[RFC PATCH 10/12] drm/virtio: implement context init: handle VIRTGPU_CONTEXT_PARAM_POLL_RINGS_MASK

[Gurchetan Singh]

For the Sommelier guest Wayland proxy, it's desirable for the
DRM fd to be pollable in response to an host compositor event.
This can also be used by the 3D driver to poll events on a CPU
timeline.

This enables the DRM fd associated with a particular 3D context
to be polled independent of KMS events.  The parameter
VIRTGPU_CONTEXT_PARAM_POLL_RINGS_MASK specifies the pollable
rings.

Signed-off-by: Gurchetan Singh <gurchetansingh at chromium.org>
Acked-by: Nicholas Verne <nverne at chromium.org>
---
 drivers/gpu/drm/virtio/virtgpu_drv.h   |  1 +
 drivers/gpu/drm/virtio/virtgpu_ioctl.c | 23 +++++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
index 3243d836b9c7..1182d5e5d322 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -266,6 +266,7 @@ struct virtio_gpu_fpriv {
 	bool context_created;
 	uint32_t num_rings;
 	uint64_t base_fence_ctx;
+	uint32_t ring_idx_mask;
 	struct mutex context_lock;
 };
 
diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 262f79210283..8523351b523d 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -693,7 +693,7 @@ static int virtio_gpu_context_init_ioctl(struct drm_device *dev,
 					 void *data, struct drm_file *file)
 {
 	int ret = 0;
-	uint32_t num_params, i, param, value;
+	uint32_t num_params, i, param, value, valid_ring_mask;
 	size_t len;
 	struct drm_virtgpu_context_set_param *ctx_set_params = NULL;
 	struct virtio_gpu_device *vgdev = dev->dev_private;
@@ -707,7 +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 > 2)
+	if (num_params > 3)
 		return -EINVAL;
 
 	ctx_set_params = memdup_user(u64_to_user_ptr(args->ctx_set_params),
@@ -761,12 +761,31 @@ static int virtio_gpu_context_init_ioctl(struct drm_device *dev,
 			vfpriv->base_fence_ctx = dma_fence_context_alloc(value);
 			vfpriv->num_rings = value;
 			break;
+		case VIRTGPU_CONTEXT_PARAM_POLL_RINGS_MASK:
+			if (vfpriv->ring_idx_mask) {
+				ret = -EINVAL;
+				goto out_unlock;
+			}
+
+			vfpriv->ring_idx_mask = value;
+			break;
 		default:
 			ret = -EINVAL;
 			goto out_unlock;
 		}
 	}
 
+	if (vfpriv->ring_idx_mask) {
+		valid_ring_mask = 0;
+		for (i = 0; i < vfpriv->num_rings; i++)
+			valid_ring_mask |= 1 << i;
+
+		if (~valid_ring_mask & vfpriv->ring_idx_mask) {
+			ret = -EINVAL;
+			goto out_unlock;
+		}
+	}
+
 	virtio_gpu_create_context_locked(vgdev, vfpriv);
 	virtio_gpu_notify(vgdev);
 
-- 
2.33.0.259.gc128427fd7-goog