path: root/Documentation/x86/x86_64/boot-options.txt
diff options
authorH. Peter Anvin <hpa@zytor.com>2008-05-30 17:19:03 -0700
committerH. Peter Anvin <hpa@zytor.com>2008-05-30 17:19:03 -0700
commit23deb06821442506615f34bd92ccd6a2422629d7 (patch)
tree5e95dba1471007a161e19844fab2d60d422f5423 /Documentation/x86/x86_64/boot-options.txt
parent4039feb5bae72a5fed9ba6bc1a9cfd8dfe0a8613 (diff)
x86: move x86-specific documentation into Documentation/x86
The current organization of the x86 documentation makes it appear as if the "i386" documentation doesn't apply to x86-64, which is does. Thus, move that documentation into Documentation/x86, and move the x86-64-specific stuff into Documentation/x86/x86_64 with the eventual goal to move stuff that isn't actually 64-bit specific back into Documentation/x86. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'Documentation/x86/x86_64/boot-options.txt')
1 files changed, 314 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 00000000000..b0c7b6c4abd
--- /dev/null
+++ b/Documentation/x86/x86_64/boot-options.txt
@@ -0,0 +1,314 @@
+AMD64 specific boot options
+There are many others (usually documented in driver documentation), but
+only the AMD64 specific ones are listed here.
+Machine check
+ mce=off disable machine check
+ 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 (number)
+ 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.
+ nomce (for compatibility with i386): same as mce=off
+ Everything else is in sysfs now.
+ 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/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.
+ apicmaintimer Run time keeping from the local APIC timer instead
+ of using the PIT/HPET interrupt for this. This is useful
+ when the PIT/HPET interrupts are unreliable.
+ noapicmaintimer Don't do time keeping using the APIC timer.
+ Useful when this option was auto selected, but doesn't work.
+ apicpmtimer
+ Do APIC timer calibration using the pmtimer. Implies
+ apicmaintimer. Useful when your PIT timer is totally
+ broken.
+ disable_8254_timer / enable_8254_timer
+ Enable interrupt 0 timer routing over the 8254 in addition to over
+ the IO-APIC. The kernel tries to set a sensible default.
+Early Console
+ syntax: earlyprintk=vga
+ earlyprintk=serial[,ttySn[,baudrate]]
+ The early console is useful when the kernel crashes before the
+ normal console is initialized. It is not enabled by
+ default because it has some cosmetic problems.
+ Append ,keep to not disable it when the real console takes over.
+ Only vga or serial at a time, not both.
+ Currently only ttyS0 and ttyS1 are supported.
+ Interaction with the standard serial driver is not very good.
+ The VGA output is eventually overwritten by the real console.
+ 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.
+ report_lost_ticks
+ Report when timer interrupts are lost because some code turned off
+ interrupts for too long.
+ nmi_watchdog=NUMBER[,panic]
+ NUMBER can be:
+ 0 don't use an NMI watchdog
+ 1 use the IO-APIC timer for the NMI watchdog
+ 2 use the local APIC for the NMI watchdog using a performance counter. Note
+ This will use one performance counter and the local APIC's performance
+ vector.
+ When panic is specified panic when an NMI watchdog timeout occurs.
+ This is useful when you use a panic=... timeout and need the box
+ quickly up again.
+ 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.
+ 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
+ additional_cpus=NUM Allow NUM more CPUs for hotplug
+ (defaults are specified by the BIOS, see Documentation/x86_64/cpu-hotplug-spec)
+ 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=CMDLINE
+ If a number, fakes CMDLINE nodes and ignores NUMA setup of the
+ actual machine. Otherwise, system memory is configured
+ depending on the sizes and coefficients listed. For example:
+ numa=fake=2*512,1024,4*256,*128
+ gives two 512M nodes, a 1024M node, four 256M nodes, and the
+ rest split into 128M chunks. If the last character of CMDLINE
+ is a *, the remaining memory is divided up equally among its
+ coefficient:
+ numa=fake=2*512,2*
+ gives two 512M nodes and the rest split into two nodes.
+ Otherwise, the remaining system RAM is allocated to an
+ additional node.
+ numa=hotadd=percent
+ Only allow hotadd memory to preallocate page structures upto
+ percent of already available memory.
+ numa=hotadd=0 will disable hotadd memory.
+ 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
+ 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 upto 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_64/kernel/pci-gart.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.
+ oops=panic Always panic on oopses. Default is to just kill the process,
+ but there is a small probability of deadlocking the machine.
+ This will also cause panics on machine check exceptions.
+ Useful together with panic=30 to trigger a reboot.
+ kstack=N Print N words from the kernel stack in oops dumps.
+ pagefaulttrace Dump all page faults. Only useful for extreme debugging
+ and will create a lot of output.
+ call_trace=[old|both|newfallback|new]
+ old: use old inexact backtracer
+ new: use new exact dwarf2 unwinder
+ both: print entries from both
+ newfallback: use new unwinder but fall back to old if it gets
+ stuck (default)
+ nogbpages
+ Do not use GB pages for kernel direct mappings.
+ gbpages
+ Use GB pages for kernel direct mappings.