From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by 2002:a17:907:2723:b0:a5a:9152:cbdc with SMTP id d3csp1105939ejl; Wed, 15 May 2024 21:12:00 -0700 (PDT) X-Forwarded-Encrypted: i=2; AJvYcCVudxU3o5cmMJAvBuinPD8U6bsDpiB8bnFaQosic5tKJtti0ZNOLg2W3yJxpjTuhW37wZ3DEBSLdfSWw/ZUCZiYCv+yy1nt X-Google-Smtp-Source: AGHT+IFyLhBbE8zKqWxYwY1M6M/lS1A/l+krvKI4lZhLgTCRJ80a5Ch57udB1MYte3NgutV/It4T X-Received: by 2002:a05:6214:3a05:b0:6a0:de8b:4bfb with SMTP id 6a1803df08f44-6a1683769a3mr184495986d6.45.1715832720580; Wed, 15 May 2024 21:12:00 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1715832720; cv=none; d=google.com; s=arc-20160816; b=GPC8ziuJZeGzxW2HB5uPonHBRwaSo8+bmNyoxo/bHR+z5w8O2LxR8J64Y53cvhkGPP kaUu9bm8CKjMglcjS1+Q5ZPKMuZf0piA+j89ZzFUaaa1tDNlq+gO91ZJ8crJl8sBiiRH InOIRRgAEMn3lBC7kL/FY4ZnF4KXBNvpmIn61oYFzJqGyDTM2I413v3sKR9b9mmJ9P9A eBg5pMzxs77Z4nAJKo0z4udNuACHTnL2hdMiTzl8rGVI7BrPtkr9nKwD41xF5jtUpbey KNIj+FBp/hbIYEjQ9QBm4G3zYXmse0PgZi1osddyTGsW+os1J8RpwQA48g951KHUzJq6 AqMw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=sender:errors-to:list-subscribe:list-help:list-post:list-archive :list-unsubscribe:list-id:precedence:content-transfer-encoding :content-disposition:in-reply-to:mime-version:references:message-id :subject:cc:to:from:date:dkim-signature; bh=RgsmUie6oNRshpsUHGjExxGQpjucuEvOk67Y+fIg6zY=; fh=7Tejv7yUirOc/WKFyXDSVq3i9rhiGvHfnxAoi16yfxk=; b=mfRK84Fsi/XH4daExqmGrw4XpNoPZ3mUxTYSFD9CEoSRlwFBR7uauOP5z5urTilgr+ LtESPuChS5PEn2z+y6GGjgxAd4qi9tlG9+lpuKdf65fuh7Rfp3yuJdvFUo/0VipN3cw2 kvbmQaL6bNtId5mFtBnIDxQPZdJ42ZZTiFrSFb+b5Ms/Enxof3AuqrVuy2rXSmHCNUT9 482awbbodi0j124JJ4ImtnQ5XWHZv1bS64Xkn4M3UnC6DUYudGWPIoZAvkSDp1cUQTrj H0hFrldr9Tlrra9cw40gBFFptqaDtr7gGxdDVlXOG6bbvlLz17PmpZVOtPUry/0NWEW+ JkQQ==; dara=google.com ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=TdyQFTuH; spf=pass (google.com: domain of qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom="qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org. [209.51.188.17]) by mx.google.com with ESMTPS id 6a1803df08f44-6a15f29a71asi158640426d6.238.2024.05.15.21.12.00 for (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Wed, 15 May 2024 21:12:00 -0700 (PDT) Received-SPF: pass (google.com: domain of qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=TdyQFTuH; spf=pass (google.com: domain of qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom="qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1s7SSx-0001aj-13; Thu, 16 May 2024 00:11:39 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1s7SSv-0001aG-4M for qemu-arm@nongnu.org; Thu, 16 May 2024 00:11:37 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1s7SSt-0003ZY-AQ for qemu-arm@nongnu.org; Thu, 16 May 2024 00:11:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1715832694; 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=RgsmUie6oNRshpsUHGjExxGQpjucuEvOk67Y+fIg6zY=; b=TdyQFTuHB8IR5GCmJ60Fc8ZZJuJCQ7OChD3+o6sPNpJvv89yzXV706E2FgNPTSZFVIJHmX mTx78/XGrTwviEy/fLy5pOYFqMjkKWFGHNaMMXNGL3BWMTMsDyqZGAU2DmWnjV4kUkTKDA AZJ3VL4tMxyzqE+iQkoLIa4OPWb+dk4= Received: from mail-pj1-f70.google.com (mail-pj1-f70.google.com [209.85.216.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-250-m5vQzpVuNbSU60qrMj5TkA-1; Thu, 16 May 2024 00:11:17 -0400 X-MC-Unique: m5vQzpVuNbSU60qrMj5TkA-1 Received: by mail-pj1-f70.google.com with SMTP id 98e67ed59e1d1-2b8a9cd19e9so615441a91.1 for ; Wed, 15 May 2024 21:11:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1715832676; x=1716437476; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=RgsmUie6oNRshpsUHGjExxGQpjucuEvOk67Y+fIg6zY=; b=UyrbvXO+yRCirvkL700/TFftFgTaza1B1jIjFYdghRrpi8RExa5sggwqSPRcG8EhFn tOTlC3FiiXtCWbNoXv2zqrMqS6+Cy+eQg5xVOWbqmjlvwttQeg6XaH/dC70D40b0AWPs 3XpcVwd6Iuv5tFAkBDr1yVuo4es+A7UPQMDxS7uvVuz1AO1VV9h0B1zIUz6uyY2lNfvO Op9NhPRcB5iCoFKRX3vVXfBExAw7HIQyt/fPk2+v4uuMW3Dv8d8a7KZqrlMOVFt57ILy 8QDO5pf2k9cJS3YPuosKRMGcjlcOjT7sIVPpNduLMX741rXkP63fc0SoTsa0lvOI4cB5 6apQ== X-Forwarded-Encrypted: i=1; AJvYcCVw3FkbrSwTj+Js7j+duW7/j/NssQ11niSI8mVrZgVN+EYIk40XyzVtkQQK6NJEHtHU7aeV+Bpr2Mxc4k27NWNiUneJ X-Gm-Message-State: AOJu0YzxkPPgFzp4p88Yst8X3u7PiyQdHFYDNBb3pLu0NvSvRRbAzT/W 27DLVedKQFgPQ/E0SrM1VHkzZECkj+EKx9qvVtLzyISL4CH2pOqWwE7O0/ac9yIwso8tPJhvvrV R/HdLnaGsxQjH2vLbbb49KcNtrncS+oTK37lRgIvNAxklD6kiyg== X-Received: by 2002:a05:6a20:4306:b0:1ad:8f18:8621 with SMTP id adf61e73a8af0-1afde28cf65mr20831436637.6.1715832676453; Wed, 15 May 2024 21:11:16 -0700 (PDT) X-Received: by 2002:a05:6a20:4306:b0:1ad:8f18:8621 with SMTP id adf61e73a8af0-1afde28cf65mr20831412637.6.1715832675762; Wed, 15 May 2024 21:11:15 -0700 (PDT) Received: from x1n ([67.214.252.166]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2b9f5820ce9sm1624392a91.56.2024.05.15.21.11.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 May 2024 21:11:15 -0700 (PDT) Date: Wed, 15 May 2024 22:11:12 -0600 From: Peter Xu To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: marcandre.lureau@redhat.com, qemu-devel@nongnu.org, Eduardo Habkost , "Michael S. Tsirkin" , Marcel Apfelbaum , Fiona Ebner , Paolo Bonzini , Richard Henderson , qemu-arm@nongnu.org, Peter Maydell , Fabiano Rosas , Gerd Hoffmann , Yanan Wang , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH v3 5/5] virtio-gpu: fix v2 migration Message-ID: References: <20240515141557.1277999-1-marcandre.lureau@redhat.com> <20240515141557.1277999-6-marcandre.lureau@redhat.com> MIME-Version: 1.0 In-Reply-To: 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=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.935, 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-arm@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org Sender: qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org X-TUID: Zyzlbspnv5jV On Wed, May 15, 2024 at 06:15:48PM +0100, Daniel P. Berrangé wrote: > On Wed, May 15, 2024 at 11:03:27AM -0600, Peter Xu wrote: > > On Wed, May 15, 2024 at 05:03:44PM +0100, Daniel P. Berrangé wrote: > > > Above all, I'm failing to see why there's a compelling reason > > > for virtio_gpu to diverge from our long standing practice of > > > adding a named property flag "virtio_scanout_vmstate_fix" > > > on the machine class, and then setting it in machine types > > > which need it. > > > > The reason to introduce that is definitely avoid introducing fields / > > properties in similar cases in which case all the fields may represent the > > same thing ("return true if MC is older than xxx version"). Especially > > when such change is not bound to a new feature so in which case it won't > > make sense to allow user to even control that propoerty, even if we > > exported this "x-virtio-scanout-fix" property, but now we must export it > > because compat fields require it. > > > > However I think agree that having upstream specific MC versions in VMSD > > checks is kind of unwanted. I think the major problem is we don't have > > that extra machine type abstract where we can have simply a number showing > > the release of QEMU, then we can map that number to whatever > > upstream/downstream machine types. E.g.: > > > > Release No. Upstream version Downstream version > > 50 9.0 Y.0 > > 51 9.1 > > 52 9.2 Y.1 > > ... > > Downstream versions do not map cleanly to individual upstream versions > across the whole code base. If we have two distinct features in upstream > version X, each of them may map to a different downstream release. > > This can happen when downstream skips one or more upstream releases. > One feature from the skipped release might be backported to an earlier > downstream release, while other feature might not arrive downstream > until they later rebase. Version based checks are an inherantly > undesirable idea for a situation where there is any backporting taking > place, whether its machine type versions or something else. Named feature > / flag based checks are always the way to go. I thought this should work better with things like this where we only want to fix a break in ABI, and none of downstream should special case things like such fix.. but I agree even with that in mind such case could be so rare to bother with above scheme. I could have raised a bad idea I suppose. :-( Let's stick with the simple until someone has better idea. Thanks, -- Peter Xu