[PATCH v4 4/5] drm/virtio: Import prime buffers from other devices as guest blobs

[Dmitry Osipenko]

On 11/25/24 10:31, Vivek Kasireddy wrote:
>  struct drm_gem_object *virtgpu_gem_prime_import(struct drm_device *dev,
>  						struct dma_buf *buf)
>  {
> +	struct virtio_gpu_device *vgdev = dev->dev_private;
> +	struct dma_buf_attachment *attach;
> +	struct virtio_gpu_object *bo;
>  	struct drm_gem_object *obj;
> +	int ret;
>  
>  	if (buf->ops == &virtgpu_dmabuf_ops.ops) {
>  		obj = buf->priv;
> @@ -275,7 +304,32 @@ struct drm_gem_object *virtgpu_gem_prime_import(struct drm_device *dev,
>  		}
>  	}
>  
> -	return drm_gem_prime_import(dev, buf);
> +	if (!vgdev->has_resource_blob || vgdev->has_virgl_3d)
> +		return drm_gem_prime_import(dev, buf);
> +
> +	bo = kzalloc(sizeof(*bo), GFP_KERNEL);
> +	if (!bo)
> +		return ERR_PTR(-ENOMEM);
> +
> +	obj = &bo->base.base;
> +	obj->funcs = &virtgpu_gem_dma_buf_funcs;
> +	drm_gem_private_object_init(dev, obj, buf->size);
> +
> +	attach = dma_buf_dynamic_attach(buf, dev->dev,
> +					&virtgpu_dma_buf_attach_ops, obj);
> +	if (IS_ERR(attach)) {
> +		kfree(bo);
> +		return ERR_CAST(attach);
> +	}
> +
> +	obj->import_attach = attach;
> +	get_dma_buf(buf);
> +
> +	ret = virtgpu_dma_buf_init_obj(dev, bo, attach);
> +	if (ret < 0)
> +		return ERR_PTR(ret);

Perhaps for a future improvement. Think we can defer
virtgpu_dma_buf_init_obj() until first use of the object in a case where
exporter supports dynamic attachment. Otherwise, we're pinning object at
the import time, partially defeating the purpose of the dynamic
attachment, AFAICT. I.e. if importer never uses object, then there is no
need to bother the exporter with the pinning.

-- 
Best regards,
Dmitry