mlx5dv_wr_post (3) - Linux Manuals

mlx5dv_wr_post: Attach a DC info to the last work request

NAME

mlx5dv_wr_set_dc_addr - Attach a DC info to the last work request

SYNOPSIS

#include <infiniband/mlx5dv.h>

static inline void mlx5dv_wr_set_dc_addr(struct mlx5dv_qp_ex *mqp,
                                         struct ibv_ah *ah,
                                         uint32_t remote_dctn,
                                         uint64_t remote_dc_key);

struct mlx5dv_mr_interleaved {
    uint64_t        addr;
    uint32_t        bytes_count;
    uint32_t        bytes_skip;
    uint32_t        lkey;
};

static inline void mlx5dv_wr_mr_interleaved(struct mlx5dv_qp_ex *mqp,
                        struct mlx5dv_mkey *mkey,
                        uint32_t access_flags, /* use enum ibv_access_flags */
                        uint32_t repeat_count,
                        uint16_t num_interleaved,
                        struct mlx5dv_mr_interleaved *data);

static inline void mlx5dv_wr_mr_list(struct mlx5dv_qp_ex *mqp,
                      struct mlx5dv_mkey *mkey,
                      uint32_t access_flags, /* use enum ibv_access_flags */
                      uint16_t num_sges,
                      struct ibv_sge *sge);

DESCRIPTION

The MLX5DV work request APIs (mlx5dv_wr_*) is an extension for IBV work request API (ibv_wr_*) with mlx5 specific features for send work request. This may be used together with or without ibv_wr_* calls.

USAGE

To use these APIs a QP must be created using mlx5dv_create_qp() with send_ops_flags of struct ibv_qp_init_attr_ex set.

If the QP does not support all the requested work request types then QP creation will fail.

The mlx5dv_qp_ex is extracted from the IBV_QP by ibv_qp_to_qp_ex() and mlx5dv_qp_ex_from_ibv_qp_ex(). This should be used to apply the mlx5 specific features on the posted WR.

A work request creation requires to use the ibv_qp_ex as described in the man for ibv_wr_post and mlx5dv_qp with its available builders and setters.

QP Specific builders

RC QPs

mlx5dv_wr_mr_interleaved()

registers an interleaved memory layout by using an indirect mkey and some interleaved data. The layout of the memory pointed by the mkey after its registration will be the data representation for the num_interleaved entries. This single layout representation is repeated by repeat_count.

The data as described by struct mlx5dv_mr_interleaved will hold real data defined by bytes_count and then a padding of bytes_skip. Post a successful registration, RDMA operations can use this mkey. The hardware will scatter the data according to the pattern. The mkey should be used in a zero-based mode. The addr field in its ibv_sge is an offset in the total data.

Current implementation requires the IBV_SEND_INLINE option to be on in ibv_qp_ex->wr_flags field. To be able to have more than 3 num_interleaved entries, the QP should be created with a larger WQE size that may fit it. This should be done using the max_inline_data attribute of struct ibv_qp_cap upon its creation.

As one entry will be consumed for strided header, the mkey should be created with one more entry than the required num_interleaved.

In case ibv_qp_ex->wr_flags turns on IBV_SEND_SIGNALED, the reported WC opcode will be MLX5DV_WC_UMR. Unregister the mkey to enable another pattern registration should be done via ibv_post_send with IBV_WR_LOCAL_INV opcode.

mlx5dv_wr_mr_list()

registers a memory layout based on list of ibv_sge. The layout of the memory pointed by the mkey after its registration will be based on the list of sge counted by num_sges. Post a successful registration RDMA operations can use this mkey, the hardware will scatter the data according to the pattern. The mkey should be used in a zero-based mode, the addr field in its ibv_sge is an offset in the total data.

Current implementation requires the IBV_SEND_INLINE option to be on in ibv_qp_ex->wr_flags field. To be able to have more than 4 num_sge entries, the QP should be created with a larger WQE size that may fit it. This should be done using the max_inline_data attribute of struct ibv_qp_cap upon its creation.

In case ibv_qp_ex->wr_flags turns on IBV_SEND_SIGNALED, the reported WC opcode will be MLX5DV_WC_UMR. Unregister the mkey to enable other pattern registration should be done via ibv_post_send with IBV_WR_LOCAL_INV opcode.

QP Specific setters

DCI QPs

mlx5dv_wr_set_dc_addr() must be called to set the DCI WR properties. The destination address of the work is specified by ah, the remote DCT number is specified by remote_dctn and the DC key is specified by remote_dc_key. This setter is available when the QP transport is DCI and send_ops_flags in struct ibv_qp_init_attr_ex is set. The available builders and setters for DCI QP are the same as RC QP.

EXAMPLE

/* create DC QP type and specify the required send opcodes */
attr_ex.qp_type = IBV_QPT_DRIVER;
attr_ex.comp_mask |= IBV_QP_INIT_ATTR_SEND_OPS_FLAGS;
attr_ex.send_ops_flags |= IBV_QP_EX_WITH_RDMA_WRITE;

attr_dv.comp_mask |= MLX5DV_QP_INIT_ATTR_MASK_DC;
attr_dv.dc_init_attr.dc_type = MLX5DV_DCTYPE_DCI;

ibv_qp *qp = mlx5dv_create_qp(ctx, attr_ex, attr_dv);
ibv_qp_ex *qpx = ibv_qp_to_qp_ex(qp);
mlx5dv_qp_ex *mqpx = mlx5dv_qp_ex_from_ibv_qp_ex(qpx);

ibv_wr_start(qpx);

/* Use ibv_qp_ex object to set WR generic attributes */
qpx->wr_id = my_wr_id_1;
qpx->wr_flags = IBV_SEND_SIGNALED;
ibv_wr_rdma_write(qpx, rkey, remote_addr_1);
ibv_wr_set_sge(qpx, lkey, local_addr_1, length_1);

/* Use mlx5 DC setter using mlx5dv_qp_ex object */
mlx5dv_wr_set_wr_dc_addr(mqpx, ah, remote_dctn, remote_dc_key);

ret = ibv_wr_complete(qpx);

AUTHOR

Guy Levi <guyle [at] mellanox.com>