RDMA/mlx5: Add attr for max number page list length for PI operation

PI offload (protection information) is a feature that each RDMA provider
can implement differently. Thus, introduce new device attribute to define
the maximal length of the page list for PI fast registration operation. For
example, mlx5 driver uses a single internal MR to map both data and
protection SGL's, so it's equal to max_fast_reg_page_list_len / 2.
Signed-off-by: NMax Gurtovoy <maxg@mellanox.com>
Reviewed-by: NLeon Romanovsky <leonro@mellanox.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/mlx5/main.c

@@ -1009,6 +1009,8 @@ static int mlx5_ib_query_device(struct ib_device *ibdev,
 	props->max_srq_sge	   = max_rq_sg - 1;
 	props->max_fast_reg_page_list_len =
 		1 << MLX5_CAP_GEN(mdev, log_max_klm_list_size);
+	props->max_pi_fast_reg_page_list_len =
+		props->max_fast_reg_page_list_len / 2;
 	get_atomic_caps_qp(dev, props);
 	props->masked_atomic_cap   = IB_ATOMIC_NONE;
 	props->max_mcast_grp	   = 1 << MLX5_CAP_GEN(mdev, log_max_mcg);

include/rdma/ib_verbs.h

@@ -390,6 +390,7 @@ struct ib_device_attr {
 	int			max_srq_wr;
 	int			max_srq_sge;
 	unsigned int		max_fast_reg_page_list_len;
+	unsigned int		max_pi_fast_reg_page_list_len;
 	u16			max_pkeys;
 	u8			local_ca_ack_delay;
 	int			sig_prot_cap;