diff --git a/virt/kvm/iodev.h b/virt/kvm/iodev.h
index 2c67f5a..06e38b2 100644
--- a/virt/kvm/iodev.h
+++ b/virt/kvm/iodev.h
@@ -20,6 +20,9 @@
 
 struct kvm_io_device;
 
+/**
+ * kvm_io_device_ops are called under kvm slots_lock.
+ **/
 struct kvm_io_device_ops {
 	void (*read)(struct kvm_io_device *this,
 		     gpa_t addr,