Index: sys/amd64/amd64/machdep.c
===================================================================
--- sys/amd64/amd64/machdep.c
+++ sys/amd64/amd64/machdep.c
@@ -2746,9 +2746,12 @@
 
 void	pagezero_std(void *addr);
 void	pagezero_erms(void *addr);
+void	pagezero_clzero(void *addr);
 DEFINE_IFUNC(, void , pagezero, (void *))
 {
 
+	if ((amd_extended_feature_extensions & AMDFEID_CLZERO) != 0)
+		return (pagezero_clzero);
 	return ((cpu_stdext_feature & CPUID_STDEXT_ERMS) != 0 ?
 	    pagezero_erms : pagezero_std);
 }
Index: sys/amd64/amd64/support.S
===================================================================
--- sys/amd64/amd64/support.S
+++ sys/amd64/amd64/support.S
@@ -66,6 +66,22 @@
 	ret
 END(pagezero_erms)
 
+ENTRY(pagezero_clzero)
+	PUSH_FRAME_POINTER
+	movq	%rdi,%rax
+	movl	cpu_clflush_line_size(%rip),%ecx
+	addq	$PAGE_SIZE,%rdi
+	sfence
+1:
+	clzero
+	addq	%rcx,%rax
+	cmpq	%rax,%rdi
+	jne	1b
+	sfence
+	POP_FRAME_POINTER
+	ret
+END(pagezero_clzero)
+
 /*
  * pagecopy(%rdi=from, %rsi=to)
  */