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=-10.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 459F7C388F9 for ; Thu, 5 Nov 2020 03:47:14 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 828E02072C for ; Thu, 5 Nov 2020 03:47:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UEBmX6na" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 828E02072C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:60496 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kaWEy-0004ig-8o for qemu-devel@archiver.kernel.org; Wed, 04 Nov 2020 22:47:12 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:34696) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kaWEN-0004Jq-0R for qemu-devel@nongnu.org; Wed, 04 Nov 2020 22:46:35 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:40813) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kaWEK-000332-M5 for qemu-devel@nongnu.org; Wed, 04 Nov 2020 22:46:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604547990; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GXM8TA/WnHaF9AzQBruktsLJJSNG7pP9SvEx2+w6nG0=; b=UEBmX6navR54sj4afOL8iyndY29Up9xYWZd37uGuSsB+nmU5VBNgcMsHuYSoA11MEy5oVf bzWgOvvhaM5NHbeHfFkNh73049Z1frkMXJ/4a7+ZqDbc+YZXZIDZXyCQUHU21R81cAJS2D cJjFoI+zJRw2LSvrYG3lrF48WkEELik= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-590-00PKAT_yP5a8LN5A5q-3Dw-1; Wed, 04 Nov 2020 22:46:26 -0500 X-MC-Unique: 00PKAT_yP5a8LN5A5q-3Dw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 92D188049CB; Thu, 5 Nov 2020 03:46:25 +0000 (UTC) Received: from [10.72.13.154] (ovpn-13-154.pek2.redhat.com [10.72.13.154]) by smtp.corp.redhat.com (Postfix) with ESMTP id AD1F51002C13; Thu, 5 Nov 2020 03:46:19 +0000 (UTC) Subject: Re: [RFC PATCH 0/6] eBPF RSS support for virtio-net To: =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= References: <20201102185115.7425-1-andrew@daynix.com> <0164a42f-4542-6f3e-bd71-3319dfaae190@redhat.com> <20201104093155.GB565323@redhat.com> From: Jason Wang Message-ID: Date: Thu, 5 Nov 2020 11:46:18 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201104093155.GB565323@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=63.128.21.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/04 22:46:30 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Yan Vugenfirer , Yuri Benditovich , Andrew Melnychenko , qemu-devel@nongnu.org, "Michael S . Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/11/4 下午5:31, Daniel P. Berrangé wrote: > On Wed, Nov 04, 2020 at 10:07:52AM +0800, Jason Wang wrote: >> On 2020/11/3 下午6:32, Yuri Benditovich wrote: >>> >>> On Tue, Nov 3, 2020 at 11:02 AM Jason Wang >> > wrote: >>> >>> >>> On 2020/11/3 上午2:51, Andrew Melnychenko wrote: >>> > Basic idea is to use eBPF to calculate and steer packets in TAP. >>> > RSS(Receive Side Scaling) is used to distribute network packets >>> to guest virtqueues >>> > by calculating packet hash. >>> > eBPF RSS allows us to use RSS with vhost TAP. >>> > >>> > This set of patches introduces the usage of eBPF for packet steering >>> > and RSS hash calculation: >>> > * RSS(Receive Side Scaling) is used to distribute network packets to >>> > guest virtqueues by calculating packet hash >>> > * eBPF RSS suppose to be faster than already existing 'software' >>> > implementation in QEMU >>> > * Additionally adding support for the usage of RSS with vhost >>> > >>> > Supported kernels: 5.8+ >>> > >>> > Implementation notes: >>> > Linux TAP TUNSETSTEERINGEBPF ioctl was used to set the eBPF program. >>> > Added eBPF support to qemu directly through a system call, see the >>> > bpf(2) for details. >>> > The eBPF program is part of the qemu and presented as an array >>> of bpf >>> > instructions. >>> > The program can be recompiled by provided Makefile.ebpf(need to >>> adjust >>> > 'linuxhdrs'), >>> > although it's not required to build QEMU with eBPF support. >>> > Added changes to virtio-net and vhost, primary eBPF RSS is used. >>> > 'Software' RSS used in the case of hash population and as a >>> fallback option. >>> > For vhost, the hash population feature is not reported to the guest. >>> > >>> > Please also see the documentation in PATCH 6/6. >>> > >>> > I am sending those patches as RFC to initiate the discussions >>> and get >>> > feedback on the following points: >>> > * Fallback when eBPF is not supported by the kernel >>> >>> >>> Yes, and it could also a lacking of CAP_BPF. >>> >>> >>> > * Live migration to the kernel that doesn't have eBPF support >>> >>> >>> Is there anything that we needs special treatment here? >>> >>> Possible case: rss=on, vhost=on, source system with kernel 5.8 >>> (everything works) -> dest. system 5.6 (bpf does not work), the adapter >>> functions, but all the steering does not use proper queues. >> >> Right, I think we need to disable vhost on dest. >> >> >>> >>> >>> > * Integration with current QEMU build >>> >>> >>> Yes, a question here: >>> >>> 1) Any reason for not using libbpf, e.g it has been shipped with some >>> distros >>> >>> >>> We intentionally do not use libbpf, as it present only on some distros. >>> We can switch to libbpf, but this will disable bpf if libbpf is not >>> installed >> >> That's better I think. >> >> >>> 2) It would be better if we can avoid shipping bytecodes >>> >>> >>> >>> This creates new dependencies: llvm + clang + ... >>> We would prefer byte code and ability to generate it if prerequisites >>> are installed. >> >> It's probably ok if we treat the bytecode as a kind of firmware. > That is explicitly *not* OK for inclusion in Fedora. They require that > BPF is compiled from source, and rejected my suggestion that it could > be considered a kind of firmware and thus have an exception from building > from source. Please refer what it was done in DPDK: http://git.dpdk.org/dpdk/tree/doc/guides/nics/tap.rst#n235 I don't think what proposed here makes anything different. It's still a bytecode that lives in an array. > >> But in the long run, it's still worthwhile consider the qemu source is used >> for development and llvm/clang should be a common requirement for generating >> eBPF bytecode for host. > So we need to do this right straight way before this merges. Yes. Thanks > > Regards, > Daniel