I'm certainly not an xnu specialist but from what I understand, you've basically got a BSD kernel (a "macrokernel") running in privileged mode that (roughly) ju

I'm certainly not an xnu specialist but from what I understand, you've basically got a BSD kernel (a "macrokernel") running in privileged mode that (roughly) just has a few services replaced by or connected to Mach ones. So I'm not really sure they get much portability benefit specifically from Mach versus "more traditional" kernels.