Comment 8 for bug 1673564

I bisected this down to the upstream commit below. Now, that's not to say that this commit is necessarily bad - it may just make an existing problem more reproducible.

commit 7235acdb1144460d9f520f0d931f3cbb79eb244c
Author: Jason Wang <email address hidden>
Date: Mon Apr 25 22:14:32 2016 -0400

    vhost: simplify work flushing

    We used to implement the work flushing through tracking queued seq,
    done seq, and the number of flushing. This patch simplify this by just
    implement work flushing through another kind of vhost work with
    completion. This will be used by lockless enqueuing patch.

    Signed-off-by: Jason Wang <email address hidden>
    Reviewed-by: Michael S. Tsirkin <email address hidden>
    Signed-off-by: Michael S. Tsirkin <email address hidden>