KVM: document lock nesting rule

Document kvm->lock nesting within kvm->slots_lock

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 5946065..fc1b58a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -68,7 +68,7 @@
 /*
  * Ordering of locks:
  *
- * 		kvm->lock --> kvm->irq_lock
+ * 		kvm->slots_lock --> kvm->lock --> kvm->irq_lock
  */
 
 DEFINE_SPINLOCK(kvm_lock);