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 18:42
> To: Xu, Rosen <rosen.xu@intel.com>; Thomas Monjalon
> <thomas@monjalon.net>
> 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 10:49 AM, Xu, Rosen wrote:
> >
> >
> >> -----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.
> 
> I agree with this statement, but if you look at Mellanox series being reviewed,
> it is defining a new type of port and not use the regular DPDK port type.
> 
> >> 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/
> 
> I can confirm that below command to add ports is not using Vhost PMD but
> directly the  librte_vhost API:
> 
> $ ovs-vsctl add-port br0 dpdkvhostclient0 \
>     -- set Interface dpdkvhostclient0 type=dpdkvhostuserclient \
>        options:vhost-server-path=/tmp/dpdkvhostclient0
> 
> Please check the OVS source code.
> 
> It is possible  to use the Vhost PMD as a regular DPDK port, but this is not
> with above command, and not the recommended way.
> 
> >> Regards,
> >> Maxime
> >
Hi,

What I mentioned and questions are in Matan's email thread.

Thanks,
Rosen