Re: [RFC PATCH v2 1/2] virtio-gpu: add resource create blob

[Gurchetan Singh <gurchetansingh@chromium.org>]

On Mon, May 18, 2020 at 12:41 AM Gerd Hoffmann <kraxel@redhat.com> wrote:
>
> > > > > same goes for dma-buf imports (inside the guest).
> > > >
> > > > dma-buf import from another virtio driver is very interesting, but
> > > > we'll probably need a some import UUID hypercall for that?
> > >
> > > No, just dma-buf import from somewhere, say a gpu passed to the guest
> > > via pci pass-through does the rendering to a dma-buf and that dmabuf
> > > gets imported into virtio-gpu for display in a host window.
> >
> > I'm unfamiliar with that use case ... is there a chance the dma-buf is
> > compressed/tiled?
>
> Hmm, not fully sure but probably not.  I'd expect gpu drivers would
> untile the BO when exporting to another driver because tiling modes
> are typically hard-ware specific ...

Okay, kept the modifier out of SCANOUT_BLOB in v4 as we expect it will
not be used for the pass through case.

>
> > If so, we won't be able to query virglrenderer for the modifier and
> > may need it in SCANOUT_BLOB unless there's another way to get it
> > host-side.
>
> No, there is no other magic way.  Userspace has to tell virtio-gpu what
> format the dma-buf data has if it wants virtio-gpu do something with it,
> the dma-buf itself is just a blob.
>
> take care,
>   Gerd
>