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

[Thomas Monjalon <thomas@monjalon.net>]

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 you really want to manage both types of traffic in this table,
you must not use such hint.

> I.e. it will not apply to wire originated traffic as well.
> 
> >> +     */
> >> +    RTE_FLOW_TRANSFER_WIRE_ORIG = RTE_BIT32(0),
> >> +    /**
> >> +     * Specialize table for transfer flows which come only from vport 
> >> (e.g. VF, SF).
> >> +     * It allows PMD not to allocate resources for non-vport 
> >> originated traffic.
> >> +     * This bit is not a matching criteria, just an optimization hint.
> >> +     * Flow rules which match non-vport originated traffic will be 
> >> missed
> >> +     * if the hint is supported.
> >> +     */
> >> +    RTE_FLOW_TRANSFER_VPORT_ORIG = RTE_BIT32(1),
> >> +};
> >> +
> >>   /**
> >>    * @warning
> >>    * @b EXPERIMENTAL: this API may change without prior notice.
> >> @@ -5201,6 +5229,10 @@ struct rte_flow_template_table_attr {
> >>        * Maximum number of flow rules that this table holds.
> >>        */
> >>       uint32_t nb_flows;
> >> +    /**
> >> +     * Optional hint flags for PMD optimization.
> >> +     */
> >> +    enum rte_flow_template_table_specialize specialize;
> > 
> > 
> > IMHO it is not 100% correct to use enum for flag since
> > RTE_FLOW_TRANSFER_WIRE_ORIG | RTE_FLOW_TRANSFER_VPORT_ORIG
> > is not the enum member. uint32_t is a better option here since
> > bits are defined as RTE_BIT32. enum should be mentioned in the
> > description.

I agree, let's not use enum.
Instead we can mention the prefix of the defines in the comments.