qgraph: allow extra_device_opts on contains nodes

Allow choosing the bus that the device will be placed on, in case
the machine has more than one.  Otherwise, the bus may not match
the base address of the controller we attach it to.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

tests/qos-test.c

@@ -340,7 +340,8 @@ static void walk_path(QOSGraphNode *orig_path, int len)
     char **path_vec = g_new0(char *, (QOS_PATH_MAX_ELEMENT_SIZE * 2));
     int path_vec_size = 0;
 
-    char *after_cmd = NULL, *before_cmd = NULL, *after_device = NULL;
+    char *after_cmd, *before_cmd, *after_device;
+    GString *after_device_str = g_string_new("");
     char *node_name = orig_path->name, *path_str;
 
     GString *cmd_line = g_string_new("");
@@ -363,9 +364,8 @@ static void walk_path(QOSGraphNode *orig_path, int len)
         /* append node command line + previous edge command line */
         if (path->command_line && etype == QEDGE_CONSUMED_BY) {
             g_string_append(cmd_line, path->command_line);
-            if (after_device) {
-                g_string_append(cmd_line, after_device);
-            }
+            g_string_append(cmd_line, after_device_str->str);
+            g_string_truncate(after_device_str, 0);
         }
 
         path_vec[path_vec_size++] = qos_graph_edge_get_name(path->path_edge);
@@ -382,12 +382,15 @@ static void walk_path(QOSGraphNode *orig_path, int len)
         if (after_cmd) {
             g_string_append(cmd_line2, after_cmd);
         }
+        if (after_device) {
+            g_string_append(after_device_str, after_device);
+        }
     }
 
     path_vec[path_vec_size++] = NULL;
-    if (after_device) {
-        g_string_append(cmd_line, after_device);
-    }
+    g_string_append(cmd_line, after_device_str->str);
+    g_string_free(after_device_str, true);
+
     g_string_append(cmd_line, cmd_line2->str);
     g_string_free(cmd_line2, true);