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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 2B189C433DF for ; Wed, 10 Jun 2020 13:28:53 +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 F2BC22072E for ; Wed, 10 Jun 2020 13:28:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F2BC22072E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:35776 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jj0mi-0001wC-9F for qemu-devel@archiver.kernel.org; Wed, 10 Jun 2020 09:28:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49446) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jj0b5-0008WH-Me; Wed, 10 Jun 2020 09:16:51 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:22422) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jj0ah-0005Hc-Iq; Wed, 10 Jun 2020 09:16:51 -0400 Received: from pps.filterd (m0187473.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 05AD2Oka083336; Wed, 10 Jun 2020 09:16:18 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 31k027rcg3-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 10 Jun 2020 09:16:18 -0400 Received: from m0187473.ppops.net (m0187473.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 05AD3YIK086706; Wed, 10 Jun 2020 09:16:17 -0400 Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 31k027rcdn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 10 Jun 2020 09:16:16 -0400 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 05ADG8Ar023217; Wed, 10 Jun 2020 13:16:10 GMT Received: from b06avi18626390.portsmouth.uk.ibm.com (b06avi18626390.portsmouth.uk.ibm.com [9.149.26.192]) by ppma03ams.nl.ibm.com with ESMTP id 31g2s7yr6u-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 10 Jun 2020 13:16:09 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 05ADEKfF64684392 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 10 Jun 2020 13:14:20 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 601894C059; Wed, 10 Jun 2020 13:15:36 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B1EA04C046; Wed, 10 Jun 2020 13:15:35 +0000 (GMT) Received: from oc2783563651 (unknown [9.145.127.50]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 10 Jun 2020 13:15:35 +0000 (GMT) Date: Wed, 10 Jun 2020 15:15:29 +0200 From: Halil Pasic To: "Michael S. Tsirkin" Subject: Re: [PATCH v2 1/1] virtio-ccw: auto-manage VIRTIO_F_IOMMU_PLATFORM if PV Message-ID: <20200610151529.1c53b82e.pasic@linux.ibm.com> In-Reply-To: <20200609124155-mutt-send-email-mst@kernel.org> References: <20200514221155.32079-1-pasic@linux.ibm.com> <20200520121507-mutt-send-email-mst@kernel.org> <20200606013217.2cffa3ed.pasic@linux.ibm.com> <20200608181428.3c6f127c.cohuck@redhat.com> <20200608190045.319dd68b.pasic@linux.ibm.com> <20200609084402.35d317ec.cohuck@redhat.com> <20200609114130.0ca9190b.pasic@linux.ibm.com> <20200609174747.4e300818@ibm-vm> <20200609182839.7ac80938.pasic@linux.ibm.com> <20200609124155-mutt-send-email-mst@kernel.org> Organization: IBM X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216, 18.0.687 definitions=2020-06-10_07:2020-06-10, 2020-06-10 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 spamscore=0 mlxscore=0 cotscore=-2147483648 bulkscore=0 malwarescore=0 lowpriorityscore=0 phishscore=0 suspectscore=0 clxscore=1015 priorityscore=1501 mlxlogscore=943 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006100096 Received-SPF: pass client-ip=148.163.156.1; envelope-from=pasic@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/10 09:16:22 X-ACL-Warn: Detected OS = Linux 3.1-3.10 [fuzzy] X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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: Thomas Huth , Boris Fiuczynski , Janosch Frank , Pierre Morel , David Hildenbrand , Claudio Imbrenda , Richard Henderson , Cornelia Huck , qemu-devel@nongnu.org, Christian Borntraeger , qemu-s390x@nongnu.org, Viktor Mihajlovski , David Gibson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 9 Jun 2020 12:44:39 -0400 "Michael S. Tsirkin" wrote: > On Tue, Jun 09, 2020 at 06:28:39PM +0200, Halil Pasic wrote: > > On Tue, 9 Jun 2020 17:47:47 +0200 > > Claudio Imbrenda wrote: > > > > > On Tue, 9 Jun 2020 11:41:30 +0200 > > > Halil Pasic wrote: > > > > > > [...] > > > > > > > I don't know. Janosch could answer that, but he is on vacation. Adding > > > > Claudio maybe he can answer. My understanding is, that while it might > > > > be possible, it is ugly at best. The ability to do a transition is > > > > indicated by a CPU model feature. Indicating the feature to the guest > > > > and then failing the transition sounds wrong to me. > > > > > > I agree. If the feature is advertised, then it has to work. I don't > > > think we even have an architected way to fail the transition for that > > > reason. > > > > > > What __could__ be done is to prevent qemu from even starting if an > > > incompatible device is specified together with PV. > > > > AFAIU, the "specified together with PV" is the problem here. Currently > > we don't "specify PV" but PV is just a capability that is managed by the > > CPU model (like so many other). > > So if we want to keep it user friendly, there could be > protection property with values on/off/auto, and auto > would poke at host capability to figure out whether > it's supported. > > Both virtio and CPU would inherit from that. > > This will allow other useful features such as ability > to hide PV from guest, which could in turn be handy e.g. > to allow migration to hosts without PV support, > or if host wants to force ability to read guest memory > e.g. for security. > > We already have the ability to "hide PV from guest". One just needs to specify that the unpack facility is not ought to be included in the CPU model. E.g. something like -cpu host,unpack=off. Regards, Halil