fglrx hangs when using Xen

[Hans van Zijst]

Hi,

Here at work I use a Dell Optiplex with an ATI Radeon HD 2400 XT
dualhead videocard, RV610 chipset, with 2 monitors. I created a nice
dualhead setup in X.org, using the proprietary fglrx driver. All of this
in Debian Lenny. So far it has worked reasonably fine.

However, I want to use this machine to run Xen, so I can use both a
Windoze install and Linux at the same time. I installed the Xen 3.2.1
hypervisor, but since then the X.org dualhead setup causes problems: as
soon as I start X, the entire PC hangs. Both screens switch off. No
reaction to ping, no keyboard leds, nothing. Only way out is to pull the
plug. When I boot into the non-Xen kernel, everything works fine again.
There are no errors in Xorg.0.log.

What I want to do is use 1 screen for my Windows DomU and the other for
a Linux DomU.

Does anyone recognise this? And more important, does anyone know of a
solution?

Kind regards,

Hans