linux-kernel - RE: [PATCH v2 5/7] EDAC/ghes: Prevent chipset-specific edac from loading after ghes

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Message-ID: <DM4PR84MB185306C2C0DE95FF408173BA826C9@DM4PR84MB1853.NAMPRD84.PROD.OUTLOOK.COM>
Date:   Fri, 19 Aug 2022 18:46:34 +0000
From:   "Kani, Toshi" <toshi.kani@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     Justin He <Justin.He@....com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "devel@...ica.org" <devel@...ica.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Shuai Xue <xueshuai@...ux.alibaba.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        nd <nd@....com>, Ard Biesheuvel <ardb@...nel.org>,
        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>,
        Robert Moore <robert.moore@...el.com>,
        Qiuxu Zhuo <qiuxu.zhuo@...el.com>,
        Yazen Ghannam <yazen.ghannam@....com>
Subject: RE: [PATCH v2 5/7] EDAC/ghes: Prevent chipset-specific edac from
 loading after ghes_edac is registered

On Friday, August 19, 2022 12:30 PM, Borislav Petkov wrote:
> > This flag is a static variable, say ghes_present, which is set to
> > false initially. ghes_probe() sets it to true. ghes_edac_preferred()
> > (aka. ghes_get_device) checks this flag at beginning and returns false
> > if this flag is false. It does not get unlatched since ACPI GHES table
> > is static.
> 
> What is that flag needed for at all?

Because ghes_get_device() always returns &ghes_devs on Arm,
which is !NULL.  It does not check if GHES is present.

> There are two possibilities:
> 
> 1. ghes_probe() succeeds. ghes_edac loads properly and other drivers use
> ghes_get_devices() to know when to load.
> 
> 2. ghes_probe() fails and that is caught during platform testing of all
> those platforms who wish to use ghes_edac. BIOS is fixed and goto 1.
> 
> No need for funky flags whatsoever.

3. ghes_probe() is not called, but ghes_get_device() is called from
other edac drivers.

Toshi