Use vhost_dev->mutex to protect vhost device iotlb from
concurrent access.

Fixes: 4c8cf318("vhost: introduce vDPA-based backend")
Signed-off-by: Xie Yongji <redacted>
---
  drivers/vhost/vdpa.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index c50079dfb281..5500e3bf05c1 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c

@@ -723,6 +723,7 @@ static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev,
  	if (r)
  		return r;
  
+	mutex_lock(&dev->mutex);

  	switch (msg->type) {
  	case VHOST_IOTLB_UPDATE:
  		r = vhost_vdpa_process_iotlb_update(v, msg);

@@ -742,6 +743,7 @@ static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev,
  		r = -EINVAL;
  		break;
  	}
+	mutex_unlock(&dev->mutex);
  
  	return r;
  }