netdev - Re: [net-next 1/5] ice: add the virtchnl handler for AdminQ command

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Date:   Sat, 25 Jul 2020 09:39:07 -0700
From:   Tom Herbert <tom@...bertland.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "Venkataramanan, Anirudh" <anirudh.venkataramanan@...el.com>,
        "Wang, Haiyue" <haiyue.wang@...el.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "sassmann@...hat.com" <sassmann@...hat.com>,
        "Bowers, AndrewX" <andrewx.bowers@...el.com>,
        "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        "Lu, Nannan" <nannan.lu@...el.com>
Subject: Re: [net-next 1/5] ice: add the virtchnl handler for AdminQ command

On Wed, Jul 22, 2020 at 6:07 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Thu, 23 Jul 2020 00:37:29 +0000 Venkataramanan, Anirudh wrote:
> > Can you please clarify how you (and the community) define bifurcated
> > driver?
>
> No amount of clarification from me will change the fact that you need
> this for DPDK.

Jakub,

The fundamental problem we have wrt DPDK is that they are not just
satisfied to just bypass the kernel datapath, they are endeavouring to
bypass the kernel control path as well with things like RTE flow API.
The purpose of this patch set, AFAICT, is to keep the kernel in the
control plane path so that we can maintain one consistent management
view of device resources. The unpleasant alternative is that DPDK will
send control messages directly to the device thereby bypassing the
kernel control plane and thus resulting in two independent entities
managing the same device and forcing a bifurcated control plane in the
device (which of course results in a complete mess!).

Tom