linux-kernel - Re: [PATCH v3 1/2] x86, mce, severity: extend the the mce_severity mechanism to handle UCNA/DEFERRED error

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Date:	Tue, 11 Nov 2014 09:56:12 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>,
	Chen Yucong <slaoub@...il.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] x86, mce, severity: extend the the mce_severity
 mechanism to handle UCNA/DEFERRED error

On Mon, Nov 10, 2014 at 11:32:12PM +0000, Luck, Tony wrote:
> But then I tested it ...
> 
> I injected a UC error to memory - then did a simple byte write to the target line.
> This resulted in two banks logging errors:
> 
> [  124.638045] poll: CPU54 saw ec00000000010092 in bank 7
> [  124.639006] poll: severity = 0
> [  124.647333] poll: CPU54 saw b800000000200179 in bank 3
> [  124.648322] poll: severity = 1
> 
> The bank 7 error reported as severity 0 because EN=0 ... so we took no action for it.

How come EN is 0? Bank7 error reporting is not enabled? Why? Or the
error injection thing doesn't do it?

> The bank 3 error got past that hurdle, then through the next BIT(8) set indicates a
> cache error. Fell at the last check because ADDRV=0.

I guess you could tweak the injection path to write in a default address
so that that check gets bypassed...

> I think the severity table entry for the "EN" check should have been skipped
> when calling from the CMCI handler. Then we would have seen severity=1
> from the bank 7 error.  It would have passed the other tests too (BIT(7) and
> ADDRV).

... but this is yet another example that this severity table is hard to
extend and handle.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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