diff --git a/drivers/infiniband/hw/mlx4/main.c b/drivers/infiniband/hw/mlx4/main.c
index d57563b..c7586a1 100644
--- a/drivers/infiniband/hw/mlx4/main.c
+++ b/drivers/infiniband/hw/mlx4/main.c
@@ -1667,9 +1667,11 @@
 	qp = ibdev->qp1_proxy[port - 1];
 	if (qp) {
 		int new_smac_index;
-		u64 old_smac = qp->pri.smac;
+		u64 old_smac;
 		struct mlx4_update_qp_params update_params;
 
+		mutex_lock(&qp->mutex);
+		old_smac = qp->pri.smac;
 		if (new_smac == old_smac)
 			goto unlock;
 
@@ -1684,17 +1686,20 @@
 			release_mac = new_smac;
 			goto unlock;
 		}
-
+		/* if old port was zero, no mac was yet registered for this QP */
+		if (qp->pri.smac_port)
+			release_mac = old_smac;
 		qp->pri.smac = new_smac;
+		qp->pri.smac_port = port;
 		qp->pri.smac_index = new_smac_index;
-
-		release_mac = old_smac;
 	}
 
 unlock:
-	mutex_unlock(&ibdev->qp1_proxy_lock[port - 1]);
 	if (release_mac != MLX4_IB_INVALID_MAC)
 		mlx4_unregister_mac(ibdev->dev, port, release_mac);
+	if (qp)
+		mutex_unlock(&qp->mutex);
+	mutex_unlock(&ibdev->qp1_proxy_lock[port - 1]);
 }
 
 static void mlx4_ib_get_dev_addr(struct net_device *dev,