Re: [dpdk-dev] [PATCH v2 3/3] virtio-user: set status on virtio-user reconnect

["Xia, Chenbo" <chenbo.xia@intel.com>]

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Thursday, October 22, 2020 3:14 PM
> To: Wang, Yinan <yinan.wang@intel.com>; Adrian Moreno
> <amorenoz@redhat.com>; dev@dpdk.org; Xia, Chenbo <chenbo.xia@intel.com>
> Cc: Fu, Patrick <patrick.fu@intel.com>; stable@dpdk.org; Wang, Zhihong
> <zhihong.wang@intel.com>; Xu, Qian Q <qian.q.xu@intel.com>
> Subject: Re: [PATCH v2 3/3] virtio-user: set status on virtio-user
> reconnect
> 
> Hi Yinan,
> 
> On 10/22/20 6:01 AM, Wang, Yinan wrote:
> > Hi Maxime/ Adrian，
> >
> > Thanks for the patch.  we can launch vhost-user with client mode with
> this fix patch.
> > But still fail to get throughput with basic vhost/virtio-user server
> mode loopback test. This is another problem which introduced by
> 57912824615fd7787a48a7b18e40661466.
> > Bugzilla: https://bugs.dpdk.org/show_bug.cgi?id=541
> 
> Thanks for reporting the issue, I will look at it this morning.
> 
> BTW, this virtio-user server mode is broken by design, we should really
> fix it.
> 
> For example, it assumes features to be supported by the backend before
> the negotiation took place:
> https://git.dpdk.org/dpdk/tree/drivers/net/virtio/virtio_user/virtio_user_
> dev.c#n513
> 
> As part of my rework, I suggest we implement the same behaviour as QEMU
> does, which will be reliable and consistent with QEMU. It means that if
> server mode is enabled in device command-line, the driver waits until
> the socket is ready.
> 
> Chenbo, Adrian, what do you think?

Yes! I totally agree and have the same opinion for a long time. As I remember, this
feature assumption has caused problems before and I notice the new STATUS feature is
also affected. It's good to make this consistent with QEMU 😊.

Cheers,
Chenbo

> 
> Thanks,
> Maxime
> 
> > BR,
> > Yinan
> >> -----Original Message-----
> >> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> >> Sent: 2020年10月21日 0:43
> >> To: Adrian Moreno <amorenoz@redhat.com>; dev@dpdk.org
> >> Cc: Wang, Yinan <yinan.wang@intel.com>; Fu, Patrick
> <patrick.fu@intel.com>;
> >> stable@dpdk.org; Xia, Chenbo <chenbo.xia@intel.com>; Wang, Zhihong
> >> <zhihong.wang@intel.com>
> >> Subject: Re: [PATCH v2 3/3] virtio-user: set status on virtio-user
> reconnect
> >>
> >>
> >>
> >> On 10/20/20 5:20 PM, Adrian Moreno wrote:
> >>> Newer vhost-user backends will rely on SET_STATUS to start the device
> >>> so this required to support them.
> >>>
> >>> Fixes: 57912824615f ("net/virtio-user: support vhost status setting")
> >>> Cc: maxime.coquelin@redhat.com
> >>> Cc: stable@dpdk.org
> >>>
> >>> Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
> >>> ---
> >>>  drivers/net/virtio/virtio_user_ethdev.c | 14 ++++++++++++--
> >>>  1 file changed, 12 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/net/virtio/virtio_user_ethdev.c
> >> b/drivers/net/virtio/virtio_user_ethdev.c
> >>> index e870fb2ff..d8bea4537 100644
> >>> --- a/drivers/net/virtio/virtio_user_ethdev.c
> >>> +++ b/drivers/net/virtio/virtio_user_ethdev.c
> >>> @@ -78,6 +78,13 @@ virtio_user_server_reconnect(struct virtio_user_dev
> >> *dev)
> >>>  		return -1;
> >>>
> >>>  	dev->vhostfd = connectfd;
> >>> +
> >>> +	vtpci_reset(hw);
> >>> +
> >>> +	vtpci_set_status(hw, VIRTIO_CONFIG_STATUS_ACK);
> >>> +
> >>> +	vtpci_set_status(hw, VIRTIO_CONFIG_STATUS_DRIVER);
> >>> +
> >>>  	if (dev->ops->send_request(dev, VHOST_USER_GET_FEATURES,
> >>>  				   &dev->device_features) < 0) {
> >>>  		PMD_INIT_LOG(ERR, "get_features failed: %s",
> >>> @@ -111,6 +118,8 @@ virtio_user_server_reconnect(struct
> virtio_user_dev
> >> *dev)
> >>>
> >>>  	dev->features &= dev->device_features;
> >>>
> >>> +	vtpci_set_status(hw, VIRTIO_CONFIG_STATUS_FEATURES_OK);
> >>> +
> >>>  	/* For packed ring, resetting queues is required in reconnection. */
> >>>  	if (vtpci_packed_queue(hw) &&
> >>>  	   (vtpci_get_status(hw) & VIRTIO_CONFIG_STATUS_DRIVER_OK)) {
> >>> @@ -119,8 +128,9 @@ virtio_user_server_reconnect(struct
> virtio_user_dev
> >> *dev)
> >>>  		virtio_user_reset_queues_packed(eth_dev);
> >>>  	}
> >>>
> >>> -	ret = virtio_user_start_device(dev);
> >>> -	if (ret < 0)
> >>> +	/*  Start the device */
> >>> +	vtpci_set_status(hw, VIRTIO_CONFIG_STATUS_DRIVER_OK);
> >>> +	if (!dev->started)
> >>>  		return -1;
> >>>
> >>>  	if (dev->queue_pairs > 1) {
> >>>
> >>
> >> Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> >>
> >> Thanks,
> >> Maxime
> >