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