[PATCH 2/5] migration: Collect more timestamps during switchover

[Joao Martins]

In addition to the start of switchover (previously @downtime_start),
add other timestamps during saving of state and return path.

For precopy migration, it should be able to capture the principal
steps of switchover. Resume-side downtime is sadly only possible when
return path is enabled.

Signed-off-by: Joao Martins <joao.m.mart...@oracle.com>
---
 qapi/migration.json   | 16 +++++++++++++++-
 migration/migration.c |  5 +++++
 migration/savevm.c    |  2 ++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/qapi/migration.json b/qapi/migration.json
index b836cc881d33..2d91fbcb22ff 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -199,10 +199,24 @@
 # @start:Timestamp taken at the start of the switchover right before
 #        we stop the VM.
 #
+# @stop: Timestamp taken after stopping the VM.
+#
+# @precopy-iterable: Timestamp taken after copying all iterable state
+#                    in stop copy phase.
+#
+# @precopy-noniterable: Timestamp taken after copying all non iterable
+#                       state in stop copy phase.
+#
+# @resume-return-path: Timestamp taken after return path has finished
+#                      migration on destination. It is zero if
+#                      'return-path' is not enabled.
+#
 # Since: 8.2
 ##
 { 'enum': 'MigrationDowntime',
-  'data': [ 'start' ] }
+  'data': [ 'start', 'stop', 'precopy-iterable', 'precopy-noniterable',
+            'resume-return-path' ] }
+
 
 ##
 # @MigrationInfo:
diff --git a/migration/migration.c b/migration/migration.c
index dd955c61acc7..d06840024a1e 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2348,6 +2348,8 @@ static void migration_completion(MigrationState *s)
 
         ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
         trace_migration_completion_vm_stop(ret);
+        migration_set_timestamp(MIGRATION_DOWNTIME_STOP);
+
         if (ret >= 0) {
             ret = migration_maybe_pause(s, &current_active_state,
                                         MIGRATION_STATUS_DEVICE);
@@ -2401,6 +2403,7 @@ static void migration_completion(MigrationState *s)
         trace_migration_return_path_end_before();
         rp_error = await_return_path_close_on_source(s);
         trace_migration_return_path_end_after(rp_error);
+        migration_set_timestamp(MIGRATION_DOWNTIME_RESUME_RETURN_PATH);
         if (rp_error) {
             goto fail;
         }
@@ -3166,6 +3169,8 @@ static void *bg_migration_thread(void *opaque)
     if (vm_stop_force_state(RUN_STATE_PAUSED)) {
         goto fail;
     }
+    migration_set_timestamp(MIGRATION_DOWNTIME_STOP);
+
     /*
      * Put vCPUs in sync with shadow context structures, then
      * save their state to channel-buffer along with devices.
diff --git a/migration/savevm.c b/migration/savevm.c
index bb3e99194c60..e93701ff2393 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1468,6 +1468,7 @@ int qemu_savevm_state_complete_precopy_iterable(QEMUFile 
*f, bool in_postcopy)
         }
     }
 
+    migration_set_timestamp(MIGRATION_DOWNTIME_PRECOPY_ITERABLE);
     return 0;
 }
 
@@ -1524,6 +1525,7 @@ int 
qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
     json_writer_free(vmdesc);
     ms->vmdesc = NULL;
 
+    migration_set_timestamp(MIGRATION_DOWNTIME_PRECOPY_NONITERABLE);
     return 0;
 }
 
-- 
2.39.3