When booting Oracle VM Server on a system using a Radeon graphics adapter, and error may appear in the dmesg output similar to the following:

[drm:r100_ring_test] *ERROR* radeon: ring test failed
(scratch(0x15E4)=0xCAFEDEAD)
[drm:r100_cp_init] *ERROR* radeon: cp isn't working (-22).
radeon 0000:01:03.0: failed initializing CP (-22).
radeon 0000:01:03.0: Disabling GPU acceleration

Workaround: Ensure that the radeon module is loaded with the modeset parameter set to zero. To do this, add the following line in /etc/modprobe.conf:

options radeon modeset=0 

In order for the change to take effect, you should reboot the server.

Alternatively, the parameter radeon.modeset=0 can be appended to the boot options within /boot/grub/grub.conf. For example:

title Oracle VM Server (2.6.39-300.20.1.el5uek)
 root (hd0,0)
 kernel /xen.gz dom0_mem=987M
 module /vmlinuz-2.6.39-300.20.1.el5uek ro root=UUID=8d7687eb-fa2b-42ef-b411-044ba66cca6c 
     radeon.modeset=0
 module /initrd-2.6.39-300.20.1.el5uek.img

Bug 14376597