[PATCH v3] drm/gem: Internally test import_attach for imported objects

[Thomas Zimmermann]

Hi

Am 05.05.25 um 09:29 schrieb Boris Brezillon:
> On Wed, 30 Apr 2025 11:07:17 +0200
> Simona Vetter <simona.vetter at ffwll.ch> wrote:
>
>> On Wed, Apr 16, 2025 at 11:38:03AM +0200, Simona Vetter wrote:
>>> On Wed, Apr 16, 2025 at 08:57:45AM +0200, Thomas Zimmermann wrote:
>>>> Test struct drm_gem_object.import_attach to detect imported objects.
>>>>
>>>> During object clenanup, the dma_buf field might be NULL. Testing it in
>>>> an object's free callback then incorrectly does a cleanup as for native
>>>> objects. Happens for calls to drm_mode_destroy_dumb_ioctl() that
>>>> clears the dma_buf field in drm_gem_object_exported_dma_buf_free().
>>>>
>>>> v3:
>>>> - only test for import_attach (Boris)
>>>> v2:
>>>> - use import_attach.dmabuf instead of dma_buf (Christian)
>>>>
>>>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>>>> Fixes: b57aa47d39e9 ("drm/gem: Test for imported GEM buffers with helper")
>>>> Reported-by: Andy Yan <andyshrk at 163.com>
>>>> Closes: https://lore.kernel.org/dri-devel/38d09d34.4354.196379aa560.Coremail.andyshrk@163.com/
>>>> Tested-by: Andy Yan <andyshrk at 163.com>
>>>> Cc: Thomas Zimmermann <tzimmermann at suse.de>
>>>> Cc: Anusha Srivatsa <asrivats at redhat.com>
>>>> Cc: Christian König <christian.koenig at amd.com>
>>>> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
>>>> Cc: Maxime Ripard <mripard at kernel.org>
>>>> Cc: David Airlie <airlied at gmail.com>
>>>> Cc: Simona Vetter <simona at ffwll.ch>
>>>> Cc: Sumit Semwal <sumit.semwal at linaro.org>
>>>> Cc: "Christian König" <christian.koenig at amd.com>
>>>> Cc: dri-devel at lists.freedesktop.org
>>>> Cc: linux-media at vger.kernel.org
>>>> Cc: linaro-mm-sig at lists.linaro.org
>>> Reviewed-by: Simona Vetter <simona.vetter at ffwll.ch>
>> Also quick doc request: We do have a bit of overview documentation for
>> prime here about specifically this lifetime fun, and why there's a chain
>> of references and hence a distinction between imported foreign dma-buf and
>> re-imported native dma-buf:
>>
>> https://dri.freedesktop.org/docs/drm/gpu/drm-mm.html#reference-counting-for-gem-drivers
>>
>> I think it would be good to augment this with more links to functions
>> (like this one recently added and fixed in this patch here) and struct
>> members to that overview. And maybe also link from key function and struct
>> functions back to that overview doc. Otherwise I think the next person
>> will get confused by this rather tricky code again and break a corner
>> cases.
> BTW, could we also backmerge 6.15-rc5 into drm-misc-next so the fix is
> also present in drm-misc-next?

drm-misc-next is now at -rc5

Best regards
Thomas


-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
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