1 files changed, 20 insertions, 12 deletions

diff --git a/migration/multifd.c b/migration/multifd.c
index 4f973d70e0..ab73d6d984 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -252,9 +252,8 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
     p->packet_num = be64_to_cpu(packet->packet_num);
     p->packets_recved++;
 
-    if (!(p->flags & MULTIFD_FLAG_SYNC)) {
-        ret = multifd_ram_unfill_packet(p, errp);
-    }
+    /* Always unfill, old QEMUs (<9.0) send data along with SYNC */
+    ret = multifd_ram_unfill_packet(p, errp);
 
     trace_multifd_recv_unfill(p->id, p->packet_num, p->flags,
                               p->next_packet_size);
@@ -523,11 +522,13 @@ static int multifd_zero_copy_flush(QIOChannel *c)
     return ret;
 }
 
-int multifd_send_sync_main(void)
+int multifd_send_sync_main(MultiFDSyncReq req)
 {
     int i;
     bool flush_zero_copy;
 
+    assert(req != MULTIFD_SYNC_NONE);
+
     flush_zero_copy = migrate_zero_copy_send();
 
     for (i = 0; i < migrate_multifd_channels(); i++) {
@@ -543,8 +544,8 @@ int multifd_send_sync_main(void)
          * We should be the only user so far, so not possible to be set by
          * others concurrently.
          */
-        assert(qatomic_read(&p->pending_sync) == false);
-        qatomic_set(&p->pending_sync, true);
+        assert(qatomic_read(&p->pending_sync) == MULTIFD_SYNC_NONE);
+        qatomic_set(&p->pending_sync, req);
         qemu_sem_post(&p->sem);
     }
     for (i = 0; i < migrate_multifd_channels(); i++) {
@@ -635,14 +636,17 @@ static void *multifd_send_thread(void *opaque)
              */
             qatomic_store_release(&p->pending_job, false);
         } else {
+            MultiFDSyncReq req = qatomic_read(&p->pending_sync);
+
             /*
              * If not a normal job, must be a sync request.  Note that
              * pending_sync is a standalone flag (unlike pending_job), so
              * it doesn't require explicit memory barriers.
              */
-            assert(qatomic_read(&p->pending_sync));
+            assert(req != MULTIFD_SYNC_NONE);
 
-            if (use_packets) {
+            /* Only push the SYNC message if it involves a remote sync */
+            if (req == MULTIFD_SYNC_ALL) {
                 p->flags = MULTIFD_FLAG_SYNC;
                 multifd_send_fill_packet(p);
                 ret = qio_channel_write_all(p->c, (void *)p->packet,
@@ -654,7 +658,7 @@ static void *multifd_send_thread(void *opaque)
                 stat64_add(&mig_stats.multifd_bytes, p->packet_len);
             }
 
-            qatomic_set(&p->pending_sync, false);
+            qatomic_set(&p->pending_sync, MULTIFD_SYNC_NONE);
             qemu_sem_post(&p->sem_sync);
         }
     }
@@ -1151,9 +1155,13 @@ static void *multifd_recv_thread(void *opaque)
             flags = p->flags;
             /* recv methods don't know how to handle the SYNC flag */
             p->flags &= ~MULTIFD_FLAG_SYNC;
-            if (!(flags & MULTIFD_FLAG_SYNC)) {
-                has_data = p->normal_num || p->zero_num;
-            }
+
+            /*
+             * Even if it's a SYNC packet, this needs to be set
+             * because older QEMUs (<9.0) still send data along with
+             * the SYNC packet.
+             */
+            has_data = p->normal_num || p->zero_num;
             qemu_mutex_unlock(&p->mutex);
         } else {
             /*