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

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Date:   Tue, 11 Apr 2017 13:50:02 +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 9:36 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 01:32:03PM +0000, Ghannam, Yazen wrote:
> > Yes, exactly. Deferred errors are *always* logged in the DE* registers and
> 
> Then the solution is simple:
> 
>         for_each_bank()
>                 if (log_error()) {
> 			clear_msrs();

We need to make sure log_error() logged the deferred error before clearing
MCA_DESTAT. We shouldn't assume that it did because we're in the #DF handler.
There's still a possibility that it was overwritten even if very rare.

> 			continue;
> 		}
> 
>                 if (mca_cfg.smca) {
>                         log_error_from_de_regs()
> 			clear_msrs();
> 		}
> 	}
> 
> and clear_msrs() clears them all.
> 

Thanks,
Yazen