Documentation: Merge x86-specific boot options doc into kernel-parameters.txt (ab0e7f20) · Commits · git / linux-net

Documentation/admin-guide/kernel-parameters.rst

+0 −3

Original line number	Diff line number	Diff line
		@@ -194,8 +194,6 @@ is applicable::
		WDT Watchdog support is enabled.
		X86-32 X86-32, aka i386 architecture is enabled.
		X86-64 X86-64 architecture is enabled.
		More X86-64 boot options can be found in
		Documentation/arch/x86/x86_64/boot-options.rst.
		X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
		X86_UV SGI UV support is enabled.
		XEN Xen support is enabled
		@@ -213,7 +211,6 @@ Do not modify the syntax of boot loader parameters without extreme
		need or coordination with <Documentation/arch/x86/boot.rst>.

		There are also arch-specific kernel-parameters not documented here.
		See for example <Documentation/arch/x86/x86_64/boot-options.rst>.

		Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
		a trailing = on the name of any parameter states that that parameter will

Documentation/admin-guide/kernel-parameters.txt

+225 −12

Original line number	Diff line number	Diff line
		@@ -21,6 +21,10 @@
		strictly ACPI specification compliant.
		rsdt -- prefer RSDT over (default) XSDT
		copy_dsdt -- copy DSDT to memory
		nocmcff -- Disable firmware first mode for corrected
		errors. This disables parsing the HEST CMC error
		source to check if firmware has set the FF flag. This
		may result in duplicate corrected error reports.
		nospcr -- disable console in ACPI SPCR table as
		default _serial_ console on ARM64
		For ARM64, ONLY "acpi=off", "acpi=on", "acpi=force" or
		@@ -405,6 +409,8 @@
		not play well with APC CPU idle - disable it if you have
		APC and your system crashes randomly.

		apic [APIC,X86-64] Use IO-APIC. Default.

		apic= [APIC,X86,EARLY] Advanced Programmable Interrupt Controller
		Change the output verbosity while booting
		Format: { quiet (default) \| verbose \| debug }
		@@ -424,6 +430,10 @@
		useful so that a dump capture kernel won't be
		shot down by NMI

		apicpmtimer Do APIC timer calibration using the pmtimer. Implies
		apicmaintimer. Useful when your PIT timer is totally
		broken.

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

		@@ -1726,6 +1736,8 @@

		off: Disable GDS mitigation.

		gbpages [X86] Use GB pages for kernel direct mappings.

		gcov_persist= [GCOV] When non-zero (default), profiling data for
		kernel modules is saved and remains accessible via
		debugfs, even when the module is unloaded/reloaded.
		@@ -2008,12 +2020,21 @@

		idle= [X86,EARLY]
		Format: idle=poll, idle=halt, idle=nomwait
		Poll forces a polling idle loop that can slightly
		improve the performance of waking up a idle CPU, but
		will use a lot of power and make the system run hot.
		Not recommended.

		idle=poll: Don't do power saving in the idle loop
		using HLT, but poll for rescheduling event. This will
		make the CPUs eat a lot more power, but may be useful
		to get slightly better performance in multiprocessor
		benchmarks. It also makes some profiling using
		performance counters more accurate. Please note that
		on systems with MONITOR/MWAIT support (like Intel
		EM64T CPUs) this option has no performance advantage
		over the normal idle loop. It may also interact badly
		with hyperthreading.

		idle=halt: Halt is forced to be used for CPU idle.
		In such case C2/C3 won't be used again.

		idle=nomwait: Disable mwait for CPU C-states

		idxd.sva= [HW]
		@@ -2311,20 +2332,73 @@
		relaxed

		iommu= [X86,EARLY]

		off
		Don't initialize and use any kind of IOMMU.

		force
		Force the use of the hardware IOMMU even when
		it is not actually needed (e.g. because < 3 GB
		memory).

		noforce
		Don't force hardware IOMMU usage when it is not
		needed. (default).

		biomerge
		panic
		nopanic
		merge
		nomerge

		soft
		pt [X86]
		nopt [X86]
		nobypass [PPC/POWERNV]
		Use software bounce buffering (SWIOTLB) (default for
		Intel machines). This can be used to prevent the usage
		of an available hardware IOMMU.

		[X86]
		pt
		[X86]
		nopt
		[PPC/POWERNV]
		nobypass
		Disable IOMMU bypass, using IOMMU for PCI devices.

		[X86]
		AMD Gart HW IOMMU-specific options:

		<size>
		Set the size of the remapping area in bytes.

		allowed
		Overwrite iommu off workarounds for specific chipsets

		fullflush
		Flush IOMMU on each allocation (default).

		nofullflush
		Don't use IOMMU fullflush.

		memaper[=<order>]
		Allocate an own aperture over RAM with size
		32MB<<order. (default: order=1, i.e. 64MB)

		merge
		Do scatter-gather (SG) merging. Implies "force"
		(experimental).

		nomerge
		Don't do scatter-gather (SG) merging.

		noaperture
		Ask the IOMMU not to touch the aperture for AGP.

		noagp
		Don't initialize the AGP driver and use full aperture.

		panic
		Always panic when IOMMU overflows.

		iommu.forcedac= [ARM64,X86,EARLY] Control IOVA allocation for PCI devices.
		Format: { "0" \| "1" }
		0 - Try to allocate a 32-bit DMA address first, before
		@@ -3259,9 +3333,77 @@
		devices can be requested on-demand with the
		/dev/loop-control interface.

		mce [X86-32] Machine Check Exception
		mce= [X86-{32,64}]

		Please see Documentation/arch/x86/x86_64/machinecheck.rst for sysfs runtime tunables.

		off
		disable machine check

		no_cmci
		disable CMCI(Corrected Machine Check Interrupt) that
		Intel processor supports. Usually this disablement is
		not recommended, but it might be handy if your
		hardware is misbehaving.

		Note that you'll get more problems without CMCI than
		with due to the shared banks, i.e. you might get
		duplicated error logs.

		dont_log_ce
		don't make logs for corrected errors. All events
		reported as corrected are silently cleared by OS. This
		option will be useful if you have no interest in any
		of corrected errors.

		ignore_ce
		disable features for corrected errors, e.g.
		polling timer and CMCI. All events reported as
		corrected are not cleared by OS and remained in its
		error banks.

		Usually this disablement is not recommended, however
		if there is an agent checking/clearing corrected
		errors (e.g. BIOS or hardware monitoring
		applications), conflicting with OS's error handling,
		and you cannot deactivate the agent, then this option
		will be a help.

		no_lmce
		do not opt-in to Local MCE delivery. Use legacy method
		to broadcast MCEs.

		bootlog
		enable logging of machine checks left over from
		booting. Disabled by default on AMD Fam10h and older
		because some BIOS leave bogus ones.

		If your BIOS doesn't do that it's a good idea to
		enable though to make sure you log even machine check
		events that result in a reboot. On Intel systems it is
		enabled by default.

		nobootlog
		disable boot machine check logging.

		monarchtimeout (number)
		sets the time in us to wait for other CPUs on machine
		checks. 0 to disable.

		bios_cmci_threshold
		don't overwrite the bios-set CMCI threshold. This boot
		option prevents Linux from overwriting the CMCI
		threshold set by the bios. Without this option, Linux
		always sets the CMCI threshold to 1. Enabling this may
		make memory predictive failure analysis less effective
		if the bios sets thresholds for memory errors since we
		will not see details for all errors.

		recovery
		force-enable recoverable machine check code paths

		Everything else is in sysfs now.

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

		md= [HW] RAID subsystems devices and level
		See Documentation/admin-guide/md.rst.
		@@ -3887,6 +4029,8 @@
		noapic [SMP,APIC,EARLY] Tells the kernel to not make use of any
		IOAPICs that may be present in the system.

		noapictimer [APIC,X86] Don't set up the APIC timer

		noautogroup Disable scheduler automatic task group creation.

		nocache [ARM,EARLY]
		@@ -3934,6 +4078,8 @@
		register save and restore. The kernel will only save
		legacy floating-point registers on task switch.

		nogbpages [X86] Do not use GB pages for kernel direct mappings.

		no_hash_pointers
		[KNL,EARLY]
		Force pointers printed to the console or buffers to be
		@@ -3960,6 +4106,8 @@
		the impact of the sleep instructions. This is also
		useful when using JTAG debugger.

		nohpet [X86] Don't use the HPET timer.

		nohugeiomap [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings.

		nohugevmalloc [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings.
		@@ -4111,8 +4259,10 @@

		nosync [HW,M68K] Disables sync negotiation for all devices.

		no_timer_check [X86,APIC] Disables the code which tests for
		broken timer IRQ sources.
		no_timer_check [X86,APIC] Disables the code which tests for broken
		timer IRQ sources, i.e., the IO-APIC timer. This can
		work around problems with incorrect timer
		initialization on some boards.

		no_uaccess_flush
		[PPC,EARLY] Don't flush the L1-D cache after accessing user data.
		@@ -4192,6 +4342,11 @@
		If given as an integer followed by 'U', it will
		divide each physical node into N emulated nodes.

		numa=noacpi [X86] Don't parse the SRAT table for NUMA setup

		numa=nohmat [X86] Don't parse the HMAT table for NUMA setup, or
		soft-reserved memory partitioning.

		numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
		NUMA balancing.
		Allowed values are enable and disable
		@@ -5710,6 +5865,55 @@
		reboot_cpu is s[mp]#### with #### being the processor
		to be used for rebooting.

		acpi
		Use the ACPI RESET_REG in the FADT. If ACPI is not
		configured or the ACPI reset does not work, the reboot
		path attempts the reset using the keyboard controller.

		bios
		Use the CPU reboot vector for warm reset

		cold
		Set the cold reboot flag

		default
		There are some built-in platform specific "quirks"
		- you may see: "reboot: <name> series board detected.
		Selecting <type> for reboots." In the case where you
		think the quirk is in error (e.g. you have newer BIOS,
		or newer board) using this option will ignore the
		built-in quirk table, and use the generic default
		reboot actions.

		efi
		Use efi reset_system runtime service. If EFI is not
		configured or the EFI reset does not work, the reboot
		path attempts the reset using the keyboard controller.

		force
		Don't stop other CPUs on reboot. This can make reboot
		more reliable in some cases.

		kbd
		Use the keyboard controller. cold reset (default)

		pci
		Use a write to the PCI config space register 0xcf9 to
		trigger reboot.

		triple
		Force a triple fault (init)

		warm
		Don't set the cold reboot flag

		Using warm reset will be much faster especially on big
		memory systems because the BIOS will not go through
		the memory check. Disadvantage is that not all
		hardware will be completely reinitialized on reboot so
		there may be boot problems on some systems.


		refscale.holdoff= [KNL]
		Set test-start holdoff period. The purpose of
		this parameter is to delay the start of the
		@@ -6101,7 +6305,16 @@

		serialnumber [BUGS=X86-32]

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

		debug
		Enable debug messages.

		nosnp
		Do not enable SEV-SNP (applies to host/hypervisor
		only). Setting 'nosnp' avoids the RMP check overhead
		in memory accesses when users do not want to run
		SEV-SNP guests.

		shapers= [NET]
		Maximal number of shapers.

Documentation/arch/x86/x86_64/boot-options.rst

deleted100644 → 0

+0 −312

Original line number	Diff line number	Diff line
		.. SPDX-License-Identifier: GPL-2.0

		===========================
		AMD64 Specific Boot Options
		===========================

		There are many others (usually documented in driver documentation), but
		only the AMD64 specific ones are listed here.

		Machine check
		=============
		Please see Documentation/arch/x86/x86_64/machinecheck.rst for sysfs runtime tunables.

		mce=off
		Disable machine check
		mce=no_cmci
		Disable CMCI(Corrected Machine Check Interrupt) that
		Intel processor supports. Usually this disablement is
		not recommended, but it might be handy if your hardware
		is misbehaving.
		Note that you'll get more problems without CMCI than with
		due to the shared banks, i.e. you might get duplicated
		error logs.
		mce=dont_log_ce
		Don't make logs for corrected errors. All events reported
		as corrected are silently cleared by OS.
		This option will be useful if you have no interest in any
		of corrected errors.
		mce=ignore_ce
		Disable features for corrected errors, e.g. polling timer
		and CMCI. All events reported as corrected are not cleared
		by OS and remained in its error banks.
		Usually this disablement is not recommended, however if
		there is an agent checking/clearing corrected errors
		(e.g. BIOS or hardware monitoring applications), conflicting
		with OS's error handling, and you cannot deactivate the agent,
		then this option will be a help.
		mce=no_lmce
		Do not opt-in to Local MCE delivery. Use legacy method
		to broadcast MCEs.
		mce=bootlog
		Enable logging of machine checks left over from booting.
		Disabled by default on AMD Fam10h and older because some BIOS
		leave bogus ones.
		If your BIOS doesn't do that it's a good idea to enable though
		to make sure you log even machine check events that result
		in a reboot. On Intel systems it is enabled by default.
		mce=nobootlog
		Disable boot machine check logging.
		mce=monarchtimeout (number)
		monarchtimeout:
		Sets the time in us to wait for other CPUs on machine checks. 0
		to disable.
		mce=bios_cmci_threshold
		Don't overwrite the bios-set CMCI threshold. This boot option
		prevents Linux from overwriting the CMCI threshold set by the
		bios. Without this option, Linux always sets the CMCI
		threshold to 1. Enabling this may make memory predictive failure
		analysis less effective if the bios sets thresholds for memory
		errors since we will not see details for all errors.
		mce=recovery
		Force-enable recoverable machine check code paths

		nomce (for compatibility with i386)
		same as mce=off

		Everything else is in sysfs now.

		APICs
		=====

		apic
		Use IO-APIC. Default

		noapic
		Don't use the IO-APIC.

		disableapic
		Don't use the local APIC

		nolapic
		Don't use the local APIC (alias for i386 compatibility)

		pirq=...
		See Documentation/arch/x86/i386/IO-APIC.rst

		noapictimer
		Don't set up the APIC timer

		no_timer_check
		Don't check the IO-APIC timer. This can work around
		problems with incorrect timer initialization on some boards.

		apicpmtimer
		Do APIC timer calibration using the pmtimer. Implies
		apicmaintimer. Useful when your PIT timer is totally broken.

		Timing
		======

		notsc
		Deprecated, use tsc=unstable instead.

		nohpet
		Don't use the HPET timer.

		Idle loop
		=========

		idle=poll
		Don't do power saving in the idle loop using HLT, but poll for rescheduling
		event. This will make the CPUs eat a lot more power, but may be useful
		to get slightly better performance in multiprocessor benchmarks. It also
		makes some profiling using performance counters more accurate.
		Please note that on systems with MONITOR/MWAIT support (like Intel EM64T
		CPUs) this option has no performance advantage over the normal idle loop.
		It may also interact badly with hyperthreading.

		Rebooting
		=========

		reboot=b[ios] \| t[riple] \| k[bd] \| a[cpi] \| e[fi] \| p[ci] [, [w]arm \| [c]old]
		bios
		Use the CPU reboot vector for warm reset
		warm
		Don't set the cold reboot flag
		cold
		Set the cold reboot flag
		triple
		Force a triple fault (init)
		kbd
		Use the keyboard controller. cold reset (default)
		acpi
		Use the ACPI RESET_REG in the FADT. If ACPI is not configured or
		the ACPI reset does not work, the reboot path attempts the reset
		using the keyboard controller.
		efi
		Use efi reset_system runtime service. If EFI is not configured or
		the EFI reset does not work, the reboot path attempts the reset using
		the keyboard controller.
		pci
		Use a write to the PCI config space register 0xcf9 to trigger reboot.

		Using warm reset will be much faster especially on big memory
		systems because the BIOS will not go through the memory check.
		Disadvantage is that not all hardware will be completely reinitialized
		on reboot so there may be boot problems on some systems.

		reboot=force
		Don't stop other CPUs on reboot. This can make reboot more reliable
		in some cases.

		reboot=default
		There are some built-in platform specific "quirks" - you may see:
		"reboot: <name> series board detected. Selecting <type> for reboots."
		In the case where you think the quirk is in error (e.g. you have
		newer BIOS, or newer board) using this option will ignore the built-in
		quirk table, and use the generic default reboot actions.

		NUMA
		====

		numa=off
		Only set up a single NUMA node spanning all memory.

		numa=noacpi
		Don't parse the SRAT table for NUMA setup

		numa=nohmat
		Don't parse the HMAT table for NUMA setup, or soft-reserved memory
		partitioning.

		ACPI
		====

		acpi=off
		Don't enable ACPI
		acpi=ht
		Use ACPI boot table parsing, but don't enable ACPI interpreter
		acpi=force
		Force ACPI on (currently not needed)
		acpi=strict
		Disable out of spec ACPI workarounds.
		acpi_sci={edge,level,high,low}
		Set up ACPI SCI interrupt.
		acpi=noirq
		Don't route interrupts
		acpi=nocmcff
		Disable firmware first mode for corrected errors. This
		disables parsing the HEST CMC error source to check if
		firmware has set the FF flag. This may result in
		duplicate corrected error reports.

		PCI
		===

		pci=off
		Don't use PCI
		pci=conf1
		Use conf1 access.
		pci=conf2
		Use conf2 access.
		pci=rom
		Assign ROMs.
		pci=assign-busses
		Assign busses
		pci=irqmask=MASK
		Set PCI interrupt mask to MASK
		pci=lastbus=NUMBER
		Scan up to NUMBER busses, no matter what the mptable says.
		pci=noacpi
		Don't use ACPI to set up PCI interrupt routing.

		IOMMU (input/output memory management unit)
		===========================================
		Multiple x86-64 PCI-DMA mapping implementations exist, for example:

		1. <kernel/dma/direct.c>: use no hardware/software IOMMU at all
		(e.g. because you have < 3 GB memory).
		Kernel boot message: "PCI-DMA: Disabling IOMMU"

		2. <arch/x86/kernel/amd_gart_64.c>: AMD GART based hardware IOMMU.
		Kernel boot message: "PCI-DMA: using GART IOMMU"

		3. <arch/x86_64/kernel/pci-swiotlb.c> : Software IOMMU implementation. Used
		e.g. if there is no hardware IOMMU in the system and it is need because
		you have >3GB memory or told the kernel to us it (iommu=soft))
		Kernel boot message: "PCI-DMA: Using software bounce buffering
		for IO (SWIOTLB)"

		::

		iommu=[<size>][,noagp][,off][,force][,noforce]
		[,memaper[=<order>]][,merge][,fullflush][,nomerge]
		[,noaperture]

		General iommu options:

		off
		Don't initialize and use any kind of IOMMU.
		noforce
		Don't force hardware IOMMU usage when it is not needed. (default).
		force
		Force the use of the hardware IOMMU even when it is
		not actually needed (e.g. because < 3 GB memory).
		soft
		Use software bounce buffering (SWIOTLB) (default for
		Intel machines). This can be used to prevent the usage
		of an available hardware IOMMU.

		iommu options only relevant to the AMD GART hardware IOMMU:

		<size>
		Set the size of the remapping area in bytes.
		allowed
		Overwrite iommu off workarounds for specific chipsets.
		fullflush
		Flush IOMMU on each allocation (default).
		nofullflush
		Don't use IOMMU fullflush.
		memaper[=<order>]
		Allocate an own aperture over RAM with size 32MB<<order.
		(default: order=1, i.e. 64MB)
		merge
		Do scatter-gather (SG) merging. Implies "force" (experimental).
		nomerge
		Don't do scatter-gather (SG) merging.
		noaperture
		Ask the IOMMU not to touch the aperture for AGP.
		noagp
		Don't initialize the AGP driver and use full aperture.
		panic
		Always panic when IOMMU overflows.

		iommu options only relevant to the software bounce buffering (SWIOTLB) IOMMU
		implementation:

		swiotlb=<slots>[,force,noforce]
		<slots>
		Prereserve that many 2K slots for the software IO bounce buffering.
		force
		Force all IO through the software TLB.
		noforce
		Do not initialize the software TLB.


		Miscellaneous
		=============

		nogbpages
		Do not use GB pages for kernel direct mappings.
		gbpages
		Use GB pages for kernel direct mappings.


		AMD SEV (Secure Encrypted Virtualization)
		=========================================
		Options relating to AMD SEV, specified via the following format:

		::

		sev=option1[,option2]

		The available options are:

		debug
		Enable debug messages.

		nosnp
		Do not enable SEV-SNP (applies to host/hypervisor only). Setting
		'nosnp' avoids the RMP check overhead in memory accesses when
		users do not want to run SEV-SNP guests.

Documentation/arch/x86/x86_64/fake-numa-for-cpusets.rst

+1 −1

Original line number	Diff line number	Diff line
		@@ -18,7 +18,7 @@ For more information on the features of cpusets, see
		Documentation/admin-guide/cgroup-v1/cpusets.rst.
		There are a number of different configurations you can use for your needs. For
		more information on the numa=fake command line option and its various ways of
		configuring fake nodes, see Documentation/arch/x86/x86_64/boot-options.rst.
		configuring fake nodes, see Documentation/admin-guide/kernel-parameters.txt

		For the purposes of this introduction, we'll assume a very primitive NUMA
		emulation setup of "numa=fake=4*512,". This will split our system memory into

Documentation/arch/x86/x86_64/index.rst

+0 −1

Original line number	Diff line number	Diff line
		@@ -7,7 +7,6 @@ x86_64 Support
		.. toctree::
		:maxdepth: 2

		boot-options
		uefi
		mm
		5level-paging