On 2023/09/13 20:34, Albert Esteve wrote:
On Wed, Sep 13, 2023 at 12:34 PM Akihiko Odaki <akihiko.od...@daynix.com
<mailto:akihiko.od...@daynix.com>> wrote:
On 2023/09/13 16:55, Albert Esteve wrote:
> Hi Antonio,
>
> If I'm not mistaken, this patch is related with:
>
https://lists.gnu.org/archive/html/qemu-devel/2023-09/msg01853.html
<https://lists.gnu.org/archive/html/qemu-devel/2023-09/msg01853.html>
>
<https://lists.gnu.org/archive/html/qemu-devel/2023-09/msg01853.html
<https://lists.gnu.org/archive/html/qemu-devel/2023-09/msg01853.html>>
> IMHO, ideally, virtio-gpu and vhost-user-gpu both, would use the
> infrastructure from the patch I linked to store the
> virtio objects, so that they can be later shared with other devices.
I don't think such sharing is possible because the resources are
identified by IDs that are local to the device. That also complicates
migration.
Regards,
Akihiko Odaki
Hi Akihiko,
As far as I understand, the feature to export dma-bufs from the
virtgpu was introduced as part of the virtio cross-device sharing
proposal [1]. Thus, it shall be posible. When virtgpu ASSING_UUID,
it exports and identifies the dmabuf resource, so that when the dmabuf gets
shared inside the guest (e.g., with virtio-video), we can use the assigned
UUID to find the dmabuf in the host (using the patch that I linked above),
and import it.
[1] - https://lwn.net/Articles/828988/ <https://lwn.net/Articles/828988/>
The problem is that virtio-gpu can have other kind of resources like
pixman and OpenGL textures and manage them and DMA-BUFs with unified
resource ID.
So you cannot change:
g_hash_table_insert(g->resource_uuids,
GUINT_TO_POINTER(assign.resource_id), uuid);
by:
virtio_add_dmabuf(uuid, assign.resource_id);
assign.resource_id is not DMA-BUF file descriptor, and the underlying
resource my not be DMA-BUF at first place.
Also, since this lives in the common code that is not used only by
virtio-gpu-gl but also virtio-gpu, which supports migration, we also
need to take care of that. It is not a problem for DMA-BUF as DMA-BUF is
not migratable anyway, but the situation is different in this case.
Implementing cross-device sharing is certainly a possibility, but that
requires more than dealing with DMA-BUFs.
