[PATCH v2] drm/virtio: conditionally allocate virtio_gpu_fence

[Dmitry Osipenko]

On 7/5/23 18:54, Gurchetan Singh wrote:
> On Wed, Jun 28, 2023 at 8:58 AM Gurchetan Singh
> <gurchetansingh at chromium.org> 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 expected
>> 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>
>> Reviewed-by: <dmitry.osipenko at collabora.com>
>> ---
>>  v2: Fix indent (Dmitry)
>>
>>  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..8c7e15c31164 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) {
>> --
> 
> Ping for additional reviews or merge.

I tested this patch with virgl,venus and nctx. No problems spotted.
Going to apply it tomorrow if there won't be additional comments from
anyone.

Tested-by: Dmitry Osipenko <dmitry.osipenko at collabora.com>

-- 
Best regards,
Dmitry