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

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 2/11/21 11:49 AM, Chris Wilson wrote:
> Quoting Hans de Goede (2021-02-11 10:36:13)
>> Hi,
>>
>> On 2/10/21 1:48 PM, Chris Wilson wrote:
>>> Quoting Hans de Goede (2021-02-10 10:37:19)
>>>> 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@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
>>>
>>> Started looking for scratch page overwrites, and found this little gem:
>>> https://patchwork.freedesktop.org/patch/420436/?series=86947&rev=1
>>>
>>> Looks promising wrt the cause of overwriting random addresses -- and
>>> I hope that is the explanation for the glitches/hangs. I have a hsw gt2
>>> with gnome shell, piglit is happy, but I suspect it is all due to
>>> placement and so will only occur at random.
>>
>> If you can give me a list of commits to cherry-pick then I can prepare
>> a Fedora 5.10.y kernel which those added for the group of Fedora users
>> who are hitting this to test.
> 
> e627d5923cae ("drm/i915/gt: One more flush for Baytrail clear residuals")
> d30bbd62b1bf ("drm/i915/gt: Flush before changing register state")
> 1914911f4aa0 ("drm/i915/gt: Correct surface base address for renderclear")

Thanks, the test-kernel is building now. I will let you know when I have
heard back from the Fedora users (this will likely take 1-2 days).

Regards,

Hans