linux-kernel - RE: [PATCH v2] apei/ghes: correctly return NULL for ghes_get

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Message-ID: <AM0PR04MB62894F2D0B9BA5512086FB9E8F469@AM0PR04MB6289.eurprd04.prod.outlook.com>
Date:   Thu, 25 May 2023 20:33:07 +0000
From:   Leo Li <leoyang.li@....com>
To:     Justin He <Justin.He@....com>, Toshi Kani <toshi.kani@....com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, James Morse <James.Morse@....com>,
        Tony Luck <tony.luck@...el.com>, Borislav Petkov <bp@...en8.de>
CC:     "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] apei/ghes: correctly return NULL for
 ghes_get_devices()



> -----Original Message-----
> From: Justin He <Justin.He@....com>
> Sent: Thursday, May 25, 2023 10:18 AM
> To: Leo Li <leoyang.li@....com>; Toshi Kani <toshi.kani@....com>; Rafael J.
> Wysocki <rafael@...nel.org>; Len Brown <lenb@...nel.org>; James Morse
> <James.Morse@....com>; Tony Luck <tony.luck@...el.com>; Borislav
> Petkov <bp@...en8.de>
> Cc: linux-acpi@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: RE: [PATCH v2] apei/ghes: correctly return NULL for
> ghes_get_devices()
> 
> Hi Li,
> 
> > -----Original Message-----
> > From: Li Yang <leoyang.li@....com>
> > Sent: Saturday, May 20, 2023 4:13 AM
> > To: Rafael J. Wysocki <rafael@...nel.org>; Len Brown
> > <lenb@...nel.org>; James Morse <James.Morse@....com>; Tony Luck
> > <tony.luck@...el.com>; Borislav Petkov <bp@...en8.de>; Justin He
> > <Justin.He@....com>
> > Cc: Li Yang <leoyang.li@....com>; linux-acpi@...r.kernel.org;
> > linux-kernel@...r.kernel.org
> > Subject: [PATCH v2] apei/ghes: correctly return NULL for
> > ghes_get_devices()
> >
> > Since 315bada690e0 ("EDAC: Check for GHES preference in the
> > chipset-specific EDAC drivers"), vendor specific EDAC driver will not
> > probe correctly when CONFIG_ACPI_APEI_GHES is enabled but no GHES
> > device is present.  Make
> > ghes_get_devices() return NULL when the GHES device list is empty to
> > fix the problem.
> >
> > Fixes: 9057a3f7ac36 ("EDAC/ghes: Prepare to make ghes_edac a proper
> > module")
> > Signed-off-by: Li Yang <leoyang.li@....com>
> > Cc: Jia He <justin.he@....com>
> > ---
> >
> > V2: fix the fallthrough case in x86 path
> >
> >  drivers/acpi/apei/ghes.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c index
> > 34ad071a64e9..4382fe13ee3e 100644
> > --- a/drivers/acpi/apei/ghes.c
> > +++ b/drivers/acpi/apei/ghes.c
> > @@ -1544,6 +1544,8 @@ struct list_head *ghes_get_devices(void)
> >
> >                       pr_warn_once("Force-loading ghes_edac on an
> > unsupported platform. You're on your own!\n");
> >               }
> > +     } else if (list_empty(&ghes_devs)) {
> > +             return NULL;
> >       }
> I have no major objections to the fix. Just curious about the edac driver in
> you platform.
> IIUC, in your case, CONFIG_ACPI_APEI_GHES is enabled and edac_ghes
> driver is either not loaded or fails to load. Is my understanding correct?

Right.  ghes_edac is loaded but since ghes_devs is empty due to this platform not using ACPI, it bails out with -ENODEV very quickly.  I would expect the original platform EDAC driver should continue to work in this scenario.

> I wonder whether ghes_get_devices() can unblock such check condition and
> let other chipset-specific edac drivers continue with the initialization. @Toshi,
> What do u think of it?
> 
> 
> --
> Cheers,
> Justin (Jia He)
> 
> 
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