debian jessie as kvm guest high cpu load

Hi

I was wondering about the high cpu load of my debian jessie kvm guests.

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+    COMMAND
 18 root 20 0     S           11,0      50:10.35 ksoftirqd/2
 28 root 20 0     S           11,0      49:45.90 ksoftirqd/4
 13 root 20 0     S           10,1      51:25.18 ksoftirqd/1
 23 root 20 0     S           10,1      55:42.26 ksoftirqd/3
 33 root 20 0     S           8,3       43:12.53 ksoftirqd/5
 3 root 20 0      S           7,4       43:19.93 ksoftirqd/0

The more load my kvm guest had the more cpu time was allocated by the kernel.
I was using 3.16.0-4-amd64.

My hostmachines were, ubuntu 14.04 and archlinux. Both same issue.

Simple solution was to install backports kernel 4.2.0-0.bpo.1-amd64 oder compile fresh vanilla kernel via make localyesconfig.

Seems to be a debian kernel bug.

Have fun!