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Based on kernel version 3.13. Page generated on 2014-01-20 22:05 EST.

1	
2	Configurable sysfs parameters for the x86-64 machine check code.
3	
4	Machine checks report internal hardware error conditions detected
5	by the CPU. Uncorrected errors typically cause a machine check
6	(often with panic), corrected ones cause a machine check log entry.
7	
8	Machine checks are organized in banks (normally associated with
9	a hardware subsystem) and subevents in a bank. The exact meaning
10	of the banks and subevent is CPU specific.
11	
12	mcelog knows how to decode them.
13	
14	When you see the "Machine check errors logged" message in the system
15	log then mcelog should run to collect and decode machine check entries
16	from /dev/mcelog. Normally mcelog should be run regularly from a cronjob.
17	
18	Each CPU has a directory in /sys/devices/system/machinecheck/machinecheckN
19	(N = CPU number)
20	
21	The directory contains some configurable entries:
22	
23	Entries:
24	
25	bankNctl
26	(N bank number)
27		64bit Hex bitmask enabling/disabling specific subevents for bank N
28		When a bit in the bitmask is zero then the respective
29		subevent will not be reported.
30		By default all events are enabled.
31		Note that BIOS maintain another mask to disable specific events
32		per bank.  This is not visible here
33	
34	The following entries appear for each CPU, but they are truly shared
35	between all CPUs.
36	
37	check_interval
38		How often to poll for corrected machine check errors, in seconds
39		(Note output is hexademical). Default 5 minutes.  When the poller
40		finds MCEs it triggers an exponential speedup (poll more often) on
41		the polling interval.  When the poller stops finding MCEs, it
42		triggers an exponential backoff (poll less often) on the polling
43		interval. The check_interval variable is both the initial and
44		maximum polling interval. 0 means no polling for corrected machine
45		check errors (but some corrected errors might be still reported
46		in other ways)
47	
48	tolerant
49		Tolerance level. When a machine check exception occurs for a non
50		corrected machine check the kernel can take different actions.
51		Since machine check exceptions can happen any time it is sometimes
52		risky for the kernel to kill a process because it defies
53		normal kernel locking rules. The tolerance level configures
54		how hard the kernel tries to recover even at some risk of
55		deadlock.  Higher tolerant values trade potentially better uptime
56		with the risk of a crash or even corruption (for tolerant >= 3).
57	
58		0: always panic on uncorrected errors, log corrected errors
59		1: panic or SIGBUS on uncorrected errors, log corrected errors
60		2: SIGBUS or log uncorrected errors, log corrected errors
61		3: never panic or SIGBUS, log all errors (for testing only)
62	
63		Default: 1
64	
65		Note this only makes a difference if the CPU allows recovery
66		from a machine check exception. Current x86 CPUs generally do not.
67	
68	trigger
69		Program to run when a machine check event is detected.
70		This is an alternative to running mcelog regularly from cron
71		and allows to detect events faster.
72	monarch_timeout
73		How long to wait for the other CPUs to machine check too on a
74		exception. 0 to disable waiting for other CPUs.
75		Unit: us
76	
77	TBD document entries for AMD threshold interrupt configuration
78	
79	For more details about the x86 machine check architecture
80	see the Intel and AMD architecture manuals from their developer websites.
81	
82	For more details about the architecture see
83	see http://one.firstfloor.org/~andi/mce.pdf
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