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=-5.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 3B28CC433E0 for ; Thu, 14 Jan 2021 10:53:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F350723A3B for ; Thu, 14 Jan 2021 10:53:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727098AbhANKxQ (ORCPT ); Thu, 14 Jan 2021 05:53:16 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:9700 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726382AbhANKxO (ORCPT ); Thu, 14 Jan 2021 05:53:14 -0500 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 10EAYtxb026207; Thu, 14 Jan 2021 05:52:19 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=FFtO+uKIgOmZPjSZlzoH6HGGbCGeEqZlRe/CtrBB5NI=; b=cWUdhOgrvZsG4FNm/2TdCffpLVbG1JVLEIqA2CYDYF3G33KLwkjvdjTNjVDg+jNLtkCx /InisZGfNoZtDXF9/oeVTeDQy/IghNuHHVxe/P49oDoZmeIaOG8lNXb3mauIU8fLLiZw EVlGb4FdQTdh7qrriR8r7ijo6OXiFX2pZPy8i0YRGj22pyWzqki5J45nm/hqHJbqkxP2 fuLVGQ3H4vcxo7nzmWL8v3VIs/0vvRXseBNV/OFBzto5uXPWLOIGNjkE1V6uaOMRU4N7 jAGuUIV+QLAm9mRNK1avnbjj2JfuPCbEMyLDn2FDpns5f6PRw8KZj7fogJO6Zq1msJgz Ug== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 362kvghb9h-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 14 Jan 2021 05:52:19 -0500 Received: from m0098409.ppops.net (m0098409.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 10EAa7se031870; Thu, 14 Jan 2021 05:52:18 -0500 Received: from ppma02fra.de.ibm.com (47.49.7a9f.ip4.static.sl-reverse.com [159.122.73.71]) by mx0a-001b2d01.pphosted.com with ESMTP id 362kvghb8u-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 14 Jan 2021 05:52:18 -0500 Received: from pps.filterd (ppma02fra.de.ibm.com [127.0.0.1]) by ppma02fra.de.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 10EAkq6b031387; Thu, 14 Jan 2021 10:52:16 GMT Received: from b06avi18626390.portsmouth.uk.ibm.com (b06avi18626390.portsmouth.uk.ibm.com [9.149.26.192]) by ppma02fra.de.ibm.com with ESMTP id 35y448k8ct-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 14 Jan 2021 10:52:16 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 10EAq8xg25428350 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 14 Jan 2021 10:52:08 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2F9784C044; Thu, 14 Jan 2021 10:52:13 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D9AA74C046; Thu, 14 Jan 2021 10:52:11 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.171.19.194]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 14 Jan 2021 10:52:11 +0000 (GMT) Subject: Re: [for-6.0 v5 11/13] spapr: PEF: prevent migration To: "Dr. David Alan Gilbert" Cc: Cornelia Huck , Ram Pai , 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 References: <20201217151530.54431f0e@bahia.lan> <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> From: Christian Borntraeger Message-ID: Date: Thu, 14 Jan 2021 11:52:11 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210114103643.GD2905@work-vm> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343,18.0.737 definitions=2021-01-14_03:2021-01-13,2021-01-14 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 mlxlogscore=999 clxscore=1015 phishscore=0 malwarescore=0 spamscore=0 priorityscore=1501 suspectscore=0 lowpriorityscore=0 bulkscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101140060 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 14.01.21 11:36, 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. Hmmm, fair enough. How do we do this with host-model? The constructed model would contain unpack, but then it will fail to startup? Or do we silently drop unpack in that case? Both variants do not feel completely right.