I did not remember that from when I used to use colinux.

The colinux home page also says:

To cooperatively share hardware with the host operating system, coLinux does not access I/O devices directly. Instead, it interfaces with emulated devices provided by the coLinux drivers in the host OS. For example, a regular file in Windows can be used as a block device in coLinux. All real hardware interrupts are transparently forwarded to the host OS, so this way the host OS's control of the real hardware is not being disturbed and thus it continues to run smoothly.

So just like UML, colinux hooks int 80h (or sysenter) and forwards the request to windows. Thus while it may make use of direct access to the MMU, most devices iirc are virtualized.