Comment # 2 on bug 957383 from Raymund Will

Yes, 'xen.efi' command-line options are currently not covered.

To rectify that, we need to add something there, but I'd like to propose
  GRUB_CMDLINE_XENEFI
to match the existing 'GRUB_CMDLINE_XEN' and to follow the example
of 'GRUB_USE_LINUXEFI', maybe prefixed with 'SUSE_' (if deemed
unavoidable).  And please retain that '$section' as last parameter.