[PATCH v2 1/2] migration: Fix rdma migration failed

[Li Zhijian]

Migration over RDMA failed since
commit: 294e5a4034 ("multifd: Only flush once each full round of memory")
with erors:
qemu-system-x86_64: rdma: Too many requests in this message 
(3638950032).Bailing.

migration 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(
RAM_SAVE_FLAG_MULTIFD_FLUSH) to destination and cause migration to fail
even though multifd is disabled.

This change make migrate_multifd_flush_after_each_section() return true
when multifd is disabled, that also means RAM_SAVE_FLAG_MULTIFD_FLUSH
will not be sent to destination any more when multifd is disabled.

Fixes: 294e5a4034 ("multifd: Only flush once each full round of memory")
CC: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
---

V2: put that check at the entry of migrate_multifd_flush_after_each_section() # 
Peter
---
 migration/options.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/migration/options.c b/migration/options.c
index 1d1e1321b0..327bcf2fbe 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -368,7 +368,7 @@ bool migrate_multifd_flush_after_each_section(void)
 {
     MigrationState *s = migrate_get_current();
 
-    return s->multifd_flush_after_each_section;
+    return !migrate_multifd() || s->multifd_flush_after_each_section;
 }
 
 bool migrate_postcopy(void)
-- 
2.31.1