Grub cause problems while loading xen.efi on many machines, mostly
because xen.efi support loading dom0 kernel and initramfs only via EFI
services and xen.efi needs to be loaded through them too. But grub in
some cases uses own filesystem handling code instead, leaving xen.efi
without dom0 kernel.
This should improve when xen.efi will get multiboot2 support (Xen 4.10?)
- then grub could load dom0 kernel and initramfs too and pass them to
xen.efi.
For now, bypass grub and launch xen.efi directly. This have unfortunate
effect of not having boot menu, so choose the most universal option:
verbose, with all known workarounds for UEFI applied.
FixesQubesOS/qubes-issues#3505
ae8b332ca8