Commit 7307f70c authored Jul 30, 2015 by Paolo Bonzini

Merge tag 'kvm-s390-master-20150730' of...

Merge tag 'kvm-s390-master-20150730' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into kvm-master

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 785dbef4 ("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 785dbef4
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.

parents 956325bd 586b7ccd

arch/s390/kvm/kvm-s390.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -1742,10 +1742,10 @@ static bool ibs_enabled(struct kvm_vcpu *vcpu)

	static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)		static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
	{		{
	if (!vcpu->requests)
	return 0;
	retry:		retry:
	kvm_s390_vcpu_request_handled(vcpu);		kvm_s390_vcpu_request_handled(vcpu);
			if (!vcpu->requests)
			return 0;
	/*		/*
	* We use MMU_RELOAD just to re-arm the ipte notifier for the		* We use MMU_RELOAD just to re-arm the ipte notifier for the
	* guest prefix page. gmap_ipte_notify will wait on the ptl lock.		* guest prefix page. gmap_ipte_notify will wait on the ptl lock.

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