diff --git a/arch/x86_64/cpu_ctrl.S b/arch/x86_64/cpu_ctrl.S
new file mode 100644
index 0000000..383afca
--- /dev/null
+++ b/arch/x86_64/cpu_ctrl.S
@@ -0,0 +1,8 @@
+
+	.global ml_halt_cpu
+	.type ml_halt_cpu, @function
+
+ml_halt_cpu:
+1:	cli
+	hlt
+	jmp 1b
diff --git a/arch/x86_64/include/socks/machine/cpu.h b/arch/x86_64/include/socks/machine/cpu.h
index dfe5bba..ab088b7 100644
--- a/arch/x86_64/include/socks/machine/cpu.h
+++ b/arch/x86_64/include/socks/machine/cpu.h
@@ -3,7 +3,6 @@
 
 #include <arch/gdt.h>
 
-#define ml_halt_cpu() asm volatile("cli;hlt")
 
 typedef struct ml_cpu_block {
 	struct gdt c_gdt;
@@ -15,4 +14,7 @@ extern int ml_init_bootcpu(void);
 extern int ml_cpu_block_init(ml_cpu_block *p);
 extern int ml_cpu_block_use(ml_cpu_block *p);
 
+/* defined in cpu_ctrl.S */
+extern void ml_halt_cpu(void);
+
 #endif