[dpdk-dev] [PATCH v5 00/29] Support VFD and DPDK PF + kernel VF on i40e

[Chen, Jing D]

Hi, Vincent,

> -----Original Message-----
> From: Vincent JARDIN [mailto:vincent.jardin at 6wind.com]
> Sent: Tuesday, January 10, 2017 9:30 PM
> To: Scott Daniels <daniels at research.att.com>; dev at dpdk.org
> Cc: kaustubh at research.att.com; az5157 at att.com; Chen, Jing D
> <jing.d.chen at intel.com>
> Subject: Re: [dpdk-dev] [PATCH v5 00/29] Support VFD and DPDK PF + kernel VF on
> i40e
> 
> Hi Scott,
> 
> Le 04/01/2017 à 22:09, Scott Daniels a écrit :
> >  With holidays we are a bit late with our thoughts, but would like to
> >  toss them into the mix.
> 
> Same, I hope I am not missing emails. I do appreciate your arguments, it
> provides lot of light. See below,
> 
> >  The original NAK is understandable, however having the ability to
> >  configure the PF via DPDK is advantageous for several reasons:
> >
> >  1) While some functions may be duplicated and/or available from the kernel
> >  driver, it is often not possible to introduce new kernel drivers into
> >  production without a large amount of additional testing of the entire
> >  platform which can cause a significant delay when introducing a DPDK based
> >  product.  If the PF control is a part of the DPDK environment, then only
> >  the application needs to pass the operational testing before deployment; a
> >  much more simple task.
> 
> So we agree: you confirm that your foresee the benefits of using DPDK to
> *bypass the role of the Kernel being the PF* of reference for the
> hypervisor.
> 
> >  2) If the driver changes are upstreamed into the kernel proper, the
> >  difficulty of operational readiness testing increases as a new kernel is
> >  introduced, and further undermines the ability to quickly and easily
> >  release a DPDK based application into production.  While the application
> >  may eventually fall back on driver and/or kernel support, this could be
> >  years away.
> 
> I do agree with the benefits of the agilities and the upsides it brings.
> But they are other options to get the same agility without creating a
> fragmentation of PFs.
> 
> For example, you do not have to update the whole kernel, you can just
> update the PF kernel module that can be upgraded with the latest needed
> features.
> 
> >  3) As DPDK is being used to configure the NIC, it just seems to make
> >  sense, for consistency, that the configuration capabilities should include
> >  the ability to configure the PF as is proposed.
> 
>  From this perspective, the kernel modules are fine for the PF: most
> kernels of hypervisors support it without the need to upgrade their kernels.
> 
> To summarize, I understand that you need a flexible way to upgrade PF
> features without touching/changing the kernel. So let's check the kernel
> module option? VFD brings some interesting capabilities, could it be a
> way to push and stimulate the i40e features instead of using DPDK?
> 
>    https://sourceforge.net/projects/e1000/files/i40e%20stable/
> for instance could be better stimulated.

May I ask what if DPDK VF need a new extension function from PF?
Then, we'll have to build kernel community expertise and submit
patch to Linux PF and wait for merge.
Your proposal indicates DPDK community submitters will have to
ask Linux community to authorize if we'll have any requirements
in DPDK VF.
Comparing fragmentation, the extra dependency worry me most.
Can you imagine how long it will be for any VF features gets
ready?