RDMA atomic operations fail

When I try to submit an RDMA FETCH_AND_ADD or CMP_AND_SWAP , the ibv_post_send() function fails, with Errno set to "Invalid argument". I have no such problems with RDMA READ/WRITE.

I developed my entire code using RDMA CM (so no manual QP transitioning). The queue pair is RC, and Atomic is enabled at the responder queue pair, and the memory regions are registered with atomic access.

I suspected that there might be the source of this problem,
so I wrote a small program using libibcm where I transition the QPs manually and set the flags fro atomic operations:
qp_attr->qp_access_flags = IBV_ACCESS_REMOTE_ATOMIC; qp_attr->max_rd_atomic = <something greater than zero>; qp_attr->max_dest_rd_atomic = <something greater than zero>;

But still, the same error (invalid argument).

I'd appreciate your help.

I'm using ConnectIB.

This is my send_wr code:

struct ibv_send_wr wr, *bad_wr = NULL;
struct ibv_sge sge;
memset(&sge, 0, sizeof(sge));
sge.addr = (uintptr_t)conn->local_buffer; sge.length = 8;
sge.lkey = conn->local_mr->lkey;
memset(&wr, 0, sizeof(wr));
wr.wr_id= 0;
wr.opcode = IBV_WR_ATOMIC_FETCH_AND_ADD; wr.sg_list = &sge;
wr.num_sge = 1;
wr.send_flags = IBV_SEND_SIGNALED; wr.wr.atomic.remote_addr= (uintptr_t)conn->peer_mr.addr; wr.wr.atomic.rkey = conn->peer_mr.rkey; wr.wr.atomic.compare_add= 1ULL;

if (ibv_post_send(conn->qp, &wr, &bad_wr)) { fprintf(stderr, "Error, ibv_post_send() failed\n"); die("");
}

When I try to submit an RDMA FETCH_AND_ADD or CMP_AND_SWAP , the ibv_post_send() function fails, with Errno set to "Invalid argument". I have no such problems with RDMA READ/WRITE.

I developed my entire code using RDMA CM (so no manual QP transitioning). The queue pair is RC, and Atomic is enabled at the responder queue pair, and the memory regions are registered with atomic access.

I suspected that there might be the source of this problem,
so I wrote a small program using libibcm where I transition the QPs manually and set the flags fro atomic operations:
qp_attr->qp_access_flags = IBV_ACCESS_REMOTE_ATOMIC; qp_attr->max_rd_atomic = <something greater than zero>; qp_attr->max_dest_rd_atomic = <something greater than zero>;

But still, the same error (invalid argument).

Quoted 8 lines · floaterions

When I try to submit an RDMA FETCH_AND_ADD or CMP_AND_SWAP , the ibv_post_send() function fails, with Errno set to "Invalid argument". I have no such problems with RDMA READ/WRITE.

I developed my entire code using RDMA CM (so no manual QP transitioning). The queue pair is RC, and Atomic is enabled at the responder queue pair, and the memory regions are registered with atomic access.

Quoted 9 lines

I suspected that there might be the source of this problem,
so I wrote a small program using libibcm where I transition the QPs manually and set the flags fro atomic operations:
qp_attr->qp_access_flags = IBV_ACCESS_REMOTE_ATOMIC; qp_attr->max_rd_atomic = <something greater than zero>; qp_attr->max_dest_rd_atomic = <something greater than zero>;

But still, the same error (invalid argument).

Hi,
the current code in upstream does not support atomic operations. Patches were sent already that will allow to use atomic operations over mlx5 supported devices.

For now, if you query the HCA capabilites you should get ATOMIC_NONE at the atomic_cap field when you query the device capabilites.