On Mon, Aug 17, 2026 at 06:51:17PM +0800, Yanfei Xu wrote:
> RAM writes and control messages share the send queue. If
> outstanding writes fill it, RDMA writes drain a completion and retry,
> but control sends fail the migration.
>
> Drain one outstanding write and retry the control send on ENOMEM.
>
> Signed-off-by: Yanfei Xu <[email protected]>
> ---
> migration/rdma.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 6e8436ccc1..d1f44a5f55 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -1572,9 +1572,19 @@ static int qemu_rdma_post_send_control(RDMAContext
> *rdma, uint8_t *buf,
> memcpy(wr->control + sizeof(RDMAControlHeader), buf, head->len);
> }
>
> -
> +retry:
> ret = ibv_post_send(rdma->qp, &send_wr, &bad_wr);
>
> + if (ret == ENOMEM && rdma->nb_sent) {
> + ret = qemu_rdma_block_for_wrid(rdma, RDMA_WRID_RDMA_WRITE, NULL);
> + if (ret < 0) {
> + error_setg(errp, "rdma migration: failed to make room for "
> + "control send");
> + return -1;
> + }
> + goto retry;
> + }
Looks also correct, but two questions:
- Should we provide a helper instead of duplicating the WRITE op handling?
I believe only WRITE wrids can be on the fly.
- Could ENOMEM be returned when nb_sent==0? If that check applies to WRITE
path too?
Thanks,
> +
> if (ret > 0) {
> error_setg(errp, "Failed to use post IB SEND for control");
> return -1;
> --
> 2.20.1
>
--
Peter Xu
