From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 28 Feb 2023 03:52:44 -0500 From: "Michael S. Tsirkin" Subject: Re: [PATCH v9] virtio-net: support inner header hash Message-ID: <20230228034620-mutt-send-email-mst@kernel.org> References: <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> <20230227124800-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit To: Jason Wang 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 Tue, Feb 28, 2023 at 11:04:26AM +0800, Jason Wang wrote: > On Tue, Feb 28, 2023 at 1:49 AM Michael S. Tsirkin wrote: > > > > On Mon, Feb 27, 2023 at 04:35:09PM +0800, Jason Wang wrote: > > > On Mon, Feb 27, 2023 at 3:39 PM 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. > > > > Until people start asking exactly for maps because they want > > state for their classifier? > > Yes, but let's compare the eBPF without maps with the static feature > proposed here. It is much more scalable and flexible. > > > And it makes sense - if you want > > e.g. load balancing you need stats which needs maps. > > Yes, but we know it's possible to have that (through the XDP offload). > This is impossible with the approach proposed here. I'm not actually objecting. And at least we then don't need to worry about leaking info - it's not virtio leaking info it's the bpf program. I wonder what does Heng Qi think. Heng Qi would it work for your scenario? > > > > > 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/ethernet/dynamic-device-personalization-brief.html > > > > Dave seems to have nacked this approach, no? > > I may miss something but looking at kernel commit, there are few > patches to support that: > > E.g > > commit c7648810961682b9388be2dd041df06915647445 > Author: Tony Nguyen > Date: Mon Sep 9 06:47:44 2019 -0700 > > ice: Implement Dynamic Device Personalization (DDP) download > > And it has been used by DPDK drivers. > > Thanks If we are talking about netdev then this discussion has to take place on netdev. If it's dpdk this is more believable. > > > > > > > > > > -- > > > > MST > > > > > >