On Wed, 16 Mar 2016 13:32:59 +0100 Paolo Bonzini <pbonz...@redhat.com> wrote:
> On 16/03/2016 13:22, Cornelia Huck wrote: > >> > Yeah, it doesn't help that the functions are underdocumented (as in the > >> > "assign" parameter above). > > My understanding is: > > > > - 'assign': set up a new notifier (true) or disable it (false) > > - 'set_handler': use our handler (true) or have it handled elsewhere > > (false) > > Right. So if we're setting up a new notifier in > virtio_queue_aio_set_host_notifier_handler, virtio_pci_stop_ioeventfd should ...do what? ;) > > > > > I don't think the ->set_host_notifiers() api really allows for this. > > > > > > I think it does, assign is the last argument to k->set_host_notifier(). > > > > This depends on whether we want 'assign' to clean up any old notifiers > > before setting up new ones. I think we want different behaviour for > > dataplane and vhost. > > I think dataplane and vhost are the same. > > The question is whether ioeventfd=off,vhost=on or > ioeventfd=off,dataplane=on are valid combinations; I think they aren't. We should disallow that even temporary, then. (This would imply that we need to drop the _stop_ioeventfd() call in ->set_host_notifier(), correct?) > If they aren't, it should be okay to remove the > virtio_queue_host_notifier_read call in > virtio_queue_set_host_notifier_fd_handler and > virtio_queue_aio_set_host_notifier_handler. That's because a handler > for the notifier will always be set _somewhere_. It could be the usual > ioeventfd handler, the vhost handler or the dataplane handler, but one > will be there. It should; but we probably need to do a final read when we stop the ioeventfd.