linux-kernel - Re: [PATCH v8 02/18] drm/virtio: switch virtio_gpu_wait

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Date:   Wed, 28 Aug 2019 14:13:44 -0700
From:   Chia-I Wu <olvaffe@...il.com>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     ML dri-devel <dri-devel@...ts.freedesktop.org>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@...ts.linux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 02/18] drm/virtio: switch virtio_gpu_wait_ioctl() to
 gem helper.

On Fri, Aug 23, 2019 at 2:55 AM Gerd Hoffmann <kraxel@...hat.com> wrote:
>
> Use drm_gem_reservation_object_wait() in virtio_gpu_wait_ioctl().
> This also makes the ioctl run lockless.
>
> v5: handle lookup failure.
> v2: use reservation_object_test_signaled_rcu for VIRTGPU_WAIT_NOWAIT.
>
> Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
> Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
> ---
>  drivers/gpu/drm/virtio/virtgpu_ioctl.c | 25 +++++++++++--------------
>  1 file changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> index 0a88ef11b9d3..74b6bad01d7f 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> @@ -466,23 +466,20 @@ static int virtio_gpu_wait_ioctl(struct drm_device *dev, void *data,
>                             struct drm_file *file)
>  {
>         struct drm_virtgpu_3d_wait *args = data;
> -       struct drm_gem_object *gobj = NULL;
> -       struct virtio_gpu_object *qobj = NULL;
> +       struct drm_gem_object *obj;
> +       long timeout = 15 * HZ;
>         int ret;
> -       bool nowait = false;
>
> -       gobj = drm_gem_object_lookup(file, args->handle);
> -       if (gobj == NULL)
> -               return -ENOENT;
> +       if (args->flags & VIRTGPU_WAIT_NOWAIT) {
> +               obj = drm_gem_object_lookup(file, args->handle);
> +               if (obj == NULL)
> +                       return -ENOENT;
> +               ret = dma_resv_test_signaled_rcu(obj->resv, true);
> +               drm_gem_object_put_unlocked(obj);
> +               return ret ? 0 : -EBUSY;
> +       }
>
> -       qobj = gem_to_virtio_gpu_obj(gobj);
> -
> -       if (args->flags & VIRTGPU_WAIT_NOWAIT)
> -               nowait = true;
> -       ret = virtio_gpu_object_wait(qobj, nowait);
> -
> -       drm_gem_object_put_unlocked(gobj);
> -       return ret;
> +       return drm_gem_dma_resv_wait(file, args->handle, true, timeout);
This changes the return value from -EBUSY to -ETIME when the wait
times out.  I think we can use dma_resv_wait_timeout_rcu directly
here.



>  }
>
>  static int virtio_gpu_get_caps_ioctl(struct drm_device *dev,
> --
> 2.18.1
>