PVCLOCK_SYSTEM_TIME_ENABLE
if (vcpu->vc_pvclock_system_gpa & PVCLOCK_SYSTEM_TIME_ENABLE) {
wrmsr(KVM_MSR_SYSTEM_TIME, pa | PVCLOCK_SYSTEM_TIME_ENABLE);
wrmsr(KVM_MSR_SYSTEM_TIME, pa & ~PVCLOCK_SYSTEM_TIME_ENABLE);
wrmsr(KVM_MSR_SYSTEM_TIME, pa | PVCLOCK_SYSTEM_TIME_ENABLE);