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=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham 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 0C530C433E0 for ; Tue, 19 Jan 2021 08:35:55 +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 4D7BC2312E for ; Tue, 19 Jan 2021 08:35:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4D7BC2312E 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]:53068 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l1mUT-0007eJ-0Z for qemu-devel@archiver.kernel.org; Tue, 19 Jan 2021 03:35:53 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:33922) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l1mTb-00075I-UL for qemu-devel@nongnu.org; Tue, 19 Jan 2021 03:34:59 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:41182) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l1mTW-0002GT-K1 for qemu-devel@nongnu.org; Tue, 19 Jan 2021 03:34:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611045292; 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=exmrZ/6vymYFyD9ipg+t6sb8kPfC89qM4+qnKpuaTAg=; b=eNML51s4pnfQCUKPG9ZGV5rNs9DESx6vr/thPfTJDGiDifuTKhhWOAJQjU8yNQatn6k0g/ OZTeEfBMyU9wIfL9J258tasSFMMHUF/abMtCaX6Sr/MKuySL6t1PBl2buhFnOTkCaRDus5 E/aQ5Hq9hV1M8t8D/qoEZ4O57Eoh3W8= 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-155-HzeH01mdPoiYhDERGSwrmA-1; Tue, 19 Jan 2021 03:34:51 -0500 X-MC-Unique: HzeH01mdPoiYhDERGSwrmA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 32AEB1842142; Tue, 19 Jan 2021 08:34:48 +0000 (UTC) Received: from gondolin (ovpn-113-246.ams2.redhat.com [10.36.113.246]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7BC6D6A8F9; Tue, 19 Jan 2021 08:34:27 +0000 (UTC) Date: Tue, 19 Jan 2021 09:34:24 +0100 From: Cornelia Huck To: Christian Borntraeger Subject: Re: [for-6.0 v5 11/13] spapr: PEF: prevent migration Message-ID: <20210119093424.165cfebb.cohuck@redhat.com> In-Reply-To: <2f358741-a9a5-a5d6-715c-c3dba85fbb17@de.ibm.com> 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> <20210114112517.GE1643043@redhat.com> <20210114235125.GO435587@yekko.fritz.box> <20210118173912.GF9899@work-vm> <2f358741-a9a5-a5d6-715c-c3dba85fbb17@de.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Received-SPF: pass client-ip=216.205.24.124; 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_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, Boris Fiuczynski , brijesh.singh@amd.com, kvm@vger.kernel.org, David Hildenbrand , Ram Pai , qemu-devel@nongnu.org, frankja@linux.ibm.com, "Michael S. Tsirkin" , Halil Pasic , Viktor Mihajlovski , thuth@redhat.com, Eduardo Habkost , Richard Henderson , "Dr. David Alan Gilbert" , Greg Kurz , qemu-s390x@nongnu.org, rth@twiddle.net, "Daniel P. =?UTF-8?B?QmVycmFuZ8Op?=" , Marcelo Tosatti , qemu-ppc@nongnu.org, David Gibson , pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 19 Jan 2021 09:28:22 +0100 Christian Borntraeger wrote: > On 18.01.21 18:39, Dr. David Alan Gilbert wrote: > > * David Gibson (david@gibson.dropbear.id.au) wrote: =20 > >> On Thu, Jan 14, 2021 at 11:25:17AM +0000, Daniel P. Berrang=C3=A9 wrot= e: =20 > >>> On Wed, Jan 13, 2021 at 12:42:26PM +0000, Dr. David Alan Gilbert wrot= e: =20 > >>>> * Cornelia Huck (cohuck@redhat.com) wrote: =20 > >>>>> On Tue, 5 Jan 2021 12:41:25 -0800 > >>>>> Ram Pai wrote: > >>>>> =20 > >>>>>> On Tue, Jan 05, 2021 at 11:56:14AM +0100, Halil Pasic wrote: =20 > >>>>>>> On Mon, 4 Jan 2021 10:40:26 -0800 > >>>>>>> Ram Pai wrote: =20 > >>>>> =20 > >>>>>>>> The main difference between my proposal and the other proposal i= s... > >>>>>>>> > >>>>>>>> In my proposal the guest makes the compatibility decision and = acts > >>>>>>>> accordingly. In the other proposal QEMU makes the compatibili= ty > >>>>>>>> decision and acts accordingly. I argue that QEMU cannot make a= good > >>>>>>>> compatibility decision, because it wont know in advance, if th= e guest > >>>>>>>> will or will-not switch-to-secure. > >>>>>>>> =20 > >>>>>>> > >>>>>>> You have a point there when you say that QEMU does not know in ad= vance, > >>>>>>> if the guest will or will-not switch-to-secure. I made that argum= ent > >>>>>>> regarding VIRTIO_F_ACCESS_PLATFORM (iommu_platform) myself. My id= ea > >>>>>>> was to flip that property on demand when the conversion occurs. D= avid > >>>>>>> explained to me that this is not possible for ppc, and that havin= g the > >>>>>>> "securable-guest-memory" property (or whatever the name will be) > >>>>>>> specified is a strong indication, that the VM is intended to be u= sed 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. =20 > >>>>>> > >>>>>> As suggested by Cornelia Huck, what if QEMU disabled the > >>>>>> "securable-guest-memory" property if 'must-support-migrate' is ena= bled? > >>>>>> 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 transi= tion. > >>>>>> Guest that try to transition will fail and terminate themselves. = =20 > >>>>> > >>>>> 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, ev= en > >>>>> if the secure object is not specified. > >>>>> - As migration is currently not supported for secured guests, we ad= d 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 anythin= g.) > >>>>> - 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 wan= t to > >>>>> transition to secure mode, nothing changes; a guest that wants to > >>>>> transition to secure mode will notice that the feature is not avail= able > >>>>> and fail appropriately (or ultimately, when the ultravisor call fai= ls). > >>>>> We'd still fail starting QEMU for the secure object + --only-migrat= able > >>>>> combination. > >>>>> > >>>>> Does that make sense? =20 > >>>> > >>>> 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 st= ops > >>>> you doing something that would have made it unmigratable or causes > >>>> an operation that would make it unmigratable to fail. =20 > >>> > >>> I agree, --only-migratable is supposed to be a *behavioural* toggle > >>> for QEMU. It must /not/ have any impact on the guest ABI. > >>> > >>> A management application needs to be able to add/remove --only-migrat= able > >>> at will without changing the exposing guest ABI. =20 > >> > >> At the qemu level, it sounds like the right thing to do is to fail > >> outright if all of the below are true: > >> 1. --only-migratable is specified > >> 2. -cpu host is specified > >> 3. unpack isn't explicitly disabled > >> 4. the host CPU actually does have the unpack facility > >> > >> That can be changed if & when migration support is added for PV. =20 > >=20 > > That sounds right to me. =20 >=20 > as startup will fail anyway if the guest cpu model enables unpack, but th= e host > cpu does not support it this can be simplified to forbid startup in qemu = if > --only-migratable is combined with unpack being active in the guest cpu m= odel. >=20 > This is actually independent from this patch set. Yep, I think we should just go ahead and fix this. > maybe just > something like >=20 > diff --git a/target/s390x/cpu_models.c b/target/s390x/cpu_models.c > index 35179f9dc7ba..3b85ff4e31b2 100644 > --- a/target/s390x/cpu_models.c > +++ b/target/s390x/cpu_models.c > @@ -26,6 +26,7 @@ > #include "qapi/qmp/qdict.h" > #ifndef CONFIG_USER_ONLY > #include "sysemu/arch_init.h" > +#include "sysemu/sysemu.h" > #include "hw/pci/pci.h" > #endif > #include "qapi/qapi-commands-machine-target.h" > @@ -878,6 +879,11 @@ static void check_compatibility(const S390CPUModel *= max_model, > return; > } > =20 > + if (only_migratable && test_bit(S390_FEAT_UNPACK, model->features)) { > + error_setg(errp, "The unpack facility is not compatible with " > + "the --only-migratable option"); > + } > + > /* detect the missing features to properly report them */ > bitmap_andnot(missing, model->features, max_model->features, S390_FE= AT_MAX); > if (bitmap_empty(missing, S390_FEAT_MAX)) { >=20 >=20 Want to send this as a proper patch?