qapi: add query-machines command

This provides the same output as -M ? but in a structured way.
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>

qapi-schema.json

@@ -2194,3 +2194,31 @@
 # Since: 0.14.0
 ##
 { 'command': 'closefd', 'data': {'fdname': 'str'} }
+
+##
+# @MachineInfo:
+#
+# Information describing a machine.
+#
+# @name: the name of the machine
+#
+# @alias: #optional an alias for the machine name
+#
+# @default: #optional whether the machine is default
+#
+# Since: 1.2.0
+##
+{ 'type': 'MachineInfo',
+  'data': { 'name': 'str', '*alias': 'str',
+            '*is-default': 'bool' } }
+
+##
+# @query-machines:
+#
+# Return a list of supported machines
+#
+# Returns: a list of MachineInfo
+#
+# Since: 1.2.0
+##
+{ 'command': 'query-machines', 'returns': ['MachineInfo'] }

qmp-commands.hx

@@ -2224,3 +2224,9 @@ EQMP
         .mhandler.cmd_new = qmp_marshal_input_device_list_properties,
     },
 
+    {
+        .name       = "query-machines",
+        .args_type  = "",
+        .mhandler.cmd_new = qmp_marshal_input_query_machines,
+    },
+

vl.c

@@ -1213,6 +1213,37 @@ QEMUMachine *find_default_machine(void)
     return NULL;
 }
 
+MachineInfoList *qmp_query_machines(Error **errp)
+{
+    MachineInfoList *mach_list = NULL;
+    QEMUMachine *m;
+
+    for (m = first_machine; m; m = m->next) {
+        MachineInfoList *entry;
+        MachineInfo *info;
+
+        info = g_malloc0(sizeof(*info));
+        if (m->is_default) {
+            info->has_is_default = true;
+            info->is_default = true;
+        }
+
+        if (m->alias) {
+            info->has_alias = true;
+            info->alias = g_strdup(m->alias);
+        }
+
+        info->name = g_strdup(m->name);
+
+        entry = g_malloc0(sizeof(*entry));
+        entry->value = info;
+        entry->next = mach_list;
+        mach_list = entry;
+    }
+
+    return mach_list;
+}
+
 /***********************************************************/
 /* main execution loop */