Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
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linux
1
2Configurable sysfs parameters for the x86-64 machine check code.
3
4Machine checks report internal hardware error conditions detected
5by the CPU. Uncorrected errors typically cause a machine check
6(often with panic), corrected ones cause a machine check log entry.
7
8Machine checks are organized in banks (normally associated with
9a hardware subsystem) and subevents in a bank. The exact meaning
10of the banks and subevent is CPU specific.
11
12mcelog knows how to decode them.
13
14When you see the "Machine check errors logged" message in the system
15log then mcelog should run to collect and decode machine check entries
16from /dev/mcelog. Normally mcelog should be run regularly from a cronjob.
17
18Each CPU has a directory in /sys/devices/system/machinecheck/machinecheckN
19(N = CPU number)
20
21The directory contains some configurable entries:
22
23Entries:
24
25bankNctl
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
34The following entries appear for each CPU, but they are truly shared
35between all CPUs.
36
37check_interval
38 How often to poll for corrected machine check errors, in seconds
39 (Note output is hexademical). Default 5 minutes.
40
41tolerant
42 Tolerance level. When a machine check exception occurs for a non
43 corrected machine check the kernel can take different actions.
44 Since machine check exceptions can happen any time it is sometimes
45 risky for the kernel to kill a process because it defies
46 normal kernel locking rules. The tolerance level configures
47 how hard the kernel tries to recover even at some risk of deadlock.
48
49 0: always panic,
50 1: panic if deadlock possible,
51 2: try to avoid panic,
52 3: never panic or exit (for testing only)
53
54 Default: 1
55
56 Note this only makes a difference if the CPU allows recovery
57 from a machine check exception. Current x86 CPUs generally do not.
58
59trigger
60 Program to run when a machine check event is detected.
61 This is an alternative to running mcelog regularly from cron
62 and allows to detect events faster.
63
64TBD document entries for AMD threshold interrupt configuration
65
66For more details about the x86 machine check architecture
67see the Intel and AMD architecture manuals from their developer websites.
68
69For more details about the architecture see
70see http://one.firstfloor.org/~andi/mce.pdf