ibv_create_cq_ex (3)

NAME

ibv_create_cq_ex - create a completion queue (CQ)

SYNOPSIS

#include <infiniband/verbs.h>

struct ibv_cq_ex *ibv_create_cq_ex(struct ibv_context *context,
                                   struct ibv_create_cq_attr_ex *cq_attr);

DESCRIPTION

ibv_create_cq_ex() creates a completion queue (CQ) for RDMA device context context. The argument cq_attr is a pointer to struct ibv_create_cq_attr_ex as defined in <infiniband/verbs.h>.

struct ibv_create_cq_attr_ex {
int                     cqe;               /* Minimum number of entries required for CQ */
void                    *cq_context;       /* Consumer-supplied context returned for completion events */
struct ibv_comp_channel *channel;          /* Completion channel where completion events will be queued. May be NULL if completion events will not be used. */
int                     comp_vector;       /* Completion vector used to signal completion events. Must be >= 0 and < context->num_comp_vectors. */
uint64_t                wc_flags;          /* The wc_flags that should be returned in ibv_poll_cq_ex. Or'ed bit of enum ibv_wc_flags_ex. */
uint32_t                comp_mask;         /* compatibility mask (extended verb). */
};

enum ibv_wc_flags_ex {
        IBV_WC_EX_WITH_BYTE_LEN              = 1 << 0,  /* Require byte len in WC */
        IBV_WC_EX_WITH_IMM                   = 1 << 1,  /* Require immediate in WC */
        IBV_WC_EX_WITH_QP_NUM                = 1 << 2,  /* Require QP number in WC */
        IBV_WC_EX_WITH_SRC_QP                = 1 << 3,  /* Require source QP in WC */
        IBV_WC_EX_WITH_SLID                  = 1 << 4,  /* Require slid in WC */
        IBV_WC_EX_WITH_SL                    = 1 << 5,  /* Require sl in WC */
        IBV_WC_EX_WITH_DLID_PATH_BITS        = 1 << 6,  /* Require dlid path bits in WC */
        IBV_WC_EX_WITH_COMPLETION_TIMESTAMP  = 1 << 7,  /* Require completion timestamp in WC /*
};

enum ibv_cq_init_attr_mask {
        IBV_CQ_INIT_ATTR_MASK_FLAGS             = 1 << 0,
};

enum ibv_create_cq_attr_flags {
        IBV_CREATE_CQ_ATTR_SINGLE_THREADED      = 1 << 0, /* This CQ is used from a single threaded, thus no locking is required */
};

Polling an extended CQ

In order to poll an extended CQ efficiently, a user could use the following functions.

Completion iterator functions

int ibv_start_poll(struct ibv_cq_ex *cq, struct ibv_poll_cq_attr *attr)
Start polling a batch of work completions. attr is given in order to make this function easily extensible in the future. This function either returns 0 on success or an error code otherwise. When no completions are available on the CQ, ENOENT is returned, but the CQ remains in a valid state. On success, querying the completion's attribute could be done using the query functions described below. If an error code is given, end_poll shouldn't be called.
int ibv_next_poll(struct ibv_cq_ex *cq)
This function is called in order to get the next work completion. It has to be called after start_poll and before end_poll are called. This function either returns 0 on success or an error code otherwise. When no completions are available on the CQ, ENOENT is returned, but the CQ remains in a valid state. On success, querying the completion's attribute could be done using the query functions described below. If an error code is given, end_poll should still be called, indicating this is the end of the polled batch.
void ibv_end_poll(struct ibv_cq_ex *cq)
This function indicates the end of polling batch of work completions. After calling this function, the user should start a new batch by calling start_poll.

Polling fields in the completion

Below members and functions are used in order to poll the current completion. The current completion is the completion which the iterator points to (start_poll and next_poll advances this iterator). Only fields that the user requested via wc_flags in ibv_create_cq_ex could be queried. In addition, some fields are only valid in certain opcodes and status codes.
uint64_t wr_id - Can be accessed directly from struct ibv_cq_ex.
enum ibv_wc_status - Can be accessed directly from struct ibv_cq_ex.
enum ibv_wc_opcode ibv_wc_read_opcode(struct ibv_cq_ex *cq);
 Get the opcode from the current completion.
uint32_t ibv_wc_read_vendor_err(struct ibv_cq_ex *cq);
 Get the vendor error from the current completion.
uint32_t ibv_wc_read_byte_len(struct ibv_cq_ex *cq);
 Get the vendor error from the current completion.
uint32_t ibv_wc_read_imm_data(struct ibv_cq_ex *cq);
 Get the immediate data field from the current completion.
uint32_t ibv_wc_read_qp_num(struct ibv_cq_ex *cq);
 Get the QP number field from the current completion.
uint32_t ibv_wc_read_src_qp(struct ibv_cq_ex *cq);
 Get the source QP number field from the current completion.
int ibv_wc_read_wc_flags(struct ibv_cq_ex *cq);
 Get the QP flags field from the current completion.
uint16_t ibv_wc_read_pkey_index(struct ibv_cq_ex *cq);
 Get the pkey index field from the current completion.
uint32_t ibv_wc_read_slid(struct ibv_cq_ex *cq);
 Get the slid field from the current completion.
uint8_t ibv_wc_read_sl(struct ibv_cq_ex *cq);
 Get the sl field from the current completion.
uint8_t ibv_wc_read_dlid_path_bits(struct ibv_cq_ex *cq);
 Get the dlid_path_bits field from the current completion.
uint64_t ibv_wc_read_completion_ts(struct ibv_cq_ex *cq);
 Get the completion timestamp from the current completion.

RETURN VALUE

ibv_create_cq_ex() returns a pointer to the CQ, or NULL if the request fails.

NOTES

ibv_create_cq_ex() may create a CQ with size greater than or equal to the requested size. Check the cqe attribute in the returned CQ for the actual size.

CQ should be destroyed with ibv_destroy_cq.

SEE ALSO

ibv_create_cq(3), ibv_destroy_cq(3), ibv_resize_cq(3), ibv_req_notify_cq(3), ibv_ack_cq_events(3), ibv_create_qp(3)

AUTHORS

Matan Barak <matanb@mellanox.com>