On Thu, Jun 15, 2023 at 11:33 AM Zhang, Qi Z <qi.z.zh...@intel.com> wrote: > > Hi Jerin:
Hi Qi > > > -----Original Message----- > > From: Jerin Jacob <jerinjac...@gmail.com> > > Sent: Thursday, June 15, 2023 12:58 PM > > To: Zhang, Qi Z <qi.z.zh...@intel.com> > > Cc: Ori Kam <or...@nvidia.com>; NBU-Contact-Thomas Monjalon (EXTERNAL) > > <tho...@monjalon.net>; david.march...@redhat.com; Richardson, Bruce > > <bruce.richard...@intel.com>; jer...@marvell.com; ferruh.yi...@amd.com; > > Mcnamara, John <john.mcnam...@intel.com>; Zhang, Helin > > <helin.zh...@intel.com>; techbo...@dpdk.org; dev@dpdk.org; Ivan Malov > > <ivan.ma...@arknetworks.am> > > Subject: Re: [RFC] lib/ethdev: introduce table driven APIs > > > > On Thu, Jun 15, 2023 at 7:55 AM Zhang, Qi Z <qi.z.zh...@intel.com> wrote: > > > > > > Hi Ori: > > > > > > Thank you for your review! > > > Comment inline. > > > Please let me know if anything I missed. > > > > > > Thanks > > > Qi > > > > > > > -----Original Message----- > > > > From: Ori Kam <or...@nvidia.com> > > > > Sent: Thursday, June 15, 2023 2:31 AM > > > > To: Zhang, Qi Z <qi.z.zh...@intel.com>; NBU-Contact-Thomas Monjalon > > > > (EXTERNAL) <tho...@monjalon.net>; david.march...@redhat.com; > > > > Richardson, Bruce <bruce.richard...@intel.com>; jer...@marvell.com; > > > > ferruh.yi...@amd.com > > > > Cc: Mcnamara, John <john.mcnam...@intel.com>; Zhang, Helin > > > > <helin.zh...@intel.com>; techbo...@dpdk.org; dev@dpdk.org > > > > Subject: RE: [RFC] lib/ethdev: > > > > > > > > Hi Qi, > > > > > > > > > > > > 1. it may be useful to get some general calling flow what comes from > > > > the application, what comes from the compiler. > > > > Simple example will be good. > > > > > > An example of decap VXLAN TCP flow is explained in problem statement > > > (http://mails.dpdk.org/archives/dev/2023-May/267719.html) > > > covering the following information. > > > > > > 1. the p4 source code, the definition of the table and actions 2. the > > > table / action hints generated by the compiler, details to each fields. > > > 3. How the Control Plane Application utilizes the P4 Runtime API to > > > program the rule with the respective table and action IDs > > > > > > The DPDK PMD is responsible for loading the hints generated by the > > compiler. > > > This enables the PMD to accept requests from the P4 Runtime and reject > > any incompatible request. > > > > I see two different types of device/system category > > > > 1) HW + SW/FW combination that really understands p4 structures and job > > of the driver to is to give work to HW/SW as p4 structure generated from > > vendor specific compiler and runtime gRPC message > > 2) Existing HW and SW drivers implements rte-flow driver. > > > > For item (1), if end user application is using P4 program and P4 runtime and > > this is _API contract_ to application, Not sure why end user care it is DPDK > > PMD or not? > > That's true. DPDK as a platform that manage the hardware, it is required to > provide a channel that connects applications with the hardware responsible > for implementing the contract. > In this context, the PMD (ethdev) serves as the conduit that can fulfill this > requirement. I meant vdev + rawdev combo can be used to talk to FW. > > If driver writer care about using DPDK for driver framework for > > EAL services, simply using vdev etc would be enough. Right? > > I may not fully understand this, a vdev should have a device type, I didn't > see any issue for a ethdev vdev to implement the table-driven APIs. See above. There is a lot of overlap between rte_flow and table driven API is the issue. To make things worst, there is also lib/table/ API. > > > > > For item (2), I think, interest is how to offload p4 workload to rte_flow. > > So > > that _existing_ drivers implements rte_flow can support > > p4 naturally in addition to existing rte_flow API. If that is direction, > > then we > > need to the following. > > While the idea of offloading P4 to rte_flow is certainly interesting, it > doesn't seem to directly address our initial problem statement. > The primary objective is to find a solution for offloading rte_flow into a > P4-based pipeline. Isn't same? If not, Please elaborate on "P4 to rte_flow mapping" vs "offloading rte_flow into a P4-based pipeline" > > We have identified two distinct use cases: > > P4-Aware Applications: > > For applications that are already P4 aware, the proposal suggests the > introduction of a new set of APIs to rte_flow. > These APIs aim to facilitate seamless integration between DPDK and P4 aware > applications. Counter argument for that is, If the P4 is API contract then why bother with DPDK abstraction use vdev + rawdev talk to FW as PMD is just passing message to FW. FW is doing the heavy lifting anyway. > > Non-P4 Aware Applications: > > In the case, our focus is on bridging the existing rte_flow API to the > underlying P4 pipeline. > Currently, we haven't identified any significant gaps in the DPDK APIs. > The key challenge lies in handling the translation process within the PMD > > Thanks > Qi > > > > > a)Improve p4-dpdk compiler backend or add new compiler DPDK backend to > > understand the rte_flow and have helper library in DPDK to understand the > > compiler spec file to translate to rte_flow objects b)Similar case for > > runtime > > API. i.e Have helper functions to translate > > p4 MatchField name etc to appropriate rte_flow objects. > > c)Enhance base rte_flow specification if there are any fundamental gaps to > > express the new pattern or actions (which is not specific to > > p4 and applicable for any flow matching use case) > > > > If we introduce compiler in the pipeline, a lot of translation will get in > > the > > slowpath. And for runtime API, the translation primarily will be name to > > rte_flow object lookup (which is not that costly) and using > > rte_flow_template etc. to amortize the cost by making it burst. > > > > Just my 2c.
