[PATCH] drm/virtio: conditionally allocate virtio_gpu_fence

[Gurchetan Singh]

On Mon, Jun 19, 2023 at 3:02 PM Dmitry Osipenko <
dmitry.osipenko at collabora.com> wrote:

> On 6/13/23 20:43, Gurchetan Singh wrote:
> > We don't want to create a fence for every command submission.  It's
> > only necessary when userspace provides a waitable token for submission.
> > This could be:
> >
> > 1) bo_handles, to be used with VIRTGPU_WAIT
> > 2) out_fence_fd, to be used with dma_fence apis
> > 3) a ring_idx provided with VIRTGPU_CONTEXT_PARAM_POLL_RINGS_MASK
> >    + DRM event API
> > 4) syncobjs in the future
> >
> > The use case for just submitting a command to the host, and expecting
> > no response.  For example, gfxstream has GFXSTREAM_CONTEXT_PING that
> > just wakes up the host side worker threads.  There's also
> > CROSS_DOMAIN_CMD_SEND which just sends data to the Wayland server.
> >
> > This prevents the need to signal the automatically created
> > virtio_gpu_fence.
> >
> > Signed-off-by: Gurchetan Singh <gurchetansingh at chromium.org>
> > ---
> >  drivers/gpu/drm/virtio/virtgpu_submit.c | 10 +++++++---
> >  1 file changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/virtio/virtgpu_submit.c
> b/drivers/gpu/drm/virtio/virtgpu_submit.c
> > index cf3c04b16a7a..add106c06ab2 100644
> > --- a/drivers/gpu/drm/virtio/virtgpu_submit.c
> > +++ b/drivers/gpu/drm/virtio/virtgpu_submit.c
> > @@ -168,9 +168,13 @@ static int virtio_gpu_init_submit(struct
> virtio_gpu_submit *submit,
> >
> >       memset(submit, 0, sizeof(*submit));
> >
> > -     out_fence = virtio_gpu_fence_alloc(vgdev, fence_ctx, ring_idx);
> > -     if (!out_fence)
> > -             return -ENOMEM;
> > +     if ((exbuf->flags & VIRTGPU_EXECBUF_FENCE_FD_OUT) ||
> > +             ((exbuf->flags & VIRTGPU_EXECBUF_RING_IDX) &&
> > +             (vfpriv->ring_idx_mask & BIT_ULL(ring_idx))) ||
> > +             exbuf->num_bo_handles)
> > +             out_fence = virtio_gpu_fence_alloc(vgdev, fence_ctx,
> ring_idx);
> > +     else
> > +             out_fence = NULL;
> >
> >       err = virtio_gpu_fence_event_create(dev, file, out_fence,
> ring_idx);
> >       if (err) {
>
> Looks okay, code indentation may be improved a tad to make it more
> eye-friendly:
>
> +       if ((exbuf->flags & VIRTGPU_EXECBUF_FENCE_FD_OUT) ||
> +          ((exbuf->flags & VIRTGPU_EXECBUF_RING_IDX) &&
> (vfpriv->ring_idx_mask & BIT_ULL(ring_idx))) ||
> +            exbuf->num_bo_handles)
> +               out_fence = virtio_gpu_fence_alloc(vgdev, fence_ctx,
> ring_idx);
> +       else
> +               out_fence = NULL;
>
> Checkpatch will complain about this variant, but the complaint can be
> ignored in this case.
>

Added you r-b and fixed indent in v2.


>
> --
> Best regards,
> Dmitry
>
>
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