mlx4: Expose correct max_sge_rd limit (a5e14ba3) · Commits · 戴 / test

mlx4 devices (ConnectX-2, ConnectX-3) 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. Signed-off-by:

Sagi Grimberg <sagig@mellanox.com> Reviewed-by:

Steve Wise <swise@opengridcomputing.com> Signed-off-by:

Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/mlx4/main.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -456,7 +456,7 @@ static int mlx4_ib_query_device(struct ib_device *ibdev,
		props->max_qp_wr = dev->dev->caps.max_wqes - MLX4_IB_SQ_MAX_SPARE;
		props->max_sge = min(dev->dev->caps.max_sq_sg,
		dev->dev->caps.max_rq_sg);
		props->max_sge_rd = props->max_sge;
		props->max_sge_rd = MLX4_MAX_SGE_RD;
		props->max_cq = dev->dev->quotas.cq;
		props->max_cqe = dev->dev->caps.max_cqes;
		props->max_mr = dev->dev->quotas.mpt;

include/linux/mlx4/device.h

+11 −0

Original line number	Diff line number	Diff line
		@@ -426,6 +426,17 @@ enum {
		MLX4_MAX_FAST_REG_PAGES = 511,
		};

		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)
		*/
		MLX4_MAX_SGE_RD = (512 - 16 - 16) / 16
		};

		enum {
		MLX4_DEV_PMC_SUBTYPE_GUID_INFO = 0x14,
		MLX4_DEV_PMC_SUBTYPE_PORT_INFO = 0x15,

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