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12febc1818
commit 5955633e91bf ("x86/reboot: Skip DMI checks if reboot set by user")
made it so that it's not required to recompile the kernel in order to
bypass broken reboot quirks compiled into an image:
* This variable is used privately to keep track of whether or not
* reboot_type is still set to its default value (i.e., reboot= hasn't
* been set on the command line). This is needed so that we can
* suppress DMI scanning for reboot quirks. Without it, it's
* impossible to override a faulty reboot quirk without recompiling.
However, at the time it was not eally documented outside the source code,
and so this information isn't really available to the average user out
there.
The change is a little white lie and invented "reboot=default" since it is
easy to remember, and documents well. The truth is that any random string
that is *not* a currently accepted string will work.
Since that doesn't document well for non-coders, and since it's unknown
what the future additions might be, lay claim on "default" since that is
exactly what it achieves.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210530162447.996461-3-paul.gortmaker@windriver.com
320 lines
9.7 KiB
ReStructuredText
320 lines
9.7 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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===========================
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AMD64 Specific Boot Options
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===========================
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There are many others (usually documented in driver documentation), but
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only the AMD64 specific ones are listed here.
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Machine check
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=============
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Please see Documentation/x86/x86_64/machinecheck.rst for sysfs runtime tunables.
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mce=off
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Disable machine check
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mce=no_cmci
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Disable CMCI(Corrected Machine Check Interrupt) that
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Intel processor supports. Usually this disablement is
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not recommended, but it might be handy if your hardware
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is misbehaving.
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Note that you'll get more problems without CMCI than with
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due to the shared banks, i.e. you might get duplicated
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error logs.
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mce=dont_log_ce
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Don't make logs for corrected errors. All events reported
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as corrected are silently cleared by OS.
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This option will be useful if you have no interest in any
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of corrected errors.
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mce=ignore_ce
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Disable features for corrected errors, e.g. polling timer
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and CMCI. All events reported as corrected are not cleared
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by OS and remained in its error banks.
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Usually this disablement is not recommended, however if
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there is an agent checking/clearing corrected errors
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(e.g. BIOS or hardware monitoring applications), conflicting
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with OS's error handling, and you cannot deactivate the agent,
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then this option will be a help.
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mce=no_lmce
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Do not opt-in to Local MCE delivery. Use legacy method
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to broadcast MCEs.
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mce=bootlog
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Enable logging of machine checks left over from booting.
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Disabled by default on AMD Fam10h and older because some BIOS
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leave bogus ones.
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If your BIOS doesn't do that it's a good idea to enable though
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to make sure you log even machine check events that result
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in a reboot. On Intel systems it is enabled by default.
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mce=nobootlog
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Disable boot machine check logging.
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mce=tolerancelevel[,monarchtimeout] (number,number)
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tolerance levels:
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0: always panic on uncorrected errors, log corrected errors
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1: panic or SIGBUS on uncorrected errors, log corrected errors
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2: SIGBUS or log uncorrected errors, log corrected errors
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3: never panic or SIGBUS, log all errors (for testing only)
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Default is 1
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Can be also set using sysfs which is preferable.
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monarchtimeout:
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Sets the time in us to wait for other CPUs on machine checks. 0
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to disable.
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mce=bios_cmci_threshold
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Don't overwrite the bios-set CMCI threshold. This boot option
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prevents Linux from overwriting the CMCI threshold set by the
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bios. Without this option, Linux always sets the CMCI
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threshold to 1. Enabling this may make memory predictive failure
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analysis less effective if the bios sets thresholds for memory
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errors since we will not see details for all errors.
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mce=recovery
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Force-enable recoverable machine check code paths
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nomce (for compatibility with i386)
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same as mce=off
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Everything else is in sysfs now.
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APICs
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=====
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apic
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Use IO-APIC. Default
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noapic
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Don't use the IO-APIC.
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disableapic
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Don't use the local APIC
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nolapic
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Don't use the local APIC (alias for i386 compatibility)
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pirq=...
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See Documentation/x86/i386/IO-APIC.rst
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noapictimer
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Don't set up the APIC timer
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no_timer_check
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Don't check the IO-APIC timer. This can work around
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problems with incorrect timer initialization on some boards.
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apicpmtimer
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Do APIC timer calibration using the pmtimer. Implies
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apicmaintimer. Useful when your PIT timer is totally broken.
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Timing
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======
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notsc
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Deprecated, use tsc=unstable instead.
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nohpet
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Don't use the HPET timer.
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Idle loop
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=========
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idle=poll
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Don't do power saving in the idle loop using HLT, but poll for rescheduling
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event. This will make the CPUs eat a lot more power, but may be useful
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to get slightly better performance in multiprocessor benchmarks. It also
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makes some profiling using performance counters more accurate.
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Please note that on systems with MONITOR/MWAIT support (like Intel EM64T
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CPUs) this option has no performance advantage over the normal idle loop.
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It may also interact badly with hyperthreading.
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Rebooting
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=========
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reboot=b[ios] | t[riple] | k[bd] | a[cpi] | e[fi] | p[ci] [, [w]arm | [c]old]
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bios
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Use the CPU reboot vector for warm reset
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warm
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Don't set the cold reboot flag
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cold
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Set the cold reboot flag
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triple
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Force a triple fault (init)
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kbd
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Use the keyboard controller. cold reset (default)
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acpi
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Use the ACPI RESET_REG in the FADT. If ACPI is not configured or
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the ACPI reset does not work, the reboot path attempts the reset
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using the keyboard controller.
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efi
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Use efi reset_system runtime service. If EFI is not configured or
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the EFI reset does not work, the reboot path attempts the reset using
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the keyboard controller.
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pci
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Use a write to the PCI config space register 0xcf9 to trigger reboot.
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Using warm reset will be much faster especially on big memory
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systems because the BIOS will not go through the memory check.
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Disadvantage is that not all hardware will be completely reinitialized
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on reboot so there may be boot problems on some systems.
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reboot=force
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Don't stop other CPUs on reboot. This can make reboot more reliable
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in some cases.
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reboot=default
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There are some built-in platform specific "quirks" - you may see:
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"reboot: <name> series board detected. Selecting <type> for reboots."
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In the case where you think the quirk is in error (e.g. you have
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newer BIOS, or newer board) using this option will ignore the built-in
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quirk table, and use the generic default reboot actions.
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Non Executable Mappings
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=======================
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noexec=on|off
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on
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Enable(default)
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off
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Disable
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NUMA
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====
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numa=off
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Only set up a single NUMA node spanning all memory.
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numa=noacpi
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Don't parse the SRAT table for NUMA setup
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numa=nohmat
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Don't parse the HMAT table for NUMA setup, or soft-reserved memory
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partitioning.
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numa=fake=<size>[MG]
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If given as a memory unit, fills all system RAM with nodes of
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size interleaved over physical nodes.
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numa=fake=<N>
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If given as an integer, fills all system RAM with N fake nodes
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interleaved over physical nodes.
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numa=fake=<N>U
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If given as an integer followed by 'U', it will divide each
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physical node into N emulated nodes.
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ACPI
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====
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acpi=off
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Don't enable ACPI
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acpi=ht
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Use ACPI boot table parsing, but don't enable ACPI interpreter
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acpi=force
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Force ACPI on (currently not needed)
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acpi=strict
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Disable out of spec ACPI workarounds.
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acpi_sci={edge,level,high,low}
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Set up ACPI SCI interrupt.
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acpi=noirq
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Don't route interrupts
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acpi=nocmcff
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Disable firmware first mode for corrected errors. This
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disables parsing the HEST CMC error source to check if
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firmware has set the FF flag. This may result in
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duplicate corrected error reports.
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PCI
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===
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pci=off
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Don't use PCI
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pci=conf1
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Use conf1 access.
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pci=conf2
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Use conf2 access.
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pci=rom
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Assign ROMs.
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pci=assign-busses
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Assign busses
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pci=irqmask=MASK
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Set PCI interrupt mask to MASK
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pci=lastbus=NUMBER
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Scan up to NUMBER busses, no matter what the mptable says.
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pci=noacpi
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Don't use ACPI to set up PCI interrupt routing.
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IOMMU (input/output memory management unit)
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===========================================
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Multiple x86-64 PCI-DMA mapping implementations exist, for example:
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1. <kernel/dma/direct.c>: use no hardware/software IOMMU at all
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(e.g. because you have < 3 GB memory).
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Kernel boot message: "PCI-DMA: Disabling IOMMU"
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2. <arch/x86/kernel/amd_gart_64.c>: AMD GART based hardware IOMMU.
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Kernel boot message: "PCI-DMA: using GART IOMMU"
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3. <arch/x86_64/kernel/pci-swiotlb.c> : Software IOMMU implementation. Used
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e.g. if there is no hardware IOMMU in the system and it is need because
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you have >3GB memory or told the kernel to us it (iommu=soft))
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Kernel boot message: "PCI-DMA: Using software bounce buffering
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for IO (SWIOTLB)"
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::
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iommu=[<size>][,noagp][,off][,force][,noforce]
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[,memaper[=<order>]][,merge][,fullflush][,nomerge]
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[,noaperture]
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General iommu options:
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off
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Don't initialize and use any kind of IOMMU.
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noforce
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Don't force hardware IOMMU usage when it is not needed. (default).
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force
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Force the use of the hardware IOMMU even when it is
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not actually needed (e.g. because < 3 GB memory).
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soft
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Use software bounce buffering (SWIOTLB) (default for
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Intel machines). This can be used to prevent the usage
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of an available hardware IOMMU.
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iommu options only relevant to the AMD GART hardware IOMMU:
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<size>
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Set the size of the remapping area in bytes.
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allowed
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Overwrite iommu off workarounds for specific chipsets.
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fullflush
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Flush IOMMU on each allocation (default).
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nofullflush
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Don't use IOMMU fullflush.
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memaper[=<order>]
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Allocate an own aperture over RAM with size 32MB<<order.
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(default: order=1, i.e. 64MB)
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merge
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Do scatter-gather (SG) merging. Implies "force" (experimental).
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nomerge
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Don't do scatter-gather (SG) merging.
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noaperture
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Ask the IOMMU not to touch the aperture for AGP.
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noagp
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Don't initialize the AGP driver and use full aperture.
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panic
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Always panic when IOMMU overflows.
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iommu options only relevant to the software bounce buffering (SWIOTLB) IOMMU
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implementation:
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swiotlb=<pages>[,force]
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<pages>
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Prereserve that many 128K pages for the software IO bounce buffering.
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force
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Force all IO through the software TLB.
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Miscellaneous
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=============
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nogbpages
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Do not use GB pages for kernel direct mappings.
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gbpages
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Use GB pages for kernel direct mappings.
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