On Mon, 14 Apr, at 10:28:02AM, Thomas Bächler wrote: > Am 14.04.2014 09:15, schrieb Ingo Molnar: > >>> Right, it is really that it is not possible to boot a mixed-mode kernel > >>> on its non-native firmware using the stub, since the stub itself can > >>> only be one way or the other. > >> > >> Yeah, my help text was a bit... unhelpful. > >> > >> CONFIG_EFI_MIXED does not introduce a regression of any sort, you can > >> enable it without worrying about that. > >> > >> All the boot configurations that used to work will continue to work. > >> > >> What I meant to say was that it isn't possible to use the EFI mixed > >> *feature* (booting a 64-bit kernel with 32-bit firmware) with the > >> EFI boot stub - so you can build support into your kernel but > >> there's no way to make the CPU actually execute those code paths. > > > > Same goes for booting a 32-bit kernel on 64-bit firmware, right? > > > > It seems that isn't implemented: > > config EFI_MIXED > bool "EFI mixed-mode support" > depends on EFI_STUB && X86_64 >
Correct, since that would require translating 64-bit pointers from the firmware into 32-bit pointers for the kernel, which isn't as straight forward as the 32-bit firmware / 64-bit kernel case, i.e. ensure all allocations are < 4GB and truncate 64-bit pointers when they're passed to the firmware. That and the fact that no one has said "We really need support". -- Matt Fleming, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
