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=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 B98C5C2D0A3 for ; Wed, 4 Nov 2020 09:33:19 +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 D263A221F8 for ; Wed, 4 Nov 2020 09:33:18 +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="H/2PzvT6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D263A221F8 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]:59826 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kaFAL-0006GA-Pk for qemu-devel@archiver.kernel.org; Wed, 04 Nov 2020 04:33:17 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:56524) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kaF9I-0005oH-Kt for qemu-devel@nongnu.org; Wed, 04 Nov 2020 04:32:12 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:33935) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kaF9F-0003VC-CY for qemu-devel@nongnu.org; Wed, 04 Nov 2020 04:32:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604482328; h=from:from:reply-to: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=fJ33nL+gPaAOkIMlUQreOlCodNd7oAg9VXwqk4MwIcY=; b=H/2PzvT69Pyf6cZV51+HnYeFZLDxF+7+hTcUBzRFOr9Biovy57mSo8NP08+NNSfLaNcLE5 NAc9Y0Nq/W0QH+lJ6stYpm0J6kB9QX/c7IKkU0MKFvtF3E5gi1iDM0DfxMkbgxrU/7pcBb /hVDiLVSGdFRqLp6kTJ2KI7Nohu4on0= 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-145-0dDRwXnOOuKc1eqkZ0EGjA-1; Wed, 04 Nov 2020 04:32:06 -0500 X-MC-Unique: 0dDRwXnOOuKc1eqkZ0EGjA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BA107186DD3A; Wed, 4 Nov 2020 09:32:05 +0000 (UTC) Received: from redhat.com (ovpn-115-26.ams2.redhat.com [10.36.115.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D14885C5FD; Wed, 4 Nov 2020 09:31:59 +0000 (UTC) Date: Wed, 4 Nov 2020 09:31:55 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Jason Wang Subject: Re: [RFC PATCH 0/6] eBPF RSS support for virtio-net Message-ID: <20201104093155.GB565323@redhat.com> References: <20201102185115.7425-1-andrew@daynix.com> <0164a42f-4542-6f3e-bd71-3319dfaae190@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/03 00:03:41 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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= 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 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. > 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. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|