linux-kernel - Re: [PATCH 02/11] x86/nmi, EDAC: Get rid of DRAM error reporting thru PCI SERR NMI

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Date:   Mon, 10 Apr 2017 15:39:55 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Borislav Petkov <bp@...en8.de>
cc:     linux-edac <linux-edac@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH 02/11] x86/nmi, EDAC: Get rid of DRAM error reporting
 thru PCI SERR NMI

On Thu, 6 Apr 2017, Borislav Petkov wrote:
> From: Borislav Petkov <bp@...e.de>
> 
> Apparently, some machines used to report DRAM errors through a PCI SERR
> NMI. This is why we have a call into EDAC in the NMI handler. See
> 
>   c0d121720220 ("drivers/edac: add new nmi rescan").
> 
> >From looking at the patch above, that's two drivers: e752x_edac.c and

Stray '>'

> e7xxx_edac.c. Now, I wanna say those are old machines which are probably
> decommissioned already.
> 
> Tony says that "[t]the newest CPU supported by either of those drivers
> is the Xeon E7520 (a.k.a. "Nehalem") released in Q1'2010. Possibly some
> folks are still using these ... but people that hold onto h/w for 7
> years generally cling to old s/w too ... so I'd guess it unlikely that
> we will get complaints for breaking these in upstream."
> 
> So even if there is a small number still in use, we did load EDAC with
> edac_op_state == EDAC_OPSTATE_POLL by default (we still do, in fact)
> which means a default EDAC setup without any parameters supplied on the
> command line or otherwise would never even log the error in the NMI
> handler because we're polling by default:
> 
>   inline int edac_handler_set(void)
>   {
>          if (edac_op_state == EDAC_OPSTATE_POLL)
>                  return 0;
> 
>          return atomic_read(&edac_handlers);
>   }
> 
> So, long story short, I'd like to get rid of that nastiness called
> edac_stub.c and confine all the EDAC drivers solely to drivers/edac/. If
> we ever have to do stuff like that again, it should be notifiers we're

Notifiers? You mean a proper NMI handler, right?

Other than that: Acked-by: Thomas Gleixner <tglx@...utronix.de>

Thanks,

	tglx