migration: report an error giving the failed field

When a field fails to load (typically due to a limit
check, or a call to a get/put) report the device and field
to give an indication of the cause.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

migration/vmstate.c

@@ -130,6 +130,8 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd,
                 }
                 if (ret < 0) {
                     qemu_file_set_error(f, ret);
+                    error_report("Failed to load %s:%s", vmsd->name,
+                                 field->name);
                     trace_vmstate_load_field_error(field->name, ret);
                     return ret;
                 }