Re: [PATCH] vhost: call rte_vhost_enable_guest_notification only on enabled queues

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Thu, Apr 07, 2016 at 03:29:32PM +0000, Loftus, Ciara wrote:
> > On 4/7/2016 8:29 AM, Rich Lane wrote:
> > > If the vhost PMD were configured with more queues than the guest, the
> > old
> > > code would segfault in rte_vhost_enable_guest_notification due to a NULL
> > > virtqueue pointer.
> > >
> > > Fixes: ee584e9710b9 ("vhost: add driver on top of the library")
> > > Signed-off-by: Rich Lane <rich.lane@bigswitch.com>
> > > ---
> > >   drivers/net/vhost/rte_eth_vhost.c | 5 +++--
> > >   1 file changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/net/vhost/rte_eth_vhost.c
> > b/drivers/net/vhost/rte_eth_vhost.c
> > > index b1eb082..310cbef 100644
> > > --- a/drivers/net/vhost/rte_eth_vhost.c
> > > +++ b/drivers/net/vhost/rte_eth_vhost.c
> > > @@ -265,7 +265,6 @@ new_device(struct virtio_net *dev)
> > >   		vq->device = dev;
> > >   		vq->internal = internal;
> > >   		vq->port = eth_dev->data->port_id;
> > > -		rte_vhost_enable_guest_notification(dev, vq-
> > >virtqueue_id, 0);
> > >   	}
> > >   	for (i = 0; i < eth_dev->data->nb_tx_queues; i++) {
> > >   		vq = eth_dev->data->tx_queues[i];
> > > @@ -274,9 +273,11 @@ new_device(struct virtio_net *dev)
> > >   		vq->device = dev;
> > >   		vq->internal = internal;
> > >   		vq->port = eth_dev->data->port_id;
> > > -		rte_vhost_enable_guest_notification(dev, vq-
> > >virtqueue_id, 0);
> > >   	}
> > >
> > > +	for (i = 0; i < dev->virt_qp_nb * VIRTIO_QNUM; i++)
> > > +		rte_vhost_enable_guest_notification(dev, i, 0);
> > > +
> > >   	dev->flags |= VIRTIO_DEV_RUNNING;
> > >   	dev->priv = eth_dev;
> > >   	eth_dev->data->dev_link.link_status = ETH_LINK_UP;
> > 
> > Just one question, when qemu starts a vm, usually, only one queue is
> > enabled, then only 1 tx and 1 rx are called
> > rte_vhost_enable_guest_notification; but after system is up, we use
> > "ethtool -K eth0 combined x" to enable multiqueues, there's no chance to
> > call rte_vhost_enable_guest_notification for other queues, right?
> 
> As far as I know, virt_qp_nb will report the number of queues available, regardless of their state enabled/disabled. So for example if we have 4 queues, but only one enabled, virt_qp_nb should still = 4 and rte_vhost_enable_guest_notification() will be called for all of these queues.

Yes.

	--yliu