Hi,
I noticed that some of my contributions to Rust Hypervisor Firmware could be helpful for the coreboot EFI working group. So I would like to introduce it.
Rust Hypervisor Firmware (https://github.com/cloud-hypervisor/rust-hypervisor-firmware) is firmware written in Rust with a minimal EFI compatible layer. It is a part of the Cloud Hypervisor project and was created for booting Linux on the VMMs. I added the coreboot feature to the firmware to use the binary as a coreboot payload. I think this firmware would be a good start point if re-implementing UEFI without EDK2 because it provides only required functions to boot OS, but it is compatible enough to boot Windows10 on specific environments.
The coreboot specific code is here: https://github.com/cloud-hypervisor/rust-hypervisor-firmware/blob/main/src/c... It just parses the coreboot information table to provide e820 compatible information.
I hope this is helpful.
Akira Moroo