__cmpxchg64
(__typeof__(*(ptr)))__cmpxchg64((ptr), \
__res = __cmpxchg64((ptr), __old, __new); \
#define arch_cmpxchg64 __cmpxchg64
return __cmpxchg64(&pte->val, 0ULL, 0ULL) & VTD_PAGE_MASK;