Re: [PATCH] drm/prime: Unbreak virtgpu dma-buf export

[Dominik Behr]

It also fixes importing virtgpu blobs into real hardware, for instance
amdgpu for DRI_PRIME rendering.


On Fri, Mar 22, 2024 at 2:48 PM Rob Clark <robdclark@xxxxxxxxx> wrote:
>
> From: Rob Clark <robdclark@xxxxxxxxxxxx>
>
> virtgpu "vram" GEM objects do not implement obj->get_sg_table().  But
> they also don't use drm_gem_map_dma_buf().  In fact they may not even
> have guest visible pages.  But it is perfectly fine to export and share
> with other virtual devices.
>
> Reported-by: Dominik Behr <dbehr@xxxxxxxxxxxx>
> Fixes: 207395da5a97 ("drm/prime: reject DMA-BUF attach when get_sg_table is missing")
> Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/drm_prime.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 7352bde299d5..64dd6276e828 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -582,7 +582,12 @@ int drm_gem_map_attach(struct dma_buf *dma_buf,
>  {
>         struct drm_gem_object *obj = dma_buf->priv;
>
> -       if (!obj->funcs->get_sg_table)
> +       /*
> +        * drm_gem_map_dma_buf() requires obj->get_sg_table(), but drivers
> +        * that implement their own ->map_dma_buf() do not.
> +        */
> +       if ((dma_buf->ops->map_dma_buf == drm_gem_map_dma_buf) &&
> +           !obj->funcs->get_sg_table)
>                 return -ENOSYS;
>
>         return drm_gem_pin(obj);
> --
> 2.44.0
>