diff --git a/xen/arch/x86/arch.mk b/xen/arch/x86/arch.mk
index cb47d72991..258e459bec 100644
--- a/xen/arch/x86/arch.mk
+++ b/xen/arch/x86/arch.mk
@@ -17,7 +17,6 @@ $(call as-option-add,CFLAGS,CC,"rdrand %eax",-DHAVE_AS_RDRAND)
 $(call as-option-add,CFLAGS,CC,"rdfsbase %rax",-DHAVE_AS_FSGSBASE)
 $(call as-option-add,CFLAGS,CC,"xsaveopt (%rax)",-DHAVE_AS_XSAVEOPT)
 $(call as-option-add,CFLAGS,CC,"rdseed %eax",-DHAVE_AS_RDSEED)
-$(call as-option-add,CFLAGS,CC,"clac",-DHAVE_AS_CLAC_STAC)
 $(call as-option-add,CFLAGS,CC,"clwb (%rax)",-DHAVE_AS_CLWB)
 $(call as-option-add,CFLAGS,CC,".equ \"x\"$(comma)1",-DHAVE_AS_QUOTED_SYM)
 $(call as-option-add,CFLAGS,CC,"invpcid (%rax)$(comma)%rax",-DHAVE_AS_INVPCID)
diff --git a/xen/arch/x86/include/asm/asm-defns.h b/xen/arch/x86/include/asm/asm-defns.h
index 32d6b44910..ab653f3218 100644
--- a/xen/arch/x86/include/asm/asm-defns.h
+++ b/xen/arch/x86/include/asm/asm-defns.h
@@ -1,15 +1,5 @@
 #include <asm/page-bits.h>
 
-#ifndef HAVE_AS_CLAC_STAC
-.macro clac
-    .byte 0x0f, 0x01, 0xca
-.endm
-
-.macro stac
-    .byte 0x0f, 0x01, 0xcb
-.endm
-#endif
-
 .macro vmrun
     .byte 0x0f, 0x01, 0xd8
 .endm