2 files changed, 15 insertions, 0 deletions

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 596de212fe7e..97f26f0aab40 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1658,6 +1658,20 @@ void vhost_add_used_and_signal_n(struct vhost_dev *dev,
 }
 EXPORT_SYMBOL_GPL(vhost_add_used_and_signal_n);
 
+/* return true if we're sure that avaiable ring is empty */
+bool vhost_vq_avail_empty(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+{
+        __virtio16 avail_idx;
+        int r;
+
+        r = __get_user(avail_idx, &vq->avail->idx);
+        if (r)
+                return false;
+
+        return vhost16_to_cpu(vq, avail_idx) == vq->avail_idx;
+}
+EXPORT_SYMBOL_GPL(vhost_vq_avail_empty);
+
 /* OK, now we need to know about added descriptors. */
 bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
 {
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index eef33b11a7ed..af5af773bf7a 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -159,6 +159,7 @@ void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *,
                                struct vring_used_elem *heads, unsigned count);
 void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
 void vhost_disable_notify(struct vhost_dev *, struct vhost_virtqueue *);
+bool vhost_vq_avail_empty(struct vhost_dev *, struct vhost_virtqueue *);
 bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *);
 
 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,