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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,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 E6C87C433E0 for ; Tue, 9 Feb 2021 03:41:04 +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 6914F64EAA for ; Tue, 9 Feb 2021 03:41:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6914F64EAA 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]:54918 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l9Jtf-0000kU-CT for qemu-devel@archiver.kernel.org; Mon, 08 Feb 2021 22:41:03 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:38804) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l9JsV-0000HR-T0 for qemu-devel@nongnu.org; Mon, 08 Feb 2021 22:39:51 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:37096) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l9JsS-0000Ex-F5 for qemu-devel@nongnu.org; Mon, 08 Feb 2021 22:39:51 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612841985; 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=+NR/DK+697iUmLTOvImR8XJJHnABoPxTEmPcebkSyyI=; b=WSryHBPoPVfVzn9/7AnslKVCWdVO48OyaWETj5ssczJElbe8RoW4z5LWRV9t6S+0TD1TdE B7PgBuyVHN56lxRnepKA9F3Tq1qz9JLT1kT977RHmb2sY9daY/St4KHuzn4GYR0ZSpZuNU vNRruR+v08ho/MsJnF10hFXu0QZsM7U= 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-256-w11LaUtUM2qom5iKtMX1vg-1; Mon, 08 Feb 2021 22:39:43 -0500 X-MC-Unique: w11LaUtUM2qom5iKtMX1vg-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 DBB42108C303; Tue, 9 Feb 2021 03:39:42 +0000 (UTC) Received: from [10.72.13.32] (ovpn-13-32.pek2.redhat.com [10.72.13.32]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4B89610013D7; Tue, 9 Feb 2021 03:39:38 +0000 (UTC) Subject: Re: [PATCH 3/3] virtio-net: graceful fallback to vhost=off for tap netdev To: Yuri Benditovich References: <20210204202915.15925-1-yuri.benditovich@daynix.com> <20210204202915.15925-4-yuri.benditovich@daynix.com> <20210205083742-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: Date: Tue, 9 Feb 2021 11:39:36 +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: 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-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.57, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.265, 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 , qemu-devel@nongnu.org, "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2021/2/9 上午3:46, Yuri Benditovich wrote: > On Mon, Feb 8, 2021 at 5:15 AM Jason Wang wrote: >> >> On 2021/2/5 下午9:38, Michael S. Tsirkin wrote: >>> On Thu, Feb 04, 2021 at 10:29:15PM +0200, Yuri Benditovich wrote: >>>> Currently virtio-net silently clears features if they are >>>> not supported by respective vhost. This may create migration >>>> problems in future if vhost features on the source and destination >>>> are different. Implement graceful fallback to no-vhost mode >>>> when some acked features contradict with vhost. The decision is >>>> taken on set_features call and the vhost will be disabled >>>> till next reset (or migration). >>>> Such fallback is currently enabled only for TAP netdev. >>>> >>>> Signed-off-by: Yuri Benditovich >>> Sounds good, but I don't think we should do this if >>> vhostforce=on is set. >> >> If we do this, does it mean we won't maintain migration compatibility >> when vhostforce is on? > AFAIU, the 'vhostforce=on' should mean the vhost can't be disabled (if > I'm not mistaken this is typically used for vhost-user). > So we can view this case as similar to vhost-vdpa and vhost-user. Right, but since it was used by libivrt. Then it turns out to be a compatibility breaker. Thanks > >> Thanks >> >> >>> Also, let's document this behaviour with the vhost option so people >>> are not suprized. >>>