Hi Dmitry,
> Subject: Re: [PATCH v5 2/3] drm/virtio: Add support for saving and restoring
> virtio_gpu_objects
>
> On 10/3/25 20:01, Kim, Dongwon wrote:
> > Hi Dmitry,
> >
> >> Subject: Re: [PATCH v5 2/3] drm/virtio: Add support for saving and
> >> restoring virtio_gpu_objects
> >>
> >> On 10/3/25 08:34, dongwon....@intel.com wrote:
> >>> +int virtio_gpu_object_restore_all(struct virtio_gpu_device *vgdev) {
> >>> + struct virtio_gpu_object *bo, *tmp;
> >>> + struct virtio_gpu_mem_entry *ents;
> >>> + unsigned int nents;
> >>> + int ret = 0;
> >>> +
> >>> + spin_lock(&vgdev->obj_restore_lock);
> >>> + list_for_each_entry_safe(bo, tmp, &vgdev->obj_restore_list, list) {
> >>> + ret = virtio_gpu_object_shmem_init(vgdev, bo, &ents, &nents);
> >>> + if (ret)
> >>> + break;
> >>> +
> >>> + if (bo->params.blob) {
> >>> + virtio_gpu_cmd_resource_create_blob(vgdev, bo, &bo-
> >>> params,
> >>> + ents, nents);
> >>> + } else if (bo->params.virgl) {
> >>> + virtio_gpu_cmd_resource_create_3d(vgdev, bo, &bo-
> >>> params,
> >>> + NULL, NULL);
> >>> +
> >>> + if (bo->attached) {
> >>> + bo->attached = false;
> >>> + virtio_gpu_object_attach(vgdev, bo, ents,
> >> nents);
> >>> + }
> >>> + } else {
> >>
> >> No need to restore blob and 3d resources that we don't support
> >> restore of and that won't be in the obj_restore_list since only shmem
> >> objs are added to the list.
> >>
> >
> > We are very interested in restoration of blob as well. It is actually
> > the primary type of resource we want to recover because those are used
> > as guest frame buffer we render in QEMU. Can you tell me why it
> > should be excluded? Would it be because of ambiguity of the location of
> backing pages for it (e.g. VRAM)?
> >
> > And 3D is not our primary interest so I don't have any issue excluding
> > it but it would be great if you can explain the reason for it as well.
> >
> > Thanks!
>
> Good point, only host blobs should be excluded. We can't restore VRAM on
> resume as hostmem is lost on host side after entering S4.
>
> Actually, now I don't see where imported dmabuf guest blob added to the
> restore_list in virtgpu_dma_buf_init_obj(). Please make sure restoring guest
> blobs tested properly.
Right, you got some critical point there.. I forgot about this object with
imported dmabuf.
We will have to store the case virtio_gpu_objects backed by imported dmabuf as
well
in case the backing storage is still valid. By the way, so far we are not using
imported
buffer as a guest framebuffer. All scanouts are originated from virtio_gpu
itself, which would
be the reason it has worked so far.
Anyhow, no matter whether it's imported or created by virtio-gpu driver, I
guess storing
only blobs with bo->attached=true would be enough assuming host blob doesn't
have any
backing pages. What do you think?
(I will also modify the code to store objects backed by imported dmabuf.)
>
> --
> Best regards,
> Dmitry
