More info here:
http://jtomaschke.blogspot.com/2009/02/plan9-ac97-driver-bug.html

This is based on mason's contrib ac97.tgz.  I placed my code above the
if/elseif to provide it with an initial state in case both tests fail.

After this, kvm -soundhw ac97 gave me audio in my virtual environment.

/james