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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id B4617C433F5 for ; Tue, 25 Jan 2022 10:28:54 +0000 (UTC) Received: from localhost ([::1]:53912 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nCJ4H-0008Ck-Hc for qemu-devel@archiver.kernel.org; Tue, 25 Jan 2022 05:28:53 -0500 Received: from eggs.gnu.org ([209.51.188.92]:42390) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nCIxG-000559-8B; Tue, 25 Jan 2022 05:21:39 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:29718) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nCIxB-0004I1-TP; Tue, 25 Jan 2022 05:21:36 -0500 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 20PADb7U024665; Tue, 25 Jan 2022 10:21:20 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : subject : message-id : in-reply-to : references : mime-version : content-type : content-transfer-encoding; s=pp1; bh=ArCra1fQ8T+J7Ab+fTdca6KALLIXb3h0mQaNiQojm5g=; b=it1EWQOFcv8/z3axIyZ9H0BFvSvkPXp6DjtCzrWxT/GD0+R7RJEgrLd72snEvYWv9E+I VZo/zxH7nCJg0N6dtIsBNOECzNw1kHR/y0AcuMV1BIdQr30ivJFZMHxanD0ccFTaX5SC qDPQ1x9rnv/xEqzupZbX6As157M2P4hK9LAj+eIC0wIb34Du6x4sLlKnQ4jCpWYWsbYr kRGqlDEpmZgy1cEIDyDiizXQ1CPatOyI7D8tqVrByk5nj1X0nWZcdLKFwxU4J9nxio8l YVrCXQpeFYUCcoYGrXFlCeUk+K/YrL4BW/k1RIRXjvkrQNKMfVGWzlhln7r6QhiQDmlr 7g== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3dtf92g410-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 25 Jan 2022 10:21:20 +0000 Received: from m0098393.ppops.net (m0098393.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 20PAFSUc029675; Tue, 25 Jan 2022 10:21:20 GMT Received: from ppma01fra.de.ibm.com (46.49.7a9f.ip4.static.sl-reverse.com [159.122.73.70]) by mx0a-001b2d01.pphosted.com with ESMTP id 3dtf92g406-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 25 Jan 2022 10:21:19 +0000 Received: from pps.filterd (ppma01fra.de.ibm.com [127.0.0.1]) by ppma01fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 20PADO6d016833; Tue, 25 Jan 2022 10:21:17 GMT Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by ppma01fra.de.ibm.com with ESMTP id 3dr9j9bfvc-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 25 Jan 2022 10:21:17 +0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 20PALF6M7537064 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 25 Jan 2022 10:21:15 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EBCE352059; Tue, 25 Jan 2022 10:21:14 +0000 (GMT) Received: from li-e979b1cc-23ba-11b2-a85c-dfd230f6cf82 (unknown [9.171.54.57]) by d06av21.portsmouth.uk.ibm.com (Postfix) with SMTP id 88CF652051; Tue, 25 Jan 2022 10:21:14 +0000 (GMT) Date: Tue, 25 Jan 2022 11:21:12 +0100 From: Halil Pasic To: "Michael S. Tsirkin" , qemu-devel@nongnu.org Subject: Re: [PATCH v2 1/1] virtio: fix the condition for iommu_platform not supported Message-ID: <20220125112112.44957075.pasic@linux.ibm.com> In-Reply-To: <20220117120238.2519239-1-pasic@linux.ibm.com> References: <20220117120238.2519239-1-pasic@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.32; 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-GUID: D7JEeiz7WS8pZ1XAeAeJVo8iTi5y8_Lx X-Proofpoint-ORIG-GUID: X_KNKLS7V44Lj6PNlbI26sGPPLhpBsGC X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-01-25_02,2022-01-25_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 mlxlogscore=999 phishscore=0 spamscore=0 mlxscore=0 priorityscore=1501 malwarescore=0 clxscore=1015 adultscore=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2201250063 Received-SPF: pass client-ip=148.163.156.1; envelope-from=pasic@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-Spam_score_int: -19 X-Spam_score: -2.0 X-Spam_bar: -- X-Spam_report: (-2.0 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Halil Pasic , Cornelia Huck , Jakob Naucke , qemu-stable@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" ping On Mon, 17 Jan 2022 13:02:38 +0100 Halil Pasic wrote: > The commit 04ceb61a40 ("virtio: Fail if iommu_platform is requested, but > unsupported") claims to fail the device hotplug when iommu_platform > is requested, but not supported by the (vhost) device. On the first > glance the condition for detecting that situation looks perfect, but > because a certain peculiarity of virtio_platform it ain't. > > In fact the aforementioned commit introduces a regression. It breaks > virtio-fs support for Secure Execution, and most likely also for AMD SEV > or any other confidential guest scenario that relies encrypted guest > memory. The same also applies to any other vhost device that does not > support _F_ACCESS_PLATFORM. > > The peculiarity is that iommu_platform and _F_ACCESS_PLATFORM collates > "device can not access all of the guest RAM" and "iova != gpa, thus > device needs to translate iova". > > Confidential guest technologies currently rely on the device/hypervisor > offering _F_ACCESS_PLATFORM, so that, after the feature has been > negotiated, the guest grants access to the portions of memory the > device needs to see. So in for confidential guests, generally, > _F_ACCESS_PLATFORM is about the restricted access to memory, but not > about the addresses used being something else than guest physical > addresses. > > This is the very reason for which commit f7ef7e6e3b ("vhost: correctly > turn on VIRTIO_F_IOMMU_PLATFORM") for, which fences _F_ACCESS_PLATFORM > form the vhost device that does not need it, because on the vhost > interface it only means "I/O address translation is needed". > > This patch takes inspiration from f7ef7e6e3b ("vhost: correctly turn on > VIRTIO_F_IOMMU_PLATFORM"), and uses the same condition for detecting the > situation when _F_ACCESS_PLATFORM is requested, but no I/O translation > by the device, and thus no device capability is needed. In this > situation claiming that the device does not support iommu_plattform=on > is counter-productive. So let us stop doing that! > > Signed-off-by: Halil Pasic > Reported-by: Jakob Naucke > Fixes: 04ceb61a40 ("virtio: Fail if iommu_platform is requested, but > unsupported") > Cc: Kevin Wolf > Cc: qemu-stable@nongnu.org > > --- > > v1->v2: > * Commit message tweaks. Most notably fixed commit SHA (Michael) > > --- > hw/virtio/virtio-bus.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c > index d23db98c56..c1578f3de2 100644 > --- a/hw/virtio/virtio-bus.c > +++ b/hw/virtio/virtio-bus.c > @@ -69,11 +69,6 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) > return; > } > > - if (has_iommu && !virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) { > - error_setg(errp, "iommu_platform=true is not supported by the device"); > - return; > - } > - > if (klass->device_plugged != NULL) { > klass->device_plugged(qbus->parent, &local_err); > } > @@ -88,6 +83,12 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) > } else { > vdev->dma_as = &address_space_memory; > } > + > + if (has_iommu && vdev->dma_as != &address_space_memory > + && !virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) { > + error_setg(errp, "iommu_platform=true is not supported by the device"); > + return; > + } > } > > /* Reset the virtio_bus */ > > base-commit: 6621441db50d5bae7e34dbd04bf3c57a27a71b32