linux-kernel - Re: [PATCH 3/3] EDAC, ghes: Make it a proper module

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Date:   Wed, 2 Aug 2017 00:19:29 +0000
From:   "Kani, Toshimitsu" <toshi.kani@....com>
To:     "bp@...en8.de" <bp@...en8.de>
CC:     "mchehab@...radead.org" <mchehab@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>
Subject: Re: [PATCH 3/3] EDAC, ghes: Make it a proper module

On Tue, 2017-08-01 at 11:46 +0200, Borislav Petkov wrote:
> On Mon, Jul 31, 2017 at 08:19:32PM +0000, Kani, Toshimitsu wrote:
> > I'd prefer to add the whitelist check to ghes_edac first.  This
> > makes the existing code to work.  We can then work on refactoring
> > changes like this on top of it without breaking the functionality.
> 
> Yes, but we want only the whitelist - not the FF testing because, as
> we said, BIOS is notoriously buggy so we're going to load ghes_edac
> only on known-good platforms.

This GHES-probe itself is appropriate and should remain.  Since not all
GHES firmware can be trusted, we will add the white-list as an
additional condition to complement this check.

> Which brings the question about the priority.
> 
> And I *think* the easiest would be if the whitelist were in the core
> edac.ko module, perhaps in edac_module.c (even though it doesn't
> really matter, technically).

I agree that adding the white-list into the core edac module is the
easiest when we make the change on top of yours.  Thinking further on
this, though, I now think that keeping the current implementation is
more reasonable with the reasons below.

1. Device-probing-logic should belong to a driver, and should remain
private to a driver.  When we add the white-list, it should be added to
ghes_edac.

2. ghes_edac is an extension to the ghes driver as they both are
specific to ghes.  ghes_edac is merely ghes driver's edac error-
reporting wrapper than an independent edac driver.  It looks OK to let
ghes_edac get registered as part of ghes_probe() and leave it as an
unconventional edac driver.

3. EDAC does not have its managed probe-chain.  All edac drivers are
called from module_init list.  They independently probe the hardware
and get unloaded when not needed.  The core edac is simply a set of
library to them.  I think it's good to keep them independent, and not
to introduce a new central mechanism for a special case like ghes_edac.

Thanks,
-Toshi