a hvm is only running via hardware assisted virtualization if the guest is using the same ISA; a non-native guest is still "real virtualization", if all else is equal, isn't it? in that case, wouldn't the processor be the same thing as a "CPU emulator"? if not, how is it different?

I guess what I'm trying to say is maybe the distinction you're drawing isn't really as distinct as you think it is; if this project had virtualized devices and a kernel driving them instead of passing through syscalls, would that be real virtualization, assuming we're talking about a non-native guest ISA? don't vm guest drivers abstractly just pass through to syscalls / host drivers anyway? what if there was no OS and the user's code implemented those drivers? aren't virtualized devices "just setting up a datastructure and calling a function" too? if not, what are they?

like, do you see how this is really a spectrum or collection of system components with levels of virtualization?

CPU-only virtualization with syscall sandboxes is still more secure and useful than fancy chroot.