v86/tests/kvm-unit-tests/lib/x86/asm/barrier.h

#ifndef _ASM_X86_BARRIER_H_
#define _ASM_X86_BARRIER_H_
/*
 * Copyright (C) 2016, Red Hat Inc, Alexander Gordeev <agordeev@redhat.com>
 *
 * This work is licensed under the terms of the GNU LGPL, version 2.
 */

#define mb()	asm volatile("mfence":::"memory")
#define rmb()	asm volatile("lfence":::"memory")
#define wmb()	asm volatile("sfence":::"memory")

#define smp_rmb()	barrier()
#define smp_wmb()	barrier()

/* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */
static inline void rep_nop(void)
{
	asm volatile("rep; nop" ::: "memory");
}

static inline void cpu_relax(void)
{
	rep_nop();
}

#endif