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Based on kernel version 3.16. Page generated on 2014-08-06 21:40 EST.

1	                          Kernel Parameters
2	                          ~~~~~~~~~~~~~~~~~
3	
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.
9	
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.
15	
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.:
18	
19		(kernel command line) usbcore.blinkenlights=1
20		(modprobe command line) modprobe usbcore blinkenlights=1
21	
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.
27	
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
32	
33	Double-quotes can be used to protect spaces in values, e.g.:
34		param="spaces in here"
35	
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}".
42	
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:
47	
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		XEN	Xen support is enabled
135	
136	In addition, the following text indicates that the option:
137	
138		BUGS=	Relates to possible processor bugs on the said processor.
139		KNL	Is a kernel start-up parameter.
140		BOOT	Is a boot loader parameter.
141	
142	Parameters denoted with BOOT are actually interpreted by the boot
143	loader, and have no meaning to the kernel directly.
144	Do not modify the syntax of boot loader parameters without extreme
145	need or coordination with <Documentation/x86/boot.txt>.
146	
147	There are also arch-specific kernel-parameters not documented here.
148	See for example <Documentation/x86/x86_64/boot-options.txt>.
149	
150	Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151	a trailing = on the name of any parameter states that that parameter will
152	be entered as an environment variable, whereas its absence indicates that
153	it will appear as a kernel argument readable via /proc/cmdline by programs
154	running once the system is up.
155	
156	The number of kernel parameters is not limited, but the length of the
157	complete command line (parameters including spaces etc.) is limited to
158	a fixed number of characters. This limit depends on the architecture
159	and is between 256 and 4096 characters. It is defined in the file
160	./include/asm/setup.h as COMMAND_LINE_SIZE.
161	
162	Finally, the [KMG] suffix is commonly described after a number of kernel
163	parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164	multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165	bytes respectively. Such letter suffixes can also be entirely omitted.
166	
167	
168		acpi=		[HW,ACPI,X86]
169				Advanced Configuration and Power Interface
170				Format: { force | off | strict | noirq | rsdt }
171				force -- enable ACPI if default was off
172				off -- disable ACPI if default was on
173				noirq -- do not use ACPI for IRQ routing
174				strict -- Be less tolerant of platforms that are not
175					strictly ACPI specification compliant.
176				rsdt -- prefer RSDT over (default) XSDT
177				copy_dsdt -- copy DSDT to memory
178	
179				See also Documentation/power/runtime_pm.txt, pci=noacpi
180	
181		acpi_rsdp=	[ACPI,EFI,KEXEC]
182				Pass the RSDP address to the kernel, mostly used
183				on machines running EFI runtime service to boot the
184				second kernel for kdump.
185	
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
191	
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.
198	
199		acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
200		acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
201				Format: <int>
202				CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203				debug output.  Bits in debug_layer correspond to a
204				_COMPONENT in an ACPI source file, e.g.,
205				    #define _COMPONENT ACPI_PCI_COMPONENT
206				Bits in debug_level correspond to a level in
207				ACPI_DEBUG_PRINT statements, e.g.,
208				    ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
209				The debug_level mask defaults to "info".  See
210				Documentation/acpi/debug.txt for more information about
211				debug layers and levels.
212	
213				Enable processor driver info messages:
214				    acpi.debug_layer=0x20000000
215				Enable PCI/PCI interrupt routing info messages:
216				    acpi.debug_layer=0x400000
217				Enable AML "Debug" output, i.e., stores to the Debug
218				object while interpreting AML:
219				    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
220				Enable all messages related to ACPI hardware:
221				    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
222	
223				Some values produce so much output that the system is
224				unusable.  The "log_buf_len" parameter may be useful
225				if you need to capture more output.
226	
227		acpi_force_table_verification	[HW,ACPI]
228				Enable table checksum verification during early stage.
229				By default, this is disabled due to x86 early mapping
230				size limitation.
231	
232		acpi_irq_balance [HW,ACPI]
233				ACPI will balance active IRQs
234				default in APIC mode
235	
236		acpi_irq_nobalance [HW,ACPI]
237				ACPI will not move active IRQs (default)
238				default in PIC mode
239	
240		acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241				Format: <irq>,<irq>...
242	
243		acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
244				use by PCI
245				Format: <irq>,<irq>...
246	
247		acpi_no_auto_serialize	[HW,ACPI]
248				Disable auto-serialization of AML methods
249				AML control methods that contain the opcodes to create
250				named objects will be marked as "Serialized" by the
251				auto-serialization feature.
252				This feature is enabled by default.
253				This option allows to turn off the feature.
254	
255		acpi_no_static_ssdt	[HW,ACPI]
256				Disable installation of static SSDTs at early boot time
257				By default, SSDTs contained in the RSDT/XSDT will be
258				installed automatically and they will appear under
259				/sys/firmware/acpi/tables.
260				This option turns off this feature.
261				Note that specifying this option does not affect
262				dynamic table installation which will install SSDT
263				tables to /sys/firmware/acpi/tables/dynamic.
264	
265		acpica_no_return_repair [HW, ACPI]
266				Disable AML predefined validation mechanism
267				This mechanism can repair the evaluation result to make
268				the return objects more ACPI specification compliant.
269				This option is useful for developers to identify the
270				root cause of an AML interpreter issue when the issue
271				has something to do with the repair mechanism.
272	
273		acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
274				Format: To spoof as Windows 98: ="Microsoft Windows"
275	
276		acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
277				acpi_osi="string1"	# add string1
278				acpi_osi="!string2"	# remove string2
279				acpi_osi=!*		# remove all strings
280				acpi_osi=!		# disable all built-in OS vendor
281							  strings
282				acpi_osi=		# disable all strings
283	
284				'acpi_osi=!' can be used in combination with single or
285				multiple 'acpi_osi="string1"' to support specific OS
286				vendor string(s).  Note that such command can only
287				affect the default state of the OS vendor strings, thus
288				it cannot affect the default state of the feature group
289				strings and the current state of the OS vendor strings,
290				specifying it multiple times through kernel command line
291				is meaningless.  This command is useful when one do not
292				care about the state of the feature group strings which
293				should be controlled by the OSPM.
294				Examples:
295				  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296				     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297				     can make '_OSI("Windows 2000")' TRUE.
298	
299				'acpi_osi=' cannot be used in combination with other
300				'acpi_osi=' command lines, the _OSI method will not
301				exist in the ACPI namespace.  NOTE that such command can
302				only affect the _OSI support state, thus specifying it
303				multiple times through kernel command line is also
304				meaningless.
305				Examples:
306				  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
307				     FALSE.
308	
309				'acpi_osi=!*' can be used in combination with single or
310				multiple 'acpi_osi="string1"' to support specific
311				string(s).  Note that such command can affect the
312				current state of both the OS vendor strings and the
313				feature group strings, thus specifying it multiple times
314				through kernel command line is meaningful.  But it may
315				still not able to affect the final state of a string if
316				there are quirks related to this string.  This command
317				is useful when one want to control the state of the
318				feature group strings to debug BIOS issues related to
319				the OSPM features.
320				Examples:
321				  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322				     '_OSI("Module Device")' FALSE.
323				  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324				     '_OSI("Module Device")' TRUE.
325				  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
326				     equivalent to
327				     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
328				     and
329				     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330				     they all will make '_OSI("Windows 2000")' TRUE.
331	
332		acpi_pm_good	[X86]
333				Override the pmtimer bug detection: force the kernel
334				to assume that this machine's pmtimer latches its value
335				and always returns good values.
336	
337		acpi_sci=	[HW,ACPI] ACPI System Control Interrupt trigger mode
338				Format: { level | edge | high | low }
339	
340		acpi_skip_timer_override [HW,ACPI]
341				Recognize and ignore IRQ0/pin2 Interrupt Override.
342				For broken nForce2 BIOS resulting in XT-PIC timer.
343	
344		acpi_sleep=	[HW,ACPI] Sleep options
345				Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
346					  old_ordering, nonvs, sci_force_enable }
347				See Documentation/power/video.txt for information on
348				s3_bios and s3_mode.
349				s3_beep is for debugging; it makes the PC's speaker beep
350				as soon as the kernel's real-mode entry point is called.
351				s4_nohwsig prevents ACPI hardware signature from being
352				used during resume from hibernation.
353				old_ordering causes the ACPI 1.0 ordering of the _PTS
354				control method, with respect to putting devices into
355				low power states, to be enforced (the ACPI 2.0 ordering
356				of _PTS is used by default).
357				nonvs prevents the kernel from saving/restoring the
358				ACPI NVS memory during suspend/hibernation and resume.
359				sci_force_enable causes the kernel to set SCI_EN directly
360				on resume from S1/S3 (which is against the ACPI spec,
361				but some broken systems don't work without it).
362	
363		acpi_use_timer_override [HW,ACPI]
364				Use timer override. For some broken Nvidia NF5 boards
365				that require a timer override, but don't have HPET
366	
367		acpi_enforce_resources=	[ACPI]
368				{ strict | lax | no }
369				Check for resource conflicts between native drivers
370				and ACPI OperationRegions (SystemIO and SystemMemory
371				only). IO ports and memory declared in ACPI might be
372				used by the ACPI subsystem in arbitrary AML code and
373				can interfere with legacy drivers.
374				strict (default): access to resources claimed by ACPI
375				is denied; legacy drivers trying to access reserved
376				resources will fail to bind to device using them.
377				lax: access to resources claimed by ACPI is allowed;
378				legacy drivers trying to access reserved resources
379				will bind successfully but a warning message is logged.
380				no: ACPI OperationRegions are not marked as reserved,
381				no further checks are performed.
382	
383		acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
384				   kernels.
385	
386		add_efi_memmap	[EFI; X86] Include EFI memory map in
387				kernel's map of available physical RAM.
388	
389		agp=		[AGP]
390				{ off | try_unsupported }
391				off: disable AGP support
392				try_unsupported: try to drive unsupported chipsets
393					(may crash computer or cause data corruption)
394	
395		ALSA		[HW,ALSA]
396				See Documentation/sound/alsa/alsa-parameters.txt
397	
398		alignment=	[KNL,ARM]
399				Allow the default userspace alignment fault handler
400				behaviour to be specified.  Bit 0 enables warnings,
401				bit 1 enables fixups, and bit 2 sends a segfault.
402	
403		align_va_addr=	[X86-64]
404				Align virtual addresses by clearing slice [14:12] when
405				allocating a VMA at process creation time. This option
406				gives you up to 3% performance improvement on AMD F15h
407				machines (where it is enabled by default) for a
408				CPU-intensive style benchmark, and it can vary highly in
409				a microbenchmark depending on workload and compiler.
410	
411				32: only for 32-bit processes
412				64: only for 64-bit processes
413				on: enable for both 32- and 64-bit processes
414				off: disable for both 32- and 64-bit processes
415	
416		alloc_snapshot	[FTRACE]
417				Allocate the ftrace snapshot buffer on boot up when the
418				main buffer is allocated. This is handy if debugging
419				and you need to use tracing_snapshot() on boot up, and
420				do not want to use tracing_snapshot_alloc() as it needs
421				to be done where GFP_KERNEL allocations are allowed.
422	
423		amd_iommu=	[HW,X86-64]
424				Pass parameters to the AMD IOMMU driver in the system.
425				Possible values are:
426				fullflush - enable flushing of IO/TLB entries when
427					    they are unmapped. Otherwise they are
428					    flushed before they will be reused, which
429					    is a lot of faster
430				off	  - do not initialize any AMD IOMMU found in
431					    the system
432				force_isolation - Force device isolation for all
433						  devices. The IOMMU driver is not
434						  allowed anymore to lift isolation
435						  requirements as needed. This option
436						  does not override iommu=pt
437	
438		amd_iommu_dump=	[HW,X86-64]
439				Enable AMD IOMMU driver option to dump the ACPI table
440				for AMD IOMMU. With this option enabled, AMD IOMMU
441				driver will print ACPI tables for AMD IOMMU during
442				IOMMU initialization.
443	
444		amijoy.map=	[HW,JOY] Amiga joystick support
445				Map of devices attached to JOY0DAT and JOY1DAT
446				Format: <a>,<b>
447				See also Documentation/input/joystick.txt
448	
449		analog.map=	[HW,JOY] Analog joystick and gamepad support
450				Specifies type or capabilities of an analog joystick
451				connected to one of 16 gameports
452				Format: <type1>,<type2>,..<type16>
453	
454		apc=		[HW,SPARC]
455				Power management functions (SPARCstation-4/5 + deriv.)
456				Format: noidle
457				Disable APC CPU standby support. SPARCstation-Fox does
458				not play well with APC CPU idle - disable it if you have
459				APC and your system crashes randomly.
460	
461		apic=		[APIC,X86-32] Advanced Programmable Interrupt Controller
462				Change the output verbosity whilst booting
463				Format: { quiet (default) | verbose | debug }
464				Change the amount of debugging information output
465				when initialising the APIC and IO-APIC components.
466	
467		autoconf=	[IPV6]
468				See Documentation/networking/ipv6.txt.
469	
470		show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
471				Limit apic dumping. The parameter defines the maximal
472				number of local apics being dumped. Also it is possible
473				to set it to "all" by meaning -- no limit here.
474				Format: { 1 (default) | 2 | ... | all }.
475				The parameter valid if only apic=debug or
476				apic=verbose is specified.
477				Example: apic=debug show_lapic=all
478	
479		apm=		[APM] Advanced Power Management
480				See header of arch/x86/kernel/apm_32.c.
481	
482		arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483				Format: <io>,<irq>,<nodeID>
484	
485		ataflop=	[HW,M68k]
486	
487		atarimouse=	[HW,MOUSE] Atari Mouse
488	
489		atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
490				EzKey and similar keyboards
491	
492		atkbd.reset=	[HW] Reset keyboard during initialization
493	
494		atkbd.set=	[HW] Select keyboard code set
495				Format: <int> (2 = AT (default), 3 = PS/2)
496	
497		atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
498				keyboards
499	
500		atkbd.softraw=	[HW] Choose between synthetic and real raw mode
501				Format: <bool> (0 = real, 1 = synthetic (default))
502	
503		atkbd.softrepeat= [HW]
504				Use software keyboard repeat
505	
506		audit=		[KNL] Enable the audit sub-system
507				Format: { "0" | "1" } (0 = disabled, 1 = enabled)
508				0 - kernel audit is disabled and can not be enabled
509				    until the next reboot
510				unset - kernel audit is initialized but disabled and
511				    will be fully enabled by the userspace auditd.
512				1 - kernel audit is initialized and partially enabled,
513				    storing at most audit_backlog_limit messages in
514				    RAM until it is fully enabled by the userspace
515				    auditd.
516				Default: unset
517	
518		audit_backlog_limit= [KNL] Set the audit queue size limit.
519				Format: <int> (must be >=0)
520				Default: 64
521	
522		baycom_epp=	[HW,AX25]
523				Format: <io>,<mode>
524	
525		baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
526				Format: <io>,<mode>
527				See header of drivers/net/hamradio/baycom_par.c.
528	
529		baycom_ser_fdx=	[HW,AX25]
530				BayCom Serial Port AX.25 Modem (Full Duplex Mode)
531				Format: <io>,<irq>,<mode>[,<baud>]
532				See header of drivers/net/hamradio/baycom_ser_fdx.c.
533	
534		baycom_ser_hdx=	[HW,AX25]
535				BayCom Serial Port AX.25 Modem (Half Duplex Mode)
536				Format: <io>,<irq>,<mode>
537				See header of drivers/net/hamradio/baycom_ser_hdx.c.
538	
539		blkdevparts=	Manual partition parsing of block device(s) for
540				embedded devices based on command line input.
541				See Documentation/block/cmdline-partition.txt
542	
543		boot_delay=	Milliseconds to delay each printk during boot.
544				Values larger than 10 seconds (10000) are changed to
545				no delay (0).
546				Format: integer
547	
548		bootmem_debug	[KNL] Enable bootmem allocator debug messages.
549	
550		bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
551		bttv.radio=	Most important insmod options are available as
552				kernel args too.
553		bttv.pll=	See Documentation/video4linux/bttv/Insmod-options
554		bttv.tuner=
555	
556		bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
557				firmware feature for flushing multiple hpte entries
558				at a time.
559	
560		c101=		[NET] Moxa C101 synchronous serial card
561	
562		cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
563				Sometimes CPU hardware bugs make them report the cache
564				size incorrectly. The kernel will attempt work arounds
565				to fix known problems, but for some CPUs it is not
566				possible to determine what the correct size should be.
567				This option provides an override for these situations.
568	
569		ccw_timeout_log [S390]
570				See Documentation/s390/CommonIO for details.
571	
572		cgroup_disable= [KNL] Disable a particular controller
573				Format: {name of the controller(s) to disable}
574				The effects of cgroup_disable=foo are:
575				- foo isn't auto-mounted if you mount all cgroups in
576				  a single hierarchy
577				- foo isn't visible as an individually mountable
578				  subsystem
579				{Currently only "memory" controller deal with this and
580				cut the overhead, others just disable the usage. So
581				only cgroup_disable=memory is actually worthy}
582	
583		checkreqprot	[SELINUX] Set initial checkreqprot flag value.
584				Format: { "0" | "1" }
585				See security/selinux/Kconfig help text.
586				0 -- check protection applied by kernel (includes
587					any implied execute protection).
588				1 -- check protection requested by application.
589				Default value is set via a kernel config option.
590				Value can be changed at runtime via
591					/selinux/checkreqprot.
592	
593		cio_ignore=	[S390]
594				See Documentation/s390/CommonIO for details.
595		clk_ignore_unused
596				[CLK]
597				Keep all clocks already enabled by bootloader on,
598				even if no driver has claimed them. This is useful
599				for debug and development, but should not be
600				needed on a platform with proper driver support.
601				For more information, see Documentation/clk.txt.
602	
603		clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
604				[Deprecated]
605				Forces specified clocksource (if available) to be used
606				when calculating gettimeofday(). If specified
607				clocksource is not available, it defaults to PIT.
608				Format: { pit | tsc | cyclone | pmtmr }
609	
610		clocksource=	Override the default clocksource
611				Format: <string>
612				Override the default clocksource and use the clocksource
613				with the name specified.
614				Some clocksource names to choose from, depending on
615				the platform:
616				[all] jiffies (this is the base, fallback clocksource)
617				[ACPI] acpi_pm
618				[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
619					pxa_timer,timer3,32k_counter,timer0_1
620				[AVR32] avr32
621				[X86-32] pit,hpet,tsc;
622					scx200_hrt on Geode; cyclone on IBM x440
623				[MIPS] MIPS
624				[PARISC] cr16
625				[S390] tod
626				[SH] SuperH
627				[SPARC64] tick
628				[X86-64] hpet,tsc
629	
630		clearcpuid=BITNUM [X86]
631				Disable CPUID feature X for the kernel. See
632				arch/x86/include/asm/cpufeature.h for the valid bit
633				numbers. Note the Linux specific bits are not necessarily
634				stable over kernel options, but the vendor specific
635				ones should be.
636				Also note that user programs calling CPUID directly
637				or using the feature without checking anything
638				will still see it. This just prevents it from
639				being used by the kernel or shown in /proc/cpuinfo.
640				Also note the kernel might malfunction if you disable
641				some critical bits.
642	
643		cma=nn[MG]@[start[MG][-end[MG]]]
644				[ARM,X86,KNL]
645				Sets the size of kernel global memory area for
646				contiguous memory allocations and optionally the
647				placement constraint by the physical address range of
648				memory allocations. For more information, see
649				include/linux/dma-contiguous.h
650	
651		cmo_free_hint=	[PPC] Format: { yes | no }
652				Specify whether pages are marked as being inactive
653				when they are freed.  This is used in CMO environments
654				to determine OS memory pressure for page stealing by
655				a hypervisor.
656				Default: yes
657	
658		coherent_pool=nn[KMG]	[ARM,KNL]
659				Sets the size of memory pool for coherent, atomic dma
660				allocations, by default set to 256K.
661	
662		code_bytes	[X86] How many bytes of object code to print
663				in an oops report.
664				Range: 0 - 8192
665				Default: 64
666	
667		com20020=	[HW,NET] ARCnet - COM20020 chipset
668				Format:
669				<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
670	
671		com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
672				Format: <io>[,<irq>]
673	
674		com90xx=	[HW,NET]
675				ARCnet - COM90xx chipset (memory-mapped buffers)
676				Format: <io>[,<irq>[,<memstart>]]
677	
678		condev=		[HW,S390] console device
679		conmode=
680	
681		console=	[KNL] Output console device and options.
682	
683			tty<n>	Use the virtual console device <n>.
684	
685			ttyS<n>[,options]
686			ttyUSB0[,options]
687				Use the specified serial port.  The options are of
688				the form "bbbbpnf", where "bbbb" is the baud rate,
689				"p" is parity ("n", "o", or "e"), "n" is number of
690				bits, and "f" is flow control ("r" for RTS or
691				omit it).  Default is "9600n8".
692	
693				See Documentation/serial-console.txt for more
694				information.  See
695				Documentation/networking/netconsole.txt for an
696				alternative.
697	
698			uart[8250],io,<addr>[,options]
699			uart[8250],mmio,<addr>[,options]
700				Start an early, polled-mode console on the 8250/16550
701				UART at the specified I/O port or MMIO address,
702				switching to the matching ttyS device later.  The
703				options are the same as for ttyS, above.
704			hvc<n>	Use the hypervisor console device <n>. This is for
705				both Xen and PowerPC hypervisors.
706	
707	                If the device connected to the port is not a TTY but a braille
708	                device, prepend "brl," before the device type, for instance
709				console=brl,ttyS0
710			For now, only VisioBraille is supported.
711	
712		consoleblank=	[KNL] The console blank (screen saver) timeout in
713				seconds. Defaults to 10*60 = 10mins. A value of 0
714				disables the blank timer.
715	
716		coredump_filter=
717				[KNL] Change the default value for
718				/proc/<pid>/coredump_filter.
719				See also Documentation/filesystems/proc.txt.
720	
721		cpuidle.off=1	[CPU_IDLE]
722				disable the cpuidle sub-system
723	
724		cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
725				Format:
726				<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
727	
728		crashkernel=size[KMG][@offset[KMG]]
729				[KNL] Using kexec, Linux can switch to a 'crash kernel'
730				upon panic. This parameter reserves the physical
731				memory region [offset, offset + size] for that kernel
732				image. If '@offset' is omitted, then a suitable offset
733				is selected automatically. Check
734				Documentation/kdump/kdump.txt for further details.
735	
736		crashkernel=range1:size1[,range2:size2,...][@offset]
737				[KNL] Same as above, but depends on the memory
738				in the running system. The syntax of range is
739				start-[end] where start and end are both
740				a memory unit (amount[KMG]). See also
741				Documentation/kdump/kdump.txt for an example.
742	
743		crashkernel=size[KMG],high
744				[KNL, x86_64] range could be above 4G. Allow kernel
745				to allocate physical memory region from top, so could
746				be above 4G if system have more than 4G ram installed.
747				Otherwise memory region will be allocated below 4G, if
748				available.
749				It will be ignored if crashkernel=X is specified.
750		crashkernel=size[KMG],low
751				[KNL, x86_64] range under 4G. When crashkernel=X,high
752				is passed, kernel could allocate physical memory region
753				above 4G, that cause second kernel crash on system
754				that require some amount of low memory, e.g. swiotlb
755				requires at least 64M+32K low memory.  Kernel would
756				try to allocate 72M below 4G automatically.
757				This one let user to specify own low range under 4G
758				for second kernel instead.
759				0: to disable low allocation.
760				It will be ignored when crashkernel=X,high is not used
761				or memory reserved is below 4G.
762	
763		cs89x0_dma=	[HW,NET]
764				Format: <dma>
765	
766		cs89x0_media=	[HW,NET]
767				Format: { rj45 | aui | bnc }
768	
769		dasd=		[HW,NET]
770				See header of drivers/s390/block/dasd_devmap.c.
771	
772		db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
773				(one device per port)
774				Format: <port#>,<type>
775				See also Documentation/input/joystick-parport.txt
776	
777		ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
778				time. See Documentation/dynamic-debug-howto.txt for
779				details.  Deprecated, see dyndbg.
780	
781		debug		[KNL] Enable kernel debugging (events log level).
782	
783		debug_locks_verbose=
784				[KNL] verbose self-tests
785				Format=<0|1>
786				Print debugging info while doing the locking API
787				self-tests.
788				We default to 0 (no extra messages), setting it to
789				1 will print _a lot_ more information - normally
790				only useful to kernel developers.
791	
792		debug_objects	[KNL] Enable object debugging
793	
794		no_debug_objects
795				[KNL] Disable object debugging
796	
797		debug_guardpage_minorder=
798				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
799				parameter allows control of the order of pages that will
800				be intentionally kept free (and hence protected) by the
801				buddy allocator. Bigger value increase the probability
802				of catching random memory corruption, but reduce the
803				amount of memory for normal system use. The maximum
804				possible value is MAX_ORDER/2.  Setting this parameter
805				to 1 or 2 should be enough to identify most random
806				memory corruption problems caused by bugs in kernel or
807				driver code when a CPU writes to (or reads from) a
808				random memory location. Note that there exists a class
809				of memory corruptions problems caused by buggy H/W or
810				F/W or by drivers badly programing DMA (basically when
811				memory is written at bus level and the CPU MMU is
812				bypassed) which are not detectable by
813				CONFIG_DEBUG_PAGEALLOC, hence this option will not help
814				tracking down these problems.
815	
816		debugpat	[X86] Enable PAT debugging
817	
818		decnet.addr=	[HW,NET]
819				Format: <area>[,<node>]
820				See also Documentation/networking/decnet.txt.
821	
822		default_hugepagesz=
823				[same as hugepagesz=] The size of the default
824				HugeTLB page size. This is the size represented by
825				the legacy /proc/ hugepages APIs, used for SHM, and
826				default size when mounting hugetlbfs filesystems.
827				Defaults to the default architecture's huge page size
828				if not specified.
829	
830		dhash_entries=	[KNL]
831				Set number of hash buckets for dentry cache.
832	
833		disable=	[IPV6]
834				See Documentation/networking/ipv6.txt.
835	
836		disable_cpu_apicid= [X86,APIC,SMP]
837				Format: <int>
838				The number of initial APIC ID for the
839				corresponding CPU to be disabled at boot,
840				mostly used for the kdump 2nd kernel to
841				disable BSP to wake up multiple CPUs without
842				causing system reset or hang due to sending
843				INIT from AP to BSP.
844	
845		disable_ddw     [PPC/PSERIES]
846				Disable Dynamic DMA Window support. Use this if
847				to workaround buggy firmware.
848	
849		disable_ipv6=	[IPV6]
850				See Documentation/networking/ipv6.txt.
851	
852		disable_mtrr_cleanup [X86]
853				The kernel tries to adjust MTRR layout from continuous
854				to discrete, to make X server driver able to add WB
855				entry later. This parameter disables that.
856	
857		disable_mtrr_trim [X86, Intel and AMD only]
858				By default the kernel will trim any uncacheable
859				memory out of your available memory pool based on
860				MTRR settings.  This parameter disables that behavior,
861				possibly causing your machine to run very slowly.
862	
863		disable_timer_pin_1 [X86]
864				Disable PIN 1 of APIC timer
865				Can be useful to work around chipset bugs.
866	
867		dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
868				this option disables the debugging code at boot.
869	
870		dma_debug_entries=<number>
871				This option allows to tune the number of preallocated
872				entries for DMA-API debugging code. One entry is
873				required per DMA-API allocation. Use this if the
874				DMA-API debugging code disables itself because the
875				architectural default is too low.
876	
877		dma_debug_driver=<driver_name>
878				With this option the DMA-API debugging driver
879				filter feature can be enabled at boot time. Just
880				pass the driver to filter for as the parameter.
881				The filter can be disabled or changed to another
882				driver later using sysfs.
883	
884		drm_kms_helper.edid_firmware=[<connector>:]<file>
885				Broken monitors, graphic adapters and KVMs may
886				send no or incorrect EDID data sets. This parameter
887				allows to specify an EDID data set in the
888				/lib/firmware directory that is used instead.
889				Generic built-in EDID data sets are used, if one of
890				edid/1024x768.bin, edid/1280x1024.bin,
891				edid/1680x1050.bin, or edid/1920x1080.bin is given
892				and no file with the same name exists. Details and
893				instructions how to build your own EDID data are
894				available in Documentation/EDID/HOWTO.txt. An EDID
895				data set will only be used for a particular connector,
896				if its name and a colon are prepended to the EDID
897				name.
898	
899		dscc4.setup=	[NET]
900	
901		dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
902		module.dyndbg[="val"]
903				Enable debug messages at boot time.  See
904				Documentation/dynamic-debug-howto.txt for details.
905	
906		early_ioremap_debug [KNL]
907				Enable debug messages in early_ioremap support. This
908				is useful for tracking down temporary early mappings
909				which are not unmapped.
910	
911		earlycon=	[KNL] Output early console device and options.
912	
913			uart[8250],io,<addr>[,options]
914			uart[8250],mmio,<addr>[,options]
915			uart[8250],mmio32,<addr>[,options]
916				Start an early, polled-mode console on the 8250/16550
917				UART at the specified I/O port or MMIO address.
918				MMIO inter-register address stride is either 8-bit
919				(mmio) or 32-bit (mmio32).
920				The options are the same as for ttyS, above.
921	
922			pl011,<addr>
923				Start an early, polled-mode console on a pl011 serial
924				port at the specified address. The pl011 serial port
925				must already be setup and configured. Options are not
926				yet supported.
927	
928			smh	Use ARM semihosting calls for early console.
929	
930		earlyprintk=	[X86,SH,BLACKFIN,ARM,M68k]
931				earlyprintk=vga
932				earlyprintk=efi
933				earlyprintk=xen
934				earlyprintk=serial[,ttySn[,baudrate]]
935				earlyprintk=serial[,0x...[,baudrate]]
936				earlyprintk=ttySn[,baudrate]
937				earlyprintk=dbgp[debugController#]
938	
939				earlyprintk is useful when the kernel crashes before
940				the normal console is initialized. It is not enabled by
941				default because it has some cosmetic problems.
942	
943				Append ",keep" to not disable it when the real console
944				takes over.
945	
946				Only one of vga, efi, serial, or usb debug port can
947				be used at a time.
948	
949				Currently only ttyS0 and ttyS1 may be specified by
950				name.  Other I/O ports may be explicitly specified
951				on some architectures (x86 and arm at least) by
952				replacing ttySn with an I/O port address, like this:
953					earlyprintk=serial,0x1008,115200
954				You can find the port for a given device in
955				/proc/tty/driver/serial:
956					2: uart:ST16650V2 port:00001008 irq:18 ...
957	
958				Interaction with the standard serial driver is not
959				very good.
960	
961				The VGA and EFI output is eventually overwritten by
962				the real console.
963	
964				The xen output can only be used by Xen PV guests.
965	
966		edac_report=	[HW,EDAC] Control how to report EDAC event
967				Format: {"on" | "off" | "force"}
968				on: enable EDAC to report H/W event. May be overridden
969				by other higher priority error reporting module.
970				off: disable H/W event reporting through EDAC.
971				force: enforce the use of EDAC to report H/W event.
972				default: on.
973	
974		ekgdboc=	[X86,KGDB] Allow early kernel console debugging
975				ekgdboc=kbd
976	
977				This is designed to be used in conjunction with
978				the boot argument: earlyprintk=vga
979	
980		edd=		[EDD]
981				Format: {"off" | "on" | "skip[mbr]"}
982	
983		efi=		[EFI]
984				Format: { "old_map" }
985				old_map [X86-64]: switch to the old ioremap-based EFI
986				runtime services mapping. 32-bit still uses this one by
987				default.
988	
989		efi_no_storage_paranoia [EFI; X86]
990				Using this parameter you can use more than 50% of
991				your efi variable storage. Use this parameter only if
992				you are really sure that your UEFI does sane gc and
993				fulfills the spec otherwise your board may brick.
994	
995		eisa_irq_edge=	[PARISC,HW]
996				See header of drivers/parisc/eisa.c.
997	
998		elanfreq=	[X86-32]
999				See comment before function elanfreq_setup() in
1000				arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1001	
1002		elevator=	[IOSCHED]
1003				Format: {"cfq" | "deadline" | "noop"}
1004				See Documentation/block/cfq-iosched.txt and
1005				Documentation/block/deadline-iosched.txt for details.
1006	
1007		elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1008				Specifies physical address of start of kernel core
1009				image elf header and optionally the size. Generally
1010				kexec loader will pass this option to capture kernel.
1011				See Documentation/kdump/kdump.txt for details.
1012	
1013		enable_mtrr_cleanup [X86]
1014				The kernel tries to adjust MTRR layout from continuous
1015				to discrete, to make X server driver able to add WB
1016				entry later. This parameter enables that.
1017	
1018		enable_timer_pin_1 [X86]
1019				Enable PIN 1 of APIC timer
1020				Can be useful to work around chipset bugs
1021				(in particular on some ATI chipsets).
1022				The kernel tries to set a reasonable default.
1023	
1024		enforcing	[SELINUX] Set initial enforcing status.
1025				Format: {"0" | "1"}
1026				See security/selinux/Kconfig help text.
1027				0 -- permissive (log only, no denials).
1028				1 -- enforcing (deny and log).
1029				Default value is 0.
1030				Value can be changed at runtime via /selinux/enforce.
1031	
1032		erst_disable	[ACPI]
1033				Disable Error Record Serialization Table (ERST)
1034				support.
1035	
1036		ether=		[HW,NET] Ethernet cards parameters
1037				This option is obsoleted by the "netdev=" option, which
1038				has equivalent usage. See its documentation for details.
1039	
1040		evm=		[EVM]
1041				Format: { "fix" }
1042				Permit 'security.evm' to be updated regardless of
1043				current integrity status.
1044	
1045		failslab=
1046		fail_page_alloc=
1047		fail_make_request=[KNL]
1048				General fault injection mechanism.
1049				Format: <interval>,<probability>,<space>,<times>
1050				See also Documentation/fault-injection/.
1051	
1052		floppy=		[HW]
1053				See Documentation/blockdev/floppy.txt.
1054	
1055		force_pal_cache_flush
1056				[IA-64] Avoid check_sal_cache_flush which may hang on
1057				buggy SAL_CACHE_FLUSH implementations. Using this
1058				parameter will force ia64_sal_cache_flush to call
1059				ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1060	
1061		forcepae [X86-32]
1062				Forcefully enable Physical Address Extension (PAE).
1063				Many Pentium M systems disable PAE but may have a
1064				functionally usable PAE implementation.
1065				Warning: use of this parameter will taint the kernel
1066				and may cause unknown problems.
1067	
1068		ftrace=[tracer]
1069				[FTRACE] will set and start the specified tracer
1070				as early as possible in order to facilitate early
1071				boot debugging.
1072	
1073		ftrace_dump_on_oops[=orig_cpu]
1074				[FTRACE] will dump the trace buffers on oops.
1075				If no parameter is passed, ftrace will dump
1076				buffers of all CPUs, but if you pass orig_cpu, it will
1077				dump only the buffer of the CPU that triggered the
1078				oops.
1079	
1080		ftrace_filter=[function-list]
1081				[FTRACE] Limit the functions traced by the function
1082				tracer at boot up. function-list is a comma separated
1083				list of functions. This list can be changed at run
1084				time by the set_ftrace_filter file in the debugfs
1085				tracing directory.
1086	
1087		ftrace_notrace=[function-list]
1088				[FTRACE] Do not trace the functions specified in
1089				function-list. This list can be changed at run time
1090				by the set_ftrace_notrace file in the debugfs
1091				tracing directory.
1092	
1093		ftrace_graph_filter=[function-list]
1094				[FTRACE] Limit the top level callers functions traced
1095				by the function graph tracer at boot up.
1096				function-list is a comma separated list of functions
1097				that can be changed at run time by the
1098				set_graph_function file in the debugfs tracing directory.
1099	
1100		gamecon.map[2|3]=
1101				[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1102				support via parallel port (up to 5 devices per port)
1103				Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1104				See also Documentation/input/joystick-parport.txt
1105	
1106		gamma=		[HW,DRM]
1107	
1108		gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
1109				Format: off | on
1110				default: on
1111	
1112		gcov_persist=	[GCOV] When non-zero (default), profiling data for
1113				kernel modules is saved and remains accessible via
1114				debugfs, even when the module is unloaded/reloaded.
1115				When zero, profiling data is discarded and associated
1116				debugfs files are removed at module unload time.
1117	
1118		gpt		[EFI] Forces disk with valid GPT signature but
1119				invalid Protective MBR to be treated as GPT. If the
1120				primary GPT is corrupted, it enables the backup/alternate
1121				GPT to be used instead.
1122	
1123		grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1124				the "Enable 0" bit of the configuration register.
1125				Format: 0 | 1
1126				Default: 0
1127		grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1128				the "Enable 0" bit of the configuration register.
1129				Format: 0 | 1
1130				Default: 0
1131		grcan.select=	[HW] Select which physical interface to use.
1132				Format: 0 | 1
1133				Default: 0
1134		grcan.txsize=	[HW] Sets the size of the tx buffer.
1135				Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1136				Default: 1024
1137		grcan.rxsize=	[HW] Sets the size of the rx buffer.
1138				Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1139				Default: 1024
1140	
1141		hashdist=	[KNL,NUMA] Large hashes allocated during boot
1142				are distributed across NUMA nodes.  Defaults on
1143				for 64-bit NUMA, off otherwise.
1144				Format: 0 | 1 (for off | on)
1145	
1146		hcl=		[IA-64] SGI's Hardware Graph compatibility layer
1147	
1148		hd=		[EIDE] (E)IDE hard drive subsystem geometry
1149				Format: <cyl>,<head>,<sect>
1150	
1151		hest_disable	[ACPI]
1152				Disable Hardware Error Source Table (HEST) support;
1153				corresponding firmware-first mode error processing
1154				logic will be disabled.
1155	
1156		highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
1157				size of <nn>. This works even on boxes that have no
1158				highmem otherwise. This also works to reduce highmem
1159				size on bigger boxes.
1160	
1161		highres=	[KNL] Enable/disable high resolution timer mode.
1162				Valid parameters: "on", "off"
1163				Default: "on"
1164	
1165		hisax=		[HW,ISDN]
1166				See Documentation/isdn/README.HiSax.
1167	
1168		hlt		[BUGS=ARM,SH]
1169	
1170		hpet=		[X86-32,HPET] option to control HPET usage
1171				Format: { enable (default) | disable | force |
1172					verbose }
1173				disable: disable HPET and use PIT instead
1174				force: allow force enabled of undocumented chips (ICH4,
1175					VIA, nVidia)
1176				verbose: show contents of HPET registers during setup
1177	
1178		hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1179				registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1180	
1181		hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1182		hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1183				On x86-64 and powerpc, this option can be specified
1184				multiple times interleaved with hugepages= to reserve
1185				huge pages of different sizes. Valid pages sizes on
1186				x86-64 are 2M (when the CPU supports "pse") and 1G
1187				(when the CPU supports the "pdpe1gb" cpuinfo flag)
1188				Note that 1GB pages can only be allocated at boot time
1189				using hugepages= and not freed afterwards.
1190	
1191		hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
1192				       terminal devices. Valid values: 0..8
1193		hvc_iucv_allow=	[S390] Comma-separated list of z/VM user IDs.
1194				       If specified, z/VM IUCV HVC accepts connections
1195				       from listed z/VM user IDs only.
1196	
1197		hwthread_map=	[METAG] Comma-separated list of Linux cpu id to
1198				        hardware thread id mappings.
1199					Format: <cpu>:<hwthread>
1200	
1201		keep_bootcon	[KNL]
1202				Do not unregister boot console at start. This is only
1203				useful for debugging when something happens in the window
1204				between unregistering the boot console and initializing
1205				the real console.
1206	
1207		i2c_bus=	[HW] Override the default board specific I2C bus speed
1208				     or register an additional I2C bus that is not
1209				     registered from board initialization code.
1210				     Format:
1211				     <bus_id>,<clkrate>
1212	
1213		i8042.debug	[HW] Toggle i8042 debug mode
1214		i8042.direct	[HW] Put keyboard port into non-translated mode
1215		i8042.dumbkbd	[HW] Pretend that controller can only read data from
1216				     keyboard and cannot control its state
1217				     (Don't attempt to blink the leds)
1218		i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1219		i8042.nokbd	[HW] Don't check/create keyboard port
1220		i8042.noloop	[HW] Disable the AUX Loopback command while probing
1221				     for the AUX port
1222		i8042.nomux	[HW] Don't check presence of an active multiplexing
1223				     controller
1224		i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1225				     controllers
1226		i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1227		i8042.reset	[HW] Reset the controller during init and cleanup
1228		i8042.unlock	[HW] Unlock (ignore) the keylock
1229	
1230		i810=		[HW,DRM]
1231	
1232		i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
1233				indicates that the driver is running on unsupported
1234				hardware.
1235		i8k.force	[HW] Activate i8k driver even if SMM BIOS signature
1236				does not match list of supported models.
1237		i8k.power_status
1238				[HW] Report power status in /proc/i8k
1239				(disabled by default)
1240		i8k.restricted	[HW] Allow controlling fans only if SYS_ADMIN
1241				capability is set.
1242	
1243		i915.invert_brightness=
1244				[DRM] Invert the sense of the variable that is used to
1245				set the brightness of the panel backlight. Normally a
1246				brightness value of 0 indicates backlight switched off,
1247				and the maximum of the brightness value sets the backlight
1248				to maximum brightness. If this parameter is set to 0
1249				(default) and the machine requires it, or this parameter
1250				is set to 1, a brightness value of 0 sets the backlight
1251				to maximum brightness, and the maximum of the brightness
1252				value switches the backlight off.
1253				-1 -- never invert brightness
1254				 0 -- machine default
1255				 1 -- force brightness inversion
1256	
1257		icn=		[HW,ISDN]
1258				Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1259	
1260		ide-core.nodma=	[HW] (E)IDE subsystem
1261				Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1262				.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1263				.cdrom .chs .ignore_cable are additional options
1264				See Documentation/ide/ide.txt.
1265	
1266		ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1267				Claim all unknown PCI IDE storage controllers.
1268	
1269		idle=		[X86]
1270				Format: idle=poll, idle=halt, idle=nomwait
1271				Poll forces a polling idle loop that can slightly
1272				improve the performance of waking up a idle CPU, but
1273				will use a lot of power and make the system run hot.
1274				Not recommended.
1275				idle=halt: Halt is forced to be used for CPU idle.
1276				In such case C2/C3 won't be used again.
1277				idle=nomwait: Disable mwait for CPU C-states
1278	
1279		ignore_loglevel	[KNL]
1280				Ignore loglevel setting - this will print /all/
1281				kernel messages to the console. Useful for debugging.
1282				We also add it as printk module parameter, so users
1283				could change it dynamically, usually by
1284				/sys/module/printk/parameters/ignore_loglevel.
1285	
1286		ihash_entries=	[KNL]
1287				Set number of hash buckets for inode cache.
1288	
1289		ima_appraise=	[IMA] appraise integrity measurements
1290				Format: { "off" | "enforce" | "fix" }
1291				default: "enforce"
1292	
1293		ima_appraise_tcb [IMA]
1294				The builtin appraise policy appraises all files
1295				owned by uid=0.
1296	
1297		ima_hash=	[IMA]
1298				Format: { md5 | sha1 | rmd160 | sha256 | sha384
1299					   | sha512 | ... }
1300				default: "sha1"
1301	
1302				The list of supported hash algorithms is defined
1303				in crypto/hash_info.h.
1304	
1305		ima_tcb		[IMA]
1306				Load a policy which meets the needs of the Trusted
1307				Computing Base.  This means IMA will measure all
1308				programs exec'd, files mmap'd for exec, and all files
1309				opened for read by uid=0.
1310	
1311		ima_template=   [IMA]
1312				Select one of defined IMA measurements template formats.
1313				Formats: { "ima" | "ima-ng" }
1314				Default: "ima-ng"
1315	
1316		init=		[KNL]
1317				Format: <full_path>
1318				Run specified binary instead of /sbin/init as init
1319				process.
1320	
1321		initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
1322				for working out where the kernel is dying during
1323				startup.
1324	
1325		initcall_blacklist=  [KNL] Do not execute a comma-separated list of
1326				initcall functions.  Useful for debugging built-in
1327				modules and initcalls.
1328	
1329		initrd=		[BOOT] Specify the location of the initial ramdisk
1330	
1331		inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
1332				Format: <irq>
1333	
1334		int_pln_enable  [x86] Enable power limit notification interrupt
1335	
1336		integrity_audit=[IMA]
1337				Format: { "0" | "1" }
1338				0 -- basic integrity auditing messages. (Default)
1339				1 -- additional integrity auditing messages.
1340	
1341		intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1342			on
1343				Enable intel iommu driver.
1344			off
1345				Disable intel iommu driver.
1346			igfx_off [Default Off]
1347				By default, gfx is mapped as normal device. If a gfx
1348				device has a dedicated DMAR unit, the DMAR unit is
1349				bypassed by not enabling DMAR with this option. In
1350				this case, gfx device will use physical address for
1351				DMA.
1352			forcedac [x86_64]
1353				With this option iommu will not optimize to look
1354				for io virtual address below 32-bit forcing dual
1355				address cycle on pci bus for cards supporting greater
1356				than 32-bit addressing. The default is to look
1357				for translation below 32-bit and if not available
1358				then look in the higher range.
1359			strict [Default Off]
1360				With this option on every unmap_single operation will
1361				result in a hardware IOTLB flush operation as opposed
1362				to batching them for performance.
1363			sp_off [Default Off]
1364				By default, super page will be supported if Intel IOMMU
1365				has the capability. With this option, super page will
1366				not be supported.
1367	
1368		intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
1369				0	disables intel_idle and fall back on acpi_idle.
1370				1 to 6	specify maximum depth of C-state.
1371	
1372		intel_pstate=  [X86]
1373			       disable
1374			         Do not enable intel_pstate as the default
1375			         scaling driver for the supported processors
1376	
1377		intremap=	[X86-64, Intel-IOMMU]
1378				on	enable Interrupt Remapping (default)
1379				off	disable Interrupt Remapping
1380				nosid	disable Source ID checking
1381				no_x2apic_optout
1382					BIOS x2APIC opt-out request will be ignored
1383	
1384		iomem=		Disable strict checking of access to MMIO memory
1385			strict	regions from userspace.
1386			relaxed
1387	
1388		iommu=		[x86]
1389			off
1390			force
1391			noforce
1392			biomerge
1393			panic
1394			nopanic
1395			merge
1396			nomerge
1397			forcesac
1398			soft
1399			pt		[x86, IA-64]
1400	
1401	
1402		io7=		[HW] IO7 for Marvel based alpha systems
1403				See comment before marvel_specify_io7 in
1404				arch/alpha/kernel/core_marvel.c.
1405	
1406		io_delay=	[X86] I/O delay method
1407			0x80
1408				Standard port 0x80 based delay
1409			0xed
1410				Alternate port 0xed based delay (needed on some systems)
1411			udelay
1412				Simple two microseconds delay
1413			none
1414				No delay
1415	
1416		ip=		[IP_PNP]
1417				See Documentation/filesystems/nfs/nfsroot.txt.
1418	
1419		ip2=		[HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1420				See comment before ip2_setup() in
1421				drivers/char/ip2/ip2base.c.
1422	
1423		irqfixup	[HW]
1424				When an interrupt is not handled search all handlers
1425				for it. Intended to get systems with badly broken
1426				firmware running.
1427	
1428		irqpoll		[HW]
1429				When an interrupt is not handled search all handlers
1430				for it. Also check all handlers each timer
1431				interrupt. Intended to get systems with badly broken
1432				firmware running.
1433	
1434		isapnp=		[ISAPNP]
1435				Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1436	
1437		isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
1438				Format:
1439				<cpu number>,...,<cpu number>
1440				or
1441				<cpu number>-<cpu number>
1442				(must be a positive range in ascending order)
1443				or a mixture
1444				<cpu number>,...,<cpu number>-<cpu number>
1445	
1446				This option can be used to specify one or more CPUs
1447				to isolate from the general SMP balancing and scheduling
1448				algorithms. You can move a process onto or off an
1449				"isolated" CPU via the CPU affinity syscalls or cpuset.
1450				<cpu number> begins at 0 and the maximum value is
1451				"number of CPUs in system - 1".
1452	
1453				This option is the preferred way to isolate CPUs. The
1454				alternative -- manually setting the CPU mask of all
1455				tasks in the system -- can cause problems and
1456				suboptimal load balancer performance.
1457	
1458		iucv=		[HW,NET]
1459	
1460		ivrs_ioapic	[HW,X86_64]
1461				Provide an override to the IOAPIC-ID<->DEVICE-ID
1462				mapping provided in the IVRS ACPI table. For
1463				example, to map IOAPIC-ID decimal 10 to
1464				PCI device 00:14.0 write the parameter as:
1465					ivrs_ioapic[10]=00:14.0
1466	
1467		ivrs_hpet	[HW,X86_64]
1468				Provide an override to the HPET-ID<->DEVICE-ID
1469				mapping provided in the IVRS ACPI table. For
1470				example, to map HPET-ID decimal 0 to
1471				PCI device 00:14.0 write the parameter as:
1472					ivrs_hpet[0]=00:14.0
1473	
1474		js=		[HW,JOY] Analog joystick
1475				See Documentation/input/joystick.txt.
1476	
1477		kaslr/nokaslr	[X86]
1478				Enable/disable kernel and module base offset ASLR
1479				(Address Space Layout Randomization) if built into
1480				the kernel. When CONFIG_HIBERNATION is selected,
1481				kASLR is disabled by default. When kASLR is enabled,
1482				hibernation will be disabled.
1483	
1484		keepinitrd	[HW,ARM]
1485	
1486		kernelcore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
1487				specifies the amount of memory usable by the kernel
1488				for non-movable allocations.  The requested amount is
1489				spread evenly throughout all nodes in the system. The
1490				remaining memory in each node is used for Movable
1491				pages. In the event, a node is too small to have both
1492				kernelcore and Movable pages, kernelcore pages will
1493				take priority and other nodes will have a larger number
1494				of Movable pages.  The Movable zone is used for the
1495				allocation of pages that may be reclaimed or moved
1496				by the page migration subsystem.  This means that
1497				HugeTLB pages may not be allocated from this zone.
1498				Note that allocations like PTEs-from-HighMem still
1499				use the HighMem zone if it exists, and the Normal
1500				zone if it does not.
1501	
1502		kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
1503				Format: <Controller#>[,poll interval]
1504				The controller # is the number of the ehci usb debug
1505				port as it is probed via PCI.  The poll interval is
1506				optional and is the number seconds in between
1507				each poll cycle to the debug port in case you need
1508				the functionality for interrupting the kernel with
1509				gdb or control-c on the dbgp connection.  When
1510				not using this parameter you use sysrq-g to break into
1511				the kernel debugger.
1512	
1513		kgdboc=		[KGDB,HW] kgdb over consoles.
1514				Requires a tty driver that supports console polling,
1515				or a supported polling keyboard driver (non-usb).
1516				 Serial only format: <serial_device>[,baud]
1517				 keyboard only format: kbd
1518				 keyboard and serial format: kbd,<serial_device>[,baud]
1519				Optional Kernel mode setting:
1520				 kms, kbd format: kms,kbd
1521				 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1522	
1523		kgdbwait	[KGDB] Stop kernel execution and enter the
1524				kernel debugger at the earliest opportunity.
1525	
1526		kmac=		[MIPS] korina ethernet MAC address.
1527				Configure the RouterBoard 532 series on-chip
1528				Ethernet adapter MAC address.
1529	
1530		kmemleak=	[KNL] Boot-time kmemleak enable/disable
1531				Valid arguments: on, off
1532				Default: on
1533	
1534		kmemcheck=	[X86] Boot-time kmemcheck enable/disable/one-shot mode
1535				Valid arguments: 0, 1, 2
1536				kmemcheck=0 (disabled)
1537				kmemcheck=1 (enabled)
1538				kmemcheck=2 (one-shot mode)
1539				Default: 2 (one-shot mode)
1540	
1541		kstack=N	[X86] Print N words from the kernel stack
1542				in oops dumps.
1543	
1544		kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1545				Default is 0 (don't ignore, but inject #GP)
1546	
1547		kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
1548				KVM MMU at runtime.
1549				Default is 0 (off)
1550	
1551		kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
1552				Default is 1 (enabled)
1553	
1554		kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
1555				for all guests.
1556				Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1557	
1558		kvm-intel.ept=	[KVM,Intel] Disable extended page tables
1559				(virtualized MMU) support on capable Intel chips.
1560				Default is 1 (enabled)
1561	
1562		kvm-intel.emulate_invalid_guest_state=
1563				[KVM,Intel] Enable emulation of invalid guest states
1564				Default is 0 (disabled)
1565	
1566		kvm-intel.flexpriority=
1567				[KVM,Intel] Disable FlexPriority feature (TPR shadow).
1568				Default is 1 (enabled)
1569	
1570		kvm-intel.nested=
1571				[KVM,Intel] Enable VMX nesting (nVMX).
1572				Default is 0 (disabled)
1573	
1574		kvm-intel.unrestricted_guest=
1575				[KVM,Intel] Disable unrestricted guest feature
1576				(virtualized real and unpaged mode) on capable
1577				Intel chips. Default is 1 (enabled)
1578	
1579		kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
1580				feature (tagged TLBs) on capable Intel chips.
1581				Default is 1 (enabled)
1582	
1583		l2cr=		[PPC]
1584	
1585		l3cr=		[PPC]
1586	
1587		lapic		[X86-32,APIC] Enable the local APIC even if BIOS
1588				disabled it.
1589	
1590		lapic=		[x86,APIC] "notscdeadline" Do not use TSC deadline
1591				value for LAPIC timer one-shot implementation. Default
1592				back to the programmable timer unit in the LAPIC.
1593	
1594		lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
1595				in C2 power state.
1596	
1597		libata.dma=	[LIBATA] DMA control
1598				libata.dma=0	  Disable all PATA and SATA DMA
1599				libata.dma=1	  PATA and SATA Disk DMA only
1600				libata.dma=2	  ATAPI (CDROM) DMA only
1601				libata.dma=4	  Compact Flash DMA only
1602				Combinations also work, so libata.dma=3 enables DMA
1603				for disks and CDROMs, but not CFs.
1604	
1605		libata.ignore_hpa=	[LIBATA] Ignore HPA limit
1606				libata.ignore_hpa=0	  keep BIOS limits (default)
1607				libata.ignore_hpa=1	  ignore limits, using full disk
1608	
1609		libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
1610				when set.
1611				Format: <int>
1612	
1613		libata.force=	[LIBATA] Force configurations.  The format is comma
1614				separated list of "[ID:]VAL" where ID is
1615				PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1616				matching port, link or device.  Basically, it matches
1617				the ATA ID string printed on console by libata.  If
1618				the whole ID part is omitted, the last PORT and DEVICE
1619				values are used.  If ID hasn't been specified yet, the
1620				configuration applies to all ports, links and devices.
1621	
1622				If only DEVICE is omitted, the parameter applies to
1623				the port and all links and devices behind it.  DEVICE
1624				number of 0 either selects the first device or the
1625				first fan-out link behind PMP device.  It does not
1626				select the host link.  DEVICE number of 15 selects the
1627				host link and device attached to it.
1628	
1629				The VAL specifies the configuration to force.  As long
1630				as there's no ambiguity shortcut notation is allowed.
1631				For example, both 1.5 and 1.5G would work for 1.5Gbps.
1632				The following configurations can be forced.
1633	
1634				* Cable type: 40c, 80c, short40c, unk, ign or sata.
1635				  Any ID with matching PORT is used.
1636	
1637				* SATA link speed limit: 1.5Gbps or 3.0Gbps.
1638	
1639				* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1640				  udma[/][16,25,33,44,66,100,133] notation is also
1641				  allowed.
1642	
1643				* [no]ncq: Turn on or off NCQ.
1644	
1645				* nohrst, nosrst, norst: suppress hard, soft
1646	                          and both resets.
1647	
1648				* rstonce: only attempt one reset during
1649				  hot-unplug link recovery
1650	
1651				* dump_id: dump IDENTIFY data.
1652	
1653				* atapi_dmadir: Enable ATAPI DMADIR bridge support
1654	
1655				* disable: Disable this device.
1656	
1657				If there are multiple matching configurations changing
1658				the same attribute, the last one is used.
1659	
1660		memblock=debug	[KNL] Enable memblock debug messages.
1661	
1662		load_ramdisk=	[RAM] List of ramdisks to load from floppy
1663				See Documentation/blockdev/ramdisk.txt.
1664	
1665		lockd.nlm_grace_period=P  [NFS] Assign grace period.
1666				Format: <integer>
1667	
1668		lockd.nlm_tcpport=N	[NFS] Assign TCP port.
1669				Format: <integer>
1670	
1671		lockd.nlm_timeout=T	[NFS] Assign timeout value.
1672				Format: <integer>
1673	
1674		lockd.nlm_udpport=M	[NFS] Assign UDP port.
1675				Format: <integer>
1676	
1677		logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
1678				Format: <irq>
1679	
1680		loglevel=	All Kernel Messages with a loglevel smaller than the
1681				console loglevel will be printed to the console. It can
1682				also be changed with klogd or other programs. The
1683				loglevels are defined as follows:
1684	
1685				0 (KERN_EMERG)		system is unusable
1686				1 (KERN_ALERT)		action must be taken immediately
1687				2 (KERN_CRIT)		critical conditions
1688				3 (KERN_ERR)		error conditions
1689				4 (KERN_WARNING)	warning conditions
1690				5 (KERN_NOTICE)		normal but significant condition
1691				6 (KERN_INFO)		informational
1692				7 (KERN_DEBUG)		debug-level messages
1693	
1694		log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
1695				in bytes.  n must be a power of two.  The default
1696				size is set in the kernel config file.
1697	
1698		logo.nologo	[FB] Disables display of the built-in Linux logo.
1699				This may be used to provide more screen space for
1700				kernel log messages and is useful when debugging
1701				kernel boot problems.
1702	
1703		lp=0		[LP]	Specify parallel ports to use, e.g,
1704		lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
1705		lp=reset		first parallel port). 'lp=0' disables the
1706		lp=auto			printer driver. 'lp=reset' (which can be
1707					specified in addition to the ports) causes
1708					attached printers to be reset. Using
1709					lp=port1,port2,... specifies the parallel ports
1710					to associate lp devices with, starting with
1711					lp0. A port specification may be 'none' to skip
1712					that lp device, or a parport name such as
1713					'parport0'. Specifying 'lp=auto' instead of a
1714					port specification list means that device IDs
1715					from each port should be examined, to see if
1716					an IEEE 1284-compliant printer is attached; if
1717					so, the driver will manage that printer.
1718					See also header of drivers/char/lp.c.
1719	
1720		lpj=n		[KNL]
1721				Sets loops_per_jiffy to given constant, thus avoiding
1722				time-consuming boot-time autodetection (up to 250 ms per
1723				CPU). 0 enables autodetection (default). To determine
1724				the correct value for your kernel, boot with normal
1725				autodetection and see what value is printed. Note that
1726				on SMP systems the preset will be applied to all CPUs,
1727				which is likely to cause problems if your CPUs need
1728				significantly divergent settings. An incorrect value
1729				will cause delays in the kernel to be wrong, leading to
1730				unpredictable I/O errors and other breakage. Although
1731				unlikely, in the extreme case this might damage your
1732				hardware.
1733	
1734		ltpc=		[NET]
1735				Format: <io>,<irq>,<dma>
1736	
1737		machvec=	[IA-64] Force the use of a particular machine-vector
1738				(machvec) in a generic kernel.
1739				Example: machvec=hpzx1_swiotlb
1740	
1741		machtype=	[Loongson] Share the same kernel image file between different
1742				 yeeloong laptop.
1743				Example: machtype=lemote-yeeloong-2f-7inch
1744	
1745		max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
1746				than or equal to this physical address is ignored.
1747	
1748		maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
1749				should make use of.  maxcpus=n : n >= 0 limits the
1750				kernel to using 'n' processors.  n=0 is a special case,
1751				it is equivalent to "nosmp", which also disables
1752				the IO APIC.
1753	
1754		max_loop=	[LOOP] The number of loop block devices that get
1755		(loop.max_loop)	unconditionally pre-created at init time. The default
1756				number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1757				of statically allocating a predefined number, loop
1758				devices can be requested on-demand with the
1759				/dev/loop-control interface.
1760	
1761		mce		[X86-32] Machine Check Exception
1762	
1763		mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
1764	
1765		md=		[HW] RAID subsystems devices and level
1766				See Documentation/md.txt.
1767	
1768		mdacon=		[MDA]
1769				Format: <first>,<last>
1770				Specifies range of consoles to be captured by the MDA.
1771	
1772		mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
1773				Amount of memory to be used when the kernel is not able
1774				to see the whole system memory or for test.
1775				[X86] Work as limiting max address. Use together
1776				with memmap= to avoid physical address space collisions.
1777				Without memmap= PCI devices could be placed at addresses
1778				belonging to unused RAM.
1779	
1780		mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
1781				memory.
1782	
1783		memchunk=nn[KMG]
1784				[KNL,SH] Allow user to override the default size for
1785				per-device physically contiguous DMA buffers.
1786	
1787		memmap=exactmap	[KNL,X86] Enable setting of an exact
1788				E820 memory map, as specified by the user.
1789				Such memmap=exactmap lines can be constructed based on
1790				BIOS output or other requirements. See the memmap=nn@ss
1791				option description.
1792	
1793		memmap=nn[KMG]@ss[KMG]
1794				[KNL] Force usage of a specific region of memory.
1795				Region of memory to be used is from ss to ss+nn.
1796	
1797		memmap=nn[KMG]#ss[KMG]
1798				[KNL,ACPI] Mark specific memory as ACPI data.
1799				Region of memory to be marked is from ss to ss+nn.
1800	
1801		memmap=nn[KMG]$ss[KMG]
1802				[KNL,ACPI] Mark specific memory as reserved.
1803				Region of memory to be reserved is from ss to ss+nn.
1804				Example: Exclude memory from 0x18690000-0x1869ffff
1805				         memmap=64K$0x18690000
1806				         or
1807				         memmap=0x10000$0x18690000
1808	
1809		memory_corruption_check=0/1 [X86]
1810				Some BIOSes seem to corrupt the first 64k of
1811				memory when doing things like suspend/resume.
1812				Setting this option will scan the memory
1813				looking for corruption.  Enabling this will
1814				both detect corruption and prevent the kernel
1815				from using the memory being corrupted.
1816				However, its intended as a diagnostic tool; if
1817				repeatable BIOS-originated corruption always
1818				affects the same memory, you can use memmap=
1819				to prevent the kernel from using that memory.
1820	
1821		memory_corruption_check_size=size [X86]
1822				By default it checks for corruption in the low
1823				64k, making this memory unavailable for normal
1824				use.  Use this parameter to scan for
1825				corruption in more or less memory.
1826	
1827		memory_corruption_check_period=seconds [X86]
1828				By default it checks for corruption every 60
1829				seconds.  Use this parameter to check at some
1830				other rate.  0 disables periodic checking.
1831	
1832		memtest=	[KNL,X86] Enable memtest
1833				Format: <integer>
1834				default : 0 <disable>
1835				Specifies the number of memtest passes to be
1836				performed. Each pass selects another test
1837				pattern from a given set of patterns. Memtest
1838				fills the memory with this pattern, validates
1839				memory contents and reserves bad memory
1840				regions that are detected.
1841	
1842		meye.*=		[HW] Set MotionEye Camera parameters
1843				See Documentation/video4linux/meye.txt.
1844	
1845		mfgpt_irq=	[IA-32] Specify the IRQ to use for the
1846				Multi-Function General Purpose Timers on AMD Geode
1847				platforms.
1848	
1849		mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
1850				the BIOS has incorrectly applied a workaround. TinyBIOS
1851				version 0.98 is known to be affected, 0.99 fixes the
1852				problem by letting the user disable the workaround.
1853	
1854		mga=		[HW,DRM]
1855	
1856		min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
1857				physical address is ignored.
1858	
1859		mini2440=	[ARM,HW,KNL]
1860				Format:[0..2][b][c][t]
1861				Default: "0tb"
1862				MINI2440 configuration specification:
1863				0 - The attached screen is the 3.5" TFT
1864				1 - The attached screen is the 7" TFT
1865				2 - The VGA Shield is attached (1024x768)
1866				Leaving out the screen size parameter will not load
1867				the TFT driver, and the framebuffer will be left
1868				unconfigured.
1869				b - Enable backlight. The TFT backlight pin will be
1870				linked to the kernel VESA blanking code and a GPIO
1871				LED. This parameter is not necessary when using the
1872				VGA shield.
1873				c - Enable the s3c camera interface.
1874				t - Reserved for enabling touchscreen support. The
1875				touchscreen support is not enabled in the mainstream
1876				kernel as of 2.6.30, a preliminary port can be found
1877				in the "bleeding edge" mini2440 support kernel at
1878				http://repo.or.cz/w/linux-2.6/mini2440.git
1879	
1880		mminit_loglevel=
1881				[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1882				parameter allows control of the logging verbosity for
1883				the additional memory initialisation checks. A value
1884				of 0 disables mminit logging and a level of 4 will
1885				log everything. Information is printed at KERN_DEBUG
1886				so loglevel=8 may also need to be specified.
1887	
1888		module.sig_enforce
1889				[KNL] When CONFIG_MODULE_SIG is set, this means that
1890				modules without (valid) signatures will fail to load.
1891				Note that if CONFIG_MODULE_SIG_FORCE is set, that
1892				is always true, so this option does nothing.
1893	
1894		mousedev.tap_time=
1895				[MOUSE] Maximum time between finger touching and
1896				leaving touchpad surface for touch to be considered
1897				a tap and be reported as a left button click (for
1898				touchpads working in absolute mode only).
1899				Format: <msecs>
1900		mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
1901				reporting absolute coordinates, such as tablets
1902		mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
1903				reporting absolute coordinates, such as tablets
1904	
1905		movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
1906				is similar to kernelcore except it specifies the
1907				amount of memory used for migratable allocations.
1908				If both kernelcore and movablecore is specified,
1909				then kernelcore will be at *least* the specified
1910				value but may be more. If movablecore on its own
1911				is specified, the administrator must be careful
1912				that the amount of memory usable for all allocations
1913				is not too small.
1914	
1915		movable_node	[KNL,X86] Boot-time switch to enable the effects
1916				of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1917	
1918		MTD_Partition=	[MTD]
1919				Format: <name>,<region-number>,<size>,<offset>
1920	
1921		MTD_Region=	[MTD] Format:
1922				<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1923	
1924		mtdparts=	[MTD]
1925				See drivers/mtd/cmdlinepart.c.
1926	
1927		multitce=off	[PPC]  This parameter disables the use of the pSeries
1928				firmware feature for updating multiple TCE entries
1929				at a time.
1930	
1931		onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
1932	
1933				Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1934	
1935				boundary - index of last SLC block on Flex-OneNAND.
1936					   The remaining blocks are configured as MLC blocks.
1937				lock	 - Configure if Flex-OneNAND boundary should be locked.
1938					   Once locked, the boundary cannot be changed.
1939					   1 indicates lock status, 0 indicates unlock status.
1940	
1941		mtdset=		[ARM]
1942				ARM/S3C2412 JIVE boot control
1943	
1944				See arch/arm/mach-s3c2412/mach-jive.c
1945	
1946		mtouchusb.raw_coordinates=
1947				[HW] Make the MicroTouch USB driver use raw coordinates
1948				('y', default) or cooked coordinates ('n')
1949	
1950		mtrr_chunk_size=nn[KMG] [X86]
1951				used for mtrr cleanup. It is largest continuous chunk
1952				that could hold holes aka. UC entries.
1953	
1954		mtrr_gran_size=nn[KMG] [X86]
1955				Used for mtrr cleanup. It is granularity of mtrr block.
1956				Default is 1.
1957				Large value could prevent small alignment from
1958				using up MTRRs.
1959	
1960		mtrr_spare_reg_nr=n [X86]
1961				Format: <integer>
1962				Range: 0,7 : spare reg number
1963				Default : 1
1964				Used for mtrr cleanup. It is spare mtrr entries number.
1965				Set to 2 or more if your graphical card needs more.
1966	
1967		n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
1968	
1969		netdev=		[NET] Network devices parameters
1970				Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1971				Note that mem_start is often overloaded to mean
1972				something different and driver-specific.
1973				This usage is only documented in each driver source
1974				file if at all.
1975	
1976		nf_conntrack.acct=
1977				[NETFILTER] Enable connection tracking flow accounting
1978				0 to disable accounting
1979				1 to enable accounting
1980				Default value is 0.
1981	
1982		nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
1983				See Documentation/filesystems/nfs/nfsroot.txt.
1984	
1985		nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
1986				See Documentation/filesystems/nfs/nfsroot.txt.
1987	
1988		nfsrootdebug	[NFS] enable nfsroot debugging messages.
1989				See Documentation/filesystems/nfs/nfsroot.txt.
1990	
1991		nfs.callback_tcpport=
1992				[NFS] set the TCP port on which the NFSv4 callback
1993				channel should listen.
1994	
1995		nfs.cache_getent=
1996				[NFS] sets the pathname to the program which is used
1997				to update the NFS client cache entries.
1998	
1999		nfs.cache_getent_timeout=
2000				[NFS] sets the timeout after which an attempt to
2001				update a cache entry is deemed to have failed.
2002	
2003		nfs.idmap_cache_timeout=
2004				[NFS] set the maximum lifetime for idmapper cache
2005				entries.
2006	
2007		nfs.enable_ino64=
2008				[NFS] enable 64-bit inode numbers.
2009				If zero, the NFS client will fake up a 32-bit inode
2010				number for the readdir() and stat() syscalls instead
2011				of returning the full 64-bit number.
2012				The default is to return 64-bit inode numbers.
2013	
2014		nfs.max_session_slots=
2015				[NFSv4.1] Sets the maximum number of session slots
2016				the client will attempt to negotiate with the server.
2017				This limits the number of simultaneous RPC requests
2018				that the client can send to the NFSv4.1 server.
2019				Note that there is little point in setting this
2020				value higher than the max_tcp_slot_table_limit.
2021	
2022		nfs.nfs4_disable_idmapping=
2023				[NFSv4] When set to the default of '1', this option
2024				ensures that both the RPC level authentication
2025				scheme and the NFS level operations agree to use
2026				numeric uids/gids if the mount is using the
2027				'sec=sys' security flavour. In effect it is
2028				disabling idmapping, which can make migration from
2029				legacy NFSv2/v3 systems to NFSv4 easier.
2030				Servers that do not support this mode of operation
2031				will be autodetected by the client, and it will fall
2032				back to using the idmapper.
2033				To turn off this behaviour, set the value to '0'.
2034		nfs.nfs4_unique_id=
2035				[NFS4] Specify an additional fixed unique ident-
2036				ification string that NFSv4 clients can insert into
2037				their nfs_client_id4 string.  This is typically a
2038				UUID that is generated at system install time.
2039	
2040		nfs.send_implementation_id =
2041				[NFSv4.1] Send client implementation identification
2042				information in exchange_id requests.
2043				If zero, no implementation identification information
2044				will be sent.
2045				The default is to send the implementation identification
2046				information.
2047		
2048		nfs.recover_lost_locks =
2049				[NFSv4] Attempt to recover locks that were lost due
2050				to a lease timeout on the server. Please note that
2051				doing this risks data corruption, since there are
2052				no guarantees that the file will remain unchanged
2053				after the locks are lost.
2054				If you want to enable the kernel legacy behaviour of
2055				attempting to recover these locks, then set this
2056				parameter to '1'.
2057				The default parameter value of '0' causes the kernel
2058				not to attempt recovery of lost locks.
2059	
2060		nfsd.nfs4_disable_idmapping=
2061				[NFSv4] When set to the default of '1', the NFSv4
2062				server will return only numeric uids and gids to
2063				clients using auth_sys, and will accept numeric uids
2064				and gids from such clients.  This is intended to ease
2065				migration from NFSv2/v3.
2066	
2067		objlayoutdriver.osd_login_prog=
2068				[NFS] [OBJLAYOUT] sets the pathname to the program which
2069				is used to automatically discover and login into new
2070				osd-targets. Please see:
2071				Documentation/filesystems/pnfs.txt for more explanations
2072	
2073		nmi_debug=	[KNL,AVR32,SH] Specify one or more actions to take
2074				when a NMI is triggered.
2075				Format: [state][,regs][,debounce][,die]
2076	
2077		nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
2078				Format: [panic,][nopanic,][num]
2079				Valid num: 0
2080				0 - turn nmi_watchdog off
2081				When panic is specified, panic when an NMI watchdog
2082				timeout occurs (or 'nopanic' to override the opposite
2083				default).
2084				This is useful when you use a panic=... timeout and
2085				need the box quickly up again.
2086	
2087		netpoll.carrier_timeout=
2088				[NET] Specifies amount of time (in seconds) that
2089				netpoll should wait for a carrier. By default netpoll
2090				waits 4 seconds.
2091	
2092		no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
2093				emulation library even if a 387 maths coprocessor
2094				is present.
2095	
2096		no_console_suspend
2097				[HW] Never suspend the console
2098				Disable suspending of consoles during suspend and
2099				hibernate operations.  Once disabled, debugging
2100				messages can reach various consoles while the rest
2101				of the system is being put to sleep (ie, while
2102				debugging driver suspend/resume hooks).  This may
2103				not work reliably with all consoles, but is known
2104				to work with serial and VGA consoles.
2105				To facilitate more flexible debugging, we also add
2106				console_suspend, a printk module parameter to control
2107				it. Users could use console_suspend (usually
2108				/sys/module/printk/parameters/console_suspend) to
2109				turn on/off it dynamically.
2110	
2111		noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
2112				caches in the slab allocator.  Saves per-node memory,
2113				but will impact performance.
2114	
2115		noalign		[KNL,ARM]
2116	
2117		noapic		[SMP,APIC] Tells the kernel to not make use of any
2118				IOAPICs that may be present in the system.
2119	
2120		noautogroup	Disable scheduler automatic task group creation.
2121	
2122		nobats		[PPC] Do not use BATs for mapping kernel lowmem
2123				on "Classic" PPC cores.
2124	
2125		nocache		[ARM]
2126	
2127		noclflush	[BUGS=X86] Don't use the CLFLUSH instruction
2128	
2129		nodelayacct	[KNL] Disable per-task delay accounting
2130	
2131		nodisconnect	[HW,SCSI,M68K] Disables SCSI disconnects.
2132	
2133		nodsp		[SH] Disable hardware DSP at boot time.
2134	
2135		noefi		[X86] Disable EFI runtime services support.
2136	
2137		noexec		[IA-64]
2138	
2139		noexec		[X86]
2140				On X86-32 available only on PAE configured kernels.
2141				noexec=on: enable non-executable mappings (default)
2142				noexec=off: disable non-executable mappings
2143	
2144		nosmap		[X86]
2145				Disable SMAP (Supervisor Mode Access Prevention)
2146				even if it is supported by processor.
2147	
2148		nosmep		[X86]
2149				Disable SMEP (Supervisor Mode Execution Prevention)
2150				even if it is supported by processor.
2151	
2152		noexec32	[X86-64]
2153				This affects only 32-bit executables.
2154				noexec32=on: enable non-executable mappings (default)
2155					read doesn't imply executable mappings
2156				noexec32=off: disable non-executable mappings
2157					read implies executable mappings
2158	
2159		nofpu		[SH] Disable hardware FPU at boot time.
2160	
2161		nofxsr		[BUGS=X86-32] Disables x86 floating point extended
2162				register save and restore. The kernel will only save
2163				legacy floating-point registers on task switch.
2164	
2165		noxsave		[BUGS=X86] Disables x86 extended register state save
2166				and restore using xsave. The kernel will fallback to
2167				enabling legacy floating-point and sse state.
2168	
2169		eagerfpu=	[X86]
2170				on	enable eager fpu restore
2171				off	disable eager fpu restore
2172				auto	selects the default scheme, which automatically
2173					enables eagerfpu restore for xsaveopt.
2174	
2175		nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2176				wfi(ARM) instruction doesn't work correctly and not to
2177				use it. This is also useful when using JTAG debugger.
2178	
2179		no_file_caps	Tells the kernel not to honor file capabilities.  The
2180				only way then for a file to be executed with privilege
2181				is to be setuid root or executed by root.
2182	
2183		nohalt		[IA-64] Tells the kernel not to use the power saving
2184				function PAL_HALT_LIGHT when idle. This increases
2185				power-consumption. On the positive side, it reduces
2186				interrupt wake-up latency, which may improve performance
2187				in certain environments such as networked servers or
2188				real-time systems.
2189	
2190		nohibernate	[HIBERNATION] Disable hibernation and resume.
2191	
2192		nohz=		[KNL] Boottime enable/disable dynamic ticks
2193				Valid arguments: on, off
2194				Default: on
2195	
2196		nohz_full=	[KNL,BOOT]
2197				In kernels built with CONFIG_NO_HZ_FULL=y, set
2198				the specified list of CPUs whose tick will be stopped
2199				whenever possible. The boot CPU will be forced outside
2200				the range to maintain the timekeeping.
2201				The CPUs in this range must also be included in the
2202				rcu_nocbs= set.
2203	
2204		noiotrap	[SH] Disables trapped I/O port accesses.
2205	
2206		noirqdebug	[X86-32] Disables the code which attempts to detect and
2207				disable unhandled interrupt sources.
2208	
2209		no_timer_check	[X86,APIC] Disables the code which tests for
2210				broken timer IRQ sources.
2211	
2212		noisapnp	[ISAPNP] Disables ISA PnP code.
2213	
2214		noinitrd	[RAM] Tells the kernel not to load any configured
2215				initial RAM disk.
2216	
2217		nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
2218				remapping.
2219				[Deprecated - use intremap=off]
2220	
2221		nointroute	[IA-64]
2222	
2223		nojitter	[IA-64] Disables jitter checking for ITC timers.
2224	
2225		no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
2226	
2227		no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
2228				fault handling.
2229	
2230		no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
2231				steal time is computed, but won't influence scheduler
2232				behaviour
2233	
2234		nolapic		[X86-32,APIC] Do not enable or use the local APIC.
2235	
2236		nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
2237	
2238		noltlbs		[PPC] Do not use large page/tlb entries for kernel
2239				lowmem mapping on PPC40x.
2240	
2241		nomca		[IA-64] Disable machine check abort handling
2242	
2243		nomce		[X86-32] Machine Check Exception
2244	
2245		nomfgpt		[X86-32] Disable Multi-Function General Purpose
2246				Timer usage (for AMD Geode machines).
2247	
2248		nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
2249				shutdown the other cpus.  Instead use the REBOOT_VECTOR
2250				irq.
2251	
2252		nomodule	Disable module load
2253	
2254		nopat		[X86] Disable PAT (page attribute table extension of
2255				pagetables) support.
2256	
2257		norandmaps	Don't use address space randomization.  Equivalent to
2258				echo 0 > /proc/sys/kernel/randomize_va_space
2259	
2260		noreplace-paravirt	[X86,IA-64,PV_OPS] Don't patch paravirt_ops
2261	
2262		noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
2263				with UP alternatives
2264	
2265		nordrand	[X86] Disable kernel use of the RDRAND and
2266				RDSEED instructions even if they are supported
2267				by the processor.  RDRAND and RDSEED are still
2268				available to user space applications.
2269	
2270		noresume	[SWSUSP] Disables resume and restores original swap
2271				space.
2272	
2273		no-scroll	[VGA] Disables scrollback.
2274				This is required for the Braillex ib80-piezo Braille
2275				reader made by F.H. Papenmeier (Germany).
2276	
2277		nosbagart	[IA-64]
2278	
2279		nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2280	
2281		nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
2282				and disable the IO APIC.  legacy for "maxcpus=0".
2283	
2284		nosoftlockup	[KNL] Disable the soft-lockup detector.
2285	
2286		nosync		[HW,M68K] Disables sync negotiation for all devices.
2287	
2288		notsc		[BUGS=X86-32] Disable Time Stamp Counter
2289	
2290		nousb		[USB] Disable the USB subsystem
2291	
2292		nowatchdog	[KNL] Disable the lockup detector (NMI watchdog).
2293	
2294		nowb		[ARM]
2295	
2296		nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
2297	
2298		cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
2299				CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2300				Some features depend on CPU0. Known dependencies are:
2301				1. Resume from suspend/hibernate depends on CPU0.
2302				Suspend/hibernate will fail if CPU0 is offline and you
2303				need to online CPU0 before suspend/hibernate.
2304				2. PIC interrupts also depend on CPU0. CPU0 can't be
2305				removed if a PIC interrupt is detected.
2306				It's said poweroff/reboot may depend on CPU0 on some
2307				machines although I haven't seen such issues so far
2308				after CPU0 is offline on a few tested machines.
2309				If the dependencies are under your control, you can
2310				turn on cpu0_hotplug.
2311	
2312		nptcg=		[IA-64] Override max number of concurrent global TLB
2313				purges which is reported from either PAL_VM_SUMMARY or
2314				SAL PALO.
2315	
2316		nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
2317				could support.  nr_cpus=n : n >= 1 limits the kernel to
2318				supporting 'n' processors. Later in runtime you can not
2319				use hotplug cpu feature to put more cpu back to online.
2320				just like you compile the kernel NR_CPUS=n
2321	
2322		nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
2323	
2324		numa_balancing=	[KNL,X86] Enable or disable automatic NUMA balancing.
2325				Allowed values are enable and disable
2326	
2327		numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2328				one of ['zone', 'node', 'default'] can be specified
2329				This can be set from sysctl after boot.
2330				See Documentation/sysctl/vm.txt for details.
2331	
2332		ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
2333				See Documentation/debugging-via-ohci1394.txt for more
2334				info.
2335	
2336		olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2337				Rather than timing out after 20 ms if an EC
2338				command is not properly ACKed, override the length
2339				of the timeout.  We have interrupts disabled while
2340				waiting for the ACK, so if this is set too high
2341				interrupts *may* be lost!
2342	
2343		omap_mux=	[OMAP] Override bootloader pin multiplexing.
2344				Format: <mux_mode0.mode_name=value>...
2345				For example, to override I2C bus2:
2346				omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2347	
2348		oprofile.timer=	[HW]
2349				Use timer interrupt instead of performance counters
2350	
2351		oprofile.cpu_type=	Force an oprofile cpu type
2352				This might be useful if you have an older oprofile
2353				userland or if you want common events.
2354				Format: { arch_perfmon }
2355				arch_perfmon: [X86] Force use of architectural
2356					perfmon on Intel CPUs instead of the
2357					CPU specific event set.
2358				timer: [X86] Force use of architectural NMI
2359					timer mode (see also oprofile.timer
2360					for generic hr timer mode)
2361					[s390] Force legacy basic mode sampling
2362	                                (report cpu_type "timer")
2363	
2364		oops=panic	Always panic on oopses. Default is to just kill the
2365				process, but there is a small probability of
2366				deadlocking the machine.
2367				This will also cause panics on machine check exceptions.
2368				Useful together with panic=30 to trigger a reboot.
2369	
2370		OSS		[HW,OSS]
2371				See Documentation/sound/oss/oss-parameters.txt
2372	
2373		panic=		[KNL] Kernel behaviour on panic: delay <timeout>
2374				timeout > 0: seconds before rebooting
2375				timeout = 0: wait forever
2376				timeout < 0: reboot immediately
2377				Format: <timeout>
2378	
2379		crash_kexec_post_notifiers
2380				Run kdump after running panic-notifiers and dumping
2381				kmsg. This only for the users who doubt kdump always
2382				succeeds in any situation.
2383				Note that this also increases risks of kdump failure,
2384				because some panic notifiers can make the crashed
2385				kernel more unstable.
2386	
2387		parkbd.port=	[HW] Parallel port number the keyboard adapter is
2388				connected to, default is 0.
2389				Format: <parport#>
2390		parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
2391				0 for XT, 1 for AT (default is AT).
2392				Format: <mode>
2393	
2394		parport=	[HW,PPT] Specify parallel ports. 0 disables.
2395				Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2396				Use 'auto' to force the driver to use any
2397				IRQ/DMA settings detected (the default is to
2398				ignore detected IRQ/DMA settings because of
2399				possible conflicts). You can specify the base
2400				address, IRQ, and DMA settings; IRQ and DMA
2401				should be numbers, or 'auto' (for using detected
2402				settings on that particular port), or 'nofifo'
2403				(to avoid using a FIFO even if it is detected).
2404				Parallel ports are assigned in the order they
2405				are specified on the command line, starting
2406				with parport0.
2407	
2408		parport_init_mode=	[HW,PPT]
2409				Configure VIA parallel port to operate in
2410				a specific mode. This is necessary on Pegasos
2411				computer where firmware has no options for setting
2412				up parallel port mode and sets it to spp.
2413				Currently this function knows 686a and 8231 chips.
2414				Format: [spp|ps2|epp|ecp|ecpepp]
2415	
2416		pause_on_oops=
2417				Halt all CPUs after the first oops has been printed for
2418				the specified number of seconds.  This is to be used if
2419				your oopses keep scrolling off the screen.
2420	
2421		pcbit=		[HW,ISDN]
2422	
2423		pcd.		[PARIDE]
2424				See header of drivers/block/paride/pcd.c.
2425				See also Documentation/blockdev/paride.txt.
2426	
2427		pci=option[,option...]	[PCI] various PCI subsystem options:
2428			earlydump	[X86] dump PCI config space before the kernel
2429				        changes anything
2430			off		[X86] don't probe for the PCI bus
2431			bios		[X86-32] force use of PCI BIOS, don't access
2432					the hardware directly. Use this if your machine
2433					has a non-standard PCI host bridge.
2434			nobios		[X86-32] disallow use of PCI BIOS, only direct
2435					hardware access methods are allowed. Use this
2436					if you experience crashes upon bootup and you
2437					suspect they are caused by the BIOS.
2438			conf1		[X86] Force use of PCI Configuration
2439					Mechanism 1.
2440			conf2		[X86] Force use of PCI Configuration
2441					Mechanism 2.
2442			noaer		[PCIE] If the PCIEAER kernel config parameter is
2443					enabled, this kernel boot option can be used to
2444					disable the use of PCIE advanced error reporting.
2445			nodomains	[PCI] Disable support for multiple PCI
2446					root domains (aka PCI segments, in ACPI-speak).
2447			nommconf	[X86] Disable use of MMCONFIG for PCI
2448					Configuration
2449			check_enable_amd_mmconf [X86] check for and enable
2450					properly configured MMIO access to PCI
2451					config space on AMD family 10h CPU
2452			nomsi		[MSI] If the PCI_MSI kernel config parameter is
2453					enabled, this kernel boot option can be used to
2454					disable the use of MSI interrupts system-wide.
2455			noioapicquirk	[APIC] Disable all boot interrupt quirks.
2456					Safety option to keep boot IRQs enabled. This
2457					should never be necessary.
2458			ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
2459					primary IO-APIC for bridges that cannot disable
2460					boot IRQs. This fixes a source of spurious IRQs
2461					when the system masks IRQs.
2462			noioapicreroute	[APIC] Disable workaround that uses the
2463					boot IRQ equivalent of an IRQ that connects to
2464					a chipset where boot IRQs cannot be disabled.
2465					The opposite of ioapicreroute.
2466			biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
2467					routing table. These calls are known to be buggy
2468					on several machines and they hang the machine
2469					when used, but on other computers it's the only
2470					way to get the interrupt routing table. Try
2471					this option if the kernel is unable to allocate
2472					IRQs or discover secondary PCI buses on your
2473					motherboard.
2474			rom		[X86] Assign address space to expansion ROMs.
2475					Use with caution as certain devices share
2476					address decoders between ROMs and other
2477					resources.
2478			norom		[X86] Do not assign address space to
2479					expansion ROMs that do not already have
2480					BIOS assigned address ranges.
2481			nobar		[X86] Do not assign address space to the
2482					BARs that weren't assigned by the BIOS.
2483			irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
2484					assigned automatically to PCI devices. You can
2485					make the kernel exclude IRQs of your ISA cards
2486					this way.
2487			pirqaddr=0xAAAAA	[X86] Specify the physical address
2488					of the PIRQ table (normally generated
2489					by the BIOS) if it is outside the
2490					F0000h-100000h range.
2491			lastbus=N	[X86] Scan all buses thru bus #N. Can be
2492					useful if the kernel is unable to find your
2493					secondary buses and you want to tell it
2494					explicitly which ones they are.
2495			assign-busses	[X86] Always assign all PCI bus
2496					numbers ourselves, overriding
2497					whatever the firmware may have done.
2498			usepirqmask	[X86] Honor the possible IRQ mask stored
2499					in the BIOS $PIR table. This is needed on
2500					some systems with broken BIOSes, notably
2501					some HP Pavilion N5400 and Omnibook XE3
2502					notebooks. This will have no effect if ACPI
2503					IRQ routing is enabled.
2504			noacpi		[X86] Do not use ACPI for IRQ routing
2505					or for PCI scanning.
2506			use_crs		[X86] Use PCI host bridge window information
2507					from ACPI.  On BIOSes from 2008 or later, this
2508					is enabled by default.  If you need to use this,
2509					please report a bug.
2510			nocrs		[X86] Ignore PCI host bridge windows from ACPI.
2511				        If you need to use this, please report a bug.
2512			routeirq	Do IRQ routing for all PCI devices.
2513					This is normally done in pci_enable_device(),
2514					so this option is a temporary workaround
2515					for broken drivers that don't call it.
2516			skip_isa_align	[X86] do not align io start addr, so can
2517					handle more pci cards
2518			firmware	[ARM] Do not re-enumerate the bus but instead
2519					just use the configuration from the
2520					bootloader. This is currently used on
2521					IXP2000 systems where the bus has to be
2522					configured a certain way for adjunct CPUs.
2523			noearly		[X86] Don't do any early type 1 scanning.
2524					This might help on some broken boards which
2525					machine check when some devices' config space
2526					is read. But various workarounds are disabled
2527					and some IOMMU drivers will not work.
2528			bfsort		Sort PCI devices into breadth-first order.
2529					This sorting is done to get a device
2530					order compatible with older (<= 2.4) kernels.
2531			nobfsort	Don't sort PCI devices into breadth-first order.
2532			pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
2533					tuning and use the BIOS-configured MPS defaults.
2534			pcie_bus_safe	Set every device's MPS to the largest value
2535					supported by all devices below the root complex.
2536			pcie_bus_perf	Set device MPS to the largest allowable MPS
2537					based on its parent bus. Also set MRRS (Max
2538					Read Request Size) to the largest supported
2539					value (no larger than the MPS that the device
2540					or bus can support) for best performance.
2541			pcie_bus_peer2peer	Set every device's MPS to 128B, which
2542					every device is guaranteed to support. This
2543					configuration allows peer-to-peer DMA between
2544					any pair of devices, possibly at the cost of
2545					reduced performance.  This also guarantees
2546					that hot-added devices will work.
2547			cbiosize=nn[KMG]	The fixed amount of bus space which is
2548					reserved for the CardBus bridge's IO window.
2549					The default value is 256 bytes.
2550			cbmemsize=nn[KMG]	The fixed amount of bus space which is
2551					reserved for the CardBus bridge's memory
2552					window. The default value is 64 megabytes.
2553			resource_alignment=
2554					Format:
2555					[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2556					Specifies alignment and device to reassign
2557					aligned memory resources.
2558					If <order of align> is not specified,
2559					PAGE_SIZE is used as alignment.
2560					PCI-PCI bridge can be specified, if resource
2561					windows need to be expanded.
2562			ecrc=		Enable/disable PCIe ECRC (transaction layer
2563					end-to-end CRC checking).
2564					bios: Use BIOS/firmware settings. This is the
2565					the default.
2566					off: Turn ECRC off
2567					on: Turn ECRC on.
2568			hpiosize=nn[KMG]	The fixed amount of bus space which is
2569					reserved for hotplug bridge's IO window.
2570					Default size is 256 bytes.
2571			hpmemsize=nn[KMG]	The fixed amount of bus space which is
2572					reserved for hotplug bridge's memory window.
2573					Default size is 2 megabytes.
2574			realloc=	Enable/disable reallocating PCI bridge resources
2575					if allocations done by BIOS are too small to
2576					accommodate resources required by all child
2577					devices.
2578					off: Turn realloc off
2579					on: Turn realloc on
2580			realloc		same as realloc=on
2581			noari		do not use PCIe ARI.
2582			pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
2583					only look for one device below a PCIe downstream
2584					port.
2585	
2586		pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
2587				Management.
2588			off	Disable ASPM.
2589			force	Enable ASPM even on devices that claim not to support it.
2590				WARNING: Forcing ASPM on may cause system lockups.
2591	
2592		pcie_hp=	[PCIE] PCI Express Hotplug driver options:
2593			nomsi	Do not use MSI for PCI Express Native Hotplug (this
2594				makes all PCIe ports use INTx for hotplug services).
2595	
2596		pcie_ports=	[PCIE] PCIe ports handling:
2597			auto	Ask the BIOS whether or not to use native PCIe services
2598				associated with PCIe ports (PME, hot-plug, AER).  Use
2599				them only if that is allowed by the BIOS.
2600			native	Use native PCIe services associated with PCIe ports
2601				unconditionally.
2602			compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2603				ports driver.
2604	
2605		pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
2606			nomsi	Do not use MSI for native PCIe PME signaling (this makes
2607				all PCIe root ports use INTx for all services).
2608	
2609		pcmv=		[HW,PCMCIA] BadgePAD 4
2610	
2611		pd_ignore_unused
2612				[PM]
2613				Keep all power-domains already enabled by bootloader on,
2614				even if no driver has claimed them. This is useful
2615				for debug and development, but should not be
2616				needed on a platform with proper driver support.
2617	
2618		pd.		[PARIDE]
2619				See Documentation/blockdev/paride.txt.
2620	
2621		pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
2622				boot time.
2623				Format: { 0 | 1 }
2624				See arch/parisc/kernel/pdc_chassis.c
2625	
2626		percpu_alloc=	Select which percpu first chunk allocator to use.
2627				Currently supported values are "embed" and "page".
2628				Archs may support subset or none of the	selections.
2629				See comments in mm/percpu.c for details on each
2630				allocator.  This parameter is primarily	for debugging
2631				and performance comparison.
2632	
2633		pf.		[PARIDE]
2634				See Documentation/blockdev/paride.txt.
2635	
2636		pg.		[PARIDE]
2637				See Documentation/blockdev/paride.txt.
2638	
2639		pirq=		[SMP,APIC] Manual mp-table setup
2640				See Documentation/x86/i386/IO-APIC.txt.
2641	
2642		plip=		[PPT,NET] Parallel port network link
2643				Format: { parport<nr> | timid | 0 }
2644				See also Documentation/parport.txt.
2645	
2646		pmtmr=		[X86] Manual setup of pmtmr I/O Port.
2647				Override pmtimer IOPort with a hex value.
2648				e.g. pmtmr=0x508
2649	
2650		pnp.debug=1	[PNP]
2651				Enable PNP debug messages (depends on the
2652				CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
2653				via /sys/module/pnp/parameters/debug.  We always show
2654				current resource usage; turning this on also shows
2655				possible settings and some assignment information.
2656	
2657		pnpacpi=	[ACPI]
2658				{ off }
2659	
2660		pnpbios=	[ISAPNP]
2661				{ on | off | curr | res | no-curr | no-res }
2662	
2663		pnp_reserve_irq=
2664				[ISAPNP] Exclude IRQs for the autoconfiguration
2665	
2666		pnp_reserve_dma=
2667				[ISAPNP] Exclude DMAs for the autoconfiguration
2668	
2669		pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
2670				Ranges are in pairs (I/O port base and size).
2671	
2672		pnp_reserve_mem=
2673				[ISAPNP] Exclude memory regions for the
2674				autoconfiguration.
2675				Ranges are in pairs (memory base and size).
2676	
2677		ports=		[IP_VS_FTP] IPVS ftp helper module
2678				Default is 21.
2679				Up to 8 (IP_VS_APP_MAX_PORTS) ports
2680				may be specified.
2681				Format: <port>,<port>....
2682	
2683		print-fatal-signals=
2684				[KNL] debug: print fatal signals
2685	
2686				If enabled, warn about various signal handling
2687				related application anomalies: too many signals,
2688				too many POSIX.1 timers, fatal signals causing a
2689				coredump - etc.
2690	
2691				If you hit the warning due to signal overflow,
2692				you might want to try "ulimit -i unlimited".
2693	
2694				default: off.
2695	
2696		printk.always_kmsg_dump=
2697				Trigger kmsg_dump for cases other than kernel oops or
2698				panics
2699				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2700				default: disabled
2701	
2702		printk.time=	Show timing data prefixed to each printk message line
2703				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2704	
2705		processor.max_cstate=	[HW,ACPI]
2706				Limit processor to maximum C-state
2707				max_cstate=9 overrides any DMI blacklist limit.
2708	
2709		processor.nocst	[HW,ACPI]
2710				Ignore the _CST method to determine C-states,
2711				instead using the legacy FADT method
2712	
2713		profile=	[KNL] Enable kernel profiling via /proc/profile
2714				Format: [schedule,]<number>
2715				Param: "schedule" - profile schedule points.
2716				Param: <number> - step/bucket size as a power of 2 for
2717					statistical time based profiling.
2718				Param: "sleep" - profile D-state sleeping (millisecs).
2719					Requires CONFIG_SCHEDSTATS
2720				Param: "kvm" - profile VM exits.
2721	
2722		prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
2723				before loading.
2724				See Documentation/blockdev/ramdisk.txt.
2725	
2726		psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
2727				probe for; one of (bare|imps|exps|lifebook|any).
2728		psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
2729				per second.
2730		psmouse.resetafter=	[HW,MOUSE]
2731				Try to reset the device after so many bad packets
2732				(0 = never).
2733		psmouse.resolution=
2734				[HW,MOUSE] Set desired mouse resolution, in dpi.
2735		psmouse.smartscroll=
2736				[HW,MOUSE] Controls Logitech smartscroll autorepeat.
2737				0 = disabled, 1 = enabled (default).
2738	
2739		pstore.backend=	Specify the name of the pstore backend to use
2740	
2741		pt.		[PARIDE]
2742				See Documentation/blockdev/paride.txt.
2743	
2744		pty.legacy_count=
2745				[KNL] Number of legacy pty's. Overwrites compiled-in
2746				default number.
2747	
2748		quiet		[KNL] Disable most log messages
2749	
2750		r128=		[HW,DRM]
2751	
2752		raid=		[HW,RAID]
2753				See Documentation/md.txt.
2754	
2755		ramdisk_blocksize=	[RAM]
2756				See Documentation/blockdev/ramdisk.txt.
2757	
2758		ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
2759				See Documentation/blockdev/ramdisk.txt.
2760	
2761		rcu_nocbs=	[KNL]
2762				In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2763				the specified list of CPUs to be no-callback CPUs.
2764				Invocation of these CPUs' RCU callbacks will
2765				be offloaded to "rcuox/N" kthreads created for
2766				that purpose, where "x" is "b" for RCU-bh, "p"
2767				for RCU-preempt, and "s" for RCU-sched, and "N"
2768				is the CPU number.  This reduces OS jitter on the
2769				offloaded CPUs, which can be useful for HPC and
2770				real-time workloads.  It can also improve energy
2771				efficiency for asymmetric multiprocessors.
2772	
2773		rcu_nocb_poll	[KNL]
2774				Rather than requiring that offloaded CPUs
2775				(specified by rcu_nocbs= above) explicitly
2776				awaken the corresponding "rcuoN" kthreads,
2777				make these kthreads poll for callbacks.
2778				This improves the real-time response for the
2779				offloaded CPUs by relieving them of the need to
2780				wake up the corresponding kthread, but degrades
2781				energy efficiency by requiring that the kthreads
2782				periodically wake up to do the polling.
2783	
2784		rcutree.blimit=	[KNL]
2785				Set maximum number of finished RCU callbacks to
2786				process in one batch.
2787	
2788		rcutree.rcu_fanout_leaf= [KNL]
2789				Increase the number of CPUs assigned to each
2790				leaf rcu_node structure.  Useful for very large
2791				systems.
2792	
2793		rcutree.jiffies_till_sched_qs= [KNL]
2794				Set required age in jiffies for a
2795				given grace period before RCU starts
2796				soliciting quiescent-state help from
2797				rcu_note_context_switch().
2798	
2799		rcutree.jiffies_till_first_fqs= [KNL]
2800				Set delay from grace-period initialization to
2801				first attempt to force quiescent states.
2802				Units are jiffies, minimum value is zero,
2803				and maximum value is HZ.
2804	
2805		rcutree.jiffies_till_next_fqs= [KNL]
2806				Set delay between subsequent attempts to force
2807				quiescent states.  Units are jiffies, minimum
2808				value is one, and maximum value is HZ.
2809	
2810		rcutree.qhimark= [KNL]
2811				Set threshold of queued RCU callbacks beyond which
2812				batch limiting is disabled.
2813	
2814		rcutree.qlowmark= [KNL]
2815				Set threshold of queued RCU callbacks below which
2816				batch limiting is re-enabled.
2817	
2818		rcutree.rcu_idle_gp_delay= [KNL]
2819				Set wakeup interval for idle CPUs that have
2820				RCU callbacks (RCU_FAST_NO_HZ=y).
2821	
2822		rcutree.rcu_idle_lazy_gp_delay= [KNL]
2823				Set wakeup interval for idle CPUs that have
2824				only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2825				Lazy RCU callbacks are those which RCU can
2826				prove do nothing more than free memory.
2827	
2828		rcutorture.fqs_duration= [KNL]
2829				Set duration of force_quiescent_state bursts.
2830	
2831		rcutorture.fqs_holdoff= [KNL]
2832				Set holdoff time within force_quiescent_state bursts.
2833	
2834		rcutorture.fqs_stutter= [KNL]
2835				Set wait time between force_quiescent_state bursts.
2836	
2837		rcutorture.gp_exp= [KNL]
2838				Use expedited update-side primitives.
2839	
2840		rcutorture.gp_normal= [KNL]
2841				Use normal (non-expedited) update-side primitives.
2842				If both gp_exp and gp_normal are set, do both.
2843				If neither gp_exp nor gp_normal are set, still
2844				do both.
2845	
2846		rcutorture.n_barrier_cbs= [KNL]
2847				Set callbacks/threads for rcu_barrier() testing.
2848	
2849		rcutorture.nfakewriters= [KNL]
2850				Set number of concurrent RCU writers.  These just
2851				stress RCU, they don't participate in the actual
2852				test, hence the "fake".
2853	
2854		rcutorture.nreaders= [KNL]
2855				Set number of RCU readers.
2856	
2857		rcutorture.object_debug= [KNL]
2858				Enable debug-object double-call_rcu() testing.
2859	
2860		rcutorture.onoff_holdoff= [KNL]
2861				Set time (s) after boot for CPU-hotplug testing.
2862	
2863		rcutorture.onoff_interval= [KNL]
2864				Set time (s) between CPU-hotplug operations, or
2865				zero to disable CPU-hotplug testing.
2866	
2867		rcutorture.rcutorture_runnable= [BOOT]
2868				Start rcutorture running at boot time.
2869	
2870		rcutorture.shuffle_interval= [KNL]
2871				Set task-shuffle interval (s).  Shuffling tasks
2872				allows some CPUs to go into dyntick-idle mode
2873				during the rcutorture test.
2874	
2875		rcutorture.shutdown_secs= [KNL]
2876				Set time (s) after boot system shutdown.  This
2877				is useful for hands-off automated testing.
2878	
2879		rcutorture.stall_cpu= [KNL]
2880				Duration of CPU stall (s) to test RCU CPU stall
2881				warnings, zero to disable.
2882	
2883		rcutorture.stall_cpu_holdoff= [KNL]
2884				Time to wait (s) after boot before inducing stall.
2885	
2886		rcutorture.stat_interval= [KNL]
2887				Time (s) between statistics printk()s.
2888	
2889		rcutorture.stutter= [KNL]
2890				Time (s) to stutter testing, for example, specifying
2891				five seconds causes the test to run for five seconds,
2892				wait for five seconds, and so on.  This tests RCU's
2893				ability to transition abruptly to and from idle.
2894	
2895		rcutorture.test_boost= [KNL]
2896				Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
2897				"Maybe" means test if the RCU implementation
2898				under test support RCU priority boosting.
2899	
2900		rcutorture.test_boost_duration= [KNL]
2901				Duration (s) of each individual boost test.
2902	
2903		rcutorture.test_boost_interval= [KNL]
2904				Interval (s) between each boost test.
2905	
2906		rcutorture.test_no_idle_hz= [KNL]
2907				Test RCU's dyntick-idle handling.  See also the
2908				rcutorture.shuffle_interval parameter.
2909	
2910		rcutorture.torture_type= [KNL]
2911				Specify the RCU implementation to test.
2912	
2913		rcutorture.verbose= [KNL]
2914				Enable additional printk() statements.
2915	
2916		rcupdate.rcu_expedited= [KNL]
2917				Use expedited grace-period primitives, for
2918				example, synchronize_rcu_expedited() instead
2919				of synchronize_rcu().  This reduces latency,
2920				but can increase CPU utilization, degrade
2921				real-time latency, and degrade energy efficiency.
2922	
2923		rcupdate.rcu_cpu_stall_suppress= [KNL]
2924				Suppress RCU CPU stall warning messages.
2925	
2926		rcupdate.rcu_cpu_stall_timeout= [KNL]
2927				Set timeout for RCU CPU stall warning messages.
2928	
2929		rdinit=		[KNL]
2930				Format: <full_path>
2931				Run specified binary instead of /init from the ramdisk,
2932				used for early userspace startup. See initrd.
2933	
2934		reboot=		[KNL]
2935				Format (x86 or x86_64):
2936					[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2937					[[,]s[mp]#### \
2938					[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2939					[[,]f[orce]
2940				Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2941				      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2942				      reboot_force is either force or not specified,
2943				      reboot_cpu is s[mp]#### with #### being the processor
2944						to be used for rebooting.
2945	
2946		relax_domain_level=
2947				[KNL, SMP] Set scheduler's default relax_domain_level.
2948				See Documentation/cgroups/cpusets.txt.
2949	
2950		relative_sleep_states=
2951				[SUSPEND] Use sleep state labeling where the deepest
2952				state available other than hibernation is always "mem".
2953				Format: { "0" | "1" }
2954				0 -- Traditional sleep state labels.
2955				1 -- Relative sleep state labels.
2956	
2957		reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
2958	
2959		reservetop=	[X86-32]
2960				Format: nn[KMG]
2961				Reserves a hole at the top of the kernel virtual
2962				address space.
2963	
2964		reservelow=	[X86]
2965				Format: nn[K]
2966				Set the amount of memory to reserve for BIOS at
2967				the bottom of the address space.
2968	
2969		reset_devices	[KNL] Force drivers to reset the underlying device
2970				during initialization.
2971	
2972		resume=		[SWSUSP]
2973				Specify the partition device for software suspend
2974				Format:
2975				{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2976	
2977		resume_offset=	[SWSUSP]
2978				Specify the offset from the beginning of the partition
2979				given by "resume=" at which the swap header is located,
2980				in <PAGE_SIZE> units (needed only for swap files).
2981				See  Documentation/power/swsusp-and-swap-files.txt
2982	
2983		resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
2984				read the resume files
2985	
2986		resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
2987				Useful for devices that are detected asynchronously
2988				(e.g. USB and MMC devices).
2989	
2990		hibernate=	[HIBERNATION]
2991			noresume	Don't check if there's a hibernation image
2992					present during boot.
2993			nocompress	Don't compress/decompress hibernation images.
2994			no		Disable hibernation and resume.
2995	
2996		retain_initrd	[RAM] Keep initrd memory after extraction
2997	
2998		rhash_entries=	[KNL,NET]
2999				Set number of hash buckets for route cache
3000	
3001		ro		[KNL] Mount root device read-only on boot
3002	
3003		root=		[KNL] Root filesystem
3004				See name_to_dev_t comment in init/do_mounts.c.
3005	
3006		rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
3007				mount the root filesystem
3008	
3009		rootflags=	[KNL] Set root filesystem mount option string
3010	
3011		rootfstype=	[KNL] Set root filesystem type
3012	
3013		rootwait	[KNL] Wait (indefinitely) for root device to show up.
3014				Useful for devices that are detected asynchronously
3015				(e.g. USB and MMC devices).
3016	
3017		rproc_mem=nn[KMG][@address]
3018				[KNL,ARM,CMA] Remoteproc physical memory block.
3019				Memory area to be used by remote processor image,
3020				managed by CMA.
3021	
3022		rw		[KNL] Mount root device read-write on boot
3023	
3024		S		[KNL] Run init in single mode
3025	
3026		sa1100ir	[NET]
3027				See drivers/net/irda/sa1100_ir.c.
3028	
3029		sbni=		[NET] Granch SBNI12 leased line adapter
3030	
3031		sched_debug	[KNL] Enables verbose scheduler debug messages.
3032	
3033		skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
3034				xtime_lock contention on larger systems, and/or RCU lock
3035				contention on all systems with CONFIG_MAXSMP set.
3036				Format: { "0" | "1" }
3037				0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3038				1 -- enable.
3039				Note: increases power consumption, thus should only be
3040				enabled if running jitter sensitive (HPC/RT) workloads.
3041	
3042		security=	[SECURITY] Choose a security module to enable at boot.
3043				If this boot parameter is not specified, only the first
3044				security module asking for security registration will be
3045				loaded. An invalid security module name will be treated
3046				as if no module has been chosen.
3047	
3048		selinux=	[SELINUX] Disable or enable SELinux at boot time.
3049				Format: { "0" | "1" }
3050				See security/selinux/Kconfig help text.
3051				0 -- disable.
3052				1 -- enable.
3053				Default value is set via kernel config option.
3054				If enabled at boot time, /selinux/disable can be used
3055				later to disable prior to initial policy load.
3056	
3057		apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
3058				Format: { "0" | "1" }
3059				See security/apparmor/Kconfig help text
3060				0 -- disable.
3061				1 -- enable.
3062				Default value is set via kernel config option.
3063	
3064		serialnumber	[BUGS=X86-32]
3065	
3066		shapers=	[NET]
3067				Maximal number of shapers.
3068	
3069		show_msr=	[x86] show boot-time MSR settings
3070				Format: { <integer> }
3071				Show boot-time (BIOS-initialized) MSR settings.
3072				The parameter means the number of CPUs to show,
3073				for example 1 means boot CPU only.
3074	
3075		simeth=		[IA-64]
3076		simscsi=
3077	
3078		slram=		[HW,MTD]
3079	
3080		slab_max_order=	[MM, SLAB]
3081				Determines the maximum allowed order for slabs.
3082				A high setting may cause OOMs due to memory
3083				fragmentation.  Defaults to 1 for systems with
3084				more than 32MB of RAM, 0 otherwise.
3085	
3086		slub_debug[=options[,slabs]]	[MM, SLUB]
3087				Enabling slub_debug allows one to determine the
3088				culprit if slab objects become corrupted. Enabling
3089				slub_debug can create guard zones around objects and
3090				may poison objects when not in use. Also tracks the
3091				last alloc / free. For more information see
3092				Documentation/vm/slub.txt.
3093	
3094		slub_max_order= [MM, SLUB]
3095				Determines the maximum allowed order for slabs.
3096				A high setting may cause OOMs due to memory
3097				fragmentation. For more information see
3098				Documentation/vm/slub.txt.
3099	
3100		slub_min_objects=	[MM, SLUB]
3101				The minimum number of objects per slab. SLUB will
3102				increase the slab order up to slub_max_order to
3103				generate a sufficiently large slab able to contain
3104				the number of objects indicated. The higher the number
3105				of objects the smaller the overhead of tracking slabs
3106				and the less frequently locks need to be acquired.
3107				For more information see Documentation/vm/slub.txt.
3108	
3109		slub_min_order=	[MM, SLUB]
3110				Determines the minimum page order for slabs. Must be
3111				lower than slub_max_order.
3112				For more information see Documentation/vm/slub.txt.
3113	
3114		slub_nomerge	[MM, SLUB]
3115				Disable merging of slabs with similar size. May be
3116				necessary if there is some reason to distinguish
3117				allocs to different slabs. Debug options disable
3118				merging on their own.
3119				For more information see Documentation/vm/slub.txt.
3120	
3121		smart2=		[HW]
3122				Format: <io1>[,<io2>[,...,<io8>]]
3123	
3124		smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
3125		smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
3126		smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
3127		smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
3128		smsc-ircc2.ircc_irq=	[HW] IRQ line
3129		smsc-ircc2.ircc_dma=	[HW] DMA channel
3130		smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3131					0: Toshiba Satellite 1800 (GP data pin select)
3132					1: Fast pin select (default)
3133					2: ATC IRMode
3134	
3135		softlockup_panic=
3136				[KNL] Should the soft-lockup detector generate panics.
3137				Format: <integer>
3138	
3139		softlockup_all_cpu_backtrace=
3140				[KNL] Should the soft-lockup detector generate
3141				backtraces on all cpus.
3142				Format: <integer>
3143	
3144		sonypi.*=	[HW] Sony Programmable I/O Control Device driver
3145				See Documentation/laptops/sonypi.txt
3146	
3147		spia_io_base=	[HW,MTD]
3148		spia_fio_base=
3149		spia_pedr=
3150		spia_peddr=
3151	
3152		stacktrace	[FTRACE]
3153				Enabled the stack tracer on boot up.
3154	
3155		stacktrace_filter=[function-list]
3156				[FTRACE] Limit the functions that the stack tracer
3157				will trace at boot up. function-list is a comma separated
3158				list of functions. This list can be changed at run
3159				time by the stack_trace_filter file in the debugfs
3160				tracing directory. Note, this enables stack tracing
3161				and the stacktrace above is not needed.
3162	
3163		sti=		[PARISC,HW]
3164				Format: <num>
3165				Set the STI (builtin display/keyboard on the HP-PARISC
3166				machines) console (graphic card) which should be used
3167				as the initial boot-console.
3168				See also comment in drivers/video/console/sticore.c.
3169	
3170		sti_font=	[HW]
3171				See comment in drivers/video/console/sticore.c.
3172	
3173		stifb=		[HW]
3174				Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3175	
3176		sunrpc.min_resvport=
3177		sunrpc.max_resvport=
3178				[NFS,SUNRPC]
3179				SunRPC servers often require that client requests
3180				originate from a privileged port (i.e. a port in the
3181				range 0 < portnr < 1024).
3182				An administrator who wishes to reserve some of these
3183				ports for other uses may adjust the range that the
3184				kernel's sunrpc client considers to be privileged
3185				using these two parameters to set the minimum and
3186				maximum port values.
3187	
3188		sunrpc.pool_mode=
3189				[NFS]
3190				Control how the NFS server code allocates CPUs to
3191				service thread pools.  Depending on how many NICs
3192				you have and where their interrupts are bound, this
3193				option will affect which CPUs will do NFS serving.
3194				Note: this parameter cannot be changed while the
3195				NFS server is running.
3196	
3197				auto	    the server chooses an appropriate mode
3198					    automatically using heuristics
3199				global	    a single global pool contains all CPUs
3200				percpu	    one pool for each CPU
3201				pernode	    one pool for each NUMA node (equivalent
3202					    to global on non-NUMA machines)
3203	
3204		sunrpc.tcp_slot_table_entries=
3205		sunrpc.udp_slot_table_entries=
3206				[NFS,SUNRPC]
3207				Sets the upper limit on the number of simultaneous
3208				RPC calls that can be sent from the client to a
3209				server. Increasing these values may allow you to
3210				improve throughput, but will also increase the
3211				amount of memory reserved for use by the client.
3212	
3213		swapaccount=[0|1]
3214				[KNL] Enable accounting of swap in memory resource
3215				controller if no parameter or 1 is given or disable
3216				it if 0 is given (See Documentation/cgroups/memory.txt)
3217	
3218		swiotlb=	[ARM,IA-64,PPC,MIPS,X86]
3219				Format: { <int> | force }
3220				<int> -- Number of I/O TLB slabs
3221				force -- force using of bounce buffers even if they
3222				         wouldn't be automatically used by the kernel
3223	
3224		switches=	[HW,M68k]
3225	
3226		sysfs.deprecated=0|1 [KNL]
3227				Enable/disable old style sysfs layout for old udev
3228				on older distributions. When this option is enabled
3229				very new udev will not work anymore. When this option
3230				is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3231				in older udev will not work anymore.
3232				Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3233				the kernel configuration.
3234	
3235		sysrq_always_enabled
3236				[KNL]
3237				Ignore sysrq setting - this boot parameter will
3238				neutralize any effect of /proc/sys/kernel/sysrq.
3239				Useful for debugging.
3240	
3241		tdfx=		[HW,DRM]
3242	
3243		test_suspend=	[SUSPEND]
3244				Specify "mem" (for Suspend-to-RAM) or "standby" (for
3245				standby suspend) as the system sleep state to briefly
3246				enter during system startup.  The system is woken from
3247				this state using a wakeup-capable RTC alarm.
3248	
3249		thash_entries=	[KNL,NET]
3250				Set number of hash buckets for TCP connection
3251	
3252		thermal.act=	[HW,ACPI]
3253				-1: disable all active trip points in all thermal zones
3254				<degrees C>: override all lowest active trip points
3255	
3256		thermal.crt=	[HW,ACPI]
3257				-1: disable all critical trip points in all thermal zones
3258				<degrees C>: override all critical trip points
3259	
3260		thermal.nocrt=	[HW,ACPI]
3261				Set to disable actions on ACPI thermal zone
3262				critical and hot trip points.
3263	
3264		thermal.off=	[HW,ACPI]
3265				1: disable ACPI thermal control
3266	
3267		thermal.psv=	[HW,ACPI]
3268				-1: disable all passive trip points
3269				<degrees C>: override all passive trip points to this
3270				value
3271	
3272		thermal.tzp=	[HW,ACPI]
3273				Specify global default ACPI thermal zone polling rate
3274				<deci-seconds>: poll all this frequency
3275				0: no polling (default)
3276	
3277		threadirqs	[KNL]
3278				Force threading of all interrupt handlers except those
3279				marked explicitly IRQF_NO_THREAD.
3280	
3281		tmem		[KNL,XEN]
3282				Enable the Transcendent memory driver if built-in.
3283	
3284		tmem.cleancache=0|1 [KNL, XEN]
3285				Default is on (1). Disable the usage of the cleancache
3286				API to send anonymous pages to the hypervisor.
3287	
3288		tmem.frontswap=0|1 [KNL, XEN]
3289				Default is on (1). Disable the usage of the frontswap
3290				API to send swap pages to the hypervisor. If disabled
3291				the selfballooning and selfshrinking are force disabled.
3292	
3293		tmem.selfballooning=0|1 [KNL, XEN]
3294				Default is on (1). Disable the driving of swap pages
3295				to the hypervisor.
3296	
3297		tmem.selfshrinking=0|1 [KNL, XEN]
3298				Default is on (1). Partial swapoff that immediately
3299				transfers pages from Xen hypervisor back to the
3300				kernel based on different criteria.
3301	
3302		topology=	[S390]
3303				Format: {off | on}
3304				Specify if the kernel should make use of the cpu
3305				topology information if the hardware supports this.
3306				The scheduler will make use of this information and
3307				e.g. base its process migration decisions on it.
3308				Default is on.
3309	
3310		tp720=		[HW,PS2]
3311	
3312		tpm_suspend_pcr=[HW,TPM]
3313				Format: integer pcr id
3314				Specify that at suspend time, the tpm driver
3315				should extend the specified pcr with zeros,
3316				as a workaround for some chips which fail to
3317				flush the last written pcr on TPM_SaveState.
3318				This will guarantee that all the other pcrs
3319				are saved.
3320	
3321		trace_buf_size=nn[KMG]
3322				[FTRACE] will set tracing buffer size.
3323	
3324		trace_event=[event-list]
3325				[FTRACE] Set and start specified trace events in order
3326				to facilitate early boot debugging.
3327				See also Documentation/trace/events.txt
3328	
3329		trace_options=[option-list]
3330				[FTRACE] Enable or disable tracer options at boot.
3331				The option-list is a comma delimited list of options
3332				that can be enabled or disabled just as if you were
3333				to echo the option name into
3334	
3335				    /sys/kernel/debug/tracing/trace_options
3336	
3337				For example, to enable stacktrace option (to dump the
3338				stack trace of each event), add to the command line:
3339	
3340				      trace_options=stacktrace
3341	
3342				See also Documentation/trace/ftrace.txt "trace options"
3343				section.
3344	
3345		traceoff_on_warning
3346				[FTRACE] enable this option to disable tracing when a
3347				warning is hit. This turns off "tracing_on". Tracing can
3348				be enabled again by echoing '1' into the "tracing_on"
3349				file located in /sys/kernel/debug/tracing/
3350	
3351				This option is useful, as it disables the trace before
3352				the WARNING dump is called, which prevents the trace to
3353				be filled with content caused by the warning output.
3354	
3355				This option can also be set at run time via the sysctl
3356				option:  kernel/traceoff_on_warning
3357	
3358		transparent_hugepage=
3359				[KNL]
3360				Format: [always|madvise|never]
3361				Can be used to control the default behavior of the system
3362				with respect to transparent hugepages.
3363				See Documentation/vm/transhuge.txt for more details.
3364	
3365		tsc=		Disable clocksource stability checks for TSC.
3366				Format: <string>
3367				[x86] reliable: mark tsc clocksource as reliable, this
3368				disables clocksource verification at runtime, as well
3369				as the stability checks done at bootup.	Used to enable
3370				high-resolution timer mode on older hardware, and in
3371				virtualized environment.
3372				[x86] noirqtime: Do not use TSC to do irq accounting.
3373				Used to run time disable IRQ_TIME_ACCOUNTING on any
3374				platforms where RDTSC is slow and this accounting
3375				can add overhead.
3376	
3377		turbografx.map[2|3]=	[HW,JOY]
3378				TurboGraFX parallel port interface
3379				Format:
3380				<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3381				See also Documentation/input/joystick-parport.txt
3382	
3383		udbg-immortal	[PPC] When debugging early kernel crashes that
3384				happen after console_init() and before a proper 
3385				console driver takes over, this boot options might
3386				help "seeing" what's going on.
3387	
3388		uhash_entries=	[KNL,NET]
3389				Set number of hash buckets for UDP/UDP-Lite connections
3390	
3391		uhci-hcd.ignore_oc=
3392				[USB] Ignore overcurrent events (default N).
3393				Some badly-designed motherboards generate lots of
3394				bogus events, for ports that aren't wired to
3395				anything.  Set this parameter to avoid log spamming.
3396				Note that genuine overcurrent events won't be
3397				reported either.
3398	
3399		unknown_nmi_panic
3400				[X86] Cause panic on unknown NMI.
3401	
3402		usbcore.authorized_default=
3403				[USB] Default USB device authorization:
3404				(default -1 = authorized except for wireless USB,
3405				0 = not authorized, 1 = authorized)
3406	
3407		usbcore.autosuspend=
3408				[USB] The autosuspend time delay (in seconds) used
3409				for newly-detected USB devices (default 2).  This
3410				is the time required before an idle device will be
3411				autosuspended.  Devices for which the delay is set
3412				to a negative value won't be autosuspended at all.
3413	
3414		usbcore.usbfs_snoop=
3415				[USB] Set to log all usbfs traffic (default 0 = off).
3416	
3417		usbcore.blinkenlights=
3418				[USB] Set to cycle leds on hubs (default 0 = off).
3419	
3420		usbcore.old_scheme_first=
3421				[USB] Start with the old device initialization
3422				scheme (default 0 = off).
3423	
3424		usbcore.usbfs_memory_mb=
3425				[USB] Memory limit (in MB) for buffers allocated by
3426				usbfs (default = 16, 0 = max = 2047).
3427	
3428		usbcore.use_both_schemes=
3429				[USB] Try the other device initialization scheme
3430				if the first one fails (default 1 = enabled).
3431	
3432		usbcore.initial_descriptor_timeout=
3433				[USB] Specifies timeout for the initial 64-byte
3434	                        USB_REQ_GET_DESCRIPTOR request in milliseconds
3435				(default 5000 = 5.0 seconds).
3436	
3437		usbhid.mousepoll=
3438				[USBHID] The interval which mice are to be polled at.
3439	
3440		usb-storage.delay_use=
3441				[UMS] The delay in seconds before a new device is
3442				scanned for Logical Units (default 5).
3443	
3444		usb-storage.quirks=
3445				[UMS] A list of quirks entries to supplement or
3446				override the built-in unusual_devs list.  List
3447				entries are separated by commas.  Each entry has
3448				the form VID:PID:Flags where VID and PID are Vendor
3449				and Product ID values (4-digit hex numbers) and
3450				Flags is a set of characters, each corresponding
3451				to a common usb-storage quirk flag as follows:
3452					a = SANE_SENSE (collect more than 18 bytes
3453						of sense data);
3454					b = BAD_SENSE (don't collect more than 18
3455						bytes of sense data);
3456					c = FIX_CAPACITY (decrease the reported
3457						device capacity by one sector);
3458					d = NO_READ_DISC_INFO (don't use
3459						READ_DISC_INFO command);
3460					e = NO_READ_CAPACITY_16 (don't use
3461						READ_CAPACITY_16 command);
3462					h = CAPACITY_HEURISTICS (decrease the
3463						reported device capacity by one
3464						sector if the number is odd);
3465					i = IGNORE_DEVICE (don't bind to this
3466						device);
3467					l = NOT_LOCKABLE (don't try to lock and
3468						unlock ejectable media);
3469					m = MAX_SECTORS_64 (don't transfer more
3470						than 64 sectors = 32 KB at a time);
3471					n = INITIAL_READ10 (force a retry of the
3472						initial READ(10) command);
3473					o = CAPACITY_OK (accept the capacity
3474						reported by the device);
3475					p = WRITE_CACHE (the device cache is ON
3476						by default);
3477					r = IGNORE_RESIDUE (the device reports
3478						bogus residue values);
3479					s = SINGLE_LUN (the device has only one
3480						Logical Unit);
3481					w = NO_WP_DETECT (don't test whether the
3482						medium is write-protected).
3483				Example: quirks=0419:aaf5:rl,0421:0433:rc
3484	
3485		user_debug=	[KNL,ARM]
3486				Format: <int>
3487				See arch/arm/Kconfig.debug help text.
3488					 1 - undefined instruction events
3489					 2 - system calls
3490					 4 - invalid data aborts
3491					 8 - SIGSEGV faults
3492					16 - SIGBUS faults
3493				Example: user_debug=31
3494	
3495		userpte=
3496				[X86] Flags controlling user PTE allocations.
3497	
3498					nohigh = do not allocate PTE pages in
3499						HIGHMEM regardless of setting
3500						of CONFIG_HIGHPTE.
3501	
3502		vdso=		[X86,SH]
3503				On X86_32, this is an alias for vdso32=.  Otherwise:
3504	
3505				vdso=1: enable VDSO (the default)
3506				vdso=0: disable VDSO mapping
3507	
3508		vdso32=		[X86] Control the 32-bit vDSO
3509				vdso32=1: enable 32-bit VDSO
3510				vdso32=0 or vdso32=2: disable 32-bit VDSO
3511	
3512				See the help text for CONFIG_COMPAT_VDSO for more
3513				details.  If CONFIG_COMPAT_VDSO is set, the default is
3514				vdso32=0; otherwise, the default is vdso32=1.
3515	
3516				For compatibility with older kernels, vdso32=2 is an
3517				alias for vdso32=0.
3518	
3519				Try vdso32=0 if you encounter an error that says:
3520				dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3521	
3522		vector=		[IA-64,SMP]
3523				vector=percpu: enable percpu vector domain
3524	
3525		video=		[FB] Frame buffer configuration
3526				See Documentation/fb/modedb.txt.
3527	
3528		video.brightness_switch_enabled= [0,1]
3529				If set to 1, on receiving an ACPI notify event
3530				generated by hotkey, video driver will adjust brightness
3531				level and then send out the event to user space through
3532				the allocated input device; If set to 0, video driver
3533				will only send out the event without touching backlight
3534				brightness level.
3535				default: 1
3536	
3537		virtio_mmio.device=
3538				[VMMIO] Memory mapped virtio (platform) device.
3539	
3540					<size>@<baseaddr>:<irq>[:<id>]
3541				where:
3542					<size>     := size (can use standard suffixes
3543							like K, M and G)
3544					<baseaddr> := physical base address
3545					<irq>      := interrupt number (as passed to
3546							request_irq())
3547					<id>       := (optional) platform device id
3548				example:
3549					virtio_mmio.device=1K@0x100b0000:48:7
3550	
3551				Can be used multiple times for multiple devices.
3552	
3553		vga=		[BOOT,X86-32] Select a particular video mode
3554				See Documentation/x86/boot.txt and
3555				Documentation/svga.txt.
3556				Use vga=ask for menu.
3557				This is actually a boot loader parameter; the value is
3558				passed to the kernel using a special protocol.
3559	
3560		vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
3561				size of <nn>. This can be used to increase the
3562				minimum size (128MB on x86). It can also be used to
3563				decrease the size and leave more room for directly
3564				mapped kernel RAM.
3565	
3566		vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
3567				Format: <command>
3568	
3569		vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
3570				Format: <command>
3571	
3572		vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
3573				Format: <command>
3574	
3575		vsyscall=	[X86-64]
3576				Controls the behavior of vsyscalls (i.e. calls to
3577				fixed addresses of 0xffffffffff600x00 from legacy
3578				code).  Most statically-linked binaries and older
3579				versions of glibc use these calls.  Because these
3580				functions are at fixed addresses, they make nice
3581				targets for exploits that can control RIP.
3582	
3583				emulate     [default] Vsyscalls turn into traps and are
3584				            emulated reasonably safely.
3585	
3586				native      Vsyscalls are native syscall instructions.
3587				            This is a little bit faster than trapping
3588				            and makes a few dynamic recompilers work
3589				            better than they would in emulation mode.
3590				            It also makes exploits much easier to write.
3591	
3592				none        Vsyscalls don't work at all.  This makes
3593				            them quite hard to use for exploits but
3594				            might break your system.
3595	
3596		vt.color=	[VT] Default text color.
3597				Format: 0xYX, X = foreground, Y = background.
3598				Default: 0x07 = light gray on black.
3599	
3600		vt.cur_default=	[VT] Default cursor shape.
3601				Format: 0xCCBBAA, where AA, BB, and CC are the same as
3602				the parameters of the <Esc>[?A;B;Cc escape sequence;
3603				see VGA-softcursor.txt. Default: 2 = underline.
3604	
3605		vt.default_blu=	[VT]
3606				Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3607				Change the default blue palette of the console.
3608				This is a 16-member array composed of values
3609				ranging from 0-255.
3610	
3611		vt.default_grn=	[VT]
3612				Format: <green0>,<green1>,<green2>,...,<green15>
3613				Change the default green palette of the console.
3614				This is a 16-member array composed of values
3615				ranging from 0-255.
3616	
3617		vt.default_red=	[VT]
3618				Format: <red0>,<red1>,<red2>,...,<red15>
3619				Change the default red palette of the console.
3620				This is a 16-member array composed of values
3621				ranging from 0-255.
3622	
3623		vt.default_utf8=
3624				[VT]
3625				Format=<0|1>
3626				Set system-wide default UTF-8 mode for all tty's.
3627				Default is 1, i.e. UTF-8 mode is enabled for all
3628				newly opened terminals.
3629	
3630		vt.global_cursor_default=
3631				[VT]
3632				Format=<-1|0|1>
3633				Set system-wide default for whether a cursor
3634				is shown on new VTs. Default is -1,
3635				i.e. cursors will be created by default unless
3636				overridden by individual drivers. 0 will hide
3637				cursors, 1 will display them.
3638	
3639		vt.italic=	[VT] Default color for italic text; 0-15.
3640				Default: 2 = green.
3641	
3642		vt.underline=	[VT] Default color for underlined text; 0-15.
3643				Default: 3 = cyan.
3644	
3645		watchdog timers	[HW,WDT] For information on watchdog timers,
3646				see Documentation/watchdog/watchdog-parameters.txt
3647				or other driver-specific files in the
3648				Documentation/watchdog/ directory.
3649	
3650		workqueue.disable_numa
3651				By default, all work items queued to unbound
3652				workqueues are affine to the NUMA nodes they're
3653				issued on, which results in better behavior in
3654				general.  If NUMA affinity needs to be disabled for
3655				whatever reason, this option can be used.  Note
3656				that this also can be controlled per-workqueue for
3657				workqueues visible under /sys/bus/workqueue/.
3658	
3659		workqueue.power_efficient
3660				Per-cpu workqueues are generally preferred because
3661				they show better performance thanks to cache
3662				locality; unfortunately, per-cpu workqueues tend to
3663				be more power hungry than unbound workqueues.
3664	
3665				Enabling this makes the per-cpu workqueues which
3666				were observed to contribute significantly to power
3667				consumption unbound, leading to measurably lower
3668				power usage at the cost of small performance
3669				overhead.
3670	
3671				The default value of this parameter is determined by
3672				the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3673	
3674		x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
3675				default x2apic cluster mode on platforms
3676				supporting x2apic.
3677	
3678		x86_intel_mid_timer= [X86-32,APBT]
3679				Choose timer option for x86 Intel MID platform.
3680				Two valid options are apbt timer only and lapic timer
3681				plus one apbt timer for broadcast timer.
3682				x86_intel_mid_timer=apbt_only | lapic_and_apbt
3683	
3684		xen_emul_unplug=		[HW,X86,XEN]
3685				Unplug Xen emulated devices
3686				Format: [unplug0,][unplug1]
3687				ide-disks -- unplug primary master IDE devices
3688				aux-ide-disks -- unplug non-primary-master IDE devices
3689				nics -- unplug network devices
3690				all -- unplug all emulated devices (NICs and IDE disks)
3691				unnecessary -- unplugging emulated devices is
3692					unnecessary even if the host did not respond to
3693					the unplug protocol
3694				never -- do not unplug even if version check succeeds
3695	
3696		xen_nopvspin	[X86,XEN]
3697				Disables the ticketlock slowpath using Xen PV
3698				optimizations.
3699	
3700		xirc2ps_cs=	[NET,PCMCIA]
3701				Format:
3702				<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3703	
3704	______________________________________________________________________
3705	
3706	TODO:
3707	
3708		Add more DRM drivers.
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