linux-kernel - Re: [PATCH 3/3] ghes_edac: add platform check to enable ghes

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Message-ID: <20170724151013.513d5fc8@vento.lan>
Date:   Mon, 24 Jul 2017 15:10:13 -0300
From:   Mauro Carvalho Chehab <mchehab@...pensource.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "Kani, Toshimitsu" <toshi.kani@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "srinivas.pandruvada@...ux.intel.com" 
        <srinivas.pandruvada@...ux.intel.com>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "lenb@...nel.org" <lenb@...nel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>
Subject: Re: [PATCH 3/3] ghes_edac: add platform check to enable ghes_edac

Em Mon, 24 Jul 2017 18:44:00 +0200
Borislav Petkov <bp@...en8.de> escreveu:

> On Mon, Jul 24, 2017 at 01:04:13PM -0300, Mauro Carvalho Chehab wrote:
> > If the Kernel force those users to use ghes_edac by default,
> > they they won't see the error counts anymore, but, instead,
> > hardware reports that the memories need to be replaced.  
> 
> This is exactly why I'm trying to load ghes_edac only on those platforms
> which would really want it.
> 
> > So, the right solution would be to keep hardware first, but
> > providing a modprobe parameter to let them switch to software
> > first.  
> 
> That's exactly the issue: if we make it spec-conform and adhere to FF
> setting, then it'll be clean. BUT(!), we will force ghes_edac on those
> platforms which potentially are using the platform-specific drivers
> until now. Not good.
> 
> If we do the whitelisting, then we're stuck with maintaining a yucky
> whitelist and have to keep updating ghes_edac with it.

Yeah, having a whitelist is a maintainership's burden, but, on
the other hand, I suspect that there aren't many systems that
implement FF, have a reliable BIOS mapping of MB's silkscreen
and doesn't filters out corrected errors using some sort of
undocumented mechanism.

So, I guess it is doable.

Another alternative, with, IMO, is better would be to add a parameter like:

	edac=FF - firmware first;
	edac=hw	 - hardware first;
	edac=auto - honors FF if set in BIOS. Otherwise, hardware first.

In order to avoid regressions, and to avoid the need of a whitelist,
I would keep "edac=hw" as default.

Thanks,
Mauro