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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 71EFAC433E0 for ; Fri, 26 Jun 2020 09:33:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4AE68212CC for ; Fri, 26 Jun 2020 09:33:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="HaqNEuhI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726710AbgFZJdq (ORCPT ); Fri, 26 Jun 2020 05:33:46 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:21183 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725280AbgFZJdq (ORCPT ); Fri, 26 Jun 2020 05:33:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1593164024; h=from:from:reply-to: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=JwInyFqPNq+XPB0DyOjAdFbK431fsG1hPSaA2tOyD8Y=; b=HaqNEuhIoO5K7mvWqyWxf+gBPF4h8vcJ4SKEA6azjsO8xroP4xacYLR+TLAMZDUo56OgIa KrKHSBCw1fekvY4XUMl4fPa6oFek3dunG7k6vt72CHKXxpgJtxSGpGXLa+56RN/r6DnsYo mZljUHDt8UDFaxim63HtiSyT9NsBntY= 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-463-WIhMDPZHNTSGNwJ0sarg7g-1; Fri, 26 Jun 2020 05:33:15 -0400 X-MC-Unique: WIhMDPZHNTSGNwJ0sarg7g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AD159193F561; Fri, 26 Jun 2020 09:33:13 +0000 (UTC) Received: from redhat.com (unknown [10.36.110.51]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 61D6B1011396; Fri, 26 Jun 2020 09:33:00 +0000 (UTC) Date: Fri, 26 Jun 2020 10:32:57 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Janosch Frank Cc: David Hildenbrand , David Gibson , pair@us.ibm.com, brijesh.singh@amd.com, Eduardo Habkost , kvm@vger.kernel.org, mst@redhat.com, Cornelia Huck , qemu-devel@nongnu.org, dgilbert@redhat.com, pasic@linux.ibm.com, Christian Borntraeger , qemu-s390x@nongnu.org, qemu-ppc@nongnu.org, pbonzini@redhat.com, mdroth@linux.vnet.ibm.com, Richard Henderson Subject: Re: [PATCH v3 0/9] Generalize memory encryption models Message-ID: <20200626093257.GC1028934@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20200619114526.6a6f70c6.cohuck@redhat.com> <79890826-f67c-2228-e98d-25d2168be3da@redhat.com> <20200619120530.256c36cb.cohuck@redhat.com> <358d48e5-4c57-808b-50da-275f5e2a352c@redhat.com> <20200622140254.0dbe5d8c.cohuck@redhat.com> <20200625052518.GD172395@umbus.fritz.box> <025fb54b-60b7-a58b-e3d7-1bbaad152c5c@redhat.com> <20200626044259.GK172395@umbus.fritz.box> <892533f8-cd3c-e282-58c2-4212eb3a84b8@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.14.0 (2020-05-02) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Jun 26, 2020 at 11:01:58AM +0200, Janosch Frank wrote: > On 6/26/20 8:53 AM, David Hildenbrand wrote: > >>>>> Does this have any implications when probing with the 'none' machine? > >>>> > >>>> I'm not sure. In your case, I guess the cpu bit would still show up > >>>> as before, so it would tell you base feature availability, but not > >>>> whether you can use the new configuration option. > >>>> > >>>> Since the HTL option is generic, you could still set it on the "none" > >>>> machine, though it wouldn't really have any effect. That is, if you > >>>> could create a suitable object to point it at, which would depend on > >>>> ... details. > >>>> > >>> > >>> The important point is that we never want the (expanded) host cpu model > >>> look different when either specifying or not specifying the HTL > >>> property. > >> > >> Ah, yes, I see your point. So my current suggestion will satisfy > >> that, basically it is: > >> > >> cpu has unpack (inc. by default) && htl specified > >> => works (allowing secure), as expected > > > > ack > > > >> > >> !cpu has unpack && htl specified > >> => bails out with an error > > > > ack > > > >> > >> !cpu has unpack && !htl specified > >> => works for a non-secure guest, as expected > >> => guest will fail if it attempts to go secure > > > > ack, behavior just like running on older hw without unpack > > > >> > >> cpu has unpack && !htl specified > >> => works as expected for a non-secure guest (unpack feature is > >> present, but unused) > >> => secure guest may work "by accident", but only if all virtio > >> properties have the right values, which is the user's > >> problem > >> > >> That last case is kinda ugly, but I think it's tolerable. > > > > Right, we must not affect non-secure guests, and existing secure setups > > (e.g., older qemu machines). Will have to think about this some more, > > but does not sound too crazy. > > I severely dislike having to specify things to make PV work. > The IOMMU is already a thorn in our side and we're working on making the > whole ordeal completely transparent so the only requirement to make this > work is the right machine, kernel, qemu and kernel cmd line option > "prot_virt=1". That's why we do the reboot into PV mode in the first place. > > I.e. the goal is that if customers convert compatible guests into > protected ones and start them up on a z15 on a distro with PV support > they can just use the guest without having to change XML or command line > parameters. If you're exposing new features to the guest machine, then it is usually to be expected that XML and QEMU command line will change. Some simple things might be hidable behind a new QEMU machine type or CPU model, but there's a limit to how much should be hidden that way while staying sane. I'd really expect the configuration to change when switching a guest to a new hardware platform and wanting major new functionality to be enabled. The XML / QEMU config is a low level instantiation of a particular feature set, optimized for a specific machine, rather than a high level description of ideal "best" config independent of host machine. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|