Commit c1be5232d21d ("Fix micro UAR allocator") broke binary compatibility between libmlx5 and mlx5_ib since it defines a different value to the number of micro UARs per page, leading to wrong calculation in libmlx5. This patch defines struct mlx5_ib_alloc_ucontext_req_v2 as an extension to struct mlx5_ib_alloc_ucontext_req. The extended size is determined in mlx5_ib_alloc_ucontext() and in case of old library we use uuarn 0 which works fine -- this is acheived due to create_user_qp() falling back from high to medium then to low class where low class will return 0. For new libraries we use the more sophisticated allocation algorithm. Signed-off-by: Eli Cohen <eli@mellanox.com> Reviewed-by: Yann Droneaud <ydroneaud@opteya.com> Signed-off-by: Roland Dreier <roland@purestorage.com>