hw/virtio: Document *_should_notify() are called within rcu_read_lock()

Such comments make reviewing this file somehow easier.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20210523094040.3516968-1-philmd@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

hw/virtio/virtio.c

@@ -2447,6 +2447,7 @@ static void virtio_set_isr(VirtIODevice *vdev, int value)
     }
 }
 
+/* Called within rcu_read_lock(). */
 static bool virtio_split_should_notify(VirtIODevice *vdev, VirtQueue *vq)
 {
     uint16_t old, new;
@@ -2483,6 +2484,7 @@ static bool vring_packed_need_event(VirtQueue *vq, bool wrap,
     return vring_need_event(off, new, old);
 }
 
+/* Called within rcu_read_lock(). */
 static bool virtio_packed_should_notify(VirtIODevice *vdev, VirtQueue *vq)
 {
     VRingPackedDescEvent e;