On Mon,  7 May 2018 15:10:44 -0700
Sridhar Samudrala [off-list ref] wrote:

+	if (netif_running(failover_dev)) {
+		err = dev_open(slave_dev);
+		if (err && (err != -EBUSY)) {
+			netdev_err(failover_dev, "Opening slave %s failed err:%d\n",
+				   slave_dev->name, err);
+			goto err_dev_open;
+		}
+	}
+
+	netif_addr_lock_bh(failover_dev);
+	dev_uc_sync_multiple(slave_dev, failover_dev);
+	dev_uc_sync_multiple(slave_dev, failover_dev);
+	netif_addr_unlock_bh(failover_dev);
+

The order of these is backwards, you want to sync addresses before bringing up.
Also, doing it this way does not allow udev/systemd the chance to rename VF devices.

The complexity of this whole failover mechanism does not make life easier,
more reliable, or safer for netvsc. I though that was the whole reason for having
common code.