[PATCH] KVM: s390: check if kernel irqchip is actually enabled

[Cornelia Huck <cohuck@redhat.com>]

On s390, we only allow userspace to create an in-kernel irqchip
if it has first enabled the KVM_CAP_S390_IRQCHIP vm capability.
Let's assume that a userspace that enabled that capability has
created an irqchip as well.

Fixes: 84223598778b ("KVM: s390: irq routing for adapter interrupts.")
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
---

A more precise check would be to add a field in kvm_arch that tracks
whether an irqchip has actually been created; not sure if that is
really needed.

Found while trying to hunt down QEMU crashes with kvm-irqchip=off;
this is not sufficient, though. I *think* everything but irqfds
should work without kvm-irqchip as well, but have not found the problem
yet.

---
 arch/s390/kvm/irq.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/kvm/irq.h b/arch/s390/kvm/irq.h
index 484608c71dd0..30e13d031379 100644
--- a/arch/s390/kvm/irq.h
+++ b/arch/s390/kvm/irq.h
@@ -13,7 +13,7 @@
 
 static inline int irqchip_in_kernel(struct kvm *kvm)
 {
-	return 1;
+	return !!kvm->arch.use_irqchip;
 }
 
 #endif
-- 
2.21.1