On Thu, Dec 4, 2014 at 12:41 AM, Adam Williamson
Hi, folks. Talking to cmurf, our resident OS X dual boot expert, on
#fedora-qa, it's become clear that when we adopted the OS X dual boot
criterion a few weeks back, we didn't have a good understanding of the
current state of that code and particularly upstream grub's support for
booting OS X via UEFI. Basically it seems that booting OS X from grub
didn't work then and doesn't work now and we can't realistically fix it,
so we shouldn't have put that criterion in place because it's not
something we can actually viably achieve.
cmurf, roshi, kparal and I voted +1 to removing the criterion on that
basis. I'm hoping cmurf will be kind enough to look at the issue again
for the F22 cycle, in consultation with pjones if necessary, so we can
put a realistic requirement in place before we get into F22 Alphas.
If no-one has any objections, we'll make the removal formal ahead of
tomorrow's Go/No-Go meeting for 21. Thanks folks!
Gist: EFI GRUB still gets these legacy OS X boot options that were
designed to permit CSM-BIOS GRUB to EFI boot OS X. They don't work
from EFI GRUB though.
As far as I can tell there's no upstream bandwidth/interest in fixing
this; even if it means just suppressing the creation of the entries,
rather than chainloading the Apple bootloader. So I think the issue is
not a QA issue right now, but needs to be bounced back to desktop@ for
the Workstation WG to maybe use some recruitment influence if they
want to see this fixed.
A challenge with grub2-mkconfig creating an entry to chainload Apple's
boot.efi, is with recent on-disk format changes in OS X 10.10 since
this last October. It means os-prober will need to become aware that
the boot.efi it's looking for is now on an Apple Boot  partition.
I'm not sure what's involved in doing that work compared to just
suppressing the creation of entries that don't work anyway.
48465300-0000-11AA-AA11-00306543ECAC HFS+ partition type, no longer
used except for external/removable media, this is what os-prober looks
426F6F74-0000-11AA-AA11-00306543ECAC Apple Boot partition type, is
JHFS+ format, is where boot.efi is located
53746F72-6167-11AA-AA11-00306543ECAC Core Storage PV partition type,
OS X's version of LVM, the LV OS X is on could be encrypted but in any
case right now we can't mount the volume until we have Core Storage
support on linux.