[PATCH 1/2] migration: Fix rdma migration failed

From: Li Zhijian <lizhijian@fujitsu.com>
To: quintela@redhat.com, peterx@redhat.com, leobras@redhat.com
Cc: qemu-devel@nongnu.org, Li Zhijian <lizhijian@cn.fujitsu.com>
Subject: [PATCH 1/2] migration: Fix rdma migration failed
Date: Wed, 20 Sep 2023 17:04:11 +0800	[thread overview]
Message-ID: <20230920090412.726725-1-lizhijian@fujitsu.com> (raw)

From: Li Zhijian <lizhijian@cn.fujitsu.com>

Destination will fail with:
qemu-system-x86_64: rdma: Too many requests in this message (3638950032).Bailing.

migrate with RDMA is different from tcp. RDMA has its own control
message, and all traffic between RDMA_CONTROL_REGISTER_REQUEST and
RDMA_CONTROL_REGISTER_FINISHED should not be disturbed.

find_dirty_block() will be called during RDMA_CONTROL_REGISTER_REQUEST
and RDMA_CONTROL_REGISTER_FINISHED, it will send a extra traffic to
destination and cause migration to fail.

Since there's no existing subroutine to indicate whether it's migrated
by RDMA or not, and RDMA is not compatible with multifd, we use
migrate_multifd() here.

Fixes: 294e5a4034 ("multifd: Only flush once each full round of memory")
Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
---
 migration/ram.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c
index 9040d66e61..89ae28e21a 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1399,7 +1399,8 @@ static int find_dirty_block(RAMState *rs, PageSearchStatus *pss)
         pss->page = 0;
         pss->block = QLIST_NEXT_RCU(pss->block, next);
         if (!pss->block) {
-            if (!migrate_multifd_flush_after_each_section()) {
+            if (migrate_multifd() &&
+                !migrate_multifd_flush_after_each_section()) {
                 QEMUFile *f = rs->pss[RAM_CHANNEL_PRECOPY].pss_channel;
                 int ret = multifd_send_sync_main(f);
                 if (ret < 0) {
-- 
2.31.1


