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mlx4: Expose correct max_sge_rd limit 

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>
hifive-unleashed-5.1
Sagi Grimberg 2015-10-28 13:28:15 +02:00 committed by Doug Ledford
parent 533708867d
commit a5e14ba334
2 changed files with 12 additions and 1 deletions
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2
drivers/infiniband/hw/mlx4/main.c
View File

@ -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;

11
include/linux/mlx4/device.h
View File

@ -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,