linux-kernel - Re: Dell XPS13: MCE (Hardware Error) reported

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Date:   Mon, 9 Jan 2017 11:23:36 -0800
From:   "Raj, Ashok" <ashok.raj@...el.com>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
Cc:     Borislav Petkov <bp@...en8.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thorsten Leemhuis <linux@...mhuis.info>,
        Len Brown <len.brown@...el.com>,
        Tony Luck <tony.luck@...el.com>, ashok.raj@...el.com
Subject: Re: Dell XPS13: MCE (Hardware Error) reported

Hi Paul

On Mon, Jan 09, 2017 at 12:53:33PM +0100, Paul Menzel wrote:
> 
> 
> On 01/05/17 02:12, Raj, Ashok wrote:
> 
> >>>CPUID Vendor Intel Family 6 Model 142
> >This is Kabylake Mobile
> >
> >>>Hardware event. This is not a software error.
> >>>MCE 1
> >>>CPU 0 BANK 7
> >>>MISC 7880018086 ADDR fef1ce40
> >>>TIME 1483543069 Wed Jan  4 16:17:49 2017

> >>>STATUS ee0000000040110a MCGSTATUS 0
> >
> >Decoding the bits further from MCi_STATUS above:
> >Val=1, OVER=1, UC=1, but EN=0 indicates this isn't a MCE, hence should have
> >been signaled by a CMCI.
> >
> >PCC=1, but should be ignored when EN=0.
> >MCACOD: 110a MSCOD: 0040

This MSCOD indicates that its a write back access to mmio space. Its possible
that BIOS is scanning certain memory region during boot. During which time
BIOS does disable generation of MCE's. Which is why EN=0 in the above log.

Its a BIOS bug, one would expect that BIOS clears up these before handoff to
OS. During OS boot we also scan all MC banks and log/clear them.

If you aren't observing them during normal operation you can safely ignore
these preboot logs, or pass them along to your OEM.

Cheers,
Ashok