From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: MIME-Version: 1.0 References: <20230218143715.841-1-hengqi@linux.alibaba.com> <20230221124518-mutt-send-email-mst@kernel.org> <4d123e32-1ad0-e692-7fa6-0565eb34c487@redhat.com> <0f53212f-a89b-ad3c-73e3-a7a7b5533058@linux.alibaba.com> <1047920c-5dd5-8f31-0c4c-a108f36155f8@redhat.com> <20230223075934-mutt-send-email-mst@kernel.org> <20230224030509-mutt-send-email-mst@kernel.org> <20230227023657-mutt-send-email-mst@kernel.org> In-Reply-To: <20230227023657-mutt-send-email-mst@kernel.org> From: Jason Wang Date: Mon, 27 Feb 2023 16:35:09 +0800 Message-ID: Subject: Re: [PATCH v9] virtio-net: support inner header hash Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable To: "Michael S. Tsirkin" Cc: Heng Qi , virtio-comment@lists.oasis-open.org, virtio-dev@lists.oasis-open.org, Parav Pandit , Yuri Benditovich , Cornelia Huck , Xuan Zhuo List-ID: On Mon, Feb 27, 2023 at 3:39=E2=80=AFPM Michael S. Tsirkin = wrote: > > On Mon, Feb 27, 2023 at 12:07:17PM +0800, Jason Wang wrote: > > Btw, this kind of 1:1 hash features seems not scalable and flexible. > > It requires an endless extension on bits/fields. Modern NICs allow the > > user to customize the hash calculation, for virtio-net we can allow to > > use eBPF program to classify the packets. It seems to be more flexible > > and scalable and there's almost no maintain burden in the spec (only > > bytecode is required, no need any fancy features/interactions like > > maps), easy to be migrated etc. > > > > Prototype is also easy, tun/tap had an eBPF classifier for years. > > > > Thanks > > Yea BPF offload would be great to have. We have been discussing it for > years though - security issues keep blocking it. *Maybe* it's finally > going to be there but I'm not going to block this work waiting for BPF > offload. And easily migrated is what BPF is not. Just to make sure we're at the same page. I meant to find a way to allow the driver/user to fully customize what it wants to hash/classify. Similar technologies which is based on private solution has been used by some vendors, which allow user to customize the classifier[1] ePBF looks like a good open-source solution candidate for this (there could be others). But there could be many kinds of eBPF programs that could be offloaded. One famous one is XDP which requires many features other than the bytecode/VM like map access, tailcall. Starting from such a complicated type is hard. Instead, we can start from a simple type, that is the eBPF classifier. All it needs is to pass the bytecode to the device, the device can choose to run it or compile it to what it can understand for classifying. We don't need maps, tail calls and other features. We don't need to worry about the security because of its simplicity: the eBPF program is only in charge of doing classification, no other interactions with the driver and packet modification is prohibited. The feature is limited only to the VM/bytecode abstraction itself. What's more, it's a good first step to achieve full eBPF offloading in the future. Thanks [1] https://www.intel.com/content/www/us/en/architecture-and-technology/eth= ernet/dynamic-device-personalization-brief.html > > -- > MST >