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

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Date:   Wed, 5 Apr 2017 19:29:48 +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: Wednesday, April 05, 2017 2:22 PM
> 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
> 
> 
> > How does log_error() know if we can't use the normal MSRs?
> 
> MCI_STATUS_VAL.
> 
> > We check for MCI_STATUS_VAL in log_error().
> 
> Yes.
> 
> > We also need to check for MCI_STATUS_DEFERRED but only if we're coming
> > from the deferred error handler.
> 
> Why? We *are* coming from the #DF handler so are you expecting a
> different type of error in the MSRs?
> 

Yes, there could be depending on how MCA_CONFIG[LogDeferredInMcaStat] is
set among other things.

If it's set, then I expect a Deferred error in MCA_STATUS since any Correctable
Errors will be overwritten. Multiple bank types can generate Deferred errors
so there may also be cases where for some types a valid Uncorrectable error
happens and overwrites the Deferred error before we can handle it. In which
case we lose the Deferred error if we don't check MCA_DESTAT.

If it's not set, then it's possible to have a valid Correctable error in MCA_STATUS
while the valid Deferred error is in MCA_DESTAT.

Right now MCA_CONFIG[LogDeferredInMcaStat] is set but this may change for
future SMCA implementations.

Thanks,
Yazen