Hi,
On 12/10/25 18:39, Val Packett wrote:
> This functionality was added for using a KMS-only virtgpu with a physical
> (or SR-IOV) headless GPU in passthrough, but it should not be restricted
> to KMS-only mode. It can be used with cross-domain to pass guest memfds
> to the host compositor with zero copies (using udmabuf on both sides).
>
> Drop the check for the absence of virgl_3d to allow for more use cases.
>
> Fixes: ca77f27a2665 ("drm/virtio: Import prime buffers from other devices as
> guest blobs")
> Signed-off-by: Val Packett <[email protected]>
> ---
>
> Hi. I couldn't find any comments on that line in the reviews (on patchwork),
> so I assume
> there was never a specific technical reason for that check, just an abundance
> of caution?
>
> BTW, while here.. The drm_gem_prime_import "fallback" seems pretty much
> equivalent to
> `return (-ENODEV)`, as drm_gem_prime_import(_dev) just translates the call to
> gem_prime_import_sg_table which we don't use. Should it be replaced with
> `return (-ENODEV)`?
Returning -ENODEV should break dmabuf self-importing where virtio-gpu
driver export dmabuf and then imports to itself.
> ---
> 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 ce49282198cb..2fedd5d3bd62 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_prime.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_prime.c
> @@ -312,7 +312,7 @@ struct drm_gem_object *virtgpu_gem_prime_import(struct
> drm_device *dev,
> }
> }
>
> - if (!vgdev->has_resource_blob || vgdev->has_virgl_3d)
> + if (!vgdev->has_resource_blob)
> return drm_gem_prime_import(dev, buf);
>
> bo = kzalloc(sizeof(*bo), GFP_KERNEL);
At a quick glance the change looks fine. Will take another stab after
Holidays and merge if no problems will be spotted. Thanks.
--
Best regards,
Dmitry
