On Fri, Sep 10, 2021 at 12:33 PM Chia-I Wu <olvaffe@xxxxxxxxx> wrote:
On Wed, Sep 8, 2021 at 6:37 PM Gurchetan Singh
<gurchetansingh@xxxxxxxxxxxx> wrote:
>
> We don't want fences from different 3D contexts (virgl, gfxstream,
> venus) to be on the same timeline. With explicit context creation,
> we can specify the number of ring each context wants.
>
> Execbuffer can specify which ring to use.
>
> Signed-off-by: Gurchetan Singh <gurchetansingh@xxxxxxxxxxxx>
> Acked-by: Lingfeng Yang <lfy@xxxxxxxxxx>
> ---
> drivers/gpu/drm/virtio/virtgpu_drv.h | 3 +++
> drivers/gpu/drm/virtio/virtgpu_ioctl.c | 34 ++++++++++++++++++++++++--
> 2 files changed, 35 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
> index a5142d60c2fa..cca9ab505deb 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
> @@ -56,6 +56,7 @@
> #define STATE_ERR 2
>
> #define MAX_CAPSET_ID 63
> +#define MAX_RINGS 64
>
> struct virtio_gpu_object_params {
> unsigned long size;
> @@ -263,6 +264,8 @@ struct virtio_gpu_fpriv {
> uint32_t ctx_id;
> uint32_t context_init;
> bool context_created;
> + uint32_t num_rings;
> + uint64_t base_fence_ctx;
> struct mutex context_lock;
> };
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> index f51f3393a194..262f79210283 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> @@ -99,6 +99,11 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
> int in_fence_fd = exbuf->fence_fd;
> int out_fence_fd = -1;
> void *buf;
> + uint64_t fence_ctx;
> + uint32_t ring_idx;
> +
> + fence_ctx = vgdev->fence_drv.context;
> + ring_idx = 0;
>
> if (vgdev->has_virgl_3d == false)
> return -ENOSYS;
> @@ -106,6 +111,17 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
> if ((exbuf->flags & ~VIRTGPU_EXECBUF_FLAGS))
> return -EINVAL;
>
> + if ((exbuf->flags & VIRTGPU_EXECBUF_RING_IDX)) {
> + if (exbuf->ring_idx >= vfpriv->num_rings)
> + return -EINVAL;
> +
> + if (!vfpriv->base_fence_ctx)
> + return -EINVAL;
> +
> + fence_ctx = vfpriv->base_fence_ctx;
> + ring_idx = exbuf->ring_idx;
> + }
> +
> exbuf->fence_fd = -1;
>
> virtio_gpu_create_context(dev, file);
> @@ -173,7 +189,7 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
> goto out_memdup;
> }
>
> - out_fence = virtio_gpu_fence_alloc(vgdev, vgdev->fence_drv.context, 0);
> + out_fence = virtio_gpu_fence_alloc(vgdev, fence_ctx, ring_idx);
> if(!out_fence) {
> ret = -ENOMEM;
> goto out_unresv;
> @@ -691,7 +707,7 @@ static int virtio_gpu_context_init_ioctl(struct drm_device *dev,
> return -EINVAL;
>
> /* Number of unique parameters supported at this time. */
> - if (num_params > 1)
> + if (num_params > 2)
> return -EINVAL;
>
> ctx_set_params = memdup_user(u64_to_user_ptr(args->ctx_set_params),
> @@ -731,6 +747,20 @@ static int virtio_gpu_context_init_ioctl(struct drm_device *dev,
>
> vfpriv->context_init |= value;
> break;
> + case VIRTGPU_CONTEXT_PARAM_NUM_RINGS:
> + if (vfpriv->base_fence_ctx) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> +
> + if (value > MAX_RINGS) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> +
> + vfpriv->base_fence_ctx = dma_fence_context_alloc(value);
With multiple fence contexts, we should do something about implicit fencing.
The classic example is Mesa and X server. When both use virgl and the
global fence context, no dma_fence_wait is fine. But when Mesa uses
venus and the ring fence context, dma_fence_wait should be inserted.
If I read your comment correctly, the use case is:
context A (venus)
sharing a render target with
context B (Xserver backed virgl)
?
Which function do you envisage dma_fence_wait(...) to be inserted? Doesn't implicit synchronization mean there's no fence to share between contexts (only buffer objects)?
It may be possible to wait on the reservation object associated with a buffer object from a different context (userspace can also do DRM_IOCTL_VIRTGPU_WAIT), but not sure if that's what you're looking for.
> + vfpriv->num_rings = value;
> + break;
> default:
> ret = -EINVAL;
> goto out_unlock;
> --
> 2.33.0.153.gba50c8fa24-goog
>
>
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