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,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 6B1B4C433E0 for ; Thu, 14 Jan 2021 10:37:52 +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 C4CF623A50 for ; Thu, 14 Jan 2021 10:37:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C4CF623A50 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]:48786 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l000k-0003mw-Ee for qemu-devel@archiver.kernel.org; Thu, 14 Jan 2021 05:37:50 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:37206) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l0002-0003Bx-41 for qemu-devel@nongnu.org; Thu, 14 Jan 2021 05:37:06 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46861) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kzzzz-0000HX-TZ for qemu-devel@nongnu.org; Thu, 14 Jan 2021 05:37:05 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610620623; 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: in-reply-to:in-reply-to:references:references; bh=4ArMEYMxt1aGuAZDThGV6VJabcOkpJRR+nDUpyDI9Lk=; b=iQeagjFncLjWdDez2oUKygMJB1kWwci2LGzqelUvA9f/zxruusiOXF+/uXgM7Fq/cgMRoo uIt95bjdobMtmM08u5DaVldL0/kZjm1Scu5CuFlIkjno5y0eMy/1b1F5iUEL/6pJ/squUC L55iLMSgQxCe/WgzilPhCqwpm/a7QXc= 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-579-6igFpg3fPI2_xql-Ql6rXw-1; Thu, 14 Jan 2021 05:36:59 -0500 X-MC-Unique: 6igFpg3fPI2_xql-Ql6rXw-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 1E80B19251AE; Thu, 14 Jan 2021 10:36:57 +0000 (UTC) Received: from work-vm (ovpn-115-29.ams2.redhat.com [10.36.115.29]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4136412D7E; Thu, 14 Jan 2021 10:36:45 +0000 (UTC) Date: Thu, 14 Jan 2021 10:36:43 +0000 From: "Dr. David Alan Gilbert" To: Christian Borntraeger Subject: Re: [for-6.0 v5 11/13] spapr: PEF: prevent migration Message-ID: <20210114103643.GD2905@work-vm> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6e02e8d5-af4b-624b-1a12-d03b9d554a41@de.ibm.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Received-SPF: pass client-ip=216.205.24.124; envelope-from=dgilbert@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=-0.25, 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_H3=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: pair@us.ibm.com, Cornelia Huck , brijesh.singh@amd.com, kvm@vger.kernel.org, "Michael S. Tsirkin" , Ram Pai , qemu-devel@nongnu.org, frankja@linux.ibm.com, david@redhat.com, mdroth@linux.vnet.ibm.com, Halil Pasic , David Gibson , thuth@redhat.com, Eduardo Habkost , Richard Henderson , Greg Kurz , qemu-s390x@nongnu.org, rth@twiddle.net, berrange@redhat.com, Marcelo Tosatti , qemu-ppc@nongnu.org, pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * 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. Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK