从ibv_create_cq（）返回的CQ

期望从CQ读取的WC数

从CQ读取的WC数num_entries的数组。（Array of size num_entries of the Work Completions that will be read from the CQ）

与WR对应关联的64 bit值 （The 64 bits value that was associated with the corresponding Work Request）

Status of the operation. The value can be one of the following enumerated values and their numeric value:

操作状态。该值可以是下列枚举值及其数字值之一：

• IBV_WC_SUCCESS (0) - Operation completed successfully: this means that the corresponding Work Request (and all of the unsignaled Work Requests that were posted previous to it) ended and the memory buffers that this Work Request refers to are ready to be (re)used.
• IBV_WC_LOC_LEN_ERR (1) - Local Length Error: this happens if a Work Request that was posted in a local Send Queue contains a message that is greater than the maximum message size that is supported by the RDMA device port that should send the message or an Atomic operation which its size is different than 8 bytes was sent. This also may happen if a Work Request that was posted in a local Receive Queue isn't big enough for holding the incoming message or if the incoming message size if greater the maximum message size supported by the RDMA device port that received the message.
• IBV_WC_LOC_QP_OP_ERR (2) - Local QP Operation Error: an internal QP consistency error was detected while processing this Work Request: this happens if a Work Request that was posted in a local Send Queue of a UD QP contains an Address Handle that is associated with a Protection Domain to a QP which is associated with a different Protection Domain or an opcode which isn't supported by the transport type of the QP isn't supported (for example: RDMA Write over a UD QP).
• IBV_WC_LOC_EEC_OP_ERR (3) - Local EE Context Operation Error: an internal EE Context consistency error was detected while processing this Work Request (unused, since its relevant only to RD QPs or EE Context, which aren’t supported).
• IBV_WC_LOC_PROT_ERR (4) - Local Protection Error: the locally posted Work Request’s buffers in the scatter/gather list does not reference a Memory Region that is valid for the requested operation.
• IBV_WC_WR_FLUSH_ERR (5) - Work Request Flushed Error: A Work Request was in process or outstanding when the QP transitioned into the Error State.
• IBV_WC_MW_BIND_ERR (6) - Memory Window Binding Error: A failure happened when tried to bind a MW to a MR.
• IBV_WC_BAD_RESP_ERR (7) - Bad Response Error: an unexpected transport layer opcode was returned by the responder. Relevant for RC QPs.
• IBV_WC_LOC_ACCESS_ERR (8) - Local Access Error: a protection error occurred on a local data buffer during the processing of a RDMA Write with Immediate operation sent from the remote node. Relevant for RC QPs.
• IBV_WC_REM_INV_REQ_ERR (9) - Remote Invalid Request Error: The responder detected an invalid message on the channel. Possible causes include the operation is not supported by this receive queue (qp_access_flags in remote QP wasn't configured to support this operation), insufficient buffering to receive a new RDMA or Atomic Operation request, or the length specified in a RDMA request is greater than  bytes. Relevant for RC QPs.
• IBV_WC_REM_ACCESS_ERR (10) - Remote Access Error: a protection error occurred on a remote data buffer to be read by an RDMA Read, written by an RDMA Write or accessed by an atomic operation. This error is reported only on RDMA operations or atomic operations. Relevant for RC QPs.
• IBV_WC_REM_OP_ERR (11) - Remote Operation Error: the operation could not be completed successfully by the responder. Possible causes include a responder QP related error that prevented the responder from completing the request or a malformed WQE on the Receive Queue. Relevant for RC QPs.
• IBV_WC_RETRY_EXC_ERR (12) - Transport Retry Counter Exceeded: The local transport timeout retry counter was exceeded while trying to send this message. This means that the remote side didn't send any Ack or Nack. If this happens when sending the first message, usually this mean that the connection attributes are wrong or the remote side isn't in a state that it can respond to messages. If this happens after sending the first message, usually it means that the remote QP isn't available anymore. Relevant for RC QPs.
• IBV_WC_RNR_RETRY_EXC_ERR (13) - RNR Retry Counter Exceeded: The RNR NAK retry count was exceeded. This usually means that the remote side didn't post any WR to its Receive Queue. Relevant for RC QPs.
• IBV_WC_LOC_RDD_VIOL_ERR (14) - Local RDD Violation Error: The RDD associated with the QP does not match the RDD associated with the EE Context (unused, since its relevant only to RD QPs or EE Context, which aren't supported).
• IBV_WC_REM_INV_RD_REQ_ERR (15) - Remote Invalid RD Request: The responder detected an invalid incoming RD message. Causes include a Q_Key or RDD violation (unused, since its relevant only to RD QPs or EE Context, which aren't supported)
• IBV_WC_REM_ABORT_ERR (16) - Remote Aborted Error: For UD or UC QPs associated with a SRQ, the responder aborted the operation.
• IBV_WC_INV_EECN_ERR (17) - Invalid EE Context Number: An invalid EE Context number was detected (unused, since its relevant only to RD QPs or EE Context, which aren't supported).
• IBV_WC_INV_EEC_STATE_ERR (18) - Invalid EE Context State Error: Operation is not legal for the specified EE Context state (unused, since its relevant only to RD QPs or EE Context, which aren't supported).
• IBV_WC_FATAL_ERR (19) - Fatal Error.
• IBV_WC_RESP_TIMEOUT_ERR (20) - Response Timeout Error.
• IBV_WC_GENERAL_ERR (21) - General Error: other error which isn't one of the above errors.

相应的工作请求执行的操作。此值控制数据的发送方式、数据流的方向以及“工作完成”中的有效属性。该值可以是下列枚举值之一：

• IBV_WC_SEND - 已发布到“发送队列”中的WR的发送操作（Send operation for a WR that was posted to the Send Queue） 
• IBV_WC_RDMA_WRITE - 已发布到发送队列的WR的RDMA写操作（RDMA Write operation for a WR that was posted to the Send Queue）
• IBV_WC_RDMA_READ - 已发布到发送队列的WR的RDMA读取操作（RDMA Read operation for a WR that was posted to the Send Queue）
• IBV_WC_COMP_SWAP - 已发布到“发送队列”中的WR的比较和交换操作（Compare and Swap operation for a WR that was posted to the Send Queue）
• IBV_WC_FETCH_ADD - 已发布到发送队列的WR的获取和添加操作（Fetch and Add operation for a WR that was posted to the Send Queue）
• IBV_WC_BIND_MW - 已发布到“发送队列”中的WR的“内存窗口”绑定操作（Memory Window bind operation for a WR that was posted to the Send Queue）
• IBV_WC_RECV - 发送已发布到（QP或SRQ的）接收队列的WR的数据操作（Send data operation for a WR that was posted to a Receive Queue (of a QP or to an SRQ)）
• IBV_WC_RECV_RDMA_WITH_IMM -  发送到（QP或SRQ）的接收队列的WR的带立即数的RDMA。对于此操作码，仅消耗一个接收请求，并且未使用此RR的sg_list（RDMA with immediate for a WR that was posted to a Receive Queue (of a QP or to an SRQ). For this opcode, only a Receive Request was consumed and the sg_list of this RR wasn't used）

供应商特定的错误，如果completion 因错误而结束，则会提供更多信息。一旦WC以错误结束，该值向RDMA设备的供应商提供有关失败原因的提示。

传输的字节数。与incoming Send或 RDMA Write with immediate operations的接收队列有关。该值不包括立即数的长度（如果存在）。与RDMA读取和原子操作的“发送队列”相关。对于不与SRQ关联的UD QP的接收队列，或者对于与UD QP关联的SRQ，该值等于消息的有效负载加上为GRH保留的40个字节。传输的字节数是消息的有效负载加上为GRH保留的40个字节（无论是否存在GRH）

（The number of bytes transferred. Relevant if the Receive Queue for incoming Send or RDMA Write with immediate operations. This value doesn't include the length of the immediate data, if such exists. Relevant in the Send Queue for RDMA Read and Atomic operations.For the Receive Queue of a UD QP that is not associated with an SRQ or for an SRQ that is associated with a UD QP this value equals to the payload of the message plus the 40 bytes reserved for the GRH.The number of bytes transferred is the payload of the message plus the 40 bytes reserved for the GRH, whether or not the GRH is present）

（可选）以网络顺序的SEND或RDMA WRITE操作码中的32 bit 数字，与有效载荷一起发送到远程端，并放置在[接收工作完]（ Receive Work Completion）成中，而不是在远端内存缓冲区中。如果设置了IBV_WC_WITH_IMM，则此值有效

已完成的WR的本地QP的号码。与和SRQ相关的[接收工作完成](Receive Work Completions)相关.

(Local QP number of completed WR. Relevant for Receive Work Completions that are associated with an SRQ)

• IBV_WC_GRH - Indicator that GRH is present for a Receive Work Completions of a UD QP. If this bit is set, the first 40 bytes of the buffered that were referred to in the Receive request will contain the GRH of the incoming message. If this bit is cleared, the content of those first 40 bytes is undefined
• IBV_WC_WITH_IMM - Indicator that imm_data is valid. Relevant for Receive Work Completions

从CQ读取的WC数及其值在wc中返回。如果该值小于num_entries，则表示CQ中没有更多的工作完成。如果此值等于num_entries，则CQ中可能会有更多的工作完成

尝试从CQ读取WC(工作完成)时发生故障