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Background:
The MCE handler has several paths that it can take, depending on various
conditions of the MCE status and the value of the 'tolerant' knob. The
exact semantics are not well defined and the code is a bit twisty.
Description:
This patch makes the MCE handler's behavior more clear by documenting the
behavior for various 'tolerant' levels. It also fixes or enhances
several small things in the handler. Specifically:
* If RIPV is set it is not safe to restart, so set the 'no way out'
flag rather than the 'kill it' flag.
* Don't panic() on correctable MCEs.
* If the _OVER bit is set *and* the _UC bit is set (meaning possibly
dropped uncorrected errors), set the 'no way out' flag.
* Use EIPV for testing whether an app can be killed (SIGBUS) rather
than RIPV. According to docs, EIPV indicates that the error is
related to the IP, while RIPV simply means the IP is valid to
restart from.
* Don't clear the MCi_STATUS registers until after the panic() path.
This leaves the status bits set after the panic() so clever BIOSes
can find them (and dumb BIOSes can do nothing).
This patch also calls nonseekable_open() in mce_open (as suggested by akpm).
Result:
Tolerant levels behave almost identically to how they always have, but
not it's well defined. There's a slightly higher chance of panic()ing
when multiple errors happen (a good thing, IMHO). If you take an MBE and
panic(), the error status bits are not cleared.
Alternatives:
None.
Testing:
I used software to inject correctable and uncorrectable errors. With
tolerant = 3, the system usually survives. With tolerant = 2, the system
usually panic()s (PCC) but not always. With tolerant = 1, the system
always panic()s. When the system panic()s, the BIOS is able to detect
that the cause of death was an MC4. I was not able to reproduce the
case of a non-PCC error in userspace, with EIPV, with (tolerant < 3).
That will be rare at best.
Signed-off-by: Tim Hockin <thockin@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
304 lines
12 KiB
Plaintext
304 lines
12 KiB
Plaintext
AMD64 specific boot options
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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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mce=off disable machine check
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mce=bootlog Enable logging of machine checks left over from booting.
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Disabled by default on AMD because some BIOS 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 (number)
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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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nomce (for compatibility with i386): same as mce=off
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Everything else is in sysfs now.
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APICs
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apic Use IO-APIC. Default
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noapic Don't use the IO-APIC.
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disableapic Don't use the local APIC
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nolapic Don't use the local APIC (alias for i386 compatibility)
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pirq=... See Documentation/i386/IO-APIC.txt
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noapictimer Don't set up the APIC timer
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no_timer_check 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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apicmaintimer Run time keeping from the local APIC timer instead
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of using the PIT/HPET interrupt for this. This is useful
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when the PIT/HPET interrupts are unreliable.
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noapicmaintimer Don't do time keeping using the APIC timer.
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Useful when this option was auto selected, but doesn't work.
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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
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broken.
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disable_8254_timer / enable_8254_timer
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Enable interrupt 0 timer routing over the 8254 in addition to over
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the IO-APIC. The kernel tries to set a sensible default.
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Early Console
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syntax: earlyprintk=vga
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earlyprintk=serial[,ttySn[,baudrate]]
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The early console is useful when the kernel crashes before the
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normal console is initialized. It is not enabled by
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default because it has some cosmetic problems.
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Append ,keep to not disable it when the real console takes over.
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Only vga or serial at a time, not both.
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Currently only ttyS0 and ttyS1 are supported.
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Interaction with the standard serial driver is not very good.
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The VGA output is eventually overwritten by the real console.
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Timing
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notsc
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Don't use the CPU time stamp counter to read the wall time.
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This can be used to work around timing problems on multiprocessor systems
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with not properly synchronized CPUs.
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report_lost_ticks
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Report when timer interrupts are lost because some code turned off
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interrupts for too long.
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nmi_watchdog=NUMBER[,panic]
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NUMBER can be:
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0 don't use an NMI watchdog
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1 use the IO-APIC timer for the NMI watchdog
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2 use the local APIC for the NMI watchdog using a performance counter. Note
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This will use one performance counter and the local APIC's performance
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vector.
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When panic is specified panic when an NMI watchdog timeout occurs.
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This is useful when you use a panic=... timeout and need the box
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quickly up again.
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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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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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reboot=b[ios] | t[riple] | k[bd] [, [w]arm | [c]old]
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bios Use the CPU reboot vector for warm reset
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warm Don't set the cold reboot flag
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cold Set the cold reboot flag
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triple Force a triple fault (init)
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kbd Use the keyboard controller. cold reset (default)
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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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Non Executable Mappings
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noexec=on|off
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on Enable(default)
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off Disable
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SMP
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additional_cpus=NUM Allow NUM more CPUs for hotplug
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(defaults are specified by the BIOS, see Documentation/x86_64/cpu-hotplug-spec)
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NUMA
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numa=off Only set up a single NUMA node spanning all memory.
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numa=noacpi Don't parse the SRAT table for NUMA setup
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numa=fake=CMDLINE
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If a number, fakes CMDLINE nodes and ignores NUMA setup of the
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actual machine. Otherwise, system memory is configured
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depending on the sizes and coefficients listed. For example:
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numa=fake=2*512,1024,4*256,*128
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gives two 512M nodes, a 1024M node, four 256M nodes, and the
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rest split into 128M chunks. If the last character of CMDLINE
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is a *, the remaining memory is divided up equally among its
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coefficient:
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numa=fake=2*512,2*
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gives two 512M nodes and the rest split into two nodes.
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Otherwise, the remaining system RAM is allocated to an
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additional node.
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numa=hotadd=percent
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Only allow hotadd memory to preallocate page structures upto
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percent of already available memory.
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numa=hotadd=0 will disable hotadd memory.
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ACPI
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acpi=off Don't enable ACPI
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acpi=ht Use ACPI boot table parsing, but don't enable ACPI
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interpreter
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acpi=force Force ACPI on (currently not needed)
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acpi=strict Disable out of spec ACPI workarounds.
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acpi_sci={edge,level,high,low} Set up ACPI SCI interrupt.
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acpi=noirq Don't route interrupts
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PCI
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pci=off Don't use PCI
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pci=conf1 Use conf1 access.
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pci=conf2 Use conf2 access.
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pci=rom Assign ROMs.
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pci=assign-busses Assign busses
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pci=irqmask=MASK Set PCI interrupt mask to MASK
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pci=lastbus=NUMBER Scan upto NUMBER busses, no matter what the mptable says.
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pci=noacpi Don't use ACPI to set up PCI interrupt routing.
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IOMMU (input/output memory management unit)
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Currently four x86-64 PCI-DMA mapping implementations exist:
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1. <arch/x86_64/kernel/pci-nommu.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_64/kernel/pci-gart.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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4. <arch/x86_64/pci-calgary.c> : IBM Calgary hardware IOMMU. Used in IBM
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pSeries and xSeries servers. This hardware IOMMU supports DMA address
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mapping with memory protection, etc.
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Kernel boot message: "PCI-DMA: Using Calgary IOMMU"
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iommu=[<size>][,noagp][,off][,force][,noforce][,leak[=<nr_of_leak_pages>]
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[,memaper[=<order>]][,merge][,forcesac][,fullflush][,nomerge]
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[,noaperture][,calgary]
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General iommu options:
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off Don't initialize and use any kind of IOMMU.
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noforce Don't force hardware IOMMU usage when it is not needed.
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(default).
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force 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 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> Set the size of the remapping area in bytes.
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allowed Overwrite iommu off workarounds for specific chipsets.
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fullflush Flush IOMMU on each allocation (default).
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nofullflush Don't use IOMMU fullflush.
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leak Turn on simple iommu leak tracing (only when
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CONFIG_IOMMU_LEAK is on). Default number of leak pages
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is 20.
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memaper[=<order>] 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 Do scatter-gather (SG) merging. Implies "force"
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(experimental).
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nomerge Don't do scatter-gather (SG) merging.
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noaperture Ask the IOMMU not to touch the aperture for AGP.
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forcesac Force single-address cycle (SAC) mode for masks <40bits
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(experimental).
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noagp Don't initialize the AGP driver and use full aperture.
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allowdac Allow double-address cycle (DAC) mode, i.e. DMA >4GB.
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DAC is used with 32-bit PCI to push a 64-bit address in
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two cycles. When off all DMA over >4GB is forced through
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an IOMMU or software bounce buffering.
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nodac Forbid DAC mode, i.e. DMA >4GB.
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panic Always panic when IOMMU overflows.
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calgary Use the Calgary IOMMU if it is available
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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> Prereserve that many 128K pages for the software IO
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bounce buffering.
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force Force all IO through the software TLB.
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Settings for the IBM Calgary hardware IOMMU currently found in IBM
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pSeries and xSeries machines:
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calgary=[64k,128k,256k,512k,1M,2M,4M,8M]
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calgary=[translate_empty_slots]
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calgary=[disable=<PCI bus number>]
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panic Always panic when IOMMU overflows
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64k,...,8M - Set the size of each PCI slot's translation table
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when using the Calgary IOMMU. This is the size of the translation
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table itself in main memory. The smallest table, 64k, covers an IO
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space of 32MB; the largest, 8MB table, can cover an IO space of
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4GB. Normally the kernel will make the right choice by itself.
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translate_empty_slots - Enable translation even on slots that have
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no devices attached to them, in case a device will be hotplugged
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in the future.
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disable=<PCI bus number> - Disable translation on a given PHB. For
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example, the built-in graphics adapter resides on the first bridge
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(PCI bus number 0); if translation (isolation) is enabled on this
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bridge, X servers that access the hardware directly from user
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space might stop working. Use this option if you have devices that
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are accessed from userspace directly on some PCI host bridge.
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Debugging
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oops=panic Always panic on oopses. Default is to just kill the process,
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but there is a small probability of deadlocking the machine.
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This will also cause panics on machine check exceptions.
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Useful together with panic=30 to trigger a reboot.
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kstack=N Print N words from the kernel stack in oops dumps.
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pagefaulttrace Dump all page faults. Only useful for extreme debugging
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and will create a lot of output.
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call_trace=[old|both|newfallback|new]
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old: use old inexact backtracer
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new: use new exact dwarf2 unwinder
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both: print entries from both
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newfallback: use new unwinder but fall back to old if it gets
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stuck (default)
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Miscellaneous
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