FreeBSD not seeing disk device resize

I debated which group to mail ( zfs, xen, of fs ) and decided to start here.

The setup : FreeBSD VM running on Xen host.  Xen disk xbd4 set up with zfs ( zpool
create PoolName /dev/xbd4 ).

Works fine.

geom disk list sees it just fine also.

If I grow the disk in Xen, I cannot see the change live in FreeBSD.  Camcontrol sees
none of the devices except the DVD drive.  Geom sees everything but the kick geom
trick of "true > /dev/xbd4" fails.

A reboot and geom now sees the new size and I can expand the pool as normal.

I had remembered seeing a "rescan" option in bsdinstall so for giggles I went in
and tried that and whatever it does didn't work either. 

This isn't a showstopper but its an annoyance.

  -Tom

-- 
 --------------------------------------------------------------------
 - Tom Arnold           -  "...is it a virus, a drug, or a religion?"  
 - Sysabend Caretaker   -    Juanita Shrugs. "What's the difference?"
 ------------------------       -- Neal Stephenson,  Snow Crash