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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 EA79FC433DB for ; Tue, 19 Jan 2021 08:22:19 +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 444BA2311C for ; Tue, 19 Jan 2021 08:22:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 444BA2311C 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]:43994 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l1mHK-00034l-1A for qemu-devel@archiver.kernel.org; Tue, 19 Jan 2021 03:22:18 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:59424) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l1mFq-0002W0-M8 for qemu-devel@nongnu.org; Tue, 19 Jan 2021 03:20:46 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:39737) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l1mFh-0003k4-7Z for qemu-devel@nongnu.org; Tue, 19 Jan 2021 03:20:46 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611044432; 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=FVk+dgxlEVOpaEFM6NUNwLFA1530NxzYd7Gc5WzY9pU=; b=WIanBZ5VLN0zNKBKtiA8oGTpXvjkxjCVDbYdruCBVZHEw8G9UKo2ZKAbd/FVy87e3aPhAy GUkTvAt4EFC97Nbe078g5LwFERyFH+XNxaUr5pH+7B3X0NrNP4lg7ZZYXsFmbvjGu+RM5i s6h4clJ32gnEPIVV7/T7kKRwTljtJ4g= 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-384-fX8BVZnnMW27Ck-fLdrujQ-1; Tue, 19 Jan 2021 03:20:27 -0500 X-MC-Unique: fX8BVZnnMW27Ck-fLdrujQ-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 0C52C8BAF85; Tue, 19 Jan 2021 08:19:58 +0000 (UTC) Received: from gondolin (ovpn-113-246.ams2.redhat.com [10.36.113.246]) by smtp.corp.redhat.com (Postfix) with ESMTP id B8B676062F; Tue, 19 Jan 2021 08:19:53 +0000 (UTC) Date: Tue, 19 Jan 2021 09:19:50 +0100 From: Cornelia Huck To: Ram Pai Subject: Re: Re: [for-6.0 v5 11/13] spapr: PEF: prevent migration Message-ID: <20210119091950.4a27a615.cohuck@redhat.com> In-Reply-To: <20210115185514.GB24076@ram-ibm-com.ibm.com> References: <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> <20210111195830.GA23898@ram-ibm-com.ibm.com> <20210112091943.095c3b29.cohuck@redhat.com> <20210112185511.GB23898@ram-ibm-com.ibm.com> <20210113090629.2f41a9d3.cohuck@redhat.com> <20210115185514.GB24076@ram-ibm-com.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Received-SPF: pass client-ip=63.128.21.124; envelope-from=cohuck@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=-0.175, 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_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: 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, Halil Pasic , borntraeger@de.ibm.com, David Gibson , thuth@redhat.com, Eduardo Habkost , Richard Henderson , Greg Kurz , dgilbert@redhat.com, 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" On Fri, 15 Jan 2021 10:55:14 -0800 Ram Pai wrote: > On Wed, Jan 13, 2021 at 09:06:29AM +0100, Cornelia Huck wrote: > > On Tue, 12 Jan 2021 10:55:11 -0800 > > Ram Pai wrote: > > > > > On Tue, Jan 12, 2021 at 09:19:43AM +0100, Cornelia Huck wrote: > > > > On Mon, 11 Jan 2021 11:58:30 -0800 > > > > Ram Pai wrote: > > > > > > > > > On Mon, Jan 11, 2021 at 05:59:14PM +0100, Cornelia Huck 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). > > > > > > > > > > > > > > > On POWER, secure-execution is not **automatically** enabled even when > > > > > the host supports it. The feature is enabled only if the secure-object > > > > > is configured, and the host supports it. > > > > > > > > Yes, the cpu feature on s390x is simply pre-existing. > > > > > > > > > > > > > > However the behavior proposed above will be consistent on POWER and > > > > > on s390x, when '--only-migratable' is specified and 'secure-object' > > > > > is NOT specified. > > > > > > > > > > So I am in agreement till now. > > > > > > > > > > > > > > > > We'd still fail starting QEMU for the secure object + --only-migratable > > > > > > combination. > > > > > > > > > > Why fail? > > > > > > > > > > Instead, print a warning and disable the secure-object; which will > > > > > disable your cpu-feature. Guests that do not transition to secure, will > > > > > continue to operate, and guests that transition to secure, will fail. > > > > > > > > But that would be consistent with how other non-migratable objects are > > > > handled, no? It's simply a case of incompatible options on the command > > > > line. > > > > > > Actually the two options are inherently NOT incompatible. Halil also > > > mentioned this in one of his replies. > > > > > > Its just that the current implementation is lacking, which will be fixed > > > in the near future. > > > > > > We can design it upfront, with the assumption that they both are compatible. > > > In the short term disable one; preferrably the secure-object, if both > > > options are specified. In the long term, remove the restriction, when > > > the implemetation is complete. > > > > Can't we simply mark the object as non-migratable now, and then remove > > that later? I don't see what is so special about it. > > This is fine too. > > However I am told that libvirt has some assumptions, where it assumes > that the VM is guaranteed to be migratable if '--only-migratable' is > specified. Silently turning off that option can be bad. > I meant "later" as in "when support for live migration has been added". Mucking around with the options does not sound like a good idea.