[Users] RHEL 5.x on oVirt - high CPU on KVM-host

Running both CentosOS 5.x and RHEL 5.x with all te latest patches gives a rather high CPU-load on the KVM-host, even when the machine is doing nothing. On the virtual server CPU-load is almost 0%. Installingen ktune and chaning the I/O scheduler to cfq gives a small change, CPU-load drops from apr. 26% to 19%. Adding devider=10 to the kernel parameters gives no improvement. Both nic and disk use virtio. It seems to be a kernel problem (there numerous thing to find on the internet) but anyone knows a solution? Winfried