How To Call ExitBootService through GRUB

I am working on a UEFI Based Hypervisor for Intel x86 platform. The GRUB is being used to load both the VMM and OS images, for reducing the complexity I am currently loading only one GPOS through GRUB and obviously the VMM. However due to some design issues, I don't want to use EFI Services within Hypervisor. During my research regarding this topic, I came across a post or comment which stated that GRUB can call the ExitBootService which will solve my issue. But there is no proper documentation about how to actually call ExitBootService through the GRUB. Would be really helpful if someone could guide me a little about calling ExitBootService through the GRUB.