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Tsirkin" To: Weqaar Janjua Cc: qemu-devel@nongnu.org, kraxel@redhat.com, peter.maydell@linaro.org, pierrick.bouvier@oss.qualcomm.com, jasowangio@gmail.com, pbonzini@redhat.com, farosas@suse.de, lvivier@redhat.com, marcel.apfelbaum@gmail.com, peterx@redhat.com, lizhijian@fujitsu.com, odaki@rsg.ci.i.u-tokyo.ac.jp Subject: Re: [PATCH v3 0/6] hw: Add Cnuas virtual devices Message-ID: <20261031135234-mutt-send-email-mst@kernel.org> References: <20260929202358.725310-1-weqaar.janjua@packetfive.com> <20261016153247.1815153-1-weqaar.janjua@packetfive.com> <20261027080746.2468700-1-weqaar.janjua@packetfive.com> <20261027063724-mutt-send-email-mst@kernel.org> <20261029115735.2716219-1-weqaar.janjua@packetfive.com> <20261029134859-mutt-send-email-mst@kernel.org> <20261029194227.2735464-1-weqaar.janjua@packetfive.com> <20261030191556-mutt-send-email-mst@kernel.org> <20261031120516.2846639-1-weqaar.janjua@packetfive.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261031120516.2846639-1-weqaar.janjua@packetfive.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Sat, Oct 31, 2026 at 12:05:14PM +0000, Weqaar Janjua wrote: > On Fri, Oct 30, 2026 at 07:19:05PM -0400, Michael S. Tsirkin wrote: > > I see. Then a simple way for you to get some eyes on this, and a path > > towards upstreaming, could be to try and add this rdma functionality > > in the virtio spec. > > Interface changes might be required during the standardization > > process. > > Thanks Michael, that is a helpful pointer. > > The intended use of the Cnuas emulated PCIe devices is the reason they > were not designed as virtio devices. > > Cnuas is intended for teaching and research of Open Compute ORV3 > (and future versions as it evolves) rack-scale data center systems, where the > PCIe devices and their drivers are what is being studied. CnuasNIC and > CnuasGPU are small, fully documented PCIe devices in the spirit of > edu, but with production-like features such as configurable link speed and > width, a 64-bit prefetchable BAR (CnuasGPU), and a switch transport > that joins several guests into one fabric. Their guest drivers are > full netdev and RDMA core drivers that run rping, perftest and QEMU > RDMA migration unmodified. Just to clarify these aren't edu extensions > because they are different PCI classes (network and co-processor), and > edu's fixed register map is used by existing course material. My concern with > virtio device is that it would hide the layer we want people to work with. People being the students? > Also, that in the ORV3 rack model, each sled carries its own NIC and accelerator > as separate PCIe functions with their own driver, next to the virtio > devices the guest uses for its disk and management network. > > I understand that a virtio-rdma device could definitely be useful in its own right, > I am happy to look at it separately since the CnuasSwitch backend could serve > both. If you are ok with it, for this series I would like to keep the devices as > they are, in the same spirit as the other QEMU-only devices in the 1b36 range, and > keep looking for a reviewer for patches 2 and 3 (Jason, Peter, Zhijian, Akihiko, > any of you?). > > Thanks, > > Weqaar -- MST