Re: [dpdk-dev] [PATCH 00/11] net/vhostpci: A new vhostpci PMD supporting VM2VM scenario

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 12/21/2017 07:26 AM, Yang, Zhiyong wrote:
> 
> 
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Yang, Zhiyong
>> Sent: Thursday, December 21, 2017 2:21 PM
>> To: Tan, Jianfeng <jianfeng.tan@intel.com>; Maxime Coquelin
>> <maxime.coquelin@redhat.com>; dev@dpdk.org; yliu@fridaylinux.org
>> Cc: Wang, Wei W <wei.w.wang@intel.com>
>> Subject: Re: [dpdk-dev] [PATCH 00/11] net/vhostpci: A new vhostpci PMD
>> supporting VM2VM scenario
>>
>> Hi Jianfeng,
>>
>>> -----Original Message-----
>>> From: Tan, Jianfeng
>>> Sent: Thursday, December 21, 2017 1:52 PM
>>> To: Yang, Zhiyong <zhiyong.yang@intel.com>; Maxime Coquelin
>>> <maxime.coquelin@redhat.com>; dev@dpdk.org; yliu@fridaylinux.org
>>> Cc: Wang, Wei W <wei.w.wang@intel.com>
>>> Subject: RE: [PATCH 00/11] net/vhostpci: A new vhostpci PMD supporting
>>> VM2VM scenario
>>>
>>> Hi,
>>>
>>>> -----Original Message-----
>>>> From: Yang, Zhiyong
>>>> Sent: Wednesday, December 20, 2017 9:52 AM
>>>> To: Maxime Coquelin; dev@dpdk.org; yliu@fridaylinux.org
>>>> Cc: Wang, Wei W; Tan, Jianfeng
>>>> Subject: RE: [PATCH 00/11] net/vhostpci: A new vhostpci PMD
>>>> supporting VM2VM scenario
>>>>
>>>> Hi Maxime,
>>>>
>>>>> -----Original Message-----
>>>>> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com]
>>>>> Sent: Tuesday, December 19, 2017 7:15 PM
>>>>> To: Yang, Zhiyong <zhiyong.yang@intel.com>; dev@dpdk.org;
>>>>> yliu@fridaylinux.org
>>>>> Cc: Wang, Wei W <wei.w.wang@intel.com>; Tan, Jianfeng
>>>>> <jianfeng.tan@intel.com>
>>>>> Subject: Re: [PATCH 00/11] net/vhostpci: A new vhostpci PMD
>>>>> supporting VM2VM scenario
>>>>>
>>>>
>>>> <snip>
>>>>
>>>>> Thanks for the RFC.
>>>>> It seems there is a lot of code duplication between this series
>>>>> and
>>>>> libvhost-
>>>> user.
>>>>>
>>>>> Does the non-RFC would make reuse of libvhost-user? I'm thinking
>>>>> of all
>>>> the
>>>>> code copied from virtio-net.c for example.
>>>>>
>>>>> If not, I think this is problematic as it will double the maintenance cost.
>>>>
>>>> Thank you for paying attention to the patchset . TX/RX logic
>>>> basically comes from vhost user code.
>>>> but some function interfaces and data structures are different,  So
>>>> can not reuse them directly, code duplicate should be removed, I'm
>>>> aware of this point too, when I was writing the vhostpci PMD.
>>>>   But We should modify the  libvhost-user firstly,  let libvhostuser
>>>> become more generic.
>>>> It looks like that more and more PMDs are becoming the member of
>>>> virtio family or are on the road.
>>>
>>> Trying to draw a conclusion here, there are two kinds of code
>>> duplication in net/vhost-pci.
>>> - For pci operations in guest driver, it has some duplicated code with
>>> virtio-net pmd.
>>> - For the enqueue/dequeuer operations, it has some duplicated code
>>> with vhost- user lib.
>>>
>>> Right?
>>
>> Right. If the existing code in DPDK can become more generic, we can avoid the
>> duplication.
>>
> 
> BTW,  wonder why vhost user enqueue/dequeue are put in lib layer,not in driver/net/vhost  like virtio PMD?

Because Vhost PMD is not its only user, it exports an API that can be
used directly by the application (e.g. ovs-dpdk).

Regards,
Maxime

>> Thanks
>> Zhiyong
>>
>>> Thanks,
>>> Jianfeng
>>>
>>>>>
>>>>> Cheers,
>>>>> Maxime