1 files changed, 16 insertions, 15 deletions

diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 53299b7a5e..f54f44d899 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -1198,6 +1198,11 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
 
     if (migrate_postcopy_preempt()) {
         /*
+         * The preempt channel is established in asynchronous way.  Wait
+         * for its completion.
+         */
+        qemu_sem_wait(&mis->postcopy_qemufile_dst_done);
+        /*
          * This thread needs to be created after the temp pages because
          * it'll fetch RAM_CHANNEL_POSTCOPY PostcopyTmpPage immediately.
          */
@@ -1544,6 +1549,7 @@ void postcopy_preempt_new_channel(MigrationIncomingState *mis, QEMUFile *file)
      */
     qemu_file_set_blocking(file, true);
     mis->postcopy_qemufile_dst = file;
+    qemu_sem_post(&mis->postcopy_qemufile_dst_done);
     trace_postcopy_preempt_new_channel();
 }
 
@@ -1612,14 +1618,21 @@ out:
     postcopy_preempt_send_channel_done(s, ioc, local_err);
 }
 
-/* Returns 0 if channel established, -1 for error. */
-int postcopy_preempt_wait_channel(MigrationState *s)
+/*
+ * This function will kick off an async task to establish the preempt
+ * channel, and wait until the connection setup completed.  Returns 0 if
+ * channel established, -1 for error.
+ */
+int postcopy_preempt_establish_channel(MigrationState *s)
 {
     /* If preempt not enabled, no need to wait */
     if (!migrate_postcopy_preempt()) {
         return 0;
     }
 
+    /* Kick off async task to establish preempt channel */
+    postcopy_preempt_setup(s);
+
     /*
      * We need the postcopy preempt channel to be established before
      * starting doing anything.
@@ -1629,22 +1642,10 @@ int postcopy_preempt_wait_channel(MigrationState *s)
     return s->postcopy_qemufile_src ? 0 : -1;
 }
 
-int postcopy_preempt_setup(MigrationState *s, Error **errp)
+void postcopy_preempt_setup(MigrationState *s)
 {
-    if (!migrate_postcopy_preempt()) {
-        return 0;
-    }
-
-    if (!migrate_multi_channels_is_allowed()) {
-        error_setg(errp, "Postcopy preempt is not supported as current "
-                   "migration stream does not support multi-channels.");
-        return -1;
-    }
-
     /* Kick an async task to connect */
     socket_send_channel_create(postcopy_preempt_send_channel_new, s);
-
-    return 0;
 }
 
 static void postcopy_pause_ram_fast_load(MigrationIncomingState *mis)