Re: [PATCH 2/5] drm/virtio: add uapi for in and out explicit fences

[Robert Foss]

Hey Emil,

On 2018-11-02 14:34, Emil Velikov wrote:
> On Thu, 1 Nov 2018 at 12:56, Robert Foss <robert.foss@xxxxxxxxxxxxx> wrote:
> > On 2018-10-31 10:38, Emil Velikov wrote:
> > > Hi Rob,
> > >
> > > On Thu, 25 Oct 2018 at 19:38, Robert Foss <robert.foss@xxxxxxxxxxxxx> wrote:
> > > > Add a new field called fence_fd that will be used by userspace to send
> > > > in-fences to the kernel and receive out-fences created by the kernel.
> > > >
> > > > This uapi enables virtio to take advantage of explicit synchronization of
> > > > dma-bufs.
> > > >
> > > > There are two new flags:
> > > >
> > > > * VIRTGPU_EXECBUF_FENCE_FD_IN to be used when passing an in-fence fd.
> > > > * VIRTGPU_EXECBUF_FENCE_FD_OUT to be used when requesting an out-fence fd
> > > >
> > > > The execbuffer IOCTL is now read-write to allow the userspace to read the
> > > > out-fence.
> > > >
> > > > On error -1 should be returned in the fence_fd field.
> > > >
> > > > Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
> > > > Signed-off-by: Robert Foss <robert.foss@xxxxxxxxxxxxx>
> > > > ---
> > > > Changes since v2:
> > > >    - Since exbuf-flags is a new flag, check that unsupported
> > > >      flags aren't set.
> > > >
> > > >    drivers/gpu/drm/virtio/virtgpu_ioctl.c |  5 +++++
> > > >    include/uapi/drm/virtgpu_drm.h         | 13 ++++++++++---
> > > >    2 files changed, 15 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> > > > index d01a9ed100d1..1af289b28fc4 100644
> > > > --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> > > > +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> > > > @@ -116,9 +116,14 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
> > > >           struct ww_acquire_ctx ticket;
> > > >           void *buf;
> > > >
> > > > +       exbuf->fence_fd = -1;
> > > > +
> > > Move this after the sanity checking.
> >
> > Agreed. Fixed in v4
> >
> > > >           if (vgdev->has_virgl_3d == false)
> > > >                   return -ENOSYS;
> > > >
> > > > +       if ((exbuf->flags & ~VIRTGPU_EXECBUF_FLAGS))
> > > > +               return -EINVAL;
> > > > +
> > > I assume this did this trigger when using old userspace?
> >
> > No, not as far as I'm aware. This check is there to prevent userspace from
> > polluting the bitspace of flag, so that all free bits can be used for new flags.
> >
> > As far as I understand this is pointed out by a drm driver development document
> > written by danvet, which I unfortunately can't seem to find the link for at the
> > moment.
> Yes that is correct. What I was asking is:
>
> Does a kernel with this patch, work with mesa lacking the corresponding updates?
> I'd imagine things work just fine.

Yes it does!

> -Emil
> _______________________________________________
> dri-devel mailing list
> dri-devel@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/dri-devel