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=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 E0643C433DB for ; Fri, 15 Jan 2021 18:25:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AAB3C23359 for ; Fri, 15 Jan 2021 18:25:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388197AbhAOSZS (ORCPT ); Fri, 15 Jan 2021 13:25:18 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:47892 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388047AbhAOSZR (ORCPT ); Fri, 15 Jan 2021 13:25:17 -0500 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 10FICwr3086890; Fri, 15 Jan 2021 13:24:21 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : message-id : reply-to : references : mime-version : content-type : in-reply-to : subject; s=pp1; bh=+ryAA7tFRy7NpZrkGCvfEnNHPOAC3BE2pscL10x1U4M=; b=RjGNuYJjBsCPkeLc+SlkRKDxB7fPTDsaH3IK/f+8aydsHnoEHbUp+t7HLs7AeUMIRfA5 DBfZHuv9Xr+NGOFSaszn1n8p9daaE8IYpSjKi+hmAbl1TumjRMiysObOGn78rUKp7H2A Esp5dNWqNQt1YRe6PVZmSfgFL4AmnvKikD+KVlrPdla6pCoxk5XjiL8RF3ignHfJa70N FutuCwqcEJ91Cr6zuDbjU/M9CsjPsUghtvl+et7ECc/ZFRBVrxq8Gx3s+ozVz+3TkYKG Bp9QFY9PapL9jPVtG1heCXOMRJw9ePQi8Ep0zTmt3QBWOQMe8YZqIjas14WI83eji/MH yA== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 363g4k88q8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 15 Jan 2021 13:24:20 -0500 Received: from m0098413.ppops.net (m0098413.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 10FIETtV090047; Fri, 15 Jan 2021 13:24:20 -0500 Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 363g4k88p7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 15 Jan 2021 13:24:20 -0500 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 10FIDUOh022500; Fri, 15 Jan 2021 18:24:18 GMT Received: from b06avi18626390.portsmouth.uk.ibm.com (b06avi18626390.portsmouth.uk.ibm.com [9.149.26.192]) by ppma03ams.nl.ibm.com with ESMTP id 35y448003h-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 15 Jan 2021 18:24:18 +0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 10FIOAHB28967230 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 15 Jan 2021 18:24:10 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 69200A4062; Fri, 15 Jan 2021 18:24:15 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BBBF3A4069; Fri, 15 Jan 2021 18:24:10 +0000 (GMT) Received: from ram-ibm-com.ibm.com (unknown [9.160.82.178]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Fri, 15 Jan 2021 18:24:10 +0000 (GMT) Date: Fri, 15 Jan 2021 10:24:07 -0800 From: Ram Pai To: "Dr. David Alan Gilbert" Cc: Christian Borntraeger , Cornelia Huck , Halil Pasic , Greg Kurz , pair@us.ibm.com, brijesh.singh@amd.com, kvm@vger.kernel.org, "Michael S. Tsirkin" , qemu-devel@nongnu.org, frankja@linux.ibm.com, david@redhat.com, mdroth@linux.vnet.ibm.com, David Gibson , thuth@redhat.com, Eduardo Habkost , Richard Henderson , qemu-s390x@nongnu.org, rth@twiddle.net, berrange@redhat.com, Marcelo Tosatti , qemu-ppc@nongnu.org, pbonzini@redhat.com Message-ID: <20210115182407.GA24076@ram-ibm-com.ibm.com> Reply-To: Ram Pai References: <20201218124111.4957eb50.cohuck@redhat.com> <20210104071550.GA22585@ram-ibm-com.ibm.com> <20210104134629.49997b53.pasic@linux.ibm.com> <20210104184026.GD4102@ram-ibm-com.ibm.com> <20210105115614.7daaadd6.pasic@linux.ibm.com> <20210105204125.GE4102@ram-ibm-com.ibm.com> <20210111175914.13adfa2e.cohuck@redhat.com> <20210113124226.GH2938@work-vm> <6e02e8d5-af4b-624b-1a12-d03b9d554a41@de.ibm.com> <20210114103643.GD2905@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210114103643.GD2905@work-vm> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 Subject: RE: [for-6.0 v5 11/13] spapr: PEF: prevent migration X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343,18.0.737 definitions=2021-01-15_09:2021-01-15,2021-01-15 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 mlxlogscore=999 priorityscore=1501 bulkscore=0 adultscore=0 lowpriorityscore=0 impostorscore=0 malwarescore=0 spamscore=0 mlxscore=0 suspectscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101150106 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Jan 14, 2021 at 10:36:43AM +0000, Dr. David Alan Gilbert wrote: > * Christian Borntraeger (borntraeger@de.ibm.com) wrote: > > > > > > On 13.01.21 13:42, Dr. David Alan Gilbert wrote: > > > * Cornelia Huck (cohuck@redhat.com) wrote: > > >> On Tue, 5 Jan 2021 12:41:25 -0800 > > >> Ram Pai wrote: > > >> > > >>> On Tue, Jan 05, 2021 at 11:56:14AM +0100, Halil Pasic wrote: > > >>>> On Mon, 4 Jan 2021 10:40:26 -0800 > > >>>> Ram Pai wrote: > > >> > > >>>>> The main difference between my proposal and the other proposal is... > > >>>>> > > >>>>> In my proposal the guest makes the compatibility decision and acts > > >>>>> accordingly. In the other proposal QEMU makes the compatibility > > >>>>> decision and acts accordingly. I argue that QEMU cannot make a good > > >>>>> compatibility decision, because it wont know in advance, if the guest > > >>>>> will or will-not switch-to-secure. > > >>>>> > > >>>> > > >>>> You have a point there when you say that QEMU does not know in advance, > > >>>> if the guest will or will-not switch-to-secure. I made that argument > > >>>> regarding VIRTIO_F_ACCESS_PLATFORM (iommu_platform) myself. My idea > > >>>> was to flip that property on demand when the conversion occurs. David > > >>>> explained to me that this is not possible for ppc, and that having the > > >>>> "securable-guest-memory" property (or whatever the name will be) > > >>>> specified is a strong indication, that the VM is intended to be used as > > >>>> a secure VM (thus it is OK to hurt the case where the guest does not > > >>>> try to transition). That argument applies here as well. > > >>> > > >>> As suggested by Cornelia Huck, what if QEMU disabled the > > >>> "securable-guest-memory" property if 'must-support-migrate' is enabled? > > >>> Offcourse; this has to be done with a big fat warning stating > > >>> "secure-guest-memory" feature is disabled on the machine. > > >>> Doing so, will continue to support guest that do not try to transition. > > >>> Guest that try to transition will fail and terminate themselves. > > >> > > >> Just to recap the s390x situation: > > >> > > >> - We currently offer a cpu feature that indicates secure execution to > > >> be available to the guest if the host supports it. > > >> - When we introduce the secure object, we still need to support > > >> previous configurations and continue to offer the cpu feature, even > > >> if the secure object is not specified. > > >> - As migration is currently not supported for secured guests, we add a > > >> blocker once the guest actually transitions. That means that > > >> transition fails if --only-migratable was specified on the command > > >> line. (Guests not transitioning will obviously not notice anything.) > > >> - With the secure object, we will already fail starting QEMU if > > >> --only-migratable was specified. > > >> > > >> My suggestion is now that we don't even offer the cpu feature if > > >> --only-migratable has been specified. For a guest that does not want to > > >> transition to secure mode, nothing changes; a guest that wants to > > >> transition to secure mode will notice that the feature is not available > > >> and fail appropriately (or ultimately, when the ultravisor call fails). > > >> We'd still fail starting QEMU for the secure object + --only-migratable > > >> combination. > > >> > > >> Does that make sense? > > > > > > It's a little unusual; I don't think we have any other cases where > > > --only-migratable changes the behaviour; I think it normally only stops > > > you doing something that would have made it unmigratable or causes > > > an operation that would make it unmigratable to fail. > > > > I would like to NOT block this feature with --only-migrateable. A guest > > can startup unprotected (and then is is migrateable). the migration blocker > > is really a dynamic aspect during runtime. > > But the point of --only-migratable is to turn things that would have > blocked migration into failures, so that a VM started with > --only-migratable is *always* migratable. I believe, the proposed behavior, does follow the above rule. The VM started with --only-migratable will always be migratable. Any behavior; in the guest, to the contrary will disallow the behavior or terminate the guest, but will never let the VM transition to a non-migratable state. RP