linux-kernel - RE: [PATCH v2 1/2] x86/mce/AMD: Redo use of SMCA MCA

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Date:   Tue, 11 Apr 2017 13:32:03 +0000
From:   "Ghannam, Yazen" <Yazen.Ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        Tony Luck <tony.luck@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 1/2] x86/mce/AMD: Redo use of SMCA MCA_DE{STAT,ADDR}
 registers

> -----Original Message-----
> From: Borislav Petkov [mailto:bp@...en8.de]
> Sent: Tuesday, April 11, 2017 9:25 AM
> To: Ghannam, Yazen <Yazen.Ghannam@....com>
> Cc: linux-edac@...r.kernel.org; Tony Luck <tony.luck@...el.com>;
> x86@...nel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v2 1/2] x86/mce/AMD: Redo use of SMCA
> MCA_DE{STAT,ADDR} registers
> 
> On Tue, Apr 11, 2017 at 01:18:50PM +0000, Ghannam, Yazen wrote:
> > So log_error() reads/clears MCA_STATUS, right? This won't affect
> > MCA_DESTAT on SMCA systems. So if we call log_error_smca() and
> > unconditionally read MCA_DESTAT, we will find the same deferred error
> that we logged in log_error().
> 
> I'm reading this as, "we log the same deferred error in *both* the original
> MCA MSRs and in the new DE* ones". Correct?
> 

Yes, exactly. Deferred errors are *always* logged in the DE* registers and
they are logged in the original MSRs based on the MCA_CONFIG bit.

The idea here is that if a deferred error is overwritten in MCA_STATUS we
will still have a copy logged in MCA_DESTAT.

Thanks,
Yazen