[v2,10/12] savevm: update error reporting of qemu_savevm_state() and related functions

diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 913f49f..0e3f30a 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -72,9 +72,10 @@  void qemu_announce_self(void);
 
 bool qemu_savevm_state_blocked(Error **errp);
 void qemu_savevm_state_begin(QEMUFile *f,
-                             const MigrationParams *params);
-int qemu_savevm_state_iterate(QEMUFile *f);
-void qemu_savevm_state_complete(QEMUFile *f);
+                             const MigrationParams *params,
+                             Error **errp);
+int qemu_savevm_state_iterate(QEMUFile *f, Error **errp);
+void qemu_savevm_state_complete(QEMUFile *f, Error **errp);
 void qemu_savevm_state_cancel(void);
 uint64_t qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size);
 void qemu_loadvm_state(QEMUFile *f, Error **errp);
diff --git a/migration.c b/migration.c
index 0279911..15ecd3f 100644
--- a/migration.c
+++ b/migration.c
@@ -508,7 +508,7 @@  static void *migration_thread(void *opaque)
     bool old_vm_running = false;
 
     DPRINTF("beginning savevm\n");
-    qemu_savevm_state_begin(s->file, &s->params);
+    qemu_savevm_state_begin(s->file, &s->params, NULL);
 
     while (s->state == MIG_STATE_ACTIVE) {
         int64_t current_time;
@@ -519,7 +519,7 @@  static void *migration_thread(void *opaque)
             pending_size = qemu_savevm_state_pending(s->file, max_size);
             DPRINTF("pending size %lu max %lu\n", pending_size, max_size);
             if (pending_size && pending_size >= max_size) {
-                qemu_savevm_state_iterate(s->file);
+                qemu_savevm_state_iterate(s->file, NULL);
             } else {
                 DPRINTF("done iterating\n");
                 qemu_mutex_lock_iothread();
@@ -528,7 +528,7 @@  static void *migration_thread(void *opaque)
                 old_vm_running = runstate_is_running();
                 vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
                 qemu_file_set_rate_limit(s->file, INT_MAX);
-                qemu_savevm_state_complete(s->file);
+                qemu_savevm_state_complete(s->file, NULL);
                 qemu_mutex_unlock_iothread();
                 if (!qemu_file_get_error(s->file)) {
                     migrate_finish_set_state(s, MIG_STATE_COMPLETED);
diff --git a/savevm.c b/savevm.c
index 6458621..749d49d 100644
--- a/savevm.c
+++ b/savevm.c
@@ -1795,7 +1795,8 @@  bool qemu_savevm_state_blocked(Error **errp)
 }
 
 void qemu_savevm_state_begin(QEMUFile *f,
-                             const MigrationParams *params)
+                             const MigrationParams *params,
+                             Error **errp)
 {
     SaveStateEntry *se;
     int ret;
@@ -1836,6 +1837,7 @@  void qemu_savevm_state_begin(QEMUFile *f,
         ret = se->ops->save_live_setup(f, se->opaque);
         if (ret < 0) {
             qemu_file_set_error(f, ret);
+            error_setg_errno(errp, -ret, "Failed to begin vmstate save");
             break;
         }
     }
@@ -1847,7 +1849,7 @@  void qemu_savevm_state_begin(QEMUFile *f,
  *   0 : We haven't finished, caller have to go again
  *   1 : We have finished, we can go to complete phase
  */
-int qemu_savevm_state_iterate(QEMUFile *f)
+int qemu_savevm_state_iterate(QEMUFile *f, Error **errp)
 {
     SaveStateEntry *se;
     int ret = 1;
@@ -1874,6 +1876,7 @@  int qemu_savevm_state_iterate(QEMUFile *f)
 
         if (ret < 0) {
             qemu_file_set_error(f, ret);
+            error_setg_errno(errp, -ret, "Failed to iterate vmstate save");
         }
         if (ret <= 0) {
             /* Do not proceed to the next vmstate before this one reported
@@ -1886,7 +1889,7 @@  int qemu_savevm_state_iterate(QEMUFile *f)
     return ret;
 }
 
-void qemu_savevm_state_complete(QEMUFile *f)
+void qemu_savevm_state_complete(QEMUFile *f, Error **errp)
 {
     SaveStateEntry *se;
     int ret;
@@ -1911,6 +1914,7 @@  void qemu_savevm_state_complete(QEMUFile *f)
         trace_savevm_section_end(se->section_id);
         if (ret < 0) {
             qemu_file_set_error(f, ret);
+            error_setg_errno(errp, -ret, "Failed to complete vmstate save");
             return;
         }
     }
@@ -1972,37 +1976,33 @@  void qemu_savevm_state_cancel(void)
     }
 }
 
-static int qemu_savevm_state(QEMUFile *f)
+static void qemu_savevm_state(QEMUFile *f, Error **errp)
 {
-    int ret;
     MigrationParams params = {
         .blk = 0,
         .shared = 0
     };
 
-    if (qemu_savevm_state_blocked(NULL)) {
-        return -EINVAL;
+    if (qemu_savevm_state_blocked(errp)) {
+        return;
     }
 
     qemu_mutex_unlock_iothread();
-    qemu_savevm_state_begin(f, &params);
+    qemu_savevm_state_begin(f, &params, errp);
     qemu_mutex_lock_iothread();
 
     while (qemu_file_get_error(f) == 0) {
-        if (qemu_savevm_state_iterate(f) > 0) {
+        if (qemu_savevm_state_iterate(f, errp) > 0) {
             break;
         }
     }
 
-    ret = qemu_file_get_error(f);
-    if (ret == 0) {
-        qemu_savevm_state_complete(f);
-        ret = qemu_file_get_error(f);
+    if (!qemu_file_get_error(f)) {
+        qemu_savevm_state_complete(f, errp);
     }
-    if (ret != 0) {
+    if (qemu_file_get_error(f)) {
         qemu_savevm_state_cancel();
     }
-    return ret;
 }
 
 static int qemu_save_device_state(QEMUFile *f)
@@ -2358,7 +2358,6 @@  void do_savevm(Monitor *mon, const QDict *qdict)
 {
     BlockDriverState *bs, *bs1;
     QEMUSnapshotInfo sn1, *sn = &sn1, old_sn1, *old_sn = &old_sn1;
-    int ret;
     QEMUFile *f;
     int saved_vm_running;
     uint64_t vm_state_size;
@@ -2423,11 +2422,12 @@  void do_savevm(Monitor *mon, const QDict *qdict)
         monitor_printf(mon, "Could not open VM state file\n");
         goto the_end;
     }
-    ret = qemu_savevm_state(f);
+    qemu_savevm_state(f, &local_err);
     vm_state_size = qemu_ftell(f);
     qemu_fclose(f);
-    if (ret < 0) {
-        monitor_printf(mon, "Error %d while writing VM\n", ret);
+    if (error_is_set(&local_err)) {
+        qerror_report_err(local_err);
+        error_free(local_err);
         goto the_end;
     }