[Qemu-devel] [PATCH RFC 2/2] qmp: New command qom-new

[Markus Armbruster <armbru@redhat.com>]

To create objects via QMP.

Test case:

$ upstream-qemu --enable-kvm -S -m 384 -vnc :0 -monitor stdio -chardev socket,id=qmp,path=test-qmp,server=on,wait=off -mon mode=control,chardev=qmp

Conversation on the qmp socket:
{"QMP": {"version": {"qemu": {"micro": 93, "minor": 0, "major": 1}, "package": ""}, "capabilities": []}}
{ "execute": "qmp_capabilities" }
{"return": {}}
{"execute":"qom-new","arguments":{"parent":"/xxx", "prop-name":"test-qmp-new", "type-name":"xxx"}}
{"error": {"class": "DeviceNotFound", "desc": "Device '/xxx' not found", "data": {"device": "/xxx"}}}
{"execute":"qom-new","arguments":{"parent":"/machine", "prop-name":"test-qmp-new", "type-name":"xxx"}}
{"error": {"class": "InvalidParameterValue", "desc": "Parameter 'type-name' expects a type name", "data": {"name": "type-name", "expected": "a type name"}}}
{"execute":"qom-new","arguments":{"parent":"/machine", "prop-name":"test-qmp-new", "type-name":"container"}}
{"return": "/machine/test-qmp-new"}
{"execute":"qom-list","arguments":{"path":"/machine"}}
{"return": [{"name": "test-qmp-new", "type": "child<container>"}, {"name": "i440fx", "type": "child<i440FX-pcihost>"}, {"name": "unattached", "type": "child<container>"}, {"name": "peripheral", "type": "child<container>"}, {"name": "peripheral-anon", "type": "child<container>"}]}

Note: qdev objects (subtype of TYPE_DEVICE) created with qom-new lack
additional magic performed by qdev_try_create(), and almost certainly
won't work.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 qapi-schema.json |   22 ++++++++++++++++++++++
 qmp-commands.hx  |    5 +++++
 qmp.c            |   27 +++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 0 deletions(-)

diff --git a/qapi-schema.json b/qapi-schema.json
index 2ca7195..ab9e68b 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1699,6 +1699,28 @@
   'returns': [ 'ObjectTypeInfo' ] }
 
 ##
+# qom-new:
+#
+# Create a new object
+#
+# @parent: the parent's path within the object model.  See @qom-get
+# for a description of paths.
+#
+# @prop-name: the name of the property to add to the parent.
+#
+# @type: the new object's type name
+#
+# Returns: The new object's canonical absolute path
+#
+# Since: 1.2
+#
+# Notes: This command is experimental and may change syntax in future releases.
+##
+{ 'command': 'qom-new',
+  'data': { 'parent': 'str', 'prop-name': 'str', 'type-name': 'str' },
+  'returns': 'str' }
+
+##
 # @migrate
 #
 # Migrates the current running guest to another Virtual Machine.
diff --git a/qmp-commands.hx b/qmp-commands.hx
index db980fa..53adda2 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -2142,3 +2142,8 @@ EQMP
         .args_type  = "implements:s?,abstract:b?",
         .mhandler.cmd_new = qmp_marshal_input_qom_list_types,
     },
+    {
+        .name       = "qom-new",
+        .args_type  = "parent:s,prop-name:s,type-name:s",
+        .mhandler.cmd_new = qmp_marshal_input_qom_new,
+    },
diff --git a/qmp.c b/qmp.c
index fee9fb2..cad5610 100644
--- a/qmp.c
+++ b/qmp.c
@@ -417,3 +417,30 @@ ObjectTypeInfoList *qmp_qom_list_types(bool has_implements,
 
     return ret;
 }
+
+char *qmp_qom_new(const char *parent, const char *prop_name,
+                  const char *type_name, Error **errp)
+{
+    Object *p, *obj;
+    Type type;
+
+    // TODO anything fancy with containger_get() needed?
+    p = object_resolve_path(parent, NULL);
+    if (!p) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, parent);
+        return NULL;
+    }
+
+    type = type_get_by_name(type_name);
+    if (!type) {
+        error_set(errp, QERR_INVALID_PARAMETER_VALUE,
+                  "type-name", "a type name");
+        return NULL;
+    }
+    obj = object_new_with_type(type);
+
+    // TODO bombs if p is an interface object; can this happen?
+    object_property_add_child(p, prop_name, obj, NULL);
+
+    return object_get_canonical_path(obj);
+}
-- 
1.7.6.5