Index: head/sys/amd64/amd64/support.S
===================================================================
--- head/sys/amd64/amd64/support.S
+++ head/sys/amd64/amd64/support.S
@@ -1807,7 +1807,7 @@
 1:	movq	PCPU(MDS_BUF), %rdi
 	movq	PCPU(MDS_BUF64), %rdx
 	vmovdqa64	%zmm0, PCPU(MDS_TMP)
-	vpxor	%zmm0, %zmm0, %zmm0
+	vpxord	%zmm0, %zmm0, %zmm0
 
 	lfence
 	vorpd	(%rdx), %zmm0, %zmm0
Index: head/sys/i386/i386/support.s
===================================================================
--- head/sys/i386/i386/support.s
+++ head/sys/i386/i386/support.s
@@ -611,7 +611,7 @@
 1:	movl	PCPU(MDS_BUF), %edi
 	movl	PCPU(MDS_BUF64), %edx
 	vmovdqa64	%zmm0, PCPU(MDS_TMP)
-	vpxor	%zmm0, %zmm0, %zmm0
+	vpxord	%zmm0, %zmm0, %zmm0
 
 	lfence
 	vorpd	(%edx), %zmm0, %zmm0