Why write CPER_NOTIFY_MCE to ERST when reboot
Hi Tony,
With commit 0bb77c46 "pstore: X86 platform interface using ACPI/APEI/ERST" when reboot the server kernel will call erst_writer() to write CPER_NOTIFY_MCE to ERST, if reboot the server to Windows we find MCE from system event logs. Any reason write this to ERST when reboot?
Any input will appreciate!
Regards,
Joe
Quoted 7 lines · Joe Jin
Hi Tony,
With commit
0bb77c46"pstore: X86 platform interface using ACPI/APEI/ERST" when reboot the server kernel will callerst_writer()to writeCPER_NOTIFY_MCEto ERST, if reboot the server to Windows we find MCE from system event logs. Any reason write this to ERST when reboot?
Quoted 8 lines
Any input will appreciate!
Regards,
Joe
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Hi Joe,
I guess this is used to handle an uncorrectable MCE. When
uncorrectable MCE happens,
the whole disk io stack is unreliable so we couldn't write MCE record to disk, ERST is the
last method to store the MCE record and OS could retrieve this record from ERST on next
reboot.
Regards!
Gerry
Gerry has this right - we want to preserve the error information, but we don't trust our kernel enough to have it write to a regular disk (perhaps it has no access to I/O because of the error - or worse, perhaps it might write to the wrong place or the wrong disk).
In theory data the information in the machine check banks is preserved across a warm reset for the reboot - but in practice we may sometimes need a power-cycle and full cold reset. Also I've heard that on some systems the BIOS clears the banks before the OS can see them.
-Tony
Tony and Gerry, thanks!
Regards,
Joe
Quoted 12 lines · Tony
Gerry has this right - we want to preserve the error information, but we don't trust our kernel enough to have it write to a regular disk (perhaps it has no access to I/O because of the error - or worse, perhaps it might write to the wrong place or the wrong disk).
In theory data the information in the machine check banks is preserved across a warm reset for the reboot - but in practice we may sometimes need a power-cycle and full cold reset. Also I've heard that on some systems the BIOS clears the banks before the OS can see them.
-Tony
Signature · 4 lines
Oracle <http://www.oracle.com> Joe Jin | Software Development Senior Manager | +8610.6106.5624 ORACLE | Linux and Virtualization No. 24 Zhongguancun Software Park, Haidian District | 100193 Beijing