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[209.51.188.17]) by mx.google.com with ESMTPS id u1si2304384ybk.9.2021.02.03.03.00.41 for (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Wed, 03 Feb 2021 03:00:41 -0800 (PST) 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=fail header.i=@redhat.com header.s=mimecast20190719 header.b=jBgE+C4q; 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=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from localhost ([::1]:41166 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l7Fto-0007H5-Iy for alex.bennee@linaro.org; Wed, 03 Feb 2021 06:00:40 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:46936) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l7Fsv-0007Gq-SW for qemu-arm@nongnu.org; Wed, 03 Feb 2021 05:59:45 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:31456) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l7Fss-00060n-Ml for qemu-arm@nongnu.org; Wed, 03 Feb 2021 05:59:45 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612349980; 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=Cberw22i4OyXhCOwhlnp5X3G0td/WRmeYu0FOAInees=; b=jBgE+C4q7IZo5qqfVXP+8z5oJOLFcoIJV3YVHtZyK0EO9G33FPFW5dU67MUeD+Sirtuc2p zuL9XSlkWmgxJCJvRKR00a91bdCTMPs7nV8Eu98BVohVD7j+DhCvlVClF9i6IBjVd1z22s 53ueRAqFIJKk8Ag41tCnTdwPDnbDbw0= 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-382-94kmtrLMNSiqgub7m-jv_A-1; Wed, 03 Feb 2021 05:59:39 -0500 X-MC-Unique: 94kmtrLMNSiqgub7m-jv_A-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 25374C7402; Wed, 3 Feb 2021 10:59:38 +0000 (UTC) Received: from work-vm (ovpn-115-70.ams2.redhat.com [10.36.115.70]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 724DE4D; Wed, 3 Feb 2021 10:59:36 +0000 (UTC) Date: Wed, 3 Feb 2021 10:59:33 +0000 From: "Dr. David Alan Gilbert" To: Peter Maydell Subject: Re: ARM Snapshots Not Backwards-Compatible Message-ID: <20210203105933.GF2950@work-vm> References: <153e5c54-f8bf-d088-502d-502309f5d2a6@redhat.com> <20210203102758.GC2950@work-vm> <20210203104920.GE2950@work-vm> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.386, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-arm@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrew Jones , Juan Quintela , QEMU Developers , Aaron Lindsay , qemu-arm , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Errors-To: qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org Sender: "Qemu-arm" X-TUID: YPO8fFYKQPS4 * Peter Maydell (peter.maydell@linaro.org) wrote: > On Wed, 3 Feb 2021 at 10:49, Dr. David Alan Gilbert wrote: > > > > * Peter Maydell (peter.maydell@linaro.org) wrote: > > > On Wed, 3 Feb 2021 at 10:28, Dr. David Alan Gilbert wrote: > > > > > > > > * Philippe Mathieu-Daudé (philmd@redhat.com) wrote: > > > > > Cc'ing migration team and qemu-arm@ list. > > > > > > > > I'll have to leave the detail of that to the ARM peole; but from a > > > > migration point of view I think we do want the 64 bit ARM migrations to > > > > be stable now. Please tie incompatible changes to machine types. > > > > > > That is the intention, but because there's no upstream testing > > > of migration compat, we never notice if we get it wrong. > > > What is x86 doing to keep cross-version migration working ? > > > > I know there used to be some of our team running Avocado tests for > > compatibility regularly, I'm not sure of the current status. > > It's something we also do regularly around when we do downstream > > releases, so we tend to catch them then, although even on x86 that > > often turns out to be a bit late. > > So downstream testing only? I thought there used to be some regular avocado testing of upstream but I'm not sure if it's all architectures and I'm not sure if it's still happening; I haven't seen any migration issues from it for a while, which makes me think it isn't. > I think that unless we either (a) start > doing migration-compat testing consistently upstream or (b) RedHat or > some other downstream start testing and reporting compat issues > to us for aarch64 as they do for x86-64, in practice we're just > not going to have working migration compat despite our best > intentions. (None of the issues Aaron raises were deliberate > compat breaks -- they're all "we made a change we didn't think > affected migration but it turns out that it does".) I'd agree; we still hit this too often on x86 as well. Dave > thanks > -- PMM > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK