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

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Message-ID: <BN6PR1201MB013144D8AD84C24F119BB39CF8000@BN6PR1201MB0131.namprd12.prod.outlook.com>
Date:   Tue, 11 Apr 2017 13:18:50 +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 9:12 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 12:53:56PM +0000, Ghannam, Yazen wrote:
> > If we do as above then we can possibly log the same deferred error twice.
> 
> Why twice?
> 
> 	for_each_bank()
> 		log_error()
> 		|-> clear MSRs after logging
> 

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().

Thanks,
Yazen