libxl_dm: Add libxl__qemu_qmp_path()

... which generates the path to a QMP socket that libxl uses.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/libxl/libxl_dm.c

@@ -946,8 +946,8 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
     flexarray_append(dm_args, "-chardev");
     flexarray_append(dm_args,
                      GCSPRINTF("socket,id=libxl-cmd,"
-                                    "path=%s/qmp-libxl-%d,server,nowait",
-                                    libxl__run_dir_path(), guest_domid));
+                               "path=%s,server,nowait",
+                               libxl__qemu_qmp_path(gc, guest_domid)));
 
     flexarray_append(dm_args, "-no-shutdown");
     flexarray_append(dm_args, "-mon");

tools/libxl/libxl_internal.h

@@ -4424,6 +4424,10 @@ static inline bool libxl__string_is_default(char **s)
 
 _hidden int libxl__prepare_sockaddr_un(libxl__gc *gc, struct sockaddr_un *un,
                                        const char *path, const char *what);
+static inline const char *libxl__qemu_qmp_path(libxl__gc *gc, int domid)
+{
+    return GCSPRINTF("%s/qmp-libxl-%d", libxl__run_dir_path(), domid);
+}
 #endif
 
 /*