Documentation: Merge x86-specific boot options doc into kernel-parameters.txt

Documentation/arch/x86/x86_64/boot-options.rst is causing unnecessary
confusion by being a second place where one can put x86 boot options.
Move them into the main one.

Drop removed ones like "acpi=ht", while at it.

Signed-off-by: Borislav Petkov (AMD) <[e-mail]>
Reviewed-by: Sohil Mehta <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/admin-guide/kernel-parameters.rst

···
 	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
···
 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

···
 				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
···
 			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 }
···
 			none: External NMI is masked for all CPUs. This is
 			      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.
···
 
 			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.
···
 
 	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]
···
 		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" }
···
 			devices can be requested on-demand with the
 			/dev/loop-control interface.
 
-	mce		[X86-32] Machine Check Exception
+	mce=		[X86-{32,64}]
 
-	mce=option	[X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
+			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.
+
 
 	md=		[HW] RAID subsystems devices and level
 			See Documentation/admin-guide/md.rst.
···
 	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]
···
 			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
···
 			correctly or when doing power measurements to evaluate
 			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.
 
···
 
 	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.
···
 			[KNL, ARM64, RISCV, X86, EARLY]
 			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.
···
 			      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
···
 
 	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

···
-.. 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

···
 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

···
 .. toctree::
    :maxdepth: 2
 
-   boot-options
    uefi
    mm
    5level-paging

arch/x86/Kconfig.debug

···
 	  code. When you use it make sure you have a big enough
 	  IOMMU/AGP aperture.  Most of the options enabled by this can
 	  be set more finegrained using the iommu= command line
-	  options. See Documentation/arch/x86/x86_64/boot-options.rst for more
+	  options. See Documentation/admin-guide/kernel-parameters.txt for more
 	  details.
 
 config IOMMU_LEAK

arch/x86/kernel/pci-dma.c

···
 	swiotlb_init(x86_swiotlb_enable, x86_swiotlb_flags);
 }
 
-/*
- * See <Documentation/arch/x86/x86_64/boot-options.rst> for the iommu kernel
- * parameter documentation.
- */
 static __init int iommu_setup(char *p)
 {
 	iommu_merge = 1;