Re: [dpdk-dev] [PATCH v1 0/3] Introduce new class for vDPA device drivers

["Xu, Rosen" <rosen.xu@intel.com>]

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Thursday, January 09, 2020 17:24
> To: Thomas Monjalon <thomas@monjalon.net>; Xu, Rosen
> <rosen.xu@intel.com>
> Cc: Matan Azrad <matan@mellanox.com>; Bie, Tiwei <tiwei.bie@intel.com>;
> Wang, Zhihong <zhihong.wang@intel.com>; Wang, Xiao W
> <xiao.w.wang@intel.com>; Yigit, Ferruh <ferruh.yigit@intel.com>;
> dev@dpdk.org; Pei, Andy <andy.pei@intel.com>
> Subject: Re: [dpdk-dev] [PATCH v1 0/3] Introduce new class for vDPA device
> drivers
> 
> 
> 
> On 1/9/20 9:41 AM, Thomas Monjalon wrote:
> > 09/01/2020 03:27, Xu, Rosen:
> >> Hi,
> >>
> >> From: Thomas Monjalon <thomas@monjalon.net>
> >>> 08/01/2020 13:39, Xu, Rosen:
> >>>> From: Matan Azrad <matan@mellanox.com>
> >>>>> From: Xu, Rosen
> >>>>>> Did you think about OVS DPDK?
> >>>>>> vDPA is a basic module for OVS, currently it will take some
> >>>>>> exception path packet processing for OVS, so it still needs to
> >>>>>> integrate
> >>> eth_dev.
> >>>>>
> >>>>> I don't understand your question.
> >>>>>
> >>>>> What do you mean by "integrate eth_dev"?
> >>>>
> >>>> My questions is in OVS DPDK scenario vDPA device implements eth_dev
> >>>> ops, so create a new class and move ifc code to this new class is not ok.
> >>>
> >>> 1/ I don't understand the relation with OVS.
> >>>
> >>> 2/ no, vDPA device implements vDPA ops.
> >>> If it implements ethdev ops, it is an ethdev device.
> >>>
> >>> Please show an example of what you claim.
> >>
> >> Answers of 1 and 2.
> >>
> >> In OVS DPDK, each network device(such as NIC, vHost etc) of DPDK
> >> needs to be implemented as rte_eth_dev and provides eth_dev_ops such
> as packet TX/RX for OVS.
> >
> > No, OVS is also using the vhost API for vhost port.
> >
> >> Take vHost(Virtio back end) for example, OVS startups vHost interface like
> this:
> >> ovs-vsctl add-port br0 vhost-user-1 -- set Interface vhost-user-1
> >> type=dpdkvhostuser drivers/net/vhost implements vHost as rte_eth_dev
> and integrated in OVS.
> >> OVS can send/receive packets to/from VM with rte_eth_tx_burst()
> >> rte_eth_rx_burst() which call eth_dev_ops implementation of
> drivers/net/vhost.
> >
> > No, it is using rte_vhost_dequeue_burst() and
> > rte_vhost_enqueue_burst() which are not in ethdev.
> >
> >> vDPA is also Virtio back end and works like vHost, same as vHost, it
> >> will be implemented as rte_eth_dev and also be integrated into OVS.
> >
> > No, vDPA is not "implemented as rte_eth_dev".
> >
> >> So, it's not ok to move ifc code from drivers/net.
> >
> > drivers/net/ifc has no ethdev implementation at all.
> >
> >
> > Rosen, I'm sorry, these arguments look irrelevant, so I won't consider
> > them as blocking the integration of this patch.
> >
> >
> 
> I agree with Thomas, the vDPA drivers do not implement the ethdev ops.

For OVS hasn't integrated vDPA, it doesn't implement ethdev ops, but there are many
discussions in OVS community about vDPA, it seems vDPA will be supported in OVS in
the near feature.

> And OVS does not use the Vhost PMD for the Vhost-user ports, but directly
> call the librte_vhost APIs.

I'm afraid you are wrong, pls read these documents which introduce how to use vHost-user PMD in OVS:
http://docs.openvswitch.org/en/latest/topics/dpdk/vhost-user/
http://docs.openvswitch.org/en/latest/topics/dpdk/pmd/

> Regards,
> Maxime