There is a new 9vx, version 0.11.

http://swtch.com/9vx/

It includes the #S device I mentioned earlier,
it includes the previously-missing darwin-asm.S,
and it fixes the cpu-chewing bug on OS X.

The sources are at the usual (other) place

http://pdos.csail.mit.edu/~baford/vm/

Russ