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

From: Maxime Coquelin <maxime.coquelin@redhat.com>
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" <dev@dpdk.org>, "Pei, Andy" <andy.pei@intel.com>
Subject: Re: [dpdk-dev] [PATCH v1 0/3] Introduce new class for vDPA device drivers
Date: Thu, 9 Jan 2020 10:23:54 +0100	[thread overview]
Message-ID: <269e1b71-89de-94a2-58db-221f78ef3955@redhat.com> (raw)
In-Reply-To: <1669723.3VsfAaAtOV@xps>

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

Regards,
Maxime