Re: [PATCH 1/6] vhost: allow device that does not depend on vhost worker

[Jason Wang]

On 2020/6/2 äå1:01, Michael S. Tsirkin wrote:
> On Fri, May 29, 2020 at 04:02:58PM +0800, Jason Wang wrote:
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index d450e16c5c25..70105e045768 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -166,11 +166,16 @@ static int vhost_poll_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync,
> >   			     void *key)
> >   {
> >   	struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
> > +	struct vhost_work *work = &poll->work;
> >   
> >   	if (!(key_to_poll(key) & poll->mask))
> >   		return 0;
> >   
> > -	vhost_poll_queue(poll);
> > +	if (!poll->dev->use_worker)
> > +		work->fn(work);
> > +	else
> > +		vhost_poll_queue(poll);
> > +
> >   	return 0;
> >   }
> So a wakeup function wakes up eventfd directly.
>
> What if user supplies e.g. the same eventfd as ioeventfd?
>
> Won't this cause infinite loops?


I'm not sure I get this.

This basically calls handle_vq directly when eventfd is woken up. The 
infinite loops can only happen when handle_vq() tries to write to 
ioeventfd itslef which should be a bug of the device.

Thanks


>