Re: [PATCH] net/virtio-user: fix multiple queues fail in server mode

["Yang, Zhiyong" <zhiyong.yang@intel.com>]

Hi  Tiwei,

> -----Original Message-----
> From: Bie, Tiwei
> Sent: Thursday, May 10, 2018 10:47 AM
> To: Yang, Zhiyong <zhiyong.yang@intel.com>
> Cc: dev@dpdk.org; maxime.coquelin@redhat.com; Yao, Lei A
> <lei.a.yao@intel.com>; stable@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] net/virtio-user: fix multiple queues fail in
> server mode
> 
> On Wed, May 09, 2018 at 05:49:36PM +0800, zhiyong.yang@intel.com wrote:
> > This patch fixes multiple queues failure when virtio-user works in
> > server mode.
> >
> > Fixes: bd8f50a45d0f ("net/virtio-user: support server mode")
> > Cc: stable@dpdk.org
> > Signed-off-by: Zhiyong Yang <zhiyong.yang@intel.com>
> > ---
> >  drivers/net/virtio/virtio_user/vhost_user.c      | 3 +++
> >  drivers/net/virtio/virtio_user/virtio_user_dev.c | 9 +++++++++
> >  2 files changed, 12 insertions(+)
> >
> > diff --git a/drivers/net/virtio/virtio_user/vhost_user.c
> > b/drivers/net/virtio/virtio_user/vhost_user.c
> > index a6df97a00..a9e53d7b5 100644
> > --- a/drivers/net/virtio/virtio_user/vhost_user.c
> > +++ b/drivers/net/virtio/virtio_user/vhost_user.c
> > @@ -263,6 +263,9 @@ vhost_user_sock(struct virtio_user_dev *dev,
> >
> >  	PMD_DRV_LOG(INFO, "%s", vhost_msg_strings[req]);
> >
> > +	if (vhostfd < 0)
> > +		return -1;
> 
> I think this is just a workaround to avoid printing error messages in server
> mode.
> 
> Ideally, vhost_user_sock() shouldn't be called with vhostfd < 0.
> 
> If we want this workaround, we should only allow this in server mode. I.e. do
> the check like this:
> 
> 	if (dev->is_server && vhostfd < 0)
> 		return -1;
 
Ok. 

> > +
> >  	msg.request = req;
> >  	msg.flags = VHOST_USER_VERSION;
> >  	msg.size = 0;
> > diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> > b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> > index 38b8bc90d..e988dc3f4 100644
> > --- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> > +++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> > @@ -126,6 +126,10 @@ virtio_user_start_device(struct virtio_user_dev
> *dev)
> >  	features &= ~(1ull << VIRTIO_NET_F_MAC);
> >  	/* Strip VIRTIO_NET_F_CTRL_VQ, as devices do not really need to
> know */
> >  	features &= ~(1ull << VIRTIO_NET_F_CTRL_VQ);
> > +	/* Also disable features which depend on VIRTIO_NET_F_CTRL_VQ
> */
> > +	features &= ~(1ull << VIRTIO_NET_F_CTRL_RX);
> > +	features &= ~(1ull << VIRTIO_NET_F_CTRL_VLAN);
> > +	features &= ~(1ull << VIRTIO_NET_F_CTRL_MAC_ADDR);
> 
> Is this really related to this fix?
> 

Yes.  if vhost user side receives these feature bits and  
Vhost user doesn’t  support these features and will close the socket connection.
If we have disable ctrl_VQ,  also should disable them.


> >  	features &= ~(1ull << VIRTIO_NET_F_STATUS);
> >  	ret = dev->ops->send_request(dev, VHOST_USER_SET_FEATURES,
> &features);
> >  	if (ret < 0)
> > @@ -488,6 +492,11 @@ virtio_user_handle_ctrl_msg(struct
> virtio_user_dev *dev, struct vring *vring,
> >  		queues = *(uint16_t *)(uintptr_t)vring->desc[idx_data].addr;
> >  		status = virtio_user_handle_mq(dev, queues);
> >  	}
> > +	/* Server mode can't enable queue pairs if vhostfd is not connected,
> > +	 * we suppose that status always returns 0 in this case.
> > +	 * /
> 
> As Ferruh pointed, a typo here.
Ok. fix it.

> 
> > +	if (dev->is_server && dev->vhostfd < 0)
> > +		status = 0;
> 
> When the connection to the backend isn't established in server mode, what
> virtio_user_handle_mq() can't do is to enable the queue pairs. But other
> checks in that function are still valid. So I would suggest moving above code
> to virtio_user_handle_mq().
Ok. 

Thanks
Zhiyong