def METHOD_NAME(hv_flag):
    """
    Boot the guest, with param cpu_model_flags set to hv_flag
    param hv_flag: the hv flags to set to cpu
    return: the booted vm and a loggined session
    """
    params["cpu_model_flags"] = hv_flag
    params["start_vm"] = "yes"
    vm_name = params["main_vm"]
    env_process.preprocess_vm(test, params, env, vm_name)
    vm = env.get_vm(vm_name)
    vm.verify_alive()
    session = vm.wait_for_login(timeout=timeout)
    return (vm, session)