4.9-rc1 boot regression, ambiguous bisect result

[Dan Williams]

Hi,

I am currently unable to boot a Yoga 900 with latest mainline, but 4.8 boots.

The symptom is a reboot before the video console is available.

I bisected to commit 816e76129ed5 "efi: Allow drivers to reserve boot
services forever".  However, that commit is known to be broken.  The
proposed fix, commit 92dc33501bfb "x86/efi: Round EFI memmap
reservations to EFI_PAGE_SIZE", also exhibits the reboot problem.

During the bisect some of the stopping points landed on commits that
caused the boot process to hang rather than cause a reboot.  The
commits that resulted in a hang are marked "git bisect skip" in this
log: https://gist.github.com/djbw/1b501daa98192a42ae848f03bb59c30e

I'll try treating those hangs as bad bisect results and re-run the
full bisect tomorrow.  In the meantime I wonder if the bisect log
implicates a better regression candidate?