Re: [PATCH v3] x86/mce: Try printing all machine check banks known before panic

From: Borislav Petkov
Date: Thu Nov 20 2014 - 05:15:16 EST

On Wed, Nov 19, 2014 at 11:34:10PM +0000, Luck, Tony wrote:
> The SDM has this to say about EN=0 (in section of volume 3B):
> When the EN flag is zero but the VAL and UC flags are one in
> the IA32_MCi_STATUS register, the reported uncorrected error
> in this bank is not enabled. As uncorrected errors with the
> EN flag = 0 are not the source of machine check exceptions,
> the MCE handler should log and clear non-enabled errors when
> the S bit is set and should continue searching for enabled
> errors from the other IA32_MCi_STATUS registers. Note that
> when IA32_MCG_CAP [24] is 0, any uncorrected error condition
> (VAL =1 and UC=1) including the one with the EN flag cleared
> are fatal and the handler must signal the operating system to
> reset the system. For the errors that do not generate machine
> check exceptions, the EN flag has no meaning.
> Note the "should log and clear". We just clear ... just need to shuffle some code
> in mce.c to add the logging.

Sure, we can log those.

> But we still need something like Rui's patch - calling mcelog()
> doesn't ensure that we see something on the console about possible
> cause of the problem.

So you're saying we should drain the mcelog buffer to the console in
such situations before we panic? If so, there's drain_mcelog_buffer()
which could be changed to call print_mce() instead of going to the


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