linux-kernel - Re: [PATCH v3 19/28] drm/ttm: rework pipelined eviction fence handling

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Message-ID: <b12b952b-1e32-439f-8d96-78e449cbbde7@amd.com>
Date: Wed, 26 Nov 2025 16:48:05 +0100
From: Christian König <christian.koenig@....com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@....com>,
 Huang Rui <ray.huang@....com>, Matthew Auld <matthew.auld@...el.com>,
 Matthew Brost <matthew.brost@...el.com>, Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Sumit Semwal <sumit.semwal@...aro.org>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v3 19/28] drm/ttm: rework pipelined eviction fence
 handling

On 11/26/25 16:39, Maarten Lankhorst wrote:
> Hey,
> 
> Den 2025-11-26 kl. 16:36, skrev Christian König:
>> On 11/26/25 16:34, Maarten Lankhorst wrote:
>>> Hey,
>>>
>>> Den 2025-11-21 kl. 16:12, skrev Christian König:
>>>> On 11/21/25 11:12, Pierre-Eric Pelloux-Prayer wrote:
>>>>> Until now ttm stored a single pipelined eviction fence which means
>>>>> drivers had to use a single entity for these evictions.
>>>>>
>>>>> To lift this requirement, this commit allows up to 8 entities to
>>>>> be used.
>>>>>
>>>>> Ideally a dma_resv object would have been used as a container of
>>>>> the eviction fences, but the locking rules makes it complex.
>>>>> dma_resv all have the same ww_class, which means "Attempting to
>>>>> lock more mutexes after ww_acquire_done." is an error.
>>>>>
>>>>> One alternative considered was to introduced a 2nd ww_class for
>>>>> specific resv to hold a single "transient" lock (= the resv lock
>>>>> would only be held for a short period, without taking any other
>>>>> locks).
>>>>>
>>>>> The other option, is to statically reserve a fence array, and
>>>>> extend the existing code to deal with N fences, instead of 1.
>>>>>
>>>>> The driver is still responsible to reserve the correct number
>>>>> of fence slots.
>>>>>
>>>>> ---
>>>>> v2:
>>>>> - simplified code
>>>>> - dropped n_fences
>>>>> - name changes
>>>>> v3: use ttm_resource_manager_cleanup
>>>>> ---
>>>>>
>>>>> Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@....com>
>>>>
>>>> Reviewed-by: Christian König <christian.koenig@....com>
>>>>
>>>> Going to push separately to drm-misc-next on Monday.
>>>>
>>> Pushing this broke drm-tip, the amd driver fails to build, as it's not using the eviction_fences array.
>>
>> Thanks for the note! But hui? We changed amdgpu to not touch the move fence.
>>
>> Give me a second.commit 13bec21f5f4cdabdf06725e5a8dee0b9b56ff671 (HEAD -> drm-tip, drm-tip/drm-tip, drm-tip/HEAD)
> 
> Author: Christian König <christian.koenig@....com>
> Date:   Wed Nov 26 13:13:03 2025 +0100
> 
>     drm-tip: 2025y-11m-26d-12h-12m-41s UTC integration manifest
> 
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c:2188:34: error: ‘struct ttm_resource_manager’ has no member named ‘move’
>  2188 |                 dma_fence_put(man->move);
>       |                                  ^~
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c:2189:20: error: ‘struct ttm_resource_manager’ has no member named ‘move’
>  2189 |                 man->move = NULL;
>       |                    ^~
> 
> Is what I see.

Ah, crap, I know what's going on.

The patch to remove those lines is queued up to go upstream through amd-staging-drm-next instead of drm-misc-next.

I will push this patch to drm-misc-next and sync up with Alex that it shouldn't go upstream through amd-staging-drm-next.

Going to build test drm-tip the next time.

Thanks,
Christian.


> 
> Kind regards,
> ~Maarten Lankhorst