libxl: On ARM, reject future new passthrough modes too

This is most pleasantly done by also changing the if to a switch.

Suggested-by: Julien Grall <julien@xen.org>
CC: Julien Grall <julien@xen.org>
CC: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Release-acked-by: Juergen Gross <jgross@suse.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>

tools/libxl/libxl_arm.c

@@ -1203,9 +1203,15 @@ int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc,
         c_info->passthrough = LIBXL_PASSTHROUGH_SHARE_PT;
     }
 
-    if (c_info->passthrough == LIBXL_PASSTHROUGH_SYNC_PT) {
+    switch (c_info->passthrough) {
+    case LIBXL_PASSTHROUGH_DISABLED:
+    case LIBXL_PASSTHROUGH_SHARE_PT:
+        break;
+
+    default:
         LOGD(ERROR, domid,
-             "passthrough=\"sync_pt\" not supported on ARM\n");
+             "passthrough=\"%s\" not supported on ARM\n",
+             libxl_passthrough_to_string(c_info->passthrough));
         rc = ERROR_INVAL;
         goto out;
     }