FC6 xen: CPU frequency scaling unsupported

[D. Hugh Redelmeier]

I just installed FC6 x86_64 on my desktop.  Previously it was running
FC5.  The installation was not an update but /home is shared.

I now get the message "CPU frequency scaling unsupported" from the
Gnome CPU Frequency Scaling Monitor applet.

Google got me to
http://www.redhat.com/archives/fedora-list/2006-October/msg03005.html
but this turns out to be unrelated.

==> It appears that a xen kernel does not support frequency scaling.

Since I have a fat desktop machine, I chose all sorts of options when
I installed, including xen.  So the kernel I had was kernel-xen for
x86_64.  When I installed and booted the non-xen kernel for x86_64,
frequency scaling worked again.

Too bad googling did not help me.  I'm posting this so that the next
person to experience this will know what is going on.

Any idea why the xen kernel cannot scale the frequency of the CPU?
This is obviously a waste of power.