[PATCH 3/3] migration/rdma: Retry control sends on full queue

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;
+    }
+
     if (ret > 0) {
         error_setg(errp, "Failed to use post IB SEND for control");
         return -1;
-- 
2.20.1