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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 6F4FFC433E1 for ; Mon, 17 Aug 2020 10:28:46 +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 3E22D20738 for ; Mon, 17 Aug 2020 10:28:46 +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="dhsaLhpm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E22D20738 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]:53306 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k7cNh-0008QH-Gy for qemu-devel@archiver.kernel.org; Mon, 17 Aug 2020 06:28:45 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39050) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k7cN1-0007yF-EG for qemu-devel@nongnu.org; Mon, 17 Aug 2020 06:28:03 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:22959) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1k7cMy-0000AF-Jq for qemu-devel@nongnu.org; Mon, 17 Aug 2020 06:28:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597660078; 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=5t4AMbi3BwtliqZ1VzYEVSDte52IZZWnAjRAQoK0j1g=; b=dhsaLhpmVIjo8MZWmB4J2HjjbP8WxxDfnoYdERsDDOcKcmzBWDYdbGCkQ1Z8Hs6GA11Nq4 HnWAUZtaojteqw+m7YcOa1lZmlIOwusG2vXIkfsOfPHKUl/l3j0s1GTdd0D3W73K2TN6vA MJi+siFZjtHUkT54Von0U9EOPouAL2A= 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-558-shrARw0MObajYwjTRrt5eA-1; Mon, 17 Aug 2020 06:27:57 -0400 X-MC-Unique: shrARw0MObajYwjTRrt5eA-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 456C0807338; Mon, 17 Aug 2020 10:27:56 +0000 (UTC) Received: from gondolin (ovpn-112-230.ams2.redhat.com [10.36.112.230]) by smtp.corp.redhat.com (Postfix) with ESMTP id E630410027AB; Mon, 17 Aug 2020 10:27:48 +0000 (UTC) Date: Mon, 17 Aug 2020 12:27:46 +0200 From: Cornelia Huck To: Stefano Garzarella Subject: Re: virtio-vsock requires 'disable-legacy=on' in QEMU 5.1 Message-ID: <20200817122746.0b786372.cohuck@redhat.com> In-Reply-To: <20200813120415.s5we6mihe6fywm4a@steredhat.lan> References: <20200813112820.62ffd63e.cohuck@redhat.com> <20200813102430.vjnc56anqjaxn4tw@steredhat.lan> <20200813123737.25ba11d2.cohuck@redhat.com> <20200813120415.s5we6mihe6fywm4a@steredhat.lan> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=cohuck@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/17 01:24:49 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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: Halil Pasic , Qinghua Cheng , qemu devel list , Stefan Hajnoczi , "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, 13 Aug 2020 14:04:15 +0200 Stefano Garzarella wrote: > On Thu, Aug 13, 2020 at 12:37:37PM +0200, Cornelia Huck wrote: > > On Thu, 13 Aug 2020 12:24:30 +0200 > > Stefano Garzarella wrote: > > > > > On Thu, Aug 13, 2020 at 11:28:20AM +0200, Cornelia Huck wrote: > > > > We basically have three possible ways to deal with this: > > > > > > > > - Force it to modern (i.e., what you have been doing; would need the > > > > equivalent changes in ccw as well.) > > > > > > Oo, thanks for pointing out ccw! > > > I don't know ccw well, in this case should we set dev->max_rev to 1 or 2 > > > to force to modern? > > > > No, ->max_rev is the wrong side of the limit :) You want > > Well :-) Thanks! > > > > > ccw_dev->force_revision_1 = true; > > > > in _instance_init() (see e.g. virtio-ccw-gpu.c). > > > > > > > > > Pro: looks like the cleanest approach. > > > > Con: not sure if we would need backwards compatibility support, > > > > which looks hairy. > > > > > > Not sure too. > > > > Yes, I'm not sure at all how to handle user-specified values for > > legacy/modern. Thinking a bit more about it, I'm not sure whether we even *can* provide backwards compatibility: we have different autoconfigurations for PCI based upon where it is plugged, and ccw does not have a way to turn legacy on/off, except from within the code. > > > > > > > > > - Add vsock to the list of devices with legacy support. > > > > Pro: Existing setups continue to work. > > > > Con: If vsock is really virtio-1-only, we still carry around > > > > possibly broken legacy support. > > > > > > I'm not sure it is virtio-1-only, but virtio-vsock was introduced in > > > 2016, so I supposed it is modern-only. > > > > Yes, I would guess so as well. > > > > > > > > How can I verify that? Maybe forcing legacy mode and run some tests. > > > > Probably yes. The likeliest area with issues is probably endianness, so > > maybe with something big endian in the mix? > > > > Yeah, I'll try this setup! > > > > > > > > - Do nothing, have users force legacy off. Bad idea, as ccw has no way > > > > to do that on the command line. > > > > > > > > The first option is probably best. The first option is now "force modern, but with no backwards compatibility", which is not that great; but "allow legacy, even though it should not exist" is not particularly appealing, either... what a mess :( > > > > > > > > > > Yeah, I agree with you! > > > > Yes, it's really a pity we only noticed this after the release; this > > was supposed to stop new devices with legacy support creeping in, not > > to break existing command lines :( > > > > Yes, I forgot to test vsock stuff before the release :-( > Maybe we should add some tests... Speaking of tests: do you have a quick way to test vhost-vsock at hand? Maybe I should add it to my manual repertoire...