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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 31915C433F5 for ; Wed, 13 Oct 2021 11:24:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1A65361056 for ; Wed, 13 Oct 2021 11:24:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230399AbhJML01 (ORCPT ); Wed, 13 Oct 2021 07:26:27 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:58560 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229664AbhJML0T (ORCPT ); Wed, 13 Oct 2021 07:26:19 -0400 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 19D9ihA8024150; Wed, 13 Oct 2021 07:24:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=E/CRiS9YKBGOipiZLMur3q/Gu9YWSpriqGljYzhvoLk=; b=qUb4A8LUqXMxe9NOmZwgO/NhGO3cIsui3mJTnSXJfm2o6DAUmSJ2ILHdp7mlgpJDgZmN 3E6ePsp+O7Aa8goCMqqmsIO2XPaZK9xaxiyiOJXDxHO7KEoEKGTcBerBSJUDHDHHRoL6 0wjcCQRXKnu9UKbtdnlMVTZoDty0cqTmd9mDLh9S9LtHM1kYCXkUUkbU1c5Gw3zTMmnp cJb3+ftDtTDYbT4GlymSZkzZJHHad6kMQyxWgonJUM/NI6T5XdJiqc5JdfqkT5wXNaLv /jEvOl3JlacJULN2obiBBSI7NX3HVZZNWnlqxi58cP1BOoFWkY3OCOWtkzFvr6fDwiLZ Gw== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3bnqmp8tj6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 13 Oct 2021 07:24:05 -0400 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 19DAq2ds026142; Wed, 13 Oct 2021 07:24:05 -0400 Received: from ppma04fra.de.ibm.com (6a.4a.5195.ip4.static.sl-reverse.com [149.81.74.106]) by mx0a-001b2d01.pphosted.com with ESMTP id 3bnqmp8thd-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 13 Oct 2021 07:24:04 -0400 Received: from pps.filterd (ppma04fra.de.ibm.com [127.0.0.1]) by ppma04fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 19DBFcNt013781; Wed, 13 Oct 2021 11:24:02 GMT Received: from b06avi18626390.portsmouth.uk.ibm.com (b06avi18626390.portsmouth.uk.ibm.com [9.149.26.192]) by ppma04fra.de.ibm.com with ESMTP id 3bk2qafun1-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 13 Oct 2021 11:24:01 +0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 19DBIKJG46137814 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 13 Oct 2021 11:18:21 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 08D7E52075; Wed, 13 Oct 2021 11:23:56 +0000 (GMT) Received: from li-43c5434c-23b8-11b2-a85c-c4958fb47a68.ibm.com (unknown [9.171.3.131]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id C5C0C5205A; Wed, 13 Oct 2021 11:23:51 +0000 (GMT) Subject: Re: [PATCH v3 1/1] virtio: write back F_VERSION_1 before validate To: "Michael S. Tsirkin" , Halil Pasic Cc: Jason Wang , Xie Yongji , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, markver@us.ibm.com, Cornelia Huck , linux-s390@vger.kernel.org, stefanha@redhat.com, Raphael Norwitz , qemu-devel@nongnu.org References: <20211011053921.1198936-1-pasic@linux.ibm.com> <20211013060923-mutt-send-email-mst@kernel.org> From: Christian Borntraeger Message-ID: <96561e29-e0d6-9a4d-3657-999bad59914e@de.ibm.com> Date: Wed, 13 Oct 2021 13:23:50 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20211013060923-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: HT3wu4tdw-asF-6Di5ricBV3R2j4XXRu X-Proofpoint-ORIG-GUID: gXUvvXMpnSzkMBewd-1wAXM9mg8j7MD9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.0.607.475 definitions=2021-10-13_03,2021-10-13_01,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 priorityscore=1501 bulkscore=0 impostorscore=0 lowpriorityscore=0 phishscore=0 clxscore=1011 mlxscore=0 adultscore=0 spamscore=0 suspectscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109230001 definitions=main-2110130071 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 13.10.21 um 12:10 schrieb Michael S. Tsirkin: > On Mon, Oct 11, 2021 at 07:39:21AM +0200, Halil Pasic wrote: >> The virtio specification virtio-v1.1-cs01 states: "Transitional devices >> MUST detect Legacy drivers by detecting that VIRTIO_F_VERSION_1 has not >> been acknowledged by the driver." This is exactly what QEMU as of 6.1 >> has done relying solely on VIRTIO_F_VERSION_1 for detecting that. >> >> However, the specification also says: "... the driver MAY read (but MUST >> NOT write) the device-specific configuration fields to check that it can >> support the device ..." before setting FEATURES_OK. >> >> In that case, any transitional device relying solely on >> VIRTIO_F_VERSION_1 for detecting legacy drivers will return data in >> legacy format. In particular, this implies that it is in big endian >> format for big endian guests. This naturally confuses the driver which >> expects little endian in the modern mode. >> >> It is probably a good idea to amend the spec to clarify that >> VIRTIO_F_VERSION_1 can only be relied on after the feature negotiation >> is complete. Before validate callback existed, config space was only >> read after FEATURES_OK. However, we already have two regressions, so >> let's address this here as well. >> >> The regressions affect the VIRTIO_NET_F_MTU feature of virtio-net and >> the VIRTIO_BLK_F_BLK_SIZE feature of virtio-blk for BE guests when >> virtio 1.0 is used on both sides. The latter renders virtio-blk unusable >> with DASD backing, because things simply don't work with the default. >> See Fixes tags for relevant commits. >> >> For QEMU, we can work around the issue by writing out the feature bits >> with VIRTIO_F_VERSION_1 bit set. We (ab)use the finalize_features >> config op for this. This isn't enough to address all vhost devices since >> these do not get the features until FEATURES_OK, however it looks like >> the affected devices actually never handled the endianness for legacy >> mode correctly, so at least that's not a regression. >> >> No devices except virtio net and virtio blk seem to be affected. >> >> Long term the right thing to do is to fix the hypervisors. >> >> Cc: #v4.11 >> Signed-off-by: Halil Pasic >> Fixes: 82e89ea077b9 ("virtio-blk: Add validation for block size in config space") >> Fixes: fe36cbe0671e ("virtio_net: clear MTU when out of range") >> Reported-by: markver@us.ibm.com >> Reviewed-by: Cornelia Huck > > OK this looks good! How about a QEMU patch to make it spec compliant on > BE? Who is going to do that? Halil? you? Conny? Can we get this kernel patch queued for 5.15 and stable without waiting for the QEMU patch as we have a regression with 4.14? > >> --- >> >> @Connie: I made some more commit message changes to accommodate Michael's >> requests. I just assumed these will work or you as well and kept your >> r-b. Please shout at me if it needs to be dropped :) >> --- >> drivers/virtio/virtio.c | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c >> index 0a5b54034d4b..236081afe9a2 100644 >> --- a/drivers/virtio/virtio.c >> +++ b/drivers/virtio/virtio.c >> @@ -239,6 +239,17 @@ static int virtio_dev_probe(struct device *_d) >> driver_features_legacy = driver_features; >> } >> >> + /* >> + * Some devices detect legacy solely via F_VERSION_1. Write >> + * F_VERSION_1 to force LE config space accesses before FEATURES_OK for >> + * these when needed. >> + */ >> + if (drv->validate && !virtio_legacy_is_little_endian() >> + && device_features & BIT_ULL(VIRTIO_F_VERSION_1)) { >> + dev->features = BIT_ULL(VIRTIO_F_VERSION_1); >> + dev->config->finalize_features(dev); >> + } >> + >> if (device_features & (1ULL << VIRTIO_F_VERSION_1)) >> dev->features = driver_features & device_features; >> else >> >> base-commit: 60a9483534ed0d99090a2ee1d4bb0b8179195f51 >> -- >> 2.25.1 >