IB/mlx5: Expose correct max_sge_rd limit
mlx5 devices (Connect-IB, ConnectX-4, ConnectX-4-LX) has a limitation
where rdma read work queue entries cannot exceed 512 bytes.
A rdma_read wqe needs to fit in 512 bytes:
- wqe control segment (16 bytes)
- rdma segment (16 bytes)
- scatter elements (16 bytes each)
So max_sge_rd should be: (512 - 16 - 16) / 16 = 30.
Cc: linux-stable@vger.kernel.org
Reported-by: Christoph Hellwig <hch@lst.de>
Tested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sagi Grimberg <sagig@grimberg.me>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
index 5acf346..049754f 100644
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -530,7 +530,7 @@
sizeof(struct mlx5_wqe_ctrl_seg)) /
sizeof(struct mlx5_wqe_data_seg);
props->max_sge = min(max_rq_sg, max_sq_sg);
- props->max_sge_rd = props->max_sge;
+ props->max_sge_rd = MLX5_MAX_SGE_RD;
props->max_cq = 1 << MLX5_CAP_GEN(mdev, log_max_cq);
props->max_cqe = (1 << MLX5_CAP_GEN(mdev, log_max_cq_sz)) - 1;
props->max_mr = 1 << MLX5_CAP_GEN(mdev, log_max_mkey);