Xen boot path with host secure boot enabled

Let’s discuss about how best to boot a Xen system in the use case of host Secure Boot.

• Which path to take? multiboot2 ? chainloading ? new grub2 commands? (xen_hypervisor / xen_module) ? UKI or not? how to deal with arguments/command line?
• which patch are needed? (in grub2 and Xen)
• What’s been done and what needs to be done next?
• Let’s put apart the lockdown topic (to discuss it in another design session)