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=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 AAE45C433B4 for ; Fri, 2 Apr 2021 05:06:25 +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 203BE610F8 for ; Fri, 2 Apr 2021 05:06:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 203BE610F8 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]:33680 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lSC0m-00071W-2z for qemu-devel@archiver.kernel.org; Fri, 02 Apr 2021 01:06:24 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:36660) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lSBzt-0006aq-GP for qemu-devel@nongnu.org; Fri, 02 Apr 2021 01:05:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:32303) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lSBzp-0001BF-Hm for qemu-devel@nongnu.org; Fri, 02 Apr 2021 01:05:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1617339923; 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=U+vDFOVXELt5FPqU2eIBoJhRC27AD7c/qDE8JANf2lg=; b=gYc8iHLApDk21p+lw7eulZKOqK2gFMTiRKrc6WJx6qvqcWM1ERoXZ8tmZ2DsMoM5Hy/yCb DHyaV71+omEYXKOJlT1hWiqPIet2h2UjNlSuwXcg9ZzHr3qq4vIkK63YbLtk2EYhuQigzW nNwXyCdB5B0pTVYEhn8O8wMzIDU3Mrg= 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-133-U5MznYnSNzy9g6omb_P44Q-1; Fri, 02 Apr 2021 01:05:21 -0400 X-MC-Unique: U5MznYnSNzy9g6omb_P44Q-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 4B83E1005D5A; Fri, 2 Apr 2021 05:05:20 +0000 (UTC) Received: from wangxiaodeMacBook-Air.local (ovpn-12-24.pek2.redhat.com [10.72.12.24]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3E92C5F9C5; Fri, 2 Apr 2021 05:05:11 +0000 (UTC) Subject: Re: [RFC PATCH v2 0/3] virtio-net: graceful drop of vhost for TAP From: Jason Wang To: Yuri Benditovich References: <20210322122452.369750-1-yuri.benditovich@daynix.com> Message-ID: Date: Fri, 2 Apr 2021 13:05:10 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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 Received-SPF: pass client-ip=216.205.24.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, 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: , Cc: Yan Vugenfirer , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , qemu-devel@nongnu.org, "Michael S . Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 在 2021/3/26 下午5:18, Jason Wang 写道: >>> ? >> I assume that  both src and dest started with vhost=on. >> >> As driver B supports both packed and split, you can switch from driver >> A to driver B after migration >> and driver B will work with split. Exactly as it does today. >> >> The key question is what is more important - vhost or features that >> vhost does not support? >> current code says: vhost is more important always >> v1 patch says: features are more important always. >> v2 patch says: vhost is more important at init time, features are more >> important at migration time. >> Because we are able to drop vhost but we can't drop features when we >> have a running driver. >> Do you agree? > > > I think what came from cli is the most important. So if I understand > correclty: > > - vhost=on means "turn on vhost when possible" it implies that > fallback is allowed (we had already had fallback codes) > - vhostforce=on means "turn on vhost unconditonally" it implies that > we can't do fallback > > So my understanding is that: > > - "vhost=on, packed=on", we can fallback to userspace but must keep > packed virtqueue works > - "vhost=on,vhostforce=on,packed=on", we can't fallback and must keep > both vhost and packed virtqueue work, if we can't we need to fail > > Thanks Daniel and Michael, am I right here? We need some inputs to move forward to fix the migration compatibility issue. Thanks