Add virt_ barriers to list of barriers to check for
presence of a comment.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Julian Calaby <julian.calaby@gmail.com> Acked-by: Joe Perches <joe@perches.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>