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=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 65CD9C4361B for ; Fri, 18 Dec 2020 12:10:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2422A23A5B for ; Fri, 18 Dec 2020 12:10:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726839AbgLRMKW (ORCPT ); Fri, 18 Dec 2020 07:10:22 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:35861 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726559AbgLRMKW (ORCPT ); Fri, 18 Dec 2020 07:10:22 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608293335; 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=qyhBcJSscLXt03rN/wlqP36IM0VuLCvIcf32trO8ph0=; b=XU+q6UnS2CszvKzjmHZwDAebsZ3wKYySz0OUJB3phVEuzRAfzX7dxZyzeYPHnEEr+iW/XQ v3F/aoNI9ABRhc+9hohRqMH56fVtJULz44H/LV9L1kwvMyfbCpkIsQhWO3P/qq23sIr/d4 /3E51m5+HNImvsGjI7PEwzKm9agrNms= 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-112-EKwJsLpENtmXHXyBkdaN5w-1; Fri, 18 Dec 2020 07:08:53 -0500 X-MC-Unique: EKwJsLpENtmXHXyBkdaN5w-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9A4A01006C88; Fri, 18 Dec 2020 12:08:51 +0000 (UTC) Received: from work-vm (ovpn-114-200.ams2.redhat.com [10.36.114.200]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D362260C43; Fri, 18 Dec 2020 12:08:38 +0000 (UTC) Date: Fri, 18 Dec 2020 12:08:36 +0000 From: "Dr. David Alan Gilbert" To: Cornelia Huck Cc: Greg Kurz , David Gibson , pair@us.ibm.com, brijesh.singh@amd.com, frankja@linux.ibm.com, kvm@vger.kernel.org, "Michael S. Tsirkin" , Richard Henderson , Marcelo Tosatti , david@redhat.com, qemu-devel@nongnu.org, pasic@linux.ibm.com, borntraeger@de.ibm.com, qemu-s390x@nongnu.org, qemu-ppc@nongnu.org, berrange@redhat.com, Marcel Apfelbaum , thuth@redhat.com, pbonzini@redhat.com, rth@twiddle.net, mdroth@linux.vnet.ibm.com, Eduardo Habkost Subject: Re: [for-6.0 v5 11/13] spapr: PEF: prevent migration Message-ID: <20201218120836.GA2956@work-vm> References: <20201204054415.579042-1-david@gibson.dropbear.id.au> <20201204054415.579042-12-david@gibson.dropbear.id.au> <20201214182240.2abd85eb.cohuck@redhat.com> <20201217054736.GH310465@yekko.fritz.box> <20201217123842.51063918.cohuck@redhat.com> <20201217151530.54431f0e@bahia.lan> <20201218124111.4957eb50.cohuck@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201218124111.4957eb50.cohuck@redhat.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org * Cornelia Huck (cohuck@redhat.com) wrote: > On Thu, 17 Dec 2020 15:15:30 +0100 > Greg Kurz wrote: > > > On Thu, 17 Dec 2020 12:38:42 +0100 > > Cornelia Huck wrote: > > > > > On Thu, 17 Dec 2020 16:47:36 +1100 > > > David Gibson wrote: > > > > > > > On Mon, Dec 14, 2020 at 06:22:40PM +0100, Cornelia Huck wrote: > > > > > On Fri, 4 Dec 2020 16:44:13 +1100 > > > > > David Gibson wrote: > > > > > > > > > > > We haven't yet implemented the fairly involved handshaking that will be > > > > > > needed to migrate PEF protected guests. For now, just use a migration > > > > > > blocker so we get a meaningful error if someone attempts this (this is the > > > > > > same approach used by AMD SEV). > > > > > > > > > > > > Signed-off-by: David Gibson > > > > > > Reviewed-by: Dr. David Alan Gilbert > > > > > > --- > > > > > > hw/ppc/pef.c | 9 +++++++++ > > > > > > 1 file changed, 9 insertions(+) > > > > > > > > > > > > diff --git a/hw/ppc/pef.c b/hw/ppc/pef.c > > > > > > index 3ae3059cfe..edc3e744ba 100644 > > > > > > --- a/hw/ppc/pef.c > > > > > > +++ b/hw/ppc/pef.c > > > > > > @@ -38,7 +38,11 @@ struct PefGuestState { > > > > > > }; > > > > > > > > > > > > #ifdef CONFIG_KVM > > > > > > +static Error *pef_mig_blocker; > > > > > > + > > > > > > static int kvmppc_svm_init(Error **errp) > > > > > > > > > > This looks weird? > > > > > > > > Oops. Not sure how that made it past even my rudimentary compile > > > > testing. > > > > > > > > > > + > > > > > > +int kvmppc_svm_init(SecurableGuestMemory *sgm, Error **errp) > > > > > > { > > > > > > if (!kvm_check_extension(kvm_state, KVM_CAP_PPC_SECURABLE_GUEST)) { > > > > > > error_setg(errp, > > > > > > @@ -54,6 +58,11 @@ static int kvmppc_svm_init(Error **errp) > > > > > > } > > > > > > } > > > > > > > > > > > > + /* add migration blocker */ > > > > > > + error_setg(&pef_mig_blocker, "PEF: Migration is not implemented"); > > > > > > + /* NB: This can fail if --only-migratable is used */ > > > > > > + migrate_add_blocker(pef_mig_blocker, &error_fatal); > > > > > > > > > > Just so that I understand: is PEF something that is enabled by the host > > > > > (and the guest is either secured or doesn't start), or is it using a > > > > > model like s390x PV where the guest initiates the transition into > > > > > secured mode? > > > > > > > > Like s390x PV it's initiated by the guest. > > > > > > > > > Asking because s390x adds the migration blocker only when the > > > > > transition is actually happening (i.e. guests that do not transition > > > > > into secure mode remain migratable.) This has the side effect that you > > > > > might be able to start a machine with --only-migratable that > > > > > transitions into a non-migratable machine via a guest action, if I'm > > > > > not mistaken. Without the new object, I don't see a way to block with > > > > > --only-migratable; with it, we should be able to do that. Not sure what > > > > > the desirable behaviour is here. > > > > > > > > The purpose of --only-migratable is specifically to prevent the machine > > to transition to a non-migrate state IIUC. The guest transition to > > secure mode should be nacked in this case. > > Yes, that's what happens for s390x: The guest tries to transition, QEMU > can't add a migration blocker and fails the instruction used for > transitioning, the guest sees the error. > > The drawback is that we see the failure only when we already launched > the machine and the guest tries to transition. If I start QEMU with > --only-migratable, it will refuse to start when non-migratable devices > are configured in the command line, so I see the issue right from the > start. (For s390x, that would possibly mean that we should not even > present the cpu feature bit when only_migratable is set?) I see --only-migratable as refusing to start if you've enabled anything that would stop migration. So I'd expect: a) Allow the cpu flag to be turned on/off somehow b) If you ask for it (-cpu ...,_confidentialcomp or whatever) and you've got --only-migratable then you'd fail before startup. Dave > > > > > > Hm, I'm not sure what the best option is here either. > > > > > > If we agree on anything, it should be as consistent across > > > architectures as possible :) > > > > > > If we want to add the migration blocker to s390x even before the guest > > > transitions, it needs to be tied to the new object; if we'd make it > > > dependent on the cpu feature bit, we'd block migration of all machines > > > on hardware with SE and a recent kernel. > > > > > > Is there a convenient point in time when PEF guests transition where > > > QEMU can add a blocker? > > > > > > > > > > > > > > > > > > + > > > > > > return 0; > > > > > > } > > > > > > > > > > > > > > > > > > > > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK