Implement .bbclass for generating xl.cfg files

[lorc]

This is a pretty large task.

Is essence, what we need, is a piece of code (presumably Yocto .bbclass, or standalone tool) that will generate guest configuration files like domd.cfg or doma.cfg. Maybe together with partial device tree files. Check https://github.com/xen-troops/xen-dom-cfg-helper for reference.

High level requirements:

• Domain recipe (like domd.bb) makes inherit xt-domain-config and provides set of Yocto variables (like DOMAIN_DEVICES or DOMAIN_NAME or DOMAIN_PV_DEVICE for example).
• Based on aforementioned variables, xt-domain-config.bbclass generates domd.cfg file.
• It must generate functionally similar config that we already have in our products (both rcar and rpi5)
• It must support dom0less mode (see rpi5 product)
• It (or its part) must be able to generate partial device trees for domains
• It (or its part) must be able to generate system device tree used by Xen
• Configuration should be done in declarative style, i.e. with variables
• It must allow hooks for cases when imperative configuration (i.e. with Python or Bash script) is absolutely required. In other words, something like do_configure_append() must be supported
• Ideally, we want to get rid of shipped dom*.cfg and dom*.dts files

[klogg]

I really think what needs to be done prior to implementation is:

• create and overview existing tools out there (Xilinx, community, ...)
• do a short design session
• check how this is aligned with our other long-term tasks