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=-2.2 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 DADD2C4360C for ; Fri, 27 Sep 2019 09:14:05 +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 A49322146E for ; Fri, 27 Sep 2019 09:14:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A49322146E 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]:48340 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iDmKC-0002oU-Jf for qemu-devel@archiver.kernel.org; Fri, 27 Sep 2019 05:14:04 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54695) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iDmFf-0006d0-Or for qemu-devel@nongnu.org; Fri, 27 Sep 2019 05:09:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iDmFa-0001hi-CM for qemu-devel@nongnu.org; Fri, 27 Sep 2019 05:09:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46818) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iDmFa-0001ea-6Y for qemu-devel@nongnu.org; Fri, 27 Sep 2019 05:09:18 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A7D613071549; Fri, 27 Sep 2019 09:09:13 +0000 (UTC) Received: from redhat.com (ovpn-112-55.ams2.redhat.com [10.36.112.55]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 238EB196B2; Fri, 27 Sep 2019 09:09:07 +0000 (UTC) Date: Fri, 27 Sep 2019 10:09:05 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Eduardo Habkost Subject: Re: [PATCH] i386: Re-add "pconfig" CPUID flag name Message-ID: <20190927090905.GC20911@redhat.com> References: <20190926212326.4092-1-ehabkost@redhat.com> <20190927004220.GV8144@habkost.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190927004220.GV8144@habkost.net> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Fri, 27 Sep 2019 09:09:13 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: thomas.lendacky@amd.com, "Kang, Luwei" , libvir-list@redhat.com, qemu-devel , Robert Hoo , kai.huang@intel.com, robert.hu@intel.com, Paolo Bonzini , Jiri Denemark , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Sep 26, 2019 at 09:42:20PM -0300, Eduardo Habkost wrote: > (CCing libvir-list) > > On Thu, Sep 26, 2019 at 11:58:30PM +0200, Paolo Bonzini wrote: > > Is this really needed? QEMU's value of pconfig=on vs. off should be > > provided by QMP CPU model queries, if a property is not available then > > Libvirt should not try to set it to off. > > > > Libvirt can easily work around it for new VMs, and it should. > > The issue are VMs that were created with QEMU 3.1.0. QEMU 3.1.0 > was telling libvirt "Icelake-Server can't be used unless > pconfig=off is used", and libvirt was adding pconfig=off to the > domain XML as expected. > > It would be wrong for libvirt to remove a device option when > migrating an existing VM to another QEMU version. We can change > the rules (and document that), but do we want to? IIUC currently any existing VMs with Icelake-Server will *not* have pconfig present, since libvirt is going to set pconfig=off QEMU has now dropped pconfig CPUID entirely. If libvirt were to stop setting pconfig=off, then there is NO guest ABI change, so we'd be safe in that sense. I'll defer to Jiri on how we'd actually go about making that work in libvirt from a code POV. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|