net/mlx5e: Unblock setting vid 0 for VFs through the uplink rep

It turns out that libvirt uses 0-vid as a default if no vlan was
set for the guest (which is the case for switchdev mode) and errs
if we disallow that:

error: Failed to start domain vm75
error: Cannot set interface MAC/vlanid to 6a:66:2d:48:92:c2/0 \
		for ifname enp59s0f0 vf 0: Operation not supported

So allow this in order not to break existing systems.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reported-by: Maor Dickman <maord@mellanox.com>
Reviewed-by: Gavi Teitz <gavi@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_rep.c

@@ -1293,6 +1293,18 @@ static int mlx5e_uplink_rep_set_mac(struct net_device *netdev, void *addr)
 	return 0;
 }
 
+static int mlx5e_uplink_rep_set_vf_vlan(struct net_device *dev, int vf, u16 vlan, u8 qos,
+					__be16 vlan_proto)
+{
+	netdev_warn_once(dev, "legacy vf vlan setting isn't supported in switchdev mode\n");
+
+	if (vlan != 0)
+		return -EOPNOTSUPP;
+
+	/* allow setting 0-vid for compatibility with libvirt */
+	return 0;
+}
+
 static const struct switchdev_ops mlx5e_rep_switchdev_ops = {
 	.switchdev_port_attr_get	= mlx5e_attr_get,
 };
@@ -1327,6 +1339,7 @@ static const struct net_device_ops mlx5e_netdev_ops_uplink_rep = {
 	.ndo_set_vf_rate         = mlx5e_set_vf_rate,
 	.ndo_get_vf_config       = mlx5e_get_vf_config,
 	.ndo_get_vf_stats        = mlx5e_get_vf_stats,
+	.ndo_set_vf_vlan         = mlx5e_uplink_rep_set_vf_vlan,
 };
 
 bool mlx5e_eswitch_rep(struct net_device *netdev)