Juergen,

as promised some more debug data. This is from c/s 22858 with Stephans 
debug patch (attached).
We get the following dump when the hypervisor crashes, note that the 
first lock is different from the second and subsequent ones:

(XEN) sched_credit.c, 572: prv: ffff831836df2970 &prv->lock: 
ffff831836df2970 prv->weight: 256 sdom->active_vcpu_count: 3 
sdom->weight: 256
(XEN) sched_credit.c, 572: prv: ffff830437ffa5e0 &prv->lock: 
ffff830437ffa5e0 prv->weight: 768 sdom->active_vcpu_count: 4 
sdom->weight: 256
(XEN) sched_credit.c, 572: prv: ffff830437ffa5e0 &prv->lock: 
ffff830437ffa5e0 prv->weight: 1024 sdom->active_vcpu_count: 5 
sdom->weight: 256
(XEN) sched_credit.c, 572: prv: ffff830437ffa5e0 &prv->lock: 
ffff830437ffa5e0 prv->weight: 1280 sdom->active_vcpu_count: 6 
sdom->weight: 256

....

Hope that gives you an idea. I attach the whole log for your reference.

Regards,
Andre

-- 
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany