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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 49080C432C0 for ; Sun, 1 Dec 2019 21:54:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1A8CC20865 for ; Sun, 1 Dec 2019 21:54:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727322AbfLAVyn (ORCPT ); Sun, 1 Dec 2019 16:54:43 -0500 Received: from shards.monkeyblade.net ([23.128.96.9]:58282 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727298AbfLAVym (ORCPT ); Sun, 1 Dec 2019 16:54:42 -0500 Received: from localhost (unknown [IPv6:2601:601:9f00:1c3::3d5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id 98EE614FD3304; Sun, 1 Dec 2019 13:54:41 -0800 (PST) Date: Sun, 01 Dec 2019 13:54:39 -0800 (PST) Message-Id: <20191201.135439.2128495024712395126.davem@davemloft.net> To: mst@redhat.com Cc: dsahern@gmail.com, prashantbhole.linux@gmail.com, jasowang@redhat.com, ast@kernel.org, daniel@iogearbox.net, jakub.kicinski@netronome.com, hawk@kernel.org, john.fastabend@gmail.com, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, andriin@fb.com, netdev@vger.kernel.org, qemu-devel@nongnu.org, kvm@vger.kernel.org Subject: Re: [RFC net-next 08/18] tun: run offloaded XDP program in Tx path From: David Miller In-Reply-To: <20191201163730-mutt-send-email-mst@kernel.org> References: <20191201.125621.1568040486743628333.davem@davemloft.net> <20191201163730-mutt-send-email-mst@kernel.org> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Sun, 01 Dec 2019 13:54:42 -0800 (PST) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: "Michael S. Tsirkin" Date: Sun, 1 Dec 2019 16:40:22 -0500 > Right. But it is helpful to expose the supported functionality > to guest in some way, if nothing else then so that > guests can be moved between different hosts. > > Also, we need a way to report this kind of event to guest > so it's possible to figure out what went wrong. On the contrary, this is why it is of utmost importance that all XDP implementations support the full suite of XDP facilities from the very beginning. This is why we keep giving people a hard time when they add support only for some of the XDP return values and semantics. Users will get killed by this, and it makes XDP a poor technology to use because behavior is not consistent across device types. That's not acceptable and I'll push back on anything that continues this trend. If you can't HW offload it, kick it to software.