[EXT] Re: [PATCH v5 2/2] app/testpmd: add command to process Rx metadata negotiation

[Jerin Jacob]

On Fri, Jan 27, 2023 at 8:31 PM Thomas Monjalon <thomas at monjalon.net> wrote:
>
> 27/01/2023 11:42, Nithin Kumar Dabilpuram:
> > From: Thomas Monjalon <thomas at monjalon.net>
> > > 27/01/2023 06:02, Nithin Kumar Dabilpuram:
> > > > From: Thomas Monjalon <thomas at monjalon.net>
> > > > > Ferruh is proposing to have a command "port config <port_id> ..."
> > > > > to configure the flags to negotiate.
> > > > > Are you OK with this approach?
> > > >
> > > > Yes, we are fine to have such command to enable and disable the feature
> > > > with default being it disabled if supported by PMD.
> > > > Is default being disabled fine if the feature is supported by a PMD ?
> > >
> > > I think the default should be enabled for ease of use.
> >
> > Since testpmd is used extensively for benchmarking purposes, we thought it should have minimum features
> > enabled by default. The default testpmd doesn't have any Rx/Tx offloads enabled(except for FAST FREE),  default
> > fwd mode being "iofwd" and the Rx metadata is only referenced when dumping packets.
> >
> >
> > > Do we have similar features disables by default?
> > > I mean do we know features in testpmd which require a "double enablement"
> > > like one configuration command + one rte_flow rule?
> >
> > Spec itself is that way i.e "RTE_FLOW_RULE + RX_METADATA_NEGOTIATE(once)"
> >
> > Isn't it enough if
> >
> > #1 We have enough print when rte_flow is being create without negotiation done and ask user to enable rx metadata using
> > "port config <port_id>..."
> > #2 Provide testpmd app arg to enable Rx metadata(for example " --rx-metadata") like other features to avoid calling another
> > command before rte flow create.
>
> I'm not sure what is best.
> I will let others discuss this part.

IMO, enabling something always defeat the purpose to negotiate. IMO,
someone needs to negotiate
for a feature if the feature is needed. I think, the double enablement
is part of the spec itself. In case, The PMD
drivers won't like double enablement, no need to implement the PMD
callback. That way, there is no change in the existing flow.

The reason why cnxk driver thought of leveraging negotiate() feature
so that it helps for optimization. e.s.p
function template for multiprocess case as we know what features
needed in fastpath upfront.

If there still concerns with patch we can take up this to TB decide
one way or another to make forward progress. Let us know.



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