Re: [PATCH 1/5] drm/virtio: add virtio_gpu_alloc_fence()

[Robert Foss]

Hey Emil,

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:
> > From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
> >
> > Refactor fence creation to remove the potential allocation failure from
> > the cmd_submit and atomic_commit paths. Now the fence should be allocated
> > first and just after we should proceed with the rest of the execution.
>
> Commit does a bit more that what the above says:
>   - dummy, factor out fence creation/destruction
>   - use per virtio_gpu_framebuffer fence
>
> Personally I'd keep the two separate patches and elaborate on the latter.
> Obviously in that case, one will need to add 3 lines worth of
> virtio_gpu_fence_alloc() in virtio_gpu_cursor_plane_update which will be nuked
> with the next patch.
>
> Not a big deal, but it's up-to the maintainer to make the final call if it's
> worth splitting or not.

Agreed, I'll hold off with this change until then.

> Couple of minor nitpicks below.
>
> >          struct virtio_gpu_device *vgdev = dev->dev_private;
> >          struct virtio_gpu_output *output = NULL;
> >          struct virtio_gpu_framebuffer *vgfb;
> > -       struct virtio_gpu_fence *fence = NULL;
> >          struct virtio_gpu_object *bo = NULL;
> >          uint32_t handle;
> >          int ret = 0;
>
> Add the virtio_gpu_fence_alloc()? And yes it will be nuked with patch 2/...
>
>
>
> > +struct virtio_gpu_fence *virtio_gpu_fence_alloc(struct virtio_gpu_device *vgdev)
> > +{
> > +       struct virtio_gpu_fence_driver *drv = &vgdev->fence_drv;
> > +       struct virtio_gpu_fence *fence = kzalloc(sizeof(struct virtio_gpu_fence), GFP_ATOMIC);
> > +       if (!fence)
> > +               return fence;
> > +
> > +       fence->drv = drv;
> > +       dma_fence_init(&fence->f, &virtio_fence_ops, &drv->lock, drv->context, 0);
> Oh no, lines over 80 col... while the original code is pretty and neat.

Ack

> > +
> > +       return fence;
> > +}
> > +
> > +void virtio_gpu_fence_cleanup(struct virtio_gpu_fence *fence)
> > +{
> > +       if (!fence)
> > +               return;
> > +
> > +       if (fence->drv)
> > +               dma_fence_put(&fence->f);
> > +       else
> > +               kfree(fence);
> I'm not sure if/how we reach the else case here?

That case should never be hit, and if it is that's a bug.
Fixed in v4.

> > +}
> > +
> >   int virtio_gpu_fence_emit(struct virtio_gpu_device *vgdev,
> >                            struct virtio_gpu_ctrl_hdr *cmd_hdr,
> > -                         struct virtio_gpu_fence **fence)
> > +                         struct virtio_gpu_fence *fence)
> >   {
>
> With a follow-up commit, we can drop the no longer needed return type.
> Which it turns out was never checked ...

Fixed during drm-misc-next rebase for v4.

> > @@ -319,6 +332,8 @@ static int virtio_gpu_resource_create_ioctl(struct drm_device *dev, void *data,
> >                  dma_fence_put(&fence->f);
> >          }
> >          return 0;
> > +fail_fence:
>
> The error labels seems to be called after what they do, not what
> fails. fail_backoff seems better IMHO.

Agreed. Fixed in v4.

> > +ttm_eu_backoff_reservation(&ticket, &validate_list);
> Indentation seems off (or my client ate it)?

No, the indentation is bad here. Fixed in v4.

Thanks for the feedback Emil.