Hi, I have verified that I can reproduce a workign build of U-Boot as x86-64bit EFI payload for Qemu: I can boot it, interact with various filesystems of both real and emulated disks, etc.

Now I would like to build and boot it for a real board, still as EFI payload.

The docs/README.efi file states:

U-Boot is packaged up and loaded in its entirety by EFI. Once started, U-Boot changes to 32-bit mode (currently) and takes over the machine. You can use devices, boot a kernel, etc.

My test device is a a D4250WYK NUC with a 4th generation Core i5 Haswell processor. I tried booting it with an USB stick that I prepared and tested with qemu. The build is based on the qemu-x86_defconfig, plus the EFI settings needed for generating a 64 bit payload.

On qemu I can reach the U-Boot shell and run commands, however on the NUC it stops at the message "U-Boot EFI Payload", which is printed by the stub.

The stub is 64bit and the fact that I can see it printing anything makes me infer that the word-size should not be the problem.

But I suspect I'm skipping some necessary step.

For example: does "takes over the machine" mean that (apart from the settings specific to EFI) I should configure U-Boot like for a bare build?

Or should I include some binary blob, still like for bare mode?