guestid_cache
unsigned int guestid_cache;
#define guestid_cache(cpu) (cpu_data[cpu].guestid_cache)
unsigned long guestid = guestid_cache(cpu);
guestid_cache(cpu) = guestid;
(vcpu->arch.vzguestid[cpu] ^ guestid_cache(cpu)) &
vcpu->arch.vzguestid[cpu] = guestid_cache(cpu);
current_cpu_data.guestid_cache = GUESTID_FIRST_VERSION;