diff -up ./arch/x86/include/asm/sync_core.h.pti ./arch/x86/include/asm/sync_core.h
--- ./arch/x86/include/asm/sync_core.h.pti	2018-10-05 05:18:19.000000000 +0900
+++ ./arch/x86/include/asm/sync_core.h	2018-10-31 18:57:31.000000000 +0900
@@ -14,9 +14,11 @@
  */
 static inline void sync_core_before_usermode(void)
 {
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
 	/* With PTI, we unconditionally serialize before running user code. */
 	if (kaiser_active())
 		return;
+#endif
 	/*
 	 * Return from interrupt and NMI is done through iret, which is core
 	 * serializing.