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_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 296AFC2BA16 for ; Tue, 7 Apr 2020 07:53:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F2E4B2072A for ; Tue, 7 Apr 2020 07:53:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727841AbgDGHxJ (ORCPT ); Tue, 7 Apr 2020 03:53:09 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:5452 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726707AbgDGHxI (ORCPT ); Tue, 7 Apr 2020 03:53:08 -0400 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0377YQ8x007891 for ; Tue, 7 Apr 2020 03:53:07 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 3082pe5p0d-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 07 Apr 2020 03:53:07 -0400 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 7 Apr 2020 08:52:49 +0100 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0377r0TR45613076 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 7 Apr 2020 07:53:00 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F413011C05B; Tue, 7 Apr 2020 07:52:59 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4532511C052; Tue, 7 Apr 2020 07:52:59 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.145.171.200]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 7 Apr 2020 07:52:59 +0000 (GMT) Subject: Re: [PATCH v2 1/5] KVM: s390: vsie: Fix region 1 ASCE sanity shadow address checks To: David Hildenbrand , kvm@vger.kernel.org Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Vasily Gorbik , Heiko Carstens , Cornelia Huck , Janosch Frank , stable@vger.kernel.org References: <20200403153050.20569-1-david@redhat.com> <20200403153050.20569-2-david@redhat.com> From: Christian Borntraeger Autocrypt: addr=borntraeger@de.ibm.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20040707-0012-0000-0000-0000039FD6DB X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20040707-0013-0000-0000-000021DCF729 Message-Id: <3431ccbb-25b2-66fc-5e07-3f449c03b087@de.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676 definitions=2020-04-07_01:2020-04-07,2020-04-06 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 mlxscore=0 clxscore=1015 spamscore=0 lowpriorityscore=0 malwarescore=0 phishscore=0 adultscore=0 mlxlogscore=881 suspectscore=0 bulkscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004070059 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07.04.20 09:49, David Hildenbrand wrote: > On 07.04.20 09:33, Christian Borntraeger wrote: >> >> On 03.04.20 17:30, David Hildenbrand wrote: >>> In case we have a region 1 ASCE, our shadow/g3 address can have any value. >>> Unfortunately, (-1UL << 64) is undefined and triggers sometimes, >>> rejecting valid shadow addresses when trying to walk our shadow table >>> hierarchy. >>> >>> The result is that the prefix cannot get mapped and will loop basically >>> forever trying to map it (-EAGAIN loop). >>> >>> After all, the broken check is only a sanity check, our table shadowing >>> code in kvm_s390_shadow_tables() already checks these conditions, injecting >>> proper translation exceptions. Turn it into a WARN_ON_ONCE(). >> >> After some testing I now triggered this warning: >> >> [ 541.633114] ------------[ cut here ]------------ >> [ 541.633128] WARNING: CPU: 38 PID: 2812 at arch/s390/mm/gmap.c:799 gmap_shadow_pgt_lookup+0x98/0x1a0 >> [ 541.633129] Modules linked in: vhost_net vhost macvtap macvlan tap kvm xt_CHECKSUM xt_MASQUERADE nf_nat_tftp nf_conntrack_tftp xt_CT tun bridge stp llc xt_tcpudp ip6t_REJECT nf_reject_ipv6 ip6t_rpfilter ipt_REJECT nf_reject_ipv4 xt_conntrack ip6table_nat ip6table_mangle ip6table_raw ip6table_security iptable_nat nf_nat iptable_mangle iptable_raw iptable_security nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nfnetlink ip6table_filter ip6_tables iptable_filter rpcrdma sunrpc rdma_ucm rdma_cm iw_cm ib_cm configfs mlx5_ib s390_trng ghash_s390 prng aes_s390 ib_uverbs des_s390 ib_core libdes sha3_512_s390 genwqe_card sha3_256_s390 vfio_ccw crc_itu_t vfio_mdev sha512_s390 mdev vfio_iommu_type1 sha1_s390 vfio eadm_sch zcrypt_cex4 sch_fq_codel ip_tables x_tables mlx5_core sha256_s390 sha_common pkey zcrypt rng_core autofs4 >> [ 541.633164] CPU: 38 PID: 2812 Comm: CPU 0/KVM Not tainted 5.6.0+ #354 >> [ 541.633166] Hardware name: IBM 3906 M04 704 (LPAR) >> [ 541.633167] Krnl PSW : 0704d00180000000 00000014e05dc454 (gmap_shadow_pgt_lookup+0x9c/0x1a0) >> [ 541.633169] R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 RI:0 EA:3 >> [ 541.633171] Krnl GPRS: 0000000000000000 0000001f00000000 0000001f487b8000 ffffffff80000000 >> [ 541.633172] ffffffffffffffff 000003e003defa18 000003e003defa1c 000003e003defa18 >> [ 541.633173] fffffffffffff000 000003e003defa18 000003e003defa28 0000001f70e06300 >> [ 541.633174] 0000001f43484000 00000000043ed200 000003e003def978 000003e003def920 >> [ 541.633203] Krnl Code: 00000014e05dc448: b9800038 ngr %r3,%r8 >> 00000014e05dc44c: a7840014 brc 8,00000014e05dc474 >> #00000014e05dc450: af000000 mc 0,0 >> >00000014e05dc454: a728fff5 lhi %r2,-11 >> 00000014e05dc458: a7180000 lhi %r1,0 >> 00000014e05dc45c: b2fa0070 niai 7,0 >> 00000014e05dc460: 4010b04a sth %r1,74(%r11) >> 00000014e05dc464: b9140022 lgfr %r2,%r2 >> [ 541.633215] Call Trace: >> [ 541.633218] [<00000014e05dc454>] gmap_shadow_pgt_lookup+0x9c/0x1a0 >> [ 541.633257] [<000003ff804c57d6>] kvm_s390_shadow_fault+0x66/0x1e8 [kvm] >> [ 541.633265] [<000003ff804c72dc>] vsie_run+0x43c/0x710 [kvm] >> [ 541.633273] [<000003ff804c85ca>] kvm_s390_handle_vsie+0x632/0x750 [kvm] >> [ 541.633281] [<000003ff804c123c>] kvm_s390_handle_b2+0x84/0x4e0 [kvm] >> [ 541.633289] [<000003ff804b46b2>] kvm_handle_sie_intercept+0x172/0xcb8 [kvm] >> [ 541.633297] [<000003ff804b18a8>] __vcpu_run+0x658/0xc90 [kvm] >> [ 541.633305] [<000003ff804b2920>] kvm_arch_vcpu_ioctl_run+0x248/0x858 [kvm] >> [ 541.633313] [<000003ff8049d454>] kvm_vcpu_ioctl+0x284/0x7b0 [kvm] >> [ 541.633316] [<00000014e087d5ae>] ksys_ioctl+0xae/0xe8 >> [ 541.633318] [<00000014e087d652>] __s390x_sys_ioctl+0x2a/0x38 >> [ 541.633323] [<00000014e0ff02a2>] system_call+0x2a6/0x2c8 >> [ 541.633323] Last Breaking-Event-Address: >> [ 541.633334] [<000003ff804983e0>] kvm_running_vcpu+0x3ea9ee997d8/0x3ea9ee99950 [kvm] >> [ 541.633335] ---[ end trace f69b6021855ea189 ]--- >> >> >> Unfortunately no dump at that point in time. >> I have other tests which are clearly fixed by this patch, so we should propbably go forward anyway. >> Question is, is this just another bug we need to fix or is the assumption that somebody else checked >> all conditions so we can warn false? > > Yeah, I think it is via > > kvm_s390_shadow_fault()->gmap_shadow_pgt_lookup()->gmap_table_walk() > > where we just peek if there is already something shadowed. If not, we go > via the full kvm_s390_shadow_tables() path. > > So we could either do sanity checks in gmap_shadow_pgt_lookup(), or > rather drop the WARN_ON_ONCE. I think the latter makes sense, now that > we understood the problem. Ok, so I will drop the WARN_ON_ONCE and fixup the commit message.