Normally, when you start a Xen domU virtual machine with sdl=1 in his configuration file in Xen, a window pops up with the screen framebuffer of the virtual machine, so you can control it with mouse and keyboard (just like VNC - also there is a "vnc=1" option in Xen). 

Note: If you close this window, the virtual machine is destroyed (hard shutdown).

Reproducible: Always

Steps to Reproduce:
1. Login normally in KDE
2. Create a Xen config file with "sdl = 1" in it. Let's call it "myxen.txt"
Example:
    name = "myxen"
    builder = "hvm"
    memory = 128
    vcpus = 1
    disk = [ ]
    vnc = 0
    sdl = 1

3. Start the domU with "xl create myxen.txt"
3. See a black screen. Done.
Actual Results:  
- The screen goes black, with a freezed mouse cursor and a static "_" in the top left corner of the screen. I must press Ctrl + Alt + F1 then Ctrl + Alt + F7 to bring KDE back.
- Sometimes it swaps to tty1 (sometimes tty2), showing a login prompt. I must press Ctrl + Alt + F7 to bring KDE back.
- My SDL window is not created. VM does not start.

The VM can't start, since the SDL window have not been created.
xl says: "libxl: error: libxl_dm.c:1245:libxl__destroy_device_model: Device Model already exited"

Expected Results:  
Create a SDL window so I can view/control the Virtual Machine.

Hardware tested:
MB: Striker II Formula
CPU: Core 2 Quad Q9650
VGA: Quadro FX580 (with Nouveau driver)

MB: G31-based motherboard (don't know the manufacturer)
CPU: Pentuim D E5300
VGA: GeForce 9800GT (tested both with nvidia and nouveau drivers)