mlx4_ib_find_real_gid
int mlx4_ib_find_real_gid(struct ib_device *ibdev, u8 port, __be64 guid);
*slave = mlx4_ib_find_real_gid(ibdev, port, gid.global.interface_id);
slave = mlx4_ib_find_real_gid(ibdev, port, grh->dgid.global.interface_id);