On 7/8/23 00:31, 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.
>
> In addition, VIRTGPU_EXECBUF_RING_IDX is checked when creating a
> DRM event object. VIRTGPU_CONTEXT_PARAM_POLL_RINGS_MASK is
> already defined in terms of per-context rings. It was theoretically
> possible to create a DRM event on the global timeline (ring_idx == 0),
> if the context enabled DRM event polling. However, that wouldn't
> work and userspace (Sommelier). Explicitly disallow it for
> clarity.
>
> Signed-off-by: Gurchetan Singh <gurchetansi...@chromium.org>
> ---
> v2: Fix indent (Dmitry)
> v3: Refactor drm fence event checks to avoid possible NULL deref (Dmitry)
> v4: More detailed commit message about addition drm fence event checks
> (Dmitry)
>
> drivers/gpu/drm/virtio/virtgpu_submit.c | 28 +++++++++++++------------
> 1 file changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_submit.c
> b/drivers/gpu/drm/virtio/virtgpu_submit.c
> index cf3c04b16a7a..004364cf86d7 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_submit.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_submit.c
> @@ -64,13 +64,9 @@ static int virtio_gpu_fence_event_create(struct drm_device
> *dev,
> struct virtio_gpu_fence *fence,
> u32 ring_idx)
> {
> - struct virtio_gpu_fpriv *vfpriv = file->driver_priv;
> struct virtio_gpu_fence_event *e = NULL;
> int ret;
>
> - if (!(vfpriv->ring_idx_mask & BIT_ULL(ring_idx)))
> - return 0;
> -
> e = kzalloc(sizeof(*e), GFP_KERNEL);
> if (!e)
> return -ENOMEM;
> @@ -161,21 +157,27 @@ static int virtio_gpu_init_submit(struct
> virtio_gpu_submit *submit,
> struct drm_file *file,
> u64 fence_ctx, u32 ring_idx)
> {
> + int err;
> + struct virtio_gpu_fence *out_fence;
> struct virtio_gpu_fpriv *vfpriv = file->driver_priv;
> struct virtio_gpu_device *vgdev = dev->dev_private;
> - struct virtio_gpu_fence *out_fence;
> - int err;
> + bool drm_fence_event = (exbuf->flags & VIRTGPU_EXECBUF_RING_IDX) &&
> + (vfpriv->ring_idx_mask & BIT_ULL(ring_idx));
The common coding style for variables definition in kernel is a "reverse
xmas tree". It makes code easier to read.
*********
******
***
I'll change the style while applying to:
if ((exbuf->flags & VIRTGPU_EXECBUF_RING_IDX) &&
(vfpriv->ring_idx_mask & BIT_ULL(ring_idx)))
drm_fence_event = true;
else
drm_fence_event = false;
> 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) || drm_fence_event ||
> + 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) {
> - dma_fence_put(&out_fence->f);
> - return err;
> + if (drm_fence_event) {
> + err = virtio_gpu_fence_event_create(dev, file, out_fence,
> ring_idx);
> + if (err) {
> + dma_fence_put(&out_fence->f);
> + return err;
> + }
> }
>
> submit->out_fence = out_fence;
Another small note for the future is that you should always start a new
email thread for every new version of the patch, i.e. don't reply with
new version to the old thread. This is not a problem here since it's
just a single patch, nevertheless please take it into account later on.
It eases patch tracking for reviewers.
I tested v4, including the applied CL4605854 to Sommilier. Everything
works well as before. Thank you for addressing all the issues.
Reviewed-by: Dmitry Osipenko <dmitry.osipe...@collabora.com>
Tested-by: Dmitry Osipenko <dmitry.osipe...@collabora.com>
--
Best regards,
Dmitry
