From 986ef95ecdd3eb6fa29433e68faa94c7624083be Mon Sep 17 00:00:00 2001 From: Sagi Grimberg Date: Thu, 31 Mar 2016 19:03:25 +0300 Subject: 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 Tested-by: Christoph Hellwig Signed-off-by: Sagi Grimberg Signed-off-by: Leon Romanovsky Signed-off-by: Doug Ledford --- include/linux/mlx5/device.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'include/linux') diff --git a/include/linux/mlx5/device.h b/include/linux/mlx5/device.h index 8156e3c9239c..b3575f392492 100644 --- a/include/linux/mlx5/device.h +++ b/include/linux/mlx5/device.h @@ -392,6 +392,17 @@ 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]; -- cgit v1.2.3