Re: [PATCH v4] ethdev: add special flags when creating async transfer table

[Thomas Monjalon <thomas@monjalon.net>]

08/11/2022 15:38, Andrew Rybchenko:
> On 11/8/22 16:29, Thomas Monjalon wrote:
> > 08/11/2022 12:47, Andrew Rybchenko:
> >> On 11/8/22 14:39, Andrew Rybchenko wrote:
> >>> On 11/4/22 13:44, Rongwei Liu wrote:
> >>>> diff --git a/lib/ethdev/rte_flow.h b/lib/ethdev/rte_flow.h
> >>>> index 8858b56428..1eab12796f 100644
> >>>> --- a/lib/ethdev/rte_flow.h
> >>>> +++ b/lib/ethdev/rte_flow.h
> >>>> @@ -5186,6 +5186,34 @@ rte_flow_actions_template_destroy(uint16_t
> >>>> port_id,
> >>>>     */
> >>>>    struct rte_flow_template_table;
> >>>> +/**
> >>>> + * @warning
> >>>> + * @b EXPERIMENTAL: this API may change without prior notice.
> >>>> + *
> >>>> + * Special optional flags for template table attribute.
> >>>> + * Each bit stands for a table specialization
> >>>> + * offering a potential optimization at PMD layer.
> >>>> + * PMD can ignore the unsupported bits silently.
> >>>> + */
> >>>> +enum rte_flow_template_table_specialize {
> >>>> +    /**
> >>>> +     * Specialize table for transfer flows which come only from wire.
> >>>> +     * It allows PMD not to allocate resources for non-wire
> >>>> originated traffic.
> >>>> +     * This bit is not a matching criteria, just an optimization hint.
> >>>> +     * Flow rules which match non-wire originated traffic will be missed
> >>>> +     * if the hint is supported.
> >>
> >> Sorry, but if so, the hint changes behavior.
> > 
> > Yes the hint may change behaviour.
> > 
> >> Let's consider a rule which matches both VF originating and
> >> wire originating traffic. Will the rule be missed (ignored)
> >> regardless if the hint is supported or not?
> > 
> > If the hint RTE_FLOW_TRANSFER_WIRE_ORIG is used,
> > the PMD may assume the table won't be used for traffic
> > which is not coming from wire ports.
> > As a consequence, the table may be implemented on the path
> > of wire traffic only.
> > In this case, the traffic coming from virtual ports
> > won't be affected by this table.
> > To answer the question, a rule matching both virtual and wire traffic
> > will be applied in a table affecting only wire traffic,
> > so it will still apply (not completely ignored).
> 
> If so, it is not a hint. It becomes matching criteria
> which should be in pattern as we discussed.

It is not a strict matching because the PMD is free to support it or not.