[04/41] migration: print total downtime for final phase of migration

diff --git a/hmp.c b/hmp.c
index ba6fbd3..40b0c05 100644
--- a/hmp.c
+++ b/hmp.c
@@ -152,6 +152,10 @@  void hmp_info_migrate(Monitor *mon)
         monitor_printf(mon, "Migration status: %s\n", info->status);
         monitor_printf(mon, "total time: %" PRIu64 " milliseconds\n",
                        info->total_time);
+        if (info->has_downtime) {
+            monitor_printf(mon, "downtime: %" PRIu64 " milliseconds\n",
+                           info->downtime);
+        }
     }

     if (info->has_ram) {
diff --git a/migration.c b/migration.c
index 7a11026..1375e7e 100644
--- a/migration.c
+++ b/migration.c
@@ -195,6 +195,8 @@  MigrationInfo *qmp_query_migrate(Error **errp)
         info->has_status = true;
         info->status = g_strdup("completed");
         info->total_time = s->total_time;
+        info->has_downtime = true;
+        info->downtime = s->downtime;

         info->has_ram = true;
         info->ram = g_malloc0(sizeof(*info->ram));
@@ -329,9 +331,10 @@  static void migrate_fd_put_ready(void *opaque)
         migrate_fd_error(s);
     } else if (ret == 1) {
         int old_vm_running = runstate_is_running();
-        int64_t end_time;
+        int64_t start_time, end_time;

         DPRINTF("done iterating\n");
+        start_time = qemu_get_clock_ms(rt_clock);
         qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
         vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);

@@ -342,6 +345,7 @@  static void migrate_fd_put_ready(void *opaque)
         }
         end_time = qemu_get_clock_ms(rt_clock);
         s->total_time = end_time - s->total_time;
+        s->downtime = end_time - start_time;
         if (s->state != MIG_STATE_COMPLETED) {
             if (old_vm_running) {
                 vm_start();
diff --git a/migration.h b/migration.h
index a9852fc..3462917 100644
--- a/migration.h
+++ b/migration.h
@@ -40,6 +40,7 @@  struct MigrationState
     void *opaque;
     MigrationParams params;
     int64_t total_time;
+    int64_t downtime;
     bool enabled_capabilities[MIGRATION_CAPABILITY_MAX];
     int64_t xbzrle_cache_size;
 };
diff --git a/qapi-schema.json b/qapi-schema.json
index 14e4419..b5a4360 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -413,13 +413,18 @@ 
 #        If migration has ended, it returns the total migration
 #        time. (since 1.2)
 #
+# @downtime: #optional only present when migration finishes correctly
+#        total downtime in milliseconds for the guest.
+#        (since 1.3)
+#
 # Since: 0.14.0
 ##
 { 'type': 'MigrationInfo',
   'data': {'*status': 'str', '*ram': 'MigrationStats',
            '*disk': 'MigrationStats',
            '*xbzrle-cache': 'XBZRLECacheStats',
-           '*total-time': 'int'} }
+           '*total-time': 'int',
+           '*downtime': 'int'} }

 ##
 # @query-migrate
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 6e21ddb..37be613 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -2267,6 +2267,8 @@  The main json-object contains the following:
 - "total-time": total amount of ms since migration started.  If
                 migration has ended, it returns the total migration
 		 time (json-int)
+- "downtime": only present when migration has finished correctly
+                total amount in ms for downtime that happened (json-int)
 - "ram": only present if "status" is "active", it is a json-object with the
   following RAM information (in bytes):
          - "transferred": amount transferred (json-int)
@@ -2304,6 +2306,7 @@  Examples:
           "remaining":123,
           "total":246,
           "total-time":12345,
+          "downtime":12345,
           "duplicate":123,
           "normal":123,
           "normal-bytes":123456