qom: qom-list-get

Using qom-list and qom-get to get all the nodes and property values in
a QOM tree can take multiple seconds because it requires 1000's of
individual QOM requests.  Some managers fetch the entire tree or a
large subset of it when starting a new VM, and this cost is a
substantial fraction of start up time.

Define the qom-list-get command, which fetches all the properties and
values for a list of paths.  This can be much faster than qom-list
plus qom-get.  When getting an entire QOM tree, I measured a 10x
speedup in elapsed time.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <1752248703-217318-2-git-send-email-steven.sistare@oracle.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

qapi/qom.json

@@ -47,6 +47,34 @@
             '*description': 'str',
             '*default-value': 'any' } }
 
+##
+# @ObjectPropertyValue:
+#
+# @name: the name of the property.
+#
+# @type: the type of the property, as described in `ObjectPropertyInfo`.
+#
+# @value: the value of the property.  Absent when the property cannot
+#     be read.
+#
+# Since 10.1
+##
+{ 'struct': 'ObjectPropertyValue',
+  'data': { 'name': 'str',
+            'type': 'str',
+            '*value': 'any' } }
+
+##
+# @ObjectPropertiesValues:
+#
+# @properties: a list of properties.
+#
+# Since 10.1
+##
+{ 'struct': 'ObjectPropertiesValues',
+  'data': { 'properties': [ 'ObjectPropertyValue' ] }}
+
+
 ##
 # @qom-list:
 #
@@ -124,6 +152,28 @@
   'returns': 'any',
   'allow-preconfig': true }
 
+##
+# @qom-list-get:
+#
+# List properties and their values for each object path in the input
+# list.
+#
+# @paths: The absolute or partial path for each object, as described
+#     in `qom-get`.
+#
+# Errors:
+#     - If any path is not valid or is ambiguous
+#
+# Returns: A list where each element is the result for the
+#     corresponding element of @paths.
+#
+# Since 10.1
+##
+{ 'command': 'qom-list-get',
+  'data': { 'paths': [ 'str' ] },
+  'returns': [ 'ObjectPropertiesValues' ],
+  'allow-preconfig': true }
+
 ##
 # @qom-set:
 #

qom/qom-qmp-cmds.c

@@ -69,6 +69,59 @@ ObjectPropertyInfoList *qmp_qom_list(const char *path, Error **errp)
     return props;
 }
 
+static void qom_list_add_property_value(Object *obj, ObjectProperty *prop,
+                                        ObjectPropertyValueList **props)
+{
+    ObjectPropertyValue *item = g_new0(ObjectPropertyValue, 1);
+
+    QAPI_LIST_PREPEND(*props, item);
+
+    item->name = g_strdup(prop->name);
+    item->type = g_strdup(prop->type);
+    item->value = object_property_get_qobject(obj, prop->name, NULL);
+}
+
+static ObjectPropertyValueList *qom_get_property_value_list(const char *path,
+                                                            Error **errp)
+{
+    Object *obj;
+    ObjectProperty *prop;
+    ObjectPropertyIterator iter;
+    ObjectPropertyValueList *props = NULL;
+
+    obj = qom_resolve_path(path, errp);
+    if (obj == NULL) {
+        return NULL;
+    }
+
+    object_property_iter_init(&iter, obj);
+    while ((prop = object_property_iter_next(&iter))) {
+        qom_list_add_property_value(obj, prop, &props);
+    }
+
+    return props;
+}
+
+ObjectPropertiesValuesList *qmp_qom_list_get(strList *paths, Error **errp)
+{
+    ObjectPropertiesValuesList *head = NULL, **tail = &head;
+    strList *path;
+
+    for (path = paths; path; path = path->next) {
+        ObjectPropertiesValues *item = g_new0(ObjectPropertiesValues, 1);
+
+        QAPI_LIST_APPEND(tail, item);
+
+        item->properties = qom_get_property_value_list(path->value, errp);
+        if (!item->properties) {
+            qapi_free_ObjectPropertiesValuesList(head);
+            return NULL;
+        }
+    }
+
+    return head;
+}
+
 void qmp_qom_set(const char *path, const char *property, QObject *value,
                  Error **errp)
 {