Merge tag 'kvm-s390-master-4.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux

KVM: s390: Fix for user-triggerable WARN_ON

A malicious user space can provide an invalid mode for runtime
instrumentation via the interfaces that are normally used on
the target host during migration. This would trigger a WARN_ON
via validity intercept. Let's detect this special case.

arch/s390/kvm/intercept.c

@@ -119,8 +119,13 @@ static int handle_validity(struct kvm_vcpu *vcpu)
 
 	vcpu->stat.exit_validity++;
 	trace_kvm_s390_intercept_validity(vcpu, viwhy);
-	WARN_ONCE(true, "kvm: unhandled validity intercept 0x%x\n", viwhy);
-	return -EOPNOTSUPP;
+	KVM_EVENT(3, "validity intercept 0x%x for pid %u (kvm 0x%pK)", viwhy,
+		  current->pid, vcpu->kvm);
+
+	/* do not warn on invalid runtime instrumentation mode */
+	WARN_ONCE(viwhy != 0x44, "kvm: unhandled validity intercept 0x%x\n",
+		  viwhy);
+	return -EINVAL;
 }
 
 static int handle_instruction(struct kvm_vcpu *vcpu)