xen_vcpu_stolen
if (xen_vcpu_stolen(cpu)) {
PV_CALLEE_SAVE_REGS_THUNK(xen_vcpu_stolen);
pv_ops_lock.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
bool xen_vcpu_stolen(int vcpu);
bool xen_vcpu_stolen(int vcpu);