On Fri, 11 Apr, at 11:03:13AM, H. Peter Anvin wrote: > On 04/11/2014 10:59 AM, Thomas Bächler wrote: > > EFI stub support is only missing for a 64 bit kernel on 32-bit firmware, > > on 64-bit kernels, EFI stub works as usual. > > --- > > > > Matt, I don't know if this help was intentionally discouraging, > > however, out of curiosity, I tested this with ovmf, and the > > kernel boots fine on 64-bit firmware bit with EFI stub, and on > > 32-bit firmware using efilinux. > > > > Documenting this properly is important for distribution kernels. > > We would want to support this on Arch, but not if it means > > introducing a regression for EFI stub users. > > > > arch/x86/Kconfig | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > > index 5b8ec0f..2bbbbb9 100644 > > --- a/arch/x86/Kconfig > > +++ b/arch/x86/Kconfig > > @@ -1529,8 +1529,8 @@ config EFI_MIXED > > mode. > > > > Note that it is not possible to boot a mixed-mode enabled > > - kernel via the EFI boot stub - a bootloader that supports > > - the EFI handover protocol must be used. > > + kernel via the EFI boot stub on 32-bit firmware - a bootloader > > + that supports the EFI handover protocol must be used. > > > > If unsure, say N. > > > > 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. -- 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/
