[CentOS] xm console -- what should I get?

If I type "xm console 6", say (when I have a virtual machine 6 running), what should I get?

The documentation seems to indicate that I should get something that behaves like a telnet to a serial console.

What I actually get is a connection that might show me a couple of lines of output that do look like they belonged on the console, but doesn't seem to accept any input (except that it does exit on the documented escape character ^[).

These virtual systems show as running, and in fact with virt-viewer I can get a VNC console to them.

Dom0 and the guests are Centos 5.5 x64, running on Intel processors with modern virtualization support (turned on in the bios, and it looks like Xen found it from xm dmesg output).