[Qemu-devel] [PATCH 4/5] migration: improve error reporting for hmp_loadvm

[Denis V. Lunev]

The patch adds Error ** parameter to load_vmstate call and fills error
inside. The caller after that properly reports error either through
monitor or via local stderr facility during VM start.

This helper will be usefull too for qmp_load_vmstate implementation.

Signed-off-by: Denis V. Lunev <address@hidden>
CC: Juan Quintela <address@hidden>
CC: Amit Shah <address@hidden>
CC: Markus Armbruster <address@hidden>
CC: Eric Blake <address@hidden>
---
 include/sysemu/sysemu.h |  2 +-
 migration/savevm.c      | 25 +++++++++++++------------
 monitor.c               |  7 ++++++-
 vl.c                    |  5 ++++-
 4 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 3bb8897..d9ccf45 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -78,7 +78,7 @@ void qemu_remove_exit_notifier(Notifier *notify);
 void qemu_add_machine_init_done_notifier(Notifier *notify);
 
 void hmp_savevm(Monitor *mon, const QDict *qdict);
-int load_vmstate(const char *name);
+int load_vmstate(const char *name, Error **errp);
 void hmp_delvm(Monitor *mon, const QDict *qdict);
 void hmp_info_snapshots(Monitor *mon, const QDict *qdict);
 
diff --git a/migration/savevm.c b/migration/savevm.c
index 90b6850..08c6c65 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2042,7 +2042,7 @@ void qmp_xen_save_devices_state(const char *filename, 
Error **errp)
     }
 }
 
-int load_vmstate(const char *name)
+int load_vmstate(const char *name, Error **errp)
 {
     BlockDriverState *bs, *bs_vm_state;
     QEMUSnapshotInfo sn;
@@ -2051,20 +2051,20 @@ int load_vmstate(const char *name)
     AioContext *aio_context;
 
     if (!bdrv_all_can_snapshot(&bs)) {
-        error_report("Device '%s' is writable but does not support snapshots.",
-                     bdrv_get_device_name(bs));
+        error_setg(errp, "Device '%s' is writable but does not support "
+                   "snapshots.", bdrv_get_device_name(bs));
         return -ENOTSUP;
     }
     ret = bdrv_all_find_snapshot(name, true, &bs);
     if (ret < 0) {
-        error_report("Device '%s' does not have the requested snapshot '%s'",
-                     bdrv_get_device_name(bs), name);
+        error_setg(errp, "Device '%s' does not have the requested "
+                   "snapshot '%s'", bdrv_get_device_name(bs), name);
         return ret;
     }
 
     bs_vm_state = bdrv_all_find_vmstate_bs();
     if (!bs_vm_state) {
-        error_report("No block device supports snapshots");
+        error_setg(errp, "No block device supports snapshots");
         return -ENOTSUP;
     }
     aio_context = bdrv_get_aio_context(bs);
@@ -2074,10 +2074,11 @@ int load_vmstate(const char *name)
     ret = bdrv_snapshot_find(bs_vm_state, &sn, name);
     aio_context_release(aio_context);
     if (ret < 0) {
+        error_setg_errno(errp, ret, "Snapshot '%s' not found", name);
         return ret;
     } else if (sn.vm_state_size == 0) {
-        error_report("This is a disk-only snapshot. Revert to it offline "
-            "using qemu-img.");
+        error_setg(errp, "This is a disk-only snapshot. Revert to it offline "
+                   "using qemu-img.");
         return -EINVAL;
     }
 
@@ -2086,15 +2087,15 @@ int load_vmstate(const char *name)
 
     ret = bdrv_all_goto_snapshot(name, &bs);
     if (ret < 0) {
-        error_report("Error %d while activating snapshot '%s' on '%s'",
-                     ret, name, bdrv_get_device_name(bs));
+        error_setg_errno(errp, ret, "Error while activating snapshot "
+                         "'%s' on '%s'", name, bdrv_get_device_name(bs));
         return ret;
     }
 
     /* restore the VM state */
     f = qemu_fopen_bdrv(bs_vm_state, 0);
     if (!f) {
-        error_report("Could not open VM state file");
+        error_setg(errp, "Could not open VM state file");
         return -EINVAL;
     }
 
@@ -2108,7 +2109,7 @@ int load_vmstate(const char *name)
 
     migration_incoming_state_destroy();
     if (ret < 0) {
-        error_report("Error %d while loading VM state", ret);
+        error_setg_errno(errp, ret, "Error while loading VM state");
         return ret;
     }
 
diff --git a/monitor.c b/monitor.c
index e4cf34e..1a0c932 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1739,10 +1739,15 @@ static void hmp_loadvm(Monitor *mon, const QDict *qdict)
 {
     int saved_vm_running  = runstate_is_running();
     const char *name = qdict_get_str(qdict, "name");
+    Error *local_err = NULL;
 
     vm_stop(RUN_STATE_RESTORE_VM);
 
-    if (load_vmstate(name) == 0 && saved_vm_running) {
+    if (load_vmstate(name, &local_err) < 0) {
+        monitor_printf(mon, "%s\n", error_get_pretty(local_err));
+        error_free(local_err);
+    }
+    if (saved_vm_running) {
         vm_start();
     }
 }
diff --git a/vl.c b/vl.c
index 7d993a5..9912366 100644
--- a/vl.c
+++ b/vl.c
@@ -4645,8 +4645,11 @@ int main(int argc, char **argv, char **envp)
     qemu_system_reset(VMRESET_SILENT);
     register_global_state();
     if (loadvm) {
-        if (load_vmstate(loadvm) < 0) {
+        Error *local_err = NULL;
+        if (load_vmstate(loadvm, &local_err) < 0) {
             autostart = 0;
+            error_report("%s", error_get_pretty(local_err));
+            error_free(local_err);
         }
     }
 
-- 
2.5.0