summaryrefslogtreecommitdiff
path: root/Documentation/x86/x86_64/boot-options.txt
diff options
context:
space:
mode:
authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /Documentation/x86/x86_64/boot-options.txt
Initial import
Diffstat (limited to 'Documentation/x86/x86_64/boot-options.txt')
-rw-r--r--Documentation/x86/x86_64/boot-options.txt284
1 files changed, 284 insertions, 0 deletions
diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt
new file mode 100644
index 000000000..522347929
--- /dev/null
+++ b/Documentation/x86/x86_64/boot-options.txt
@@ -0,0 +1,284 @@
+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.