Two x86_64 UEFI computers (different CPUs and firmware OEMs) won't
boot this kernel.
On one computer, it reboots shortly after I see EFI stub: UEFI secure
On another computer, I just get a hang with an underscore and it never recovers.
kernel-4.15.0-0.rc8.git1.1.fc28.x86_64 works fine on both.