
			pci:<vendor>:<device>[:<subvendor>:<subdevice>]

			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
			<linux-pci@vger.kernel.org>.
	no_e820		[X86] Ignore E820 reservations for PCI host
			bridge windows. This is the default on modern
			hardware. If you need to use this, please report
			a bug to <linux-pci@vger.kernel.org>.
	routeirq	Do IRQ routing for all PCI devices.
			This is normally done in pci_enable_device(),
			so this option is a temporary workaround
			for broken drivers that don't call it.
	skip_isa_align	[X86] do not align io start addr, so can
			handle more pci cards
	noearly		[X86] Don't do any early type 1 scanning.
			This might help on some broken boards which
			machine check when some devices' config space
			is read. But various workarounds are disabled
			and some IOMMU drivers will not work.
	bfsort		Sort PCI devices into breadth-first order.
			This sorting is done to get a device
			order compatible with older (<= 2.4) kernels.
	nobfsort	Don't sort PCI devices into breadth-first order.
	pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
			tuning and use the BIOS-configured MPS defaults.
	pcie_bus_safe	Set every device's MPS to the largest value
			supported by all devices below the root complex.
	pcie_bus_perf	Set device MPS to the largest allowable MPS
			based on its parent bus. Also set MRRS (Max
			Read Request Size) to the largest supported
			value (no larger than the MPS that the device
			or bus can support) for best performance.
	pcie_bus_peer2peer	Set every device's MPS to 128B, which
			every device is guaranteed to support. This
			configuration allows peer-to-peer DMA between
			any pair of devices, possibly at the cost of
			reduced performance.  This also guarantees
			that hot-added devices will work.
	cbiosize=nn[KMG]	The fixed amount of bus space which is
			reserved for the CardBus bridge's IO window.
			The default value is 256 bytes.
	cbmemsize=nn[KMG]	The fixed amount of bus space which is
			reserved for the CardBus bridge's memory
			window. The default value is 64 megabytes.
	resource_alignment=
			Format:
			[<order of align>@]<pci_dev>[; ...]
			Specifies alignment and device to reassign
			aligned memory resources. How to
			specify the device is described above.
			If <order of align> is not specified,
			PAGE_SIZE is used as alignment.
			A PCI-PCI bridge can be specified if resource
			windows need to be expanded.
			To specify the alignment for several
			instances of a device, the PCI vendor,
			device, subvendor, and subdevice may be
			specified, e.g., 12@pci:8086:9c22:103c:198f
			for 4096-byte alignment.
	ecrc=		Enable/disable PCIe ECRC (transaction layer
			end-to-end CRC checking). Only effective if
			OS has native AER control (either granted by
			ACPI _OSC or forced via "pcie_ports=native")
			bios: Use BIOS/firmware settings. This is the
			the default.
			off: Turn ECRC off
			on: Turn ECRC on.
	hpiosize=nn[KMG]	The fixed amount of bus space which is
			reserved for hotplug bridge's IO window.
			Default size is 256 bytes.
	hpmmiosize=nn[KMG]	The fixed amount of bus space which is
			reserved for hotplug bridge's MMIO window.
			Default size is 2 megabytes.
	hpmmioprefsize=nn[KMG]	The fixed amount of bus space which is
			reserved for hotplug bridge's MMIO_PREF window.
			Default size is 2 megabytes.
	hpmemsize=nn[KMG]	The fixed amount of bus space which is
			reserved for hotplug bridge's MMIO and
			MMIO_PREF window.
			Default size is 2 megabytes.
	hpbussize=nn	The minimum amount of additional bus numbers
			reserved for buses below a hotplug bridge.
			Default is 1.
	realloc=	Enable/disable reallocating PCI bridge resources
			if allocations done by BIOS are too small to
			accommodate resources required by all child
			devices.
			off: Turn realloc off
			on: Turn realloc on
	realloc		same as realloc=on
	noari		do not use PCIe ARI.
	noats		[PCIE, Intel-IOMMU, AMD-IOMMU]
			do not use PCIe ATS (and IOMMU device IOTLB).
	pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
			only look for one device below a PCIe downstream
			port.
	big_root_window	Try to add a big 64bit memory window to the PCIe
			root complex on AMD CPUs. Some GFX hardware
			can resize a BAR to allow access to all VRAM.
			Adding the window is slightly risky (it may
			conflict with unreported devices), so this
			taints the kernel.
	disable_acs_redir=<pci_dev>[; ...]
			Specify one or more PCI devices (in the format
			specified above) separated by semicolons.
			Each device specified will have the PCI ACS
			redirect capabilities forced off which will
			allow P2P traffic between devices through
			bridges without forcing it upstream. Note:
			this removes isolation between devices and
			may put more devices in an IOMMU group.
	force_floating	[S390] Force usage of floating interrupts.
	nomio		[S390] Do not use MIO instructions.
	norid		[S390] ignore the RID field and force use of
			one PCI domain per PCI function

pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
		Management.
	off	Disable ASPM.
	force	Enable ASPM even on devices that claim not to support it.
		WARNING: Forcing ASPM on may cause system lockups.

pcie_ports=	[PCIE] PCIe port services handling:
	native	Use native PCIe services (PME, AER, DPC, PCIe hotplug)
		even if the platform doesn't give the OS permission to
		use them.  This may cause conflicts if the platform
		also tries to use these services.
	dpc-native	Use native PCIe service for DPC only.  May
			cause conflicts if firmware uses AER or DPC.
	compat	Disable native PCIe services (PME, AER, DPC, PCIe
		hotplug).

pcie_port_pm=	[PCIE] PCIe port power management handling:
	off	Disable power management of all PCIe ports
	force	Forcibly enable power management of all PCIe ports

pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
	nomsi	Do not use MSI for native PCIe PME signaling (this makes
		all PCIe root ports use INTx for all services).

pcmv=		[HW,PCMCIA] BadgePAD 4

pd_ignore_unused
		[PM]
		Keep all power-domains already enabled by bootloader on,
		even if no driver has claimed them. This is useful
		for debug and development, but should not be
		needed on a platform with proper driver support.

pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
		boot time.
		Format: { 0 | 1 }
		See arch/parisc/kernel/pdc_chassis.c

percpu_alloc=	Select which percpu first chunk allocator to use.
		Currently supported values are "embed" and "page".
		Archs may support subset or none of the	selections.
		See comments in mm/percpu.c for details on each
		allocator.  This parameter is primarily	for debugging
		and performance comparison.

pirq=		[SMP,APIC] Manual mp-table setup
		See Documentation/arch/x86/i386/IO-APIC.rst.

plip=		[PPT,NET] Parallel port network link
		Format: { parport<nr> | timid | 0 }
		See also Documentation/admin-guide/parport.rst.

pmtmr=		[X86] Manual setup of pmtmr I/O Port.
		Override pmtimer IOPort with a hex value.
		e.g. pmtmr=0x508

pmu_override=	[PPC] Override the PMU.
		This option takes over the PMU facility, so it is no
		longer usable by perf. Setting this option starts the
		PMU counters by setting MMCR0 to 0 (the FC bit is
		cleared). If a number is given, then MMCR1 is set to
		that number, otherwise (e.g., 'pmu_override=on'), MMCR1
		remains 0.

pm_debug_messages	[SUSPEND,KNL]
		Enable suspend/resume debug messages during boot up.

pnp.debug=1	[PNP]
		Enable PNP debug messages (depends on the
		CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
		via /sys/module/pnp/parameters/debug.  We always show
		current resource usage; turning this on also shows
		possible settings and some assignment information.

pnpacpi=	[ACPI]
		{ off }

pnpbios=	[ISAPNP]
		{ on | off | curr | res | no-curr | no-res }

pnp_reserve_irq=
		[ISAPNP] Exclude IRQs for the autoconfiguration

pnp_reserve_dma=
		[ISAPNP] Exclude DMAs for the autoconfiguration

pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
		Ranges are in pairs (I/O port base and size).

pnp_reserve_mem=
		[ISAPNP] Exclude memory regions for the
		autoconfiguration.
		Ranges are in pairs (memory base and size).

ports=		[IP_VS_FTP] IPVS ftp helper module
		Default is 21.
		Up to 8 (IP_VS_APP_MAX_PORTS) ports
		may be specified.
		Format: <port>,<port>....

powersave=off	[PPC] This option disables power saving features.
		It specifically disables cpuidle and sets the
		platform machine description specific power_save
		function to NULL. On Idle the CPU just reduces
		execution priority.

ppc_strict_facility_enable
		[PPC] This option catches any kernel floating point,
		Altivec, VSX and SPE outside of regions specifically
		allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
		There is some performance impact when enabling this.

ppc_tm=		[PPC]
		Format: {"off"}
		Disable Hardware Transactional Memory

preempt=	[KNL]
		Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
		none - Limited to cond_resched() calls
		voluntary - Limited to cond_resched() and might_sleep() calls
		full - Any section that isn't explicitly preempt disabled
		       can be preempted anytime.

print-fatal-signals=
		[KNL] debug: print fatal signals

		If enabled, warn about various signal handling
		related application anomalies: too many signals,
		too many POSIX.1 timers, fatal signals causing a
		coredump - etc.

		If you hit the warning due to signal overflow,
		you might want to try "ulimit -i unlimited".

		default: off.

printk.always_kmsg_dump=
		Trigger kmsg_dump for cases other than kernel oops or
		panics
		Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
		default: disabled

printk.console_no_auto_verbose=
		Disable console loglevel raise on oops, panic
		or lockdep-detected issues (only if lock debug is on).
		With an exception to setups with low baudrate on
		serial console, keeping this 0 is a good choice
		in order to provide more debug information.
		Format: <bool>
		default: 0 (auto_verbose is enabled)

printk.devkmsg={on,off,ratelimit}
		Control writing to /dev/kmsg.
		on - unlimited logging to /dev/kmsg from userspace
		off - logging to /dev/kmsg disabled
		ratelimit - ratelimit the logging
		Default: ratelimit

printk.time=	Show timing data prefixed to each printk message line
		Format: <bool>  (1/Y/y=enable, 0/N/n=disable)

processor.max_cstate=	[HW,ACPI]
		Limit processor to maximum C-state
		max_cstate=9 overrides any DMI blacklist limit.

processor.nocst	[HW,ACPI]
		Ignore the _CST method to determine C-states,
		instead using the legacy FADT method

profile=	[KNL] Enable kernel profiling via /proc/profile
		Format: [<profiletype>,]<number>
		Param: <profiletype>: "schedule", "sleep", or "kvm"
			[defaults to kernel profiling]
		Param: "schedule" - profile schedule points.
		Param: "sleep" - profile D-state sleeping (millisecs).
			Requires CONFIG_SCHEDSTATS
		Param: "kvm" - profile VM exits.
		Param: <number> - step/bucket size as a power of 2 for
			statistical time based profiling.

prompt_ramdisk=	[RAM] [Deprecated]

prot_virt=	[S390] enable hosting protected virtual machines
		isolated from the hypervisor (if hardware supports
		that).
		Format: <bool>

psi=		[KNL] Enable or disable pressure stall information
		tracking.
		Format: <bool>

psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
		probe for; one of (bare|imps|exps|lifebook|any).
psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
		per second.
psmouse.resetafter=	[HW,MOUSE]
		Try to reset the device after so many bad packets
		(0 = never).
psmouse.resolution=
		[HW,MOUSE] Set desired mouse resolution, in dpi.
psmouse.smartscroll=
		[HW,MOUSE] Controls Logitech smartscroll autorepeat.
		0 = disabled, 1 = enabled (default).

pstore.backend=	Specify the name of the pstore backend to use

pti=		[X86-64] Control Page Table Isolation of user and
		kernel address spaces.  Disabling this feature
		removes hardening, but improves performance of
		system calls and interrupts.

		on   - unconditionally enable
		off  - unconditionally disable
		auto - kernel detects whether your CPU model is
		       vulnerable to issues that PTI mitigates

		Not specifying this option is equivalent to pti=auto.

pty.legacy_count=
		[KNL] Number of legacy pty's. Overwrites compiled-in
		default number.

quiet		[KNL] Disable most log messages

r128=		[HW,DRM]

radix_hcall_invalidate=on  [PPC/PSERIES]
		Disable RADIX GTSE feature and use hcall for TLB
		invalidate.

raid=		[HW,RAID]
		See Documentation/admin-guide/md.rst.

ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
		See Documentation/admin-guide/blockdev/ramdisk.rst.

ramdisk_start=	[RAM] RAM disk image start address

random.trust_cpu=off
		[KNL] Disable trusting the use of the CPU's
		random number generator (if available) to
		initialize the kernel's RNG.

random.trust_bootloader=off
		[KNL] Disable trusting the use of the a seed
		passed by the bootloader (if available) to
		initialize the kernel's RNG.

randomize_kstack_offset=
		[KNL] Enable or disable kernel stack offset
		randomization, which provides roughly 5 bits of
		entropy, frustrating memory corruption attacks
		that depend on stack address determinism or
		cross-syscall address exposures. This is only
		available on architectures that have defined
		CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
		Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
		Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.

ras=option[,option,...]	[KNL] RAS-specific options

	cec_disable	[X86]
			Disable the Correctable Errors Collector,
			see CONFIG_RAS_CEC help text.

rcu_nocbs[=cpu-list]
		[KNL] The optional argument is a cpu list,
		as described above.

		In kernels built with CONFIG_RCU_NOCB_CPU=y,
		enable the no-callback CPU mode, which prevents
		such CPUs' callbacks from being invoked in
		softirq context.  Invocation of such CPUs' RCU
		callbacks will instead be offloaded to "rcuox/N"
		kthreads created for that purpose, where "x" is
		"p" for RCU-preempt, "s" for RCU-sched, and "g"
		for the kthreads that mediate grace periods; and
		"N" is the CPU number. This reduces OS jitter on
		the offloaded CPUs, which can be useful for HPC
		and real-time workloads.  It can also improve
		energy efficiency for asymmetric multiprocessors.

		If a cpulist is passed as an argument, the specified
		list of	CPUs is set to no-callback mode from boot.

		Otherwise, if the '=' sign and the cpulist
		arguments are omitted, no CPU will be set to
		no-callback mode from boot but the mode may be
		toggled at runtime via cpusets.

		Note that this argument takes precedence over
		the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.

rcu_nocb_poll	[KNL]
		Rather than requiring that offloaded CPUs
		(specified by rcu_nocbs= above) explicitly
		awaken the corresponding "rcuoN" kthreads,
		make these kthreads poll for callbacks.
		This improves the real-time response for the
		offloaded CPUs by relieving them of the need to
		wake up the corresponding kthread, but degrades
		energy efficiency by requiring that the kthreads
		periodically wake up to do the polling.

rcutree.blimit=	[KNL]
		Set maximum number of finished RCU callbacks to
		process in one batch.

rcutree.dump_tree=	[KNL]
		Dump the structure of the rcu_node combining tree
		out at early boot.  This is used for diagnostic
		purposes, to verify correct tree setup.

rcutree.gp_cleanup_delay=	[KNL]
		Set the number of jiffies to delay each step of
		RCU grace-period cleanup.

rcutree.gp_init_delay=	[KNL]
		Set the number of jiffies to delay each step of
		RCU grace-period initialization.

rcutree.gp_preinit_delay=	[KNL]
		Set the number of jiffies to delay each step of
		RCU grace-period pre-initialization, that is,
		the propagation of recent CPU-hotplug changes up
		the rcu_node combining tree.

rcutree.jiffies_till_first_fqs= [KNL]
		Set delay from grace-period initialization to
		first attempt to force quiescent states.
		Units are jiffies, minimum value is zero,
		and maximum value is HZ.

rcutree.jiffies_till_next_fqs= [KNL]
		Set delay between subsequent attempts to force
		quiescent states.  Units are jiffies, minimum
		value is one, and maximum value is HZ.

rcutree.jiffies_till_sched_qs= [KNL]
		Set required age in jiffies for a
		given grace period before RCU starts
		soliciting quiescent-state help from
		rcu_note_context_switch() and cond_resched().
		If not specified, the kernel will calculate
		a value based on the most recent settings
		of rcutree.jiffies_till_first_fqs
		and rcutree.jiffies_till_next_fqs.
		This calculated value may be viewed in
		rcutree.jiffies_to_sched_qs.  Any attempt to set
		rcutree.jiffies_to_sched_qs will be cheerfully
		overwritten.

rcutree.kthread_prio= 	 [KNL,BOOT]
		Set the SCHED_FIFO priority of the RCU per-CPU
		kthreads (rcuc/N). This value is also used for
		the priority of the RCU boost threads (rcub/N)
		and for the RCU grace-period kthreads (rcu_bh,
		rcu_preempt, and rcu_sched). If RCU_BOOST is
		set, valid values are 1-99 and the default is 1
		(the least-favored priority).  Otherwise, when
		RCU_BOOST is not set, valid values are 0-99 and
		the default is zero (non-realtime operation).
		When RCU_NOCB_CPU is set, also adjust the
		priority of NOCB callback kthreads.

rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
		On callback-offloaded (rcu_nocbs) CPUs,
		RCU reduces the lock contention that would
		otherwise be caused by callback floods through
		use of the ->nocb_bypass list.	However, in the
		common non-flooded case, RCU queues directly to
		the main ->cblist in order to avoid the extra
		overhead of the ->nocb_bypass list and its lock.
		But if there are too many callbacks queued during
		a single jiffy, RCU pre-queues the callbacks into
		the ->nocb_bypass queue.  The definition of "too
		many" is supplied by this kernel boot parameter.

rcutree.qhimark= [KNL]
		Set threshold of queued RCU callbacks beyond which
		batch limiting is disabled.

rcutree.qlowmark= [KNL]
		Set threshold of queued RCU callbacks below which
		batch limiting is re-enabled.

rcutree.qovld= [KNL]
		Set threshold of queued RCU callbacks beyond which
		RCU's force-quiescent-state scan will aggressively
		enlist help from cond_resched() and sched IPIs to
		help CPUs more quickly reach quiescent states.
		Set to less than zero to make this be set based
		on rcutree.qhimark at boot time and to zero to
		disable more aggressive help enlistment.

rcutree.rcu_delay_page_cache_fill_msec= [KNL]
		Set the page-cache refill delay (in milliseconds)
		in response to low-memory conditions.  The range
		of permitted values is in the range 0:100000.

rcutree.rcu_divisor= [KNL]
		Set the shift-right count to use to compute
		the callback-invocation batch limit bl from
		the number of callbacks queued on this CPU.
		The result will be bounded below by the value of
		the rcutree.blimit kernel parameter.  Every bl
		callbacks, the softirq handler will exit in
		order to allow the CPU to do other work.

		Please note that this callback-invocation batch
		limit applies only to non-offloaded callback
		invocation.  Offloaded callbacks are instead
		invoked in the context of an rcuoc kthread, which
		scheduler will preempt as it does any other task.

rcutree.rcu_fanout_exact= [KNL]
		Disable autobalancing of the rcu_node combining
		tree.  This is used by rcutorture, and might
		possibly be useful for architectures having high
		cache-to-cache transfer latencies.

rcutree.rcu_fanout_leaf= [KNL]
		Change the number of CPUs assigned to each
		leaf rcu_node structure.  Useful for very
		large systems, which will choose the value 64,
		and for NUMA systems with large remote-access
		latencies, which will choose a value aligned
		with the appropriate hardware boundaries.

rcutree.rcu_min_cached_objs= [KNL]
		Minimum number of objects which are cached and
		maintained per one CPU. Object size is equal
		to PAGE_SIZE. The cache allows to reduce the
		pressure to page allocator, also it makes the
		whole algorithm to behave better in low memory
		condition.

rcutree.rcu_nocb_gp_stride= [KNL]
		Set the number of NOCB callback kthreads in
		each group, which defaults to the square root
		of the number of CPUs.	Larger numbers reduce
		the wakeup overhead on the global grace-period
		kthread, but increases that same overhead on
		each group's NOCB grace-period kthread.

rcutree.rcu_kick_kthreads= [KNL]
		Cause the grace-period kthread to get an extra
		wake_up() if it sleeps three times longer than
		it should at force-quiescent-state time.
		This wake_up() will be accompanied by a
		WARN_ONCE() splat and an ftrace_dump().

rcutree.rcu_resched_ns= [KNL]
		Limit the time spend invoking a batch of RCU
		callbacks to the specified number of nanoseconds.
		By default, this limit is checked only once
		every 32 callbacks in order to limit the pain
		inflicted by local_clock() overhead.

rcutree.rcu_unlock_delay= [KNL]
		In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
		this specifies an rcu_read_unlock()-time delay
		in microseconds.  This defaults to zero.
		Larger delays increase the probability of
		catching RCU pointer leaks, that is, buggy use
		of RCU-protected pointers after the relevant
		rcu_read_unlock() has completed.

rcutree.sysrq_rcu= [KNL]
		Commandeer a sysrq key to dump out Tree RCU's
		rcu_node tree with an eye towards determining
		why a new grace period has not yet started.

rcutree.use_softirq=	[KNL]
		If set to zero, move all RCU_SOFTIRQ processing to
		per-CPU rcuc kthreads.  Defaults to a non-zero
		value, meaning that RCU_SOFTIRQ is used by default.
		Specify rcutree.use_softirq=0 to use rcuc kthreads.

		But note that CONFIG_PREEMPT_RT=y kernels disable
		this kernel boot parameter, forcibly setting it
		to zero.

rcuscale.gp_async= [KNL]
		Measure performance of asynchronous
		grace-period primitives such as call_rcu().

rcuscale.gp_async_max= [KNL]
		Specify the maximum number of outstanding
		callbacks per writer thread.  When a writer
		thread exceeds this limit, it invokes the
		corresponding flavor of rcu_barrier() to allow
		previously posted callbacks to drain.

rcuscale.gp_exp= [KNL]
		Measure performance of expedited synchronous
		grace-period primitives.

rcuscale.holdoff= [KNL]
		Set test-start holdoff period.  The purpose of
		this parameter is to delay the start of the
		test until boot completes in order to avoid
		interference.

rcuscale.kfree_by_call_rcu= [KNL]
		In kernels built with CONFIG_RCU_LAZY=y, test
		call_rcu() instead of kfree_rcu().

rcuscale.kfree_mult= [KNL]
		Instead of allocating an object of size kfree_obj,
		allocate one of kfree_mult * sizeof(kfree_obj).
		Defaults to 1.

rcuscale.kfree_rcu_test= [KNL]
		Set to measure performance of kfree_rcu() flooding.

rcuscale.kfree_rcu_test_double= [KNL]
		Test the double-argument variant of kfree_rcu().
		If this parameter has the same value as
		rcuscale.kfree_rcu_test_single, both the single-
		and double-argument variants are tested.

rcuscale.kfree_rcu_test_single= [KNL]
		Test the single-argument variant of kfree_rcu().
		If this parameter has the same value as
		rcuscale.kfree_rcu_test_double, both the single-
		and double-argument variants are tested.

rcuscale.kfree_nthreads= [KNL]
		The number of threads running loops of kfree_rcu().

rcuscale.kfree_alloc_num= [KNL]
		Number of allocations and frees done in an iteration.

rcuscale.kfree_loops= [KNL]
		Number of loops doing rcuscale.kfree_alloc_num number
		of allocations and frees.

rcuscale.minruntime= [KNL]
		Set the minimum test run time in seconds.  This
		does not affect the data-collection interval,
		but instead allows better measurement of things
		like CPU consumption.

rcuscale.nreaders= [KNL]
		Set number of RCU readers.  The value -1 selects
		N, where N is the number of CPUs.  A value
		"n" less than -1 selects N-n+1, where N is again
		the number of CPUs.  For example, -2 selects N
		(the number of CPUs), -3 selects N+1, and so on.
		A value of "n" less than or equal to -N selects
		a single reader.

rcuscale.nwriters= [KNL]
		Set number of RCU writers.  The values operate
		the same as for rcuscale.nreaders.
		N, where N is the number of CPUs

rcuscale.scale_type= [KNL]
		Specify the RCU implementation to test.

rcuscale.shutdown= [KNL]
		Shut the system down after performance tests
		complete.  This is useful for hands-off automated
		testing.

rcuscale.verbose= [KNL]
		Enable additional printk() statements.

rcuscale.writer_holdoff= [KNL]
		Write-side holdoff between grace periods,
		in microseconds.  The default of zero says
		no holdoff.

rcuscale.writer_holdoff_jiffies= [KNL]
		Additional write-side holdoff between grace
		periods, but in jiffies.  The default of zero
		says no holdoff.

rcutorture.fqs_duration= [KNL]
		Set duration of force_quiescent_state bursts
		in microseconds.

rcutorture.fqs_holdoff= [KNL]
		Set holdoff time within force_quiescent_state bursts
		in microseconds.

rcutorture.fqs_stutter= [KNL]
		Set wait time between force_quiescent_state bursts
		in seconds.

rcutorture.fwd_progress= [KNL]
		Specifies the number of kthreads to be used
		for  RCU grace-period forward-progress testing
		for the types of RCU supporting this notion.
		Defaults to 1 kthread, values less than zero or
		greater than the number of CPUs cause the number
		of CPUs to be used.

rcutorture.fwd_progress_div= [KNL]
		Specify the fraction of a CPU-stall-warning
		period to do tight-loop forward-progress testing.

rcutorture.fwd_progress_holdoff= [KNL]
		Number of seconds to wait between successive
		forward-progress tests.

rcutorture.fwd_progress_need_resched= [KNL]
		Enclose cond_resched() calls within checks for
		need_resched() during tight-loop forward-progress
		testing.

rcutorture.gp_cond= [KNL]
		Use conditional/asynchronous update-side
		primitives, if available.

rcutorture.gp_exp= [KNL]
		Use expedited update-side primitives, if available.

rcutorture.gp_normal= [KNL]
		Use normal (non-expedited) asynchronous
		update-side primitives, if available.

rcutorture.gp_sync= [KNL]
		Use normal (non-expedited) synchronous
		update-side primitives, if available.  If all
		of rcutorture.gp_cond=, rcutorture.gp_exp=,
		rcutorture.gp_normal=, and rcutorture.gp_sync=
		are zero, rcutorture acts as if is interpreted
		they are all non-zero.

rcutorture.irqreader= [KNL]
		Run RCU readers from irq handlers, or, more
		accurately, from a timer handler.  Not all RCU
		flavors take kindly to this sort of thing.

rcutorture.leakpointer= [KNL]
		Leak an RCU-protected pointer out of the reader.
		This can of course result in splats, and is
		intended to test the ability of things like
		CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
		such leaks.

rcutorture.n_barrier_cbs= [KNL]
		Set callbacks/threads for rcu_barrier() testing.

rcutorture.nfakewriters= [KNL]
		Set number of concurrent RCU writers.  These just
		stress RCU, they don't participate in the actual
		test, hence the "fake".

rcutorture.nocbs_nthreads= [KNL]
		Set number of RCU callback-offload togglers.
		Zero (the default) disables toggling.

rcutorture.nocbs_toggle= [KNL]
		Set the delay in milliseconds between successive
		callback-offload toggling attempts.

rcutorture.nreaders= [KNL]
		Set number of RCU readers.  The value -1 selects
		N-1, where N is the number of CPUs.  A value
		"n" less than -1 selects N-n-2, where N is again
		the number of CPUs.  For example, -2 selects N
		(the number of CPUs), -3 selects N+1, and so on.

rcutorture.object_debug= [KNL]
		Enable debug-object double-call_rcu() testing.

rcutorture.onoff_holdoff= [KNL]
		Set time (s) after boot for CPU-hotplug testing.

rcutorture.onoff_interval= [KNL]
		Set time (jiffies) between CPU-hotplug operations,
		or zero to disable CPU-hotplug testing.

rcutorture.read_exit= [KNL]
		Set the number of read-then-exit kthreads used
		to test the interaction of RCU updaters and
		task-exit processing.

rcutorture.read_exit_burst= [KNL]
		The number of times in a given read-then-exit
		episode that a set of read-then-exit kthreads
		is spawned.

rcutorture.read_exit_delay= [KNL]
		The delay, in seconds, between successive
		read-then-exit testing episodes.

rcutorture.shuffle_interval= [KNL]
		Set task-shuffle interval (s).  Shuffling tasks
		allows some CPUs to go into dyntick-idle mode
		during the rcutorture test.

rcutorture.shutdown_secs= [KNL]
		Set time (s) after boot system shutdown.  This
		is useful for hands-off automated testing.

rcutorture.stall_cpu= [KNL]
		Duration of CPU stall (s) to test RCU CPU stall
		warnings, zero to disable.

rcutorture.stall_cpu_block= [KNL]
		Sleep while stalling if set.  This will result
		in warnings from preemptible RCU in addition to
		any other stall-related activity.  Note that
		in kernels built with CONFIG_PREEMPTION=n and
		CONFIG_PREEMPT_COUNT=y, this parameter will
		cause the CPU to pass through a quiescent state.
		Given CONFIG_PREEMPTION=n, this will suppress
		RCU CPU stall warnings, but will instead result
		in scheduling-while-atomic splats.

		Use of this module parameter results in splats.


rcutorture.stall_cpu_holdoff= [KNL]
		Time to wait (s) after boot before inducing stall.

rcutorture.stall_cpu_irqsoff= [KNL]
		Disable interrupts while stalling if set.

rcutorture.stall_gp_kthread= [KNL]
		Duration (s) of forced sleep within RCU
		grace-period kthread to test RCU CPU stall
		warnings, zero to disable.  If both stall_cpu
		and stall_gp_kthread are specified, the
		kthread is starved first, then the CPU.

rcutorture.stat_interval= [KNL]
		Time (s) between statistics printk()s.

rcutorture.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 RCU's
		ability to transition abruptly to and from idle.

rcutorture.test_boost= [KNL]
		Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
		"Maybe" means test if the RCU implementation
		under test support RCU priority boosting.

rcutorture.test_boost_duration= [KNL]
		Duration (s) of each individual boost test.

rcutorture.test_boost_interval= [KNL]
		Interval (s) between each boost test.

rcutorture.test_no_idle_hz= [KNL]
		Test RCU's dyntick-idle handling.  See also the
		rcutorture.shuffle_interval parameter.

rcutorture.torture_type= [KNL]
		Specify the RCU implementation to test.

rcutorture.verbose= [KNL]
		Enable additional printk() statements.

rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
		Dump ftrace buffer after reporting RCU CPU
		stall warning.

rcupdate.rcu_cpu_stall_suppress= [KNL]
		Suppress RCU CPU stall warning messages.

rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
		Suppress RCU CPU stall warning messages and
		rcutorture writer stall warnings that occur
		during early boot, that is, during the time
		before the init task is spawned.

rcupdate.rcu_cpu_stall_timeout= [KNL]
		Set timeout for RCU CPU stall warning messages.
		The value is in seconds and the maximum allowed
		value is 300 seconds.

rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
		Set timeout for expedited RCU CPU stall warning
		messages.  The value is in milliseconds
		and the maximum allowed value is 21000
		milliseconds. Please note that this value is
		adjusted to an arch timer tick resolution.
		Setting this to zero causes the value from
		rcupdate.rcu_cpu_stall_timeout to be used (after
		conversion from seconds to milliseconds).

rcupdate.rcu_cpu_stall_cputime= [KNL]
		Provide statistics on the cputime and count of
		interrupts and tasks during the sampling period. For
		multiple continuous RCU stalls, all sampling periods
		begin at half of the first RCU stall timeout.

rcupdate.rcu_exp_stall_task_details= [KNL]
		Print stack dumps of any tasks blocking the
		current expedited RCU grace period during an
		expedited RCU CPU stall warning.

rcupdate.rcu_expedited= [KNL]
		Use expedited grace-period primitives, for
		example, synchronize_rcu_expedited() instead
		of synchronize_rcu().  This reduces latency,
		but can increase CPU utilization, degrade
		real-time latency, and degrade energy efficiency.
		No effect on CONFIG_TINY_RCU kernels.

rcupdate.rcu_normal= [KNL]
		Use only normal grace-period primitives,
		for example, synchronize_rcu() instead of
		synchronize_rcu_expedited().  This improves
		real-time latency, CPU utilization, and
		energy efficiency, but can expose users to
		increased grace-period latency.  This parameter
		overrides rcupdate.rcu_expedited.  No effect on
		CONFIG_TINY_RCU kernels.

rcupdate.rcu_normal_after_boot= [KNL]
		Once boot has completed (that is, after
		rcu_end_inkernel_boot() has been invoked), use
		only normal grace-period primitives.  No effect
		on CONFIG_TINY_RCU kernels.

		But note that CONFIG_PREEMPT_RT=y kernels enables
		this kernel boot parameter, forcibly setting
		it to the value one, that is, converting any
		post-boot attempt at an expedited RCU grace
		period to instead use normal non-expedited
		grace-period processing.

rcupdate.rcu_task_collapse_lim= [KNL]
		Set the maximum number of callbacks present
		at the beginning of a grace period that allows
		the RCU Tasks flavors to collapse back to using
		a single callback queue.  This switching only
		occurs when rcupdate.rcu_task_enqueue_lim is
		set to the default value of -1.

rcupdate.rcu_task_contend_lim= [KNL]
		Set the minimum number of callback-queuing-time
		lock-contention events per jiffy required to
		cause the RCU Tasks flavors to switch to per-CPU
		callback queuing.  This switching only occurs
		when rcupdate.rcu_task_enqueue_lim is set to
		the default value of -1.

rcupdate.rcu_task_enqueue_lim= [KNL]
		Set the number of callback queues to use for the
		RCU Tasks family of RCU flavors.  The default
		of -1 allows this to be automatically (and
		dynamically) adjusted.	This parameter is intended
		for use in testing.

rcupdate.rcu_task_ipi_delay= [KNL]
		Set time in jiffies during which RCU tasks will
		avoid sending IPIs, starting with the beginning
		of a given grace period.  Setting a large
		number avoids disturbing real-time workloads,
		but lengthens grace periods.

rcupdate.rcu_task_lazy_lim= [KNL]
		Number of callbacks on a given CPU that will
		cancel laziness on that CPU.  Use -1 to disable
		cancellation of laziness, but be advised that
		doing so increases the danger of OOM due to
		callback flooding.

rcupdate.rcu_task_stall_info= [KNL]
		Set initial timeout in jiffies for RCU task stall
		informational messages, which give some indication
		of the problem for those not patient enough to
		wait for ten minutes.  Informational messages are
		only printed prior to the stall-warning message
		for a given grace period. Disable with a value
		less than or equal to zero.  Defaults to ten
		seconds.  A change in value does not take effect
		until the beginning of the next grace period.

rcupdate.rcu_task_stall_info_mult= [KNL]
		Multiplier for time interval between successive
		RCU task stall informational messages for a given
		RCU tasks grace period.  This value is clamped
		to one through ten, inclusive.	It defaults to
		the value three, so that the first informational
		message is printed 10 seconds into the grace
		period, the second at 40 seconds, the third at
		160 seconds, and then the stall warning at 600
		seconds would prevent a fourth at 640 seconds.

rcupdate.rcu_task_stall_timeout= [KNL]
		Set timeout in jiffies for RCU task stall
		warning messages.  Disable with a value less
		than or equal to zero.	Defaults to ten minutes.
		A change in value does not take effect until
		the beginning of the next grace period.

rcupdate.rcu_tasks_lazy_ms= [KNL]
		Set timeout in milliseconds RCU Tasks asynchronous
		callback batching for call_rcu_tasks().
		A negative value will take the default.  A value
		of zero will disable batching.	Batching is
		always disabled for synchronize_rcu_tasks().

rcupdate.rcu_tasks_rude_lazy_ms= [KNL]
		Set timeout in milliseconds RCU Tasks
		Rude asynchronous callback batching for
		call_rcu_tasks_rude().	A negative value
		will take the default.	A value of zero will
		disable batching.  Batching is always disabled
		for synchronize_rcu_tasks_rude().

rcupdate.rcu_tasks_trace_lazy_ms= [KNL]
		Set timeout in milliseconds RCU Tasks
		Trace asynchronous callback batching for
		call_rcu_tasks_trace().  A negative value
		will take the default.	A value of zero will
		disable batching.  Batching is always disabled
		for synchronize_rcu_tasks_trace().

rcupdate.rcu_self_test= [KNL]
		Run the RCU early boot self tests

rdinit=		[KNL]
		Format: <full_path>
		Run specified binary instead of /init from the ramdisk,
		used for early userspace startup. See initrd.

rdrand=		[X86]
		force - Override the decision by the kernel to hide the
			advertisement of RDRAND support (this affects
			certain AMD processors because of buggy BIOS
			support, specifically around the suspend/resume
			path).

rdt=		[HW,X86,RDT]
		Turn on/off individual RDT features. List is:
		cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
		mba, smba, bmec.
		E.g. to turn on cmt and turn off mba use:
			rdt=cmt,!mba

reboot=		[KNL]
		Format (x86 or x86_64):
			[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
			[[,]s[mp]#### \
			[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
			[[,]f[orce]
		Where reboot_mode is one of warm (soft) or cold (hard) or gpio
				(prefix with 'panic_' to set mode for panic
				reboot only),
		      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
		      reboot_force is either force or not specified,
		      reboot_cpu is s[mp]#### with #### being the processor
				to be used for rebooting.

refscale.holdoff= [KNL]
		Set test-start holdoff period.  The purpose of
		this parameter is to delay the start of the
		test until boot completes in order to avoid
		interference.

refscale.loops= [KNL]
		Set the number of loops over the synchronization
		primitive under test.  Increasing this number
		reduces noise due to loop start/end overhead,
		but the default has already reduced the per-pass
		noise to a handful of picoseconds on ca. 2020
		x86 laptops.

refscale.nreaders= [KNL]
		Set number of readers.  The default value of -1
		selects N, where N is roughly 75% of the number
		of CPUs.  A value of zero is an interesting choice.

refscale.nruns= [KNL]
		Set number of runs, each of which is dumped onto
		the console log.

refscale.readdelay= [KNL]
		Set the read-side critical-section duration,
		measured in microseconds.

refscale.scale_type= [KNL]
		Specify the read-protection implementation to test.

refscale.shutdown= [KNL]
		Shut down the system at the end of the performance
		test.  This defaults to 1 (shut it down) when
		refscale is built into the kernel and to 0 (leave
		it running) when refscale is built as a module.

refscale.verbose= [KNL]
		Enable additional printk() statements.

refscale.verbose_batched= [KNL]
		Batch the additional printk() statements.  If zero
		(the default) or negative, print everything.  Otherwise,
		print every Nth verbose statement, where N is the value
		specified.

relax_domain_level=
		[KNL, SMP] Set scheduler's default relax_domain_level.
		See Documentation/admin-guide/cgroup-v1/cpusets.rst.

reserve=	[KNL,BUGS] Force kernel to ignore I/O ports or memory
		Format: <base1>,<size1>[,<base2>,<size2>,...]
		Reserve I/O ports or memory so the kernel won't use
		them.  If <base> is less than 0x10000, the region
		is assumed to be I/O ports; otherwise it is memory.

reservetop=	[X86-32]
		Format: nn[KMG]
		Reserves a hole at the top of the kernel virtual
		address space.

reset_devices	[KNL] Force drivers to reset the underlying device
		during initialization.

resume=		[SWSUSP]
		Specify the partition device for software suspend
		Format:
		{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}

resume_offset=	[SWSUSP]
		Specify the offset from the beginning of the partition
		given by "resume=" at which the swap header is located,
		in <PAGE_SIZE> units (needed only for swap files).
		See  Documentation/power/swsusp-and-swap-files.rst

resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
		read the resume files

resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
		Useful for devices that are detected asynchronously
		(e.g. USB and MMC devices).

retain_initrd	[RAM] Keep initrd memory after extraction

retbleed=	[X86] Control mitigation of RETBleed (Arbitrary
		Speculative Code Execution with Return Instructions)
		vulnerability.

		AMD-based UNRET and IBPB mitigations alone do not stop
		sibling threads from influencing the predictions of other
		sibling threads. For that reason, STIBP is used on pro-
		cessors that support it, and mitigate SMT on processors
		that don't.

		off          - no mitigation
		auto         - automatically select a migitation
		auto,nosmt   - automatically select a mitigation,
			       disabling SMT if necessary for
			       the full mitigation (only on Zen1
			       and older without STIBP).
		ibpb         - On AMD, mitigate short speculation
			       windows on basic block boundaries too.
			       Safe, highest perf impact. It also
			       enables STIBP if present. Not suitable
			       on Intel.
		ibpb,nosmt   - Like "ibpb" above but will disable SMT
			       when STIBP is not available. This is
			       the alternative for systems which do not
			       have STIBP.
		unret        - Force enable untrained return thunks,
			       only effective on AMD f15h-f17h based
			       systems.
		unret,nosmt  - Like unret, but will disable SMT when STIBP
			       is not available. This is the alternative for
			       systems which do not have STIBP.

		Selecting 'auto' will choose a mitigation method at run
		time according to the CPU.

		Not specifying this option is equivalent to retbleed=auto.

rfkill.default_state=
	0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
		etc. communication is blocked by default.
	1	Unblocked.

rfkill.master_switch_mode=
	0	The "airplane mode" button does nothing.
	1	The "airplane mode" button toggles between everything
		blocked and the previous configuration.
	2	The "airplane mode" button toggles between everything
		blocked and everything unblocked.

rhash_entries=	[KNL,NET]
		Set number of hash buckets for route cache

ring3mwait=disable
		[KNL] Disable ring 3 MONITOR/MWAIT feature on supported
		CPUs.

riscv_isa_fallback [RISCV]
		When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit
		falling back to detecting extension support by parsing
		"riscv,isa" property on devicetree systems when the
		replacement properties are not found. See the Kconfig
		entry for RISCV_ISA_FALLBACK.

ro		[KNL] Mount root device read-only on boot

rodata=		[KNL]
	on	Mark read-only kernel memory as read-only (default).
	off	Leave read-only kernel memory writable for debugging.
	full	Mark read-only kernel memory and aliases as read-only
	        [arm64]

rockchip.usb_uart
		Enable the uart passthrough on the designated usb port
		on Rockchip SoCs. When active, the signals of the
		debug-uart get routed to the D+ and D- pins of the usb
		port and the regular usb controller gets disabled.

root=		[KNL] Root filesystem
		Usually this a a block device specifier of some kind,
		see the early_lookup_bdev comment in
		block/early-lookup.c for details.
		Alternatively this can be "ram" for the legacy initial
		ramdisk, "nfs" and "cifs" for root on a network file
		system, or "mtd" and "ubi" for mounting from raw flash.

rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
		mount the root filesystem

rootflags=	[KNL] Set root filesystem mount option string

rootfstype=	[KNL] Set root filesystem type

rootwait	[KNL] Wait (indefinitely) for root device to show up.
		Useful for devices that are detected asynchronously
		(e.g. USB and MMC devices).

rootwait=	[KNL] Maximum time (in seconds) to wait for root device
		to show up before attempting to mount the root
		filesystem.

rproc_mem=nn[KMG][@address]
		[KNL,ARM,CMA] Remoteproc physical memory block.
		Memory area to be used by remote processor image,
		managed by CMA.

rw		[KNL] Mount root device read-write on boot

S		[KNL] Run init in single mode

s390_iommu=	[HW,S390]
		Set s390 IOTLB flushing mode
	strict
		With strict flushing every unmap operation will result in
		an IOTLB flush. Default is lazy flushing before reuse,
		which is faster.

s390_iommu_aperture=	[KNL,S390]
		Specifies the size of the per device DMA address space
		accessible through the DMA and IOMMU APIs as a decimal
		factor of the size of main memory.
		The default is 1 meaning that one can concurrently use
		as many DMA addresses as physical memory is installed,
		if supported by hardware, and thus map all of memory
		once. With a value of 2 one can map all of memory twice
		and so on. As a special case a factor of 0 imposes no
		restrictions other than those given by hardware at the
		cost of significant additional memory use for tables.

sa1100ir	[NET]
		See drivers/net/irda/sa1100_ir.c.

sched_verbose	[KNL] Enables verbose scheduler debug messages.

schedstats=	[KNL,X86] Enable or disable scheduled statistics.
		Allowed values are enable and disable. This feature
		incurs a small amount of overhead in the scheduler
		but is useful for debugging and performance tuning.

sched_thermal_decay_shift=
		[KNL, SMP] Set a decay shift for scheduler thermal
		pressure signal. Thermal pressure signal follows the
		default decay period of other scheduler pelt
		signals(usually 32 ms but configurable). Setting
		sched_thermal_decay_shift will left shift the decay
		period for the thermal pressure signal by the shift
		value.
		i.e. with the default pelt decay period of 32 ms
		sched_thermal_decay_shift   thermal pressure decay pr
			1			64 ms
			2			128 ms
		and so on.
		Format: integer between 0 and 10
		Default is 0.

scftorture.holdoff= [KNL]
		Number of seconds to hold off before starting
		test.  Defaults to zero for module insertion and
		to 10 seconds for built-in smp_call_function()
		tests.

scftorture.longwait= [KNL]
		Request ridiculously long waits randomly selected
		up to the chosen limit in seconds.  Zero (the
		default) disables this feature.  Please note
		that requesting even small non-zero numbers of
		seconds can result in RCU CPU stall warnings,
		softlockup complaints, and so on.

scftorture.nthreads= [KNL]
		Number of kthreads to spawn to invoke the
		smp_call_function() family of functions.
		The default of -1 specifies a number of kthreads
		equal to the number of CPUs.

scftorture.onoff_holdoff= [KNL]
		Number seconds to wait after the start of the
		test before initiating CPU-hotplug operations.

scftorture.onoff_interval= [KNL]
		Number seconds to wait between successive
		CPU-hotplug operations.  Specifying zero (which
		is the default) disables CPU-hotplug operations.

scftorture.shutdown_secs= [KNL]
		The number of seconds following the start of the
		test after which to shut down the system.  The
		default of zero avoids shutting down the system.
		Non-zero values are useful for automated tests.

scftorture.stat_interval= [KNL]
		The number of seconds between outputting the
		current test statistics to the console.  A value
		of zero disables statistics output.

scftorture.stutter_cpus= [KNL]
		The number of jiffies to wait between each change
		to the set of CPUs under test.

scftorture.use_cpus_read_lock= [KNL]
		Use use_cpus_read_lock() instead of the default
		preempt_disable() to disable CPU hotplug
		while invoking one of the smp_call_function*()
		functions.

scftorture.verbose= [KNL]
		Enable additional printk() statements.

scftorture.weight_single= [KNL]
		The probability weighting to use for the
		smp_call_function_single() function with a zero
		"wait" parameter.  A value of -1 selects the
		default if all other weights are -1.  However,
		if at least one weight has some other value, a
		value of -1 will instead select a weight of zero.

scftorture.weight_single_wait= [KNL]
		The probability weighting to use for the
		smp_call_function_single() function with a
		non-zero "wait" parameter.  See weight_single.

scftorture.weight_many= [KNL]
		The probability weighting to use for the
		smp_call_function_many() function with a zero
		"wait" parameter.  See weight_single.
		Note well that setting a high probability for
		this weighting can place serious IPI load
		on the system.

scftorture.weight_many_wait= [KNL]
		The probability weighting to use for the
		smp_call_function_many() function with a
		non-zero "wait" parameter.  See weight_single
		and weight_many.

scftorture.weight_all= [KNL]
		The probability weighting to use for the
		smp_call_function_all() function with a zero
		"wait" parameter.  See weight_single and
		weight_many.

scftorture.weight_all_wait= [KNL]
		The probability weighting to use for the
		smp_call_function_all() function with a
		non-zero "wait" parameter.  See weight_single
		and weight_many.

skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
		xtime_lock contention on larger systems, and/or RCU lock
		contention on all systems with CONFIG_MAXSMP set.
		Format: { "0" | "1" }
		0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
		1 -- enable.
		Note: increases power consumption, thus should only be
		enabled if running jitter sensitive (HPC/RT) workloads.

security=	[SECURITY] Choose a legacy "major" security module to
		enable at boot. This has been deprecated by the
		"lsm=" parameter.

selinux=	[SELINUX] Disable or enable SELinux at boot time.
		Format: { "0" | "1" }
		See security/selinux/Kconfig help text.
		0 -- disable.
		1 -- enable.
		Default value is 1.

serialnumber	[BUGS=X86-32]

sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst

shapers=	[NET]
		Maximal number of shapers.

show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
		Limit apic dumping. The parameter defines the maximal
		number of local apics being dumped. Also it is possible
		to set it to "all" by meaning -- no limit here.
		Format: { 1 (default) | 2 | ... | all }.
		The parameter valid if only apic=debug or
		apic=verbose is specified.
		Example: apic=debug show_lapic=all

simeth=		[IA-64]
simscsi=

slram=		[HW,MTD]

slab_merge	[MM]
		Enable merging of slabs with similar size when the
		kernel is built without CONFIG_SLAB_MERGE_DEFAULT.

slab_nomerge	[MM]
		Disable merging of slabs with similar size. May be
		necessary if there is some reason to distinguish
		allocs to different slabs, especially in hardened
		environments where the risk of heap overflows and
		layout control by attackers can usually be
		frustrated by disabling merging. This will reduce
		most of the exposure of a heap attack to a single
		cache (risks via metadata attacks are mostly
		unchanged). Debug options disable merging on their
		own.
		For more information see Documentation/mm/slub.rst.

slab_max_order=	[MM, SLAB]
		Determines the maximum allowed order for slabs.
		A high setting may cause OOMs due to memory
		fragmentation.  Defaults to 1 for systems with
		more than 32MB of RAM, 0 otherwise.

slub_debug[=options[,slabs][;[options[,slabs]]...]	[MM, SLUB]
		Enabling slub_debug allows one to determine the
		culprit if slab objects become corrupted. Enabling
		slub_debug can create guard zones around objects and
		may poison objects when not in use. Also tracks the
		last alloc / free. For more information see
		Documentation/mm/slub.rst.

slub_max_order= [MM, SLUB]
		Determines the maximum allowed order for slabs.
		A high setting may cause OOMs due to memory
		fragmentation. For more information see
		Documentation/mm/slub.rst.

slub_min_objects=	[MM, SLUB]
		The minimum number of objects per slab. SLUB will
		increase the slab order up to slub_max_order to
		generate a sufficiently large slab able to contain
		the number of objects indicated. The higher the number
		of objects the smaller the overhead of tracking slabs
		and the less frequently locks need to be acquired.
		For more information see Documentation/mm/slub.rst.

slub_min_order=	[MM, SLUB]
		Determines the minimum page order for slabs. Must be
		lower than slub_max_order.
		For more information see Documentation/mm/slub.rst.

slub_merge	[MM, SLUB]
		Same with slab_merge.

slub_nomerge	[MM, SLUB]
		Same with slab_nomerge. This is supported for legacy.
		See slab_nomerge for more information.

smart2=		[HW]
		Format: <io1>[,<io2>[,...,<io8>]]

smp.csd_lock_timeout= [KNL]
		Specify the period of time in milliseconds
		that smp_call_function() and friends will wait
		for a CPU to release the CSD lock.  This is
		useful when diagnosing bugs involving CPUs
		disabling interrupts for extended periods
		of time.  Defaults to 5,000 milliseconds, and
		setting a value of zero disables this feature.
		This feature may be more efficiently disabled
		using the csdlock_debug- kernel parameter.

smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
smsc-ircc2.ircc_irq=	[HW] IRQ line
smsc-ircc2.ircc_dma=	[HW] DMA channel
smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
			0: Toshiba Satellite 1800 (GP data pin select)
			1: Fast pin select (default)
			2: ATC IRMode

smt=		[KNL,MIPS,S390] Set the maximum number of threads (logical
		CPUs) to use per physical CPU on systems capable of
		symmetric multithreading (SMT). Will be capped to the
		actual hardware limit.
		Format: <integer>
		Default: -1 (no limit)

softlockup_panic=
		[KNL] Should the soft-lockup detector generate panics.
		Format: 0 | 1

		A value of 1 instructs the soft-lockup detector
		to panic the machine when a soft-lockup occurs. It is
		also controlled by the kernel.softlockup_panic sysctl
		and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
		respective build-time switch to that functionality.

softlockup_all_cpu_backtrace=
		[KNL] Should the soft-lockup detector generate
		backtraces on all cpus.
		Format: 0 | 1

sonypi.*=	[HW] Sony Programmable I/O Control Device driver
		See Documentation/admin-guide/laptops/sonypi.rst

spectre_v2=	[X86] Control mitigation of Spectre variant 2
		(indirect branch speculation) vulnerability.
		The default operation protects the kernel from
		user space attacks.

		on   - unconditionally enable, implies
		       spectre_v2_user=on
		off  - unconditionally disable, implies
		       spectre_v2_user=off
		auto - kernel detects whether your CPU model is
		       vulnerable

		Selecting 'on' will, and 'auto' may, choose a
		mitigation method at run time according to the
		CPU, the available microcode, the setting of the
		CONFIG_RETPOLINE configuration option, and the
		compiler with which the kernel was built.

		Selecting 'on' will also enable the mitigation
		against user space to user space task attacks.

		Selecting 'off' will disable both the kernel and
		the user space protections.

		Specific mitigations can also be selected manually:

		retpoline	  - replace indirect branches
		retpoline,generic - Retpolines
		retpoline,lfence  - LFENCE; indirect branch
		retpoline,amd     - alias for retpoline,lfence
		eibrs		  - Enhanced/Auto IBRS
		eibrs,retpoline   - Enhanced/Auto IBRS + Retpolines
		eibrs,lfence      - Enhanced/Auto IBRS + LFENCE
		ibrs		  - use IBRS to protect kernel

		Not specifying this option is equivalent to
		spectre_v2=auto.

spectre_v2_user=
		[X86] Control mitigation of Spectre variant 2
	        (indirect branch speculation) vulnerability between
	        user space tasks

		on	- Unconditionally enable mitigations. Is
			  enforced by spectre_v2=on

		off     - Unconditionally disable mitigations. Is
			  enforced by spectre_v2=off

		prctl   - Indirect branch speculation is enabled,
			  but mitigation can be enabled via prctl
			  per thread.  The mitigation control state
			  is inherited on fork.

		prctl,ibpb
			- Like "prctl" above, but only STIBP is
			  controlled per thread. IBPB is issued
			  always when switching between different user
			  space processes.

		seccomp
			- Same as "prctl" above, but all seccomp
			  threads will enable the mitigation unless
			  they explicitly opt out.

		seccomp,ibpb
			- Like "seccomp" above, but only STIBP is
			  controlled per thread. IBPB is issued
			  always when switching between different
			  user space processes.

		auto    - Kernel selects the mitigation depending on
			  the available CPU features and vulnerability.

		Default mitigation: "prctl"

		Not specifying this option is equivalent to
		spectre_v2_user=auto.

spec_rstack_overflow=
		[X86] Control RAS overflow mitigation on AMD Zen CPUs

		off		- Disable mitigation
		microcode	- Enable microcode mitigation only
		safe-ret	- Enable sw-only safe RET mitigation (default)
		ibpb		- Enable mitigation by issuing IBPB on
				  kernel entry
		ibpb-vmexit	- Issue IBPB only on VMEXIT
				  (cloud-specific mitigation)

spec_store_bypass_disable=
		[HW] Control Speculative Store Bypass (SSB) Disable mitigation
		(Speculative Store Bypass vulnerability)

		Certain CPUs are vulnerable to an exploit against a
		a common industry wide performance optimization known
		as "Speculative Store Bypass" in which recent stores
		to the same memory location may not be observed by
		later loads during speculative execution. The idea
		is that such stores are unlikely and that they can
		be detected prior to instruction retirement at the
		end of a particular speculation execution window.

		In vulnerable processors, the speculatively forwarded
		store can be used in a cache side channel attack, for
		example to read memory to which the attacker does not
		directly have access (e.g. inside sandboxed code).

		This parameter controls whether the Speculative Store
		Bypass optimization is used.

		On x86 the options are:

		on      - Unconditionally disable Speculative Store Bypass
		off     - Unconditionally enable Speculative Store Bypass
		auto    - Kernel detects whether the CPU model contains an
			  implementation of Speculative Store Bypass and
			  picks the most appropriate mitigation. If the
			  CPU is not vulnerable, "off" is selected. If the
			  CPU is vulnerable the default mitigation is
			  architecture and Kconfig dependent. See below.
		prctl   - Control Speculative Store Bypass per thread
			  via prctl. Speculative Store Bypass is enabled
			  for a process by default. The state of the control
			  is inherited on fork.
		seccomp - Same as "prctl" above, but all seccomp threads
			  will disable SSB unless they explicitly opt out.

		Default mitigations:
		X86:	"prctl"

		On powerpc the options are:

		on,auto - On Power8 and Power9 insert a store-forwarding
			  barrier on kernel entry and exit. On Power7
			  perform a software flush on kernel entry and
			  exit.
		off	- No action.

		Not specifying this option is equivalent to
		spec_store_bypass_disable=auto.

spia_io_base=	[HW,MTD]
spia_fio_base=
spia_pedr=
spia_peddr=

split_lock_detect=
		[X86] Enable split lock detection or bus lock detection

		When enabled (and if hardware support is present), atomic
		instructions that access data across cache line
		boundaries will result in an alignment check exception
		for split lock detection or a debug exception for
		bus lock detection.

		off	- not enabled

		warn	- the kernel will emit rate-limited warnings
			  about applications triggering the #AC
			  exception or the #DB exception. This mode is
			  the default on CPUs that support split lock
			  detection or bus lock detection. Default
			  behavior is by #AC if both features are
			  enabled in hardware.

		fatal	- the kernel will send SIGBUS to applications
			  that trigger the #AC exception or the #DB
			  exception. Default behavior is by #AC if
			  both features are enabled in hardware.

		ratelimit:N -
			  Set system wide rate limit to N bus locks
			  per second for bus lock detection.
			  0 < N <= 1000.

			  N/A for split lock detection.


		If an #AC exception is hit in the kernel or in
		firmware (i.e. not while executing in user mode)
		the kernel will oops in either "warn" or "fatal"
		mode.

		#DB exception for bus lock is triggered only when
		CPL > 0.

srbds=		[X86,INTEL]
		Control the Special Register Buffer Data Sampling
		(SRBDS) mitigation.

		Certain CPUs are vulnerable to an MDS-like
		exploit which can leak bits from the random
		number generator.

		By default, this issue is mitigated by
		microcode.  However, the microcode fix can cause
		the RDRAND and RDSEED instructions to become
		much slower.  Among other effects, this will
		result in reduced throughput from /dev/urandom.

		The microcode mitigation can be disabled with
		the following option:

		off:    Disable mitigation and remove
			performance impact to RDRAND and RDSEED

srcutree.big_cpu_lim [KNL]
		Specifies the number of CPUs constituting a
		large system, such that srcu_struct structures
		should immediately allocate an srcu_node array.
		This kernel-boot parameter defaults to 128,
		but takes effect only when the low-order four
		bits of srcutree.convert_to_big is equal to 3
		(decide at boot).

srcutree.convert_to_big [KNL]
		Specifies under what conditions an SRCU tree
		srcu_struct structure will be converted to big
		form, that is, with an rcu_node tree:

			   0:  Never.
			   1:  At init_srcu_struct() time.
			   2:  When rcutorture decides to.
			   3:  Decide at boot time (default).
			0x1X:  Above plus if high contention.

		Either way, the srcu_node tree will be sized based
		on the actual runtime number of CPUs (nr_cpu_ids)
		instead of the compile-time CONFIG_NR_CPUS.

srcutree.counter_wrap_check [KNL]
		Specifies how frequently to check for
		grace-period sequence counter wrap for the
		srcu_data structure's ->srcu_gp_seq_needed field.
		The greater the number of bits set in this kernel
		parameter, the less frequently counter wrap will
		be checked for.  Note that the bottom two bits
		are ignored.

srcutree.exp_holdoff [KNL]
		Specifies how many nanoseconds must elapse
		since the end of the last SRCU grace period for
		a given srcu_struct until the next normal SRCU
		grace period will be considered for automatic
		expediting.  Set to zero to disable automatic
		expediting.

srcutree.srcu_max_nodelay [KNL]
		Specifies the number of no-delay instances
		per jiffy for which the SRCU grace period
		worker thread will be rescheduled with zero
		delay. Beyond this limit, worker thread will
		be rescheduled with a sleep delay of one jiffy.

srcutree.srcu_max_nodelay_phase [KNL]
		Specifies the per-grace-period phase, number of
		non-sleeping polls of readers. Beyond this limit,
		grace period worker thread will be rescheduled
		with a sleep delay of one jiffy, between each
		rescan of the readers, for a grace period phase.

srcutree.srcu_retry_check_delay [KNL]
		Specifies number of microseconds of non-sleeping
		delay between each non-sleeping poll of readers.

srcutree.small_contention_lim [KNL]
		Specifies the number of update-side contention
		events per jiffy will be tolerated before
		initiating a conversion of an srcu_struct
		structure to big form.	Note that the value of
		srcutree.convert_to_big must have the 0x10 bit
		set for contention-based conversions to occur.

ssbd=		[ARM64,HW]
		Speculative Store Bypass Disable control

		On CPUs that are vulnerable to the Speculative
		Store Bypass vulnerability and offer a
		firmware based mitigation, this parameter
		indicates how the mitigation should be used:

		force-on:  Unconditionally enable mitigation for
			   for both kernel and userspace
		force-off: Unconditionally disable mitigation for
			   for both kernel and userspace
		kernel:    Always enable mitigation in the
			   kernel, and offer a prctl interface
			   to allow userspace to register its
			   interest in being mitigated too.

stack_guard_gap=	[MM]
		override the default stack gap protection. The value
		is in page units and it defines how many pages prior
		to (for stacks growing down) resp. after (for stacks
		growing up) the main stack are reserved for no other
		mapping. Default value is 256 pages.

stack_depot_disable= [KNL]
		Setting this to true through kernel command line will
		disable the stack depot thereby saving the static memory
		consumed by the stack hash table. By default this is set
		to false.

stacktrace	[FTRACE]
		Enabled the stack tracer on boot up.

stacktrace_filter=[function-list]
		[FTRACE] Limit the functions that the stack tracer
		will trace at boot up. function-list is a comma-separated
		list of functions. This list can be changed at run
		time by the stack_trace_filter file in the debugfs
		tracing directory. Note, this enables stack tracing
		and the stacktrace above is not needed.

sti=		[PARISC,HW]
		Format: <num>
		Set the STI (builtin display/keyboard on the HP-PARISC
		machines) console (graphic card) which should be used
		as the initial boot-console.
		See also comment in drivers/video/console/sticore.c.

sti_font=	[HW]
		See comment in drivers/video/console/sticore.c.

stifb=		[HW]
		Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]

       strict_sas_size=
		[X86]
		Format: <bool>
		Enable or disable strict sigaltstack size checks
		against the required signal frame size which
		depends on the supported FPU features. This can
		be used to filter out binaries which have
		not yet been made aware of AT_MINSIGSTKSZ.

stress_hpt	[PPC]
		Limits the number of kernel HPT entries in the hash
		page table to increase the rate of hash page table
		faults on kernel addresses.

stress_slb	[PPC]
		Limits the number of kernel SLB entries, and flushes
		them frequently to increase the rate of SLB faults
		on kernel addresses.

sunrpc.min_resvport=
sunrpc.max_resvport=
		[NFS,SUNRPC]
		SunRPC servers often require that client requests
		originate from a privileged port (i.e. a port in the
		range 0 < portnr < 1024).
		An administrator who wishes to reserve some of these
		ports for other uses may adjust the range that the
		kernel's sunrpc client considers to be privileged
		using these two parameters to set the minimum and
		maximum port values.

sunrpc.svc_rpc_per_connection_limit=
		[NFS,SUNRPC]
		Limit the number of requests that the server will
		process in parallel from a single connection.
		The default value is 0 (no limit).

sunrpc.pool_mode=
		[NFS]
		Control how the NFS server code allocates CPUs to
		service thread pools.  Depending on how many NICs
		you have and where their interrupts are bound, this
		option will affect which CPUs will do NFS serving.
		Note: this parameter cannot be changed while the
		NFS server is running.

		auto	    the server chooses an appropriate mode
			    automatically using heuristics
		global	    a single global pool contains all CPUs
		percpu	    one pool for each CPU
		pernode	    one pool for each NUMA node (equivalent
			    to global on non-NUMA machines)

sunrpc.tcp_slot_table_entries=
sunrpc.udp_slot_table_entries=
		[NFS,SUNRPC]
		Sets the upper limit on the number of simultaneous
		RPC calls that can be sent from the client to a
		server. Increasing these values may allow you to
		improve throughput, but will also increase the
		amount of memory reserved for use by the client.

suspend.pm_test_delay=
		[SUSPEND]
		Sets the number of seconds to remain in a suspend test
		mode before resuming the system (see
		/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
		is set. Default value is 5.

svm=		[PPC]
		Format: { on | off | y | n | 1 | 0 }
		This parameter controls use of the Protected
		Execution Facility on pSeries.

swiotlb=	[ARM,IA-64,PPC,MIPS,X86]
		Format: { <int> [,<int>] | force | noforce }
		<int> -- Number of I/O TLB slabs
		<int> -- Second integer after comma. Number of swiotlb
			 areas with their own lock. Will be rounded up
			 to a power of 2.
		force -- force using of bounce buffers even if they
		         wouldn't be automatically used by the kernel
		noforce -- Never use bounce buffers (for debugging)

switches=	[HW,M68k]

sysctl.*=	[KNL]
		Set a sysctl parameter, right before loading the init
		process, as if the value was written to the respective
		/proc/sys/... file. Both '.' and '/' are recognized as
		separators. Unrecognized parameters and invalid values
		are reported in the kernel log. Sysctls registered
		later by a loaded module cannot be set this way.
		Example: sysctl.vm.swappiness=40

sysrq_always_enabled
		[KNL]
		Ignore sysrq setting - this boot parameter will
		neutralize any effect of /proc/sys/kernel/sysrq.
		Useful for debugging.

tcpmhash_entries= [KNL,NET]
		Set the number of tcp_metrics_hash slots.
		Default value is 8192 or 16384 depending on total
		ram pages. This is used to specify the TCP metrics
		cache size. See Documentation/networking/ip-sysctl.rst
		"tcp_no_metrics_save" section for more details.

tdfx=		[HW,DRM]

test_suspend=	[SUSPEND]
		Format: { "mem" | "standby" | "freeze" }[,N]
		Specify "mem" (for Suspend-to-RAM) or "standby" (for
		standby suspend) or "freeze" (for suspend type freeze)
		as the system sleep state during system startup with
		the optional capability to repeat N number of times.
		The system is woken from this state using a
		wakeup-capable RTC alarm.

thash_entries=	[KNL,NET]
		Set number of hash buckets for TCP connection

thermal.act=	[HW,ACPI]
		-1: disable all active trip points in all thermal zones
		<degrees C>: override all lowest active trip points

thermal.crt=	[HW,ACPI]
		-1: disable all critical trip points in all thermal zones
		<degrees C>: override all critical trip points

thermal.off=	[HW,ACPI]
		1: disable ACPI thermal control

thermal.psv=	[HW,ACPI]
		-1: disable all passive trip points
		<degrees C>: override all passive trip points to this
		value

thermal.tzp=	[HW,ACPI]
		Specify global default ACPI thermal zone polling rate
		<deci-seconds>: poll all this frequency
		0: no polling (default)

threadirqs	[KNL]
		Force threading of all interrupt handlers except those
		marked explicitly IRQF_NO_THREAD.

topology=	[S390]
		Format: {off | on}
		Specify if the kernel should make use of the cpu
		topology information if the hardware supports this.
		The scheduler will make use of this information and
		e.g. base its process migration decisions on it.
		Default is on.

topology_updates= [KNL, PPC, NUMA]
		Format: {off}
		Specify if the kernel should ignore (off)
		topology updates sent by the hypervisor to this
		LPAR.

torture.disable_onoff_at_boot= [KNL]
		Prevent the CPU-hotplug component of torturing
		until after init has spawned.

torture.ftrace_dump_at_shutdown= [KNL]
		Dump the ftrace buffer at torture-test shutdown,
		even if there were no errors.  This can be a
		very costly operation when many torture tests
		are running concurrently, especially on systems
		with rotating-rust storage.

torture.verbose_sleep_frequency= [KNL]
		Specifies how many verbose printk()s should be
		emitted between each sleep.  The default of zero
		disables verbose-printk() sleeping.

torture.verbose_sleep_duration= [KNL]
		Duration of each verbose-printk() sleep in jiffies.

tp720=		[HW,PS2]

tpm_suspend_pcr=[HW,TPM]
		Format: integer pcr id
		Specify that at suspend time, the tpm driver
		should extend the specified pcr with zeros,
		as a workaround for some chips which fail to
		flush the last written pcr on TPM_SaveState.
		This will guarantee that all the other pcrs
		are saved.

tpm_tis.interrupts= [HW,TPM]
		Enable interrupts for the MMIO based physical layer
		for the FIFO interface. By default it is set to false
		(0). For more information about TPM hardware interfaces
		defined by Trusted Computing Group (TCG) see
		https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/

tp_printk	[FTRACE]
		Have the tracepoints sent to printk as well as the
		tracing ring buffer. This is useful for early boot up
		where the system hangs or reboots and does not give the
		option for reading the tracing buffer or performing a
		ftrace_dump_on_oops.

		To turn off having tracepoints sent to printk,
		 echo 0 > /proc/sys/kernel/tracepoint_printk
		Note, echoing 1 into this file without the
		tracepoint_printk kernel cmdline option has no effect.

		The tp_printk_stop_on_boot (see below) can also be used
		to stop the printing of events to console at
		late_initcall_sync.

		** CAUTION **

		Having tracepoints sent to printk() and activating high
		frequency tracepoints such as irq or sched, can cause
		the system to live lock.

tp_printk_stop_on_boot [FTRACE]
		When tp_printk (above) is set, it can cause a lot of noise
		on the console. It may be useful to only include the
		printing of events during boot up, as user space may
		make the system inoperable.

		This command line option will stop the printing of events
		to console at the late_initcall_sync() time frame.

trace_buf_size=nn[KMG]
		[FTRACE] will set tracing buffer size on each cpu.

trace_clock=	[FTRACE] Set the clock used for tracing events
		at boot up.
		local - Use the per CPU time stamp counter
			(converted into nanoseconds). Fast, but
			depending on the architecture, may not be
			in sync between CPUs.
		global - Event time stamps are synchronize across
			CPUs. May be slower than the local clock,
			but better for some race conditions.
		counter - Simple counting of events (1, 2, ..)
			note, some counts may be skipped due to the
			infrastructure grabbing the clock more than
			once per event.
		uptime - Use jiffies as the time stamp.
		perf - Use the same clock that perf uses.
		mono - Use ktime_get_mono_fast_ns() for time stamps.
		mono_raw - Use ktime_get_raw_fast_ns() for time
			stamps.
		boot - Use ktime_get_boot_fast_ns() for time stamps.
		Architectures may add more clocks. See
		Documentation/trace/ftrace.rst for more details.

trace_event=[event-list]
		[FTRACE] Set and start specified trace events in order
		to facilitate early boot debugging. The event-list is a
		comma-separated list of trace events to enable. See
		also Documentation/trace/events.rst

trace_instance=[instance-info]
		[FTRACE] Create a ring buffer instance early in boot up.
		This will be listed in:

			/sys/kernel/tracing/instances

		Events can be enabled at the time the instance is created
		via:

			trace_instance=<name>,<system1>:<event1>,<system2>:<event2>

		Note, the "<system*>:" portion is optional if the event is
		unique.

			trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall

		will enable the "sched_switch" event (note, the "sched:" is optional, and
		the same thing would happen if it was left off). The irq_handler_entry
		event, and all events under the "initcall" system.

trace_options=[option-list]
		[FTRACE] Enable or disable tracer options at boot.
		The option-list is a comma delimited list of options
		that can be enabled or disabled just as if you were
		to echo the option name into

		    /sys/kernel/tracing/trace_options

		For example, to enable stacktrace option (to dump the
		stack trace of each event), add to the command line:

		      trace_options=stacktrace

		See also Documentation/trace/ftrace.rst "trace options"
		section.

trace_trigger=[trigger-list]
		[FTRACE] Add a event trigger on specific events.
		Set a trigger on top of a specific event, with an optional
		filter.

		The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
		Where more than one trigger may be specified that are comma deliminated.

		For example:

		  trace_trigger="sched_switch.stacktrace if prev_state == 2"

		The above will enable the "stacktrace" trigger on the "sched_switch"
		event but only trigger it if the "prev_state" of the "sched_switch"
		event is "2" (TASK_UNINTERUPTIBLE).

		See also "Event triggers" in Documentation/trace/events.rst


traceoff_on_warning
		[FTRACE] enable this option to disable tracing when a
		warning is hit. This turns off "tracing_on". Tracing can
		be enabled again by echoing '1' into the "tracing_on"
		file located in /sys/kernel/tracing/

		This option is useful, as it disables the trace before
		the WARNING dump is called, which prevents the trace to
		be filled with content caused by the warning output.

		This option can also be set at run time via the sysctl
		option:  kernel/traceoff_on_warning

transparent_hugepage=
		[KNL]
		Format: [always|madvise|never]
		Can be used to control the default behavior of the system
		with respect to transparent hugepages.
		See Documentation/admin-guide/mm/transhuge.rst
		for more details.

trusted.source=	[KEYS]
		Format: <string>
		This parameter identifies the trust source as a backend
		for trusted keys implementation. Supported trust
		sources:
		- "tpm"
		- "tee"
		- "caam"
		If not specified then it defaults to iterating through
		the trust source list starting with TPM and assigns the
		first trust source as a backend which is initialized
		successfully during iteration.

trusted.rng=	[KEYS]
		Format: <string>
		The RNG used to generate key material for trusted keys.
		Can be one of:
		- "kernel"
		- the same value as trusted.source: "tpm" or "tee"
		- "default"
		If not specified, "default" is used. In this case,
		the RNG's choice is left to each individual trust source.

tsc=		Disable clocksource stability checks for TSC.
		Format: <string>
		[x86] reliable: mark tsc clocksource as reliable, this
		disables clocksource verification at runtime, as well
		as the stability checks done at bootup.	Used to enable
		high-resolution timer mode on older hardware, and in
		virtualized environment.
		[x86] noirqtime: Do not use TSC to do irq accounting.
		Used to run time disable IRQ_TIME_ACCOUNTING on any
		platforms where RDTSC is slow and this accounting
		can add overhead.
		[x86] unstable: mark the TSC clocksource as unstable, this
		marks the TSC unconditionally unstable at bootup and
		avoids any further wobbles once the TSC watchdog notices.
		[x86] nowatchdog: disable clocksource watchdog. Used
		in situations with strict latency requirements (where
		interruptions from clocksource watchdog are not
		acceptable).
		[x86] recalibrate: force recalibration against a HW timer
		(HPET or PM timer) on systems whose TSC frequency was
		obtained from HW or FW using either an MSR or CPUID(0x15).
		Warn if the difference is more than 500 ppm.
		[x86] watchdog: Use TSC as the watchdog clocksource with
		which to check other HW timers (HPET or PM timer), but
		only on systems where TSC has been deemed trustworthy.
		This will be suppressed by an earlier tsc=nowatchdog and
		can be overridden by a later tsc=nowatchdog.  A console
		message will flag any such suppression or overriding.

tsc_early_khz=  [X86] Skip early TSC calibration and use the given
		value instead. Useful when the early TSC frequency discovery
		procedure is not reliable, such as on overclocked systems
		with CPUID.16h support and partial CPUID.15h support.
		Format: <unsigned int>

tsx=		[X86] Control Transactional Synchronization
		Extensions (TSX) feature in Intel processors that
		support TSX control.

		This parameter controls the TSX feature. The options are:

		on	- Enable TSX on the system. Although there are
			mitigations for all known security vulnerabilities,
			TSX has been known to be an accelerator for
			several previous speculation-related CVEs, and
			so there may be unknown	security risks associated
			with leaving it enabled.

		off	- Disable TSX on the system. (Note that this
			option takes effect only on newer CPUs which are
			not vulnerable to MDS, i.e., have
			MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
			the new IA32_TSX_CTRL MSR through a microcode
			update. This new MSR allows for the reliable
			deactivation of the TSX functionality.)

		auto	- Disable TSX if X86_BUG_TAA is present,
			  otherwise enable TSX on the system.

		Not specifying this option is equivalent to tsx=off.

		See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
		for more details.

tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
		Abort (TAA) vulnerability.

		Similar to Micro-architectural Data Sampling (MDS)
		certain CPUs that support Transactional
		Synchronization Extensions (TSX) 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 TAA mitigation.  The
		options are:

		full       - Enable TAA mitigation on vulnerable CPUs
			     if TSX is enabled.

		full,nosmt - Enable TAA mitigation and disable SMT on
			     vulnerable CPUs. If TSX is disabled, SMT
			     is not disabled because CPU is not
			     vulnerable to cross-thread TAA attacks.
		off        - Unconditionally disable TAA mitigation

		On MDS-affected machines, tsx_async_abort=off can be
		prevented by an active MDS mitigation as both vulnerabilities
		are mitigated with the same mechanism so in order to disable
		this mitigation, you need to specify mds=off too.

		Not specifying this option is equivalent to
		tsx_async_abort=full.  On CPUs which are MDS affected
		and deploy MDS mitigation, TAA mitigation is not
		required and doesn't provide any additional
		mitigation.

		For details see:
		Documentation/admin-guide/hw-vuln/tsx_async_abort.rst

turbografx.map[2|3]=	[HW,JOY]
		TurboGraFX parallel port interface
		Format:
		<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
		See also Documentation/input/devices/joystick-parport.rst

udbg-immortal	[PPC] When debugging early kernel crashes that
		happen after console_init() and before a proper
		console driver takes over, this boot options might
		help "seeing" what's going on.

uhash_entries=	[KNL,NET]
		Set number of hash buckets for UDP/UDP-Lite connections

uhci-hcd.ignore_oc=
		[USB] Ignore overcurrent events (default N).
		Some badly-designed motherboards generate lots of
		bogus events, for ports that aren't wired to
		anything.  Set this parameter to avoid log spamming.
		Note that genuine overcurrent events won't be
		reported either.

unknown_nmi_panic
		[X86] Cause panic on unknown NMI.

unwind_debug	[X86-64]
		Enable unwinder debug output.  This can be
		useful for debugging certain unwinder error
		conditions, including corrupt stacks and
		bad/missing unwinder metadata.

usbcore.authorized_default=
		[USB] Default USB device authorization:
		(default -1 = authorized (same as 1),
		0 = not authorized, 1 = authorized, 2 = authorized
		if device connected to internal port)

usbcore.autosuspend=
		[USB] The autosuspend time delay (in seconds) used
		for newly-detected USB devices (default 2).  This
		is the time required before an idle device will be
		autosuspended.  Devices for which the delay is set
		to a negative value won't be autosuspended at all.

usbcore.usbfs_snoop=
		[USB] Set to log all usbfs traffic (default 0 = off).

usbcore.usbfs_snoop_max=
		[USB] Maximum number of bytes to snoop in each URB
		(default = 65536).

usbcore.blinkenlights=
		[USB] Set to cycle leds on hubs (default 0 = off).

usbcore.old_scheme_first=
		[USB] Start with the old device initialization
		scheme (default 0 = off).

usbcore.usbfs_memory_mb=
		[USB] Memory limit (in MB) for buffers allocated by
		usbfs (default = 16, 0 = max = 2047).

usbcore.use_both_schemes=
		[USB] Try the other device initialization scheme
		if the first one fails (default 1 = enabled).

usbcore.initial_descriptor_timeout=
		[USB] Specifies timeout for the initial 64-byte
		USB_REQ_GET_DESCRIPTOR request in milliseconds
		(default 5000 = 5.0 seconds).

usbcore.nousb	[USB] Disable the USB subsystem

usbcore.quirks=
		[USB] A list of quirk entries to augment the built-in
		usb core quirk list. List entries are separated by
		commas. Each entry has the form
		VendorID:ProductID:Flags. The IDs are 4-digit hex
		numbers and Flags is a set of letters. Each letter
		will change the built-in quirk; setting it if it is
		clear and clearing it if it is set. The letters have
		the following meanings:
			a = USB_QUIRK_STRING_FETCH_255 (string
				descriptors must not be fetched using
				a 255-byte read);
			b = USB_QUIRK_RESET_RESUME (device can't resume
				correctly so reset it instead);
			c = USB_QUIRK_NO_SET_INTF (device can't handle
				Set-Interface requests);
			d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
				handle its Configuration or Interface
				strings);
			e = USB_QUIRK_RESET (device can't be reset
				(e.g morph devices), don't use reset);
			f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
				more interface descriptions than the
				bNumInterfaces count, and can't handle
				talking to these interfaces);
			g = USB_QUIRK_DELAY_INIT (device needs a pause
				during initialization, after we read
				the device descriptor);
			h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
				high speed and super speed interrupt
				endpoints, the USB 2.0 and USB 3.0 spec
				require the interval in microframes (1
				microframe = 125 microseconds) to be
				calculated as interval = 2 ^
				(bInterval-1).
				Devices with this quirk report their
				bInterval as the result of this
				calculation instead of the exponent
				variable used in the calculation);
			i = USB_QUIRK_DEVICE_QUALIFIER (device can't
				handle device_qualifier descriptor
				requests);
			j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
				generates spurious wakeup, ignore
				remote wakeup capability);
			k = USB_QUIRK_NO_LPM (device can't handle Link
				Power Management);
			l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
				(Device reports its bInterval as linear
				frames instead of the USB 2.0
				calculation);
			m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
				to be disconnected before suspend to
				prevent spurious wakeup);
			n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
				pause after every control message);
			o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
				delay after resetting its port);
		Example: quirks=0781:5580:bk,0a5c:5834:gij

usbhid.mousepoll=
		[USBHID] The interval which mice are to be polled at.

usbhid.jspoll=
		[USBHID] The interval which joysticks are to be polled at.

usbhid.kbpoll=
		[USBHID] The interval which keyboards are to be polled at.

usb-storage.delay_use=
		[UMS] The delay in seconds before a new device is
		scanned for Logical Units (default 1).

usb-storage.quirks=
		[UMS] A list of quirks entries to supplement or
		override the built-in unusual_devs list.  List
		entries are separated by commas.  Each entry has
		the form VID:PID:Flags where VID and PID are Vendor
		and Product ID values (4-digit hex numbers) and
		Flags is a set of characters, each corresponding
		to a common usb-storage quirk flag as follows:
			a = SANE_SENSE (collect more than 18 bytes
				of sense data, not on uas);
			b = BAD_SENSE (don't collect more than 18
				bytes of sense data, not on uas);
			c = FIX_CAPACITY (decrease the reported
				device capacity by one sector);
			d = NO_READ_DISC_INFO (don't use
				READ_DISC_INFO command, not on uas);
			e = NO_READ_CAPACITY_16 (don't use
				READ_CAPACITY_16 command);
			f = NO_REPORT_OPCODES (don't use report opcodes
				command, uas only);
			g = MAX_SECTORS_240 (don't transfer more than
				240 sectors at a time, uas only);
			h = CAPACITY_HEURISTICS (decrease the
				reported device capacity by one
				sector if the number is odd);
			i = IGNORE_DEVICE (don't bind to this
				device);
			j = NO_REPORT_LUNS (don't use report luns
				command, uas only);
			k = NO_SAME (do not use WRITE_SAME, uas only)
			l = NOT_LOCKABLE (don't try to lock and
				unlock ejectable media, not on uas);
			m = MAX_SECTORS_64 (don't transfer more
				than 64 sectors = 32 KB at a time,
				not on uas);
			n = INITIAL_READ10 (force a retry of the
				initial READ(10) command, not on uas);
			o = CAPACITY_OK (accept the capacity
				reported by the device, not on uas);
			p = WRITE_CACHE (the device cache is ON
				by default, not on uas);
			r = IGNORE_RESIDUE (the device reports
				bogus residue values, not on uas);
			s = SINGLE_LUN (the device has only one
				Logical Unit);
			t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
				commands, uas only);
			u = IGNORE_UAS (don't bind to the uas driver);
			w = NO_WP_DETECT (don't test whether the
				medium is write-protected).
			y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
				even if the device claims no cache,
				not on uas)
		Example: quirks=0419:aaf5:rl,0421:0433:rc

user_debug=	[KNL,ARM]
		Format: <int>
		See arch/arm/Kconfig.debug help text.
			 1 - undefined instruction events
			 2 - system calls
			 4 - invalid data aborts
			 8 - SIGSEGV faults
			16 - SIGBUS faults
		Example: user_debug=31

userpte=
		[X86] Flags controlling user PTE allocations.

			nohigh = do not allocate PTE pages in
				HIGHMEM regardless of setting
				of CONFIG_HIGHPTE.

vdso=		[X86,SH,SPARC]
		On X86_32, this is an alias for vdso32=.  Otherwise:

		vdso=1: enable VDSO (the default)
		vdso=0: disable VDSO mapping

vdso32=		[X86] Control the 32-bit vDSO
		vdso32=1: enable 32-bit VDSO
		vdso32=0 or vdso32=2: disable 32-bit VDSO

		See the help text for CONFIG_COMPAT_VDSO for more
		details.  If CONFIG_COMPAT_VDSO is set, the default is
		vdso32=0; otherwise, the default is vdso32=1.

		For compatibility with older kernels, vdso32=2 is an
		alias for vdso32=0.

		Try vdso32=0 if you encounter an error that says:
		dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!

vector=		[IA-64,SMP]
		vector=percpu: enable percpu vector domain

video=		[FB] Frame buffer configuration
		See Documentation/fb/modedb.rst.

video.brightness_switch_enabled= [ACPI]
		Format: [0|1]
		If set to 1, on receiving an ACPI notify event
		generated by hotkey, video driver will adjust brightness
		level and then send out the event to user space through
		the allocated input device. If set to 0, video driver
		will only send out the event without touching backlight
		brightness level.
		default: 1

virtio_mmio.device=
		[VMMIO] Memory mapped virtio (platform) device.

			<size>@<baseaddr>:<irq>[:<id>]
		where:
			<size>     := size (can use standard suffixes
					like K, M and G)
			<baseaddr> := physical base address
			<irq>      := interrupt number (as passed to
					request_irq())
			<id>       := (optional) platform device id
		example:
			virtio_mmio.device=1K@0x100b0000:48:7

		Can be used multiple times for multiple devices.

vga=		[BOOT,X86-32] Select a particular video mode
		See Documentation/arch/x86/boot.rst and
		Documentation/admin-guide/svga.rst.
		Use vga=ask for menu.
		This is actually a boot loader parameter; the value is
		passed to the kernel using a special protocol.

vm_debug[=options]	[KNL] Available with CONFIG_DEBUG_VM=y.
		May slow down system boot speed, especially when
		enabled on systems with a large amount of memory.
		All options are enabled by default, and this
		interface is meant to allow for selectively
		enabling or disabling specific virtual memory
		debugging features.

		Available options are:
		  P	Enable page structure init time poisoning
		  -	Disable all of the above options

vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
		size of <nn>. This can be used to increase the
		minimum size (128MB on x86). It can also be used to
		decrease the size and leave more room for directly
		mapped kernel RAM.

vmcp_cma=nn[MG]	[KNL,S390]
		Sets the memory size reserved for contiguous memory
		allocations for the vmcp device driver.

vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
		Format: <command>

vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
		Format: <command>

vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
		Format: <command>

vsyscall=	[X86-64]
		Controls the behavior of vsyscalls (i.e. calls to
		fixed addresses of 0xffffffffff600x00 from legacy
		code).  Most statically-linked binaries and older
		versions of glibc use these calls.  Because these
		functions are at fixed addresses, they make nice
		targets for exploits that can control RIP.

		emulate     Vsyscalls turn into traps and are emulated
		            reasonably safely.  The vsyscall page is
			    readable.

		xonly       [default] Vsyscalls turn into traps and are
		            emulated reasonably safely.  The vsyscall
			    page is not readable.

		none        Vsyscalls don't work at all.  This makes
		            them quite hard to use for exploits but
		            might break your system.

vt.color=	[VT] Default text color.
		Format: 0xYX, X = foreground, Y = background.
		Default: 0x07 = light gray on black.

vt.cur_default=	[VT] Default cursor shape.
		Format: 0xCCBBAA, where AA, BB, and CC are the same as
		the parameters of the <Esc>[?A;B;Cc escape sequence;
		see VGA-softcursor.txt. Default: 2 = underline.

vt.default_blu=	[VT]
		Format: <blue0>,<blue1>,<blue2>,...,<blue15>
		Change the default blue palette of the console.
		This is a 16-member array composed of values
		ranging from 0-255.

vt.default_grn=	[VT]
		Format: <green0>,<green1>,<green2>,...,<green15>
		Change the default green palette of the console.
		This is a 16-member array composed of values
		ranging from 0-255.

vt.default_red=	[VT]
		Format: <red0>,<red1>,<red2>,...,<red15>
		Change the default red palette of the console.
		This is a 16-member array composed of values
		ranging from 0-255.

vt.default_utf8=
		[VT]
		Format=<0|1>
		Set system-wide default UTF-8 mode for all tty's.
		Default is 1, i.e. UTF-8 mode is enabled for all
		newly opened terminals.

vt.global_cursor_default=
		[VT]
		Format=<-1|0|1>
		Set system-wide default for whether a cursor
		is shown on new VTs. Default is -1,
		i.e. cursors will be created by default unless
		overridden by individual drivers. 0 will hide
		cursors, 1 will display them.

vt.italic=	[VT] Default color for italic text; 0-15.
		Default: 2 = green.

vt.underline=	[VT] Default color for underlined text; 0-15.
		Default: 3 = cyan.

watchdog timers	[HW,WDT] For information on watchdog timers,
		see Documentation/watchdog/watchdog-parameters.rst
		or other driver-specific files in the
		Documentation/watchdog/ directory.

watchdog_thresh=
		[KNL]
		Set the hard lockup detector stall duration
		threshold in seconds. The soft lockup detector
		threshold is set to twice the value. A value of 0
		disables both lockup detectors. Default is 10
		seconds.

workqueue.unbound_cpus=
		[KNL,SMP] Specify to constrain one or some CPUs
		to use in unbound workqueues.
		Format: <cpu-list>
		By default, all online CPUs are available for
		unbound workqueues.

workqueue.watchdog_thresh=
		If CONFIG_WQ_WATCHDOG is configured, workqueue can
		warn stall conditions and dump internal state to
		help debugging.  0 disables workqueue stall
		detection; otherwise, it's the stall threshold
		duration in seconds.  The default value is 30 and
		it can be updated at runtime by writing to the
		corresponding sysfs file.

workqueue.cpu_intensive_thresh_us=
		Per-cpu work items which run for longer than this
		threshold are automatically considered CPU intensive
		and excluded from concurrency management to prevent
		them from noticeably delaying other per-cpu work
		items. Default is 10000 (10ms).

		If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
		will report the work functions which violate this
		threshold repeatedly. They are likely good
		candidates for using WQ_UNBOUND workqueues instead.

workqueue.power_efficient
		Per-cpu workqueues are generally preferred because
		they show better performance thanks to cache
		locality; unfortunately, per-cpu workqueues tend to
		be more power hungry than unbound workqueues.

		Enabling this makes the per-cpu workqueues which
		were observed to contribute significantly to power
		consumption unbound, leading to measurably lower
		power usage at the cost of small performance
		overhead.

		The default value of this parameter is determined by
		the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.

       workqueue.default_affinity_scope=
		Select the default affinity scope to use for unbound
		workqueues. Can be one of "cpu", "smt", "cache",
		"numa" and "system". Default is "cache". For more
		information, see the Affinity Scopes section in
		Documentation/core-api/workqueue.rst.

		This can be changed after boot by writing to the
		matching /sys/module/workqueue/parameters file. All
		workqueues with the "default" affinity scope will be
		updated accordignly.

workqueue.debug_force_rr_cpu
		Workqueue used to implicitly guarantee that work
		items queued without explicit CPU specified are put
		on the local CPU.  This guarantee is no longer true
		and while local CPU is still preferred work items
		may be put on foreign CPUs.  This debug option
		forces round-robin CPU selection to flush out
		usages which depend on the now broken guarantee.
		When enabled, memory and cache locality will be
		impacted.

writecombine=	[LOONGARCH] Control the MAT (Memory Access Type) of
		ioremap_wc().

		on   - Enable writecombine, use WUC for ioremap_wc()
		off  - Disable writecombine, use SUC for ioremap_wc()

x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
		default x2apic cluster mode on platforms
		supporting x2apic.

xen_512gb_limit		[KNL,X86-64,XEN]
		Restricts the kernel running paravirtualized under Xen
		to use only up to 512 GB of RAM. The reason to do so is
		crash analysis tools and Xen tools for doing domain
		save/restore/migration must be enabled to handle larger
		domains.

xen_emul_unplug=		[HW,X86,XEN]
		Unplug Xen emulated devices
		Format: [unplug0,][unplug1]
		ide-disks -- unplug primary master IDE devices
		aux-ide-disks -- unplug non-primary-master IDE devices
		nics -- unplug network devices
		all -- unplug all emulated devices (NICs and IDE disks)
		unnecessary -- unplugging emulated devices is
			unnecessary even if the host did not respond to
			the unplug protocol
		never -- do not unplug even if version check succeeds

xen_legacy_crash	[X86,XEN]
		Crash from Xen panic notifier, without executing late
		panic() code such as dumping handler.

xen_msr_safe=	[X86,XEN]
		Format: <bool>
		Select whether to always use non-faulting (safe) MSR
		access functions when running as Xen PV guest. The
		default value is controlled by CONFIG_XEN_PV_MSR_SAFE.

xen_nopvspin	[X86,XEN]
		Disables the qspinlock slowpath using Xen PV optimizations.
		This parameter is obsoleted by "nopvspin" parameter, which
		has equivalent effect for XEN platform.

xen_nopv	[X86]
		Disables the PV optimizations forcing the HVM guest to
		run as generic HVM guest with no PV drivers.
		This option is obsoleted by the "nopv" option, which
		has equivalent effect for XEN platform.

xen_no_vector_callback
		[KNL,X86,XEN] Disable the vector callback for Xen
		event channel interrupts.

xen_scrub_pages=	[XEN]
		Boolean option to control scrubbing pages before giving them back
		to Xen, for use by other domains. Can be also changed at runtime
		with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
		Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.

xen_timer_slop=	[X86-64,XEN]
		Set the timer slop (in nanoseconds) for the virtual Xen
		timers (default is 100000). This adjusts the minimum
		delta of virtualized Xen timers, where lower values
		improve timer resolution at the expense of processing
		more timer interrupts.

xen.balloon_boot_timeout= [XEN]
		The time (in seconds) to wait before giving up to boot
		in case initial ballooning fails to free enough memory.
		Applies only when running as HVM or PVH guest and
		started with less memory configured than allowed at
		max. Default is 180.

xen.event_eoi_delay=	[XEN]
		How long to delay EOI handling in case of event
		storms (jiffies). Default is 10.

xen.event_loop_timeout=	[XEN]
		After which time (jiffies) the event handling loop
		should start to delay EOI handling. Default is 2.

xen.fifo_events=	[XEN]
		Boolean parameter to disable using fifo event handling
		even if available. Normally fifo event handling is
		preferred over the 2-level event handling, as it is
		fairer and the number of possible event channels is
		much higher. Default is on (use fifo events).

xirc2ps_cs=	[NET,PCMCIA]
		Format:
		<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]

xive=		[PPC]
		By default on POWER9 and above, the kernel will
		natively use the XIVE interrupt controller. This option
		allows the fallback firmware mode to be used:

		off       Fallback to firmware control of XIVE interrupt
			  controller on both pseries and powernv
			  platforms. Only useful on POWER9 and above.

xive.store-eoi=off	[PPC]
		By default on POWER10 and above, the kernel will use
		stores for EOI handling when the XIVE interrupt mode
		is active. This option allows the XIVE driver to use
		loads instead, as on POWER9.

xhci-hcd.quirks		[USB,KNL]
		A hex value specifying bitmask with supplemental xhci
		host controller quirks. Meaning of each bit can be
		consulted in header drivers/usb/host/xhci.h.

xmon		[PPC]
		Format: { early | on | rw | ro | off }
		Controls if xmon debugger is enabled. Default is off.
		Passing only "xmon" is equivalent to "xmon=early".
		early	Call xmon as early as possible on boot; xmon
			debugger is called from setup_arch().
		on	xmon debugger hooks will be installed so xmon
			is only called on a kernel crash. Default mode,
			i.e. either "ro" or "rw" mode, is controlled
			with CONFIG_XMON_DEFAULT_RO_MODE.
		rw	xmon debugger hooks will be installed so xmon
			is called only on a kernel crash, mode is write,
			meaning SPR registers, memory and, other data
			can be written using xmon commands.
		ro 	same as "rw" option above but SPR registers,
			memory, and other data can't be written using
			xmon commands.
		off	xmon is disabled.