def METHOD_NAME():
    """
    Format the new tmpfs disk in guest
    return: the formatted drive letter of the disk
    """
    test.log.info("Boot the guest to setup tmpfs disk")
    vm, session = _boot_guest_with_cpu_flag(cpu_model_flags)
    test.log.info("Format tmpfs disk")
    disk_size = params["image_size_" + params["tmpfs_image_name"]]
    disk_id = utils_disk.get_windows_disks_index(session, disk_size)[0]
    drive_letter = utils_disk.configure_empty_windows_disk(
        session, disk_id, disk_size)[0]
    vm.graceful_shutdown(timeout=timeout)
    return drive_letter