linux-kernel - RE: [PATCH] ACPI: APEI: move edac_init ahead of ghes platform drv register

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Date:   Mon, 8 Aug 2022 20:40:18 +0000
From:   "Kani, Toshi" <toshi.kani@....com>
To:     Borislav Petkov <bp@...en8.de>,
        "Rafael J. Wysocki" <rafael@...nel.org>
CC:     Jia He <justin.he@....com>, Len Brown <lenb@...nel.org>,
        James Morse <james.morse@....com>,
        Tony Luck <tony.luck@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Robert Richter <rric@...nel.org>,
        Shuai Xue <xueshuai@...ux.alibaba.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        "ACPI Devel Maling List" <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:EDAC-CORE" <linux-edac@...r.kernel.org>
Subject: RE: [PATCH] ACPI: APEI: move edac_init ahead of ghes platform drv
 register

On Monday, August 8, 2022 12:38 PM, Borislav Petkov wrote:
> On Mon, Aug 08, 2022 at 08:17:58PM +0200, Rafael J. Wysocki wrote:
> > This effectively makes EDAC depend on GHES which may not be always
> > valid AFAICS.
> 
> Yes, and this has been getting on my nerves since forever.
> 
> The GHES code which does collect all those errors *forces* the registration of
> an EDAC module which does only the reporting.
> 
> Which cannot be any more backwards.
> 
> What should happen is, GHES inits and starts working on the errors.
> Then, at some point later, ghes_edac loads and starts reporting whatever it
> gets. If there's no EDAC module, it doesn't report them. The same way MCA
> works.
> 
> That's it.
> 
> And then ghes_edac can be made a normal module again and we can get rid
> of this insanity.

The following approach may be considerable:
- Separate ghes_edac_register() into two functions, e.g., ghes_edac_register()
and ghes_edac_init().
- ghes_edac_register() only takes the first if-block with IS_ENABLED() & force_load
check, and then calls a new function, edac_set_owner(mod_name), which simply
sets mod_name to edac_mc_owner.  This allows ghes_edac_register() to run
before edac_init(), and sets edac_mc_owner to prevent chipset-specific edac driver
to be loaded before ghes_edac.
- ghes_edac_init() first calls edac_get_owner() to match with its mod_name.  If so,
it performs the rest of the original ghes_edac_register() procedure.  This
ghes_edac_init() is called from the normal module init path, e.g., module_init().

Thanks,
Toshi