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Based on kernel version 4.8. Page generated on 2016-10-06 23:16 EST.

1	                          Kernel Parameters
2	                          ~~~~~~~~~~~~~~~~~
4	The following is a consolidated list of the kernel parameters as
5	implemented by the __setup(), core_param() and module_param() macros
6	and sorted into English Dictionary order (defined as ignoring all
7	punctuation and sorting digits before letters in a case insensitive
8	manner), and with descriptions where known.
10	The kernel parses parameters from the kernel command line up to "--";
11	if it doesn't recognize a parameter and it doesn't contain a '.', the
12	parameter gets passed to init: parameters with '=' go into init's
13	environment, others are passed as command line arguments to init.
14	Everything after "--" is passed as an argument to init.
16	Module parameters can be specified in two ways: via the kernel command
17	line with a module name prefix, or via modprobe, e.g.:
19		(kernel command line) usbcore.blinkenlights=1
20		(modprobe command line) modprobe usbcore blinkenlights=1
22	Parameters for modules which are built into the kernel need to be
23	specified on the kernel command line.  modprobe looks through the
24	kernel command line (/proc/cmdline) and collects module parameters
25	when it loads a module, so the kernel command line can be used for
26	loadable modules too.
28	Hyphens (dashes) and underscores are equivalent in parameter names, so
29		log_buf_len=1M print-fatal-signals=1
30	can also be entered as
31		log-buf-len=1M print_fatal_signals=1
33	Double-quotes can be used to protect spaces in values, e.g.:
34		param="spaces in here"
36	This document may not be entirely up to date and comprehensive. The command
37	"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38	module. Loadable modules, after being loaded into the running kernel, also
39	reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40	parameters may be changed at runtime by the command
41	"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43	The parameters listed below are only valid if certain kernel build options were
44	enabled and if respective hardware is present. The text in square brackets at
45	the beginning of each description states the restrictions within which a
46	parameter is applicable:
48		ACPI	ACPI support is enabled.
49		AGP	AGP (Accelerated Graphics Port) is enabled.
50		ALSA	ALSA sound support is enabled.
51		APIC	APIC support is enabled.
52		APM	Advanced Power Management support is enabled.
53		ARM	ARM architecture is enabled.
54		AVR32	AVR32 architecture is enabled.
55		AX25	Appropriate AX.25 support is enabled.
56		BLACKFIN Blackfin architecture is enabled.
57		CLK	Common clock infrastructure is enabled.
58		CMA	Contiguous Memory Area support is enabled.
59		DRM	Direct Rendering Management support is enabled.
60		DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61		EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
62		EFI	EFI Partitioning (GPT) is enabled
63		EIDE	EIDE/ATAPI support is enabled.
64		EVM	Extended Verification Module
65		FB	The frame buffer device is enabled.
66		FTRACE	Function tracing enabled.
67		GCOV	GCOV profiling is enabled.
68		HW	Appropriate hardware is enabled.
69		IA-64	IA-64 architecture is enabled.
70		IMA     Integrity measurement architecture is enabled.
71		IOSCHED	More than one I/O scheduler is enabled.
72		IP_PNP	IP DHCP, BOOTP, or RARP is enabled.
73		IPV6	IPv6 support is enabled.
74		ISAPNP	ISA PnP code is enabled.
75		ISDN	Appropriate ISDN support is enabled.
76		JOY	Appropriate joystick support is enabled.
77		KGDB	Kernel debugger support is enabled.
78		KVM	Kernel Virtual Machine support is enabled.
79		LIBATA  Libata driver is enabled
80		LP	Printer support is enabled.
81		LOOP	Loopback device support is enabled.
82		M68k	M68k architecture is enabled.
83				These options have more detailed description inside of
84				Documentation/m68k/kernel-options.txt.
85		MDA	MDA console support is enabled.
86		MIPS	MIPS architecture is enabled.
87		MOUSE	Appropriate mouse support is enabled.
88		MSI	Message Signaled Interrupts (PCI).
89		MTD	MTD (Memory Technology Device) support is enabled.
90		NET	Appropriate network support is enabled.
91		NUMA	NUMA support is enabled.
92		NFS	Appropriate NFS support is enabled.
93		OSS	OSS sound support is enabled.
94		PV_OPS	A paravirtualized kernel is enabled.
95		PARIDE	The ParIDE (parallel port IDE) subsystem is enabled.
96		PARISC	The PA-RISC architecture is enabled.
97		PCI	PCI bus support is enabled.
98		PCIE	PCI Express support is enabled.
99		PCMCIA	The PCMCIA subsystem is enabled.
100		PNP	Plug & Play support is enabled.
101		PPC	PowerPC architecture is enabled.
102		PPT	Parallel port support is enabled.
103		PS2	Appropriate PS/2 support is enabled.
104		RAM	RAM disk support is enabled.
105		S390	S390 architecture is enabled.
106		SCSI	Appropriate SCSI support is enabled.
107				A lot of drivers have their options described inside
108				the Documentation/scsi/ sub-directory.
109		SECURITY Different security models are enabled.
110		SELINUX SELinux support is enabled.
111		APPARMOR AppArmor support is enabled.
112		SERIAL	Serial support is enabled.
113		SH	SuperH architecture is enabled.
114		SMP	The kernel is an SMP kernel.
115		SPARC	Sparc architecture is enabled.
116		SWSUSP	Software suspend (hibernation) is enabled.
117		SUSPEND	System suspend states are enabled.
118		TPM	TPM drivers are enabled.
119		TS	Appropriate touchscreen support is enabled.
120		UMS	USB Mass Storage support is enabled.
121		USB	USB support is enabled.
122		USBHID	USB Human Interface Device support is enabled.
123		V4L	Video For Linux support is enabled.
124		VMMIO   Driver for memory mapped virtio devices is enabled.
125		VGA	The VGA console has been enabled.
126		VT	Virtual terminal support is enabled.
127		WDT	Watchdog support is enabled.
128		XT	IBM PC/XT MFM hard disk support is enabled.
129		X86-32	X86-32, aka i386 architecture is enabled.
130		X86-64	X86-64 architecture is enabled.
131				More X86-64 boot options can be found in
132				Documentation/x86/x86_64/boot-options.txt .
133		X86	Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134		X86_UV	SGI UV support is enabled.
135		XEN	Xen support is enabled
137	In addition, the following text indicates that the option:
139		BUGS=	Relates to possible processor bugs on the said processor.
140		KNL	Is a kernel start-up parameter.
141		BOOT	Is a boot loader parameter.
143	Parameters denoted with BOOT are actually interpreted by the boot
144	loader, and have no meaning to the kernel directly.
145	Do not modify the syntax of boot loader parameters without extreme
146	need or coordination with <Documentation/x86/boot.txt>.
148	There are also arch-specific kernel-parameters not documented here.
149	See for example <Documentation/x86/x86_64/boot-options.txt>.
151	Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
152	a trailing = on the name of any parameter states that that parameter will
153	be entered as an environment variable, whereas its absence indicates that
154	it will appear as a kernel argument readable via /proc/cmdline by programs
155	running once the system is up.
157	The number of kernel parameters is not limited, but the length of the
158	complete command line (parameters including spaces etc.) is limited to
159	a fixed number of characters. This limit depends on the architecture
160	and is between 256 and 4096 characters. It is defined in the file
161	./include/asm/setup.h as COMMAND_LINE_SIZE.
163	Finally, the [KMG] suffix is commonly described after a number of kernel
164	parameter values. These 'K', 'M', and 'G' letters represent the _binary_
165	multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
166	bytes respectively. Such letter suffixes can also be entirely omitted.
169		acpi=		[HW,ACPI,X86,ARM64]
170				Advanced Configuration and Power Interface
171				Format: { force | on | off | strict | noirq | rsdt |
172					  copy_dsdt }
173				force -- enable ACPI if default was off
174				on -- enable ACPI but allow fallback to DT [arm64]
175				off -- disable ACPI if default was on
176				noirq -- do not use ACPI for IRQ routing
177				strict -- Be less tolerant of platforms that are not
178					strictly ACPI specification compliant.
179				rsdt -- prefer RSDT over (default) XSDT
180				copy_dsdt -- copy DSDT to memory
181				For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
182				are available
184				See also Documentation/power/runtime_pm.txt, pci=noacpi
186		acpi_apic_instance=	[ACPI, IOAPIC]
187				Format: <int>
188				2: use 2nd APIC table, if available
189				1,0: use 1st APIC table
190				default: 0
192		acpi_backlight=	[HW,ACPI]
193				acpi_backlight=vendor
194				acpi_backlight=video
195				If set to vendor, prefer vendor specific driver
196				(e.g. thinkpad_acpi, sony_acpi, etc.) instead
197				of the ACPI video.ko driver.
199		acpi_force_32bit_fadt_addr
200				force FADT to use 32 bit addresses rather than the
201				64 bit X_* addresses. Some firmware have broken 64
202				bit addresses for force ACPI ignore these and use
203				the older legacy 32 bit addresses.
205		acpica_no_return_repair [HW, ACPI]
206				Disable AML predefined validation mechanism
207				This mechanism can repair the evaluation result to make
208				the return objects more ACPI specification compliant.
209				This option is useful for developers to identify the
210				root cause of an AML interpreter issue when the issue
211				has something to do with the repair mechanism.
213		acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
214		acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
215				Format: <int>
216				CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
217				debug output.  Bits in debug_layer correspond to a
218				_COMPONENT in an ACPI source file, e.g.,
220				Bits in debug_level correspond to a level in
221				ACPI_DEBUG_PRINT statements, e.g.,
223				The debug_level mask defaults to "info".  See
224				Documentation/acpi/debug.txt for more information about
225				debug layers and levels.
227				Enable processor driver info messages:
228				    acpi.debug_layer=0x20000000
229				Enable PCI/PCI interrupt routing info messages:
230				    acpi.debug_layer=0x400000
231				Enable AML "Debug" output, i.e., stores to the Debug
232				object while interpreting AML:
233				    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
234				Enable all messages related to ACPI hardware:
235				    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
237				Some values produce so much output that the system is
238				unusable.  The "log_buf_len" parameter may be useful
239				if you need to capture more output.
241		acpi_enforce_resources=	[ACPI]
242				{ strict | lax | no }
243				Check for resource conflicts between native drivers
244				and ACPI OperationRegions (SystemIO and SystemMemory
245				only). IO ports and memory declared in ACPI might be
246				used by the ACPI subsystem in arbitrary AML code and
247				can interfere with legacy drivers.
248				strict (default): access to resources claimed by ACPI
249				is denied; legacy drivers trying to access reserved
250				resources will fail to bind to device using them.
251				lax: access to resources claimed by ACPI is allowed;
252				legacy drivers trying to access reserved resources
253				will bind successfully but a warning message is logged.
254				no: ACPI OperationRegions are not marked as reserved,
255				no further checks are performed.
257		acpi_force_table_verification	[HW,ACPI]
258				Enable table checksum verification during early stage.
259				By default, this is disabled due to x86 early mapping
260				size limitation.
262		acpi_irq_balance [HW,ACPI]
263				ACPI will balance active IRQs
264				default in APIC mode
266		acpi_irq_nobalance [HW,ACPI]
267				ACPI will not move active IRQs (default)
268				default in PIC mode
270		acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
271				Format: <irq>,<irq>...
273		acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
274				use by PCI
275				Format: <irq>,<irq>...
277		acpi_no_auto_serialize	[HW,ACPI]
278				Disable auto-serialization of AML methods
279				AML control methods that contain the opcodes to create
280				named objects will be marked as "Serialized" by the
281				auto-serialization feature.
282				This feature is enabled by default.
283				This option allows to turn off the feature.
285		acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
286				   kernels.
288		acpi_no_static_ssdt	[HW,ACPI]
289				Disable installation of static SSDTs at early boot time
290				By default, SSDTs contained in the RSDT/XSDT will be
291				installed automatically and they will appear under
292				/sys/firmware/acpi/tables.
293				This option turns off this feature.
294				Note that specifying this option does not affect
295				dynamic table installation which will install SSDT
296				tables to /sys/firmware/acpi/tables/dynamic.
298		acpi_rsdp=	[ACPI,EFI,KEXEC]
299				Pass the RSDP address to the kernel, mostly used
300				on machines running EFI runtime service to boot the
301				second kernel for kdump.
303		acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
304				Format: To spoof as Windows 98: ="Microsoft Windows"
306		acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
307				of 2 which is mandated by ACPI 6) as the supported ACPI
308				specification revision (when using this switch, it may
309				be necessary to carry out a cold reboot _twice_ in a
310				row to make it take effect on the platform firmware).
312		acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
313				acpi_osi="string1"	# add string1
314				acpi_osi="!string2"	# remove string2
315				acpi_osi=!*		# remove all strings
316				acpi_osi=!		# disable all built-in OS vendor
317							  strings
318				acpi_osi=!!		# enable all built-in OS vendor
319							  strings
320				acpi_osi=		# disable all strings
322				'acpi_osi=!' can be used in combination with single or
323				multiple 'acpi_osi="string1"' to support specific OS
324				vendor string(s).  Note that such command can only
325				affect the default state of the OS vendor strings, thus
326				it cannot affect the default state of the feature group
327				strings and the current state of the OS vendor strings,
328				specifying it multiple times through kernel command line
329				is meaningless.  This command is useful when one do not
330				care about the state of the feature group strings which
331				should be controlled by the OSPM.
332				Examples:
333				  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
334				     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
335				     can make '_OSI("Windows 2000")' TRUE.
337				'acpi_osi=' cannot be used in combination with other
338				'acpi_osi=' command lines, the _OSI method will not
339				exist in the ACPI namespace.  NOTE that such command can
340				only affect the _OSI support state, thus specifying it
341				multiple times through kernel command line is also
342				meaningless.
343				Examples:
344				  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
345				     FALSE.
347				'acpi_osi=!*' can be used in combination with single or
348				multiple 'acpi_osi="string1"' to support specific
349				string(s).  Note that such command can affect the
350				current state of both the OS vendor strings and the
351				feature group strings, thus specifying it multiple times
352				through kernel command line is meaningful.  But it may
353				still not able to affect the final state of a string if
354				there are quirks related to this string.  This command
355				is useful when one want to control the state of the
356				feature group strings to debug BIOS issues related to
357				the OSPM features.
358				Examples:
359				  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
360				     '_OSI("Module Device")' FALSE.
361				  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
362				     '_OSI("Module Device")' TRUE.
363				  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
364				     equivalent to
365				     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
366				     and
367				     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
368				     they all will make '_OSI("Windows 2000")' TRUE.
370		acpi_pm_good	[X86]
371				Override the pmtimer bug detection: force the kernel
372				to assume that this machine's pmtimer latches its value
373				and always returns good values.
375		acpi_sci=	[HW,ACPI] ACPI System Control Interrupt trigger mode
376				Format: { level | edge | high | low }
378		acpi_skip_timer_override [HW,ACPI]
379				Recognize and ignore IRQ0/pin2 Interrupt Override.
380				For broken nForce2 BIOS resulting in XT-PIC timer.
382		acpi_sleep=	[HW,ACPI] Sleep options
383				Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
384					  old_ordering, nonvs, sci_force_enable }
385				See Documentation/power/video.txt for information on
386				s3_bios and s3_mode.
387				s3_beep is for debugging; it makes the PC's speaker beep
388				as soon as the kernel's real-mode entry point is called.
389				s4_nohwsig prevents ACPI hardware signature from being
390				used during resume from hibernation.
391				old_ordering causes the ACPI 1.0 ordering of the _PTS
392				control method, with respect to putting devices into
393				low power states, to be enforced (the ACPI 2.0 ordering
394				of _PTS is used by default).
395				nonvs prevents the kernel from saving/restoring the
396				ACPI NVS memory during suspend/hibernation and resume.
397				sci_force_enable causes the kernel to set SCI_EN directly
398				on resume from S1/S3 (which is against the ACPI spec,
399				but some broken systems don't work without it).
401		acpi_use_timer_override [HW,ACPI]
402				Use timer override. For some broken Nvidia NF5 boards
403				that require a timer override, but don't have HPET
405		add_efi_memmap	[EFI; X86] Include EFI memory map in
406				kernel's map of available physical RAM.
408		agp=		[AGP]
409				{ off | try_unsupported }
410				off: disable AGP support
411				try_unsupported: try to drive unsupported chipsets
412					(may crash computer or cause data corruption)
414		ALSA		[HW,ALSA]
415				See Documentation/sound/alsa/alsa-parameters.txt
417		alignment=	[KNL,ARM]
418				Allow the default userspace alignment fault handler
419				behaviour to be specified.  Bit 0 enables warnings,
420				bit 1 enables fixups, and bit 2 sends a segfault.
422		align_va_addr=	[X86-64]
423				Align virtual addresses by clearing slice [14:12] when
424				allocating a VMA at process creation time. This option
425				gives you up to 3% performance improvement on AMD F15h
426				machines (where it is enabled by default) for a
427				CPU-intensive style benchmark, and it can vary highly in
428				a microbenchmark depending on workload and compiler.
430				32: only for 32-bit processes
431				64: only for 64-bit processes
432				on: enable for both 32- and 64-bit processes
433				off: disable for both 32- and 64-bit processes
435		alloc_snapshot	[FTRACE]
436				Allocate the ftrace snapshot buffer on boot up when the
437				main buffer is allocated. This is handy if debugging
438				and you need to use tracing_snapshot() on boot up, and
439				do not want to use tracing_snapshot_alloc() as it needs
440				to be done where GFP_KERNEL allocations are allowed.
442		amd_iommu=	[HW,X86-64]
443				Pass parameters to the AMD IOMMU driver in the system.
444				Possible values are:
445				fullflush - enable flushing of IO/TLB entries when
446					    they are unmapped. Otherwise they are
447					    flushed before they will be reused, which
448					    is a lot of faster
449				off	  - do not initialize any AMD IOMMU found in
450					    the system
451				force_isolation - Force device isolation for all
452						  devices. The IOMMU driver is not
453						  allowed anymore to lift isolation
454						  requirements as needed. This option
455						  does not override iommu=pt
457		amd_iommu_dump=	[HW,X86-64]
458				Enable AMD IOMMU driver option to dump the ACPI table
459				for AMD IOMMU. With this option enabled, AMD IOMMU
460				driver will print ACPI tables for AMD IOMMU during
461				IOMMU initialization.
463		amijoy.map=	[HW,JOY] Amiga joystick support
464				Map of devices attached to JOY0DAT and JOY1DAT
465				Format: <a>,<b>
466				See also Documentation/input/joystick.txt
468		analog.map=	[HW,JOY] Analog joystick and gamepad support
469				Specifies type or capabilities of an analog joystick
470				connected to one of 16 gameports
471				Format: <type1>,<type2>,..<type16>
473		apc=		[HW,SPARC]
474				Power management functions (SPARCstation-4/5 + deriv.)
475				Format: noidle
476				Disable APC CPU standby support. SPARCstation-Fox does
477				not play well with APC CPU idle - disable it if you have
478				APC and your system crashes randomly.
480		apic=		[APIC,X86-32] Advanced Programmable Interrupt Controller
481				Change the output verbosity whilst booting
482				Format: { quiet (default) | verbose | debug }
483				Change the amount of debugging information output
484				when initialising the APIC and IO-APIC components.
486		apic_extnmi=	[APIC,X86] External NMI delivery setting
487				Format: { bsp (default) | all | none }
488				bsp:  External NMI is delivered only to CPU 0
489				all:  External NMIs are broadcast to all CPUs as a
490				      backup of CPU 0
491				none: External NMI is masked for all CPUs. This is
492				      useful so that a dump capture kernel won't be
493				      shot down by NMI
495		autoconf=	[IPV6]
496				See Documentation/networking/ipv6.txt.
498		show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
499				Limit apic dumping. The parameter defines the maximal
500				number of local apics being dumped. Also it is possible
501				to set it to "all" by meaning -- no limit here.
502				Format: { 1 (default) | 2 | ... | all }.
503				The parameter valid if only apic=debug or
504				apic=verbose is specified.
505				Example: apic=debug show_lapic=all
507		apm=		[APM] Advanced Power Management
508				See header of arch/x86/kernel/apm_32.c.
510		arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
511				Format: <io>,<irq>,<nodeID>
513		ataflop=	[HW,M68k]
515		atarimouse=	[HW,MOUSE] Atari Mouse
517		atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
518				EzKey and similar keyboards
520		atkbd.reset=	[HW] Reset keyboard during initialization
522		atkbd.set=	[HW] Select keyboard code set
523				Format: <int> (2 = AT (default), 3 = PS/2)
525		atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
526				keyboards
528		atkbd.softraw=	[HW] Choose between synthetic and real raw mode
529				Format: <bool> (0 = real, 1 = synthetic (default))
531		atkbd.softrepeat= [HW]
532				Use software keyboard repeat
534		audit=		[KNL] Enable the audit sub-system
535				Format: { "0" | "1" } (0 = disabled, 1 = enabled)
536				0 - kernel audit is disabled and can not be enabled
537				    until the next reboot
538				unset - kernel audit is initialized but disabled and
539				    will be fully enabled by the userspace auditd.
540				1 - kernel audit is initialized and partially enabled,
541				    storing at most audit_backlog_limit messages in
542				    RAM until it is fully enabled by the userspace
543				    auditd.
544				Default: unset
546		audit_backlog_limit= [KNL] Set the audit queue size limit.
547				Format: <int> (must be >=0)
548				Default: 64
550		bau=		[X86_UV] Enable the BAU on SGI UV.  The default
551				behavior is to disable the BAU (i.e. bau=0).
552				Format: { "0" | "1" }
553				0 - Disable the BAU.
554				1 - Enable the BAU.
555				unset - Disable the BAU.
557		baycom_epp=	[HW,AX25]
558				Format: <io>,<mode>
560		baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
561				Format: <io>,<mode>
562				See header of drivers/net/hamradio/baycom_par.c.
564		baycom_ser_fdx=	[HW,AX25]
565				BayCom Serial Port AX.25 Modem (Full Duplex Mode)
566				Format: <io>,<irq>,<mode>[,<baud>]
567				See header of drivers/net/hamradio/baycom_ser_fdx.c.
569		baycom_ser_hdx=	[HW,AX25]
570				BayCom Serial Port AX.25 Modem (Half Duplex Mode)
571				Format: <io>,<irq>,<mode>
572				See header of drivers/net/hamradio/baycom_ser_hdx.c.
574		blkdevparts=	Manual partition parsing of block device(s) for
575				embedded devices based on command line input.
576				See Documentation/block/cmdline-partition.txt
578		boot_delay=	Milliseconds to delay each printk during boot.
579				Values larger than 10 seconds (10000) are changed to
580				no delay (0).
581				Format: integer
583		bootmem_debug	[KNL] Enable bootmem allocator debug messages.
585		bert_disable	[ACPI]
586				Disable BERT OS support on buggy BIOSes.
588		bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
589		bttv.radio=	Most important insmod options are available as
590				kernel args too.
591		bttv.pll=	See Documentation/video4linux/bttv/Insmod-options
592		bttv.tuner=
594		bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
595				firmware feature for flushing multiple hpte entries
596				at a time.
598		c101=		[NET] Moxa C101 synchronous serial card
600		cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
601				Sometimes CPU hardware bugs make them report the cache
602				size incorrectly. The kernel will attempt work arounds
603				to fix known problems, but for some CPUs it is not
604				possible to determine what the correct size should be.
605				This option provides an override for these situations.
607		ca_keys=	[KEYS] This parameter identifies a specific key(s) on
608				the system trusted keyring to be used for certificate
609				trust validation.
610				format: { id:<keyid> | builtin }
612		cca=		[MIPS] Override the kernel pages' cache coherency
613				algorithm.  Accepted values range from 0 to 7
614				inclusive. See arch/mips/include/asm/pgtable-bits.h
615				for platform specific values (SB1, Loongson3 and
616				others).
618		ccw_timeout_log [S390]
619				See Documentation/s390/CommonIO for details.
621		cgroup_disable= [KNL] Disable a particular controller
622				Format: {name of the controller(s) to disable}
623				The effects of cgroup_disable=foo are:
624				- foo isn't auto-mounted if you mount all cgroups in
625				  a single hierarchy
626				- foo isn't visible as an individually mountable
627				  subsystem
628				{Currently only "memory" controller deal with this and
629				cut the overhead, others just disable the usage. So
630				only cgroup_disable=memory is actually worthy}
632		cgroup_no_v1=	[KNL] Disable one, multiple, all cgroup controllers in v1
633				Format: { controller[,controller...] | "all" }
634				Like cgroup_disable, but only applies to cgroup v1;
635				the blacklisted controllers remain available in cgroup2.
637		cgroup.memory=	[KNL] Pass options to the cgroup memory controller.
638				Format: <string>
639				nosocket -- Disable socket memory accounting.
640				nokmem -- Disable kernel memory accounting.
642		checkreqprot	[SELINUX] Set initial checkreqprot flag value.
643				Format: { "0" | "1" }
644				See security/selinux/Kconfig help text.
645				0 -- check protection applied by kernel (includes
646					any implied execute protection).
647				1 -- check protection requested by application.
648				Default value is set via a kernel config option.
649				Value can be changed at runtime via
650					/selinux/checkreqprot.
652		cio_ignore=	[S390]
653				See Documentation/s390/CommonIO for details.
654		clk_ignore_unused
655				[CLK]
656				Prevents the clock framework from automatically gating
657				clocks that have not been explicitly enabled by a Linux
658				device driver but are enabled in hardware at reset or
659				by the bootloader/firmware. Note that this does not
660				force such clocks to be always-on nor does it reserve
661				those clocks in any way. This parameter is useful for
662				debug and development, but should not be needed on a
663				platform with proper driver support.  For more
664				information, see Documentation/clk.txt.
666		clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
667				[Deprecated]
668				Forces specified clocksource (if available) to be used
669				when calculating gettimeofday(). If specified
670				clocksource is not available, it defaults to PIT.
671				Format: { pit | tsc | cyclone | pmtmr }
673		clocksource=	Override the default clocksource
674				Format: <string>
675				Override the default clocksource and use the clocksource
676				with the name specified.
677				Some clocksource names to choose from, depending on
678				the platform:
679				[all] jiffies (this is the base, fallback clocksource)
680				[ACPI] acpi_pm
681				[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
682					pxa_timer,timer3,32k_counter,timer0_1
683				[AVR32] avr32
684				[X86-32] pit,hpet,tsc;
685					scx200_hrt on Geode; cyclone on IBM x440
686				[MIPS] MIPS
687				[PARISC] cr16
688				[S390] tod
689				[SH] SuperH
690				[SPARC64] tick
691				[X86-64] hpet,tsc
693		clocksource.arm_arch_timer.evtstrm=
694				[ARM,ARM64]
695				Format: <bool>
696				Enable/disable the eventstream feature of the ARM
697				architected timer so that code using WFE-based polling
698				loops can be debugged more effectively on production
699				systems.
701		clearcpuid=BITNUM [X86]
702				Disable CPUID feature X for the kernel. See
703				arch/x86/include/asm/cpufeatures.h for the valid bit
704				numbers. Note the Linux specific bits are not necessarily
705				stable over kernel options, but the vendor specific
706				ones should be.
707				Also note that user programs calling CPUID directly
708				or using the feature without checking anything
709				will still see it. This just prevents it from
710				being used by the kernel or shown in /proc/cpuinfo.
711				Also note the kernel might malfunction if you disable
712				some critical bits.
714		cma=nn[MG]@[start[MG][-end[MG]]]
715				[ARM,X86,KNL]
716				Sets the size of kernel global memory area for
717				contiguous memory allocations and optionally the
718				placement constraint by the physical address range of
719				memory allocations. A value of 0 disables CMA
720				altogether. For more information, see
721				include/linux/dma-contiguous.h
723		cmo_free_hint=	[PPC] Format: { yes | no }
724				Specify whether pages are marked as being inactive
725				when they are freed.  This is used in CMO environments
726				to determine OS memory pressure for page stealing by
727				a hypervisor.
728				Default: yes
730		coherent_pool=nn[KMG]	[ARM,KNL]
731				Sets the size of memory pool for coherent, atomic dma
732				allocations, by default set to 256K.
734		code_bytes	[X86] How many bytes of object code to print
735				in an oops report.
736				Range: 0 - 8192
737				Default: 64
739		com20020=	[HW,NET] ARCnet - COM20020 chipset
740				Format:
741				<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
743		com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
744				Format: <io>[,<irq>]
746		com90xx=	[HW,NET]
747				ARCnet - COM90xx chipset (memory-mapped buffers)
748				Format: <io>[,<irq>[,<memstart>]]
750		condev=		[HW,S390] console device
751		conmode=
753		console=	[KNL] Output console device and options.
755			tty<n>	Use the virtual console device <n>.
757			ttyS<n>[,options]
758			ttyUSB0[,options]
759				Use the specified serial port.  The options are of
760				the form "bbbbpnf", where "bbbb" is the baud rate,
761				"p" is parity ("n", "o", or "e"), "n" is number of
762				bits, and "f" is flow control ("r" for RTS or
763				omit it).  Default is "9600n8".
765				See Documentation/serial-console.txt for more
766				information.  See
767				Documentation/networking/netconsole.txt for an
768				alternative.
770			uart[8250],io,<addr>[,options]
771			uart[8250],mmio,<addr>[,options]
772			uart[8250],mmio16,<addr>[,options]
773			uart[8250],mmio32,<addr>[,options]
774			uart[8250],0x<addr>[,options]
775				Start an early, polled-mode console on the 8250/16550
776				UART at the specified I/O port or MMIO address,
777				switching to the matching ttyS device later.
778				MMIO inter-register address stride is either 8-bit
779				(mmio), 16-bit (mmio16), or 32-bit (mmio32).
780				If none of [io|mmio|mmio16|mmio32], <addr> is assumed
781				to be equivalent to 'mmio'. 'options' are specified in
782				the same format described for ttyS above; if unspecified,
783				the h/w is not re-initialized.
785			hvc<n>	Use the hypervisor console device <n>. This is for
786				both Xen and PowerPC hypervisors.
788	                If the device connected to the port is not a TTY but a braille
789	                device, prepend "brl," before the device type, for instance
790				console=brl,ttyS0
791			For now, only VisioBraille is supported.
793		consoleblank=	[KNL] The console blank (screen saver) timeout in
794				seconds. Defaults to 10*60 = 10mins. A value of 0
795				disables the blank timer.
797		coredump_filter=
798				[KNL] Change the default value for
799				/proc/<pid>/coredump_filter.
800				See also Documentation/filesystems/proc.txt.
802		cpuidle.off=1	[CPU_IDLE]
803				disable the cpuidle sub-system
805		cpu_init_udelay=N
806				[X86] Delay for N microsec between assert and de-assert
807				of APIC INIT to start processors.  This delay occurs
808				on every CPU online, such as boot, and resume from suspend.
809				Default: 10000
811		cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
812				Format:
813				<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
815		crashkernel=size[KMG][@offset[KMG]]
816				[KNL] Using kexec, Linux can switch to a 'crash kernel'
817				upon panic. This parameter reserves the physical
818				memory region [offset, offset + size] for that kernel
819				image. If '@offset' is omitted, then a suitable offset
820				is selected automatically. Check
821				Documentation/kdump/kdump.txt for further details.
823		crashkernel=range1:size1[,range2:size2,...][@offset]
824				[KNL] Same as above, but depends on the memory
825				in the running system. The syntax of range is
826				start-[end] where start and end are both
827				a memory unit (amount[KMG]). See also
828				Documentation/kdump/kdump.txt for an example.
830		crashkernel=size[KMG],high
831				[KNL, x86_64] range could be above 4G. Allow kernel
832				to allocate physical memory region from top, so could
833				be above 4G if system have more than 4G ram installed.
834				Otherwise memory region will be allocated below 4G, if
835				available.
836				It will be ignored if crashkernel=X is specified.
837		crashkernel=size[KMG],low
838				[KNL, x86_64] range under 4G. When crashkernel=X,high
839				is passed, kernel could allocate physical memory region
840				above 4G, that cause second kernel crash on system
841				that require some amount of low memory, e.g. swiotlb
842				requires at least 64M+32K low memory, also enough extra
843				low memory is needed to make sure DMA buffers for 32-bit
844				devices won't run out. Kernel would try to allocate at
845				at least 256M below 4G automatically.
846				This one let user to specify own low range under 4G
847				for second kernel instead.
848				0: to disable low allocation.
849				It will be ignored when crashkernel=X,high is not used
850				or memory reserved is below 4G.
852		cryptomgr.notests
853	                        [KNL] Disable crypto self-tests
855		cs89x0_dma=	[HW,NET]
856				Format: <dma>
858		cs89x0_media=	[HW,NET]
859				Format: { rj45 | aui | bnc }
861		dasd=		[HW,NET]
862				See header of drivers/s390/block/dasd_devmap.c.
864		db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
865				(one device per port)
866				Format: <port#>,<type>
867				See also Documentation/input/joystick-parport.txt
869		ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
870				time. See Documentation/dynamic-debug-howto.txt for
871				details.  Deprecated, see dyndbg.
873		debug		[KNL] Enable kernel debugging (events log level).
875		debug_locks_verbose=
876				[KNL] verbose self-tests
877				Format=<0|1>
878				Print debugging info while doing the locking API
879				self-tests.
880				We default to 0 (no extra messages), setting it to
881				1 will print _a lot_ more information - normally
882				only useful to kernel developers.
884		debug_objects	[KNL] Enable object debugging
886		no_debug_objects
887				[KNL] Disable object debugging
889		debug_guardpage_minorder=
890				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
891				parameter allows control of the order of pages that will
892				be intentionally kept free (and hence protected) by the
893				buddy allocator. Bigger value increase the probability
894				of catching random memory corruption, but reduce the
895				amount of memory for normal system use. The maximum
896				possible value is MAX_ORDER/2.  Setting this parameter
897				to 1 or 2 should be enough to identify most random
898				memory corruption problems caused by bugs in kernel or
899				driver code when a CPU writes to (or reads from) a
900				random memory location. Note that there exists a class
901				of memory corruptions problems caused by buggy H/W or
902				F/W or by drivers badly programing DMA (basically when
903				memory is written at bus level and the CPU MMU is
904				bypassed) which are not detectable by
905				CONFIG_DEBUG_PAGEALLOC, hence this option will not help
906				tracking down these problems.
908		debug_pagealloc=
909				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
910				parameter enables the feature at boot time. In
911				default, it is disabled. We can avoid allocating huge
912				chunk of memory for debug pagealloc if we don't enable
913				it at boot time and the system will work mostly same
914				with the kernel built without CONFIG_DEBUG_PAGEALLOC.
915				on: enable the feature
917		debugpat	[X86] Enable PAT debugging
919		decnet.addr=	[HW,NET]
920				Format: <area>[,<node>]
921				See also Documentation/networking/decnet.txt.
923		default_hugepagesz=
924				[same as hugepagesz=] The size of the default
925				HugeTLB page size. This is the size represented by
926				the legacy /proc/ hugepages APIs, used for SHM, and
927				default size when mounting hugetlbfs filesystems.
928				Defaults to the default architecture's huge page size
929				if not specified.
931		dhash_entries=	[KNL]
932				Set number of hash buckets for dentry cache.
934		disable_1tb_segments [PPC]
935				Disables the use of 1TB hash page table segments. This
936				causes the kernel to fall back to 256MB segments which
937				can be useful when debugging issues that require an SLB
938				miss to occur.
940		disable=	[IPV6]
941				See Documentation/networking/ipv6.txt.
943		disable_radix	[PPC]
944				Disable RADIX MMU mode on POWER9
946		disable_cpu_apicid= [X86,APIC,SMP]
947				Format: <int>
948				The number of initial APIC ID for the
949				corresponding CPU to be disabled at boot,
950				mostly used for the kdump 2nd kernel to
951				disable BSP to wake up multiple CPUs without
952				causing system reset or hang due to sending
953				INIT from AP to BSP.
955		disable_ddw     [PPC/PSERIES]
956				Disable Dynamic DMA Window support. Use this if
957				to workaround buggy firmware.
959		disable_ipv6=	[IPV6]
960				See Documentation/networking/ipv6.txt.
962		disable_mtrr_cleanup [X86]
963				The kernel tries to adjust MTRR layout from continuous
964				to discrete, to make X server driver able to add WB
965				entry later. This parameter disables that.
967		disable_mtrr_trim [X86, Intel and AMD only]
968				By default the kernel will trim any uncacheable
969				memory out of your available memory pool based on
970				MTRR settings.  This parameter disables that behavior,
971				possibly causing your machine to run very slowly.
973		disable_timer_pin_1 [X86]
974				Disable PIN 1 of APIC timer
975				Can be useful to work around chipset bugs.
977		dis_ucode_ldr	[X86] Disable the microcode loader.
979		dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
980				this option disables the debugging code at boot.
982		dma_debug_entries=<number>
983				This option allows to tune the number of preallocated
984				entries for DMA-API debugging code. One entry is
985				required per DMA-API allocation. Use this if the
986				DMA-API debugging code disables itself because the
987				architectural default is too low.
989		dma_debug_driver=<driver_name>
990				With this option the DMA-API debugging driver
991				filter feature can be enabled at boot time. Just
992				pass the driver to filter for as the parameter.
993				The filter can be disabled or changed to another
994				driver later using sysfs.
996		drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
997				Broken monitors, graphic adapters, KVMs and EDIDless
998				panels may send no or incorrect EDID data sets.
999				This parameter allows to specify an EDID data sets
1000				in the /lib/firmware directory that are used instead.
1001				Generic built-in EDID data sets are used, if one of
1002				edid/1024x768.bin, edid/1280x1024.bin,
1003				edid/1680x1050.bin, or edid/1920x1080.bin is given
1004				and no file with the same name exists. Details and
1005				instructions how to build your own EDID data are
1006				available in Documentation/EDID/HOWTO.txt. An EDID
1007				data set will only be used for a particular connector,
1008				if its name and a colon are prepended to the EDID
1009				name. Each connector may use a unique EDID data
1010				set by separating the files with a comma.  An EDID
1011				data set with no connector name will be used for
1012				any connectors not explicitly specified.
1014		dscc4.setup=	[NET]
1016		dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
1017		module.dyndbg[="val"]
1018				Enable debug messages at boot time.  See
1019				Documentation/dynamic-debug-howto.txt for details.
1021		nompx		[X86] Disables Intel Memory Protection Extensions.
1022				See Documentation/x86/intel_mpx.txt for more
1023				information about the feature.
1025		nopku		[X86] Disable Memory Protection Keys CPU feature found
1026				in some Intel CPUs.
1028		eagerfpu=	[X86]
1029				on	enable eager fpu restore
1030				off	disable eager fpu restore
1031				auto	selects the default scheme, which automatically
1032					enables eagerfpu restore for xsaveopt.
1034		module.async_probe [KNL]
1035				Enable asynchronous probe on this module.
1037		early_ioremap_debug [KNL]
1038				Enable debug messages in early_ioremap support. This
1039				is useful for tracking down temporary early mappings
1040				which are not unmapped.
1042		earlycon=	[KNL] Output early console device and options.
1044				When used with no options, the early console is
1045				determined by the stdout-path property in device
1046				tree's chosen node.
1048			cdns,<addr>
1049				Start an early, polled-mode console on a cadence serial
1050				port at the specified address. The cadence serial port
1051				must already be setup and configured. Options are not
1052				yet supported.
1054			uart[8250],io,<addr>[,options]
1055			uart[8250],mmio,<addr>[,options]
1056			uart[8250],mmio32,<addr>[,options]
1057			uart[8250],mmio32be,<addr>[,options]
1058			uart[8250],0x<addr>[,options]
1059				Start an early, polled-mode console on the 8250/16550
1060				UART at the specified I/O port or MMIO address.
1061				MMIO inter-register address stride is either 8-bit
1062				(mmio) or 32-bit (mmio32 or mmio32be).
1063				If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1064				to be equivalent to 'mmio'. 'options' are specified
1065				in the same format described for "console=ttyS<n>"; if
1066				unspecified, the h/w is not initialized.
1068			pl011,<addr>
1069			pl011,mmio32,<addr>
1070				Start an early, polled-mode console on a pl011 serial
1071				port at the specified address. The pl011 serial port
1072				must already be setup and configured. Options are not
1073				yet supported.  If 'mmio32' is specified, then only
1074				the driver will use only 32-bit accessors to read/write
1075				the device registers.
1077			meson,<addr>
1078				Start an early, polled-mode console on a meson serial
1079				port at the specified address. The serial port must
1080				already be setup and configured. Options are not yet
1081				supported.
1083			msm_serial,<addr>
1084				Start an early, polled-mode console on an msm serial
1085				port at the specified address. The serial port
1086				must already be setup and configured. Options are not
1087				yet supported.
1089			msm_serial_dm,<addr>
1090				Start an early, polled-mode console on an msm serial
1091				dm port at the specified address. The serial port
1092				must already be setup and configured. Options are not
1093				yet supported.
1095			smh	Use ARM semihosting calls for early console.
1097			s3c2410,<addr>
1098			s3c2412,<addr>
1099			s3c2440,<addr>
1100			s3c6400,<addr>
1101			s5pv210,<addr>
1102			exynos4210,<addr>
1103				Use early console provided by serial driver available
1104				on Samsung SoCs, requires selecting proper type and
1105				a correct base address of the selected UART port. The
1106				serial port must already be setup and configured.
1107				Options are not yet supported.
1109			lpuart,<addr>
1110			lpuart32,<addr>
1111				Use early console provided by Freescale LP UART driver
1112				found on Freescale Vybrid and QorIQ LS1021A processors.
1113				A valid base address must be provided, and the serial
1114				port must already be setup and configured.
1116			armada3700_uart,<addr>
1117				Start an early, polled-mode console on the
1118				Armada 3700 serial port at the specified
1119				address. The serial port must already be setup
1120				and configured. Options are not yet supported.
1122		earlyprintk=	[X86,SH,BLACKFIN,ARM,M68k]
1123				earlyprintk=vga
1124				earlyprintk=efi
1125				earlyprintk=xen
1126				earlyprintk=serial[,ttySn[,baudrate]]
1127				earlyprintk=serial[,0x...[,baudrate]]
1128				earlyprintk=ttySn[,baudrate]
1129				earlyprintk=dbgp[debugController#]
1130				earlyprintk=pciserial,bus:device.function[,baudrate]
1132				earlyprintk is useful when the kernel crashes before
1133				the normal console is initialized. It is not enabled by
1134				default because it has some cosmetic problems.
1136				Append ",keep" to not disable it when the real console
1137				takes over.
1139				Only one of vga, efi, serial, or usb debug port can
1140				be used at a time.
1142				Currently only ttyS0 and ttyS1 may be specified by
1143				name.  Other I/O ports may be explicitly specified
1144				on some architectures (x86 and arm at least) by
1145				replacing ttySn with an I/O port address, like this:
1146					earlyprintk=serial,0x1008,115200
1147				You can find the port for a given device in
1148				/proc/tty/driver/serial:
1149					2: uart:ST16650V2 port:00001008 irq:18 ...
1151				Interaction with the standard serial driver is not
1152				very good.
1154				The VGA and EFI output is eventually overwritten by
1155				the real console.
1157				The xen output can only be used by Xen PV guests.
1159		edac_report=	[HW,EDAC] Control how to report EDAC event
1160				Format: {"on" | "off" | "force"}
1161				on: enable EDAC to report H/W event. May be overridden
1162				by other higher priority error reporting module.
1163				off: disable H/W event reporting through EDAC.
1164				force: enforce the use of EDAC to report H/W event.
1165				default: on.
1167		ekgdboc=	[X86,KGDB] Allow early kernel console debugging
1168				ekgdboc=kbd
1170				This is designed to be used in conjunction with
1171				the boot argument: earlyprintk=vga
1173		edd=		[EDD]
1174				Format: {"off" | "on" | "skip[mbr]"}
1176		efi=		[EFI]
1177				Format: { "old_map", "nochunk", "noruntime", "debug" }
1178				old_map [X86-64]: switch to the old ioremap-based EFI
1179				runtime services mapping. 32-bit still uses this one by
1180				default.
1181				nochunk: disable reading files in "chunks" in the EFI
1182				boot stub, as chunking can cause problems with some
1183				firmware implementations.
1184				noruntime : disable EFI runtime services support
1185				debug: enable misc debug output
1187		efi_no_storage_paranoia [EFI; X86]
1188				Using this parameter you can use more than 50% of
1189				your efi variable storage. Use this parameter only if
1190				you are really sure that your UEFI does sane gc and
1191				fulfills the spec otherwise your board may brick.
1193		efi_fake_mem=	nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1194				Add arbitrary attribute to specific memory range by
1195				updating original EFI memory map.
1196				Region of memory which aa attribute is added to is
1197				from ss to ss+nn.
1198				If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1199				is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1200				attribute is added to range 0x100000000-0x180000000 and
1201				0x10a0000000-0x1120000000.
1203				Using this parameter you can do debugging of EFI memmap
1204				related feature. For example, you can do debugging of
1205				Address Range Mirroring feature even if your box
1206				doesn't support it.
1208		efivar_ssdt=	[EFI; X86] Name of an EFI variable that contains an SSDT
1209				that is to be dynamically loaded by Linux. If there are
1210				multiple variables with the same name but with different
1211				vendor GUIDs, all of them will be loaded. See
1212				Documentation/acpi/ssdt-overlays.txt for details.
1215		eisa_irq_edge=	[PARISC,HW]
1216				See header of drivers/parisc/eisa.c.
1218		elanfreq=	[X86-32]
1219				See comment before function elanfreq_setup() in
1220				arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1222		elevator=	[IOSCHED]
1223				Format: {"cfq" | "deadline" | "noop"}
1224				See Documentation/block/cfq-iosched.txt and
1225				Documentation/block/deadline-iosched.txt for details.
1227		elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1228				Specifies physical address of start of kernel core
1229				image elf header and optionally the size. Generally
1230				kexec loader will pass this option to capture kernel.
1231				See Documentation/kdump/kdump.txt for details.
1233		enable_mtrr_cleanup [X86]
1234				The kernel tries to adjust MTRR layout from continuous
1235				to discrete, to make X server driver able to add WB
1236				entry later. This parameter enables that.
1238		enable_timer_pin_1 [X86]
1239				Enable PIN 1 of APIC timer
1240				Can be useful to work around chipset bugs
1241				(in particular on some ATI chipsets).
1242				The kernel tries to set a reasonable default.
1244		enforcing	[SELINUX] Set initial enforcing status.
1245				Format: {"0" | "1"}
1246				See security/selinux/Kconfig help text.
1247				0 -- permissive (log only, no denials).
1248				1 -- enforcing (deny and log).
1249				Default value is 0.
1250				Value can be changed at runtime via /selinux/enforce.
1252		erst_disable	[ACPI]
1253				Disable Error Record Serialization Table (ERST)
1254				support.
1256		ether=		[HW,NET] Ethernet cards parameters
1257				This option is obsoleted by the "netdev=" option, which
1258				has equivalent usage. See its documentation for details.
1260		evm=		[EVM]
1261				Format: { "fix" }
1262				Permit 'security.evm' to be updated regardless of
1263				current integrity status.
1265		failslab=
1266		fail_page_alloc=
1267		fail_make_request=[KNL]
1268				General fault injection mechanism.
1269				Format: <interval>,<probability>,<space>,<times>
1270				See also Documentation/fault-injection/.
1272		floppy=		[HW]
1273				See Documentation/blockdev/floppy.txt.
1275		force_pal_cache_flush
1276				[IA-64] Avoid check_sal_cache_flush which may hang on
1277				buggy SAL_CACHE_FLUSH implementations. Using this
1278				parameter will force ia64_sal_cache_flush to call
1279				ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1281		forcepae [X86-32]
1282				Forcefully enable Physical Address Extension (PAE).
1283				Many Pentium M systems disable PAE but may have a
1284				functionally usable PAE implementation.
1285				Warning: use of this parameter will taint the kernel
1286				and may cause unknown problems.
1288		ftrace=[tracer]
1289				[FTRACE] will set and start the specified tracer
1290				as early as possible in order to facilitate early
1291				boot debugging.
1293		ftrace_dump_on_oops[=orig_cpu]
1294				[FTRACE] will dump the trace buffers on oops.
1295				If no parameter is passed, ftrace will dump
1296				buffers of all CPUs, but if you pass orig_cpu, it will
1297				dump only the buffer of the CPU that triggered the
1298				oops.
1300		ftrace_filter=[function-list]
1301				[FTRACE] Limit the functions traced by the function
1302				tracer at boot up. function-list is a comma separated
1303				list of functions. This list can be changed at run
1304				time by the set_ftrace_filter file in the debugfs
1305				tracing directory.
1307		ftrace_notrace=[function-list]
1308				[FTRACE] Do not trace the functions specified in
1309				function-list. This list can be changed at run time
1310				by the set_ftrace_notrace file in the debugfs
1311				tracing directory.
1313		ftrace_graph_filter=[function-list]
1314				[FTRACE] Limit the top level callers functions traced
1315				by the function graph tracer at boot up.
1316				function-list is a comma separated list of functions
1317				that can be changed at run time by the
1318				set_graph_function file in the debugfs tracing directory.
1320		ftrace_graph_notrace=[function-list]
1321				[FTRACE] Do not trace from the functions specified in
1322				function-list.  This list is a comma separated list of
1323				functions that can be changed at run time by the
1324				set_graph_notrace file in the debugfs tracing directory.
1326		gamecon.map[2|3]=
1327				[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1328				support via parallel port (up to 5 devices per port)
1329				Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1330				See also Documentation/input/joystick-parport.txt
1332		gamma=		[HW,DRM]
1334		gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
1335				Format: off | on
1336				default: on
1338		gcov_persist=	[GCOV] When non-zero (default), profiling data for
1339				kernel modules is saved and remains accessible via
1340				debugfs, even when the module is unloaded/reloaded.
1341				When zero, profiling data is discarded and associated
1342				debugfs files are removed at module unload time.
1344		gpt		[EFI] Forces disk with valid GPT signature but
1345				invalid Protective MBR to be treated as GPT. If the
1346				primary GPT is corrupted, it enables the backup/alternate
1347				GPT to be used instead.
1349		grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1350				the "Enable 0" bit of the configuration register.
1351				Format: 0 | 1
1352				Default: 0
1353		grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1354				the "Enable 0" bit of the configuration register.
1355				Format: 0 | 1
1356				Default: 0
1357		grcan.select=	[HW] Select which physical interface to use.
1358				Format: 0 | 1
1359				Default: 0
1360		grcan.txsize=	[HW] Sets the size of the tx buffer.
1361				Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1362				Default: 1024
1363		grcan.rxsize=	[HW] Sets the size of the rx buffer.
1364				Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1365				Default: 1024
1367		hardlockup_all_cpu_backtrace=
1368				[KNL] Should the hard-lockup detector generate
1369				backtraces on all cpus.
1370				Format: <integer>
1372		hashdist=	[KNL,NUMA] Large hashes allocated during boot
1373				are distributed across NUMA nodes.  Defaults on
1374				for 64-bit NUMA, off otherwise.
1375				Format: 0 | 1 (for off | on)
1377		hcl=		[IA-64] SGI's Hardware Graph compatibility layer
1379		hd=		[EIDE] (E)IDE hard drive subsystem geometry
1380				Format: <cyl>,<head>,<sect>
1382		hest_disable	[ACPI]
1383				Disable Hardware Error Source Table (HEST) support;
1384				corresponding firmware-first mode error processing
1385				logic will be disabled.
1387		highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
1388				size of <nn>. This works even on boxes that have no
1389				highmem otherwise. This also works to reduce highmem
1390				size on bigger boxes.
1392		highres=	[KNL] Enable/disable high resolution timer mode.
1393				Valid parameters: "on", "off"
1394				Default: "on"
1396		hisax=		[HW,ISDN]
1397				See Documentation/isdn/README.HiSax.
1399		hlt		[BUGS=ARM,SH]
1401		hpet=		[X86-32,HPET] option to control HPET usage
1402				Format: { enable (default) | disable | force |
1403					verbose }
1404				disable: disable HPET and use PIT instead
1405				force: allow force enabled of undocumented chips (ICH4,
1406					VIA, nVidia)
1407				verbose: show contents of HPET registers during setup
1409		hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1410				registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1412		hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1413		hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1414				On x86-64 and powerpc, this option can be specified
1415				multiple times interleaved with hugepages= to reserve
1416				huge pages of different sizes. Valid pages sizes on
1417				x86-64 are 2M (when the CPU supports "pse") and 1G
1418				(when the CPU supports the "pdpe1gb" cpuinfo flag).
1420		hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
1421				       terminal devices. Valid values: 0..8
1422		hvc_iucv_allow=	[S390] Comma-separated list of z/VM user IDs.
1423				       If specified, z/VM IUCV HVC accepts connections
1424				       from listed z/VM user IDs only.
1426		hwthread_map=	[METAG] Comma-separated list of Linux cpu id to
1427				        hardware thread id mappings.
1428					Format: <cpu>:<hwthread>
1430		keep_bootcon	[KNL]
1431				Do not unregister boot console at start. This is only
1432				useful for debugging when something happens in the window
1433				between unregistering the boot console and initializing
1434				the real console.
1436		i2c_bus=	[HW] Override the default board specific I2C bus speed
1437				     or register an additional I2C bus that is not
1438				     registered from board initialization code.
1439				     Format:
1440				     <bus_id>,<clkrate>
1442		i8042.debug	[HW] Toggle i8042 debug mode
1443		i8042.unmask_kbd_data
1444				[HW] Enable printing of interrupt data from the KBD port
1445				     (disabled by default, and as a pre-condition
1446				     requires that i8042.debug=1 be enabled)
1447		i8042.direct	[HW] Put keyboard port into non-translated mode
1448		i8042.dumbkbd	[HW] Pretend that controller can only read data from
1449				     keyboard and cannot control its state
1450				     (Don't attempt to blink the leds)
1451		i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1452		i8042.nokbd	[HW] Don't check/create keyboard port
1453		i8042.noloop	[HW] Disable the AUX Loopback command while probing
1454				     for the AUX port
1455		i8042.nomux	[HW] Don't check presence of an active multiplexing
1456				     controller
1457		i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1458				     controllers
1459		i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1460		i8042.reset	[HW] Reset the controller during init and cleanup
1461		i8042.unlock	[HW] Unlock (ignore) the keylock
1462		i8042.kbdreset  [HW] Reset device connected to KBD port
1464		i810=		[HW,DRM]
1466		i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
1467				indicates that the driver is running on unsupported
1468				hardware.
1469		i8k.force	[HW] Activate i8k driver even if SMM BIOS signature
1470				does not match list of supported models.
1471		i8k.power_status
1472				[HW] Report power status in /proc/i8k
1473				(disabled by default)
1474		i8k.restricted	[HW] Allow controlling fans only if SYS_ADMIN
1475				capability is set.
1477		i915.invert_brightness=
1478				[DRM] Invert the sense of the variable that is used to
1479				set the brightness of the panel backlight. Normally a
1480				brightness value of 0 indicates backlight switched off,
1481				and the maximum of the brightness value sets the backlight
1482				to maximum brightness. If this parameter is set to 0
1483				(default) and the machine requires it, or this parameter
1484				is set to 1, a brightness value of 0 sets the backlight
1485				to maximum brightness, and the maximum of the brightness
1486				value switches the backlight off.
1487				-1 -- never invert brightness
1488				 0 -- machine default
1489				 1 -- force brightness inversion
1491		icn=		[HW,ISDN]
1492				Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1494		ide-core.nodma=	[HW] (E)IDE subsystem
1495				Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1496				.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1497				.cdrom .chs .ignore_cable are additional options
1498				See Documentation/ide/ide.txt.
1500		ide-generic.probe-mask= [HW] (E)IDE subsystem
1501				Format: <int>
1502				Probe mask for legacy ISA IDE ports.  Depending on
1503				platform up to 6 ports are supported, enabled by
1504				setting corresponding bits in the mask to 1.  The
1505				default value is 0x0, which has a special meaning.
1506				On systems that have PCI, it triggers scanning the
1507				PCI bus for the first and the second port, which
1508				are then probed.  On systems without PCI the value
1509				of 0x0 enables probing the two first ports as if it
1510				was 0x3.
1512		ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1513				Claim all unknown PCI IDE storage controllers.
1515		idle=		[X86]
1516				Format: idle=poll, idle=halt, idle=nomwait
1517				Poll forces a polling idle loop that can slightly
1518				improve the performance of waking up a idle CPU, but
1519				will use a lot of power and make the system run hot.
1520				Not recommended.
1521				idle=halt: Halt is forced to be used for CPU idle.
1522				In such case C2/C3 won't be used again.
1523				idle=nomwait: Disable mwait for CPU C-states
1525		ieee754=	[MIPS] Select IEEE Std 754 conformance mode
1526				Format: { strict | legacy | 2008 | relaxed }
1527				Default: strict
1529				Choose which programs will be accepted for execution
1530				based on the IEEE 754 NaN encoding(s) supported by
1531				the FPU and the NaN encoding requested with the value
1532				of an ELF file header flag individually set by each
1533				binary.  Hardware implementations are permitted to
1534				support either or both of the legacy and the 2008 NaN
1535				encoding mode.
1537				Available settings are as follows:
1538				strict	accept binaries that request a NaN encoding
1539					supported by the FPU
1540				legacy	only accept legacy-NaN binaries, if supported
1541					by the FPU
1542				2008	only accept 2008-NaN binaries, if supported
1543					by the FPU
1544				relaxed	accept any binaries regardless of whether
1545					supported by the FPU
1547				The FPU emulator is always able to support both NaN
1548				encodings, so if no FPU hardware is present or it has
1549				been disabled with 'nofpu', then the settings of
1550				'legacy' and '2008' strap the emulator accordingly,
1551				'relaxed' straps the emulator for both legacy-NaN and
1552				2008-NaN, whereas 'strict' enables legacy-NaN only on
1553				legacy processors and both NaN encodings on MIPS32 or
1554				MIPS64 CPUs.
1556				The setting for ABS.fmt/NEG.fmt instruction execution
1557				mode generally follows that for the NaN encoding,
1558				except where unsupported by hardware.
1560		ignore_loglevel	[KNL]
1561				Ignore loglevel setting - this will print /all/
1562				kernel messages to the console. Useful for debugging.
1563				We also add it as printk module parameter, so users
1564				could change it dynamically, usually by
1565				/sys/module/printk/parameters/ignore_loglevel.
1567		ignore_rlimit_data
1568				Ignore RLIMIT_DATA setting for data mappings,
1569				print warning at first misuse.  Can be changed via
1570				/sys/module/kernel/parameters/ignore_rlimit_data.
1572		ihash_entries=	[KNL]
1573				Set number of hash buckets for inode cache.
1575		ima_appraise=	[IMA] appraise integrity measurements
1576				Format: { "off" | "enforce" | "fix" | "log" }
1577				default: "enforce"
1579		ima_appraise_tcb [IMA]
1580				The builtin appraise policy appraises all files
1581				owned by uid=0.
1583		ima_hash=	[IMA]
1584				Format: { md5 | sha1 | rmd160 | sha256 | sha384
1585					   | sha512 | ... }
1586				default: "sha1"
1588				The list of supported hash algorithms is defined
1589				in crypto/hash_info.h.
1591		ima_policy=	[IMA]
1592				The builtin measurement policy to load during IMA
1593				setup.  Specyfing "tcb" as the value, measures all
1594				programs exec'd, files mmap'd for exec, and all files
1595				opened with the read mode bit set by either the
1596				effective uid (euid=0) or uid=0.
1597				Format: "tcb"
1599		ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
1600				Load a policy which meets the needs of the Trusted
1601				Computing Base.  This means IMA will measure all
1602				programs exec'd, files mmap'd for exec, and all files
1603				opened for read by uid=0.
1605		ima_template=   [IMA]
1606				Select one of defined IMA measurements template formats.
1607				Formats: { "ima" | "ima-ng" | "ima-sig" }
1608				Default: "ima-ng"
1610		ima_template_fmt=
1611		                [IMA] Define a custom template format.
1612				Format: { "field1|...|fieldN" }
1614		ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1615				Format: <min_file_size>
1616				Set the minimal file size for using asynchronous hash.
1617				If left unspecified, ahash usage is disabled.
1619				ahash performance varies for different data sizes on
1620				different crypto accelerators. This option can be used
1621				to achieve the best performance for a particular HW.
1623		ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1624				Format: <bufsize>
1625				Set hashing buffer size. Default: 4k.
1627				ahash performance varies for different chunk sizes on
1628				different crypto accelerators. This option can be used
1629				to achieve best performance for particular HW.
1631		init=		[KNL]
1632				Format: <full_path>
1633				Run specified binary instead of /sbin/init as init
1634				process.
1636		initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
1637				for working out where the kernel is dying during
1638				startup.
1640		initcall_blacklist=  [KNL] Do not execute a comma-separated list of
1641				initcall functions.  Useful for debugging built-in
1642				modules and initcalls.
1644		initrd=		[BOOT] Specify the location of the initial ramdisk
1646		inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
1647				Format: <irq>
1649		int_pln_enable  [x86] Enable power limit notification interrupt
1651		integrity_audit=[IMA]
1652				Format: { "0" | "1" }
1653				0 -- basic integrity auditing messages. (Default)
1654				1 -- additional integrity auditing messages.
1656		intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1657			on
1658				Enable intel iommu driver.
1659			off
1660				Disable intel iommu driver.
1661			igfx_off [Default Off]
1662				By default, gfx is mapped as normal device. If a gfx
1663				device has a dedicated DMAR unit, the DMAR unit is
1664				bypassed by not enabling DMAR with this option. In
1665				this case, gfx device will use physical address for
1666				DMA.
1667			forcedac [x86_64]
1668				With this option iommu will not optimize to look
1669				for io virtual address below 32-bit forcing dual
1670				address cycle on pci bus for cards supporting greater
1671				than 32-bit addressing. The default is to look
1672				for translation below 32-bit and if not available
1673				then look in the higher range.
1674			strict [Default Off]
1675				With this option on every unmap_single operation will
1676				result in a hardware IOTLB flush operation as opposed
1677				to batching them for performance.
1678			sp_off [Default Off]
1679				By default, super page will be supported if Intel IOMMU
1680				has the capability. With this option, super page will
1681				not be supported.
1682			ecs_off [Default Off]
1683				By default, extended context tables will be supported if
1684				the hardware advertises that it has support both for the
1685				extended tables themselves, and also PASID support. With
1686				this option set, extended tables will not be used even
1687				on hardware which claims to support them.
1689		intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
1690				0	disables intel_idle and fall back on acpi_idle.
1691				1 to 6	specify maximum depth of C-state.
1693		intel_pstate=  [X86]
1694			       disable
1695			         Do not enable intel_pstate as the default
1696			         scaling driver for the supported processors
1697			       force
1698				 Enable intel_pstate on systems that prohibit it by default
1699				 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1700				 instead of acpi-cpufreq may disable platform features, such
1701				 as thermal controls and power capping, that rely on ACPI
1702				 P-States information being indicated to OSPM and therefore
1703				 should be used with caution. This option does not work with
1704				 processors that aren't supported by the intel_pstate driver
1705				 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1706			       no_hwp
1707			         Do not enable hardware P state control (HWP)
1708				 if available.
1709			hwp_only
1710				Only load intel_pstate on systems which support
1711				hardware P state control (HWP) if available.
1712			support_acpi_ppc
1713				Enforce ACPI _PPC performance limits. If the Fixed ACPI
1714				Description Table, specifies preferred power management
1715				profile as "Enterprise Server" or "Performance Server",
1716				then this feature is turned on by default.
1718		intremap=	[X86-64, Intel-IOMMU]
1719				on	enable Interrupt Remapping (default)
1720				off	disable Interrupt Remapping
1721				nosid	disable Source ID checking
1722				no_x2apic_optout
1723					BIOS x2APIC opt-out request will be ignored
1724				nopost	disable Interrupt Posting
1726		iomem=		Disable strict checking of access to MMIO memory
1727			strict	regions from userspace.
1728			relaxed
1730		iommu=		[x86]
1731			off
1732			force
1733			noforce
1734			biomerge
1735			panic
1736			nopanic
1737			merge
1738			nomerge
1739			forcesac
1740			soft
1741			pt		[x86, IA-64]
1742			nobypass	[PPC/POWERNV]
1743				Disable IOMMU bypass, using IOMMU for PCI devices.
1746		io7=		[HW] IO7 for Marvel based alpha systems
1747				See comment before marvel_specify_io7 in
1748				arch/alpha/kernel/core_marvel.c.
1750		io_delay=	[X86] I/O delay method
1751			0x80
1752				Standard port 0x80 based delay
1753			0xed
1754				Alternate port 0xed based delay (needed on some systems)
1755			udelay
1756				Simple two microseconds delay
1757			none
1758				No delay
1760		ip=		[IP_PNP]
1761				See Documentation/filesystems/nfs/nfsroot.txt.
1763		irqaffinity=	[SMP] Set the default irq affinity mask
1764				Format:
1765				<cpu number>,...,<cpu number>
1766				or
1767				<cpu number>-<cpu number>
1768				(must be a positive range in ascending order)
1769				or a mixture
1770				<cpu number>,...,<cpu number>-<cpu number>
1772		irqfixup	[HW]
1773				When an interrupt is not handled search all handlers
1774				for it. Intended to get systems with badly broken
1775				firmware running.
1777		irqpoll		[HW]
1778				When an interrupt is not handled search all handlers
1779				for it. Also check all handlers each timer
1780				interrupt. Intended to get systems with badly broken
1781				firmware running.
1783		isapnp=		[ISAPNP]
1784				Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1786		isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
1787				Format:
1788				<cpu number>,...,<cpu number>
1789				or
1790				<cpu number>-<cpu number>
1791				(must be a positive range in ascending order)
1792				or a mixture
1793				<cpu number>,...,<cpu number>-<cpu number>
1795				This option can be used to specify one or more CPUs
1796				to isolate from the general SMP balancing and scheduling
1797				algorithms. You can move a process onto or off an
1798				"isolated" CPU via the CPU affinity syscalls or cpuset.
1799				<cpu number> begins at 0 and the maximum value is
1800				"number of CPUs in system - 1".
1802				This option is the preferred way to isolate CPUs. The
1803				alternative -- manually setting the CPU mask of all
1804				tasks in the system -- can cause problems and
1805				suboptimal load balancer performance.
1807		iucv=		[HW,NET]
1809		ivrs_ioapic	[HW,X86_64]
1810				Provide an override to the IOAPIC-ID<->DEVICE-ID
1811				mapping provided in the IVRS ACPI table. For
1812				example, to map IOAPIC-ID decimal 10 to
1813				PCI device 00:14.0 write the parameter as:
1814					ivrs_ioapic[10]=00:14.0
1816		ivrs_hpet	[HW,X86_64]
1817				Provide an override to the HPET-ID<->DEVICE-ID
1818				mapping provided in the IVRS ACPI table. For
1819				example, to map HPET-ID decimal 0 to
1820				PCI device 00:14.0 write the parameter as:
1821					ivrs_hpet[0]=00:14.0
1823		ivrs_acpihid	[HW,X86_64]
1824				Provide an override to the ACPI-HID:UID<->DEVICE-ID
1825				mapping provided in the IVRS ACPI table. For
1826				example, to map UART-HID:UID AMD0020:0 to
1827				PCI device 00:14.5 write the parameter as:
1828					ivrs_acpihid[00:14.5]=AMD0020:0
1830		js=		[HW,JOY] Analog joystick
1831				See Documentation/input/joystick.txt.
1833		nokaslr		[KNL]
1834				When CONFIG_RANDOMIZE_BASE is set, this disables
1835				kernel and module base offset ASLR (Address Space
1836				Layout Randomization).
1838		keepinitrd	[HW,ARM]
1840		kernelcore=	[KNL,X86,IA-64,PPC]
1841				Format: nn[KMGTPE] | "mirror"
1842				This parameter
1843				specifies the amount of memory usable by the kernel
1844				for non-movable allocations.  The requested amount is
1845				spread evenly throughout all nodes in the system. The
1846				remaining memory in each node is used for Movable
1847				pages. In the event, a node is too small to have both
1848				kernelcore and Movable pages, kernelcore pages will
1849				take priority and other nodes will have a larger number
1850				of Movable pages.  The Movable zone is used for the
1851				allocation of pages that may be reclaimed or moved
1852				by the page migration subsystem.  This means that
1853				HugeTLB pages may not be allocated from this zone.
1854				Note that allocations like PTEs-from-HighMem still
1855				use the HighMem zone if it exists, and the Normal
1856				zone if it does not.
1858				Instead of specifying the amount of memory (nn[KMGTPE]),
1859				you can specify "mirror" option. In case "mirror"
1860				option is specified, mirrored (reliable) memory is used
1861				for non-movable allocations and remaining memory is used
1862				for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1863				so you can NOT specify nn[KMGTPE] and "mirror" at the same
1864				time.
1866		kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
1867				Format: <Controller#>[,poll interval]
1868				The controller # is the number of the ehci usb debug
1869				port as it is probed via PCI.  The poll interval is
1870				optional and is the number seconds in between
1871				each poll cycle to the debug port in case you need
1872				the functionality for interrupting the kernel with
1873				gdb or control-c on the dbgp connection.  When
1874				not using this parameter you use sysrq-g to break into
1875				the kernel debugger.
1877		kgdboc=		[KGDB,HW] kgdb over consoles.
1878				Requires a tty driver that supports console polling,
1879				or a supported polling keyboard driver (non-usb).
1880				 Serial only format: <serial_device>[,baud]
1881				 keyboard only format: kbd
1882				 keyboard and serial format: kbd,<serial_device>[,baud]
1883				Optional Kernel mode setting:
1884				 kms, kbd format: kms,kbd
1885				 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1887		kgdbwait	[KGDB] Stop kernel execution and enter the
1888				kernel debugger at the earliest opportunity.
1890		kmac=		[MIPS] korina ethernet MAC address.
1891				Configure the RouterBoard 532 series on-chip
1892				Ethernet adapter MAC address.
1894		kmemleak=	[KNL] Boot-time kmemleak enable/disable
1895				Valid arguments: on, off
1896				Default: on
1898				the default is off.
1900		kmemcheck=	[X86] Boot-time kmemcheck enable/disable/one-shot mode
1901				Valid arguments: 0, 1, 2
1902				kmemcheck=0 (disabled)
1903				kmemcheck=1 (enabled)
1904				kmemcheck=2 (one-shot mode)
1905				Default: 2 (one-shot mode)
1907		kstack=N	[X86] Print N words from the kernel stack
1908				in oops dumps.
1910		kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1911				Default is 0 (don't ignore, but inject #GP)
1913		kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
1914				KVM MMU at runtime.
1915				Default is 0 (off)
1917		kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
1918				Default is 1 (enabled)
1920		kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
1921				for all guests.
1922				Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1924		kvm-intel.ept=	[KVM,Intel] Disable extended page tables
1925				(virtualized MMU) support on capable Intel chips.
1926				Default is 1 (enabled)
1928		kvm-intel.emulate_invalid_guest_state=
1929				[KVM,Intel] Enable emulation of invalid guest states
1930				Default is 0 (disabled)
1932		kvm-intel.flexpriority=
1933				[KVM,Intel] Disable FlexPriority feature (TPR shadow).
1934				Default is 1 (enabled)
1936		kvm-intel.nested=
1937				[KVM,Intel] Enable VMX nesting (nVMX).
1938				Default is 0 (disabled)
1940		kvm-intel.unrestricted_guest=
1941				[KVM,Intel] Disable unrestricted guest feature
1942				(virtualized real and unpaged mode) on capable
1943				Intel chips. Default is 1 (enabled)
1945		kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
1946				feature (tagged TLBs) on capable Intel chips.
1947				Default is 1 (enabled)
1949		l2cr=		[PPC]
1951		l3cr=		[PPC]
1953		lapic		[X86-32,APIC] Enable the local APIC even if BIOS
1954				disabled it.
1956		lapic=		[x86,APIC] "notscdeadline" Do not use TSC deadline
1957				value for LAPIC timer one-shot implementation. Default
1958				back to the programmable timer unit in the LAPIC.
1960		lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
1961				in C2 power state.
1963		libata.dma=	[LIBATA] DMA control
1964				libata.dma=0	  Disable all PATA and SATA DMA
1965				libata.dma=1	  PATA and SATA Disk DMA only
1966				libata.dma=2	  ATAPI (CDROM) DMA only
1967				libata.dma=4	  Compact Flash DMA only
1968				Combinations also work, so libata.dma=3 enables DMA
1969				for disks and CDROMs, but not CFs.
1971		libata.ignore_hpa=	[LIBATA] Ignore HPA limit
1972				libata.ignore_hpa=0	  keep BIOS limits (default)
1973				libata.ignore_hpa=1	  ignore limits, using full disk
1975		libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
1976				when set.
1977				Format: <int>
1979		libata.force=	[LIBATA] Force configurations.  The format is comma
1980				separated list of "[ID:]VAL" where ID is
1981				PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1982				matching port, link or device.  Basically, it matches
1983				the ATA ID string printed on console by libata.  If
1984				the whole ID part is omitted, the last PORT and DEVICE
1985				values are used.  If ID hasn't been specified yet, the
1986				configuration applies to all ports, links and devices.
1988				If only DEVICE is omitted, the parameter applies to
1989				the port and all links and devices behind it.  DEVICE
1990				number of 0 either selects the first device or the
1991				first fan-out link behind PMP device.  It does not
1992				select the host link.  DEVICE number of 15 selects the
1993				host link and device attached to it.
1995				The VAL specifies the configuration to force.  As long
1996				as there's no ambiguity shortcut notation is allowed.
1997				For example, both 1.5 and 1.5G would work for 1.5Gbps.
1998				The following configurations can be forced.
2000				* Cable type: 40c, 80c, short40c, unk, ign or sata.
2001				  Any ID with matching PORT is used.
2003				* SATA link speed limit: 1.5Gbps or 3.0Gbps.
2005				* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2006				  udma[/][16,25,33,44,66,100,133] notation is also
2007				  allowed.
2009				* [no]ncq: Turn on or off NCQ.
2011				* [no]ncqtrim: Turn off queued DSM TRIM.
2013				* nohrst, nosrst, norst: suppress hard, soft
2014	                          and both resets.
2016				* rstonce: only attempt one reset during
2017				  hot-unplug link recovery
2019				* dump_id: dump IDENTIFY data.
2021				* atapi_dmadir: Enable ATAPI DMADIR bridge support
2023				* disable: Disable this device.
2025				If there are multiple matching configurations changing
2026				the same attribute, the last one is used.
2028		memblock=debug	[KNL] Enable memblock debug messages.
2030		load_ramdisk=	[RAM] List of ramdisks to load from floppy
2031				See Documentation/blockdev/ramdisk.txt.
2033		lockd.nlm_grace_period=P  [NFS] Assign grace period.
2034				Format: <integer>
2036		lockd.nlm_tcpport=N	[NFS] Assign TCP port.
2037				Format: <integer>
2039		lockd.nlm_timeout=T	[NFS] Assign timeout value.
2040				Format: <integer>
2042		lockd.nlm_udpport=M	[NFS] Assign UDP port.
2043				Format: <integer>
2045		locktorture.nreaders_stress= [KNL]
2046				Set the number of locking read-acquisition kthreads.
2047				Defaults to being automatically set based on the
2048				number of online CPUs.
2050		locktorture.nwriters_stress= [KNL]
2051				Set the number of locking write-acquisition kthreads.
2053		locktorture.onoff_holdoff= [KNL]
2054				Set time (s) after boot for CPU-hotplug testing.
2056		locktorture.onoff_interval= [KNL]
2057				Set time (s) between CPU-hotplug operations, or
2058				zero to disable CPU-hotplug testing.
2060		locktorture.shuffle_interval= [KNL]
2061				Set task-shuffle interval (jiffies).  Shuffling
2062				tasks allows some CPUs to go into dyntick-idle
2063				mode during the locktorture test.
2065		locktorture.shutdown_secs= [KNL]
2066				Set time (s) after boot system shutdown.  This
2067				is useful for hands-off automated testing.
2069		locktorture.stat_interval= [KNL]
2070				Time (s) between statistics printk()s.
2072		locktorture.stutter= [KNL]
2073				Time (s) to stutter testing, for example,
2074				specifying five seconds causes the test to run for
2075				five seconds, wait for five seconds, and so on.
2076				This tests the locking primitive's ability to
2077				transition abruptly to and from idle.
2079		locktorture.torture_runnable= [BOOT]
2080				Start locktorture running at boot time.
2082		locktorture.torture_type= [KNL]
2083				Specify the locking implementation to test.
2085		locktorture.verbose= [KNL]
2086				Enable additional printk() statements.
2088		logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
2089				Format: <irq>
2091		loglevel=	All Kernel Messages with a loglevel smaller than the
2092				console loglevel will be printed to the console. It can
2093				also be changed with klogd or other programs. The
2094				loglevels are defined as follows:
2096				0 (KERN_EMERG)		system is unusable
2097				1 (KERN_ALERT)		action must be taken immediately
2098				2 (KERN_CRIT)		critical conditions
2099				3 (KERN_ERR)		error conditions
2100				4 (KERN_WARNING)	warning conditions
2101				5 (KERN_NOTICE)		normal but significant condition
2102				6 (KERN_INFO)		informational
2103				7 (KERN_DEBUG)		debug-level messages
2105		log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
2106				in bytes.  n must be a power of two and greater
2107				than the minimal size. The minimal size is defined
2108				by LOG_BUF_SHIFT kernel config parameter. There is
2109				also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2110				that allows to increase the default size depending on
2111				the number of CPUs. See init/Kconfig for more details.
2113		logo.nologo	[FB] Disables display of the built-in Linux logo.
2114				This may be used to provide more screen space for
2115				kernel log messages and is useful when debugging
2116				kernel boot problems.
2118		lp=0		[LP]	Specify parallel ports to use, e.g,
2119		lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
2120		lp=reset		first parallel port). 'lp=0' disables the
2121		lp=auto			printer driver. 'lp=reset' (which can be
2122					specified in addition to the ports) causes
2123					attached printers to be reset. Using
2124					lp=port1,port2,... specifies the parallel ports
2125					to associate lp devices with, starting with
2126					lp0. A port specification may be 'none' to skip
2127					that lp device, or a parport name such as
2128					'parport0'. Specifying 'lp=auto' instead of a
2129					port specification list means that device IDs
2130					from each port should be examined, to see if
2131					an IEEE 1284-compliant printer is attached; if
2132					so, the driver will manage that printer.
2133					See also header of drivers/char/lp.c.
2135		lpj=n		[KNL]
2136				Sets loops_per_jiffy to given constant, thus avoiding
2137				time-consuming boot-time autodetection (up to 250 ms per
2138				CPU). 0 enables autodetection (default). To determine
2139				the correct value for your kernel, boot with normal
2140				autodetection and see what value is printed. Note that
2141				on SMP systems the preset will be applied to all CPUs,
2142				which is likely to cause problems if your CPUs need
2143				significantly divergent settings. An incorrect value
2144				will cause delays in the kernel to be wrong, leading to
2145				unpredictable I/O errors and other breakage. Although
2146				unlikely, in the extreme case this might damage your
2147				hardware.
2149		ltpc=		[NET]
2150				Format: <io>,<irq>,<dma>
2152		machvec=	[IA-64] Force the use of a particular machine-vector
2153				(machvec) in a generic kernel.
2154				Example: machvec=hpzx1_swiotlb
2156		machtype=	[Loongson] Share the same kernel image file between different
2157				 yeeloong laptop.
2158				Example: machtype=lemote-yeeloong-2f-7inch
2160		max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
2161				than or equal to this physical address is ignored.
2163		maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
2164				should make use of.  maxcpus=n : n >= 0 limits the
2165				kernel to using 'n' processors.  n=0 is a special case,
2166				it is equivalent to "nosmp", which also disables
2167				the IO APIC.
2169		max_loop=	[LOOP] The number of loop block devices that get
2170		(loop.max_loop)	unconditionally pre-created at init time. The default
2171				number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2172				of statically allocating a predefined number, loop
2173				devices can be requested on-demand with the
2174				/dev/loop-control interface.
2176		mce		[X86-32] Machine Check Exception
2178		mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
2180		md=		[HW] RAID subsystems devices and level
2181				See Documentation/md.txt.
2183		mdacon=		[MDA]
2184				Format: <first>,<last>
2185				Specifies range of consoles to be captured by the MDA.
2187		mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
2188				Amount of memory to be used when the kernel is not able
2189				to see the whole system memory or for test.
2190				[X86] Work as limiting max address. Use together
2191				with memmap= to avoid physical address space collisions.
2192				Without memmap= PCI devices could be placed at addresses
2193				belonging to unused RAM.
2195		mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
2196				memory.
2198		memchunk=nn[KMG]
2199				[KNL,SH] Allow user to override the default size for
2200				per-device physically contiguous DMA buffers.
2202	        memhp_default_state=online/offline
2203				[KNL] Set the initial state for the memory hotplug
2204				onlining policy. If not specified, the default value is
2205				set according to the
2207				option.
2208				See Documentation/memory-hotplug.txt.
2210		memmap=exactmap	[KNL,X86] Enable setting of an exact
2211				E820 memory map, as specified by the user.
2212				Such memmap=exactmap lines can be constructed based on
2213				BIOS output or other requirements. See the memmap=nn@ss
2214				option description.
2216		memmap=nn[KMG]@ss[KMG]
2217				[KNL] Force usage of a specific region of memory.
2218				Region of memory to be used is from ss to ss+nn.
2220		memmap=nn[KMG]#ss[KMG]
2221				[KNL,ACPI] Mark specific memory as ACPI data.
2222				Region of memory to be marked is from ss to ss+nn.
2224		memmap=nn[KMG]$ss[KMG]
2225				[KNL,ACPI] Mark specific memory as reserved.
2226				Region of memory to be reserved is from ss to ss+nn.
2227				Example: Exclude memory from 0x18690000-0x1869ffff
2228				         memmap=64K$0x18690000
2229				         or
2230				         memmap=0x10000$0x18690000
2232		memmap=nn[KMG]!ss[KMG]
2233				[KNL,X86] Mark specific memory as protected.
2234				Region of memory to be used, from ss to ss+nn.
2235				The memory region may be marked as e820 type 12 (0xc)
2236				and is NVDIMM or ADR memory.
2238		memory_corruption_check=0/1 [X86]
2239				Some BIOSes seem to corrupt the first 64k of
2240				memory when doing things like suspend/resume.
2241				Setting this option will scan the memory
2242				looking for corruption.  Enabling this will
2243				both detect corruption and prevent the kernel
2244				from using the memory being corrupted.
2245				However, its intended as a diagnostic tool; if
2246				repeatable BIOS-originated corruption always
2247				affects the same memory, you can use memmap=
2248				to prevent the kernel from using that memory.
2250		memory_corruption_check_size=size [X86]
2251				By default it checks for corruption in the low
2252				64k, making this memory unavailable for normal
2253				use.  Use this parameter to scan for
2254				corruption in more or less memory.
2256		memory_corruption_check_period=seconds [X86]
2257				By default it checks for corruption every 60
2258				seconds.  Use this parameter to check at some
2259				other rate.  0 disables periodic checking.
2261		memtest=	[KNL,X86,ARM] Enable memtest
2262				Format: <integer>
2263				default : 0 <disable>
2264				Specifies the number of memtest passes to be
2265				performed. Each pass selects another test
2266				pattern from a given set of patterns. Memtest
2267				fills the memory with this pattern, validates
2268				memory contents and reserves bad memory
2269				regions that are detected.
2271		meye.*=		[HW] Set MotionEye Camera parameters
2272				See Documentation/video4linux/meye.txt.
2274		mfgpt_irq=	[IA-32] Specify the IRQ to use for the
2275				Multi-Function General Purpose Timers on AMD Geode
2276				platforms.
2278		mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
2279				the BIOS has incorrectly applied a workaround. TinyBIOS
2280				version 0.98 is known to be affected, 0.99 fixes the
2281				problem by letting the user disable the workaround.
2283		mga=		[HW,DRM]
2285		min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
2286				physical address is ignored.
2288		mini2440=	[ARM,HW,KNL]
2289				Format:[0..2][b][c][t]
2290				Default: "0tb"
2291				MINI2440 configuration specification:
2292				0 - The attached screen is the 3.5" TFT
2293				1 - The attached screen is the 7" TFT
2294				2 - The VGA Shield is attached (1024x768)
2295				Leaving out the screen size parameter will not load
2296				the TFT driver, and the framebuffer will be left
2297				unconfigured.
2298				b - Enable backlight. The TFT backlight pin will be
2299				linked to the kernel VESA blanking code and a GPIO
2300				LED. This parameter is not necessary when using the
2301				VGA shield.
2302				c - Enable the s3c camera interface.
2303				t - Reserved for enabling touchscreen support. The
2304				touchscreen support is not enabled in the mainstream
2305				kernel as of 2.6.30, a preliminary port can be found
2306				in the "bleeding edge" mini2440 support kernel at
2307				http://repo.or.cz/w/linux-2.6/mini2440.git
2309		mminit_loglevel=
2310				[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2311				parameter allows control of the logging verbosity for
2312				the additional memory initialisation checks. A value
2313				of 0 disables mminit logging and a level of 4 will
2314				log everything. Information is printed at KERN_DEBUG
2315				so loglevel=8 may also need to be specified.
2317		module.sig_enforce
2318				[KNL] When CONFIG_MODULE_SIG is set, this means that
2319				modules without (valid) signatures will fail to load.
2320				Note that if CONFIG_MODULE_SIG_FORCE is set, that
2321				is always true, so this option does nothing.
2323		module_blacklist=  [KNL] Do not load a comma-separated list of
2324				modules.  Useful for debugging problem modules.
2326		mousedev.tap_time=
2327				[MOUSE] Maximum time between finger touching and
2328				leaving touchpad surface for touch to be considered
2329				a tap and be reported as a left button click (for
2330				touchpads working in absolute mode only).
2331				Format: <msecs>
2332		mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
2333				reporting absolute coordinates, such as tablets
2334		mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
2335				reporting absolute coordinates, such as tablets
2337		movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
2338				is similar to kernelcore except it specifies the
2339				amount of memory used for migratable allocations.
2340				If both kernelcore and movablecore is specified,
2341				then kernelcore will be at *least* the specified
2342				value but may be more. If movablecore on its own
2343				is specified, the administrator must be careful
2344				that the amount of memory usable for all allocations
2345				is not too small.
2347		movable_node	[KNL,X86] Boot-time switch to enable the effects
2348				of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2350		MTD_Partition=	[MTD]
2351				Format: <name>,<region-number>,<size>,<offset>
2353		MTD_Region=	[MTD] Format:
2354				<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2356		mtdparts=	[MTD]
2357				See drivers/mtd/cmdlinepart.c.
2359		multitce=off	[PPC]  This parameter disables the use of the pSeries
2360				firmware feature for updating multiple TCE entries
2361				at a time.
2363		onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
2365				Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2367				boundary - index of last SLC block on Flex-OneNAND.
2368					   The remaining blocks are configured as MLC blocks.
2369				lock	 - Configure if Flex-OneNAND boundary should be locked.
2370					   Once locked, the boundary cannot be changed.
2371					   1 indicates lock status, 0 indicates unlock status.
2373		mtdset=		[ARM]
2374				ARM/S3C2412 JIVE boot control
2376				See arch/arm/mach-s3c2412/mach-jive.c
2378		mtouchusb.raw_coordinates=
2379				[HW] Make the MicroTouch USB driver use raw coordinates
2380				('y', default) or cooked coordinates ('n')
2382		mtrr_chunk_size=nn[KMG] [X86]
2383				used for mtrr cleanup. It is largest continuous chunk
2384				that could hold holes aka. UC entries.
2386		mtrr_gran_size=nn[KMG] [X86]
2387				Used for mtrr cleanup. It is granularity of mtrr block.
2388				Default is 1.
2389				Large value could prevent small alignment from
2390				using up MTRRs.
2392		mtrr_spare_reg_nr=n [X86]
2393				Format: <integer>
2394				Range: 0,7 : spare reg number
2395				Default : 1
2396				Used for mtrr cleanup. It is spare mtrr entries number.
2397				Set to 2 or more if your graphical card needs more.
2399		n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
2401		netdev=		[NET] Network devices parameters
2402				Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2403				Note that mem_start is often overloaded to mean
2404				something different and driver-specific.
2405				This usage is only documented in each driver source
2406				file if at all.
2408		nf_conntrack.acct=
2409				[NETFILTER] Enable connection tracking flow accounting
2410				0 to disable accounting
2411				1 to enable accounting
2412				Default value is 0.
2414		nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
2415				See Documentation/filesystems/nfs/nfsroot.txt.
2417		nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
2418				See Documentation/filesystems/nfs/nfsroot.txt.
2420		nfsrootdebug	[NFS] enable nfsroot debugging messages.
2421				See Documentation/filesystems/nfs/nfsroot.txt.
2423		nfs.callback_tcpport=
2424				[NFS] set the TCP port on which the NFSv4 callback
2425				channel should listen.
2427		nfs.cache_getent=
2428				[NFS] sets the pathname to the program which is used
2429				to update the NFS client cache entries.
2431		nfs.cache_getent_timeout=
2432				[NFS] sets the timeout after which an attempt to
2433				update a cache entry is deemed to have failed.
2435		nfs.idmap_cache_timeout=
2436				[NFS] set the maximum lifetime for idmapper cache
2437				entries.
2439		nfs.enable_ino64=
2440				[NFS] enable 64-bit inode numbers.
2441				If zero, the NFS client will fake up a 32-bit inode
2442				number for the readdir() and stat() syscalls instead
2443				of returning the full 64-bit number.
2444				The default is to return 64-bit inode numbers.
2446		nfs.max_session_slots=
2447				[NFSv4.1] Sets the maximum number of session slots
2448				the client will attempt to negotiate with the server.
2449				This limits the number of simultaneous RPC requests
2450				that the client can send to the NFSv4.1 server.
2451				Note that there is little point in setting this
2452				value higher than the max_tcp_slot_table_limit.
2454		nfs.nfs4_disable_idmapping=
2455				[NFSv4] When set to the default of '1', this option
2456				ensures that both the RPC level authentication
2457				scheme and the NFS level operations agree to use
2458				numeric uids/gids if the mount is using the
2459				'sec=sys' security flavour. In effect it is
2460				disabling idmapping, which can make migration from
2461				legacy NFSv2/v3 systems to NFSv4 easier.
2462				Servers that do not support this mode of operation
2463				will be autodetected by the client, and it will fall
2464				back to using the idmapper.
2465				To turn off this behaviour, set the value to '0'.
2466		nfs.nfs4_unique_id=
2467				[NFS4] Specify an additional fixed unique ident-
2468				ification string that NFSv4 clients can insert into
2469				their nfs_client_id4 string.  This is typically a
2470				UUID that is generated at system install time.
2472		nfs.send_implementation_id =
2473				[NFSv4.1] Send client implementation identification
2474				information in exchange_id requests.
2475				If zero, no implementation identification information
2476				will be sent.
2477				The default is to send the implementation identification
2478				information.
2480		nfs.recover_lost_locks =
2481				[NFSv4] Attempt to recover locks that were lost due
2482				to a lease timeout on the server. Please note that
2483				doing this risks data corruption, since there are
2484				no guarantees that the file will remain unchanged
2485				after the locks are lost.
2486				If you want to enable the kernel legacy behaviour of
2487				attempting to recover these locks, then set this
2488				parameter to '1'.
2489				The default parameter value of '0' causes the kernel
2490				not to attempt recovery of lost locks.
2492		nfs4.layoutstats_timer =
2493				[NFSv4.2] Change the rate at which the kernel sends
2494				layoutstats to the pNFS metadata server.
2496				Setting this to value to 0 causes the kernel to use
2497				whatever value is the default set by the layout
2498				driver. A non-zero value sets the minimum interval
2499				in seconds between layoutstats transmissions.
2501		nfsd.nfs4_disable_idmapping=
2502				[NFSv4] When set to the default of '1', the NFSv4
2503				server will return only numeric uids and gids to
2504				clients using auth_sys, and will accept numeric uids
2505				and gids from such clients.  This is intended to ease
2506				migration from NFSv2/v3.
2508		objlayoutdriver.osd_login_prog=
2509				[NFS] [OBJLAYOUT] sets the pathname to the program which
2510				is used to automatically discover and login into new
2511				osd-targets. Please see:
2512				Documentation/filesystems/pnfs.txt for more explanations
2514		nmi_debug=	[KNL,AVR32,SH] Specify one or more actions to take
2515				when a NMI is triggered.
2516				Format: [state][,regs][,debounce][,die]
2518		nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
2519				Format: [panic,][nopanic,][num]
2520				Valid num: 0 or 1
2521				0 - turn hardlockup detector in nmi_watchdog off
2522				1 - turn hardlockup detector in nmi_watchdog on
2523				When panic is specified, panic when an NMI watchdog
2524				timeout occurs (or 'nopanic' to override the opposite
2525				default). To disable both hard and soft lockup detectors,
2526				please see 'nowatchdog'.
2527				This is useful when you use a panic=... timeout and
2528				need the box quickly up again.
2530		netpoll.carrier_timeout=
2531				[NET] Specifies amount of time (in seconds) that
2532				netpoll should wait for a carrier. By default netpoll
2533				waits 4 seconds.
2535		no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
2536				emulation library even if a 387 maths coprocessor
2537				is present.
2539		no_console_suspend
2540				[HW] Never suspend the console
2541				Disable suspending of consoles during suspend and
2542				hibernate operations.  Once disabled, debugging
2543				messages can reach various consoles while the rest
2544				of the system is being put to sleep (ie, while
2545				debugging driver suspend/resume hooks).  This may
2546				not work reliably with all consoles, but is known
2547				to work with serial and VGA consoles.
2548				To facilitate more flexible debugging, we also add
2549				console_suspend, a printk module parameter to control
2550				it. Users could use console_suspend (usually
2551				/sys/module/printk/parameters/console_suspend) to
2552				turn on/off it dynamically.
2554		noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
2555				caches in the slab allocator.  Saves per-node memory,
2556				but will impact performance.
2558		noalign		[KNL,ARM]
2560		noapic		[SMP,APIC] Tells the kernel to not make use of any
2561				IOAPICs that may be present in the system.
2563		noautogroup	Disable scheduler automatic task group creation.
2565		nobats		[PPC] Do not use BATs for mapping kernel lowmem
2566				on "Classic" PPC cores.
2568		nocache		[ARM]
2570		noclflush	[BUGS=X86] Don't use the CLFLUSH instruction
2572		nodelayacct	[KNL] Disable per-task delay accounting
2574		nodisconnect	[HW,SCSI,M68K] Disables SCSI disconnects.
2576		nodsp		[SH] Disable hardware DSP at boot time.
2578		noefi		Disable EFI runtime services support.
2580		noexec		[IA-64]
2582		noexec		[X86]
2583				On X86-32 available only on PAE configured kernels.
2584				noexec=on: enable non-executable mappings (default)
2585				noexec=off: disable non-executable mappings
2587		nosmap		[X86]
2588				Disable SMAP (Supervisor Mode Access Prevention)
2589				even if it is supported by processor.
2591		nosmep		[X86]
2592				Disable SMEP (Supervisor Mode Execution Prevention)
2593				even if it is supported by processor.
2595		noexec32	[X86-64]
2596				This affects only 32-bit executables.
2597				noexec32=on: enable non-executable mappings (default)
2598					read doesn't imply executable mappings
2599				noexec32=off: disable non-executable mappings
2600					read implies executable mappings
2602		nofpu		[MIPS,SH] Disable hardware FPU at boot time.
2604		nofxsr		[BUGS=X86-32] Disables x86 floating point extended
2605				register save and restore. The kernel will only save
2606				legacy floating-point registers on task switch.
2608		nohugeiomap	[KNL,x86] Disable kernel huge I/O mappings.
2610		nosmt		[KNL,S390] Disable symmetric multithreading (SMT).
2611				Equivalent to smt=1.
2613		noxsave		[BUGS=X86] Disables x86 extended register state save
2614				and restore using xsave. The kernel will fallback to
2615				enabling legacy floating-point and sse state.
2617		noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
2618				register states. The kernel will fall back to use
2619				xsave to save the states. By using this parameter,
2620				performance of saving the states is degraded because
2621				xsave doesn't support modified optimization while
2622				xsaveopt supports it on xsaveopt enabled systems.
2624		noxsaves	[X86] Disables xsaves and xrstors used in saving and
2625				restoring x86 extended register state in compacted
2626				form of xsave area. The kernel will fall back to use
2627				xsaveopt and xrstor to save and restore the states
2628				in standard form of xsave area. By using this
2629				parameter, xsave area per process might occupy more
2630				memory on xsaves enabled systems.
2632		nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2633				wfi(ARM) instruction doesn't work correctly and not to
2634				use it. This is also useful when using JTAG debugger.
2636		no_file_caps	Tells the kernel not to honor file capabilities.  The
2637				only way then for a file to be executed with privilege
2638				is to be setuid root or executed by root.
2640		nohalt		[IA-64] Tells the kernel not to use the power saving
2641				function PAL_HALT_LIGHT when idle. This increases
2642				power-consumption. On the positive side, it reduces
2643				interrupt wake-up latency, which may improve performance
2644				in certain environments such as networked servers or
2645				real-time systems.
2647		nohibernate	[HIBERNATION] Disable hibernation and resume.
2649		nohz=		[KNL] Boottime enable/disable dynamic ticks
2650				Valid arguments: on, off
2651				Default: on
2653		nohz_full=	[KNL,BOOT]
2654				In kernels built with CONFIG_NO_HZ_FULL=y, set
2655				the specified list of CPUs whose tick will be stopped
2656				whenever possible. The boot CPU will be forced outside
2657				the range to maintain the timekeeping.
2658				The CPUs in this range must also be included in the
2659				rcu_nocbs= set.
2661		noiotrap	[SH] Disables trapped I/O port accesses.
2663		noirqdebug	[X86-32] Disables the code which attempts to detect and
2664				disable unhandled interrupt sources.
2666		no_timer_check	[X86,APIC] Disables the code which tests for
2667				broken timer IRQ sources.
2669		noisapnp	[ISAPNP] Disables ISA PnP code.
2671		noinitrd	[RAM] Tells the kernel not to load any configured
2672				initial RAM disk.
2674		nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
2675				remapping.
2676				[Deprecated - use intremap=off]
2678		nointroute	[IA-64]
2680		noinvpcid	[X86] Disable the INVPCID cpu feature.
2682		nojitter	[IA-64] Disables jitter checking for ITC timers.
2684		no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
2686		no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
2687				fault handling.
2689		no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
2690				steal time is computed, but won't influence scheduler
2691				behaviour
2693		nolapic		[X86-32,APIC] Do not enable or use the local APIC.
2695		nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
2697		noltlbs		[PPC] Do not use large page/tlb entries for kernel
2698				lowmem mapping on PPC40x and PPC8xx
2700		nomca		[IA-64] Disable machine check abort handling
2702		nomce		[X86-32] Disable Machine Check Exception
2704		nomfgpt		[X86-32] Disable Multi-Function General Purpose
2705				Timer usage (for AMD Geode machines).
2707		nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
2708				shutdown the other cpus.  Instead use the REBOOT_VECTOR
2709				irq.
2711		nomodule	Disable module load
2713		nopat		[X86] Disable PAT (page attribute table extension of
2714				pagetables) support.
2716		norandmaps	Don't use address space randomization.  Equivalent to
2717				echo 0 > /proc/sys/kernel/randomize_va_space
2719		noreplace-paravirt	[X86,IA-64,PV_OPS] Don't patch paravirt_ops
2721		noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
2722				with UP alternatives
2724		nordrand	[X86] Disable kernel use of the RDRAND and
2725				RDSEED instructions even if they are supported
2726				by the processor.  RDRAND and RDSEED are still
2727				available to user space applications.
2729		noresume	[SWSUSP] Disables resume and restores original swap
2730				space.
2732		no-scroll	[VGA] Disables scrollback.
2733				This is required for the Braillex ib80-piezo Braille
2734				reader made by F.H. Papenmeier (Germany).
2736		nosbagart	[IA-64]
2738		nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2740		nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
2741				and disable the IO APIC.  legacy for "maxcpus=0".
2743		nosoftlockup	[KNL] Disable the soft-lockup detector.
2745		nosync		[HW,M68K] Disables sync negotiation for all devices.
2747		notsc		[BUGS=X86-32] Disable Time Stamp Counter
2749		nowatchdog	[KNL] Disable both lockup detectors, i.e.
2750	                        soft-lockup and NMI watchdog (hard-lockup).
2752		nowb		[ARM]
2754		nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
2756		cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
2758				Some features depend on CPU0. Known dependencies are:
2759				1. Resume from suspend/hibernate depends on CPU0.
2760				Suspend/hibernate will fail if CPU0 is offline and you
2761				need to online CPU0 before suspend/hibernate.
2762				2. PIC interrupts also depend on CPU0. CPU0 can't be
2763				removed if a PIC interrupt is detected.
2764				It's said poweroff/reboot may depend on CPU0 on some
2765				machines although I haven't seen such issues so far
2766				after CPU0 is offline on a few tested machines.
2767				If the dependencies are under your control, you can
2768				turn on cpu0_hotplug.
2770		nptcg=		[IA-64] Override max number of concurrent global TLB
2771				purges which is reported from either PAL_VM_SUMMARY or
2772				SAL PALO.
2774		nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
2775				could support.  nr_cpus=n : n >= 1 limits the kernel to
2776				supporting 'n' processors. Later in runtime you can not
2777				use hotplug cpu feature to put more cpu back to online.
2778				just like you compile the kernel NR_CPUS=n
2780		nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
2782		numa_balancing=	[KNL,X86] Enable or disable automatic NUMA balancing.
2783				Allowed values are enable and disable
2785		numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2786				one of ['zone', 'node', 'default'] can be specified
2787				This can be set from sysctl after boot.
2788				See Documentation/sysctl/vm.txt for details.
2790		ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
2791				See Documentation/debugging-via-ohci1394.txt for more
2792				info.
2794		olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2795				Rather than timing out after 20 ms if an EC
2796				command is not properly ACKed, override the length
2797				of the timeout.  We have interrupts disabled while
2798				waiting for the ACK, so if this is set too high
2799				interrupts *may* be lost!
2801		omap_mux=	[OMAP] Override bootloader pin multiplexing.
2802				Format: <mux_mode0.mode_name=value>...
2803				For example, to override I2C bus2:
2804				omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2806		oprofile.timer=	[HW]
2807				Use timer interrupt instead of performance counters
2809		oprofile.cpu_type=	Force an oprofile cpu type
2810				This might be useful if you have an older oprofile
2811				userland or if you want common events.
2812				Format: { arch_perfmon }
2813				arch_perfmon: [X86] Force use of architectural
2814					perfmon on Intel CPUs instead of the
2815					CPU specific event set.
2816				timer: [X86] Force use of architectural NMI
2817					timer mode (see also oprofile.timer
2818					for generic hr timer mode)
2820		oops=panic	Always panic on oopses. Default is to just kill the
2821				process, but there is a small probability of
2822				deadlocking the machine.
2823				This will also cause panics on machine check exceptions.
2824				Useful together with panic=30 to trigger a reboot.
2826		OSS		[HW,OSS]
2827				See Documentation/sound/oss/oss-parameters.txt
2829		page_owner=	[KNL] Boot-time page_owner enabling option.
2830				Storage of the information about who allocated
2831				each page is disabled in default. With this switch,
2832				we can turn it on.
2833				on: enable the feature
2835		page_poison=	[KNL] Boot-time parameter changing the state of
2836				poisoning on the buddy allocator.
2837				off: turn off poisoning
2838				on: turn on poisoning
2840		panic=		[KNL] Kernel behaviour on panic: delay <timeout>
2841				timeout > 0: seconds before rebooting
2842				timeout = 0: wait forever
2843				timeout < 0: reboot immediately
2844				Format: <timeout>
2846		panic_on_warn	panic() instead of WARN().  Useful to cause kdump
2847				on a WARN().
2849		crash_kexec_post_notifiers
2850				Run kdump after running panic-notifiers and dumping
2851				kmsg. This only for the users who doubt kdump always
2852				succeeds in any situation.
2853				Note that this also increases risks of kdump failure,
2854				because some panic notifiers can make the crashed
2855				kernel more unstable.
2857		parkbd.port=	[HW] Parallel port number the keyboard adapter is
2858				connected to, default is 0.
2859				Format: <parport#>
2860		parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
2861				0 for XT, 1 for AT (default is AT).
2862				Format: <mode>
2864		parport=	[HW,PPT] Specify parallel ports. 0 disables.
2865				Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2866				Use 'auto' to force the driver to use any
2867				IRQ/DMA settings detected (the default is to
2868				ignore detected IRQ/DMA settings because of
2869				possible conflicts). You can specify the base
2870				address, IRQ, and DMA settings; IRQ and DMA
2871				should be numbers, or 'auto' (for using detected
2872				settings on that particular port), or 'nofifo'
2873				(to avoid using a FIFO even if it is detected).
2874				Parallel ports are assigned in the order they
2875				are specified on the command line, starting
2876				with parport0.
2878		parport_init_mode=	[HW,PPT]
2879				Configure VIA parallel port to operate in
2880				a specific mode. This is necessary on Pegasos
2881				computer where firmware has no options for setting
2882				up parallel port mode and sets it to spp.
2883				Currently this function knows 686a and 8231 chips.
2884				Format: [spp|ps2|epp|ecp|ecpepp]
2886		pause_on_oops=
2887				Halt all CPUs after the first oops has been printed for
2888				the specified number of seconds.  This is to be used if
2889				your oopses keep scrolling off the screen.
2891		pcbit=		[HW,ISDN]
2893		pcd.		[PARIDE]
2894				See header of drivers/block/paride/pcd.c.
2895				See also Documentation/blockdev/paride.txt.
2897		pci=option[,option...]	[PCI] various PCI subsystem options:
2898			earlydump	[X86] dump PCI config space before the kernel
2899				        changes anything
2900			off		[X86] don't probe for the PCI bus
2901			bios		[X86-32] force use of PCI BIOS, don't access
2902					the hardware directly. Use this if your machine
2903					has a non-standard PCI host bridge.
2904			nobios		[X86-32] disallow use of PCI BIOS, only direct
2905					hardware access methods are allowed. Use this
2906					if you experience crashes upon bootup and you
2907					suspect they are caused by the BIOS.
2908			conf1		[X86] Force use of PCI Configuration Access
2909					Mechanism 1 (config address in IO port 0xCF8,
2910					data in IO port 0xCFC, both 32-bit).
2911			conf2		[X86] Force use of PCI Configuration Access
2912					Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2913					the function, IO port 0xCFA, also 8-bit, sets
2914					bus number. The config space is then accessed
2915					through ports 0xC000-0xCFFF).
2916					See http://wiki.osdev.org/PCI for more info
2917					on the configuration access mechanisms.
2918			noaer		[PCIE] If the PCIEAER kernel config parameter is
2919					enabled, this kernel boot option can be used to
2920					disable the use of PCIE advanced error reporting.
2921			nodomains	[PCI] Disable support for multiple PCI
2922					root domains (aka PCI segments, in ACPI-speak).
2923			nommconf	[X86] Disable use of MMCONFIG for PCI
2924					Configuration
2925			check_enable_amd_mmconf [X86] check for and enable
2926					properly configured MMIO access to PCI
2927					config space on AMD family 10h CPU
2928			nomsi		[MSI] If the PCI_MSI kernel config parameter is
2929					enabled, this kernel boot option can be used to
2930					disable the use of MSI interrupts system-wide.
2931			noioapicquirk	[APIC] Disable all boot interrupt quirks.
2932					Safety option to keep boot IRQs enabled. This
2933					should never be necessary.
2934			ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
2935					primary IO-APIC for bridges that cannot disable
2936					boot IRQs. This fixes a source of spurious IRQs
2937					when the system masks IRQs.
2938			noioapicreroute	[APIC] Disable workaround that uses the
2939					boot IRQ equivalent of an IRQ that connects to
2940					a chipset where boot IRQs cannot be disabled.
2941					The opposite of ioapicreroute.
2942			biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
2943					routing table. These calls are known to be buggy
2944					on several machines and they hang the machine
2945					when used, but on other computers it's the only
2946					way to get the interrupt routing table. Try
2947					this option if the kernel is unable to allocate
2948					IRQs or discover secondary PCI buses on your
2949					motherboard.
2950			rom		[X86] Assign address space to expansion ROMs.
2951					Use with caution as certain devices share
2952					address decoders between ROMs and other
2953					resources.
2954			norom		[X86] Do not assign address space to
2955					expansion ROMs that do not already have
2956					BIOS assigned address ranges.
2957			nobar		[X86] Do not assign address space to the
2958					BARs that weren't assigned by the BIOS.
2959			irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
2960					assigned automatically to PCI devices. You can
2961					make the kernel exclude IRQs of your ISA cards
2962					this way.
2963			pirqaddr=0xAAAAA	[X86] Specify the physical address
2964					of the PIRQ table (normally generated
2965					by the BIOS) if it is outside the
2966					F0000h-100000h range.
2967			lastbus=N	[X86] Scan all buses thru bus #N. Can be
2968					useful if the kernel is unable to find your
2969					secondary buses and you want to tell it
2970					explicitly which ones they are.
2971			assign-busses	[X86] Always assign all PCI bus
2972					numbers ourselves, overriding
2973					whatever the firmware may have done.
2974			usepirqmask	[X86] Honor the possible IRQ mask stored
2975					in the BIOS $PIR table. This is needed on
2976					some systems with broken BIOSes, notably
2977					some HP Pavilion N5400 and Omnibook XE3
2978					notebooks. This will have no effect if ACPI
2979					IRQ routing is enabled.
2980			noacpi		[X86] Do not use ACPI for IRQ routing
2981					or for PCI scanning.
2982			use_crs		[X86] Use PCI host bridge window information
2983					from ACPI.  On BIOSes from 2008 or later, this
2984					is enabled by default.  If you need to use this,
2985					please report a bug.
2986			nocrs		[X86] Ignore PCI host bridge windows from ACPI.
2987				        If you need to use this, please report a bug.
2988			routeirq	Do IRQ routing for all PCI devices.
2989					This is normally done in pci_enable_device(),
2990					so this option is a temporary workaround
2991					for broken drivers that don't call it.
2992			skip_isa_align	[X86] do not align io start addr, so can
2993					handle more pci cards
2994			noearly		[X86] Don't do any early type 1 scanning.
2995					This might help on some broken boards which
2996					machine check when some devices' config space
2997					is read. But various workarounds are disabled
2998					and some IOMMU drivers will not work.
2999			bfsort		Sort PCI devices into breadth-first order.
3000					This sorting is done to get a device
3001					order compatible with older (<= 2.4) kernels.
3002			nobfsort	Don't sort PCI devices into breadth-first order.
3003			pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
3004					tuning and use the BIOS-configured MPS defaults.
3005			pcie_bus_safe	Set every device's MPS to the largest value
3006					supported by all devices below the root complex.
3007			pcie_bus_perf	Set device MPS to the largest allowable MPS
3008					based on its parent bus. Also set MRRS (Max
3009					Read Request Size) to the largest supported
3010					value (no larger than the MPS that the device
3011					or bus can support) for best performance.
3012			pcie_bus_peer2peer	Set every device's MPS to 128B, which
3013					every device is guaranteed to support. This
3014					configuration allows peer-to-peer DMA between
3015					any pair of devices, possibly at the cost of
3016					reduced performance.  This also guarantees
3017					that hot-added devices will work.
3018			cbiosize=nn[KMG]	The fixed amount of bus space which is
3019					reserved for the CardBus bridge's IO window.
3020					The default value is 256 bytes.
3021			cbmemsize=nn[KMG]	The fixed amount of bus space which is
3022					reserved for the CardBus bridge's memory
3023					window. The default value is 64 megabytes.
3024			resource_alignment=
3025					Format:
3026					[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
3027					[<order of align>@]pci:<vendor>:<device>\
3028							[:<subvendor>:<subdevice>][; ...]
3029					Specifies alignment and device to reassign
3030					aligned memory resources.
3031					If <order of align> is not specified,
3032					PAGE_SIZE is used as alignment.
3033					PCI-PCI bridge can be specified, if resource
3034					windows need to be expanded.
3035					To specify the alignment for several
3036					instances of a device, the PCI vendor,
3037					device, subvendor, and subdevice may be
3038					specified, e.g., 4096@pci:8086:9c22:103c:198f
3039			ecrc=		Enable/disable PCIe ECRC (transaction layer
3040					end-to-end CRC checking).
3041					bios: Use BIOS/firmware settings. This is the
3042					the default.
3043					off: Turn ECRC off
3044					on: Turn ECRC on.
3045			hpiosize=nn[KMG]	The fixed amount of bus space which is
3046					reserved for hotplug bridge's IO window.
3047					Default size is 256 bytes.
3048			hpmemsize=nn[KMG]	The fixed amount of bus space which is
3049					reserved for hotplug bridge's memory window.
3050					Default size is 2 megabytes.
3051			hpbussize=nn	The minimum amount of additional bus numbers
3052					reserved for buses below a hotplug bridge.
3053					Default is 1.
3054			realloc=	Enable/disable reallocating PCI bridge resources
3055					if allocations done by BIOS are too small to
3056					accommodate resources required by all child
3057					devices.
3058					off: Turn realloc off
3059					on: Turn realloc on
3060			realloc		same as realloc=on
3061			noari		do not use PCIe ARI.
3062			pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
3063					only look for one device below a PCIe downstream
3064					port.
3066		pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
3067				Management.
3068			off	Disable ASPM.
3069			force	Enable ASPM even on devices that claim not to support it.
3070				WARNING: Forcing ASPM on may cause system lockups.
3072		pcie_hp=	[PCIE] PCI Express Hotplug driver options:
3073			nomsi	Do not use MSI for PCI Express Native Hotplug (this
3074				makes all PCIe ports use INTx for hotplug services).
3076		pcie_ports=	[PCIE] PCIe ports handling:
3077			auto	Ask the BIOS whether or not to use native PCIe services
3078				associated with PCIe ports (PME, hot-plug, AER).  Use
3079				them only if that is allowed by the BIOS.
3080			native	Use native PCIe services associated with PCIe ports
3081				unconditionally.
3082			compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3083				ports driver.
3085		pcie_port_pm=	[PCIE] PCIe port power management handling:
3086			off	Disable power management of all PCIe ports
3087			force	Forcibly enable power management of all PCIe ports
3089		pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
3090			nomsi	Do not use MSI for native PCIe PME signaling (this makes
3091				all PCIe root ports use INTx for all services).
3093		pcmv=		[HW,PCMCIA] BadgePAD 4
3095		pd_ignore_unused
3096				[PM]
3097				Keep all power-domains already enabled by bootloader on,
3098				even if no driver has claimed them. This is useful
3099				for debug and development, but should not be
3100				needed on a platform with proper driver support.
3102		pd.		[PARIDE]
3103				See Documentation/blockdev/paride.txt.
3105		pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
3106				boot time.
3107				Format: { 0 | 1 }
3108				See arch/parisc/kernel/pdc_chassis.c
3110		percpu_alloc=	Select which percpu first chunk allocator to use.
3111				Currently supported values are "embed" and "page".
3112				Archs may support subset or none of the	selections.
3113				See comments in mm/percpu.c for details on each
3114				allocator.  This parameter is primarily	for debugging
3115				and performance comparison.
3117		pf.		[PARIDE]
3118				See Documentation/blockdev/paride.txt.
3120		pg.		[PARIDE]
3121				See Documentation/blockdev/paride.txt.
3123		pirq=		[SMP,APIC] Manual mp-table setup
3124				See Documentation/x86/i386/IO-APIC.txt.
3126		plip=		[PPT,NET] Parallel port network link
3127				Format: { parport<nr> | timid | 0 }
3128				See also Documentation/parport.txt.
3130		pmtmr=		[X86] Manual setup of pmtmr I/O Port.
3131				Override pmtimer IOPort with a hex value.
3132				e.g. pmtmr=0x508
3134		pnp.debug=1	[PNP]
3135				Enable PNP debug messages (depends on the
3136				CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
3137				via /sys/module/pnp/parameters/debug.  We always show
3138				current resource usage; turning this on also shows
3139				possible settings and some assignment information.
3141		pnpacpi=	[ACPI]
3142				{ off }
3144		pnpbios=	[ISAPNP]
3145				{ on | off | curr | res | no-curr | no-res }
3147		pnp_reserve_irq=
3148				[ISAPNP] Exclude IRQs for the autoconfiguration
3150		pnp_reserve_dma=
3151				[ISAPNP] Exclude DMAs for the autoconfiguration
3153		pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
3154				Ranges are in pairs (I/O port base and size).
3156		pnp_reserve_mem=
3157				[ISAPNP] Exclude memory regions for the
3158				autoconfiguration.
3159				Ranges are in pairs (memory base and size).
3161		ports=		[IP_VS_FTP] IPVS ftp helper module
3162				Default is 21.
3163				Up to 8 (IP_VS_APP_MAX_PORTS) ports
3164				may be specified.
3165				Format: <port>,<port>....
3167		ppc_strict_facility_enable
3168				[PPC] This option catches any kernel floating point,
3169				Altivec, VSX and SPE outside of regions specifically
3170				allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3171				There is some performance impact when enabling this.
3173		print-fatal-signals=
3174				[KNL] debug: print fatal signals
3176				If enabled, warn about various signal handling
3177				related application anomalies: too many signals,
3178				too many POSIX.1 timers, fatal signals causing a
3179				coredump - etc.
3181				If you hit the warning due to signal overflow,
3182				you might want to try "ulimit -i unlimited".
3184				default: off.
3186		printk.always_kmsg_dump=
3187				Trigger kmsg_dump for cases other than kernel oops or
3188				panics
3189				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
3190				default: disabled
3192		printk.devkmsg={on,off,ratelimit}
3193				Control writing to /dev/kmsg.
3194				on - unlimited logging to /dev/kmsg from userspace
3195				off - logging to /dev/kmsg disabled
3196				ratelimit - ratelimit the logging
3197				Default: ratelimit
3199		printk.time=	Show timing data prefixed to each printk message line
3200				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
3202		processor.max_cstate=	[HW,ACPI]
3203				Limit processor to maximum C-state
3204				max_cstate=9 overrides any DMI blacklist limit.
3206		processor.nocst	[HW,ACPI]
3207				Ignore the _CST method to determine C-states,
3208				instead using the legacy FADT method
3210		profile=	[KNL] Enable kernel profiling via /proc/profile
3211				Format: [schedule,]<number>
3212				Param: "schedule" - profile schedule points.
3213				Param: <number> - step/bucket size as a power of 2 for
3214					statistical time based profiling.
3215				Param: "sleep" - profile D-state sleeping (millisecs).
3216					Requires CONFIG_SCHEDSTATS
3217				Param: "kvm" - profile VM exits.
3219		prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
3220				before loading.
3221				See Documentation/blockdev/ramdisk.txt.
3223		psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
3224				probe for; one of (bare|imps|exps|lifebook|any).
3225		psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
3226				per second.
3227		psmouse.resetafter=	[HW,MOUSE]
3228				Try to reset the device after so many bad packets
3229				(0 = never).
3230		psmouse.resolution=
3231				[HW,MOUSE] Set desired mouse resolution, in dpi.
3232		psmouse.smartscroll=
3233				[HW,MOUSE] Controls Logitech smartscroll autorepeat.
3234				0 = disabled, 1 = enabled (default).
3236		pstore.backend=	Specify the name of the pstore backend to use
3238		pt.		[PARIDE]
3239				See Documentation/blockdev/paride.txt.
3241		pty.legacy_count=
3242				[KNL] Number of legacy pty's. Overwrites compiled-in
3243				default number.
3245		quiet		[KNL] Disable most log messages
3247		r128=		[HW,DRM]
3249		raid=		[HW,RAID]
3250				See Documentation/md.txt.
3252		ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
3253				See Documentation/blockdev/ramdisk.txt.
3255		rcu_nocbs=	[KNL]
3256				In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3257				the specified list of CPUs to be no-callback CPUs.
3258				Invocation of these CPUs' RCU callbacks will
3259				be offloaded to "rcuox/N" kthreads created for
3260				that purpose, where "x" is "b" for RCU-bh, "p"
3261				for RCU-preempt, and "s" for RCU-sched, and "N"
3262				is the CPU number.  This reduces OS jitter on the
3263				offloaded CPUs, which can be useful for HPC and
3264				real-time workloads.  It can also improve energy
3265				efficiency for asymmetric multiprocessors.
3267		rcu_nocb_poll	[KNL]
3268				Rather than requiring that offloaded CPUs
3269				(specified by rcu_nocbs= above) explicitly
3270				awaken the corresponding "rcuoN" kthreads,
3271				make these kthreads poll for callbacks.
3272				This improves the real-time response for the
3273				offloaded CPUs by relieving them of the need to
3274				wake up the corresponding kthread, but degrades
3275				energy efficiency by requiring that the kthreads
3276				periodically wake up to do the polling.
3278		rcutree.blimit=	[KNL]
3279				Set maximum number of finished RCU callbacks to
3280				process in one batch.
3282		rcutree.dump_tree=	[KNL]
3283				Dump the structure of the rcu_node combining tree
3284				out at early boot.  This is used for diagnostic
3285				purposes, to verify correct tree setup.
3287		rcutree.gp_cleanup_delay=	[KNL]
3288				Set the number of jiffies to delay each step of
3289				RCU grace-period cleanup.  This only has effect
3292		rcutree.gp_init_delay=	[KNL]
3293				Set the number of jiffies to delay each step of
3294				RCU grace-period initialization.  This only has
3296				is set.
3298		rcutree.gp_preinit_delay=	[KNL]
3299				Set the number of jiffies to delay each step of
3300				RCU grace-period pre-initialization, that is,
3301				the propagation of recent CPU-hotplug changes up
3302				the rcu_node combining tree.  This only has effect
3305		rcutree.rcu_fanout_exact= [KNL]
3306				Disable autobalancing of the rcu_node combining
3307				tree.  This is used by rcutorture, and might
3308				possibly be useful for architectures having high
3309				cache-to-cache transfer latencies.
3311		rcutree.rcu_fanout_leaf= [KNL]
3312				Change the number of CPUs assigned to each
3313				leaf rcu_node structure.  Useful for very
3314				large systems, which will choose the value 64,
3315				and for NUMA systems with large remote-access
3316				latencies, which will choose a value aligned
3317				with the appropriate hardware boundaries.
3319		rcutree.jiffies_till_sched_qs= [KNL]
3320				Set required age in jiffies for a
3321				given grace period before RCU starts
3322				soliciting quiescent-state help from
3323				rcu_note_context_switch().
3325		rcutree.jiffies_till_first_fqs= [KNL]
3326				Set delay from grace-period initialization to
3327				first attempt to force quiescent states.
3328				Units are jiffies, minimum value is zero,
3329				and maximum value is HZ.
3331		rcutree.jiffies_till_next_fqs= [KNL]
3332				Set delay between subsequent attempts to force
3333				quiescent states.  Units are jiffies, minimum
3334				value is one, and maximum value is HZ.
3336		rcutree.kthread_prio= 	 [KNL,BOOT]
3337				Set the SCHED_FIFO priority of the RCU per-CPU
3338				kthreads (rcuc/N). This value is also used for
3339				the priority of the RCU boost threads (rcub/N)
3340				and for the RCU grace-period kthreads (rcu_bh,
3341				rcu_preempt, and rcu_sched). If RCU_BOOST is
3342				set, valid values are 1-99 and the default is 1
3343				(the least-favored priority).  Otherwise, when
3344				RCU_BOOST is not set, valid values are 0-99 and
3345				the default is zero (non-realtime operation).
3347		rcutree.rcu_nocb_leader_stride= [KNL]
3348				Set the number of NOCB kthread groups, which
3349				defaults to the square root of the number of
3350				CPUs.  Larger numbers reduces the wakeup overhead
3351				on the per-CPU grace-period kthreads, but increases
3352				that same overhead on each group's leader.
3354		rcutree.qhimark= [KNL]
3355				Set threshold of queued RCU callbacks beyond which
3356				batch limiting is disabled.
3358		rcutree.qlowmark= [KNL]
3359				Set threshold of queued RCU callbacks below which
3360				batch limiting is re-enabled.
3362		rcutree.rcu_idle_gp_delay= [KNL]
3363				Set wakeup interval for idle CPUs that have
3364				RCU callbacks (RCU_FAST_NO_HZ=y).
3366		rcutree.rcu_idle_lazy_gp_delay= [KNL]
3367				Set wakeup interval for idle CPUs that have
3368				only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3369				Lazy RCU callbacks are those which RCU can
3370				prove do nothing more than free memory.
3372		rcuperf.gp_exp= [KNL]
3373				Measure performance of expedited synchronous
3374				grace-period primitives.
3376		rcuperf.holdoff= [KNL]
3377				Set test-start holdoff period.  The purpose of
3378				this parameter is to delay the start of the
3379				test until boot completes in order to avoid
3380				interference.
3382		rcuperf.nreaders= [KNL]
3383				Set number of RCU readers.  The value -1 selects
3384				N, where N is the number of CPUs.  A value
3385				"n" less than -1 selects N-n+1, where N is again
3386				the number of CPUs.  For example, -2 selects N
3387				(the number of CPUs), -3 selects N+1, and so on.
3388				A value of "n" less than or equal to -N selects
3389				a single reader.
3391		rcuperf.nwriters= [KNL]
3392				Set number of RCU writers.  The values operate
3393				the same as for rcuperf.nreaders.
3394				N, where N is the number of CPUs
3396		rcuperf.perf_runnable= [BOOT]
3397				Start rcuperf running at boot time.
3399		rcuperf.shutdown= [KNL]
3400				Shut the system down after performance tests
3401				complete.  This is useful for hands-off automated
3402				testing.
3404		rcuperf.perf_type= [KNL]
3405				Specify the RCU implementation to test.
3407		rcuperf.verbose= [KNL]
3408				Enable additional printk() statements.
3410		rcutorture.cbflood_inter_holdoff= [KNL]
3411				Set holdoff time (jiffies) between successive
3412				callback-flood tests.
3414		rcutorture.cbflood_intra_holdoff= [KNL]
3415				Set holdoff time (jiffies) between successive
3416				bursts of callbacks within a given callback-flood
3417				test.
3419		rcutorture.cbflood_n_burst= [KNL]
3420				Set the number of bursts making up a given
3421				callback-flood test.  Set this to zero to
3422				disable callback-flood testing.
3424		rcutorture.cbflood_n_per_burst= [KNL]
3425				Set the number of callbacks to be registered
3426				in a given burst of a callback-flood test.
3428		rcutorture.fqs_duration= [KNL]
3429				Set duration of force_quiescent_state bursts
3430				in microseconds.
3432		rcutorture.fqs_holdoff= [KNL]
3433				Set holdoff time within force_quiescent_state bursts
3434				in microseconds.
3436		rcutorture.fqs_stutter= [KNL]
3437				Set wait time between force_quiescent_state bursts
3438				in seconds.
3440		rcutorture.gp_cond= [KNL]
3441				Use conditional/asynchronous update-side
3442				primitives, if available.
3444		rcutorture.gp_exp= [KNL]
3445				Use expedited update-side primitives, if available.
3447		rcutorture.gp_normal= [KNL]
3448				Use normal (non-expedited) asynchronous
3449				update-side primitives, if available.
3451		rcutorture.gp_sync= [KNL]
3452				Use normal (non-expedited) synchronous
3453				update-side primitives, if available.  If all
3454				of rcutorture.gp_cond=, rcutorture.gp_exp=,
3455				rcutorture.gp_normal=, and rcutorture.gp_sync=
3456				are zero, rcutorture acts as if is interpreted
3457				they are all non-zero.
3459		rcutorture.n_barrier_cbs= [KNL]
3460				Set callbacks/threads for rcu_barrier() testing.
3462		rcutorture.nfakewriters= [KNL]
3463				Set number of concurrent RCU writers.  These just
3464				stress RCU, they don't participate in the actual
3465				test, hence the "fake".
3467		rcutorture.nreaders= [KNL]
3468				Set number of RCU readers.  The value -1 selects
3469				N-1, where N is the number of CPUs.  A value
3470				"n" less than -1 selects N-n-2, where N is again
3471				the number of CPUs.  For example, -2 selects N
3472				(the number of CPUs), -3 selects N+1, and so on.
3474		rcutorture.object_debug= [KNL]
3475				Enable debug-object double-call_rcu() testing.
3477		rcutorture.onoff_holdoff= [KNL]
3478				Set time (s) after boot for CPU-hotplug testing.
3480		rcutorture.onoff_interval= [KNL]
3481				Set time (s) between CPU-hotplug operations, or
3482				zero to disable CPU-hotplug testing.
3484		rcutorture.shuffle_interval= [KNL]
3485				Set task-shuffle interval (s).  Shuffling tasks
3486				allows some CPUs to go into dyntick-idle mode
3487				during the rcutorture test.
3489		rcutorture.shutdown_secs= [KNL]
3490				Set time (s) after boot system shutdown.  This
3491				is useful for hands-off automated testing.
3493		rcutorture.stall_cpu= [KNL]
3494				Duration of CPU stall (s) to test RCU CPU stall
3495				warnings, zero to disable.
3497		rcutorture.stall_cpu_holdoff= [KNL]
3498				Time to wait (s) after boot before inducing stall.
3500		rcutorture.stat_interval= [KNL]
3501				Time (s) between statistics printk()s.
3503		rcutorture.stutter= [KNL]
3504				Time (s) to stutter testing, for example, specifying
3505				five seconds causes the test to run for five seconds,
3506				wait for five seconds, and so on.  This tests RCU's
3507				ability to transition abruptly to and from idle.
3509		rcutorture.test_boost= [KNL]
3510				Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
3511				"Maybe" means test if the RCU implementation
3512				under test support RCU priority boosting.
3514		rcutorture.test_boost_duration= [KNL]
3515				Duration (s) of each individual boost test.
3517		rcutorture.test_boost_interval= [KNL]
3518				Interval (s) between each boost test.
3520		rcutorture.test_no_idle_hz= [KNL]
3521				Test RCU's dyntick-idle handling.  See also the
3522				rcutorture.shuffle_interval parameter.
3524		rcutorture.torture_runnable= [BOOT]
3525				Start rcutorture running at boot time.
3527		rcutorture.torture_type= [KNL]
3528				Specify the RCU implementation to test.
3530		rcutorture.verbose= [KNL]
3531				Enable additional printk() statements.
3533		rcupdate.rcu_cpu_stall_suppress= [KNL]
3534				Suppress RCU CPU stall warning messages.
3536		rcupdate.rcu_cpu_stall_timeout= [KNL]
3537				Set timeout for RCU CPU stall warning messages.
3539		rcupdate.rcu_expedited= [KNL]
3540				Use expedited grace-period primitives, for
3541				example, synchronize_rcu_expedited() instead
3542				of synchronize_rcu().  This reduces latency,
3543				but can increase CPU utilization, degrade
3544				real-time latency, and degrade energy efficiency.
3545				No effect on CONFIG_TINY_RCU kernels.
3547		rcupdate.rcu_normal= [KNL]
3548				Use only normal grace-period primitives,
3549				for example, synchronize_rcu() instead of
3550				synchronize_rcu_expedited().  This improves
3551				real-time latency, CPU utilization, and
3552				energy efficiency, but can expose users to
3553				increased grace-period latency.  This parameter
3554				overrides rcupdate.rcu_expedited.  No effect on
3555				CONFIG_TINY_RCU kernels.
3557		rcupdate.rcu_normal_after_boot= [KNL]
3558				Once boot has completed (that is, after
3559				rcu_end_inkernel_boot() has been invoked), use
3560				only normal grace-period primitives.  No effect
3561				on CONFIG_TINY_RCU kernels.
3563		rcupdate.rcu_task_stall_timeout= [KNL]
3564				Set timeout in jiffies for RCU task stall warning
3565				messages.  Disable with a value less than or equal
3566				to zero.
3568		rcupdate.rcu_self_test= [KNL]
3569				Run the RCU early boot self tests
3571		rcupdate.rcu_self_test_bh= [KNL]
3572				Run the RCU bh early boot self tests
3574		rcupdate.rcu_self_test_sched= [KNL]
3575				Run the RCU sched early boot self tests
3577		rdinit=		[KNL]
3578				Format: <full_path>
3579				Run specified binary instead of /init from the ramdisk,
3580				used for early userspace startup. See initrd.
3582		reboot=		[KNL]
3583				Format (x86 or x86_64):
3584					[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3585					[[,]s[mp]#### \
3586					[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3587					[[,]f[orce]
3588				Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3589				      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3590				      reboot_force is either force or not specified,
3591				      reboot_cpu is s[mp]#### with #### being the processor
3592						to be used for rebooting.
3594		relax_domain_level=
3595				[KNL, SMP] Set scheduler's default relax_domain_level.
3596				See Documentation/cgroup-v1/cpusets.txt.
3598		relative_sleep_states=
3599				[SUSPEND] Use sleep state labeling where the deepest
3600				state available other than hibernation is always "mem".
3601				Format: { "0" | "1" }
3602				0 -- Traditional sleep state labels.
3603				1 -- Relative sleep state labels.
3605		reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
3607		reservetop=	[X86-32]
3608				Format: nn[KMG]
3609				Reserves a hole at the top of the kernel virtual
3610				address space.
3612		reservelow=	[X86]
3613				Format: nn[K]
3614				Set the amount of memory to reserve for BIOS at
3615				the bottom of the address space.
3617		reset_devices	[KNL] Force drivers to reset the underlying device
3618				during initialization.
3620		resume=		[SWSUSP]
3621				Specify the partition device for software suspend
3622				Format:
3623				{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3625		resume_offset=	[SWSUSP]
3626				Specify the offset from the beginning of the partition
3627				given by "resume=" at which the swap header is located,
3628				in <PAGE_SIZE> units (needed only for swap files).
3629				See  Documentation/power/swsusp-and-swap-files.txt
3631		resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
3632				read the resume files
3634		resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
3635				Useful for devices that are detected asynchronously
3636				(e.g. USB and MMC devices).
3638		hibernate=	[HIBERNATION]
3639			noresume	Don't check if there's a hibernation image
3640					present during boot.
3641			nocompress	Don't compress/decompress hibernation images.
3642			no		Disable hibernation and resume.
3643			protect_image	Turn on image protection during restoration
3644					(that will set all pages holding image data
3645					during restoration read-only).
3647		retain_initrd	[RAM] Keep initrd memory after extraction
3649		rfkill.default_state=
3650			0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
3651				etc. communication is blocked by default.
3652			1	Unblocked.
3654		rfkill.master_switch_mode=
3655			0	The "airplane mode" button does nothing.
3656			1	The "airplane mode" button toggles between everything
3657				blocked and the previous configuration.
3658			2	The "airplane mode" button toggles between everything
3659				blocked and everything unblocked.
3661		rhash_entries=	[KNL,NET]
3662				Set number of hash buckets for route cache
3664		ro		[KNL] Mount root device read-only on boot
3666		rodata=		[KNL]
3667			on	Mark read-only kernel memory as read-only (default).
3668			off	Leave read-only kernel memory writable for debugging.
3670		rockchip.usb_uart
3671				Enable the uart passthrough on the designated usb port
3672				on Rockchip SoCs. When active, the signals of the
3673				debug-uart get routed to the D+ and D- pins of the usb
3674				port and the regular usb controller gets disabled.
3676		root=		[KNL] Root filesystem
3677				See name_to_dev_t comment in init/do_mounts.c.
3679		rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
3680				mount the root filesystem
3682		rootflags=	[KNL] Set root filesystem mount option string
3684		rootfstype=	[KNL] Set root filesystem type
3686		rootwait	[KNL] Wait (indefinitely) for root device to show up.
3687				Useful for devices that are detected asynchronously
3688				(e.g. USB and MMC devices).
3690		rproc_mem=nn[KMG][@address]
3691				[KNL,ARM,CMA] Remoteproc physical memory block.
3692				Memory area to be used by remote processor image,
3693				managed by CMA.
3695		rw		[KNL] Mount root device read-write on boot
3697		S		[KNL] Run init in single mode
3699		s390_iommu=	[HW,S390]
3700				Set s390 IOTLB flushing mode
3701			strict
3702				With strict flushing every unmap operation will result in
3703				an IOTLB flush. Default is lazy flushing before reuse,
3704				which is faster.
3706		sa1100ir	[NET]
3707				See drivers/net/irda/sa1100_ir.c.
3709		sbni=		[NET] Granch SBNI12 leased line adapter
3711		sched_debug	[KNL] Enables verbose scheduler debug messages.
3713		schedstats=	[KNL,X86] Enable or disable scheduled statistics.
3714				Allowed values are enable and disable. This feature
3715				incurs a small amount of overhead in the scheduler
3716				but is useful for debugging and performance tuning.
3718		skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
3719				xtime_lock contention on larger systems, and/or RCU lock
3720				contention on all systems with CONFIG_MAXSMP set.
3721				Format: { "0" | "1" }
3722				0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3723				1 -- enable.
3724				Note: increases power consumption, thus should only be
3725				enabled if running jitter sensitive (HPC/RT) workloads.
3727		security=	[SECURITY] Choose a security module to enable at boot.
3728				If this boot parameter is not specified, only the first
3729				security module asking for security registration will be
3730				loaded. An invalid security module name will be treated
3731				as if no module has been chosen.
3733		selinux=	[SELINUX] Disable or enable SELinux at boot time.
3734				Format: { "0" | "1" }
3735				See security/selinux/Kconfig help text.
3736				0 -- disable.
3737				1 -- enable.
3738				Default value is set via kernel config option.
3739				If enabled at boot time, /selinux/disable can be used
3740				later to disable prior to initial policy load.
3742		apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
3743				Format: { "0" | "1" }
3744				See security/apparmor/Kconfig help text
3745				0 -- disable.
3746				1 -- enable.
3747				Default value is set via kernel config option.
3749		serialnumber	[BUGS=X86-32]
3751		shapers=	[NET]
3752				Maximal number of shapers.
3754		show_msr=	[x86] show boot-time MSR settings
3755				Format: { <integer> }
3756				Show boot-time (BIOS-initialized) MSR settings.
3757				The parameter means the number of CPUs to show,
3758				for example 1 means boot CPU only.
3760		simeth=		[IA-64]
3761		simscsi=
3763		slram=		[HW,MTD]
3765		slab_nomerge	[MM]
3766				Disable merging of slabs with similar size. May be
3767				necessary if there is some reason to distinguish
3768				allocs to different slabs. Debug options disable
3769				merging on their own.
3770				For more information see Documentation/vm/slub.txt.
3772		slab_max_order=	[MM, SLAB]
3773				Determines the maximum allowed order for slabs.
3774				A high setting may cause OOMs due to memory
3775				fragmentation.  Defaults to 1 for systems with
3776				more than 32MB of RAM, 0 otherwise.
3778		slub_debug[=options[,slabs]]	[MM, SLUB]
3779				Enabling slub_debug allows one to determine the
3780				culprit if slab objects become corrupted. Enabling
3781				slub_debug can create guard zones around objects and
3782				may poison objects when not in use. Also tracks the
3783				last alloc / free. For more information see
3784				Documentation/vm/slub.txt.
3786		slub_max_order= [MM, SLUB]
3787				Determines the maximum allowed order for slabs.
3788				A high setting may cause OOMs due to memory
3789				fragmentation. For more information see
3790				Documentation/vm/slub.txt.
3792		slub_min_objects=	[MM, SLUB]
3793				The minimum number of objects per slab. SLUB will
3794				increase the slab order up to slub_max_order to
3795				generate a sufficiently large slab able to contain
3796				the number of objects indicated. The higher the number
3797				of objects the smaller the overhead of tracking slabs
3798				and the less frequently locks need to be acquired.
3799				For more information see Documentation/vm/slub.txt.
3801		slub_min_order=	[MM, SLUB]
3802				Determines the minimum page order for slabs. Must be
3803				lower than slub_max_order.
3804				For more information see Documentation/vm/slub.txt.
3806		slub_nomerge	[MM, SLUB]
3807				Same with slab_nomerge. This is supported for legacy.
3808				See slab_nomerge for more information.
3810		smart2=		[HW]
3811				Format: <io1>[,<io2>[,...,<io8>]]
3813		smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
3814		smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
3815		smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
3816		smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
3817		smsc-ircc2.ircc_irq=	[HW] IRQ line
3818		smsc-ircc2.ircc_dma=	[HW] DMA channel
3819		smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3820					0: Toshiba Satellite 1800 (GP data pin select)
3821					1: Fast pin select (default)
3822					2: ATC IRMode
3824		smt		[KNL,S390] Set the maximum number of threads (logical
3825				CPUs) to use per physical CPU on systems capable of
3826				symmetric multithreading (SMT). Will be capped to the
3827				actual hardware limit.
3828				Format: <integer>
3829				Default: -1 (no limit)
3831		softlockup_panic=
3832				[KNL] Should the soft-lockup detector generate panics.
3833				Format: <integer>
3835		softlockup_all_cpu_backtrace=
3836				[KNL] Should the soft-lockup detector generate
3837				backtraces on all cpus.
3838				Format: <integer>
3840		sonypi.*=	[HW] Sony Programmable I/O Control Device driver
3841				See Documentation/laptops/sonypi.txt
3843		spia_io_base=	[HW,MTD]
3844		spia_fio_base=
3845		spia_pedr=
3846		spia_peddr=
3848		stacktrace	[FTRACE]
3849				Enabled the stack tracer on boot up.
3851		stacktrace_filter=[function-list]
3852				[FTRACE] Limit the functions that the stack tracer
3853				will trace at boot up. function-list is a comma separated
3854				list of functions. This list can be changed at run
3855				time by the stack_trace_filter file in the debugfs
3856				tracing directory. Note, this enables stack tracing
3857				and the stacktrace above is not needed.
3859		sti=		[PARISC,HW]
3860				Format: <num>
3861				Set the STI (builtin display/keyboard on the HP-PARISC
3862				machines) console (graphic card) which should be used
3863				as the initial boot-console.
3864				See also comment in drivers/video/console/sticore.c.
3866		sti_font=	[HW]
3867				See comment in drivers/video/console/sticore.c.
3869		stifb=		[HW]
3870				Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3872		sunrpc.min_resvport=
3873		sunrpc.max_resvport=
3874				[NFS,SUNRPC]
3875				SunRPC servers often require that client requests
3876				originate from a privileged port (i.e. a port in the
3877				range 0 < portnr < 1024).
3878				An administrator who wishes to reserve some of these
3879				ports for other uses may adjust the range that the
3880				kernel's sunrpc client considers to be privileged
3881				using these two parameters to set the minimum and
3882				maximum port values.
3884		sunrpc.svc_rpc_per_connection_limit=
3885				[NFS,SUNRPC]
3886				Limit the number of requests that the server will
3887				process in parallel from a single connection.
3888				The default value is 0 (no limit).
3890		sunrpc.pool_mode=
3891				[NFS]
3892				Control how the NFS server code allocates CPUs to
3893				service thread pools.  Depending on how many NICs
3894				you have and where their interrupts are bound, this
3895				option will affect which CPUs will do NFS serving.
3896				Note: this parameter cannot be changed while the
3897				NFS server is running.
3899				auto	    the server chooses an appropriate mode
3900					    automatically using heuristics
3901				global	    a single global pool contains all CPUs
3902				percpu	    one pool for each CPU
3903				pernode	    one pool for each NUMA node (equivalent
3904					    to global on non-NUMA machines)
3906		sunrpc.tcp_slot_table_entries=
3907		sunrpc.udp_slot_table_entries=
3908				[NFS,SUNRPC]
3909				Sets the upper limit on the number of simultaneous
3910				RPC calls that can be sent from the client to a
3911				server. Increasing these values may allow you to
3912				improve throughput, but will also increase the
3913				amount of memory reserved for use by the client.
3915		suspend.pm_test_delay=
3916				[SUSPEND]
3917				Sets the number of seconds to remain in a suspend test
3918				mode before resuming the system (see
3919				/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3920				is set. Default value is 5.
3922		swapaccount=[0|1]
3923				[KNL] Enable accounting of swap in memory resource
3924				controller if no parameter or 1 is given or disable
3925				it if 0 is given (See Documentation/cgroup-v1/memory.txt)
3927		swiotlb=	[ARM,IA-64,PPC,MIPS,X86]
3928				Format: { <int> | force }
3929				<int> -- Number of I/O TLB slabs
3930				force -- force using of bounce buffers even if they
3931				         wouldn't be automatically used by the kernel
3933		switches=	[HW,M68k]
3935		sysfs.deprecated=0|1 [KNL]
3936				Enable/disable old style sysfs layout for old udev
3937				on older distributions. When this option is enabled
3938				very new udev will not work anymore. When this option
3939				is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3940				in older udev will not work anymore.
3941				Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3942				the kernel configuration.
3944		sysrq_always_enabled
3945				[KNL]
3946				Ignore sysrq setting - this boot parameter will
3947				neutralize any effect of /proc/sys/kernel/sysrq.
3948				Useful for debugging.
3950		tcpmhash_entries= [KNL,NET]
3951				Set the number of tcp_metrics_hash slots.
3952				Default value is 8192 or 16384 depending on total
3953				ram pages. This is used to specify the TCP metrics
3954				cache size. See Documentation/networking/ip-sysctl.txt
3955				"tcp_no_metrics_save" section for more details.
3957		tdfx=		[HW,DRM]
3959		test_suspend=	[SUSPEND][,N]
3960				Specify "mem" (for Suspend-to-RAM) or "standby" (for
3961				standby suspend) or "freeze" (for suspend type freeze)
3962				as the system sleep state during system startup with
3963				the optional capability to repeat N number of times.
3964				The system is woken from this state using a
3965				wakeup-capable RTC alarm.
3967		thash_entries=	[KNL,NET]
3968				Set number of hash buckets for TCP connection
3970		thermal.act=	[HW,ACPI]
3971				-1: disable all active trip points in all thermal zones
3972				<degrees C>: override all lowest active trip points
3974		thermal.crt=	[HW,ACPI]
3975				-1: disable all critical trip points in all thermal zones
3976				<degrees C>: override all critical trip points
3978		thermal.nocrt=	[HW,ACPI]
3979				Set to disable actions on ACPI thermal zone
3980				critical and hot trip points.
3982		thermal.off=	[HW,ACPI]
3983				1: disable ACPI thermal control
3985		thermal.psv=	[HW,ACPI]
3986				-1: disable all passive trip points
3987				<degrees C>: override all passive trip points to this
3988				value
3990		thermal.tzp=	[HW,ACPI]
3991				Specify global default ACPI thermal zone polling rate
3992				<deci-seconds>: poll all this frequency
3993				0: no polling (default)
3995		threadirqs	[KNL]
3996				Force threading of all interrupt handlers except those
3997				marked explicitly IRQF_NO_THREAD.
3999		tmem		[KNL,XEN]
4000				Enable the Transcendent memory driver if built-in.
4002		tmem.cleancache=0|1 [KNL, XEN]
4003				Default is on (1). Disable the usage of the cleancache
4004				API to send anonymous pages to the hypervisor.
4006		tmem.frontswap=0|1 [KNL, XEN]
4007				Default is on (1). Disable the usage of the frontswap
4008				API to send swap pages to the hypervisor. If disabled
4009				the selfballooning and selfshrinking are force disabled.
4011		tmem.selfballooning=0|1 [KNL, XEN]
4012				Default is on (1). Disable the driving of swap pages
4013				to the hypervisor.
4015		tmem.selfshrinking=0|1 [KNL, XEN]
4016				Default is on (1). Partial swapoff that immediately
4017				transfers pages from Xen hypervisor back to the
4018				kernel based on different criteria.
4020		topology=	[S390]
4021				Format: {off | on}
4022				Specify if the kernel should make use of the cpu
4023				topology information if the hardware supports this.
4024				The scheduler will make use of this information and
4025				e.g. base its process migration decisions on it.
4026				Default is on.
4028		topology_updates= [KNL, PPC, NUMA]
4029				Format: {off}
4030				Specify if the kernel should ignore (off)
4031				topology updates sent by the hypervisor to this
4032				LPAR.
4034		tp720=		[HW,PS2]
4036		tpm_suspend_pcr=[HW,TPM]
4037				Format: integer pcr id
4038				Specify that at suspend time, the tpm driver
4039				should extend the specified pcr with zeros,
4040				as a workaround for some chips which fail to
4041				flush the last written pcr on TPM_SaveState.
4042				This will guarantee that all the other pcrs
4043				are saved.
4045		trace_buf_size=nn[KMG]
4046				[FTRACE] will set tracing buffer size on each cpu.
4048		trace_event=[event-list]
4049				[FTRACE] Set and start specified trace events in order
4050				to facilitate early boot debugging. The event-list is a
4051				comma separated list of trace events to enable. See
4052				also Documentation/trace/events.txt
4054		trace_options=[option-list]
4055				[FTRACE] Enable or disable tracer options at boot.
4056				The option-list is a comma delimited list of options
4057				that can be enabled or disabled just as if you were
4058				to echo the option name into
4060				    /sys/kernel/debug/tracing/trace_options
4062				For example, to enable stacktrace option (to dump the
4063				stack trace of each event), add to the command line:
4065				      trace_options=stacktrace
4067				See also Documentation/trace/ftrace.txt "trace options"
4068				section.
4070		tp_printk[FTRACE]
4071				Have the tracepoints sent to printk as well as the
4072				tracing ring buffer. This is useful for early boot up
4073				where the system hangs or reboots and does not give the
4074				option for reading the tracing buffer or performing a
4075				ftrace_dump_on_oops.
4077				To turn off having tracepoints sent to printk,
4078				 echo 0 > /proc/sys/kernel/tracepoint_printk
4079				Note, echoing 1 into this file without the
4080				tracepoint_printk kernel cmdline option has no effect.
4082				** CAUTION **
4084				Having tracepoints sent to printk() and activating high
4085				frequency tracepoints such as irq or sched, can cause
4086				the system to live lock.
4088		traceoff_on_warning
4089				[FTRACE] enable this option to disable tracing when a
4090				warning is hit. This turns off "tracing_on". Tracing can
4091				be enabled again by echoing '1' into the "tracing_on"
4092				file located in /sys/kernel/debug/tracing/
4094				This option is useful, as it disables the trace before
4095				the WARNING dump is called, which prevents the trace to
4096				be filled with content caused by the warning output.
4098				This option can also be set at run time via the sysctl
4099				option:  kernel/traceoff_on_warning
4101		transparent_hugepage=
4102				[KNL]
4103				Format: [always|madvise|never]
4104				Can be used to control the default behavior of the system
4105				with respect to transparent hugepages.
4106				See Documentation/vm/transhuge.txt for more details.
4108		tsc=		Disable clocksource stability checks for TSC.
4109				Format: <string>
4110				[x86] reliable: mark tsc clocksource as reliable, this
4111				disables clocksource verification at runtime, as well
4112				as the stability checks done at bootup.	Used to enable
4113				high-resolution timer mode on older hardware, and in
4114				virtualized environment.
4115				[x86] noirqtime: Do not use TSC to do irq accounting.
4116				Used to run time disable IRQ_TIME_ACCOUNTING on any
4117				platforms where RDTSC is slow and this accounting
4118				can add overhead.
4120		turbografx.map[2|3]=	[HW,JOY]
4121				TurboGraFX parallel port interface
4122				Format:
4123				<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4124				See also Documentation/input/joystick-parport.txt
4126		udbg-immortal	[PPC] When debugging early kernel crashes that
4127				happen after console_init() and before a proper 
4128				console driver takes over, this boot options might
4129				help "seeing" what's going on.
4131		uhash_entries=	[KNL,NET]
4132				Set number of hash buckets for UDP/UDP-Lite connections
4134		uhci-hcd.ignore_oc=
4135				[USB] Ignore overcurrent events (default N).
4136				Some badly-designed motherboards generate lots of
4137				bogus events, for ports that aren't wired to
4138				anything.  Set this parameter to avoid log spamming.
4139				Note that genuine overcurrent events won't be
4140				reported either.
4142		unknown_nmi_panic
4143				[X86] Cause panic on unknown NMI.
4145		usbcore.authorized_default=
4146				[USB] Default USB device authorization:
4147				(default -1 = authorized except for wireless USB,
4148				0 = not authorized, 1 = authorized)
4150		usbcore.autosuspend=
4151				[USB] The autosuspend time delay (in seconds) used
4152				for newly-detected USB devices (default 2).  This
4153				is the time required before an idle device will be
4154				autosuspended.  Devices for which the delay is set
4155				to a negative value won't be autosuspended at all.
4157		usbcore.usbfs_snoop=
4158				[USB] Set to log all usbfs traffic (default 0 = off).
4160		usbcore.usbfs_snoop_max=
4161				[USB] Maximum number of bytes to snoop in each URB
4162				(default = 65536).
4164		usbcore.blinkenlights=
4165				[USB] Set to cycle leds on hubs (default 0 = off).
4167		usbcore.old_scheme_first=
4168				[USB] Start with the old device initialization
4169				scheme (default 0 = off).
4171		usbcore.usbfs_memory_mb=
4172				[USB] Memory limit (in MB) for buffers allocated by
4173				usbfs (default = 16, 0 = max = 2047).
4175		usbcore.use_both_schemes=
4176				[USB] Try the other device initialization scheme
4177				if the first one fails (default 1 = enabled).
4179		usbcore.initial_descriptor_timeout=
4180				[USB] Specifies timeout for the initial 64-byte
4181	                        USB_REQ_GET_DESCRIPTOR request in milliseconds
4182				(default 5000 = 5.0 seconds).
4184		usbcore.nousb	[USB] Disable the USB subsystem
4186		usbhid.mousepoll=
4187				[USBHID] The interval which mice are to be polled at.
4189		usb-storage.delay_use=
4190				[UMS] The delay in seconds before a new device is
4191				scanned for Logical Units (default 1).
4193		usb-storage.quirks=
4194				[UMS] A list of quirks entries to supplement or
4195				override the built-in unusual_devs list.  List
4196				entries are separated by commas.  Each entry has
4197				the form VID:PID:Flags where VID and PID are Vendor
4198				and Product ID values (4-digit hex numbers) and
4199				Flags is a set of characters, each corresponding
4200				to a common usb-storage quirk flag as follows:
4201					a = SANE_SENSE (collect more than 18 bytes
4202						of sense data);
4203					b = BAD_SENSE (don't collect more than 18
4204						bytes of sense data);
4205					c = FIX_CAPACITY (decrease the reported
4206						device capacity by one sector);
4207					d = NO_READ_DISC_INFO (don't use
4208						READ_DISC_INFO command);
4209					e = NO_READ_CAPACITY_16 (don't use
4210						READ_CAPACITY_16 command);
4211					f = NO_REPORT_OPCODES (don't use report opcodes
4212						command, uas only);
4213					g = MAX_SECTORS_240 (don't transfer more than
4214						240 sectors at a time, uas only);
4215					h = CAPACITY_HEURISTICS (decrease the
4216						reported device capacity by one
4217						sector if the number is odd);
4218					i = IGNORE_DEVICE (don't bind to this
4219						device);
4220					j = NO_REPORT_LUNS (don't use report luns
4221						command, uas only);
4222					l = NOT_LOCKABLE (don't try to lock and
4223						unlock ejectable media);
4224					m = MAX_SECTORS_64 (don't transfer more
4225						than 64 sectors = 32 KB at a time);
4226					n = INITIAL_READ10 (force a retry of the
4227						initial READ(10) command);
4228					o = CAPACITY_OK (accept the capacity
4229						reported by the device);
4230					p = WRITE_CACHE (the device cache is ON
4231						by default);
4232					r = IGNORE_RESIDUE (the device reports
4233						bogus residue values);
4234					s = SINGLE_LUN (the device has only one
4235						Logical Unit);
4236					t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4237						commands, uas only);
4238					u = IGNORE_UAS (don't bind to the uas driver);
4239					w = NO_WP_DETECT (don't test whether the
4240						medium is write-protected).
4241				Example: quirks=0419:aaf5:rl,0421:0433:rc
4243		user_debug=	[KNL,ARM]
4244				Format: <int>
4245				See arch/arm/Kconfig.debug help text.
4246					 1 - undefined instruction events
4247					 2 - system calls
4248					 4 - invalid data aborts
4249					 8 - SIGSEGV faults
4250					16 - SIGBUS faults
4251				Example: user_debug=31
4253		userpte=
4254				[X86] Flags controlling user PTE allocations.
4256					nohigh = do not allocate PTE pages in
4257						HIGHMEM regardless of setting
4258						of CONFIG_HIGHPTE.
4260		vdso=		[X86,SH]
4261				On X86_32, this is an alias for vdso32=.  Otherwise:
4263				vdso=1: enable VDSO (the default)
4264				vdso=0: disable VDSO mapping
4266		vdso32=		[X86] Control the 32-bit vDSO
4267				vdso32=1: enable 32-bit VDSO
4268				vdso32=0 or vdso32=2: disable 32-bit VDSO
4270				See the help text for CONFIG_COMPAT_VDSO for more
4271				details.  If CONFIG_COMPAT_VDSO is set, the default is
4272				vdso32=0; otherwise, the default is vdso32=1.
4274				For compatibility with older kernels, vdso32=2 is an
4275				alias for vdso32=0.
4277				Try vdso32=0 if you encounter an error that says:
4278				dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4280		vector=		[IA-64,SMP]
4281				vector=percpu: enable percpu vector domain
4283		video=		[FB] Frame buffer configuration
4284				See Documentation/fb/modedb.txt.
4286		video.brightness_switch_enabled= [0,1]
4287				If set to 1, on receiving an ACPI notify event
4288				generated by hotkey, video driver will adjust brightness
4289				level and then send out the event to user space through
4290				the allocated input device; If set to 0, video driver
4291				will only send out the event without touching backlight
4292				brightness level.
4293				default: 1
4295		virtio_mmio.device=
4296				[VMMIO] Memory mapped virtio (platform) device.
4298					<size>@<baseaddr>:<irq>[:<id>]
4299				where:
4300					<size>     := size (can use standard suffixes
4301							like K, M and G)
4302					<baseaddr> := physical base address
4303					<irq>      := interrupt number (as passed to
4304							request_irq())
4305					<id>       := (optional) platform device id
4306				example:
4307					virtio_mmio.device=1K@0x100b0000:48:7
4309				Can be used multiple times for multiple devices.
4311		vga=		[BOOT,X86-32] Select a particular video mode
4312				See Documentation/x86/boot.txt and
4313				Documentation/svga.txt.
4314				Use vga=ask for menu.
4315				This is actually a boot loader parameter; the value is
4316				passed to the kernel using a special protocol.
4318		vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
4319				size of <nn>. This can be used to increase the
4320				minimum size (128MB on x86). It can also be used to
4321				decrease the size and leave more room for directly
4322				mapped kernel RAM.
4324		vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
4325				Format: <command>
4327		vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
4328				Format: <command>
4330		vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
4331				Format: <command>
4333		vsyscall=	[X86-64]
4334				Controls the behavior of vsyscalls (i.e. calls to
4335				fixed addresses of 0xffffffffff600x00 from legacy
4336				code).  Most statically-linked binaries and older
4337				versions of glibc use these calls.  Because these
4338				functions are at fixed addresses, they make nice
4339				targets for exploits that can control RIP.
4341				emulate     [default] Vsyscalls turn into traps and are
4342				            emulated reasonably safely.
4344				native      Vsyscalls are native syscall instructions.
4345				            This is a little bit faster than trapping
4346				            and makes a few dynamic recompilers work
4347				            better than they would in emulation mode.
4348				            It also makes exploits much easier to write.
4350				none        Vsyscalls don't work at all.  This makes
4351				            them quite hard to use for exploits but
4352				            might break your system.
4354		vt.color=	[VT] Default text color.
4355				Format: 0xYX, X = foreground, Y = background.
4356				Default: 0x07 = light gray on black.
4358		vt.cur_default=	[VT] Default cursor shape.
4359				Format: 0xCCBBAA, where AA, BB, and CC are the same as
4360				the parameters of the <Esc>[?A;B;Cc escape sequence;
4361				see VGA-softcursor.txt. Default: 2 = underline.
4363		vt.default_blu=	[VT]
4364				Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4365				Change the default blue palette of the console.
4366				This is a 16-member array composed of values
4367				ranging from 0-255.
4369		vt.default_grn=	[VT]
4370				Format: <green0>,<green1>,<green2>,...,<green15>
4371				Change the default green palette of the console.
4372				This is a 16-member array composed of values
4373				ranging from 0-255.
4375		vt.default_red=	[VT]
4376				Format: <red0>,<red1>,<red2>,...,<red15>
4377				Change the default red palette of the console.
4378				This is a 16-member array composed of values
4379				ranging from 0-255.
4381		vt.default_utf8=
4382				[VT]
4383				Format=<0|1>
4384				Set system-wide default UTF-8 mode for all tty's.
4385				Default is 1, i.e. UTF-8 mode is enabled for all
4386				newly opened terminals.
4388		vt.global_cursor_default=
4389				[VT]
4390				Format=<-1|0|1>
4391				Set system-wide default for whether a cursor
4392				is shown on new VTs. Default is -1,
4393				i.e. cursors will be created by default unless
4394				overridden by individual drivers. 0 will hide
4395				cursors, 1 will display them.
4397		vt.italic=	[VT] Default color for italic text; 0-15.
4398				Default: 2 = green.
4400		vt.underline=	[VT] Default color for underlined text; 0-15.
4401				Default: 3 = cyan.
4403		watchdog timers	[HW,WDT] For information on watchdog timers,
4404				see Documentation/watchdog/watchdog-parameters.txt
4405				or other driver-specific files in the
4406				Documentation/watchdog/ directory.
4408		workqueue.watchdog_thresh=
4409				If CONFIG_WQ_WATCHDOG is configured, workqueue can
4410				warn stall conditions and dump internal state to
4411				help debugging.  0 disables workqueue stall
4412				detection; otherwise, it's the stall threshold
4413				duration in seconds.  The default value is 30 and
4414				it can be updated at runtime by writing to the
4415				corresponding sysfs file.
4417		workqueue.disable_numa
4418				By default, all work items queued to unbound
4419				workqueues are affine to the NUMA nodes they're
4420				issued on, which results in better behavior in
4421				general.  If NUMA affinity needs to be disabled for
4422				whatever reason, this option can be used.  Note
4423				that this also can be controlled per-workqueue for
4424				workqueues visible under /sys/bus/workqueue/.
4426		workqueue.power_efficient
4427				Per-cpu workqueues are generally preferred because
4428				they show better performance thanks to cache
4429				locality; unfortunately, per-cpu workqueues tend to
4430				be more power hungry than unbound workqueues.
4432				Enabling this makes the per-cpu workqueues which
4433				were observed to contribute significantly to power
4434				consumption unbound, leading to measurably lower
4435				power usage at the cost of small performance
4436				overhead.
4438				The default value of this parameter is determined by
4439				the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4441		workqueue.debug_force_rr_cpu
4442				Workqueue used to implicitly guarantee that work
4443				items queued without explicit CPU specified are put
4444				on the local CPU.  This guarantee is no longer true
4445				and while local CPU is still preferred work items
4446				may be put on foreign CPUs.  This debug option
4447				forces round-robin CPU selection to flush out
4448				usages which depend on the now broken guarantee.
4449				When enabled, memory and cache locality will be
4450				impacted.
4452		x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
4453				default x2apic cluster mode on platforms
4454				supporting x2apic.
4456		x86_intel_mid_timer= [X86-32,APBT]
4457				Choose timer option for x86 Intel MID platform.
4458				Two valid options are apbt timer only and lapic timer
4459				plus one apbt timer for broadcast timer.
4460				x86_intel_mid_timer=apbt_only | lapic_and_apbt
4462		xen_512gb_limit		[KNL,X86-64,XEN]
4463				Restricts the kernel running paravirtualized under Xen
4464				to use only up to 512 GB of RAM. The reason to do so is
4465				crash analysis tools and Xen tools for doing domain
4466				save/restore/migration must be enabled to handle larger
4467				domains.
4469		xen_emul_unplug=		[HW,X86,XEN]
4470				Unplug Xen emulated devices
4471				Format: [unplug0,][unplug1]
4472				ide-disks -- unplug primary master IDE devices
4473				aux-ide-disks -- unplug non-primary-master IDE devices
4474				nics -- unplug network devices
4475				all -- unplug all emulated devices (NICs and IDE disks)
4476				unnecessary -- unplugging emulated devices is
4477					unnecessary even if the host did not respond to
4478					the unplug protocol
4479				never -- do not unplug even if version check succeeds
4481		xen_nopvspin	[X86,XEN]
4482				Disables the ticketlock slowpath using Xen PV
4483				optimizations.
4485		xen_nopv	[X86]
4486				Disables the PV optimizations forcing the HVM guest to
4487				run as generic HVM guest with no PV drivers.
4489		xirc2ps_cs=	[NET,PCMCIA]
4490				Format:
4491				<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4493	______________________________________________________________________
4495	TODO:
4497		Add more DRM drivers.
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