migration: Add Error** argument to vmstate_save()

This will prepare ground for future changes adding an Error** argument
to qemu_savevm_state_setup().

Reviewed-by: Prasad Pandit <pjp@fedoraproject.org>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240320064911.545001-6-clg@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

migration/savevm.c

@@ -1009,11 +1009,10 @@ static void save_section_footer(QEMUFile *f, SaveStateEntry *se)
     }
 }
 
-static int vmstate_save(QEMUFile *f, SaveStateEntry *se, JSONWriter *vmdesc)
+static int vmstate_save(QEMUFile *f, SaveStateEntry *se, JSONWriter *vmdesc,
+                        Error **errp)
 {
     int ret;
-    Error *local_err = NULL;
-    MigrationState *s = migrate_get_current();
 
     if ((!se->ops || !se->ops->save_state) && !se->vmsd) {
         return 0;
@@ -1035,10 +1034,9 @@ static int vmstate_save(QEMUFile *f, SaveStateEntry *se, JSONWriter *vmdesc)
     if (!se->vmsd) {
         vmstate_save_old_style(f, se, vmdesc);
     } else {
-        ret = vmstate_save_state_with_err(f, se->vmsd, se->opaque, vmdesc, &local_err);
+        ret = vmstate_save_state_with_err(f, se->vmsd, se->opaque, vmdesc,
+                                          errp);
         if (ret) {
-            migrate_set_error(s, local_err);
-            error_report_err(local_err);
             return ret;
         }
     }
@@ -1325,8 +1323,10 @@ void qemu_savevm_state_setup(QEMUFile *f)
     trace_savevm_state_setup();
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
         if (se->vmsd && se->vmsd->early_setup) {
-            ret = vmstate_save(f, se, ms->vmdesc);
+            ret = vmstate_save(f, se, ms->vmdesc, &local_err);
             if (ret) {
+                migrate_set_error(ms, local_err);
+                error_report_err(local_err);
                 qemu_file_set_error(f, ret);
                 break;
             }
@@ -1542,6 +1542,7 @@ int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
     JSONWriter *vmdesc = ms->vmdesc;
     int vmdesc_len;
     SaveStateEntry *se;
+    Error *local_err = NULL;
     int ret;
 
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
@@ -1552,8 +1553,10 @@ int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
 
         start_ts_each = qemu_clock_get_us(QEMU_CLOCK_REALTIME);
 
-        ret = vmstate_save(f, se, vmdesc);
+        ret = vmstate_save(f, se, vmdesc, &local_err);
         if (ret) {
+            migrate_set_error(ms, local_err);
+            error_report_err(local_err);
             qemu_file_set_error(f, ret);
             return ret;
         }
@@ -1568,7 +1571,6 @@ int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
          * bdrv_activate_all() on the other end won't fail. */
         ret = bdrv_inactivate_all();
         if (ret) {
-            Error *local_err = NULL;
             error_setg(&local_err, "%s: bdrv_inactivate_all() failed (%d)",
                        __func__, ret);
             migrate_set_error(ms, local_err);
@@ -1764,6 +1766,8 @@ void qemu_savevm_live_state(QEMUFile *f)
 
 int qemu_save_device_state(QEMUFile *f)
 {
+    MigrationState *ms = migrate_get_current();
+    Error *local_err = NULL;
     SaveStateEntry *se;
 
     if (!migration_in_colo_state()) {
@@ -1778,8 +1782,10 @@ int qemu_save_device_state(QEMUFile *f)
         if (se->is_ram) {
             continue;
         }
-        ret = vmstate_save(f, se, NULL);
+        ret = vmstate_save(f, se, NULL, &local_err);
         if (ret) {
+            migrate_set_error(ms, local_err);
+            error_report_err(local_err);
             return ret;
         }
     }