[virglrenderer-devel] coherent memory access for virgl

[Gerd Hoffmann]

On Wed, Oct 17, 2018 at 12:39:28AM -0700, Zach Reizner wrote:
> On Wed, Oct 17, 2018 at 12:19 AM Gerd Hoffmann <kraxel at redhat.com> wrote:
> >
> > Well, for now I'm looking at the virtio protocol level.  resource_info
> > simply doesn't exist there, so that must be tackled first before we can
> > figure the best way to tell userspace.
> Gurchetan and I have been iterating on expanded resource info a bit:
> virtio-gpu protocol:
> https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1208591/5/include/uapi/linux/virtio_gpu.h

I'm more looking into a new create_resource command, which will also
return stride and size information (and while being at it we probably
should add support for planes too):

https://git.kraxel.org/cgit/linux/commit/?h=drm-virtio-ttm&id=7a8cbf98900db1ba01404ec233dd4b50940567d8

Just proxying the info ioctl to the host doesn't fly.  The kms driver
needs to know pretty early how big the object will actually be (after
the host driver possibly added some padding and alignment), so it can
reserve enough address space in the pci bar.

Making that work needs changes in the way the virtio-gpu driver creates
objects.  Busy with that right now, when it works I can continue looking
into the ioctl and virtio protocol changes.

cheers,
  Gerd

PS: are you at linuxcon / kvm forum @ edinburgh?