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Based on kernel version 4.0. Page generated on 2015-04-14 21:25 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		ca_keys=	[KEYS] This parameter identifies a specific key(s) on
570				the system trusted keyring to be used for certificate
571				trust validation.
572				format: { id:<keyid> | builtin }
573	
574		cca=		[MIPS] Override the kernel pages' cache coherency
575				algorithm.  Accepted values range from 0 to 7
576				inclusive. See arch/mips/include/asm/pgtable-bits.h
577				for platform specific values (SB1, Loongson3 and
578				others).
579	
580		ccw_timeout_log [S390]
581				See Documentation/s390/CommonIO for details.
582	
583		cgroup_disable= [KNL] Disable a particular controller
584				Format: {name of the controller(s) to disable}
585				The effects of cgroup_disable=foo are:
586				- foo isn't auto-mounted if you mount all cgroups in
587				  a single hierarchy
588				- foo isn't visible as an individually mountable
589				  subsystem
590				{Currently only "memory" controller deal with this and
591				cut the overhead, others just disable the usage. So
592				only cgroup_disable=memory is actually worthy}
593	
594		checkreqprot	[SELINUX] Set initial checkreqprot flag value.
595				Format: { "0" | "1" }
596				See security/selinux/Kconfig help text.
597				0 -- check protection applied by kernel (includes
598					any implied execute protection).
599				1 -- check protection requested by application.
600				Default value is set via a kernel config option.
601				Value can be changed at runtime via
602					/selinux/checkreqprot.
603	
604		cio_ignore=	[S390]
605				See Documentation/s390/CommonIO for details.
606		clk_ignore_unused
607				[CLK]
608				Prevents the clock framework from automatically gating
609				clocks that have not been explicitly enabled by a Linux
610				device driver but are enabled in hardware at reset or
611				by the bootloader/firmware. Note that this does not
612				force such clocks to be always-on nor does it reserve
613				those clocks in any way. This parameter is useful for
614				debug and development, but should not be needed on a
615				platform with proper driver support.  For more
616				information, see Documentation/clk.txt.
617	
618		clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
619				[Deprecated]
620				Forces specified clocksource (if available) to be used
621				when calculating gettimeofday(). If specified
622				clocksource is not available, it defaults to PIT.
623				Format: { pit | tsc | cyclone | pmtmr }
624	
625		clocksource=	Override the default clocksource
626				Format: <string>
627				Override the default clocksource and use the clocksource
628				with the name specified.
629				Some clocksource names to choose from, depending on
630				the platform:
631				[all] jiffies (this is the base, fallback clocksource)
632				[ACPI] acpi_pm
633				[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
634					pxa_timer,timer3,32k_counter,timer0_1
635				[AVR32] avr32
636				[X86-32] pit,hpet,tsc;
637					scx200_hrt on Geode; cyclone on IBM x440
638				[MIPS] MIPS
639				[PARISC] cr16
640				[S390] tod
641				[SH] SuperH
642				[SPARC64] tick
643				[X86-64] hpet,tsc
644	
645		clearcpuid=BITNUM [X86]
646				Disable CPUID feature X for the kernel. See
647				arch/x86/include/asm/cpufeature.h for the valid bit
648				numbers. Note the Linux specific bits are not necessarily
649				stable over kernel options, but the vendor specific
650				ones should be.
651				Also note that user programs calling CPUID directly
652				or using the feature without checking anything
653				will still see it. This just prevents it from
654				being used by the kernel or shown in /proc/cpuinfo.
655				Also note the kernel might malfunction if you disable
656				some critical bits.
657	
658		cma=nn[MG]@[start[MG][-end[MG]]]
659				[ARM,X86,KNL]
660				Sets the size of kernel global memory area for
661				contiguous memory allocations and optionally the
662				placement constraint by the physical address range of
663				memory allocations. A value of 0 disables CMA
664				altogether. For more information, see
665				include/linux/dma-contiguous.h
666	
667		cmo_free_hint=	[PPC] Format: { yes | no }
668				Specify whether pages are marked as being inactive
669				when they are freed.  This is used in CMO environments
670				to determine OS memory pressure for page stealing by
671				a hypervisor.
672				Default: yes
673	
674		coherent_pool=nn[KMG]	[ARM,KNL]
675				Sets the size of memory pool for coherent, atomic dma
676				allocations, by default set to 256K.
677	
678		code_bytes	[X86] How many bytes of object code to print
679				in an oops report.
680				Range: 0 - 8192
681				Default: 64
682	
683		com20020=	[HW,NET] ARCnet - COM20020 chipset
684				Format:
685				<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
686	
687		com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
688				Format: <io>[,<irq>]
689	
690		com90xx=	[HW,NET]
691				ARCnet - COM90xx chipset (memory-mapped buffers)
692				Format: <io>[,<irq>[,<memstart>]]
693	
694		condev=		[HW,S390] console device
695		conmode=
696	
697		console=	[KNL] Output console device and options.
698	
699			tty<n>	Use the virtual console device <n>.
700	
701			ttyS<n>[,options]
702			ttyUSB0[,options]
703				Use the specified serial port.  The options are of
704				the form "bbbbpnf", where "bbbb" is the baud rate,
705				"p" is parity ("n", "o", or "e"), "n" is number of
706				bits, and "f" is flow control ("r" for RTS or
707				omit it).  Default is "9600n8".
708	
709				See Documentation/serial-console.txt for more
710				information.  See
711				Documentation/networking/netconsole.txt for an
712				alternative.
713	
714			uart[8250],io,<addr>[,options]
715			uart[8250],mmio,<addr>[,options]
716				Start an early, polled-mode console on the 8250/16550
717				UART at the specified I/O port or MMIO address,
718				switching to the matching ttyS device later.  The
719				options are the same as for ttyS, above.
720			hvc<n>	Use the hypervisor console device <n>. This is for
721				both Xen and PowerPC hypervisors.
722	
723	                If the device connected to the port is not a TTY but a braille
724	                device, prepend "brl," before the device type, for instance
725				console=brl,ttyS0
726			For now, only VisioBraille is supported.
727	
728		consoleblank=	[KNL] The console blank (screen saver) timeout in
729				seconds. Defaults to 10*60 = 10mins. A value of 0
730				disables the blank timer.
731	
732		coredump_filter=
733				[KNL] Change the default value for
734				/proc/<pid>/coredump_filter.
735				See also Documentation/filesystems/proc.txt.
736	
737		cpuidle.off=1	[CPU_IDLE]
738				disable the cpuidle sub-system
739	
740		cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
741				Format:
742				<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
743	
744		crashkernel=size[KMG][@offset[KMG]]
745				[KNL] Using kexec, Linux can switch to a 'crash kernel'
746				upon panic. This parameter reserves the physical
747				memory region [offset, offset + size] for that kernel
748				image. If '@offset' is omitted, then a suitable offset
749				is selected automatically. Check
750				Documentation/kdump/kdump.txt for further details.
751	
752		crashkernel=range1:size1[,range2:size2,...][@offset]
753				[KNL] Same as above, but depends on the memory
754				in the running system. The syntax of range is
755				start-[end] where start and end are both
756				a memory unit (amount[KMG]). See also
757				Documentation/kdump/kdump.txt for an example.
758	
759		crashkernel=size[KMG],high
760				[KNL, x86_64] range could be above 4G. Allow kernel
761				to allocate physical memory region from top, so could
762				be above 4G if system have more than 4G ram installed.
763				Otherwise memory region will be allocated below 4G, if
764				available.
765				It will be ignored if crashkernel=X is specified.
766		crashkernel=size[KMG],low
767				[KNL, x86_64] range under 4G. When crashkernel=X,high
768				is passed, kernel could allocate physical memory region
769				above 4G, that cause second kernel crash on system
770				that require some amount of low memory, e.g. swiotlb
771				requires at least 64M+32K low memory.  Kernel would
772				try to allocate 72M below 4G automatically.
773				This one let user to specify own low range under 4G
774				for second kernel instead.
775				0: to disable low allocation.
776				It will be ignored when crashkernel=X,high is not used
777				or memory reserved is below 4G.
778	
779		cs89x0_dma=	[HW,NET]
780				Format: <dma>
781	
782		cs89x0_media=	[HW,NET]
783				Format: { rj45 | aui | bnc }
784	
785		dasd=		[HW,NET]
786				See header of drivers/s390/block/dasd_devmap.c.
787	
788		db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
789				(one device per port)
790				Format: <port#>,<type>
791				See also Documentation/input/joystick-parport.txt
792	
793		ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
794				time. See Documentation/dynamic-debug-howto.txt for
795				details.  Deprecated, see dyndbg.
796	
797		debug		[KNL] Enable kernel debugging (events log level).
798	
799		debug_locks_verbose=
800				[KNL] verbose self-tests
801				Format=<0|1>
802				Print debugging info while doing the locking API
803				self-tests.
804				We default to 0 (no extra messages), setting it to
805				1 will print _a lot_ more information - normally
806				only useful to kernel developers.
807	
808		debug_objects	[KNL] Enable object debugging
809	
810		no_debug_objects
811				[KNL] Disable object debugging
812	
813		debug_guardpage_minorder=
814				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
815				parameter allows control of the order of pages that will
816				be intentionally kept free (and hence protected) by the
817				buddy allocator. Bigger value increase the probability
818				of catching random memory corruption, but reduce the
819				amount of memory for normal system use. The maximum
820				possible value is MAX_ORDER/2.  Setting this parameter
821				to 1 or 2 should be enough to identify most random
822				memory corruption problems caused by bugs in kernel or
823				driver code when a CPU writes to (or reads from) a
824				random memory location. Note that there exists a class
825				of memory corruptions problems caused by buggy H/W or
826				F/W or by drivers badly programing DMA (basically when
827				memory is written at bus level and the CPU MMU is
828				bypassed) which are not detectable by
829				CONFIG_DEBUG_PAGEALLOC, hence this option will not help
830				tracking down these problems.
831	
832		debug_pagealloc=
833				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
834				parameter enables the feature at boot time. In
835				default, it is disabled. We can avoid allocating huge
836				chunk of memory for debug pagealloc if we don't enable
837				it at boot time and the system will work mostly same
838				with the kernel built without CONFIG_DEBUG_PAGEALLOC.
839				on: enable the feature
840	
841		debugpat	[X86] Enable PAT debugging
842	
843		decnet.addr=	[HW,NET]
844				Format: <area>[,<node>]
845				See also Documentation/networking/decnet.txt.
846	
847		default_hugepagesz=
848				[same as hugepagesz=] The size of the default
849				HugeTLB page size. This is the size represented by
850				the legacy /proc/ hugepages APIs, used for SHM, and
851				default size when mounting hugetlbfs filesystems.
852				Defaults to the default architecture's huge page size
853				if not specified.
854	
855		dhash_entries=	[KNL]
856				Set number of hash buckets for dentry cache.
857	
858		disable=	[IPV6]
859				See Documentation/networking/ipv6.txt.
860	
861		disable_cpu_apicid= [X86,APIC,SMP]
862				Format: <int>
863				The number of initial APIC ID for the
864				corresponding CPU to be disabled at boot,
865				mostly used for the kdump 2nd kernel to
866				disable BSP to wake up multiple CPUs without
867				causing system reset or hang due to sending
868				INIT from AP to BSP.
869	
870		disable_ddw     [PPC/PSERIES]
871				Disable Dynamic DMA Window support. Use this if
872				to workaround buggy firmware.
873	
874		disable_ipv6=	[IPV6]
875				See Documentation/networking/ipv6.txt.
876	
877		disable_mtrr_cleanup [X86]
878				The kernel tries to adjust MTRR layout from continuous
879				to discrete, to make X server driver able to add WB
880				entry later. This parameter disables that.
881	
882		disable_mtrr_trim [X86, Intel and AMD only]
883				By default the kernel will trim any uncacheable
884				memory out of your available memory pool based on
885				MTRR settings.  This parameter disables that behavior,
886				possibly causing your machine to run very slowly.
887	
888		disable_timer_pin_1 [X86]
889				Disable PIN 1 of APIC timer
890				Can be useful to work around chipset bugs.
891	
892		dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
893				this option disables the debugging code at boot.
894	
895		dma_debug_entries=<number>
896				This option allows to tune the number of preallocated
897				entries for DMA-API debugging code. One entry is
898				required per DMA-API allocation. Use this if the
899				DMA-API debugging code disables itself because the
900				architectural default is too low.
901	
902		dma_debug_driver=<driver_name>
903				With this option the DMA-API debugging driver
904				filter feature can be enabled at boot time. Just
905				pass the driver to filter for as the parameter.
906				The filter can be disabled or changed to another
907				driver later using sysfs.
908	
909		drm_kms_helper.edid_firmware=[<connector>:]<file>
910				Broken monitors, graphic adapters and KVMs may
911				send no or incorrect EDID data sets. This parameter
912				allows to specify an EDID data set in the
913				/lib/firmware directory that is used instead.
914				Generic built-in EDID data sets are used, if one of
915				edid/1024x768.bin, edid/1280x1024.bin,
916				edid/1680x1050.bin, or edid/1920x1080.bin is given
917				and no file with the same name exists. Details and
918				instructions how to build your own EDID data are
919				available in Documentation/EDID/HOWTO.txt. An EDID
920				data set will only be used for a particular connector,
921				if its name and a colon are prepended to the EDID
922				name.
923	
924		dscc4.setup=	[NET]
925	
926		dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
927		module.dyndbg[="val"]
928				Enable debug messages at boot time.  See
929				Documentation/dynamic-debug-howto.txt for details.
930	
931		early_ioremap_debug [KNL]
932				Enable debug messages in early_ioremap support. This
933				is useful for tracking down temporary early mappings
934				which are not unmapped.
935	
936		earlycon=	[KNL] Output early console device and options.
937	
938			cdns,<addr>
939				Start an early, polled-mode console on a cadence serial
940				port at the specified address. The cadence serial port
941				must already be setup and configured. Options are not
942				yet supported.
943	
944			uart[8250],io,<addr>[,options]
945			uart[8250],mmio,<addr>[,options]
946			uart[8250],mmio32,<addr>[,options]
947				Start an early, polled-mode console on the 8250/16550
948				UART at the specified I/O port or MMIO address.
949				MMIO inter-register address stride is either 8-bit
950				(mmio) or 32-bit (mmio32).
951				The options are the same as for ttyS, above.
952	
953			pl011,<addr>
954				Start an early, polled-mode console on a pl011 serial
955				port at the specified address. The pl011 serial port
956				must already be setup and configured. Options are not
957				yet supported.
958	
959			msm_serial,<addr>
960				Start an early, polled-mode console on an msm serial
961				port at the specified address. The serial port
962				must already be setup and configured. Options are not
963				yet supported.
964	
965			msm_serial_dm,<addr>
966				Start an early, polled-mode console on an msm serial
967				dm port at the specified address. The serial port
968				must already be setup and configured. Options are not
969				yet supported.
970	
971			smh	Use ARM semihosting calls for early console.
972	
973			s3c2410,<addr>
974			s3c2412,<addr>
975			s3c2440,<addr>
976			s3c6400,<addr>
977			s5pv210,<addr>
978			exynos4210,<addr>
979				Use early console provided by serial driver available
980				on Samsung SoCs, requires selecting proper type and
981				a correct base address of the selected UART port. The
982				serial port must already be setup and configured.
983				Options are not yet supported.
984	
985		earlyprintk=	[X86,SH,BLACKFIN,ARM,M68k]
986				earlyprintk=vga
987				earlyprintk=efi
988				earlyprintk=xen
989				earlyprintk=serial[,ttySn[,baudrate]]
990				earlyprintk=serial[,0x...[,baudrate]]
991				earlyprintk=ttySn[,baudrate]
992				earlyprintk=dbgp[debugController#]
993	
994				earlyprintk is useful when the kernel crashes before
995				the normal console is initialized. It is not enabled by
996				default because it has some cosmetic problems.
997	
998				Append ",keep" to not disable it when the real console
999				takes over.
1000	
1001				Only one of vga, efi, serial, or usb debug port can
1002				be used at a time.
1003	
1004				Currently only ttyS0 and ttyS1 may be specified by
1005				name.  Other I/O ports may be explicitly specified
1006				on some architectures (x86 and arm at least) by
1007				replacing ttySn with an I/O port address, like this:
1008					earlyprintk=serial,0x1008,115200
1009				You can find the port for a given device in
1010				/proc/tty/driver/serial:
1011					2: uart:ST16650V2 port:00001008 irq:18 ...
1012	
1013				Interaction with the standard serial driver is not
1014				very good.
1015	
1016				The VGA and EFI output is eventually overwritten by
1017				the real console.
1018	
1019				The xen output can only be used by Xen PV guests.
1020	
1021		edac_report=	[HW,EDAC] Control how to report EDAC event
1022				Format: {"on" | "off" | "force"}
1023				on: enable EDAC to report H/W event. May be overridden
1024				by other higher priority error reporting module.
1025				off: disable H/W event reporting through EDAC.
1026				force: enforce the use of EDAC to report H/W event.
1027				default: on.
1028	
1029		ekgdboc=	[X86,KGDB] Allow early kernel console debugging
1030				ekgdboc=kbd
1031	
1032				This is designed to be used in conjunction with
1033				the boot argument: earlyprintk=vga
1034	
1035		edd=		[EDD]
1036				Format: {"off" | "on" | "skip[mbr]"}
1037	
1038		efi=		[EFI]
1039				Format: { "old_map", "nochunk", "noruntime" }
1040				old_map [X86-64]: switch to the old ioremap-based EFI
1041				runtime services mapping. 32-bit still uses this one by
1042				default.
1043				nochunk: disable reading files in "chunks" in the EFI
1044				boot stub, as chunking can cause problems with some
1045				firmware implementations.
1046				noruntime : disable EFI runtime services support
1047	
1048		efi_no_storage_paranoia [EFI; X86]
1049				Using this parameter you can use more than 50% of
1050				your efi variable storage. Use this parameter only if
1051				you are really sure that your UEFI does sane gc and
1052				fulfills the spec otherwise your board may brick.
1053	
1054		eisa_irq_edge=	[PARISC,HW]
1055				See header of drivers/parisc/eisa.c.
1056	
1057		elanfreq=	[X86-32]
1058				See comment before function elanfreq_setup() in
1059				arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1060	
1061		elevator=	[IOSCHED]
1062				Format: {"cfq" | "deadline" | "noop"}
1063				See Documentation/block/cfq-iosched.txt and
1064				Documentation/block/deadline-iosched.txt for details.
1065	
1066		elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1067				Specifies physical address of start of kernel core
1068				image elf header and optionally the size. Generally
1069				kexec loader will pass this option to capture kernel.
1070				See Documentation/kdump/kdump.txt for details.
1071	
1072		enable_mtrr_cleanup [X86]
1073				The kernel tries to adjust MTRR layout from continuous
1074				to discrete, to make X server driver able to add WB
1075				entry later. This parameter enables that.
1076	
1077		enable_timer_pin_1 [X86]
1078				Enable PIN 1 of APIC timer
1079				Can be useful to work around chipset bugs
1080				(in particular on some ATI chipsets).
1081				The kernel tries to set a reasonable default.
1082	
1083		enforcing	[SELINUX] Set initial enforcing status.
1084				Format: {"0" | "1"}
1085				See security/selinux/Kconfig help text.
1086				0 -- permissive (log only, no denials).
1087				1 -- enforcing (deny and log).
1088				Default value is 0.
1089				Value can be changed at runtime via /selinux/enforce.
1090	
1091		erst_disable	[ACPI]
1092				Disable Error Record Serialization Table (ERST)
1093				support.
1094	
1095		ether=		[HW,NET] Ethernet cards parameters
1096				This option is obsoleted by the "netdev=" option, which
1097				has equivalent usage. See its documentation for details.
1098	
1099		evm=		[EVM]
1100				Format: { "fix" }
1101				Permit 'security.evm' to be updated regardless of
1102				current integrity status.
1103	
1104		failslab=
1105		fail_page_alloc=
1106		fail_make_request=[KNL]
1107				General fault injection mechanism.
1108				Format: <interval>,<probability>,<space>,<times>
1109				See also Documentation/fault-injection/.
1110	
1111		floppy=		[HW]
1112				See Documentation/blockdev/floppy.txt.
1113	
1114		force_pal_cache_flush
1115				[IA-64] Avoid check_sal_cache_flush which may hang on
1116				buggy SAL_CACHE_FLUSH implementations. Using this
1117				parameter will force ia64_sal_cache_flush to call
1118				ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1119	
1120		forcepae [X86-32]
1121				Forcefully enable Physical Address Extension (PAE).
1122				Many Pentium M systems disable PAE but may have a
1123				functionally usable PAE implementation.
1124				Warning: use of this parameter will taint the kernel
1125				and may cause unknown problems.
1126	
1127		ftrace=[tracer]
1128				[FTRACE] will set and start the specified tracer
1129				as early as possible in order to facilitate early
1130				boot debugging.
1131	
1132		ftrace_dump_on_oops[=orig_cpu]
1133				[FTRACE] will dump the trace buffers on oops.
1134				If no parameter is passed, ftrace will dump
1135				buffers of all CPUs, but if you pass orig_cpu, it will
1136				dump only the buffer of the CPU that triggered the
1137				oops.
1138	
1139		ftrace_filter=[function-list]
1140				[FTRACE] Limit the functions traced by the function
1141				tracer at boot up. function-list is a comma separated
1142				list of functions. This list can be changed at run
1143				time by the set_ftrace_filter file in the debugfs
1144				tracing directory.
1145	
1146		ftrace_notrace=[function-list]
1147				[FTRACE] Do not trace the functions specified in
1148				function-list. This list can be changed at run time
1149				by the set_ftrace_notrace file in the debugfs
1150				tracing directory.
1151	
1152		ftrace_graph_filter=[function-list]
1153				[FTRACE] Limit the top level callers functions traced
1154				by the function graph tracer at boot up.
1155				function-list is a comma separated list of functions
1156				that can be changed at run time by the
1157				set_graph_function file in the debugfs tracing directory.
1158	
1159		ftrace_graph_notrace=[function-list]
1160				[FTRACE] Do not trace from the functions specified in
1161				function-list.  This list is a comma separated list of
1162				functions that can be changed at run time by the
1163				set_graph_notrace file in the debugfs tracing directory.
1164	
1165		gamecon.map[2|3]=
1166				[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1167				support via parallel port (up to 5 devices per port)
1168				Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1169				See also Documentation/input/joystick-parport.txt
1170	
1171		gamma=		[HW,DRM]
1172	
1173		gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
1174				Format: off | on
1175				default: on
1176	
1177		gcov_persist=	[GCOV] When non-zero (default), profiling data for
1178				kernel modules is saved and remains accessible via
1179				debugfs, even when the module is unloaded/reloaded.
1180				When zero, profiling data is discarded and associated
1181				debugfs files are removed at module unload time.
1182	
1183		gpt		[EFI] Forces disk with valid GPT signature but
1184				invalid Protective MBR to be treated as GPT. If the
1185				primary GPT is corrupted, it enables the backup/alternate
1186				GPT to be used instead.
1187	
1188		grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1189				the "Enable 0" bit of the configuration register.
1190				Format: 0 | 1
1191				Default: 0
1192		grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1193				the "Enable 0" bit of the configuration register.
1194				Format: 0 | 1
1195				Default: 0
1196		grcan.select=	[HW] Select which physical interface to use.
1197				Format: 0 | 1
1198				Default: 0
1199		grcan.txsize=	[HW] Sets the size of the tx buffer.
1200				Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1201				Default: 1024
1202		grcan.rxsize=	[HW] Sets the size of the rx buffer.
1203				Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1204				Default: 1024
1205	
1206		hashdist=	[KNL,NUMA] Large hashes allocated during boot
1207				are distributed across NUMA nodes.  Defaults on
1208				for 64-bit NUMA, off otherwise.
1209				Format: 0 | 1 (for off | on)
1210	
1211		hcl=		[IA-64] SGI's Hardware Graph compatibility layer
1212	
1213		hd=		[EIDE] (E)IDE hard drive subsystem geometry
1214				Format: <cyl>,<head>,<sect>
1215	
1216		hest_disable	[ACPI]
1217				Disable Hardware Error Source Table (HEST) support;
1218				corresponding firmware-first mode error processing
1219				logic will be disabled.
1220	
1221		highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
1222				size of <nn>. This works even on boxes that have no
1223				highmem otherwise. This also works to reduce highmem
1224				size on bigger boxes.
1225	
1226		highres=	[KNL] Enable/disable high resolution timer mode.
1227				Valid parameters: "on", "off"
1228				Default: "on"
1229	
1230		hisax=		[HW,ISDN]
1231				See Documentation/isdn/README.HiSax.
1232	
1233		hlt		[BUGS=ARM,SH]
1234	
1235		hpet=		[X86-32,HPET] option to control HPET usage
1236				Format: { enable (default) | disable | force |
1237					verbose }
1238				disable: disable HPET and use PIT instead
1239				force: allow force enabled of undocumented chips (ICH4,
1240					VIA, nVidia)
1241				verbose: show contents of HPET registers during setup
1242	
1243		hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1244				registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1245	
1246		hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1247		hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1248				On x86-64 and powerpc, this option can be specified
1249				multiple times interleaved with hugepages= to reserve
1250				huge pages of different sizes. Valid pages sizes on
1251				x86-64 are 2M (when the CPU supports "pse") and 1G
1252				(when the CPU supports the "pdpe1gb" cpuinfo flag).
1253	
1254		hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
1255				       terminal devices. Valid values: 0..8
1256		hvc_iucv_allow=	[S390] Comma-separated list of z/VM user IDs.
1257				       If specified, z/VM IUCV HVC accepts connections
1258				       from listed z/VM user IDs only.
1259	
1260		hwthread_map=	[METAG] Comma-separated list of Linux cpu id to
1261				        hardware thread id mappings.
1262					Format: <cpu>:<hwthread>
1263	
1264		keep_bootcon	[KNL]
1265				Do not unregister boot console at start. This is only
1266				useful for debugging when something happens in the window
1267				between unregistering the boot console and initializing
1268				the real console.
1269	
1270		i2c_bus=	[HW] Override the default board specific I2C bus speed
1271				     or register an additional I2C bus that is not
1272				     registered from board initialization code.
1273				     Format:
1274				     <bus_id>,<clkrate>
1275	
1276		i8042.debug	[HW] Toggle i8042 debug mode
1277		i8042.direct	[HW] Put keyboard port into non-translated mode
1278		i8042.dumbkbd	[HW] Pretend that controller can only read data from
1279				     keyboard and cannot control its state
1280				     (Don't attempt to blink the leds)
1281		i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1282		i8042.nokbd	[HW] Don't check/create keyboard port
1283		i8042.noloop	[HW] Disable the AUX Loopback command while probing
1284				     for the AUX port
1285		i8042.nomux	[HW] Don't check presence of an active multiplexing
1286				     controller
1287		i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1288				     controllers
1289		i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1290		i8042.reset	[HW] Reset the controller during init and cleanup
1291		i8042.unlock	[HW] Unlock (ignore) the keylock
1292		i8042.kbdreset  [HW] Reset device connected to KBD port
1293	
1294		i810=		[HW,DRM]
1295	
1296		i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
1297				indicates that the driver is running on unsupported
1298				hardware.
1299		i8k.force	[HW] Activate i8k driver even if SMM BIOS signature
1300				does not match list of supported models.
1301		i8k.power_status
1302				[HW] Report power status in /proc/i8k
1303				(disabled by default)
1304		i8k.restricted	[HW] Allow controlling fans only if SYS_ADMIN
1305				capability is set.
1306	
1307		i915.invert_brightness=
1308				[DRM] Invert the sense of the variable that is used to
1309				set the brightness of the panel backlight. Normally a
1310				brightness value of 0 indicates backlight switched off,
1311				and the maximum of the brightness value sets the backlight
1312				to maximum brightness. If this parameter is set to 0
1313				(default) and the machine requires it, or this parameter
1314				is set to 1, a brightness value of 0 sets the backlight
1315				to maximum brightness, and the maximum of the brightness
1316				value switches the backlight off.
1317				-1 -- never invert brightness
1318				 0 -- machine default
1319				 1 -- force brightness inversion
1320	
1321		icn=		[HW,ISDN]
1322				Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1323	
1324		ide-core.nodma=	[HW] (E)IDE subsystem
1325				Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1326				.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1327				.cdrom .chs .ignore_cable are additional options
1328				See Documentation/ide/ide.txt.
1329	
1330		ide-generic.probe-mask= [HW] (E)IDE subsystem
1331				Format: <int>
1332				Probe mask for legacy ISA IDE ports.  Depending on
1333				platform up to 6 ports are supported, enabled by
1334				setting corresponding bits in the mask to 1.  The
1335				default value is 0x0, which has a special meaning.
1336				On systems that have PCI, it triggers scanning the
1337				PCI bus for the first and the second port, which
1338				are then probed.  On systems without PCI the value
1339				of 0x0 enables probing the two first ports as if it
1340				was 0x3.
1341	
1342		ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1343				Claim all unknown PCI IDE storage controllers.
1344	
1345		idle=		[X86]
1346				Format: idle=poll, idle=halt, idle=nomwait
1347				Poll forces a polling idle loop that can slightly
1348				improve the performance of waking up a idle CPU, but
1349				will use a lot of power and make the system run hot.
1350				Not recommended.
1351				idle=halt: Halt is forced to be used for CPU idle.
1352				In such case C2/C3 won't be used again.
1353				idle=nomwait: Disable mwait for CPU C-states
1354	
1355		ignore_loglevel	[KNL]
1356				Ignore loglevel setting - this will print /all/
1357				kernel messages to the console. Useful for debugging.
1358				We also add it as printk module parameter, so users
1359				could change it dynamically, usually by
1360				/sys/module/printk/parameters/ignore_loglevel.
1361	
1362		ihash_entries=	[KNL]
1363				Set number of hash buckets for inode cache.
1364	
1365		ima_appraise=	[IMA] appraise integrity measurements
1366				Format: { "off" | "enforce" | "fix" | "log" }
1367				default: "enforce"
1368	
1369		ima_appraise_tcb [IMA]
1370				The builtin appraise policy appraises all files
1371				owned by uid=0.
1372	
1373		ima_hash=	[IMA]
1374				Format: { md5 | sha1 | rmd160 | sha256 | sha384
1375					   | sha512 | ... }
1376				default: "sha1"
1377	
1378				The list of supported hash algorithms is defined
1379				in crypto/hash_info.h.
1380	
1381		ima_tcb		[IMA]
1382				Load a policy which meets the needs of the Trusted
1383				Computing Base.  This means IMA will measure all
1384				programs exec'd, files mmap'd for exec, and all files
1385				opened for read by uid=0.
1386	
1387		ima_template=   [IMA]
1388				Select one of defined IMA measurements template formats.
1389				Formats: { "ima" | "ima-ng" }
1390				Default: "ima-ng"
1391	
1392		ima_template_fmt=
1393		                [IMA] Define a custom template format.
1394				Format: { "field1|...|fieldN" }
1395	
1396		ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1397				Format: <min_file_size>
1398				Set the minimal file size for using asynchronous hash.
1399				If left unspecified, ahash usage is disabled.
1400	
1401				ahash performance varies for different data sizes on
1402				different crypto accelerators. This option can be used
1403				to achieve the best performance for a particular HW.
1404	
1405		ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1406				Format: <bufsize>
1407				Set hashing buffer size. Default: 4k.
1408	
1409				ahash performance varies for different chunk sizes on
1410				different crypto accelerators. This option can be used
1411				to achieve best performance for particular HW.
1412	
1413		init=		[KNL]
1414				Format: <full_path>
1415				Run specified binary instead of /sbin/init as init
1416				process.
1417	
1418		initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
1419				for working out where the kernel is dying during
1420				startup.
1421	
1422		initcall_blacklist=  [KNL] Do not execute a comma-separated list of
1423				initcall functions.  Useful for debugging built-in
1424				modules and initcalls.
1425	
1426		initrd=		[BOOT] Specify the location of the initial ramdisk
1427	
1428		inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
1429				Format: <irq>
1430	
1431		int_pln_enable  [x86] Enable power limit notification interrupt
1432	
1433		integrity_audit=[IMA]
1434				Format: { "0" | "1" }
1435				0 -- basic integrity auditing messages. (Default)
1436				1 -- additional integrity auditing messages.
1437	
1438		intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1439			on
1440				Enable intel iommu driver.
1441			off
1442				Disable intel iommu driver.
1443			igfx_off [Default Off]
1444				By default, gfx is mapped as normal device. If a gfx
1445				device has a dedicated DMAR unit, the DMAR unit is
1446				bypassed by not enabling DMAR with this option. In
1447				this case, gfx device will use physical address for
1448				DMA.
1449			forcedac [x86_64]
1450				With this option iommu will not optimize to look
1451				for io virtual address below 32-bit forcing dual
1452				address cycle on pci bus for cards supporting greater
1453				than 32-bit addressing. The default is to look
1454				for translation below 32-bit and if not available
1455				then look in the higher range.
1456			strict [Default Off]
1457				With this option on every unmap_single operation will
1458				result in a hardware IOTLB flush operation as opposed
1459				to batching them for performance.
1460			sp_off [Default Off]
1461				By default, super page will be supported if Intel IOMMU
1462				has the capability. With this option, super page will
1463				not be supported.
1464	
1465		intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
1466				0	disables intel_idle and fall back on acpi_idle.
1467				1 to 6	specify maximum depth of C-state.
1468	
1469		intel_pstate=  [X86]
1470			       disable
1471			         Do not enable intel_pstate as the default
1472			         scaling driver for the supported processors
1473			       force
1474				 Enable intel_pstate on systems that prohibit it by default
1475				 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1476				 instead of acpi-cpufreq may disable platform features, such
1477				 as thermal controls and power capping, that rely on ACPI
1478				 P-States information being indicated to OSPM and therefore
1479				 should be used with caution. This option does not work with
1480				 processors that aren't supported by the intel_pstate driver
1481				 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1482			       no_hwp
1483			         Do not enable hardware P state control (HWP)
1484				 if available.
1485			hwp_only
1486				Only load intel_pstate on systems which support
1487				hardware P state control (HWP) if available.
1488	
1489		intremap=	[X86-64, Intel-IOMMU]
1490				on	enable Interrupt Remapping (default)
1491				off	disable Interrupt Remapping
1492				nosid	disable Source ID checking
1493				no_x2apic_optout
1494					BIOS x2APIC opt-out request will be ignored
1495	
1496		iomem=		Disable strict checking of access to MMIO memory
1497			strict	regions from userspace.
1498			relaxed
1499	
1500		iommu=		[x86]
1501			off
1502			force
1503			noforce
1504			biomerge
1505			panic
1506			nopanic
1507			merge
1508			nomerge
1509			forcesac
1510			soft
1511			pt		[x86, IA-64]
1512			nobypass	[PPC/POWERNV]
1513				Disable IOMMU bypass, using IOMMU for PCI devices.
1514	
1515	
1516		io7=		[HW] IO7 for Marvel based alpha systems
1517				See comment before marvel_specify_io7 in
1518				arch/alpha/kernel/core_marvel.c.
1519	
1520		io_delay=	[X86] I/O delay method
1521			0x80
1522				Standard port 0x80 based delay
1523			0xed
1524				Alternate port 0xed based delay (needed on some systems)
1525			udelay
1526				Simple two microseconds delay
1527			none
1528				No delay
1529	
1530		ip=		[IP_PNP]
1531				See Documentation/filesystems/nfs/nfsroot.txt.
1532	
1533		irqfixup	[HW]
1534				When an interrupt is not handled search all handlers
1535				for it. Intended to get systems with badly broken
1536				firmware running.
1537	
1538		irqpoll		[HW]
1539				When an interrupt is not handled search all handlers
1540				for it. Also check all handlers each timer
1541				interrupt. Intended to get systems with badly broken
1542				firmware running.
1543	
1544		isapnp=		[ISAPNP]
1545				Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1546	
1547		isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
1548				Format:
1549				<cpu number>,...,<cpu number>
1550				or
1551				<cpu number>-<cpu number>
1552				(must be a positive range in ascending order)
1553				or a mixture
1554				<cpu number>,...,<cpu number>-<cpu number>
1555	
1556				This option can be used to specify one or more CPUs
1557				to isolate from the general SMP balancing and scheduling
1558				algorithms. You can move a process onto or off an
1559				"isolated" CPU via the CPU affinity syscalls or cpuset.
1560				<cpu number> begins at 0 and the maximum value is
1561				"number of CPUs in system - 1".
1562	
1563				This option is the preferred way to isolate CPUs. The
1564				alternative -- manually setting the CPU mask of all
1565				tasks in the system -- can cause problems and
1566				suboptimal load balancer performance.
1567	
1568		iucv=		[HW,NET]
1569	
1570		ivrs_ioapic	[HW,X86_64]
1571				Provide an override to the IOAPIC-ID<->DEVICE-ID
1572				mapping provided in the IVRS ACPI table. For
1573				example, to map IOAPIC-ID decimal 10 to
1574				PCI device 00:14.0 write the parameter as:
1575					ivrs_ioapic[10]=00:14.0
1576	
1577		ivrs_hpet	[HW,X86_64]
1578				Provide an override to the HPET-ID<->DEVICE-ID
1579				mapping provided in the IVRS ACPI table. For
1580				example, to map HPET-ID decimal 0 to
1581				PCI device 00:14.0 write the parameter as:
1582					ivrs_hpet[0]=00:14.0
1583	
1584		js=		[HW,JOY] Analog joystick
1585				See Documentation/input/joystick.txt.
1586	
1587		kaslr/nokaslr	[X86]
1588				Enable/disable kernel and module base offset ASLR
1589				(Address Space Layout Randomization) if built into
1590				the kernel. When CONFIG_HIBERNATION is selected,
1591				kASLR is disabled by default. When kASLR is enabled,
1592				hibernation will be disabled.
1593	
1594		keepinitrd	[HW,ARM]
1595	
1596		kernelcore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
1597				specifies the amount of memory usable by the kernel
1598				for non-movable allocations.  The requested amount is
1599				spread evenly throughout all nodes in the system. The
1600				remaining memory in each node is used for Movable
1601				pages. In the event, a node is too small to have both
1602				kernelcore and Movable pages, kernelcore pages will
1603				take priority and other nodes will have a larger number
1604				of Movable pages.  The Movable zone is used for the
1605				allocation of pages that may be reclaimed or moved
1606				by the page migration subsystem.  This means that
1607				HugeTLB pages may not be allocated from this zone.
1608				Note that allocations like PTEs-from-HighMem still
1609				use the HighMem zone if it exists, and the Normal
1610				zone if it does not.
1611	
1612		kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
1613				Format: <Controller#>[,poll interval]
1614				The controller # is the number of the ehci usb debug
1615				port as it is probed via PCI.  The poll interval is
1616				optional and is the number seconds in between
1617				each poll cycle to the debug port in case you need
1618				the functionality for interrupting the kernel with
1619				gdb or control-c on the dbgp connection.  When
1620				not using this parameter you use sysrq-g to break into
1621				the kernel debugger.
1622	
1623		kgdboc=		[KGDB,HW] kgdb over consoles.
1624				Requires a tty driver that supports console polling,
1625				or a supported polling keyboard driver (non-usb).
1626				 Serial only format: <serial_device>[,baud]
1627				 keyboard only format: kbd
1628				 keyboard and serial format: kbd,<serial_device>[,baud]
1629				Optional Kernel mode setting:
1630				 kms, kbd format: kms,kbd
1631				 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1632	
1633		kgdbwait	[KGDB] Stop kernel execution and enter the
1634				kernel debugger at the earliest opportunity.
1635	
1636		kmac=		[MIPS] korina ethernet MAC address.
1637				Configure the RouterBoard 532 series on-chip
1638				Ethernet adapter MAC address.
1639	
1640		kmemleak=	[KNL] Boot-time kmemleak enable/disable
1641				Valid arguments: on, off
1642				Default: on
1643				Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1644				the default is off.
1645	
1646		kmemcheck=	[X86] Boot-time kmemcheck enable/disable/one-shot mode
1647				Valid arguments: 0, 1, 2
1648				kmemcheck=0 (disabled)
1649				kmemcheck=1 (enabled)
1650				kmemcheck=2 (one-shot mode)
1651				Default: 2 (one-shot mode)
1652	
1653		kstack=N	[X86] Print N words from the kernel stack
1654				in oops dumps.
1655	
1656		kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1657				Default is 0 (don't ignore, but inject #GP)
1658	
1659		kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
1660				KVM MMU at runtime.
1661				Default is 0 (off)
1662	
1663		kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
1664				Default is 1 (enabled)
1665	
1666		kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
1667				for all guests.
1668				Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1669	
1670		kvm-intel.ept=	[KVM,Intel] Disable extended page tables
1671				(virtualized MMU) support on capable Intel chips.
1672				Default is 1 (enabled)
1673	
1674		kvm-intel.emulate_invalid_guest_state=
1675				[KVM,Intel] Enable emulation of invalid guest states
1676				Default is 0 (disabled)
1677	
1678		kvm-intel.flexpriority=
1679				[KVM,Intel] Disable FlexPriority feature (TPR shadow).
1680				Default is 1 (enabled)
1681	
1682		kvm-intel.nested=
1683				[KVM,Intel] Enable VMX nesting (nVMX).
1684				Default is 0 (disabled)
1685	
1686		kvm-intel.unrestricted_guest=
1687				[KVM,Intel] Disable unrestricted guest feature
1688				(virtualized real and unpaged mode) on capable
1689				Intel chips. Default is 1 (enabled)
1690	
1691		kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
1692				feature (tagged TLBs) on capable Intel chips.
1693				Default is 1 (enabled)
1694	
1695		l2cr=		[PPC]
1696	
1697		l3cr=		[PPC]
1698	
1699		lapic		[X86-32,APIC] Enable the local APIC even if BIOS
1700				disabled it.
1701	
1702		lapic=		[x86,APIC] "notscdeadline" Do not use TSC deadline
1703				value for LAPIC timer one-shot implementation. Default
1704				back to the programmable timer unit in the LAPIC.
1705	
1706		lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
1707				in C2 power state.
1708	
1709		libata.dma=	[LIBATA] DMA control
1710				libata.dma=0	  Disable all PATA and SATA DMA
1711				libata.dma=1	  PATA and SATA Disk DMA only
1712				libata.dma=2	  ATAPI (CDROM) DMA only
1713				libata.dma=4	  Compact Flash DMA only
1714				Combinations also work, so libata.dma=3 enables DMA
1715				for disks and CDROMs, but not CFs.
1716	
1717		libata.ignore_hpa=	[LIBATA] Ignore HPA limit
1718				libata.ignore_hpa=0	  keep BIOS limits (default)
1719				libata.ignore_hpa=1	  ignore limits, using full disk
1720	
1721		libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
1722				when set.
1723				Format: <int>
1724	
1725		libata.force=	[LIBATA] Force configurations.  The format is comma
1726				separated list of "[ID:]VAL" where ID is
1727				PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1728				matching port, link or device.  Basically, it matches
1729				the ATA ID string printed on console by libata.  If
1730				the whole ID part is omitted, the last PORT and DEVICE
1731				values are used.  If ID hasn't been specified yet, the
1732				configuration applies to all ports, links and devices.
1733	
1734				If only DEVICE is omitted, the parameter applies to
1735				the port and all links and devices behind it.  DEVICE
1736				number of 0 either selects the first device or the
1737				first fan-out link behind PMP device.  It does not
1738				select the host link.  DEVICE number of 15 selects the
1739				host link and device attached to it.
1740	
1741				The VAL specifies the configuration to force.  As long
1742				as there's no ambiguity shortcut notation is allowed.
1743				For example, both 1.5 and 1.5G would work for 1.5Gbps.
1744				The following configurations can be forced.
1745	
1746				* Cable type: 40c, 80c, short40c, unk, ign or sata.
1747				  Any ID with matching PORT is used.
1748	
1749				* SATA link speed limit: 1.5Gbps or 3.0Gbps.
1750	
1751				* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1752				  udma[/][16,25,33,44,66,100,133] notation is also
1753				  allowed.
1754	
1755				* [no]ncq: Turn on or off NCQ.
1756	
1757				* nohrst, nosrst, norst: suppress hard, soft
1758	                          and both resets.
1759	
1760				* rstonce: only attempt one reset during
1761				  hot-unplug link recovery
1762	
1763				* dump_id: dump IDENTIFY data.
1764	
1765				* atapi_dmadir: Enable ATAPI DMADIR bridge support
1766	
1767				* disable: Disable this device.
1768	
1769				If there are multiple matching configurations changing
1770				the same attribute, the last one is used.
1771	
1772		memblock=debug	[KNL] Enable memblock debug messages.
1773	
1774		load_ramdisk=	[RAM] List of ramdisks to load from floppy
1775				See Documentation/blockdev/ramdisk.txt.
1776	
1777		lockd.nlm_grace_period=P  [NFS] Assign grace period.
1778				Format: <integer>
1779	
1780		lockd.nlm_tcpport=N	[NFS] Assign TCP port.
1781				Format: <integer>
1782	
1783		lockd.nlm_timeout=T	[NFS] Assign timeout value.
1784				Format: <integer>
1785	
1786		lockd.nlm_udpport=M	[NFS] Assign UDP port.
1787				Format: <integer>
1788	
1789		locktorture.nreaders_stress= [KNL]
1790				Set the number of locking read-acquisition kthreads.
1791				Defaults to being automatically set based on the
1792				number of online CPUs.
1793	
1794		locktorture.nwriters_stress= [KNL]
1795				Set the number of locking write-acquisition kthreads.
1796	
1797		locktorture.onoff_holdoff= [KNL]
1798				Set time (s) after boot for CPU-hotplug testing.
1799	
1800		locktorture.onoff_interval= [KNL]
1801				Set time (s) between CPU-hotplug operations, or
1802				zero to disable CPU-hotplug testing.
1803	
1804		locktorture.shuffle_interval= [KNL]
1805				Set task-shuffle interval (jiffies).  Shuffling
1806				tasks allows some CPUs to go into dyntick-idle
1807				mode during the locktorture test.
1808	
1809		locktorture.shutdown_secs= [KNL]
1810				Set time (s) after boot system shutdown.  This
1811				is useful for hands-off automated testing.
1812	
1813		locktorture.stat_interval= [KNL]
1814				Time (s) between statistics printk()s.
1815	
1816		locktorture.stutter= [KNL]
1817				Time (s) to stutter testing, for example,
1818				specifying five seconds causes the test to run for
1819				five seconds, wait for five seconds, and so on.
1820				This tests the locking primitive's ability to
1821				transition abruptly to and from idle.
1822	
1823		locktorture.torture_runnable= [BOOT]
1824				Start locktorture running at boot time.
1825	
1826		locktorture.torture_type= [KNL]
1827				Specify the locking implementation to test.
1828	
1829		locktorture.verbose= [KNL]
1830				Enable additional printk() statements.
1831	
1832		logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
1833				Format: <irq>
1834	
1835		loglevel=	All Kernel Messages with a loglevel smaller than the
1836				console loglevel will be printed to the console. It can
1837				also be changed with klogd or other programs. The
1838				loglevels are defined as follows:
1839	
1840				0 (KERN_EMERG)		system is unusable
1841				1 (KERN_ALERT)		action must be taken immediately
1842				2 (KERN_CRIT)		critical conditions
1843				3 (KERN_ERR)		error conditions
1844				4 (KERN_WARNING)	warning conditions
1845				5 (KERN_NOTICE)		normal but significant condition
1846				6 (KERN_INFO)		informational
1847				7 (KERN_DEBUG)		debug-level messages
1848	
1849		log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
1850				in bytes.  n must be a power of two and greater
1851				than the minimal size. The minimal size is defined
1852				by LOG_BUF_SHIFT kernel config parameter. There is
1853				also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1854				that allows to increase the default size depending on
1855				the number of CPUs. See init/Kconfig for more details.
1856	
1857		logo.nologo	[FB] Disables display of the built-in Linux logo.
1858				This may be used to provide more screen space for
1859				kernel log messages and is useful when debugging
1860				kernel boot problems.
1861	
1862		lp=0		[LP]	Specify parallel ports to use, e.g,
1863		lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
1864		lp=reset		first parallel port). 'lp=0' disables the
1865		lp=auto			printer driver. 'lp=reset' (which can be
1866					specified in addition to the ports) causes
1867					attached printers to be reset. Using
1868					lp=port1,port2,... specifies the parallel ports
1869					to associate lp devices with, starting with
1870					lp0. A port specification may be 'none' to skip
1871					that lp device, or a parport name such as
1872					'parport0'. Specifying 'lp=auto' instead of a
1873					port specification list means that device IDs
1874					from each port should be examined, to see if
1875					an IEEE 1284-compliant printer is attached; if
1876					so, the driver will manage that printer.
1877					See also header of drivers/char/lp.c.
1878	
1879		lpj=n		[KNL]
1880				Sets loops_per_jiffy to given constant, thus avoiding
1881				time-consuming boot-time autodetection (up to 250 ms per
1882				CPU). 0 enables autodetection (default). To determine
1883				the correct value for your kernel, boot with normal
1884				autodetection and see what value is printed. Note that
1885				on SMP systems the preset will be applied to all CPUs,
1886				which is likely to cause problems if your CPUs need
1887				significantly divergent settings. An incorrect value
1888				will cause delays in the kernel to be wrong, leading to
1889				unpredictable I/O errors and other breakage. Although
1890				unlikely, in the extreme case this might damage your
1891				hardware.
1892	
1893		ltpc=		[NET]
1894				Format: <io>,<irq>,<dma>
1895	
1896		machvec=	[IA-64] Force the use of a particular machine-vector
1897				(machvec) in a generic kernel.
1898				Example: machvec=hpzx1_swiotlb
1899	
1900		machtype=	[Loongson] Share the same kernel image file between different
1901				 yeeloong laptop.
1902				Example: machtype=lemote-yeeloong-2f-7inch
1903	
1904		max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
1905				than or equal to this physical address is ignored.
1906	
1907		maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
1908				should make use of.  maxcpus=n : n >= 0 limits the
1909				kernel to using 'n' processors.  n=0 is a special case,
1910				it is equivalent to "nosmp", which also disables
1911				the IO APIC.
1912	
1913		max_loop=	[LOOP] The number of loop block devices that get
1914		(loop.max_loop)	unconditionally pre-created at init time. The default
1915				number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1916				of statically allocating a predefined number, loop
1917				devices can be requested on-demand with the
1918				/dev/loop-control interface.
1919	
1920		mce		[X86-32] Machine Check Exception
1921	
1922		mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
1923	
1924		md=		[HW] RAID subsystems devices and level
1925				See Documentation/md.txt.
1926	
1927		mdacon=		[MDA]
1928				Format: <first>,<last>
1929				Specifies range of consoles to be captured by the MDA.
1930	
1931		mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
1932				Amount of memory to be used when the kernel is not able
1933				to see the whole system memory or for test.
1934				[X86] Work as limiting max address. Use together
1935				with memmap= to avoid physical address space collisions.
1936				Without memmap= PCI devices could be placed at addresses
1937				belonging to unused RAM.
1938	
1939		mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
1940				memory.
1941	
1942		memchunk=nn[KMG]
1943				[KNL,SH] Allow user to override the default size for
1944				per-device physically contiguous DMA buffers.
1945	
1946		memmap=exactmap	[KNL,X86] Enable setting of an exact
1947				E820 memory map, as specified by the user.
1948				Such memmap=exactmap lines can be constructed based on
1949				BIOS output or other requirements. See the memmap=nn@ss
1950				option description.
1951	
1952		memmap=nn[KMG]@ss[KMG]
1953				[KNL] Force usage of a specific region of memory.
1954				Region of memory to be used is from ss to ss+nn.
1955	
1956		memmap=nn[KMG]#ss[KMG]
1957				[KNL,ACPI] Mark specific memory as ACPI data.
1958				Region of memory to be marked is from ss to ss+nn.
1959	
1960		memmap=nn[KMG]$ss[KMG]
1961				[KNL,ACPI] Mark specific memory as reserved.
1962				Region of memory to be reserved is from ss to ss+nn.
1963				Example: Exclude memory from 0x18690000-0x1869ffff
1964				         memmap=64K$0x18690000
1965				         or
1966				         memmap=0x10000$0x18690000
1967	
1968		memory_corruption_check=0/1 [X86]
1969				Some BIOSes seem to corrupt the first 64k of
1970				memory when doing things like suspend/resume.
1971				Setting this option will scan the memory
1972				looking for corruption.  Enabling this will
1973				both detect corruption and prevent the kernel
1974				from using the memory being corrupted.
1975				However, its intended as a diagnostic tool; if
1976				repeatable BIOS-originated corruption always
1977				affects the same memory, you can use memmap=
1978				to prevent the kernel from using that memory.
1979	
1980		memory_corruption_check_size=size [X86]
1981				By default it checks for corruption in the low
1982				64k, making this memory unavailable for normal
1983				use.  Use this parameter to scan for
1984				corruption in more or less memory.
1985	
1986		memory_corruption_check_period=seconds [X86]
1987				By default it checks for corruption every 60
1988				seconds.  Use this parameter to check at some
1989				other rate.  0 disables periodic checking.
1990	
1991		memtest=	[KNL,X86] Enable memtest
1992				Format: <integer>
1993				default : 0 <disable>
1994				Specifies the number of memtest passes to be
1995				performed. Each pass selects another test
1996				pattern from a given set of patterns. Memtest
1997				fills the memory with this pattern, validates
1998				memory contents and reserves bad memory
1999				regions that are detected.
2000	
2001		meye.*=		[HW] Set MotionEye Camera parameters
2002				See Documentation/video4linux/meye.txt.
2003	
2004		mfgpt_irq=	[IA-32] Specify the IRQ to use for the
2005				Multi-Function General Purpose Timers on AMD Geode
2006				platforms.
2007	
2008		mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
2009				the BIOS has incorrectly applied a workaround. TinyBIOS
2010				version 0.98 is known to be affected, 0.99 fixes the
2011				problem by letting the user disable the workaround.
2012	
2013		mga=		[HW,DRM]
2014	
2015		min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
2016				physical address is ignored.
2017	
2018		mini2440=	[ARM,HW,KNL]
2019				Format:[0..2][b][c][t]
2020				Default: "0tb"
2021				MINI2440 configuration specification:
2022				0 - The attached screen is the 3.5" TFT
2023				1 - The attached screen is the 7" TFT
2024				2 - The VGA Shield is attached (1024x768)
2025				Leaving out the screen size parameter will not load
2026				the TFT driver, and the framebuffer will be left
2027				unconfigured.
2028				b - Enable backlight. The TFT backlight pin will be
2029				linked to the kernel VESA blanking code and a GPIO
2030				LED. This parameter is not necessary when using the
2031				VGA shield.
2032				c - Enable the s3c camera interface.
2033				t - Reserved for enabling touchscreen support. The
2034				touchscreen support is not enabled in the mainstream
2035				kernel as of 2.6.30, a preliminary port can be found
2036				in the "bleeding edge" mini2440 support kernel at
2037				http://repo.or.cz/w/linux-2.6/mini2440.git
2038	
2039		mminit_loglevel=
2040				[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2041				parameter allows control of the logging verbosity for
2042				the additional memory initialisation checks. A value
2043				of 0 disables mminit logging and a level of 4 will
2044				log everything. Information is printed at KERN_DEBUG
2045				so loglevel=8 may also need to be specified.
2046	
2047		module.sig_enforce
2048				[KNL] When CONFIG_MODULE_SIG is set, this means that
2049				modules without (valid) signatures will fail to load.
2050				Note that if CONFIG_MODULE_SIG_FORCE is set, that
2051				is always true, so this option does nothing.
2052	
2053		mousedev.tap_time=
2054				[MOUSE] Maximum time between finger touching and
2055				leaving touchpad surface for touch to be considered
2056				a tap and be reported as a left button click (for
2057				touchpads working in absolute mode only).
2058				Format: <msecs>
2059		mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
2060				reporting absolute coordinates, such as tablets
2061		mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
2062				reporting absolute coordinates, such as tablets
2063	
2064		movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
2065				is similar to kernelcore except it specifies the
2066				amount of memory used for migratable allocations.
2067				If both kernelcore and movablecore is specified,
2068				then kernelcore will be at *least* the specified
2069				value but may be more. If movablecore on its own
2070				is specified, the administrator must be careful
2071				that the amount of memory usable for all allocations
2072				is not too small.
2073	
2074		movable_node	[KNL,X86] Boot-time switch to enable the effects
2075				of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2076	
2077		MTD_Partition=	[MTD]
2078				Format: <name>,<region-number>,<size>,<offset>
2079	
2080		MTD_Region=	[MTD] Format:
2081				<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2082	
2083		mtdparts=	[MTD]
2084				See drivers/mtd/cmdlinepart.c.
2085	
2086		multitce=off	[PPC]  This parameter disables the use of the pSeries
2087				firmware feature for updating multiple TCE entries
2088				at a time.
2089	
2090		onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
2091	
2092				Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2093	
2094				boundary - index of last SLC block on Flex-OneNAND.
2095					   The remaining blocks are configured as MLC blocks.
2096				lock	 - Configure if Flex-OneNAND boundary should be locked.
2097					   Once locked, the boundary cannot be changed.
2098					   1 indicates lock status, 0 indicates unlock status.
2099	
2100		mtdset=		[ARM]
2101				ARM/S3C2412 JIVE boot control
2102	
2103				See arch/arm/mach-s3c2412/mach-jive.c
2104	
2105		mtouchusb.raw_coordinates=
2106				[HW] Make the MicroTouch USB driver use raw coordinates
2107				('y', default) or cooked coordinates ('n')
2108	
2109		mtrr_chunk_size=nn[KMG] [X86]
2110				used for mtrr cleanup. It is largest continuous chunk
2111				that could hold holes aka. UC entries.
2112	
2113		mtrr_gran_size=nn[KMG] [X86]
2114				Used for mtrr cleanup. It is granularity of mtrr block.
2115				Default is 1.
2116				Large value could prevent small alignment from
2117				using up MTRRs.
2118	
2119		mtrr_spare_reg_nr=n [X86]
2120				Format: <integer>
2121				Range: 0,7 : spare reg number
2122				Default : 1
2123				Used for mtrr cleanup. It is spare mtrr entries number.
2124				Set to 2 or more if your graphical card needs more.
2125	
2126		n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
2127	
2128		netdev=		[NET] Network devices parameters
2129				Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2130				Note that mem_start is often overloaded to mean
2131				something different and driver-specific.
2132				This usage is only documented in each driver source
2133				file if at all.
2134	
2135		nf_conntrack.acct=
2136				[NETFILTER] Enable connection tracking flow accounting
2137				0 to disable accounting
2138				1 to enable accounting
2139				Default value is 0.
2140	
2141		nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
2142				See Documentation/filesystems/nfs/nfsroot.txt.
2143	
2144		nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
2145				See Documentation/filesystems/nfs/nfsroot.txt.
2146	
2147		nfsrootdebug	[NFS] enable nfsroot debugging messages.
2148				See Documentation/filesystems/nfs/nfsroot.txt.
2149	
2150		nfs.callback_tcpport=
2151				[NFS] set the TCP port on which the NFSv4 callback
2152				channel should listen.
2153	
2154		nfs.cache_getent=
2155				[NFS] sets the pathname to the program which is used
2156				to update the NFS client cache entries.
2157	
2158		nfs.cache_getent_timeout=
2159				[NFS] sets the timeout after which an attempt to
2160				update a cache entry is deemed to have failed.
2161	
2162		nfs.idmap_cache_timeout=
2163				[NFS] set the maximum lifetime for idmapper cache
2164				entries.
2165	
2166		nfs.enable_ino64=
2167				[NFS] enable 64-bit inode numbers.
2168				If zero, the NFS client will fake up a 32-bit inode
2169				number for the readdir() and stat() syscalls instead
2170				of returning the full 64-bit number.
2171				The default is to return 64-bit inode numbers.
2172	
2173		nfs.max_session_slots=
2174				[NFSv4.1] Sets the maximum number of session slots
2175				the client will attempt to negotiate with the server.
2176				This limits the number of simultaneous RPC requests
2177				that the client can send to the NFSv4.1 server.
2178				Note that there is little point in setting this
2179				value higher than the max_tcp_slot_table_limit.
2180	
2181		nfs.nfs4_disable_idmapping=
2182				[NFSv4] When set to the default of '1', this option
2183				ensures that both the RPC level authentication
2184				scheme and the NFS level operations agree to use
2185				numeric uids/gids if the mount is using the
2186				'sec=sys' security flavour. In effect it is
2187				disabling idmapping, which can make migration from
2188				legacy NFSv2/v3 systems to NFSv4 easier.
2189				Servers that do not support this mode of operation
2190				will be autodetected by the client, and it will fall
2191				back to using the idmapper.
2192				To turn off this behaviour, set the value to '0'.
2193		nfs.nfs4_unique_id=
2194				[NFS4] Specify an additional fixed unique ident-
2195				ification string that NFSv4 clients can insert into
2196				their nfs_client_id4 string.  This is typically a
2197				UUID that is generated at system install time.
2198	
2199		nfs.send_implementation_id =
2200				[NFSv4.1] Send client implementation identification
2201				information in exchange_id requests.
2202				If zero, no implementation identification information
2203				will be sent.
2204				The default is to send the implementation identification
2205				information.
2206		
2207		nfs.recover_lost_locks =
2208				[NFSv4] Attempt to recover locks that were lost due
2209				to a lease timeout on the server. Please note that
2210				doing this risks data corruption, since there are
2211				no guarantees that the file will remain unchanged
2212				after the locks are lost.
2213				If you want to enable the kernel legacy behaviour of
2214				attempting to recover these locks, then set this
2215				parameter to '1'.
2216				The default parameter value of '0' causes the kernel
2217				not to attempt recovery of lost locks.
2218	
2219		nfsd.nfs4_disable_idmapping=
2220				[NFSv4] When set to the default of '1', the NFSv4
2221				server will return only numeric uids and gids to
2222				clients using auth_sys, and will accept numeric uids
2223				and gids from such clients.  This is intended to ease
2224				migration from NFSv2/v3.
2225	
2226		objlayoutdriver.osd_login_prog=
2227				[NFS] [OBJLAYOUT] sets the pathname to the program which
2228				is used to automatically discover and login into new
2229				osd-targets. Please see:
2230				Documentation/filesystems/pnfs.txt for more explanations
2231	
2232		nmi_debug=	[KNL,AVR32,SH] Specify one or more actions to take
2233				when a NMI is triggered.
2234				Format: [state][,regs][,debounce][,die]
2235	
2236		nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
2237				Format: [panic,][nopanic,][num]
2238				Valid num: 0
2239				0 - turn nmi_watchdog off
2240				When panic is specified, panic when an NMI watchdog
2241				timeout occurs (or 'nopanic' to override the opposite
2242				default).
2243				This is useful when you use a panic=... timeout and
2244				need the box quickly up again.
2245	
2246		netpoll.carrier_timeout=
2247				[NET] Specifies amount of time (in seconds) that
2248				netpoll should wait for a carrier. By default netpoll
2249				waits 4 seconds.
2250	
2251		no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
2252				emulation library even if a 387 maths coprocessor
2253				is present.
2254	
2255		no_console_suspend
2256				[HW] Never suspend the console
2257				Disable suspending of consoles during suspend and
2258				hibernate operations.  Once disabled, debugging
2259				messages can reach various consoles while the rest
2260				of the system is being put to sleep (ie, while
2261				debugging driver suspend/resume hooks).  This may
2262				not work reliably with all consoles, but is known
2263				to work with serial and VGA consoles.
2264				To facilitate more flexible debugging, we also add
2265				console_suspend, a printk module parameter to control
2266				it. Users could use console_suspend (usually
2267				/sys/module/printk/parameters/console_suspend) to
2268				turn on/off it dynamically.
2269	
2270		noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
2271				caches in the slab allocator.  Saves per-node memory,
2272				but will impact performance.
2273	
2274		noalign		[KNL,ARM]
2275	
2276		noapic		[SMP,APIC] Tells the kernel to not make use of any
2277				IOAPICs that may be present in the system.
2278	
2279		noautogroup	Disable scheduler automatic task group creation.
2280	
2281		nobats		[PPC] Do not use BATs for mapping kernel lowmem
2282				on "Classic" PPC cores.
2283	
2284		nocache		[ARM]
2285	
2286		noclflush	[BUGS=X86] Don't use the CLFLUSH instruction
2287	
2288		nodelayacct	[KNL] Disable per-task delay accounting
2289	
2290		nodisconnect	[HW,SCSI,M68K] Disables SCSI disconnects.
2291	
2292		nodsp		[SH] Disable hardware DSP at boot time.
2293	
2294		noefi		Disable EFI runtime services support.
2295	
2296		noexec		[IA-64]
2297	
2298		noexec		[X86]
2299				On X86-32 available only on PAE configured kernels.
2300				noexec=on: enable non-executable mappings (default)
2301				noexec=off: disable non-executable mappings
2302	
2303		nosmap		[X86]
2304				Disable SMAP (Supervisor Mode Access Prevention)
2305				even if it is supported by processor.
2306	
2307		nosmep		[X86]
2308				Disable SMEP (Supervisor Mode Execution Prevention)
2309				even if it is supported by processor.
2310	
2311		noexec32	[X86-64]
2312				This affects only 32-bit executables.
2313				noexec32=on: enable non-executable mappings (default)
2314					read doesn't imply executable mappings
2315				noexec32=off: disable non-executable mappings
2316					read implies executable mappings
2317	
2318		nofpu		[SH] Disable hardware FPU at boot time.
2319	
2320		nofxsr		[BUGS=X86-32] Disables x86 floating point extended
2321				register save and restore. The kernel will only save
2322				legacy floating-point registers on task switch.
2323	
2324		noxsave		[BUGS=X86] Disables x86 extended register state save
2325				and restore using xsave. The kernel will fallback to
2326				enabling legacy floating-point and sse state.
2327	
2328		noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
2329				register states. The kernel will fall back to use
2330				xsave to save the states. By using this parameter,
2331				performance of saving the states is degraded because
2332				xsave doesn't support modified optimization while
2333				xsaveopt supports it on xsaveopt enabled systems.
2334	
2335		noxsaves	[X86] Disables xsaves and xrstors used in saving and
2336				restoring x86 extended register state in compacted
2337				form of xsave area. The kernel will fall back to use
2338				xsaveopt and xrstor to save and restore the states
2339				in standard form of xsave area. By using this
2340				parameter, xsave area per process might occupy more
2341				memory on xsaves enabled systems.
2342	
2343		eagerfpu=	[X86]
2344				on	enable eager fpu restore
2345				off	disable eager fpu restore
2346				auto	selects the default scheme, which automatically
2347					enables eagerfpu restore for xsaveopt.
2348	
2349		nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2350				wfi(ARM) instruction doesn't work correctly and not to
2351				use it. This is also useful when using JTAG debugger.
2352	
2353		no_file_caps	Tells the kernel not to honor file capabilities.  The
2354				only way then for a file to be executed with privilege
2355				is to be setuid root or executed by root.
2356	
2357		nohalt		[IA-64] Tells the kernel not to use the power saving
2358				function PAL_HALT_LIGHT when idle. This increases
2359				power-consumption. On the positive side, it reduces
2360				interrupt wake-up latency, which may improve performance
2361				in certain environments such as networked servers or
2362				real-time systems.
2363	
2364		nohibernate	[HIBERNATION] Disable hibernation and resume.
2365	
2366		nohz=		[KNL] Boottime enable/disable dynamic ticks
2367				Valid arguments: on, off
2368				Default: on
2369	
2370		nohz_full=	[KNL,BOOT]
2371				In kernels built with CONFIG_NO_HZ_FULL=y, set
2372				the specified list of CPUs whose tick will be stopped
2373				whenever possible. The boot CPU will be forced outside
2374				the range to maintain the timekeeping.
2375				The CPUs in this range must also be included in the
2376				rcu_nocbs= set.
2377	
2378		noiotrap	[SH] Disables trapped I/O port accesses.
2379	
2380		noirqdebug	[X86-32] Disables the code which attempts to detect and
2381				disable unhandled interrupt sources.
2382	
2383		no_timer_check	[X86,APIC] Disables the code which tests for
2384				broken timer IRQ sources.
2385	
2386		noisapnp	[ISAPNP] Disables ISA PnP code.
2387	
2388		noinitrd	[RAM] Tells the kernel not to load any configured
2389				initial RAM disk.
2390	
2391		nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
2392				remapping.
2393				[Deprecated - use intremap=off]
2394	
2395		nointroute	[IA-64]
2396	
2397		nojitter	[IA-64] Disables jitter checking for ITC timers.
2398	
2399		no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
2400	
2401		no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
2402				fault handling.
2403	
2404		no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
2405				steal time is computed, but won't influence scheduler
2406				behaviour
2407	
2408		nolapic		[X86-32,APIC] Do not enable or use the local APIC.
2409	
2410		nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
2411	
2412		noltlbs		[PPC] Do not use large page/tlb entries for kernel
2413				lowmem mapping on PPC40x.
2414	
2415		nomca		[IA-64] Disable machine check abort handling
2416	
2417		nomce		[X86-32] Machine Check Exception
2418	
2419		nomfgpt		[X86-32] Disable Multi-Function General Purpose
2420				Timer usage (for AMD Geode machines).
2421	
2422		nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
2423				shutdown the other cpus.  Instead use the REBOOT_VECTOR
2424				irq.
2425	
2426		nomodule	Disable module load
2427	
2428		nopat		[X86] Disable PAT (page attribute table extension of
2429				pagetables) support.
2430	
2431		norandmaps	Don't use address space randomization.  Equivalent to
2432				echo 0 > /proc/sys/kernel/randomize_va_space
2433	
2434		noreplace-paravirt	[X86,IA-64,PV_OPS] Don't patch paravirt_ops
2435	
2436		noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
2437				with UP alternatives
2438	
2439		nordrand	[X86] Disable kernel use of the RDRAND and
2440				RDSEED instructions even if they are supported
2441				by the processor.  RDRAND and RDSEED are still
2442				available to user space applications.
2443	
2444		noresume	[SWSUSP] Disables resume and restores original swap
2445				space.
2446	
2447		no-scroll	[VGA] Disables scrollback.
2448				This is required for the Braillex ib80-piezo Braille
2449				reader made by F.H. Papenmeier (Germany).
2450	
2451		nosbagart	[IA-64]
2452	
2453		nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2454	
2455		nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
2456				and disable the IO APIC.  legacy for "maxcpus=0".
2457	
2458		nosoftlockup	[KNL] Disable the soft-lockup detector.
2459	
2460		nosync		[HW,M68K] Disables sync negotiation for all devices.
2461	
2462		notsc		[BUGS=X86-32] Disable Time Stamp Counter
2463	
2464		nousb		[USB] Disable the USB subsystem
2465	
2466		nowatchdog	[KNL] Disable the lockup detector (NMI watchdog).
2467	
2468		nowb		[ARM]
2469	
2470		nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
2471	
2472		cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
2473				CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2474				Some features depend on CPU0. Known dependencies are:
2475				1. Resume from suspend/hibernate depends on CPU0.
2476				Suspend/hibernate will fail if CPU0 is offline and you
2477				need to online CPU0 before suspend/hibernate.
2478				2. PIC interrupts also depend on CPU0. CPU0 can't be
2479				removed if a PIC interrupt is detected.
2480				It's said poweroff/reboot may depend on CPU0 on some
2481				machines although I haven't seen such issues so far
2482				after CPU0 is offline on a few tested machines.
2483				If the dependencies are under your control, you can
2484				turn on cpu0_hotplug.
2485	
2486		nptcg=		[IA-64] Override max number of concurrent global TLB
2487				purges which is reported from either PAL_VM_SUMMARY or
2488				SAL PALO.
2489	
2490		nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
2491				could support.  nr_cpus=n : n >= 1 limits the kernel to
2492				supporting 'n' processors. Later in runtime you can not
2493				use hotplug cpu feature to put more cpu back to online.
2494				just like you compile the kernel NR_CPUS=n
2495	
2496		nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
2497	
2498		numa_balancing=	[KNL,X86] Enable or disable automatic NUMA balancing.
2499				Allowed values are enable and disable
2500	
2501		numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2502				one of ['zone', 'node', 'default'] can be specified
2503				This can be set from sysctl after boot.
2504				See Documentation/sysctl/vm.txt for details.
2505	
2506		ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
2507				See Documentation/debugging-via-ohci1394.txt for more
2508				info.
2509	
2510		olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2511				Rather than timing out after 20 ms if an EC
2512				command is not properly ACKed, override the length
2513				of the timeout.  We have interrupts disabled while
2514				waiting for the ACK, so if this is set too high
2515				interrupts *may* be lost!
2516	
2517		omap_mux=	[OMAP] Override bootloader pin multiplexing.
2518				Format: <mux_mode0.mode_name=value>...
2519				For example, to override I2C bus2:
2520				omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2521	
2522		oprofile.timer=	[HW]
2523				Use timer interrupt instead of performance counters
2524	
2525		oprofile.cpu_type=	Force an oprofile cpu type
2526				This might be useful if you have an older oprofile
2527				userland or if you want common events.
2528				Format: { arch_perfmon }
2529				arch_perfmon: [X86] Force use of architectural
2530					perfmon on Intel CPUs instead of the
2531					CPU specific event set.
2532				timer: [X86] Force use of architectural NMI
2533					timer mode (see also oprofile.timer
2534					for generic hr timer mode)
2535					[s390] Force legacy basic mode sampling
2536	                                (report cpu_type "timer")
2537	
2538		oops=panic	Always panic on oopses. Default is to just kill the
2539				process, but there is a small probability of
2540				deadlocking the machine.
2541				This will also cause panics on machine check exceptions.
2542				Useful together with panic=30 to trigger a reboot.
2543	
2544		OSS		[HW,OSS]
2545				See Documentation/sound/oss/oss-parameters.txt
2546	
2547		page_owner=	[KNL] Boot-time page_owner enabling option.
2548				Storage of the information about who allocated
2549				each page is disabled in default. With this switch,
2550				we can turn it on.
2551				on: enable the feature
2552	
2553		panic=		[KNL] Kernel behaviour on panic: delay <timeout>
2554				timeout > 0: seconds before rebooting
2555				timeout = 0: wait forever
2556				timeout < 0: reboot immediately
2557				Format: <timeout>
2558	
2559		panic_on_warn	panic() instead of WARN().  Useful to cause kdump
2560				on a WARN().
2561	
2562		crash_kexec_post_notifiers
2563				Run kdump after running panic-notifiers and dumping
2564				kmsg. This only for the users who doubt kdump always
2565				succeeds in any situation.
2566				Note that this also increases risks of kdump failure,
2567				because some panic notifiers can make the crashed
2568				kernel more unstable.
2569	
2570		parkbd.port=	[HW] Parallel port number the keyboard adapter is
2571				connected to, default is 0.
2572				Format: <parport#>
2573		parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
2574				0 for XT, 1 for AT (default is AT).
2575				Format: <mode>
2576	
2577		parport=	[HW,PPT] Specify parallel ports. 0 disables.
2578				Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2579				Use 'auto' to force the driver to use any
2580				IRQ/DMA settings detected (the default is to
2581				ignore detected IRQ/DMA settings because of
2582				possible conflicts). You can specify the base
2583				address, IRQ, and DMA settings; IRQ and DMA
2584				should be numbers, or 'auto' (for using detected
2585				settings on that particular port), or 'nofifo'
2586				(to avoid using a FIFO even if it is detected).
2587				Parallel ports are assigned in the order they
2588				are specified on the command line, starting
2589				with parport0.
2590	
2591		parport_init_mode=	[HW,PPT]
2592				Configure VIA parallel port to operate in
2593				a specific mode. This is necessary on Pegasos
2594				computer where firmware has no options for setting
2595				up parallel port mode and sets it to spp.
2596				Currently this function knows 686a and 8231 chips.
2597				Format: [spp|ps2|epp|ecp|ecpepp]
2598	
2599		pause_on_oops=
2600				Halt all CPUs after the first oops has been printed for
2601				the specified number of seconds.  This is to be used if
2602				your oopses keep scrolling off the screen.
2603	
2604		pcbit=		[HW,ISDN]
2605	
2606		pcd.		[PARIDE]
2607				See header of drivers/block/paride/pcd.c.
2608				See also Documentation/blockdev/paride.txt.
2609	
2610		pci=option[,option...]	[PCI] various PCI subsystem options:
2611			earlydump	[X86] dump PCI config space before the kernel
2612				        changes anything
2613			off		[X86] don't probe for the PCI bus
2614			bios		[X86-32] force use of PCI BIOS, don't access
2615					the hardware directly. Use this if your machine
2616					has a non-standard PCI host bridge.
2617			nobios		[X86-32] disallow use of PCI BIOS, only direct
2618					hardware access methods are allowed. Use this
2619					if you experience crashes upon bootup and you
2620					suspect they are caused by the BIOS.
2621			conf1		[X86] Force use of PCI Configuration
2622					Mechanism 1.
2623			conf2		[X86] Force use of PCI Configuration
2624					Mechanism 2.
2625			noaer		[PCIE] If the PCIEAER kernel config parameter is
2626					enabled, this kernel boot option can be used to
2627					disable the use of PCIE advanced error reporting.
2628			nodomains	[PCI] Disable support for multiple PCI
2629					root domains (aka PCI segments, in ACPI-speak).
2630			nommconf	[X86] Disable use of MMCONFIG for PCI
2631					Configuration
2632			check_enable_amd_mmconf [X86] check for and enable
2633					properly configured MMIO access to PCI
2634					config space on AMD family 10h CPU
2635			nomsi		[MSI] If the PCI_MSI kernel config parameter is
2636					enabled, this kernel boot option can be used to
2637					disable the use of MSI interrupts system-wide.
2638			noioapicquirk	[APIC] Disable all boot interrupt quirks.
2639					Safety option to keep boot IRQs enabled. This
2640					should never be necessary.
2641			ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
2642					primary IO-APIC for bridges that cannot disable
2643					boot IRQs. This fixes a source of spurious IRQs
2644					when the system masks IRQs.
2645			noioapicreroute	[APIC] Disable workaround that uses the
2646					boot IRQ equivalent of an IRQ that connects to
2647					a chipset where boot IRQs cannot be disabled.
2648					The opposite of ioapicreroute.
2649			biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
2650					routing table. These calls are known to be buggy
2651					on several machines and they hang the machine
2652					when used, but on other computers it's the only
2653					way to get the interrupt routing table. Try
2654					this option if the kernel is unable to allocate
2655					IRQs or discover secondary PCI buses on your
2656					motherboard.
2657			rom		[X86] Assign address space to expansion ROMs.
2658					Use with caution as certain devices share
2659					address decoders between ROMs and other
2660					resources.
2661			norom		[X86] Do not assign address space to
2662					expansion ROMs that do not already have
2663					BIOS assigned address ranges.
2664			nobar		[X86] Do not assign address space to the
2665					BARs that weren't assigned by the BIOS.
2666			irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
2667					assigned automatically to PCI devices. You can
2668					make the kernel exclude IRQs of your ISA cards
2669					this way.
2670			pirqaddr=0xAAAAA	[X86] Specify the physical address
2671					of the PIRQ table (normally generated
2672					by the BIOS) if it is outside the
2673					F0000h-100000h range.
2674			lastbus=N	[X86] Scan all buses thru bus #N. Can be
2675					useful if the kernel is unable to find your
2676					secondary buses and you want to tell it
2677					explicitly which ones they are.
2678			assign-busses	[X86] Always assign all PCI bus
2679					numbers ourselves, overriding
2680					whatever the firmware may have done.
2681			usepirqmask	[X86] Honor the possible IRQ mask stored
2682					in the BIOS $PIR table. This is needed on
2683					some systems with broken BIOSes, notably
2684					some HP Pavilion N5400 and Omnibook XE3
2685					notebooks. This will have no effect if ACPI
2686					IRQ routing is enabled.
2687			noacpi		[X86] Do not use ACPI for IRQ routing
2688					or for PCI scanning.
2689			use_crs		[X86] Use PCI host bridge window information
2690					from ACPI.  On BIOSes from 2008 or later, this
2691					is enabled by default.  If you need to use this,
2692					please report a bug.
2693			nocrs		[X86] Ignore PCI host bridge windows from ACPI.
2694				        If you need to use this, please report a bug.
2695			routeirq	Do IRQ routing for all PCI devices.
2696					This is normally done in pci_enable_device(),
2697					so this option is a temporary workaround
2698					for broken drivers that don't call it.
2699			skip_isa_align	[X86] do not align io start addr, so can
2700					handle more pci cards
2701			firmware	[ARM] Do not re-enumerate the bus but instead
2702					just use the configuration from the
2703					bootloader. This is currently used on
2704					IXP2000 systems where the bus has to be
2705					configured a certain way for adjunct CPUs.
2706			noearly		[X86] Don't do any early type 1 scanning.
2707					This might help on some broken boards which
2708					machine check when some devices' config space
2709					is read. But various workarounds are disabled
2710					and some IOMMU drivers will not work.
2711			bfsort		Sort PCI devices into breadth-first order.
2712					This sorting is done to get a device
2713					order compatible with older (<= 2.4) kernels.
2714			nobfsort	Don't sort PCI devices into breadth-first order.
2715			pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
2716					tuning and use the BIOS-configured MPS defaults.
2717			pcie_bus_safe	Set every device's MPS to the largest value
2718					supported by all devices below the root complex.
2719			pcie_bus_perf	Set device MPS to the largest allowable MPS
2720					based on its parent bus. Also set MRRS (Max
2721					Read Request Size) to the largest supported
2722					value (no larger than the MPS that the device
2723					or bus can support) for best performance.
2724			pcie_bus_peer2peer	Set every device's MPS to 128B, which
2725					every device is guaranteed to support. This
2726					configuration allows peer-to-peer DMA between
2727					any pair of devices, possibly at the cost of
2728					reduced performance.  This also guarantees
2729					that hot-added devices will work.
2730			cbiosize=nn[KMG]	The fixed amount of bus space which is
2731					reserved for the CardBus bridge's IO window.
2732					The default value is 256 bytes.
2733			cbmemsize=nn[KMG]	The fixed amount of bus space which is
2734					reserved for the CardBus bridge's memory
2735					window. The default value is 64 megabytes.
2736			resource_alignment=
2737					Format:
2738					[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2739					Specifies alignment and device to reassign
2740					aligned memory resources.
2741					If <order of align> is not specified,
2742					PAGE_SIZE is used as alignment.
2743					PCI-PCI bridge can be specified, if resource
2744					windows need to be expanded.
2745			ecrc=		Enable/disable PCIe ECRC (transaction layer
2746					end-to-end CRC checking).
2747					bios: Use BIOS/firmware settings. This is the
2748					the default.
2749					off: Turn ECRC off
2750					on: Turn ECRC on.
2751			hpiosize=nn[KMG]	The fixed amount of bus space which is
2752					reserved for hotplug bridge's IO window.
2753					Default size is 256 bytes.
2754			hpmemsize=nn[KMG]	The fixed amount of bus space which is
2755					reserved for hotplug bridge's memory window.
2756					Default size is 2 megabytes.
2757			realloc=	Enable/disable reallocating PCI bridge resources
2758					if allocations done by BIOS are too small to
2759					accommodate resources required by all child
2760					devices.
2761					off: Turn realloc off
2762					on: Turn realloc on
2763			realloc		same as realloc=on
2764			noari		do not use PCIe ARI.
2765			pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
2766					only look for one device below a PCIe downstream
2767					port.
2768	
2769		pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
2770				Management.
2771			off	Disable ASPM.
2772			force	Enable ASPM even on devices that claim not to support it.
2773				WARNING: Forcing ASPM on may cause system lockups.
2774	
2775		pcie_hp=	[PCIE] PCI Express Hotplug driver options:
2776			nomsi	Do not use MSI for PCI Express Native Hotplug (this
2777				makes all PCIe ports use INTx for hotplug services).
2778	
2779		pcie_ports=	[PCIE] PCIe ports handling:
2780			auto	Ask the BIOS whether or not to use native PCIe services
2781				associated with PCIe ports (PME, hot-plug, AER).  Use
2782				them only if that is allowed by the BIOS.
2783			native	Use native PCIe services associated with PCIe ports
2784				unconditionally.
2785			compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2786				ports driver.
2787	
2788		pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
2789			nomsi	Do not use MSI for native PCIe PME signaling (this makes
2790				all PCIe root ports use INTx for all services).
2791	
2792		pcmv=		[HW,PCMCIA] BadgePAD 4
2793	
2794		pd_ignore_unused
2795				[PM]
2796				Keep all power-domains already enabled by bootloader on,
2797				even if no driver has claimed them. This is useful
2798				for debug and development, but should not be
2799				needed on a platform with proper driver support.
2800	
2801		pd.		[PARIDE]
2802				See Documentation/blockdev/paride.txt.
2803	
2804		pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
2805				boot time.
2806				Format: { 0 | 1 }
2807				See arch/parisc/kernel/pdc_chassis.c
2808	
2809		percpu_alloc=	Select which percpu first chunk allocator to use.
2810				Currently supported values are "embed" and "page".
2811				Archs may support subset or none of the	selections.
2812				See comments in mm/percpu.c for details on each
2813				allocator.  This parameter is primarily	for debugging
2814				and performance comparison.
2815	
2816		pf.		[PARIDE]
2817				See Documentation/blockdev/paride.txt.
2818	
2819		pg.		[PARIDE]
2820				See Documentation/blockdev/paride.txt.
2821	
2822		pirq=		[SMP,APIC] Manual mp-table setup
2823				See Documentation/x86/i386/IO-APIC.txt.
2824	
2825		plip=		[PPT,NET] Parallel port network link
2826				Format: { parport<nr> | timid | 0 }
2827				See also Documentation/parport.txt.
2828	
2829		pmtmr=		[X86] Manual setup of pmtmr I/O Port.
2830				Override pmtimer IOPort with a hex value.
2831				e.g. pmtmr=0x508
2832	
2833		pnp.debug=1	[PNP]
2834				Enable PNP debug messages (depends on the
2835				CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
2836				via /sys/module/pnp/parameters/debug.  We always show
2837				current resource usage; turning this on also shows
2838				possible settings and some assignment information.
2839	
2840		pnpacpi=	[ACPI]
2841				{ off }
2842	
2843		pnpbios=	[ISAPNP]
2844				{ on | off | curr | res | no-curr | no-res }
2845	
2846		pnp_reserve_irq=
2847				[ISAPNP] Exclude IRQs for the autoconfiguration
2848	
2849		pnp_reserve_dma=
2850				[ISAPNP] Exclude DMAs for the autoconfiguration
2851	
2852		pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
2853				Ranges are in pairs (I/O port base and size).
2854	
2855		pnp_reserve_mem=
2856				[ISAPNP] Exclude memory regions for the
2857				autoconfiguration.
2858				Ranges are in pairs (memory base and size).
2859	
2860		ports=		[IP_VS_FTP] IPVS ftp helper module
2861				Default is 21.
2862				Up to 8 (IP_VS_APP_MAX_PORTS) ports
2863				may be specified.
2864				Format: <port>,<port>....
2865	
2866		print-fatal-signals=
2867				[KNL] debug: print fatal signals
2868	
2869				If enabled, warn about various signal handling
2870				related application anomalies: too many signals,
2871				too many POSIX.1 timers, fatal signals causing a
2872				coredump - etc.
2873	
2874				If you hit the warning due to signal overflow,
2875				you might want to try "ulimit -i unlimited".
2876	
2877				default: off.
2878	
2879		printk.always_kmsg_dump=
2880				Trigger kmsg_dump for cases other than kernel oops or
2881				panics
2882				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2883				default: disabled
2884	
2885		printk.time=	Show timing data prefixed to each printk message line
2886				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2887	
2888		processor.max_cstate=	[HW,ACPI]
2889				Limit processor to maximum C-state
2890				max_cstate=9 overrides any DMI blacklist limit.
2891	
2892		processor.nocst	[HW,ACPI]
2893				Ignore the _CST method to determine C-states,
2894				instead using the legacy FADT method
2895	
2896		profile=	[KNL] Enable kernel profiling via /proc/profile
2897				Format: [schedule,]<number>
2898				Param: "schedule" - profile schedule points.
2899				Param: <number> - step/bucket size as a power of 2 for
2900					statistical time based profiling.
2901				Param: "sleep" - profile D-state sleeping (millisecs).
2902					Requires CONFIG_SCHEDSTATS
2903				Param: "kvm" - profile VM exits.
2904	
2905		prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
2906				before loading.
2907				See Documentation/blockdev/ramdisk.txt.
2908	
2909		psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
2910				probe for; one of (bare|imps|exps|lifebook|any).
2911		psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
2912				per second.
2913		psmouse.resetafter=	[HW,MOUSE]
2914				Try to reset the device after so many bad packets
2915				(0 = never).
2916		psmouse.resolution=
2917				[HW,MOUSE] Set desired mouse resolution, in dpi.
2918		psmouse.smartscroll=
2919				[HW,MOUSE] Controls Logitech smartscroll autorepeat.
2920				0 = disabled, 1 = enabled (default).
2921	
2922		pstore.backend=	Specify the name of the pstore backend to use
2923	
2924		pt.		[PARIDE]
2925				See Documentation/blockdev/paride.txt.
2926	
2927		pty.legacy_count=
2928				[KNL] Number of legacy pty's. Overwrites compiled-in
2929				default number.
2930	
2931		quiet		[KNL] Disable most log messages
2932	
2933		r128=		[HW,DRM]
2934	
2935		raid=		[HW,RAID]
2936				See Documentation/md.txt.
2937	
2938		ramdisk_blocksize=	[RAM]
2939				See Documentation/blockdev/ramdisk.txt.
2940	
2941		ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
2942				See Documentation/blockdev/ramdisk.txt.
2943	
2944		rcu_nocbs=	[KNL]
2945				In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2946				the specified list of CPUs to be no-callback CPUs.
2947				Invocation of these CPUs' RCU callbacks will
2948				be offloaded to "rcuox/N" kthreads created for
2949				that purpose, where "x" is "b" for RCU-bh, "p"
2950				for RCU-preempt, and "s" for RCU-sched, and "N"
2951				is the CPU number.  This reduces OS jitter on the
2952				offloaded CPUs, which can be useful for HPC and
2953				real-time workloads.  It can also improve energy
2954				efficiency for asymmetric multiprocessors.
2955	
2956		rcu_nocb_poll	[KNL]
2957				Rather than requiring that offloaded CPUs
2958				(specified by rcu_nocbs= above) explicitly
2959				awaken the corresponding "rcuoN" kthreads,
2960				make these kthreads poll for callbacks.
2961				This improves the real-time response for the
2962				offloaded CPUs by relieving them of the need to
2963				wake up the corresponding kthread, but degrades
2964				energy efficiency by requiring that the kthreads
2965				periodically wake up to do the polling.
2966	
2967		rcutree.blimit=	[KNL]
2968				Set maximum number of finished RCU callbacks to
2969				process in one batch.
2970	
2971		rcutree.rcu_fanout_leaf= [KNL]
2972				Increase the number of CPUs assigned to each
2973				leaf rcu_node structure.  Useful for very large
2974				systems.
2975	
2976		rcutree.jiffies_till_sched_qs= [KNL]
2977				Set required age in jiffies for a
2978				given grace period before RCU starts
2979				soliciting quiescent-state help from
2980				rcu_note_context_switch().
2981	
2982		rcutree.jiffies_till_first_fqs= [KNL]
2983				Set delay from grace-period initialization to
2984				first attempt to force quiescent states.
2985				Units are jiffies, minimum value is zero,
2986				and maximum value is HZ.
2987	
2988		rcutree.jiffies_till_next_fqs= [KNL]
2989				Set delay between subsequent attempts to force
2990				quiescent states.  Units are jiffies, minimum
2991				value is one, and maximum value is HZ.
2992	
2993		rcutree.kthread_prio= 	 [KNL,BOOT]
2994				Set the SCHED_FIFO priority of the RCU
2995				per-CPU kthreads (rcuc/N). This value is also
2996				used for the priority of the RCU boost threads
2997				(rcub/N). Valid values are 1-99 and the default
2998				is 1 (the least-favored priority).
2999	
3000		rcutree.rcu_nocb_leader_stride= [KNL]
3001				Set the number of NOCB kthread groups, which
3002				defaults to the square root of the number of
3003				CPUs.  Larger numbers reduces the wakeup overhead
3004				on the per-CPU grace-period kthreads, but increases
3005				that same overhead on each group's leader.
3006	
3007		rcutree.qhimark= [KNL]
3008				Set threshold of queued RCU callbacks beyond which
3009				batch limiting is disabled.
3010	
3011		rcutree.qlowmark= [KNL]
3012				Set threshold of queued RCU callbacks below which
3013				batch limiting is re-enabled.
3014	
3015		rcutree.rcu_idle_gp_delay= [KNL]
3016				Set wakeup interval for idle CPUs that have
3017				RCU callbacks (RCU_FAST_NO_HZ=y).
3018	
3019		rcutree.rcu_idle_lazy_gp_delay= [KNL]
3020				Set wakeup interval for idle CPUs that have
3021				only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3022				Lazy RCU callbacks are those which RCU can
3023				prove do nothing more than free memory.
3024	
3025		rcutorture.cbflood_inter_holdoff= [KNL]
3026				Set holdoff time (jiffies) between successive
3027				callback-flood tests.
3028	
3029		rcutorture.cbflood_intra_holdoff= [KNL]
3030				Set holdoff time (jiffies) between successive
3031				bursts of callbacks within a given callback-flood
3032				test.
3033	
3034		rcutorture.cbflood_n_burst= [KNL]
3035				Set the number of bursts making up a given
3036				callback-flood test.  Set this to zero to
3037				disable callback-flood testing.
3038	
3039		rcutorture.cbflood_n_per_burst= [KNL]
3040				Set the number of callbacks to be registered
3041				in a given burst of a callback-flood test.
3042	
3043		rcutorture.fqs_duration= [KNL]
3044				Set duration of force_quiescent_state bursts.
3045	
3046		rcutorture.fqs_holdoff= [KNL]
3047				Set holdoff time within force_quiescent_state bursts.
3048	
3049		rcutorture.fqs_stutter= [KNL]
3050				Set wait time between force_quiescent_state bursts.
3051	
3052		rcutorture.gp_exp= [KNL]
3053				Use expedited update-side primitives.
3054	
3055		rcutorture.gp_normal= [KNL]
3056				Use normal (non-expedited) update-side primitives.
3057				If both gp_exp and gp_normal are set, do both.
3058				If neither gp_exp nor gp_normal are set, still
3059				do both.
3060	
3061		rcutorture.n_barrier_cbs= [KNL]
3062				Set callbacks/threads for rcu_barrier() testing.
3063	
3064		rcutorture.nfakewriters= [KNL]
3065				Set number of concurrent RCU writers.  These just
3066				stress RCU, they don't participate in the actual
3067				test, hence the "fake".
3068	
3069		rcutorture.nreaders= [KNL]
3070				Set number of RCU readers.
3071	
3072		rcutorture.object_debug= [KNL]
3073				Enable debug-object double-call_rcu() testing.
3074	
3075		rcutorture.onoff_holdoff= [KNL]
3076				Set time (s) after boot for CPU-hotplug testing.
3077	
3078		rcutorture.onoff_interval= [KNL]
3079				Set time (s) between CPU-hotplug operations, or
3080				zero to disable CPU-hotplug testing.
3081	
3082		rcutorture.torture_runnable= [BOOT]
3083				Start rcutorture running at boot time.
3084	
3085		rcutorture.shuffle_interval= [KNL]
3086				Set task-shuffle interval (s).  Shuffling tasks
3087				allows some CPUs to go into dyntick-idle mode
3088				during the rcutorture test.
3089	
3090		rcutorture.shutdown_secs= [KNL]
3091				Set time (s) after boot system shutdown.  This
3092				is useful for hands-off automated testing.
3093	
3094		rcutorture.stall_cpu= [KNL]
3095				Duration of CPU stall (s) to test RCU CPU stall
3096				warnings, zero to disable.
3097	
3098		rcutorture.stall_cpu_holdoff= [KNL]
3099				Time to wait (s) after boot before inducing stall.
3100	
3101		rcutorture.stat_interval= [KNL]
3102				Time (s) between statistics printk()s.
3103	
3104		rcutorture.stutter= [KNL]
3105				Time (s) to stutter testing, for example, specifying
3106				five seconds causes the test to run for five seconds,
3107				wait for five seconds, and so on.  This tests RCU's
3108				ability to transition abruptly to and from idle.
3109	
3110		rcutorture.test_boost= [KNL]
3111				Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
3112				"Maybe" means test if the RCU implementation
3113				under test support RCU priority boosting.
3114	
3115		rcutorture.test_boost_duration= [KNL]
3116				Duration (s) of each individual boost test.
3117	
3118		rcutorture.test_boost_interval= [KNL]
3119				Interval (s) between each boost test.
3120	
3121		rcutorture.test_no_idle_hz= [KNL]
3122				Test RCU's dyntick-idle handling.  See also the
3123				rcutorture.shuffle_interval parameter.
3124	
3125		rcutorture.torture_type= [KNL]
3126				Specify the RCU implementation to test.
3127	
3128		rcutorture.verbose= [KNL]
3129				Enable additional printk() statements.
3130	
3131		rcupdate.rcu_expedited= [KNL]
3132				Use expedited grace-period primitives, for
3133				example, synchronize_rcu_expedited() instead
3134				of synchronize_rcu().  This reduces latency,
3135				but can increase CPU utilization, degrade
3136				real-time latency, and degrade energy efficiency.
3137	
3138		rcupdate.rcu_cpu_stall_suppress= [KNL]
3139				Suppress RCU CPU stall warning messages.
3140	
3141		rcupdate.rcu_cpu_stall_timeout= [KNL]
3142				Set timeout for RCU CPU stall warning messages.
3143	
3144		rcupdate.rcu_task_stall_timeout= [KNL]
3145				Set timeout in jiffies for RCU task stall warning
3146				messages.  Disable with a value less than or equal
3147				to zero.
3148	
3149		rcupdate.rcu_self_test= [KNL]
3150				Run the RCU early boot self tests
3151	
3152		rcupdate.rcu_self_test_bh= [KNL]
3153				Run the RCU bh early boot self tests
3154	
3155		rcupdate.rcu_self_test_sched= [KNL]
3156				Run the RCU sched early boot self tests
3157	
3158		rdinit=		[KNL]
3159				Format: <full_path>
3160				Run specified binary instead of /init from the ramdisk,
3161				used for early userspace startup. See initrd.
3162	
3163		reboot=		[KNL]
3164				Format (x86 or x86_64):
3165					[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3166					[[,]s[mp]#### \
3167					[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3168					[[,]f[orce]
3169				Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3170				      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3171				      reboot_force is either force or not specified,
3172				      reboot_cpu is s[mp]#### with #### being the processor
3173						to be used for rebooting.
3174	
3175		relax_domain_level=
3176				[KNL, SMP] Set scheduler's default relax_domain_level.
3177				See Documentation/cgroups/cpusets.txt.
3178	
3179		relative_sleep_states=
3180				[SUSPEND] Use sleep state labeling where the deepest
3181				state available other than hibernation is always "mem".
3182				Format: { "0" | "1" }
3183				0 -- Traditional sleep state labels.
3184				1 -- Relative sleep state labels.
3185	
3186		reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
3187	
3188		reservetop=	[X86-32]
3189				Format: nn[KMG]
3190				Reserves a hole at the top of the kernel virtual
3191				address space.
3192	
3193		reservelow=	[X86]
3194				Format: nn[K]
3195				Set the amount of memory to reserve for BIOS at
3196				the bottom of the address space.
3197	
3198		reset_devices	[KNL] Force drivers to reset the underlying device
3199				during initialization.
3200	
3201		resume=		[SWSUSP]
3202				Specify the partition device for software suspend
3203				Format:
3204				{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3205	
3206		resume_offset=	[SWSUSP]
3207				Specify the offset from the beginning of the partition
3208				given by "resume=" at which the swap header is located,
3209				in <PAGE_SIZE> units (needed only for swap files).
3210				See  Documentation/power/swsusp-and-swap-files.txt
3211	
3212		resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
3213				read the resume files
3214	
3215		resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
3216				Useful for devices that are detected asynchronously
3217				(e.g. USB and MMC devices).
3218	
3219		hibernate=	[HIBERNATION]
3220			noresume	Don't check if there's a hibernation image
3221					present during boot.
3222			nocompress	Don't compress/decompress hibernation images.
3223			no		Disable hibernation and resume.
3224	
3225		retain_initrd	[RAM] Keep initrd memory after extraction
3226	
3227		rfkill.default_state=
3228			0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
3229				etc. communication is blocked by default.
3230			1	Unblocked.
3231	
3232		rfkill.master_switch_mode=
3233			0	The "airplane mode" button does nothing.
3234			1	The "airplane mode" button toggles between everything
3235				blocked and the previous configuration.
3236			2	The "airplane mode" button toggles between everything
3237				blocked and everything unblocked.
3238	
3239		rhash_entries=	[KNL,NET]
3240				Set number of hash buckets for route cache
3241	
3242		ro		[KNL] Mount root device read-only on boot
3243	
3244		root=		[KNL] Root filesystem
3245				See name_to_dev_t comment in init/do_mounts.c.
3246	
3247		rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
3248				mount the root filesystem
3249	
3250		rootflags=	[KNL] Set root filesystem mount option string
3251	
3252		rootfstype=	[KNL] Set root filesystem type
3253	
3254		rootwait	[KNL] Wait (indefinitely) for root device to show up.
3255				Useful for devices that are detected asynchronously
3256				(e.g. USB and MMC devices).
3257	
3258		rproc_mem=nn[KMG][@address]
3259				[KNL,ARM,CMA] Remoteproc physical memory block.
3260				Memory area to be used by remote processor image,
3261				managed by CMA.
3262	
3263		rw		[KNL] Mount root device read-write on boot
3264	
3265		S		[KNL] Run init in single mode
3266	
3267		s390_iommu=	[HW,S390]
3268				Set s390 IOTLB flushing mode
3269			strict
3270				With strict flushing every unmap operation will result in
3271				an IOTLB flush. Default is lazy flushing before reuse,
3272				which is faster.
3273	
3274		sa1100ir	[NET]
3275				See drivers/net/irda/sa1100_ir.c.
3276	
3277		sbni=		[NET] Granch SBNI12 leased line adapter
3278	
3279		sched_debug	[KNL] Enables verbose scheduler debug messages.
3280	
3281		skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
3282				xtime_lock contention on larger systems, and/or RCU lock
3283				contention on all systems with CONFIG_MAXSMP set.
3284				Format: { "0" | "1" }
3285				0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3286				1 -- enable.
3287				Note: increases power consumption, thus should only be
3288				enabled if running jitter sensitive (HPC/RT) workloads.
3289	
3290		security=	[SECURITY] Choose a security module to enable at boot.
3291				If this boot parameter is not specified, only the first
3292				security module asking for security registration will be
3293				loaded. An invalid security module name will be treated
3294				as if no module has been chosen.
3295	
3296		selinux=	[SELINUX] Disable or enable SELinux at boot time.
3297				Format: { "0" | "1" }
3298				See security/selinux/Kconfig help text.
3299				0 -- disable.
3300				1 -- enable.
3301				Default value is set via kernel config option.
3302				If enabled at boot time, /selinux/disable can be used
3303				later to disable prior to initial policy load.
3304	
3305		apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
3306				Format: { "0" | "1" }
3307				See security/apparmor/Kconfig help text
3308				0 -- disable.
3309				1 -- enable.
3310				Default value is set via kernel config option.
3311	
3312		serialnumber	[BUGS=X86-32]
3313	
3314		shapers=	[NET]
3315				Maximal number of shapers.
3316	
3317		show_msr=	[x86] show boot-time MSR settings
3318				Format: { <integer> }
3319				Show boot-time (BIOS-initialized) MSR settings.
3320				The parameter means the number of CPUs to show,
3321				for example 1 means boot CPU only.
3322	
3323		simeth=		[IA-64]
3324		simscsi=
3325	
3326		slram=		[HW,MTD]
3327	
3328		slab_nomerge	[MM]
3329				Disable merging of slabs with similar size. May be
3330				necessary if there is some reason to distinguish
3331				allocs to different slabs. Debug options disable
3332				merging on their own.
3333				For more information see Documentation/vm/slub.txt.
3334	
3335		slab_max_order=	[MM, SLAB]
3336				Determines the maximum allowed order for slabs.
3337				A high setting may cause OOMs due to memory
3338				fragmentation.  Defaults to 1 for systems with
3339				more than 32MB of RAM, 0 otherwise.
3340	
3341		slub_debug[=options[,slabs]]	[MM, SLUB]
3342				Enabling slub_debug allows one to determine the
3343				culprit if slab objects become corrupted. Enabling
3344				slub_debug can create guard zones around objects and
3345				may poison objects when not in use. Also tracks the
3346				last alloc / free. For more information see
3347				Documentation/vm/slub.txt.
3348	
3349		slub_max_order= [MM, SLUB]
3350				Determines the maximum allowed order for slabs.
3351				A high setting may cause OOMs due to memory
3352				fragmentation. For more information see
3353				Documentation/vm/slub.txt.
3354	
3355		slub_min_objects=	[MM, SLUB]
3356				The minimum number of objects per slab. SLUB will
3357				increase the slab order up to slub_max_order to
3358				generate a sufficiently large slab able to contain
3359				the number of objects indicated. The higher the number
3360				of objects the smaller the overhead of tracking slabs
3361				and the less frequently locks need to be acquired.
3362				For more information see Documentation/vm/slub.txt.
3363	
3364		slub_min_order=	[MM, SLUB]
3365				Determines the minimum page order for slabs. Must be
3366				lower than slub_max_order.
3367				For more information see Documentation/vm/slub.txt.
3368	
3369		slub_nomerge	[MM, SLUB]
3370				Same with slab_nomerge. This is supported for legacy.
3371				See slab_nomerge for more information.
3372	
3373		smart2=		[HW]
3374				Format: <io1>[,<io2>[,...,<io8>]]
3375	
3376		smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
3377		smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
3378		smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
3379		smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
3380		smsc-ircc2.ircc_irq=	[HW] IRQ line
3381		smsc-ircc2.ircc_dma=	[HW] DMA channel
3382		smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3383					0: Toshiba Satellite 1800 (GP data pin select)
3384					1: Fast pin select (default)
3385					2: ATC IRMode
3386	
3387		softlockup_panic=
3388				[KNL] Should the soft-lockup detector generate panics.
3389				Format: <integer>
3390	
3391		softlockup_all_cpu_backtrace=
3392				[KNL] Should the soft-lockup detector generate
3393				backtraces on all cpus.
3394				Format: <integer>
3395	
3396		sonypi.*=	[HW] Sony Programmable I/O Control Device driver
3397				See Documentation/laptops/sonypi.txt
3398	
3399		spia_io_base=	[HW,MTD]
3400		spia_fio_base=
3401		spia_pedr=
3402		spia_peddr=
3403	
3404		stacktrace	[FTRACE]
3405				Enabled the stack tracer on boot up.
3406	
3407		stacktrace_filter=[function-list]
3408				[FTRACE] Limit the functions that the stack tracer
3409				will trace at boot up. function-list is a comma separated
3410				list of functions. This list can be changed at run
3411				time by the stack_trace_filter file in the debugfs
3412				tracing directory. Note, this enables stack tracing
3413				and the stacktrace above is not needed.
3414	
3415		sti=		[PARISC,HW]
3416				Format: <num>
3417				Set the STI (builtin display/keyboard on the HP-PARISC
3418				machines) console (graphic card) which should be used
3419				as the initial boot-console.
3420				See also comment in drivers/video/console/sticore.c.
3421	
3422		sti_font=	[HW]
3423				See comment in drivers/video/console/sticore.c.
3424	
3425		stifb=		[HW]
3426				Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3427	
3428		sunrpc.min_resvport=
3429		sunrpc.max_resvport=
3430				[NFS,SUNRPC]
3431				SunRPC servers often require that client requests
3432				originate from a privileged port (i.e. a port in the
3433				range 0 < portnr < 1024).
3434				An administrator who wishes to reserve some of these
3435				ports for other uses may adjust the range that the
3436				kernel's sunrpc client considers to be privileged
3437				using these two parameters to set the minimum and
3438				maximum port values.
3439	
3440		sunrpc.pool_mode=
3441				[NFS]
3442				Control how the NFS server code allocates CPUs to
3443				service thread pools.  Depending on how many NICs
3444				you have and where their interrupts are bound, this
3445				option will affect which CPUs will do NFS serving.
3446				Note: this parameter cannot be changed while the
3447				NFS server is running.
3448	
3449				auto	    the server chooses an appropriate mode
3450					    automatically using heuristics
3451				global	    a single global pool contains all CPUs
3452				percpu	    one pool for each CPU
3453				pernode	    one pool for each NUMA node (equivalent
3454					    to global on non-NUMA machines)
3455	
3456		sunrpc.tcp_slot_table_entries=
3457		sunrpc.udp_slot_table_entries=
3458				[NFS,SUNRPC]
3459				Sets the upper limit on the number of simultaneous
3460				RPC calls that can be sent from the client to a
3461				server. Increasing these values may allow you to
3462				improve throughput, but will also increase the
3463				amount of memory reserved for use by the client.
3464	
3465		swapaccount=[0|1]
3466				[KNL] Enable accounting of swap in memory resource
3467				controller if no parameter or 1 is given or disable
3468				it if 0 is given (See Documentation/cgroups/memory.txt)
3469	
3470		swiotlb=	[ARM,IA-64,PPC,MIPS,X86]
3471				Format: { <int> | force }
3472				<int> -- Number of I/O TLB slabs
3473				force -- force using of bounce buffers even if they
3474				         wouldn't be automatically used by the kernel
3475	
3476		switches=	[HW,M68k]
3477	
3478		sysfs.deprecated=0|1 [KNL]
3479				Enable/disable old style sysfs layout for old udev
3480				on older distributions. When this option is enabled
3481				very new udev will not work anymore. When this option
3482				is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3483				in older udev will not work anymore.
3484				Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3485				the kernel configuration.
3486	
3487		sysrq_always_enabled
3488				[KNL]
3489				Ignore sysrq setting - this boot parameter will
3490				neutralize any effect of /proc/sys/kernel/sysrq.
3491				Useful for debugging.
3492	
3493		tcpmhash_entries= [KNL,NET]
3494				Set the number of tcp_metrics_hash slots.
3495				Default value is 8192 or 16384 depending on total
3496				ram pages. This is used to specify the TCP metrics
3497				cache size. See Documentation/networking/ip-sysctl.txt
3498				"tcp_no_metrics_save" section for more details.
3499	
3500		tdfx=		[HW,DRM]
3501	
3502		test_suspend=	[SUSPEND][,N]
3503				Specify "mem" (for Suspend-to-RAM) or "standby" (for
3504				standby suspend) or "freeze" (for suspend type freeze)
3505				as the system sleep state during system startup with
3506				the optional capability to repeat N number of times.
3507				The system is woken from this state using a
3508				wakeup-capable RTC alarm.
3509	
3510		thash_entries=	[KNL,NET]
3511				Set number of hash buckets for TCP connection
3512	
3513		thermal.act=	[HW,ACPI]
3514				-1: disable all active trip points in all thermal zones
3515				<degrees C>: override all lowest active trip points
3516	
3517		thermal.crt=	[HW,ACPI]
3518				-1: disable all critical trip points in all thermal zones
3519				<degrees C>: override all critical trip points
3520	
3521		thermal.nocrt=	[HW,ACPI]
3522				Set to disable actions on ACPI thermal zone
3523				critical and hot trip points.
3524	
3525		thermal.off=	[HW,ACPI]
3526				1: disable ACPI thermal control
3527	
3528		thermal.psv=	[HW,ACPI]
3529				-1: disable all passive trip points
3530				<degrees C>: override all passive trip points to this
3531				value
3532	
3533		thermal.tzp=	[HW,ACPI]
3534				Specify global default ACPI thermal zone polling rate
3535				<deci-seconds>: poll all this frequency
3536				0: no polling (default)
3537	
3538		threadirqs	[KNL]
3539				Force threading of all interrupt handlers except those
3540				marked explicitly IRQF_NO_THREAD.
3541	
3542		tmem		[KNL,XEN]
3543				Enable the Transcendent memory driver if built-in.
3544	
3545		tmem.cleancache=0|1 [KNL, XEN]
3546				Default is on (1). Disable the usage of the cleancache
3547				API to send anonymous pages to the hypervisor.
3548	
3549		tmem.frontswap=0|1 [KNL, XEN]
3550				Default is on (1). Disable the usage of the frontswap
3551				API to send swap pages to the hypervisor. If disabled
3552				the selfballooning and selfshrinking are force disabled.
3553	
3554		tmem.selfballooning=0|1 [KNL, XEN]
3555				Default is on (1). Disable the driving of swap pages
3556				to the hypervisor.
3557	
3558		tmem.selfshrinking=0|1 [KNL, XEN]
3559				Default is on (1). Partial swapoff that immediately
3560				transfers pages from Xen hypervisor back to the
3561				kernel based on different criteria.
3562	
3563		topology=	[S390]
3564				Format: {off | on}
3565				Specify if the kernel should make use of the cpu
3566				topology information if the hardware supports this.
3567				The scheduler will make use of this information and
3568				e.g. base its process migration decisions on it.
3569				Default is on.
3570	
3571		topology_updates= [KNL, PPC, NUMA]
3572				Format: {off}
3573				Specify if the kernel should ignore (off)
3574				topology updates sent by the hypervisor to this
3575				LPAR.
3576	
3577		tp720=		[HW,PS2]
3578	
3579		tpm_suspend_pcr=[HW,TPM]
3580				Format: integer pcr id
3581				Specify that at suspend time, the tpm driver
3582				should extend the specified pcr with zeros,
3583				as a workaround for some chips which fail to
3584				flush the last written pcr on TPM_SaveState.
3585				This will guarantee that all the other pcrs
3586				are saved.
3587	
3588		trace_buf_size=nn[KMG]
3589				[FTRACE] will set tracing buffer size on each cpu.
3590	
3591		trace_event=[event-list]
3592				[FTRACE] Set and start specified trace events in order
3593				to facilitate early boot debugging.
3594				See also Documentation/trace/events.txt
3595	
3596		trace_options=[option-list]
3597				[FTRACE] Enable or disable tracer options at boot.
3598				The option-list is a comma delimited list of options
3599				that can be enabled or disabled just as if you were
3600				to echo the option name into
3601	
3602				    /sys/kernel/debug/tracing/trace_options
3603	
3604				For example, to enable stacktrace option (to dump the
3605				stack trace of each event), add to the command line:
3606	
3607				      trace_options=stacktrace
3608	
3609				See also Documentation/trace/ftrace.txt "trace options"
3610				section.
3611	
3612		tp_printk[FTRACE]
3613				Have the tracepoints sent to printk as well as the
3614				tracing ring buffer. This is useful for early boot up
3615				where the system hangs or reboots and does not give the
3616				option for reading the tracing buffer or performing a
3617				ftrace_dump_on_oops.
3618	
3619				To turn off having tracepoints sent to printk,
3620				 echo 0 > /proc/sys/kernel/tracepoint_printk
3621				Note, echoing 1 into this file without the
3622				tracepoint_printk kernel cmdline option has no effect.
3623	
3624				** CAUTION **
3625	
3626				Having tracepoints sent to printk() and activating high
3627				frequency tracepoints such as irq or sched, can cause
3628				the system to live lock.
3629	
3630		traceoff_on_warning
3631				[FTRACE] enable this option to disable tracing when a
3632				warning is hit. This turns off "tracing_on". Tracing can
3633				be enabled again by echoing '1' into the "tracing_on"
3634				file located in /sys/kernel/debug/tracing/
3635	
3636				This option is useful, as it disables the trace before
3637				the WARNING dump is called, which prevents the trace to
3638				be filled with content caused by the warning output.
3639	
3640				This option can also be set at run time via the sysctl
3641				option:  kernel/traceoff_on_warning
3642	
3643		transparent_hugepage=
3644				[KNL]
3645				Format: [always|madvise|never]
3646				Can be used to control the default behavior of the system
3647				with respect to transparent hugepages.
3648				See Documentation/vm/transhuge.txt for more details.
3649	
3650		tsc=		Disable clocksource stability checks for TSC.
3651				Format: <string>
3652				[x86] reliable: mark tsc clocksource as reliable, this
3653				disables clocksource verification at runtime, as well
3654				as the stability checks done at bootup.	Used to enable
3655				high-resolution timer mode on older hardware, and in
3656				virtualized environment.
3657				[x86] noirqtime: Do not use TSC to do irq accounting.
3658				Used to run time disable IRQ_TIME_ACCOUNTING on any
3659				platforms where RDTSC is slow and this accounting
3660				can add overhead.
3661	
3662		turbografx.map[2|3]=	[HW,JOY]
3663				TurboGraFX parallel port interface
3664				Format:
3665				<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3666				See also Documentation/input/joystick-parport.txt
3667	
3668		udbg-immortal	[PPC] When debugging early kernel crashes that
3669				happen after console_init() and before a proper 
3670				console driver takes over, this boot options might
3671				help "seeing" what's going on.
3672	
3673		uhash_entries=	[KNL,NET]
3674				Set number of hash buckets for UDP/UDP-Lite connections
3675	
3676		uhci-hcd.ignore_oc=
3677				[USB] Ignore overcurrent events (default N).
3678				Some badly-designed motherboards generate lots of
3679				bogus events, for ports that aren't wired to
3680				anything.  Set this parameter to avoid log spamming.
3681				Note that genuine overcurrent events won't be
3682				reported either.
3683	
3684		unknown_nmi_panic
3685				[X86] Cause panic on unknown NMI.
3686	
3687		usbcore.authorized_default=
3688				[USB] Default USB device authorization:
3689				(default -1 = authorized except for wireless USB,
3690				0 = not authorized, 1 = authorized)
3691	
3692		usbcore.autosuspend=
3693				[USB] The autosuspend time delay (in seconds) used
3694				for newly-detected USB devices (default 2).  This
3695				is the time required before an idle device will be
3696				autosuspended.  Devices for which the delay is set
3697				to a negative value won't be autosuspended at all.
3698	
3699		usbcore.usbfs_snoop=
3700				[USB] Set to log all usbfs traffic (default 0 = off).
3701	
3702		usbcore.blinkenlights=
3703				[USB] Set to cycle leds on hubs (default 0 = off).
3704	
3705		usbcore.old_scheme_first=
3706				[USB] Start with the old device initialization
3707				scheme (default 0 = off).
3708	
3709		usbcore.usbfs_memory_mb=
3710				[USB] Memory limit (in MB) for buffers allocated by
3711				usbfs (default = 16, 0 = max = 2047).
3712	
3713		usbcore.use_both_schemes=
3714				[USB] Try the other device initialization scheme
3715				if the first one fails (default 1 = enabled).
3716	
3717		usbcore.initial_descriptor_timeout=
3718				[USB] Specifies timeout for the initial 64-byte
3719	                        USB_REQ_GET_DESCRIPTOR request in milliseconds
3720				(default 5000 = 5.0 seconds).
3721	
3722		usbhid.mousepoll=
3723				[USBHID] The interval which mice are to be polled at.
3724	
3725		usb-storage.delay_use=
3726				[UMS] The delay in seconds before a new device is
3727				scanned for Logical Units (default 1).
3728	
3729		usb-storage.quirks=
3730				[UMS] A list of quirks entries to supplement or
3731				override the built-in unusual_devs list.  List
3732				entries are separated by commas.  Each entry has
3733				the form VID:PID:Flags where VID and PID are Vendor
3734				and Product ID values (4-digit hex numbers) and
3735				Flags is a set of characters, each corresponding
3736				to a common usb-storage quirk flag as follows:
3737					a = SANE_SENSE (collect more than 18 bytes
3738						of sense data);
3739					b = BAD_SENSE (don't collect more than 18
3740						bytes of sense data);
3741					c = FIX_CAPACITY (decrease the reported
3742						device capacity by one sector);
3743					d = NO_READ_DISC_INFO (don't use
3744						READ_DISC_INFO command);
3745					e = NO_READ_CAPACITY_16 (don't use
3746						READ_CAPACITY_16 command);
3747					f = NO_REPORT_OPCODES (don't use report opcodes
3748						command, uas only);
3749					h = CAPACITY_HEURISTICS (decrease the
3750						reported device capacity by one
3751						sector if the number is odd);
3752					i = IGNORE_DEVICE (don't bind to this
3753						device);
3754					l = NOT_LOCKABLE (don't try to lock and
3755						unlock ejectable media);
3756					m = MAX_SECTORS_64 (don't transfer more
3757						than 64 sectors = 32 KB at a time);
3758					n = INITIAL_READ10 (force a retry of the
3759						initial READ(10) command);
3760					o = CAPACITY_OK (accept the capacity
3761						reported by the device);
3762					p = WRITE_CACHE (the device cache is ON
3763						by default);
3764					r = IGNORE_RESIDUE (the device reports
3765						bogus residue values);
3766					s = SINGLE_LUN (the device has only one
3767						Logical Unit);
3768					t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3769						commands, uas only);
3770					u = IGNORE_UAS (don't bind to the uas driver);
3771					w = NO_WP_DETECT (don't test whether the
3772						medium is write-protected).
3773				Example: quirks=0419:aaf5:rl,0421:0433:rc
3774	
3775		user_debug=	[KNL,ARM]
3776				Format: <int>
3777				See arch/arm/Kconfig.debug help text.
3778					 1 - undefined instruction events
3779					 2 - system calls
3780					 4 - invalid data aborts
3781					 8 - SIGSEGV faults
3782					16 - SIGBUS faults
3783				Example: user_debug=31
3784	
3785		userpte=
3786				[X86] Flags controlling user PTE allocations.
3787	
3788					nohigh = do not allocate PTE pages in
3789						HIGHMEM regardless of setting
3790						of CONFIG_HIGHPTE.
3791	
3792		vdso=		[X86,SH]
3793				On X86_32, this is an alias for vdso32=.  Otherwise:
3794	
3795				vdso=1: enable VDSO (the default)
3796				vdso=0: disable VDSO mapping
3797	
3798		vdso32=		[X86] Control the 32-bit vDSO
3799				vdso32=1: enable 32-bit VDSO
3800				vdso32=0 or vdso32=2: disable 32-bit VDSO
3801	
3802				See the help text for CONFIG_COMPAT_VDSO for more
3803				details.  If CONFIG_COMPAT_VDSO is set, the default is
3804				vdso32=0; otherwise, the default is vdso32=1.
3805	
3806				For compatibility with older kernels, vdso32=2 is an
3807				alias for vdso32=0.
3808	
3809				Try vdso32=0 if you encounter an error that says:
3810				dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3811	
3812		vector=		[IA-64,SMP]
3813				vector=percpu: enable percpu vector domain
3814	
3815		video=		[FB] Frame buffer configuration
3816				See Documentation/fb/modedb.txt.
3817	
3818		video.brightness_switch_enabled= [0,1]
3819				If set to 1, on receiving an ACPI notify event
3820				generated by hotkey, video driver will adjust brightness
3821				level and then send out the event to user space through
3822				the allocated input device; If set to 0, video driver
3823				will only send out the event without touching backlight
3824				brightness level.
3825				default: 1
3826	
3827		virtio_mmio.device=
3828				[VMMIO] Memory mapped virtio (platform) device.
3829	
3830					<size>@<baseaddr>:<irq>[:<id>]
3831				where:
3832					<size>     := size (can use standard suffixes
3833							like K, M and G)
3834					<baseaddr> := physical base address
3835					<irq>      := interrupt number (as passed to
3836							request_irq())
3837					<id>       := (optional) platform device id
3838				example:
3839					virtio_mmio.device=1K@0x100b0000:48:7
3840	
3841				Can be used multiple times for multiple devices.
3842	
3843		vga=		[BOOT,X86-32] Select a particular video mode
3844				See Documentation/x86/boot.txt and
3845				Documentation/svga.txt.
3846				Use vga=ask for menu.
3847				This is actually a boot loader parameter; the value is
3848				passed to the kernel using a special protocol.
3849	
3850		vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
3851				size of <nn>. This can be used to increase the
3852				minimum size (128MB on x86). It can also be used to
3853				decrease the size and leave more room for directly
3854				mapped kernel RAM.
3855	
3856		vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
3857				Format: <command>
3858	
3859		vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
3860				Format: <command>
3861	
3862		vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
3863				Format: <command>
3864	
3865		vsyscall=	[X86-64]
3866				Controls the behavior of vsyscalls (i.e. calls to
3867				fixed addresses of 0xffffffffff600x00 from legacy
3868				code).  Most statically-linked binaries and older
3869				versions of glibc use these calls.  Because these
3870				functions are at fixed addresses, they make nice
3871				targets for exploits that can control RIP.
3872	
3873				emulate     [default] Vsyscalls turn into traps and are
3874				            emulated reasonably safely.
3875	
3876				native      Vsyscalls are native syscall instructions.
3877				            This is a little bit faster than trapping
3878				            and makes a few dynamic recompilers work
3879				            better than they would in emulation mode.
3880				            It also makes exploits much easier to write.
3881	
3882				none        Vsyscalls don't work at all.  This makes
3883				            them quite hard to use for exploits but
3884				            might break your system.
3885	
3886		vt.color=	[VT] Default text color.
3887				Format: 0xYX, X = foreground, Y = background.
3888				Default: 0x07 = light gray on black.
3889	
3890		vt.cur_default=	[VT] Default cursor shape.
3891				Format: 0xCCBBAA, where AA, BB, and CC are the same as
3892				the parameters of the <Esc>[?A;B;Cc escape sequence;
3893				see VGA-softcursor.txt. Default: 2 = underline.
3894	
3895		vt.default_blu=	[VT]
3896				Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3897				Change the default blue palette of the console.
3898				This is a 16-member array composed of values
3899				ranging from 0-255.
3900	
3901		vt.default_grn=	[VT]
3902				Format: <green0>,<green1>,<green2>,...,<green15>
3903				Change the default green palette of the console.
3904				This is a 16-member array composed of values
3905				ranging from 0-255.
3906	
3907		vt.default_red=	[VT]
3908				Format: <red0>,<red1>,<red2>,...,<red15>
3909				Change the default red palette of the console.
3910				This is a 16-member array composed of values
3911				ranging from 0-255.
3912	
3913		vt.default_utf8=
3914				[VT]
3915				Format=<0|1>
3916				Set system-wide default UTF-8 mode for all tty's.
3917				Default is 1, i.e. UTF-8 mode is enabled for all
3918				newly opened terminals.
3919	
3920		vt.global_cursor_default=
3921				[VT]
3922				Format=<-1|0|1>
3923				Set system-wide default for whether a cursor
3924				is shown on new VTs. Default is -1,
3925				i.e. cursors will be created by default unless
3926				overridden by individual drivers. 0 will hide
3927				cursors, 1 will display them.
3928	
3929		vt.italic=	[VT] Default color for italic text; 0-15.
3930				Default: 2 = green.
3931	
3932		vt.underline=	[VT] Default color for underlined text; 0-15.
3933				Default: 3 = cyan.
3934	
3935		watchdog timers	[HW,WDT] For information on watchdog timers,
3936				see Documentation/watchdog/watchdog-parameters.txt
3937				or other driver-specific files in the
3938				Documentation/watchdog/ directory.
3939	
3940		workqueue.disable_numa
3941				By default, all work items queued to unbound
3942				workqueues are affine to the NUMA nodes they're
3943				issued on, which results in better behavior in
3944				general.  If NUMA affinity needs to be disabled for
3945				whatever reason, this option can be used.  Note
3946				that this also can be controlled per-workqueue for
3947				workqueues visible under /sys/bus/workqueue/.
3948	
3949		workqueue.power_efficient
3950				Per-cpu workqueues are generally preferred because
3951				they show better performance thanks to cache
3952				locality; unfortunately, per-cpu workqueues tend to
3953				be more power hungry than unbound workqueues.
3954	
3955				Enabling this makes the per-cpu workqueues which
3956				were observed to contribute significantly to power
3957				consumption unbound, leading to measurably lower
3958				power usage at the cost of small performance
3959				overhead.
3960	
3961				The default value of this parameter is determined by
3962				the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3963	
3964		x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
3965				default x2apic cluster mode on platforms
3966				supporting x2apic.
3967	
3968		x86_intel_mid_timer= [X86-32,APBT]
3969				Choose timer option for x86 Intel MID platform.
3970				Two valid options are apbt timer only and lapic timer
3971				plus one apbt timer for broadcast timer.
3972				x86_intel_mid_timer=apbt_only | lapic_and_apbt
3973	
3974		xen_emul_unplug=		[HW,X86,XEN]
3975				Unplug Xen emulated devices
3976				Format: [unplug0,][unplug1]
3977				ide-disks -- unplug primary master IDE devices
3978				aux-ide-disks -- unplug non-primary-master IDE devices
3979				nics -- unplug network devices
3980				all -- unplug all emulated devices (NICs and IDE disks)
3981				unnecessary -- unplugging emulated devices is
3982					unnecessary even if the host did not respond to
3983					the unplug protocol
3984				never -- do not unplug even if version check succeeds
3985	
3986		xen_nopvspin	[X86,XEN]
3987				Disables the ticketlock slowpath using Xen PV
3988				optimizations.
3989	
3990		xen_nopv	[X86]
3991				Disables the PV optimizations forcing the HVM guest to
3992				run as generic HVM guest with no PV drivers.
3993	
3994		xirc2ps_cs=	[NET,PCMCIA]
3995				Format:
3996				<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3997	
3998	______________________________________________________________________
3999	
4000	TODO:
4001	
4002		Add more DRM drivers.
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