linux-kernel - Re: [PATCH v5 1/1] drm/doc: Document DRM device reset expectations

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Date:   Tue, 27 Jun 2023 18:17:35 -0300
From:   André Almeida <andrealmeid@...lia.com>
To:     Christian König <ckoenig.leichtzumerken@...il.com>
Cc:     pierre-eric.pelloux-prayer@....com,
        Randy Dunlap <rdunlap@...radead.org>,
        Daniel Vetter <daniel@...ll.ch>,
        'Marek Olšák' <maraeo@...il.com>,
        Michel Dänzer <michel.daenzer@...lbox.org>,
        Simon Ser <contact@...rsion.fr>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Timur Kristóf <timur.kristof@...il.com>,
        amd-gfx@...ts.freedesktop.org,
        Pekka Paalanen <ppaalanen@...il.com>,
        Daniel Stone <daniel@...ishbar.org>,
        Rob Clark <robdclark@...il.com>,
        Samuel Pitoiset <samuel.pitoiset@...il.com>,
        kernel-dev@...lia.com, Bas Nieuwenhuizen <bas@...nieuwenhuizen.nl>,
        alexander.deucher@....com,
        Pekka Paalanen <pekka.paalanen@...labora.com>,
        Dave Airlie <airlied@...il.com>, christian.koenig@....com
Subject: Re: [PATCH v5 1/1] drm/doc: Document DRM device reset expectations

Em 27/06/2023 14:47, Christian König escreveu:
> Am 27.06.23 um 15:23 schrieb André Almeida:
>> Create a section that specifies how to deal with DRM device resets for
>> kernel and userspace drivers.
>>
>> Acked-by: Pekka Paalanen <pekka.paalanen@...labora.com>
>> Signed-off-by: André Almeida <andrealmeid@...lia.com>
>> ---
>>
>> v4: 
>> https://lore.kernel.org/lkml/20230626183347.55118-1-andrealmeid@igalia.com/
>>
>> Changes:
>>   - Grammar fixes (Randy)
>>
>>   Documentation/gpu/drm-uapi.rst | 68 ++++++++++++++++++++++++++++++++++
>>   1 file changed, 68 insertions(+)
>>
>> diff --git a/Documentation/gpu/drm-uapi.rst 
>> b/Documentation/gpu/drm-uapi.rst
>> index 65fb3036a580..3cbffa25ed93 100644
>> --- a/Documentation/gpu/drm-uapi.rst
>> +++ b/Documentation/gpu/drm-uapi.rst
>> @@ -285,6 +285,74 @@ for GPU1 and GPU2 from different vendors, and a 
>> third handler for
>>   mmapped regular files. Threads cause additional pain with signal
>>   handling as well.
>> +Device reset
>> +============
>> +
>> +The GPU stack is really complex and is prone to errors, from hardware 
>> bugs,
>> +faulty applications and everything in between the many layers. Some 
>> errors
>> +require resetting the device in order to make the device usable 
>> again. This
>> +sections describes the expectations for DRM and usermode drivers when a
>> +device resets and how to propagate the reset status.
>> +
>> +Kernel Mode Driver
>> +------------------
>> +
>> +The KMD is responsible for checking if the device needs a reset, and 
>> to perform
>> +it as needed. Usually a hang is detected when a job gets stuck 
>> executing. KMD
>> +should keep track of resets, because userspace can query any time 
>> about the
>> +reset stats for an specific context.
> 
> Maybe drop the part "for a specific context". Essentially the reset 
> query could use global counters instead and we won't need the context 
> any more here.
> 

Right, I wrote like this to reflect how it's currently implemented.

If follow correctly what you meant, KMD could always notify the global 
count for UMD, and we would move to the UMD the responsibility to manage 
the reset counters, right? This would also simplify my 
DRM_IOCTL_GET_RESET proposal. I'll apply your suggestion to the next doc 
version.

> Apart from that this sounds good to me, feel free to add my rb.
> 
> Regards,
> Christian.
> 
>