Yes, I have been shuffling this struct around and didn't check the
layout. Will fix. I'll also try to make this struct usable for aarch64 too.
You may want to give a look to vcpu_guest_core_regs in public/arch-arm.h
Thanks, so the easiest way to be compatible with both it seems is to just declare all registers 64-bit wide. The userspace can then mask the unused bits if necessary.