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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 4D5DAC433DB for ; Thu, 18 Mar 2021 11:34:58 +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 92A2F64E99 for ; Thu, 18 Mar 2021 11:34:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 92A2F64E99 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]:51296 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lMqvY-0004KC-Ci for qemu-devel@archiver.kernel.org; Thu, 18 Mar 2021 07:34:56 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44672) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lMqs7-0002ZZ-M8 for qemu-devel@nongnu.org; Thu, 18 Mar 2021 07:31:25 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:31409) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lMqs2-0002fv-Fe for qemu-devel@nongnu.org; Thu, 18 Mar 2021 07:31:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616067076; 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=+ysM6uPvCTnBFvFlgfILPpEME73b7cXiBO8cNe3ntmI=; b=gv0QeJEE6QJ4rN7bESlvRRdPq2gEyTqkaawyXdjTTC9L4YDYfLrvVOkxlcCyxcfPTRoeho pQkuf7zzdwtvgVl5VydnnJh+MtoVYT/w/YD47CPrWYGsdsOFZ9FZYZ3rsxTFaWATNpxUMW kAx0TNkadwZCI4Mrmz3ugn/CZ4/14v8= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-354-n0zuLgtYNLW47yeJ8y4NWg-1; Thu, 18 Mar 2021 07:31:14 -0400 X-MC-Unique: n0zuLgtYNLW47yeJ8y4NWg-1 Received: by mail-wr1-f70.google.com with SMTP id f3so19949386wrt.14 for ; Thu, 18 Mar 2021 04:31:14 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=+ysM6uPvCTnBFvFlgfILPpEME73b7cXiBO8cNe3ntmI=; b=pDkUXFmjJ5QT+Js4kvKBHq7MBq+yszCzz1y1diwZWvuTbrYuXL0ixAqycQG/YXNGmt IumNB5gzlTt2QrCxuno91eR7oqE6/nx3q0OPeHDzraGdU/BsQSru5Cs/A7696EFUbv2f Lb9ih6N1lSj/zToni9zOXK+XSZiRdfV8jOLJw79gUQIeIZ+DFK3lCqBvm7Md9ZqEOmG9 dUroN8jo+bEsDAhM0uoZBBwdP0GL8JVGgEl81aj9n1MRVdJ31FqCy7SKovHUdIdonxtc j/INfX0PbEe0LYpcauGWJdSwsqGylSidcwnSeUpUuOFh1XSeCOHNtf/onqphWcCnzOjm HZTw== X-Gm-Message-State: AOAM533BTKdupwApzFjtRyg82S3UBwJNBlJf8cktbhA9uIXTsJjw5xUA Em4f7xsLFiejTW5mdLiPBdC9HelVhyeWEWfm/6uUeZy0fxdSey2AfwsU3dc9XaamyhRShe5qZGF Qee45kxx6zz5m4t8= X-Received: by 2002:a5d:538d:: with SMTP id d13mr9349462wrv.92.1616067073628; Thu, 18 Mar 2021 04:31:13 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxBtyXngtfdfe4a3ao469XeAfdS3Vamiu9M9YqQBz3uMFREzDyznGqm9VT169ExwqNnVLyncg== X-Received: by 2002:a5d:538d:: with SMTP id d13mr9349439wrv.92.1616067073452; Thu, 18 Mar 2021 04:31:13 -0700 (PDT) Received: from [192.168.1.36] (17.red-88-21-201.staticip.rima-tde.net. [88.21.201.17]) by smtp.gmail.com with ESMTPSA id p17sm1886330wmq.47.2021.03.18.04.31.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 18 Mar 2021 04:31:13 -0700 (PDT) Subject: Re: [PATCH v2 3/3] target/arm: Restrict v7A TCG cpus to TCG accel To: Peter Maydell , Andrew Jones References: <20210221222617.2579610-1-f4bug@amsat.org> <20210221222617.2579610-4-f4bug@amsat.org> <8a302c84-b69c-b0c2-de45-607dd1f686a6@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <28540fd5-3bd3-30d7-624d-da21d0f39806@redhat.com> Date: Thu, 18 Mar 2021 12:31:12 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=philmd@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=-0.249, 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=unavailable 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: qemu-arm , =?UTF-8?Q?Alex_Benn=c3=a9e?= , Claudio Fontana , "Dr. David Alan Gilbert" , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/18/21 12:21 PM, Peter Maydell wrote: > On Thu, 18 Mar 2021 at 11:09, Philippe Mathieu-Daudé wrote: >> Still, I'm not sure it makes sense. If you want to migrate a such >> machine, KVM can not virtualize it, so you'll be forced to use TCG >> right? In that case cpu_tcg is built in and you have the A15. >> >> IOW the problem is not this patch, it is that since 82bf7ae84ce we >> can not migrate A15. > > Do you mean "we can't migrate a TCG A15" ? That would be a problem. No problem here. > Or do you mean "we can't migrate a KVM A15" ? That's entirely > expected when we drop support for KVM A15 :-) Yes, this is why I mentioned this is mostly a problem for downstream distributions. > Or do you mean "migration from KVM to TCG doesn't work?" That's > a pre-existing thing I don't expect to work (we don't put anything > in to stop it working, but I'm pretty sure there will be a bunch > of things that mean it doesn't in practice work.) > >> So we need both 1/ revert 82bf7ae84ce and 2/ be sure the kernel >> support 32-bit host... Am I missing something? > > We're definitely not reverting 82bf7ae84ce if we can avoid it... I tend to agree. The problem is for the running VMs started before 82bf7ae84ce (so up to any fork based on v5.2). I don't know what the forks are supposed to do with the running VMs if they want to migrate them to newer QEMU (or upgrade the host QEMU). I don't expect a guest being happy and reliable if we underneath change its CPU by another one while migrating it... KVM to TCG is not tested much indeed, and I don't think the performance impact will be well accepted :)