[PATCH] x86-64: Allow to run a program when a machine check event is detected

When a machine check event is detected (including a AMD RevF threshold
overflow event) allow to run a "trigger" program. This allows user space
to react to such events sooner.

The trigger is configured using a new trigger entry in the
machinecheck sysfs interface. It is currently shared between
all CPUs.

I also fixed the AMD threshold handler to run the machine
check polling code immediately to actually log any events
that might have caused the threshold interrupt.

Also added some documentation for the mce sysfs interface.

Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 70 insertions, 0 deletions

diff --git a/Documentation/x86_64/machinecheck b/Documentation/x86_64/machinecheck
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+
+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:
+
+Entries:
+
+bankNctl
+(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.
+
+check_interval
+        How often to poll for corrected machine check errors, in seconds
+        (Note output is hexademical). Default 5 minutes.
+
+tolerant
+        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.
+
+        0: always panic,
+        1: panic if deadlock possible,
+        2: try to avoid panic,
+        3: never panic or exit (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.
+
+trigger
+        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