netdev - Re: [PATCH net-next v2 0/2] flow_offload: add tc police parameters

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Date:   Fri, 18 Feb 2022 11:38:14 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Roi Dayan <roid@...dia.com>, Ido Schimmel <idosch@...sch.org>
Cc:     Jianbo Liu <jianbol@...dia.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        olteanv@...il.com, andrew@...n.ch, vivien.didelot@...il.com,
        f.fainelli@...il.com, davem@...emloft.net, kuba@...nel.org,
        rajur@...lsio.com, claudiu.manoil@....com, sgoutham@...vell.com,
        gakula@...vell.com, sbhatta@...vell.com, hkelam@...vell.com,
        saeedm@...dia.com, leon@...nel.org, idosch@...dia.com,
        petrm@...dia.com, alexandre.belloni@...tlin.com,
        UNGLinuxDriver@...rochip.com, jhs@...atatu.com,
        xiyou.wangcong@...il.com, jiri@...nulli.us,
        baowen.zheng@...igine.com, louis.peens@...ronome.com,
        peng.zhang@...igine.com, oss-drivers@...igine.com
Subject: Re: [PATCH net-next v2 0/2] flow_offload: add tc police parameters

On Thu, Feb 17, 2022 at 01:52:47PM +0200, Roi Dayan wrote:
> On 2022-02-17 1:34 PM, Simon Horman wrote:
> > On Thu, Feb 17, 2022 at 08:28:01AM +0000, Jianbo Liu wrote:
> > > As a preparation for more advanced police offload in mlx5 (e.g.,
> > > jumping to another chain when bandwidth is not exceeded), extend the
> > > flow offload API with more tc-police parameters. Adjust existing
> > > drivers to reject unsupported configurations.
> > 
> > Hi,
> > 
> > I have a concern that
> > a) patch 1 introduces a facility that may break existing drivers; and
> > b) patch 2 then fixes this
> > 
> > I'd slightly prefer if the series was rearranged to avoid this problem.
> > 
> > ...
> 
> Hi Simon,
> 
> It can't be rearranged as patch 2 can't compile without patch 1.
> Patch 1 only adds more information passing to the driver.
> 
> The drivers functionality doesn't change. drivers today ignore
> police information, like actions, and still being ignored after patch 1.
> 
> patch 2 updates the drivers to use that information instead of
> ignoring it. so it fixes the drivers that without patch 1 can't be
> fixed.

I think it would be possible, but...

On Thu, Feb 17, 2022 at 01:56:51PM +0200, Ido Schimmel wrote:

...

> Not sure what you mean by the above. Patch #1 extends the flow offload
> API with tc-police parameters that weren't communicated to drivers until
> now. Drivers still ignore the new parameters after this patch. It is
> only in patch #2 that these drivers reject configurations where the
> parameters are set.
> 
> Therefore, the only breakage I see is the one that can happen after
> patch #2: unaware user space that was installing actions that weren't
> fully reflected to hardware.
> 
> If we want to be on the safe side, it is possible to remove the errors,
> but keep the extack messages so that user space is at least somewhat
> aware.

Yes, I see what you mean.
I'm now comfortable with the way this patchset is arranged.