xref: /openbmc/linux/Documentation/ABI/testing/sysfs-mce (revision edfc8730)

What:		/sys/devices/system/machinecheck/machinecheckX/
Contact:	Andi Kleen <ak@linux.intel.com>
Date:		Feb, 2007
Description:
		(X = CPU number)

		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.

		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 http://one.firstfloor.org/~andi/mce.pdf

		Each CPU has its own directory.

What:		/sys/devices/system/machinecheck/machinecheckX/bank<Y>
Contact:	Andi Kleen <ak@linux.intel.com>
Date:		Feb, 2007
Description:
		(Y bank number)

		64bit Hex bitmask enabling/disabling specific subevents for
		bank Y.

		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

What:		/sys/devices/system/machinecheck/machinecheckX/check_interval
Contact:	Andi Kleen <ak@linux.intel.com>
Date:		Feb, 2007
Description:
		The 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 hexadecimal). 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.
		0 means no polling for corrected machine check errors
		(but some corrected errors might be still reported
		in other ways)

What:		/sys/devices/system/machinecheck/machinecheckX/tolerant
Contact:	Andi Kleen <ak@linux.intel.com>
Date:		Feb, 2007
Description:
		The entries appear for each CPU, but they are truly shared
		between all CPUs.

		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.

What:		/sys/devices/system/machinecheck/machinecheckX/trigger
Contact:	Andi Kleen <ak@linux.intel.com>
Date:		Feb, 2007
Description:
		The entries appear for each CPU, but they are truly shared
		between all CPUs.

		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.

What:		/sys/devices/system/machinecheck/machinecheckX/monarch_timeout
Contact:	Andi Kleen <ak@linux.intel.com>
Date:		Feb, 2007
Description:
		How long to wait for the other CPUs to machine check too on a
		exception. 0 to disable waiting for other CPUs.

		Unit: us