[kbumsik]

I think this title is misleading. Apple has open XNU for more than 10 years. And AFAIK this kernel does not include ARM compiling option, as the very first paragraph in the README:

> XNU runs on I386, X86_64

[LeoNatan25]

That’s what's newsworthy here—the code now includes the ARM codepaths as well.

[codehusker]

The README also mentions iOS, which AFAIK is only ARM.

There's also some ARM specific code: https://github.com/apple/darwin-xnu/tree/master/pexpert/arm

The Makefile also has ARM/ARM64 options.

[orbitur]

There are people on Twitter saying ARM64 is available on opensource.apple.com but I can't seem to find it.

This guy works on Foundation: https://twitter.com/Catfish_Man/status/913983607777116160