Merge tag 'kvm-ppc-fixes-5.5-1' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc into kvm-master

PPC KVM fix for 5.5

- Fix a bug where we try to do an ultracall on a system without an
  ultravisor.

1 files changed, 18 insertions, 4 deletions

diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index 45634b3d2e0a..3fb54ec2cf3e 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -158,14 +158,28 @@ static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu)
 
 	tid = vcpu->run->s.regs.gprs[(vcpu->arch.sie_block->ipa & 0xf0) >> 4];
 	vcpu->stat.diagnose_9c++;
-	VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d", tid);
 
+	/* yield to self */
 	if (tid == vcpu->vcpu_id)
-		return 0;
+		goto no_yield;
 
+	/* yield to invalid */
 	tcpu = kvm_get_vcpu_by_id(vcpu->kvm, tid);
-	if (tcpu)
-		kvm_vcpu_yield_to(tcpu);
+	if (!tcpu)
+		goto no_yield;
+
+	/* target already running */
+	if (READ_ONCE(tcpu->cpu) >= 0)
+		goto no_yield;
+
+	if (kvm_vcpu_yield_to(tcpu) <= 0)
+		goto no_yield;
+
+	VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d: done", tid);
+	return 0;
+no_yield:
+	VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d: ignored", tid);
+	vcpu->stat.diagnose_9c_ignored++;
 	return 0;
 }