linux-kernel - Re: [PATCH AUTOSEL 5.10 13/22] drm/amdgpu: install stub fence into potential unused fence pointers

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Message-ID: <0eb8750d-79c5-4508-ac36-7f91bc8cbaf9@gmail.com>
Date:   Mon, 9 Oct 2023 14:46:40 +0200
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Bryan Jennings <bryjen423@...il.com>
Cc:     sashal@...nel.org, airlied@...ux.ie, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, olvaffe@...il.com,
        amd-gfx@...ts.freedesktop.org, alexander.deucher@....com,
        stable@...r.kernel.org, Lang.Yu@....com, christian.koenig@....com
Subject: Re: [PATCH AUTOSEL 5.10 13/22] drm/amdgpu: install stub fence into
 potential unused fence pointers

Am 07.10.23 um 11:50 schrieb Greg KH:
> On Sun, Sep 10, 2023 at 03:43:01PM -0500, Bryan Jennings wrote:
>> This is also causing log spam on 5.15.  It was included in 5.15.128 as
>> commit 4921792e04f2125b5eadef9dbe9417a8354c7eff.  I encountered this and
>> found https://gitlab.freedesktop.org/drm/amd/-/issues/2820 while researching
>> the problem.
> Confused, what should we do here?

If this patch was backported to even more older kernels then please 
revert that immediately!

This patch was part of a new feature and can only work correctly with a 
bunch of prerequisites. If you don't have those prerequisites in your 
branch then it might actually cause random memory corruptions through 
device DMA.

And we should probably talk about why this patch was automatically 
selected for backporting in the first place? There is no mention that 
this is a fix or should be backported in the commit message or patch 
itself whatsoever.

Without the WARN_ON() which started to spam the logs that could have 
gone south pretty quickly. Random data corruption without any indicator 
what's causing it is not really funny.

Regards,
Christian.