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Fri, 23 Sep 2022 00:13:51 -0700 (PDT) X-Google-Smtp-Source: AMsMyM5XnLLNENb85a4WtOFYOoI6PtnDeoQJ8fSbHX0+j9mn/2GwLjmMlUKpX6jS7+4qvw+ixC1W9HJL2ukwpMXYhsc= X-Received: by 2002:a2e:9a88:0:b0:26a:c4d2:3418 with SMTP id p8-20020a2e9a88000000b0026ac4d23418mr2476891lji.81.1663917231706; Fri, 23 Sep 2022 00:13:51 -0700 (PDT) MIME-Version: 1.0 References: <20220628144643.1213026-1-david.marchand@redhat.com> <20220728152640.547725-1-david.marchand@redhat.com> <8AC9271A-AC63-4C5E-BF9C-E4E8027A1132@intel.com> <CAJFAV8wDm_A-fJvTugMxzxBCO_U0R7hcLo-aRK5xDPQKtyc0YQ@mail.gmail.com> <BYAPR11MB2824536FB90CDCC745C5B42AEF769@BYAPR11MB2824.namprd11.prod.outlook.com> <CAJFAV8yNoP5PKx4HN76gGb3iJfXEx2WF83Yep66qx31s-VrxVw@mail.gmail.com> <F932E29C-7F68-4715-8D66-96354ECFB77F@intel.com> In-Reply-To: <F932E29C-7F68-4715-8D66-96354ECFB77F@intel.com> From: David Marchand <david.marchand@redhat.com> Date: Fri, 23 Sep 2022 09:13:40 +0200 Message-ID: <CAJFAV8zL4YWdxt0daU6vz31ybqRmqdLXHD0LDKf5GcjkEu9FRg@mail.gmail.com> Subject: Re: [RFC v3 00/26] Bus and device cleanup for 22.11 To: "Harris, James R" <james.r.harris@intel.com> Cc: "Walker, Benjamin" <benjamin.walker@intel.com>, "dev@dpdk.org" <dev@dpdk.org>, "Liu, Changpeng" <changpeng.liu@intel.com>, Alexey Marchuk <alexeymar@nvidia.com>, Shuhei Matsumoto <smatsumoto@nvidia.com>, Thomas Monjalon <thomas@monjalon.net>, "Richardson, Bruce" <bruce.richardson@intel.com>, Stephen Hemminger <stephen@networkplumber.org> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions <dev.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> Errors-To: dev-bounces@dpdk.org On Thu, Sep 22, 2022 at 12:29 AM Harris, James R <james.r.harris@intel.com> wrote: > > On Aug 30, 2022, at 8:09 AM, David Marchand <david.marchand@redhat.com>= wrote: > > > > On Mon, Aug 29, 2022 at 7:12 PM Walker, Benjamin > > <benjamin.walker@intel.com> wrote: > >>>> Can we keep rte_pci_register(), or a new variation of it that keeps > >>>> the rte_pci_driver structure hidden? Hiding rte_pci_register() woul= d > >>>> mean SPDK can no longer work with a packaged DPDK. Or the DPDK > >>>> packages would need to set enable_driver_sdk which I suspect is not = the > >>> intent. > >>> > >>> What do you think if SPDK maintains a copy of the internal headers? > >>> > >>> The internal API are not supposed to change that often, but we (DPDK)= won't > >>> guarantee it. > >>> This would still put some maintenance burden on SPDK but I think it i= s a good > >>> compromise. > >>> > >> > >> Would these internal symbols be considered part of the public/official= ABI? When > > > > What do you mean by "public/official"? > > If you mean the "stable" ABI (as described in the ABI policy document > > and for which compatibility is preserved across minor versions of the > > ABI), the answer is no: internal symbols are not part of it. > > > > > >> SPDK goes to dynamically load a shared DPDK library, how can we detect > >> whether it's a version that we support linking against? > > > > The runtime version of a DPDK library is available via rte_version(). > > > > > > As for the PCI drivers that SPDK wants to register in DPDK, what do > > you think if SPDK people added and maintained a "generic" PCI driver > > in DPDK. > > This driver would expose a new API (which can not re-expose internal > > structures, like rte_pci_driver and consorts) and ensure its ABI is > > maintained in the long term. > > This makes me think of pci-stub, but in DPDK. > > > > I did not think too much about it and I don't understand what SPDK > > requires, but is there something wrong with this approach? > > The stub driver idea is interesting. In the past we=E2=80=99ve needed acc= ess to more > than what a stub driver would provide - for example, to work around kerne= l > vfio + pci bugs when we probe 24 NVMe SSDs behind a PCIe switch that is > hot-inserted, or conversely handling hot removal of that same switch. So > I=E2=80=99m worried that even if we do the stub driver, we end up running= into a > case where we need these header file copies anyways. Not ruling the stub > driver out, but I think it's a longer-term goal, not something we would h= ave > ready for 22.11 obviously. > > So sticking with the internal header copies for now, this works fine > for LTS and non-LTS releases. What about stable releases (i.e. 22.11.1)? > IIUC, these header files could change in a stable release since they are > no longer part of the ABI? In theory, yes they can change. But this is a price to pay, as no one seems willing to invest and maintain a stable API for PCI drivers. I just noticed that some parts of the cleanups I had proposed have been merged in SPDK. Next time, I prefer getting some feedback from SPDK community before my SoB is applied (or stripped) on modified patches. Thanks. --=20 David Marchand