UEFI fastboot is so fast that there's no opportunity for the user to interrupt it to get to the firmware (nee BIOS) configuration; the only way to get to the firmware configuration is for the OS or bootloader to set a flag in nvram and then reboot. We need to sort out what the UI for doing this should be. We probably want to support doing this from the bootloader menu (so that if the OS fails to boot you can still recover). We may also want to support doing this from the shutdown menu, in case the bootloader menu is inaccessible (e.g., on a touchscreen-only device?) and/or for a better UI experience.