4.5-stable review patch. If anyone has any objections, please let me know.
------------------ From: Sagi Grimberg <s...@grimberg.me> commit 986ef95ecdd3eb6fa29433e68faa94c7624083be upstream. 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. Reported-by: Christoph Hellwig <h...@lst.de> Tested-by: Christoph Hellwig <h...@lst.de> Signed-off-by: Sagi Grimberg <sa...@grimberg.me> Signed-off-by: Leon Romanovsky <leo...@mellanox.com> Signed-off-by: Doug Ledford <dledf...@redhat.com> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- drivers/infiniband/hw/mlx5/main.c | 2 +- include/linux/mlx5/device.h | 11 +++++++++++ 2 files changed, 12 insertions(+), 1 deletion(-) --- a/drivers/infiniband/hw/mlx5/main.c +++ b/drivers/infiniband/hw/mlx5/main.c @@ -517,7 +517,7 @@ static int mlx5_ib_query_device(struct i 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); --- a/include/linux/mlx5/device.h +++ b/include/linux/mlx5/device.h @@ -363,6 +363,17 @@ enum { MLX5_CAP_OFF_CMDIF_CSUM = 46, }; +enum { + /* + * Max wqe size for rdma read is 512 bytes, so this + * limits our max_sge_rd as the wqe needs to fit: + * - ctrl segment (16 bytes) + * - rdma segment (16 bytes) + * - scatter elements (16 bytes each) + */ + MLX5_MAX_SGE_RD = (512 - 16 - 16) / 16 +}; + struct mlx5_inbox_hdr { __be16 opcode; u8 rsvd[4];