virtio-gpu: add & use virtio_gpu_queue_fenced_ctrl_buffer

Add helper function to handle the submission of fenced control requests.
Make sure we initialize the fence while holding the virtqueue lock, so
requests can't be reordered.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

2 files changed, 35 insertions, 7 deletions

diff --git a/drivers/gpu/drm/virtio/virtgpu_fence.c b/drivers/gpu/drm/virtio/virtgpu_fence.c
index 1da632631dac..793ad9f631fd 100644
--- a/drivers/gpu/drm/virtio/virtgpu_fence.c
+++ b/drivers/gpu/drm/virtio/virtgpu_fence.c
@@ -81,7 +81,7 @@ int virtio_gpu_fence_emit(struct virtio_gpu_device *vgdev,
         struct virtio_gpu_fence_driver *drv = &vgdev->fence_drv;
         unsigned long irq_flags;
 
-        *fence = kmalloc(sizeof(struct virtio_gpu_fence), GFP_KERNEL);
+        *fence = kmalloc(sizeof(struct virtio_gpu_fence), GFP_ATOMIC);
         if ((*fence) == NULL)
                 return -ENOMEM;
 
diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
index 5b9bc242890f..ee25e9a4ae03 100644
--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -347,6 +347,38 @@ static int virtio_gpu_queue_ctrl_buffer(struct virtio_gpu_device *vgdev,
         return rc;
 }
 
+static int virtio_gpu_queue_fenced_ctrl_buffer(struct virtio_gpu_device *vgdev,
+                                               struct virtio_gpu_vbuffer *vbuf,
+                                               struct virtio_gpu_ctrl_hdr *hdr,
+                                               struct virtio_gpu_fence **fence)
+{
+        struct virtqueue *vq = vgdev->ctrlq.vq;
+        int rc;
+
+again:
+        spin_lock(&vgdev->ctrlq.qlock);
+
+        /*
+         * Make sure we have enouth space in the virtqueue.  If not
+         * wait here until we have.
+         *
+         * Without that virtio_gpu_queue_ctrl_buffer_nolock might have
+         * to wait for free space, which can result in fence ids being
+         * submitted out-of-order.
+         */
+        if (vq->num_free < 3) {
+                spin_unlock(&vgdev->ctrlq.qlock);
+                wait_event(vgdev->ctrlq.ack_queue, vq->num_free >= 3);
+                goto again;
+        }
+
+        if (fence)
+                virtio_gpu_fence_emit(vgdev, hdr, fence);
+        rc = virtio_gpu_queue_ctrl_buffer_locked(vgdev, vbuf);
+        spin_unlock(&vgdev->ctrlq.qlock);
+        return rc;
+}
+
 static int virtio_gpu_queue_cursor(struct virtio_gpu_device *vgdev,
                                    struct virtio_gpu_vbuffer *vbuf)
 {
@@ -499,9 +531,7 @@ void virtio_gpu_cmd_transfer_to_host_2d(struct virtio_gpu_device *vgdev,
         cmd_p->r.x = x;
         cmd_p->r.y = y;
 
-        if (fence)
-                virtio_gpu_fence_emit(vgdev, &cmd_p->hdr, fence);
-        virtio_gpu_queue_ctrl_buffer(vgdev, vbuf);
+        virtio_gpu_queue_fenced_ctrl_buffer(vgdev, vbuf, &cmd_p->hdr, fence);
 }
 
 static void
@@ -524,9 +554,7 @@ virtio_gpu_cmd_resource_attach_backing(struct virtio_gpu_device *vgdev,
         vbuf->data_buf = ents;
         vbuf->data_size = sizeof(*ents) * nents;
 
-        if (fence)
-                virtio_gpu_fence_emit(vgdev, &cmd_p->hdr, fence);
-        virtio_gpu_queue_ctrl_buffer(vgdev, vbuf);
+        virtio_gpu_queue_fenced_ctrl_buffer(vgdev, vbuf, &cmd_p->hdr, fence);
 }
 
 static void virtio_gpu_cmd_get_display_info_cb(struct virtio_gpu_device *vgdev,