[PATCH 0/9] drm: Revert general use of struct drm_gem_object.dma_buf

[Christian König]

On 11.07.25 11:35, Thomas Zimmermann wrote:
> Revert the use of drm_gem_object.dma_buf back to .import_attach->dmabuf
> in the affected places. Also revert any fixes on top. Separates references
> to imported and exported DMA bufs within a GEM object; as before.
> 
> Using the dma_buf as the one authoritative field for the DMA buf turns
> out to be fragile. The GEM object's dma_buf pointer can be NULL if
> userspace releases the GEM handle too early. Sima mentioned that the fix
> in commit 5307dce878d4 ("drm/gem: Acquire references on GEM handles for
> framebuffers") is conceptionally broken. Linus still notices boot-up
> hangs that might be related.

Did I missed that response? What exactly is the issue?

> Reverting the whole thing is the only sensible action here.

Feel free to add Acked-by: Christian König <christian.koenig at amd.com> to the entire series.

Regards,
Christian.

> 
> Tested on virtio; and amdgpu, simpledrm plus udl for dma-buf sharing.
> 
> Thomas Zimmermann (9):
>   Revert "drm/framebuffer: Acquire internal references on GEM handles"
>   Revert "drm/gem: Acquire references on GEM handles for framebuffers"
>   Revert "drm/virtio: Use dma_buf from GEM object instance"
>   Revert "drm/vmwgfx: Use dma_buf from GEM object instance"
>   Revert "drm/etnaviv: Use dma_buf from GEM object instance"
>   Revert "drm/prime: Use dma_buf from GEM object instance"
>   Revert "drm/gem-framebuffer: Use dma_buf from GEM object instance"
>   Revert "drm/gem-shmem: Use dma_buf from GEM object instance"
>   Revert "drm/gem-dma: Use dma_buf from GEM object instance"
> 
>  drivers/gpu/drm/drm_framebuffer.c            | 31 +---------
>  drivers/gpu/drm/drm_gem.c                    | 64 +++-----------------
>  drivers/gpu/drm/drm_gem_dma_helper.c         |  2 +-
>  drivers/gpu/drm/drm_gem_framebuffer_helper.c |  8 ++-
>  drivers/gpu/drm/drm_gem_shmem_helper.c       |  4 +-
>  drivers/gpu/drm/drm_internal.h               |  2 -
>  drivers/gpu/drm/drm_prime.c                  |  8 ++-
>  drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c  |  4 +-
>  drivers/gpu/drm/virtio/virtgpu_prime.c       |  5 +-
>  drivers/gpu/drm/vmwgfx/vmwgfx_gem.c          |  6 +-
>  include/drm/drm_framebuffer.h                |  7 ---
>  11 files changed, 35 insertions(+), 106 deletions(-)
>