Re: [PATCH] vhost: fix notification for packed ring

[Tiwei Bie <tiwei.bie@intel.com>]

On Thu, Oct 11, 2018 at 09:36:48AM -0400, Michael S. Tsirkin wrote:
> On Thu, Oct 11, 2018 at 09:34:06PM +0800, Jason Wang wrote:
> > 
> > 
> > On 2018年10月11日 21:06, Tiwei Bie wrote:
> > > The notification can't be disabled in packed ring when
> > > application tries to disable notification, because the
> > > device event flags field is overwritten by an unexpected
> > > value. This patch fixes this issue.
> > > 
> > > Fixes: b1cce26af1dc ("vhost: add notification for packed ring")
> > > Cc: stable@dpdk.org
> > > 
> > > Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> > > ---
> > >   lib/librte_vhost/vhost.c | 7 +++++--
> > >   1 file changed, 5 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
> > > index e62f4c594..c9270bdec 100644
> > > --- a/lib/librte_vhost/vhost.c
> > > +++ b/lib/librte_vhost/vhost.c
> > > @@ -667,8 +667,10 @@ vhost_enable_notify_packed(struct virtio_net *dev,
> > >   {
> > >   	uint16_t flags;
> > > -	if (!enable)
> > > -		vq->device_event->flags = VRING_EVENT_F_DISABLE;
> > > +	if (!enable) {
> > > +		flags = VRING_EVENT_F_DISABLE;
> > > +		goto out;
> > > +	}
> > >   	flags = VRING_EVENT_F_ENABLE;
> > >   	if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
> > > @@ -677,6 +679,7 @@ vhost_enable_notify_packed(struct virtio_net *dev,
> > >   			vq->avail_wrap_counter << 15;
> > >   	}
> > > +out:
> > >   	rte_smp_wmb();
> > 
> > It looks to me the barrier is even not needed for !enable.
> > 
> > Thanks
> 
> Good point, I agree.
> Besides that
> 
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> 

Yeah, it's better to return directly after disabling the
interrupt. I will send a new version to do this change.

Thanks!

> 
> 
> > >   	vq->device_event->flags = flags;