[RFC] lib/ethdev: introduce table driven APIs

[Jerin Jacob]

On Tue, Jun 20, 2023 at 7:22 AM Zhang, Qi Z <qi.z.zhang at intel.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Jerin Jacob <jerinjacobk at gmail.com>
> > Sent: Monday, June 19, 2023 5:52 PM
> > To: Zhang, Qi Z <qi.z.zhang at intel.com>
> > Cc: Dumitrescu, Cristian <cristian.dumitrescu at intel.com>; Ori Kam
> > <orika at nvidia.com>; NBU-Contact-Thomas Monjalon (EXTERNAL)
> > <thomas at monjalon.net>; david.marchand at redhat.com; Richardson, Bruce
> > <bruce.richardson at intel.com>; jerinj at marvell.com; ferruh.yigit at amd.com;
> > Mcnamara, John <john.mcnamara at intel.com>; Zhang, Helin
> > <helin.zhang at intel.com>; techboard at dpdk.org; dev at dpdk.org; Ivan Malov
> > <ivan.malov at arknetworks.am>
> > Subject: Re: [RFC] lib/ethdev: introduce table driven APIs
> >
> > On Mon, Jun 19, 2023 at 5:53 AM Zhang, Qi Z <qi.z.zhang at intel.com> wrote:
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Jerin Jacob <jerinjacobk at gmail.com>
> > > > Sent: Friday, June 16, 2023 9:20 AM
> > > > To: Zhang, Qi Z <qi.z.zhang at intel.com>; Dumitrescu, Cristian
> > > > <cristian.dumitrescu at intel.com>
> > > > Cc: Ori Kam <orika at nvidia.com>; NBU-Contact-Thomas Monjalon
> > > > (EXTERNAL) <thomas at monjalon.net>; david.marchand at redhat.com;
> > > > Richardson, Bruce <bruce.richardson at intel.com>; jerinj at marvell.com;
> > > > ferruh.yigit at amd.com; Mcnamara, John <john.mcnamara at intel.com>;
> > > > Zhang, Helin <helin.zhang at intel.com>; techboard at dpdk.org;
> > > > dev at dpdk.org; Ivan Malov <ivan.malov at arknetworks.am>
> > > > Subject: Re: [RFC] lib/ethdev: introduce table driven APIs
> > > >

> >
> > >
> > > However, the question arises regarding how to handle vendor-specific data,
> > which also can be part of the table / action key and could potentially be
> > mapped to either rte_flow_item_tag or rte_flow_item_metadata. I'm
> > uncertain about how the P4-DPDK compiler can manage this aspect. Perhaps
> > this particular aspect should be addressed by each vendor's individual
> > backend compiler, while we focus on defining the specifications for the
> > output and providing the common components for parser analysis.
> >
> > If we take the compiler path, Why we need vendor specific data?
>
> Let's consider the following scenario:
>
> Assume that a hardware device contains metadata that can be passed between different stages of a pipeline.
>
> For instance, in stage A, a rule is matched, and the metadata is set. In stage B, this metadata is used as a match key.
>
> To design the API calls for the above situation using rte_flow, my understanding is that we need to map a rte_flow_item_tag or rte_flow_item_metadata to the corresponding metadata portion (including offset and size).
> This way, the driver can understand how to configure the hardware accordingly.
>
> In P4, we define data structures to abstract the metadata, and the vender specific-backend compiler determines the arrangement of the metadata space.
>
> However, in our case, how does the proposed compiler establish the mapping from the P4 metadata key to rte_flow without support from the backend compiler?

Yes. We need to change the backend compiler to understand the rte_flow
mapping to p4 to avoid any translation cost.