IB/mlx5: Expose correct max_sge_rd limit (986ef95e) · Commits · 戴 / test

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>

drivers/infiniband/hw/mlx5/main.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -530,7 +530,7 @@ static int mlx5_ib_query_device(struct ib_device *ibdev,
		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);

include/linux/mlx5/device.h

+11 −0

Original line number	Diff line number	Diff line
		@@ -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];

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