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+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/x86/x86_64/machinecheck 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=bootlog
+		Enable logging of machine checks left over from booting.
+		Disabled by default on AMD 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=tolerancelevel[,monarchtimeout] (number,number)
+		tolerance levels:
+		0: always panic on uncorrected errors, log corrected errors
+		1: panic or SIGBUS on uncorrected errors, log corrected errors
+		2: SIGBUS or log uncorrected errors, log corrected errors
+		3: never panic or SIGBUS, log all errors (for testing only)
+		Default is 1
+		Can be also set using sysfs which is preferable.
+		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.
+
+   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/x86/i386/IO-APIC.txt
+
+   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
+  Don't use the CPU time stamp counter to read the wall time.
+  This can be used to work around timing problems on multiprocessor systems
+  with not properly synchronized CPUs.
+
+  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] [, [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.
+
+   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.
+
+Non Executable Mappings
+
+  noexec=on|off
+
+  on      Enable(default)
+  off     Disable
+
+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=fake=<size>[MG]
+		If given as a memory unit, fills all system RAM with nodes of
+		size interleaved over physical nodes.
+
+  numa=fake=<N>
+		If given as an integer, fills all system RAM with N fake nodes
+		interleaved over physical nodes.
+
+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)
+
+ Currently four x86-64 PCI-DMA mapping implementations exist:
+
+   1. <arch/x86_64/kernel/pci-nommu.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)"
+
+   4. <arch/x86_64/pci-calgary.c> : IBM Calgary hardware IOMMU. Used in IBM
+      pSeries and xSeries servers. This hardware IOMMU supports DMA address
+      mapping with memory protection, etc.
+      Kernel boot message: "PCI-DMA: Using Calgary IOMMU"
+
+ iommu=[<size>][,noagp][,off][,force][,noforce][,leak[=<nr_of_leak_pages>]
+	[,memaper[=<order>]][,merge][,forcesac][,fullflush][,nomerge]
+	[,noaperture][,calgary]
+
+  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.
+    leak               Turn on simple iommu leak tracing (only when
+                       CONFIG_IOMMU_LEAK is on). Default number of leak pages
+                       is 20.
+    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.
+    forcesac           Force single-address cycle (SAC) mode for masks <40bits
+                       (experimental).
+    noagp              Don't initialize the AGP driver and use full aperture.
+    allowdac           Allow double-address cycle (DAC) mode, i.e. DMA >4GB.
+                       DAC is used with 32-bit PCI to push a 64-bit address in
+                       two cycles. When off all DMA over >4GB is forced through
+                       an IOMMU or software bounce buffering.
+    nodac              Forbid DAC mode, i.e. DMA >4GB.
+    panic              Always panic when IOMMU overflows.
+    calgary            Use the Calgary IOMMU if it is available
+
+  iommu options only relevant to the software bounce buffering (SWIOTLB) IOMMU
+  implementation:
+    swiotlb=<pages>[,force]
+    <pages>            Prereserve that many 128K pages for the software IO
+                       bounce buffering.
+    force              Force all IO through the software TLB.
+
+  Settings for the IBM Calgary hardware IOMMU currently found in IBM
+  pSeries and xSeries machines:
+
+    calgary=[64k,128k,256k,512k,1M,2M,4M,8M]
+    calgary=[translate_empty_slots]
+    calgary=[disable=<PCI bus number>]
+    panic              Always panic when IOMMU overflows
+
+    64k,...,8M - Set the size of each PCI slot's translation table
+    when using the Calgary IOMMU. This is the size of the translation
+    table itself in main memory. The smallest table, 64k, covers an IO
+    space of 32MB; the largest, 8MB table, can cover an IO space of
+    4GB. Normally the kernel will make the right choice by itself.
+
+    translate_empty_slots - Enable translation even on slots that have
+    no devices attached to them, in case a device will be hotplugged
+    in the future.
+
+    disable=<PCI bus number> - Disable translation on a given PHB. For
+    example, the built-in graphics adapter resides on the first bridge
+    (PCI bus number 0); if translation (isolation) is enabled on this
+    bridge, X servers that access the hardware directly from user
+    space might stop working. Use this option if you have devices that
+    are accessed from userspace directly on some PCI host bridge.
+
+Debugging
+
+  kstack=N	Print N words from the kernel stack in oops dumps.
+
+Miscellaneous
+
+	nogbpages
+		Do not use GB pages for kernel direct mappings.
+	gbpages
+		Use GB pages for kernel direct mappings.