path: root/Documentation/x86/x86_64
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
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')
8 files changed, 660 insertions, 0 deletions
diff --git a/Documentation/x86/x86_64/00-INDEX b/Documentation/x86/x86_64/00-INDEX
new file mode 100644
index 000000000000..92fc20ab5f0e
--- /dev/null
+++ b/Documentation/x86/x86_64/00-INDEX
@@ -0,0 +1,16 @@
+ - This file
+ - AMD64-specific boot options.
+ - Firmware support for CPU hotplug under Linux/x86-64
+ - Using numa=fake and CPUSets for Resource Management
+ - Context-specific per-processor interrupt stacks.
+ - Configurable sysfs parameters for the x86-64 machine check code.
+ - Memory layout of x86-64 (4 level page tables, 46 bits physical).
+ - Booting Linux via Unified Extensible Firmware Interface.
diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt
new file mode 100644
index 000000000000..b0c7b6c4abda
--- /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.
diff --git a/Documentation/x86/x86_64/cpu-hotplug-spec b/Documentation/x86/x86_64/cpu-hotplug-spec
new file mode 100644
index 000000000000..3c23e0587db3
--- /dev/null
+++ b/Documentation/x86/x86_64/cpu-hotplug-spec
@@ -0,0 +1,21 @@
+Firmware support for CPU hotplug under Linux/x86-64
+Linux/x86-64 supports CPU hotplug now. For various reasons Linux wants to
+know in advance of boot time the maximum number of CPUs that could be plugged
+into the system. ACPI 3.0 currently has no official way to supply
+this information from the firmware to the operating system.
+In ACPI each CPU needs an LAPIC object in the MADT table ( in the
+ACPI 3.0 specification). ACPI already has the concept of disabled LAPIC
+objects by setting the Enabled bit in the LAPIC object to zero.
+For CPU hotplug Linux/x86-64 expects now that any possible future hotpluggable
+CPU is already available in the MADT. If the CPU is not available yet
+it should have its LAPIC Enabled bit set to 0. Linux will use the number
+of disabled LAPICs to compute the maximum number of future CPUs.
+In the worst case the user can overwrite this choice using a command line
+option (additional_cpus=...), but it is recommended to supply the correct
+number (or a reasonable approximation of it, with erring towards more not less)
+in the MADT to avoid manual configuration.
diff --git a/Documentation/x86/x86_64/fake-numa-for-cpusets b/Documentation/x86/x86_64/fake-numa-for-cpusets
new file mode 100644
index 000000000000..d1a985c5b00a
--- /dev/null
+++ b/Documentation/x86/x86_64/fake-numa-for-cpusets
@@ -0,0 +1,66 @@
+Using numa=fake and CPUSets for Resource Management
+Written by David Rientjes <rientjes@cs.washington.edu>
+This document describes how the numa=fake x86_64 command-line option can be used
+in conjunction with cpusets for coarse memory management. Using this feature,
+you can create fake NUMA nodes that represent contiguous chunks of memory and
+assign them to cpusets and their attached tasks. This is a way of limiting the
+amount of system memory that are available to a certain class of tasks.
+For more information on the features of cpusets, see Documentation/cpusets.txt.
+There are a number of different configurations you can use for your needs. For
+more information on the numa=fake command line option and its various ways of
+configuring fake nodes, see Documentation/x86_64/boot-options.txt.
+For the purposes of this introduction, we'll assume a very primitive NUMA
+emulation setup of "numa=fake=4*512,". This will split our system memory into
+four equal chunks of 512M each that we can now use to assign to cpusets. As
+you become more familiar with using this combination for resource control,
+you'll determine a better setup to minimize the number of nodes you have to deal
+A machine may be split as follows with "numa=fake=4*512," as reported by dmesg:
+ Faking node 0 at 0000000000000000-0000000020000000 (512MB)
+ Faking node 1 at 0000000020000000-0000000040000000 (512MB)
+ Faking node 2 at 0000000040000000-0000000060000000 (512MB)
+ Faking node 3 at 0000000060000000-0000000080000000 (512MB)
+ ...
+ On node 0 totalpages: 130975
+ On node 1 totalpages: 131072
+ On node 2 totalpages: 131072
+ On node 3 totalpages: 131072
+Now following the instructions for mounting the cpusets filesystem from
+Documentation/cpusets.txt, you can assign fake nodes (i.e. contiguous memory
+address spaces) to individual cpusets:
+ [root@xroads /]# mkdir exampleset
+ [root@xroads /]# mount -t cpuset none exampleset
+ [root@xroads /]# mkdir exampleset/ddset
+ [root@xroads /]# cd exampleset/ddset
+ [root@xroads /exampleset/ddset]# echo 0-1 > cpus
+ [root@xroads /exampleset/ddset]# echo 0-1 > mems
+Now this cpuset, 'ddset', will only allowed access to fake nodes 0 and 1 for
+memory allocations (1G).
+You can now assign tasks to these cpusets to limit the memory resources
+available to them according to the fake nodes assigned as mems:
+ [root@xroads /exampleset/ddset]# echo $$ > tasks
+ [root@xroads /exampleset/ddset]# dd if=/dev/zero of=tmp bs=1024 count=1G
+ [1] 13425
+Notice the difference between the system memory usage as reported by
+/proc/meminfo between the restricted cpuset case above and the unrestricted
+case (i.e. running the same 'dd' command without assigning it to a fake NUMA
+ Unrestricted Restricted
+ MemTotal: 3091900 kB 3091900 kB
+ MemFree: 42113 kB 1513236 kB
+This allows for coarse memory management for the tasks you assign to particular
+cpusets. Since cpusets can form a hierarchy, you can create some pretty
+interesting combinations of use-cases for various classes of tasks for your
+memory management needs.
diff --git a/Documentation/x86/x86_64/kernel-stacks b/Documentation/x86/x86_64/kernel-stacks
new file mode 100644
index 000000000000..5ad65d51fb95
--- /dev/null
+++ b/Documentation/x86/x86_64/kernel-stacks
@@ -0,0 +1,99 @@
+Most of the text from Keith Owens, hacked by AK
+x86_64 page size (PAGE_SIZE) is 4K.
+Like all other architectures, x86_64 has a kernel stack for every
+active thread. These thread stacks are THREAD_SIZE (2*PAGE_SIZE) big.
+These stacks contain useful data as long as a thread is alive or a
+zombie. While the thread is in user space the kernel stack is empty
+except for the thread_info structure at the bottom.
+In addition to the per thread stacks, there are specialized stacks
+associated with each CPU. These stacks are only used while the kernel
+is in control on that CPU; when a CPU returns to user space the
+specialized stacks contain no useful data. The main CPU stacks are:
+* Interrupt stack. IRQSTACKSIZE
+ Used for external hardware interrupts. If this is the first external
+ hardware interrupt (i.e. not a nested hardware interrupt) then the
+ kernel switches from the current task to the interrupt stack. Like
+ the split thread and interrupt stacks on i386 (with CONFIG_4KSTACKS),
+ this gives more room for kernel interrupt processing without having
+ to increase the size of every per thread stack.
+ The interrupt stack is also used when processing a softirq.
+Switching to the kernel interrupt stack is done by software based on a
+per CPU interrupt nest counter. This is needed because x86-64 "IST"
+hardware stacks cannot nest without races.
+x86_64 also has a feature which is not available on i386, the ability
+to automatically switch to a new stack for designated events such as
+double fault or NMI, which makes it easier to handle these unusual
+events on x86_64. This feature is called the Interrupt Stack Table
+(IST). There can be up to 7 IST entries per CPU. The IST code is an
+index into the Task State Segment (TSS). The IST entries in the TSS
+point to dedicated stacks; each stack can be a different size.
+An IST is selected by a non-zero value in the IST field of an
+interrupt-gate descriptor. When an interrupt occurs and the hardware
+loads such a descriptor, the hardware automatically sets the new stack
+pointer based on the IST value, then invokes the interrupt handler. If
+software wants to allow nested IST interrupts then the handler must
+adjust the IST values on entry to and exit from the interrupt handler.
+(This is occasionally done, e.g. for debug exceptions.)
+Events with different IST codes (i.e. with different stacks) can be
+nested. For example, a debug interrupt can safely be interrupted by an
+NMI. arch/x86_64/kernel/entry.S::paranoidentry adjusts the stack
+pointers on entry to and exit from all IST events, in theory allowing
+IST events with the same code to be nested. However in most cases, the
+stack size allocated to an IST assumes no nesting for the same code.
+If that assumption is ever broken then the stacks will become corrupt.
+The currently assigned IST stacks are :-
+ Used for interrupt 12 - Stack Fault Exception (#SS).
+ This allows the CPU to recover from invalid stack segments. Rarely
+ happens.
+ Used for interrupt 8 - Double Fault Exception (#DF).
+ Invoked when handling one exception causes another exception. Happens
+ when the kernel is very confused (e.g. kernel stack pointer corrupt).
+ Using a separate stack allows the kernel to recover from it well enough
+ in many cases to still output an oops.
+ Used for non-maskable interrupts (NMI).
+ NMI can be delivered at any time, including when the kernel is in the
+ middle of switching stacks. Using IST for NMI events avoids making
+ assumptions about the previous state of the kernel stack.
+ Used for hardware debug interrupts (interrupt 1) and for software
+ debug interrupts (INT3).
+ When debugging a kernel, debug interrupts (both hardware and
+ software) can occur at any time. Using IST for these interrupts
+ avoids making assumptions about the previous state of the kernel
+ stack.
+ Used for interrupt 18 - Machine Check Exception (#MC).
+ MCE can be delivered at any time, including when the kernel is in the
+ middle of switching stacks. Using IST for MCE events avoids making
+ assumptions about the previous state of the kernel stack.
+For more details see the Intel IA32 or AMD AMD64 architecture manuals.
diff --git a/Documentation/x86/x86_64/machinecheck b/Documentation/x86/x86_64/machinecheck
new file mode 100644
index 000000000000..a05e58e7b159
--- /dev/null
+++ b/Documentation/x86/x86_64/machinecheck
@@ -0,0 +1,77 @@
+Configurable sysfs parameters for the x86-64 machine check code.
+Machine checks report internal hardware error conditions detected
+by the CPU. Uncorrected errors typically cause a machine check
+(often with panic), corrected ones cause a machine check log entry.
+Machine checks are organized in banks (normally associated with
+a hardware subsystem) and subevents in a bank. The exact meaning
+of the banks and subevent is CPU specific.
+mcelog knows how to decode them.
+When you see the "Machine check errors logged" message in the system
+log then mcelog should run to collect and decode machine check entries
+from /dev/mcelog. Normally mcelog should be run regularly from a cronjob.
+Each CPU has a directory in /sys/devices/system/machinecheck/machinecheckN
+(N = CPU number)
+The directory contains some configurable entries:
+(N bank number)
+ 64bit Hex bitmask enabling/disabling specific subevents for bank N
+ When a bit in the bitmask is zero then the respective
+ subevent will not be reported.
+ By default all events are enabled.
+ Note that BIOS maintain another mask to disable specific events
+ per bank. This is not visible here
+The following entries appear for each CPU, but they are truly shared
+between all CPUs.
+ How often to poll for corrected machine check errors, in seconds
+ (Note output is hexademical). Default 5 minutes. When the poller
+ finds MCEs it triggers an exponential speedup (poll more often) on
+ the polling interval. When the poller stops finding MCEs, it
+ triggers an exponential backoff (poll less often) on the polling
+ interval. The check_interval variable is both the initial and
+ maximum polling interval.
+ Tolerance level. When a machine check exception occurs for a non
+ corrected machine check the kernel can take different actions.
+ Since machine check exceptions can happen any time it is sometimes
+ risky for the kernel to kill a process because it defies
+ normal kernel locking rules. The tolerance level configures
+ how hard the kernel tries to recover even at some risk of
+ deadlock. Higher tolerant values trade potentially better uptime
+ with the risk of a crash or even corruption (for tolerant >= 3).
+ 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: 1
+ Note this only makes a difference if the CPU allows recovery
+ from a machine check exception. Current x86 CPUs generally do not.
+ Program to run when a machine check event is detected.
+ This is an alternative to running mcelog regularly from cron
+ and allows to detect events faster.
+TBD document entries for AMD threshold interrupt configuration
+For more details about the x86 machine check architecture
+see the Intel and AMD architecture manuals from their developer websites.
+For more details about the architecture see
+see http://one.firstfloor.org/~andi/mce.pdf
diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt
new file mode 100644
index 000000000000..b89b6d2bebfa
--- /dev/null
+++ b/Documentation/x86/x86_64/mm.txt
@@ -0,0 +1,29 @@
+<previous description obsolete, deleted>
+Virtual memory map with 4 level page tables:
+0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
+hole caused by [48:63] sign extension
+ffff800000000000 - ffff80ffffffffff (=40 bits) guard hole
+ffff810000000000 - ffffc0ffffffffff (=46 bits) direct mapping of all phys. memory
+ffffc10000000000 - ffffc1ffffffffff (=40 bits) hole
+ffffc20000000000 - ffffe1ffffffffff (=45 bits) vmalloc/ioremap space
+ffffe20000000000 - ffffe2ffffffffff (=40 bits) virtual memory map (1TB)
+... unused hole ...
+ffffffff80000000 - ffffffff82800000 (=40 MB) kernel text mapping, from phys 0
+... unused hole ...
+ffffffff88000000 - fffffffffff00000 (=1919 MB) module mapping space
+The direct mapping covers all memory in the system up to the highest
+memory address (this means in some cases it can also include PCI memory
+vmalloc space is lazily synchronized into the different PML4 pages of
+the processes using the page fault handler, with init_level4_pgt as
+Current X86-64 implementations only support 40 bits of address space,
+but we support up to 46 bits. This expands into MBZ space in the page tables.
+-Andi Kleen, Jul 2004
diff --git a/Documentation/x86/x86_64/uefi.txt b/Documentation/x86/x86_64/uefi.txt
new file mode 100644
index 000000000000..7d77120a5184
--- /dev/null
+++ b/Documentation/x86/x86_64/uefi.txt
@@ -0,0 +1,38 @@
+General note on [U]EFI x86_64 support
+The nomenclature EFI and UEFI are used interchangeably in this document.
+Although the tools below are _not_ needed for building the kernel,
+the needed bootloader support and associated tools for x86_64 platforms
+with EFI firmware and specifications are listed below.
+1. UEFI specification: http://www.uefi.org
+2. Booting Linux kernel on UEFI x86_64 platform requires bootloader
+ support. Elilo with x86_64 support can be used.
+3. x86_64 platform with EFI/UEFI firmware.
+- Build the kernel with the following configuration.
+ If EFI runtime services are expected, the following configuration should
+ be selected.
+ CONFIG_EFI_VARS=y or m # optional
+- Create a VFAT partition on the disk
+- Copy the following to the VFAT partition:
+ elilo bootloader with x86_64 support, elilo configuration file,
+ kernel image built in first step and corresponding
+ initrd. Instructions on building elilo and its dependencies
+ can be found in the elilo sourceforge project.
+- Boot to EFI shell and invoke elilo choosing the kernel image built
+ in first step.
+- If some or all EFI runtime services don't work, you can try following
+ kernel command line parameters to turn off some or all EFI runtime
+ services.
+ noefi turn off all EFI runtime services
+ reboot_type=k turn off EFI reboot runtime service

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