docs/vm: hwpoison.txt: convert to ReST format
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Mike Rapoport
Jonathan Corbet
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@ -1,7 +1,14 @@
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.. hwpoison:
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========
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hwpoison
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========
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What is hwpoison?
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=================
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Upcoming Intel CPUs have support for recovering from some memory errors
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(``MCA recovery''). This requires the OS to declare a page "poisoned",
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(``MCA recovery``). This requires the OS to declare a page "poisoned",
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kill the processes associated with it and avoid using it in the future.
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This patchkit implements the necessary infrastructure in the VM.
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@ -46,9 +53,10 @@ address. This in theory allows other applications to handle
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memory failures too. The expection is that near all applications
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won't do that, but some very specialized ones might.
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---
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Failure recovery modes
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======================
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There are two (actually three) modi memory failure recovery can be in:
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There are two (actually three) modes memory failure recovery can be in:
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vm.memory_failure_recovery sysctl set to zero:
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All memory failures cause a panic. Do not attempt recovery.
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@ -67,9 +75,8 @@ late kill
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This is best for memory error unaware applications and default
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Note some pages are always handled as late kill.
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---
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User control:
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User control
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============
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vm.memory_failure_recovery
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See sysctl.txt
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@ -79,11 +86,19 @@ vm.memory_failure_early_kill
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PR_MCE_KILL
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Set early/late kill mode/revert to system default
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arg1: PR_MCE_KILL_CLEAR: Revert to system default
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arg1: PR_MCE_KILL_SET: arg2 defines thread specific mode
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PR_MCE_KILL_EARLY: Early kill
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PR_MCE_KILL_LATE: Late kill
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PR_MCE_KILL_DEFAULT: Use system global default
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arg1: PR_MCE_KILL_CLEAR:
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Revert to system default
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arg1: PR_MCE_KILL_SET:
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arg2 defines thread specific mode
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PR_MCE_KILL_EARLY:
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Early kill
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PR_MCE_KILL_LATE:
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Late kill
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PR_MCE_KILL_DEFAULT
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Use system global default
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Note that if you want to have a dedicated thread which handles
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the SIGBUS(BUS_MCEERR_AO) on behalf of the process, you should
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call prctl(PR_MCE_KILL_EARLY) on the designated thread. Otherwise,
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@ -92,48 +107,38 @@ PR_MCE_KILL
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PR_MCE_KILL_GET
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return current mode
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Testing
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=======
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---
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* madvise(MADV_HWPOISON, ....) (as root) - Poison a page in the
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process for testing
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Testing:
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* hwpoison-inject module through debugfs ``/sys/kernel/debug/hwpoison/``
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madvise(MADV_HWPOISON, ....)
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(as root)
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Poison a page in the process for testing
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corrupt-pfn
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Inject hwpoison fault at PFN echoed into this file. This does
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some early filtering to avoid corrupted unintended pages in test suites.
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unpoison-pfn
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Software-unpoison page at PFN echoed into this file. This way
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a page can be reused again. This only works for Linux
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injected failures, not for real memory failures.
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hwpoison-inject module through debugfs
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Note these injection interfaces are not stable and might change between
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kernel versions
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/sys/kernel/debug/hwpoison/
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corrupt-filter-dev-major, corrupt-filter-dev-minor
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Only handle memory failures to pages associated with the file
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system defined by block device major/minor. -1U is the
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wildcard value. This should be only used for testing with
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artificial injection.
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corrupt-pfn
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corrupt-filter-memcg
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Limit injection to pages owned by memgroup. Specified by inode
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number of the memcg.
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Inject hwpoison fault at PFN echoed into this file. This does
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some early filtering to avoid corrupted unintended pages in test suites.
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Example::
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unpoison-pfn
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Software-unpoison page at PFN echoed into this file. This
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way a page can be reused again.
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This only works for Linux injected failures, not for real
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memory failures.
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Note these injection interfaces are not stable and might change between
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kernel versions
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corrupt-filter-dev-major
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corrupt-filter-dev-minor
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Only handle memory failures to pages associated with the file system defined
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by block device major/minor. -1U is the wildcard value.
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This should be only used for testing with artificial injection.
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corrupt-filter-memcg
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Limit injection to pages owned by memgroup. Specified by inode number
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of the memcg.
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Example:
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mkdir /sys/fs/cgroup/mem/hwpoison
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usemem -m 100 -s 1000 &
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@ -145,24 +150,21 @@ Example:
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page-types -p `pidof init` --hwpoison # shall do nothing
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page-types -p `pidof usemem` --hwpoison # poison its pages
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corrupt-filter-flags-mask
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corrupt-filter-flags-value
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corrupt-filter-flags-mask, corrupt-filter-flags-value
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When specified, only poison pages if ((page_flags & mask) ==
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value). This allows stress testing of many kinds of
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pages. The page_flags are the same as in /proc/kpageflags. The
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flag bits are defined in include/linux/kernel-page-flags.h and
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documented in Documentation/vm/pagemap.txt
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When specified, only poison pages if ((page_flags & mask) == value).
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This allows stress testing of many kinds of pages. The page_flags
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are the same as in /proc/kpageflags. The flag bits are defined in
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include/linux/kernel-page-flags.h and documented in
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Documentation/vm/pagemap.txt
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* Architecture specific MCE injector
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Architecture specific MCE injector
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x86 has mce-inject, mce-test
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x86 has mce-inject, mce-test
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Some portable hwpoison test programs in mce-test, see below.
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Some portable hwpoison test programs in mce-test, see blow.
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---
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References:
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References
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==========
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http://halobates.de/mce-lc09-2.pdf
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Overview presentation from LinuxCon 09
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@ -174,14 +176,11 @@ git://git.kernel.org/pub/scm/utils/cpu/mce/mce-inject.git
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x86 specific injector
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---
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Limitations:
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Limitations
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===========
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- Not all page types are supported and never will. Most kernel internal
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objects cannot be recovered, only LRU pages for now.
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objects cannot be recovered, only LRU pages for now.
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- Right now hugepage support is missing.
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---
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Andi Kleen, Oct 2009
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