monitor: Fix find_device_state() for IDs containing slashes

Recent commit 6952026120 "monitor: Tidy up find_device_state()"
assumed the function's argument is "the device's ID or QOM path" (as
documented for device_del).  It's actually either an absolute QOM
path, or a QOM path relative to /machine/peripheral/.  Such a relative
path is a device ID when it doesn't contain a slash.  When it does,
the function now always fails.  Broke iotest 200, which uses relative
path "vda/virtio-backend".

It fails because object_resolve_path_component() resolves just one
component, not a relative path.

The obvious function to resolve relative paths is
object_resolve_path().  It picks a parent automatically.  Too much
magic, we want to specify the parent.  Create new
object_resolve_path_at() for that, and use it in find_device_state().

Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20211019085711.86377-1-armbru@redhat.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/qom/object.h b/include/qom/object.h
index faae0d841f..fae096f51c 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -1544,6 +1544,18 @@ Object *object_resolve_path_type(const char *path, const char *typename,
                                  bool *ambiguous);
 
 /**
+ * object_resolve_path_at:
+ * @parent: the object in which to resolve the path
+ * @path: the path to resolve
+ *
+ * This is like object_resolve_path(), except paths not starting with
+ * a slash are relative to @parent.
+ *
+ * Returns: The resolved object or NULL on path lookup failure.
+ */
+Object *object_resolve_path_at(Object *parent, const char *path);
+
+/**
  * object_resolve_path_component:
  * @parent: the object in which to resolve the path
  * @part: the component to resolve.