KVM: s390: bugfix for kvm/master (4.2)
Here is a bugfix for a regression that was introduced after 4.1
with the commit commit
fe2a35752671 ("KVM: s390: optimize round
trip time in request handling"). After lots of cpu hotplugs in the
guest (online/offline) sometimes a guest CPU did loop within host
KVM code. Reason was that PROG_REQUEST was set in the sie control
block, but no request was pending. This made commit
fe2a35752671
the suspect and changing that area to always reset PROG_REQUEST
did indeed fix the problem.
Special thanks to David Hildenbrand, who helped understanding the
exact sequence that led to the problem.