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From:   "Joshi, Mukul" <Mukul.Joshi@amd.com>
To:     Borislav Petkov <bp@alien8.de>
CC:     "amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
        "Kasiviswanathan, Harish" <Harish.Kasiviswanathan@amd.com>,
        x86-ml <x86@kernel.org>, lkml <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] drm/amdgpu: Register bad page handler for Aldebaran
Thread-Topic: [PATCH] drm/amdgpu: Register bad page handler for Aldebaran
Thread-Index: AQHXRs6Uco2r7eCCPEW3XTp7lQLNb6rflw+AgACR7NCAAC6FAIAAV7jw
Date:   Thu, 13 May 2021 03:20:36 +0000
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[AMD Official Use Only - Internal Distribution Only]


> -----Original Message-----
> From: Borislav Petkov <bp@alien8.de>
> Sent: Wednesday, May 12, 2021 5:06 PM
> To: Joshi, Mukul <Mukul.Joshi@amd.com>
> Cc: amd-gfx@lists.freedesktop.org; Kasiviswanathan, Harish
> <Harish.Kasiviswanathan@amd.com>; x86-ml <x86@kernel.org>; lkml <linux-
> kernel@vger.kernel.org>
> Subject: Re: [PATCH] drm/amdgpu: Register bad page handler for Aldebaran
>=20
> [CAUTION: External Email]
>=20
> On Wed, May 12, 2021 at 07:00:58PM +0000, Joshi, Mukul wrote:
> > SMCA UMCv2 corresponds to GPU's UMC MCA bank and the GPU driver is
> > only interested in errors on GPU UMC.
>=20
> So that thing should be called SMCA_GPU_UMC not SMCA_UMC_V2.
>=20
> > We cannot know this without is_smca_umc_v2.
>=20
> You don't need it - just export smca_get_bank_type() and test the bank ty=
pe at
> the call site.

Exporting smca_get_bank_type() works fine when CONFIG_X86_MCE_AMD is define=
d.
I would need to put #ifdef CONFIG_X86_MCE_AMD in my code to compile the amd=
gpu
driver when CONFIG_X86_MCE_AMD is not defined.
I can avoid all that by using is_smca_umc_v2().
I think it would be cleaner with using is_smca_umc_v2().

>=20
> > Maybe. I hope its not too much of a concern if it stays the way it is.
>=20
> That was just a suggestion anyway - it is not code I maintain so not my c=
all.
>=20
> > I wasn't really sure if I should use the EDAC priority here or create a=
 new one
> for Accelerator devices.
> > I thought using EDAC priority might not be accepted by the maintainers
> > as EDAC and GPU (Accelerator) devices are two different class of device=
s.
> > That is the reason I create a new one.
> > I am OK to use EDAC priority if that is acceptable.
>=20
> I don't know what's acceptable because I still am unclear as to what that=
 thing is
> supposed to do. It seems you are interested only in uncorrectable errors.
>=20

You can think of GPU device as a EDAC device here. It is mainly interested =
in
handling uncorrectable errors.

> How are those errors reported? #MC exception, deferred interrupt, simply
> logged in the bank and we find them by polling?
>=20

It is a deferred interrupt that generates an MCE.

> Then, the commit message is talking about some "bad page retirement".
> What does that do? What can the user do when she sees the
>=20
> "Uncorrectable error detected in UMC..."
>=20
> message?
>=20
> It depends on what "retiring" of GPU pages means...
>=20
> In any case, dmesg should issue a human-understandable message about the
> recovery action being done and what that means for the user: should she
> replace the GPU, should she ignore, etc, etc.
>

When an uncorrectable error is detected on the GPU UMC, all we are doing is=
=20
determining the physical address where the error occurred and then "retirin=
g"
the page that address belongs to.
By retiring, we mean we reserve the page so that it is not available for al=
locations
to any applications.
We are providing information to the user by storing all the information abo=
ut the
retired pages in EEPROM. This can be accessed through sysfs.

Hope it clears what "bad page retirement" is achieving.

Thanks,
Mukul

> > A system can have multiple GPUs and we only want a single notifier
> > registered. I will change the comment to explicitly state this.
>=20
> Actually, the notifier registration should be able to return a different =
retval to
> state that a callback has already been registered but that warns only cur=
rently so
> I'm guessing we're stuck with such ugly "workarounds" for their shortcomi=
ngs.
>=20
> I'm gonna take a look whether they can be fixed though so that you don't =
have
> to do this notifier_registered thing.
>=20
> --
> Regards/Gruss,
>     Boris.
>=20
> https://nam11.safelinks.protection.outlook.com/?url=3Dhttps%3A%2F%2Fpeopl=
e.
> kernel.org%2Ftglx%2Fnotes-about-
> netiquette&amp;data=3D04%7C01%7CMukul.Joshi%40amd.com%7C5e305845504
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