ibvallocpd

ibv_alloc_pd is a function in the libibverbs API used to allocate a protection domain (PD) for a given RDMA device context. A protection domain provides an isolation boundary for memory regions, queue pairs, and other resources, ensuring that memory registrations and queue pairs created within the PD can only access memory and resources associated with that same PD.

The function takes a single argument: a pointer to a populated RDMA device context (struct ibv_context *context). On success, it returns a pointer to a newly allocated protection domain (struct ibv_pd *). On failure, it returns NULL and sets errno to indicate the error.

A protection domain serves as a scope for resources used in RDMA operations. Memory regions registered with a PD (via ibv_reg_mr) and queue pairs (via ibv_create_qp) are associated with that PD, enabling protection checks and isolation from other PDs. PDs are specific to the device context they are created from and must be released when no longer needed.

To release resources, the application calls ibv_dealloc_pd with the pointer returned by ibv_alloc_pd. Deallocation frees the PD and its associated resources, and any outstanding references should be cleaned up before deallocation.

Common error conditions include insufficient resources (ENOMEM), invalid or closed context (EINVAL or ENODEV), or other device-specific failures. The exact error codes depend on the system and the RDMA hardware.

See also: ibv_dealloc_pd, ibv_reg_mr, ibv_create_qp. ibv_alloc_pd is a foundational step in setting up RDMA resources on a device and is typically performed after opening an RDMA device context and before configuring memory regions or queue pairs.