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References: <20220405173918.1000846-1-robdclark@gmail.com>
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From:   Chia-I Wu <olvaffe@gmail.com>
Date:   Tue, 5 Apr 2022 10:56:51 -0700
Message-ID: <CAPaKu7Tur-_Kf3Lb9U=98Yr_08onxPHNKTPh2anHU6zLPhr5ZQ@mail.gmail.com>
Subject: Re: [PATCH] drm/virtio: Add execbuf flag to request no fence-event
To:     Rob Clark <robdclark@gmail.com>
Cc:     ML dri-devel <dri-devel@lists.freedesktop.org>,
        Rob Clark <robdclark@chromium.org>,
        David Airlie <airlied@linux.ie>,
        Gerd Hoffmann <kraxel@redhat.com>,
        Gurchetan Singh <gurchetansingh@chromium.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@lists.linux-foundation.org>,
        open list <linux-kernel@vger.kernel.org>
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On Tue, Apr 5, 2022 at 10:38 AM Rob Clark <robdclark@gmail.com> wrote:
>
> From: Rob Clark <robdclark@chromium.org>
>
> It would have been cleaner to have a flag to *request* the fence event.
> But that ship has sailed.  So add a flag so that userspace which doesn't
> care about the events can opt-out.
>
> Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>

Might want to wait for Gurchetan to chime in as he added the mechanism.

> ---
>  drivers/gpu/drm/virtio/virtgpu_ioctl.c | 8 +++++---
>  include/uapi/drm/virtgpu_drm.h         | 2 ++
>  2 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> index 3a8078f2ee27..09f1aa263f91 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> @@ -225,9 +225,11 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
>                 goto out_unresv;
>         }
>
> -       ret = virtio_gpu_fence_event_create(dev, file, out_fence, ring_idx);
> -       if (ret)
> -               goto out_unresv;
> +       if (!(exbuf->flags & VIRTGPU_EXECBUF_NO_EVENT)) {
> +               ret = virtio_gpu_fence_event_create(dev, file, out_fence, ring_idx);
> +               if (ret)
> +                       goto out_unresv;
> +       }
>
>         if (out_fence_fd >= 0) {
>                 sync_file = sync_file_create(&out_fence->f);
> diff --git a/include/uapi/drm/virtgpu_drm.h b/include/uapi/drm/virtgpu_drm.h
> index 0512fde5e697..d06cac3407cc 100644
> --- a/include/uapi/drm/virtgpu_drm.h
> +++ b/include/uapi/drm/virtgpu_drm.h
> @@ -52,10 +52,12 @@ extern "C" {
>  #define VIRTGPU_EXECBUF_FENCE_FD_IN    0x01
>  #define VIRTGPU_EXECBUF_FENCE_FD_OUT   0x02
>  #define VIRTGPU_EXECBUF_RING_IDX       0x04
> +#define VIRTGPU_EXECBUF_NO_EVENT       0x08
>  #define VIRTGPU_EXECBUF_FLAGS  (\
>                 VIRTGPU_EXECBUF_FENCE_FD_IN |\
>                 VIRTGPU_EXECBUF_FENCE_FD_OUT |\
>                 VIRTGPU_EXECBUF_RING_IDX |\
> +               VIRTGPU_EXECBUF_NO_EVENT |\
>                 0)
>
>  struct drm_virtgpu_map {
> --
> 2.35.1
>