Date:   Mon, 4 Nov 2019 18:47:32 -0700
From:   David Ahern <dsahern@...il.com>
To:     Saeed Mahameed <saeedm@...lanox.com>,
        "jakub.kicinski@...ronome.com" <jakub.kicinski@...ronome.com>
Cc:     "sbrivio@...hat.com" <sbrivio@...hat.com>,
        "nikolay@...ulusnetworks.com" <nikolay@...ulusnetworks.com>,
        "sd@...asysnail.net" <sd@...asysnail.net>,
        Jiri Pirko <jiri@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "stephen@...workplumber.org" <stephen@...workplumber.org>,
        Ariel Levkovich <lariel@...lanox.com>
Subject: Re: [PATCH net-next v2 0/3] VGT+ support

On 11/4/19 6:38 PM, Saeed Mahameed wrote:
> On Fri, 2019-11-01 at 17:21 -0700, Jakub Kicinski wrote:
>> On Fri, 1 Nov 2019 21:28:22 +0000, Saeed Mahameed wrote:
>>> Jakub, since Ariel is still working on his upstream mailing list
>>> skills
>>> :), i would like to emphasis and summarize his point in text style
>>> ;-)
>>> the way we like it.
>>
>> Thanks :)
>>
>>> Bottom line, we tried to push this feature a couple of years ago,
>>> and
>>> due to some internal issues this submission ignored for a while,
>>> now as
>>> the legacy sriov customers are moving towards upstream, which is
>>> for me
>>> a great progress I think this feature worth the shot, also as Ariel
>>> pointed out, VF vlan filter is really a gap that should be closed.
>>>
>>> For all other features it is true that the user must consider
>>> moving to
>>> witchdev mode or find a another community for support.
>>>
>>> Our policy is still strong regarding obsoleting legacy mode and
>>> pushing
>>> all new feature to switchdev mode, but looking at the facts here  I
>>> do
>>> think there is a point here and ROI to close this gap in legacy
>>> mode.
>>>
>>> I hope this all make sense. 
>>
>> I understand and sympathize, you know full well the benefits of
>> working
>> upstream-first...
>>
>> I won't reiterate the entire response from my previous email, but the
>> bottom line for me is that we haven't added a single legacy VF NDO
>> since 2016, I was hoping we never will add more and I was trying to
>> stop anyone who tried.
>>
> 
> The NDO is not the problem here, we can perfectly extend the current
> set_vf_vlan_ndo to achieve the same goal with minimal or even NO kernel
> changes, but first you have to look at this from my angel, i have been
> doing lots of research and there are many points for why this should be
> added to legacy mode:
> 
> 1) Switchdev mode can't replace legacy mode with a press of a button,
> many missing pieces.
> 
> 2) Upstream Legacy SRIOV is incomplete since it goes together with
> flexible vf vlan configuration, most of mlx5 legacy sriov users are
> using customized kernels and external drivers, since upstream is
> lacking this one basic vlan filtering feature, and many users decline
> switching to upstream kernel due to this missing features.
> 
> 3) Many other vendors have this feature in customized drivers/kernels,
> and many vendors/drivers don't even support switchdev mode (mlx4 for
> example), we can't just tell the users of such device we are not
> supporting basic sriov legacy mode features in upstream kernel.
> 
> 4) the motivation for this is to slowly move sriov users to upstream
> and eventually to switchdev mode.

If the legacy freeze started in 2016 and we are at the end of 2019, what
is the migration path?


> 
> Now if the only remaining problem is the uAPI, we can minimize kernel
> impact or even make no kernel changes at all, only ip route2 and
> drivers, by reusing the current set_vf_vlan_ndo.

And this caught my eye as well -- iproute2 does not need the baggage either.

Is there any reason this continued support for legacy sriov can not be
done out of tree?

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