Re: [PATCH v1] Revert "drm/virtio: Allow importing prime buffers when 3D is enabled"

[Val Packett <val@invisiblethingslab.com>]

On 9/11/26 11:42 AM, Dmitry Osipenko wrote:
> Guest userspace may import udmabuf to vrend. Vrend doesn't support guest
> blobs, and thus, further 3d operations with the imported blob are failing.
> Typical scenario of the problem shown with mouse cursor RGBA image imported
> into virtio-gpu, which previously was rejected by virtio-gpu driver.
> Revert enabling guest blobs importing into vrend to fix the regression.
>
> Link: https://gitlab.freedesktop.org/virgl/virglrenderer/-/work_items/674
> Fixes: df4dc947c46b ("drm/virtio: Allow importing prime buffers when 3D is enabled")
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>   drivers/gpu/drm/virtio/virtgpu_prime.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_prime.c b/drivers/gpu/drm/virtio/virtgpu_prime.c
> index 149e6bcb5878..ebf471044d06 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_prime.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_prime.c
> @@ -349,7 +349,7 @@ struct drm_gem_object *virtgpu_gem_prime_import(struct drm_device *dev,
>   		}
>   	}
>   
> -	if (!vgdev->has_resource_blob)
> +	if (!vgdev->has_resource_blob || vgdev->has_virgl_3d)
>   		return drm_gem_prime_import(dev, buf);
>   
>   	bo = kzalloc_obj(*bo);

Oops, right, didn't think the back-compat issues all the way through on 
that one..

Reviewed-by: Val Packett <val@invisiblethingslab.com>


BTW, to clarify wrt the original use case this was intended for— I got 
it all working, but it adds new feature flags:

https://lore.kernel.org/virtio-comment/20260903021442.423274-1-val@invisiblethingslab.com/

So I'll "unlock" this again in new patches but not unconditionally of 
course. Rather, gated on the new F_CREATE_GUEST_HANDLE flag which would 
indicate that the device backend *does* support creating guest blobs 
with host handles (dmabufs).


Thanks,
~val