[Intel-gfx] [5.10.y regression] i915 clear-residuals mitigation is causing gfx issues

[Hans de Goede]

Hi,

On 2/10/21 12:07 AM, Chris Wilson wrote:
> Quoting Hans de Goede (2021-02-09 11:46:46)
>> Hi,
>>
>> On 2/9/21 12:27 AM, Chris Wilson wrote:
>>> Quoting Hans de Goede (2021-02-08 20:38:58)
>>>> Hi All,
>>>>
>>>> We (Fedora) have been receiving reports from multiple users about gfx issues / glitches
>>>> stating with 5.10.9. All reporters are users of Ivy Bridge / Haswell iGPUs and all
>>>> reporters report that adding i915.mitigations=off to the cmdline fixes things, see:
>>>
>>> I tried to reproduce this on the w/e on hsw-gt1, to no avail; and piglit
>>> did not report any differences with and without mitigations. I have yet
>>> to test other platforms. So I don't yet have an alternative.
>>
>> Note the original / first reporter of:
>>
>> https://bugzilla.redhat.com/show_bug.cgi?id=1925346
>>
>> Is using hsw-gt2, so it seems that the problem is not just the enabling of
>> the mitigations on ivy-bridge / bay-trail but that there actually is
>> a regression on devices where the WA worked fine before...
> 
> There have been 3 crashes uploaded related to v5.10.9, and in all 3
> cases the ACTHD has been in the first page. This strongly suggests that
> the w/a is scribbling over address 0. And there's then a very good
> chance that
> 
> commit 29d35b73ead4e41aa0d1a954c9bfbdce659ec5d6
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date:   Mon Jan 25 12:50:33 2021 +0000
> 
>     drm/i915/gt: Always try to reserve GGTT address 0x0
>     
>     commit 489140b5ba2e7cc4b853c29e0591895ddb462a82 upstream.
> 
> in v5.10.14 is sufficient to hide the issue.

That one actually is already in v5.10.13 and the various reportes of these
issues have already tested 5.10.13. They did mention that it took longer
to reproduce with 5.10.13 then with 5.10.10, but that could also be due to:

"drm/i915/gt: Clear CACHE_MODE prior to clearing residuals"
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.10.y&id=520d05a77b2866eb4cb9e548e1d8c8abcfe60ec5

Regards,

Hans