rdmacreateqp

rdmacreateqp is a function in the RDMA core API used to create a queue pair (QP) for communication on an RDMA device. A QP represents a pair of communication endpoints—the send and receive contexts that participate in RDMA operations such as remote memory access and one-sided transfers. The function is typically used after obtaining a device context and a protection domain, and it serves as the primary means to initialize the hardware resources required for RDMA messaging.

In a typical workflow, an application opens the RDMA device to obtain a device context, allocates a protection domain, and then calls rdmacreateqp with that context and PD along with a specification of the desired QP attributes. These attributes generally describe capabilities such as queue depths, the type of QP (for example, reliable connected RC, unreliable datagram UD, or others), and related parameters relevant to the underlying hardware and verbs library. The call returns a handle to the new QP on success or an error code on failure.

Once created, the QP must be transitioned through its required states (e.g., INIT, RTR, RTS) using appropriate verbs or helper routines, and it is typically paired with a completion queue. Proper memory registration, queue pair configuration, and synchronization with the remote peer are necessary for correct operation. The exact prototype and usage can vary between RDMA libraries and backends, so developers should refer to the specific library’s documentation for precise details.

rdmacreateqp is part of the broader RDMA verbs ecosystem, which also includes operations for creating completion queues, memory regions, and protection domains, as well as utilities for resolving addresses and managing connections.