KVM: document lock nesting rule

Document kvm->lock nesting within kvm->slots_lock
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

virt/kvm/kvm_main.c

@@ -68,7 +68,7 @@ MODULE_LICENSE("GPL");
 /*
  * Ordering of locks:
  *
- * 		kvm->lock --> kvm->irq_lock
+ * 		kvm->slots_lock --> kvm->lock --> kvm->irq_lock
  */
 
 DEFINE_SPINLOCK(kvm_lock);