ahci timeout on Parallels Desktop 6

[David Evans]

On a 9.0-RC1 system I am seeing ahci timeout messages like this:

ahcich3: Timeout on slot 2 port 0
ahcich3: is 00000001 cs 00000000 ss 00000000 rs 00000006 tfd \
   40 serr 00000000 cmd 1000c213
ahcich0: Timeout on slot 24 port 0
ahcich0: is 00000001 cs 00000000 ss 00000000 rs 01800000 tfd \
   40 serr 00000000 cmd 1000d813

on VM on Parallels Desktop  6.0.12106 for OS X

The messages appear to be quite benign, and the system resumes after a 
couple of seconds.

But on another system, 10.0-CURRENT as of a few days ago with a ZFS
filesystem on a SATA disk, when a ahci timeout message appears the system
freezes, although it is possible to switch consoles with alt-Fx 

Are there any timeout values I could possibly increase to make these
messages go away?

Regarding ZFS, yes I know it makes no sense to run it on a virtual disk.
I'm doing it for fun and educational value as well as testing 10-CURRENT
out.