checkvm hangs on EC2

Running an Ubuntu 10.10 UEC VM on Amazon EC2 (ami-b7e4b4f2), installing the open-vm-tools package (2010.06.16-268169-3ubuntu1) hangs apt-get when running the /etc/init.d/open-vm-tools script. (Yes, it's pointless to install open-vm-tools on EC2 or Xen, but hanging seems too severe a punishment.)

The script runs vmware-checkvm to see whether it's running on VMware. This program tries to read from a magic IO port 0x5658, but this just hangs when running on EC2.

Assuming the problem is Xen and not EC2 specifically, either the init script or vmware-checkvm.c could test for the existence of the /proc/xen directory before attempting the IO port read. Or is there a safer way than running vmware-checkvm to check that the system is running on VMware?

(See https://bugs.launchpad.net/ubuntu/+source/open-vm-tools/+bug/737668 for the bug I filed against Ubuntu.)