1What:		/sys/devices/system/machinecheck/machinecheckX/tolerant
2Contact:	Borislav Petkov <bp@suse.de>
3Date:		Dec, 2021
4Description:
5		Unused and obsolete after the advent of recoverable machine
6		checks (see last sentence below) and those are present since
7		2010 (Nehalem).
8
9		Original description:
10
11		The entries appear for each CPU, but they are truly shared
12		between all CPUs.
13
14		Tolerance level. When a machine check exception occurs for a
15		non corrected machine check the kernel can take different
16		actions.
17
18		Since machine check exceptions can happen any time it is
19		sometimes risky for the kernel to kill a process because it
20		defies normal kernel locking rules. The tolerance level
21		configures how hard the kernel tries to recover even at some
22		risk of	deadlock. Higher tolerant values trade potentially
23		better uptime with the risk of a crash or even corruption
24		(for tolerant >= 3).
25
26		==  ===========================================================
27		 0  always panic on uncorrected errors, log corrected errors
28		 1  panic or SIGBUS on uncorrected errors, log corrected errors
29		 2  SIGBUS or log uncorrected errors, log corrected errors
30		 3  never panic or SIGBUS, log all errors (for testing only)
31		==  ===========================================================
32
33		Default: 1
34
35		Note this only makes a difference if the CPU allows recovery
36		from a machine check exception. Current x86 CPUs generally
37		do not.
38