From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from ws5-mx01.kavi.com (ws5-mx01.kavi.com [34.193.7.191]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3C46BC678D4 for ; Thu, 2 Mar 2023 07:42:20 +0000 (UTC) Received: from lists.oasis-open.org (oasis.ws5.connectedcommunity.org [10.110.1.242]) by ws5-mx01.kavi.com (Postfix) with ESMTP id 49C4B2ACA8 for ; Thu, 2 Mar 2023 07:42:19 +0000 (UTC) Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 283B498667E for ; Thu, 2 Mar 2023 07:42:19 +0000 (UTC) Received: from host09.ws5.connectedcommunity.org (host09.ws5.connectedcommunity.org [10.110.1.97]) by lists.oasis-open.org (Postfix) with QMQP id 0E471983EB8; Thu, 2 Mar 2023 07:42:19 +0000 (UTC) Mailing-List: contact virtio-dev-help@lists.oasis-open.org; run by ezmlm List-Id: Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id EB411986674 for ; Thu, 2 Mar 2023 07:42:18 +0000 (UTC) X-Virus-Scanned: amavisd-new at kavi.com X-MC-Unique: ZNf_d0byMAuMYw5nF5nT9Q-1 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1677742935; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=O9xvXmGZyO/ORzW2Sm8cV8FSEeXyOc0GMQDqezateig=; b=fFXTvUZBAonvpRyHs3Avi6doc5ezFSc374l0RJ7f8qinElZpX0tc911Xl2zxdBO8Rn aTY+CX/Z+CRTlz2KkAG55xev0TJojbLZ/+yPla1wNJUa4ZzUf5IPAr8QDWKY438FxhNV 6vEDtWEQisSc8vgSyHwQT9IcMFirZTi/cnTGpsjKU6kBzOcsp23y1sxfmKbrrz9WmoAX NsKRcKH2Wimg59Aq+dxtZMt9omMUAsj4o+irsK0FHv5LwVyqXdLFY+pvq/s9d5MzxCN5 pv46aySd+TKubh+b/MFPF9sZqb10wK+2D8MeOtG3Zxay1hs5Tw0eOKneIrfuGpfoAdlb Gvew== X-Gm-Message-State: AO0yUKXZN990kji6ef0j4TH1AqilaC9WD/t78D143dOhVioZFQaGXB3P IwQiVY9pRUabqSuDlrmuiQml/QhOvqAWl07t5M87gQNAD1AyhR4nweJCrY8fffF8i2rWNomE2Ad N2JwOdOXLVDcC6HxnqtKiVgGXZ4Jn X-Received: by 2002:a05:600c:491f:b0:3ea:bc08:42ad with SMTP id f31-20020a05600c491f00b003eabc0842admr7004203wmp.2.1677742934793; Wed, 01 Mar 2023 23:42:14 -0800 (PST) X-Google-Smtp-Source: AK7set/7hioXyDkcW7ijSRo4vOW6rfYqBidwUpFXbSaen07ieKxpN14VEK8KBSwKNRcuVGaHvnrWHQ== X-Received: by 2002:a05:600c:491f:b0:3ea:bc08:42ad with SMTP id f31-20020a05600c491f00b003eabc0842admr7004188wmp.2.1677742934449; Wed, 01 Mar 2023 23:42:14 -0800 (PST) Date: Thu, 2 Mar 2023 02:42:10 -0500 From: "Michael S. Tsirkin" 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 Message-ID: <20230302024129-mutt-send-email-mst@kernel.org> References: <20230224030509-mutt-send-email-mst@kernel.org> <20230227023657-mutt-send-email-mst@kernel.org> <20230227124800-mutt-send-email-mst@kernel.org> <20230228060352-mutt-send-email-mst@kernel.org> <20230301053407-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Subject: [virtio-dev] Re: [PATCH v9] virtio-net: support inner header hash On Thu, Mar 02, 2023 at 10:57:12AM +0800, Jason Wang wrote: > On Wed, Mar 1, 2023 at 6:36 PM Michael S. Tsirkin wrote: > > > > On Wed, Mar 01, 2023 at 10:36:41AM +0800, Jason Wang wrote: > > > On Tue, Feb 28, 2023 at 7:05 PM Michael S. Tsirkin wrote: > > > > > > > > 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. > > > > > > > > I looked for some examples of RSS using BPF and only found this: > > > > https://github.com/Netronome/bpf-samples/blob/master/programmable_rss/rss_user.c > > > > seems to use maps. > > > > > > Yes and this is also the way we emulate RSS with TUN/TAP via steering > > > eBPF support for TUN/TAP. The reason is that it needs to emulate not > > > only the hash but also the indirection. If we only replace the hash > > > function with the eBPF program but reuse the RSS indirection table, we > > > don't need maps. > > > > How? Add a special helper? > > We can let the eBPF program return the hash: > > [eBPF hasing] -> hash value -> [indirection table lookup] > > Note that if we don't consider future full eBPF offloading, we can > start with classical BPF. > > Thanks So again this is a custom thing not a standard use of BPF. Normally value returned is pass/drop. > > > > > > > > > > > > > > > > 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). > > > > > > > > Not without a lot more work to make xdp offload happen. > > > > > > > > > > Yes, that's why a simple eBPF RSS hashing program looks much more easier. > > > > > > Thanks > > > > Notice that at this point this is no longer a generic BPF - you > > are using a special helper. For tunnels I would imagine two tables > > could easily turn out to be useful. Then what? Another table? > > If yes then I can't say I like where this is going ... > > > > > > > This is impossible with the approach proposed here. > > > > > > > > > > > > > > > > > > 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 > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > MST > > > > > > > > > > > > > > > > > > > > --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org