RDMA_CREATE_QP(3)

💅 RDMA_CREATE_QP(3) — the librdmacm programmer's manual, but make it cute ✨

okay bestie, sit down, hydrate, because we're allocating a Queue Pair and it's actually not that deep once you get the vibe 🦋

✨ NAME ✨

rdma_create_qp — Allocate a QP. that's it. that's the whole job. iconic behavior honestly 💖

🌸 SYNOPSIS 🌸

#include <rdma/rdma_cma.h>

int rdma_create_qp (struct rdma_cm_id *id, struct ibv_pd *pd, struct
ibv_qp_init_attr *qp_init_attr);

look at her. three args. she's lowkey slaying 🌈

🎀 ARGUMENTS 🎀

• id — the RDMA identifier. your main character. 💫
• pd — optional protection domain for the QP. optional!! she can be NULL, we'll get to that 🫶
• qp_init_attr — the initial QP attributes. the lewk, if you will ✨

💖 DESCRIPTION 💖

So what we're doing here is allocating a QP that's associated with the specified rdma_cm_id, and then transitioning it so it's ready for sending and receiving. that's the whole plot. no cap 💅

⭐ RETURN VALUE ⭐

Returns 0 on success, or -1 on error. and if an error happens, errno gets set to tell you why, which is genuinely so thoughtful of her 😭

🧚 NOTES 🧚

• The rdma_cm_id must be bound to a local RDMA device before you call this function. and the protection domain has to be for that same device. periodt. 🙈
• QPs allocated to an rdma_cm_id get automatically transitioned by the librdmacm through their states — you don't have to babysit them, she's self-sufficient 💜
• After being allocated, the QP will be ready to handle posting of receives. and if the QP is unconnected, it'll be ready to post sends too. go off 🔥
• If a protection domain is not given — like, the pd parameter is NULL — then the rdma_cm_id will be created using a default protection domain. and here's the tea: one default protection domain is allocated per RDMA device. one. per device. 🍓
• The initial QP attributes are specified by the qp_init_attr parameter. the send_cq and recv_cq fields in the ibv_qp_init_attr are optional — if you don't specify a send or receive completion queue, then a CQ will be allocated by the rdma_cm for the QP, along with corresponding completion channels. and those completion channels and CQ data created by the rdma_cm? they get exposed to the user through the rdma_cm_id structure. it's giving generous. it's giving sharing. 💝
• The actual capabilities and properties of the created QP will be returned to you through the qp_init_attr parameter. so check it after, bestie, she updates it in place ✨
• An rdma_cm_id may only be associated with a single QP. one. monogamy. no sharing, no side quests. 👑

👑 SEE ALSO 👑

• rdma_bind_addr(3)
• rdma_resolve_addr(3)
• rdma_destroy_qp(3)
• ibv_create_qp(3)
• ibv_modify_qp(3)

the whole friend group. go read them too 🫶

that's the page, babe. now go bind your id and allocate responsibly. mwah 💋

this has been librdmacm, dated 2007-05-15 — yes she's vintage, yes she still eats. RDMA_CREATE_QP(3) out. 💅✨