In order to use the old bios emulator, you have to do nothing. (Default, if CONFIG_PCI_ROM_RUN is enabled)
In order to use yabel in your target, you need to add the following lines to your config: uses CONFIG_PCI_OPTION_ROM_RUN_YABEL default CONFIG_PCI_OPTION_ROM_RUN_YABEL=1
In order to use vm86 in your target, you need to add the following lines to your config: uses CONFIG_PCI_OPTION_ROM_RUN_VM86 default CONFIG_PCI_OPTION_ROM_RUN_VM86=1 Note: vm86 only works on platforms with _RAMBASE in the lower megabyte.
Can we get this added to the wiki somewhere? Maybe http://www.coreboot.org/Coreboot_Options ?