HYPERVISOR_hvm_op
error = HYPERVISOR_hvm_op(HVMOP_set_evtchn_upcall_vector, &vec);
error = HYPERVISOR_hvm_op(HVMOP_set_param, &xhp);
if (HYPERVISOR_hvm_op(HVMOP_set_param, &xhp) != 0)
error = HYPERVISOR_hvm_op(HVMOP_get_param, &xhv);