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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7D204C636CC for ; Mon, 13 Feb 2023 09:21:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230258AbjBMJV6 (ORCPT ); Mon, 13 Feb 2023 04:21:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229524AbjBMJV5 (ORCPT ); Mon, 13 Feb 2023 04:21:57 -0500 Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 61A24C644; Mon, 13 Feb 2023 01:21:56 -0800 (PST) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 31D8RQK7005640; Mon, 13 Feb 2023 09:21:55 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : date : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding : mime-version; s=pp1; bh=ylaedKUPVkiuwTWek6hj+l+VrUiHb8wDUwllrzXwIQw=; b=Cq519t7rgO3IeRsbaI1A3/J+UphfHr8yiYKjP0cjczS3WhUnro0E8D2yOWIvvyf7zGaB yIf91JWnkh8WNdex3qqAHgNz1SKTVQmtXXL3HxTpbhYqzejUTQQl5WVTisDx3r08jpS1 nZctbDpagLwrzVXhrhNbliGcJ0Vef/5Rq1M1e0w9AVaoojf6hCTTxz9G+PLQjaZpT/P9 oH5IiENCp7YKsADc5vTm6RRZ64xan88ZaMmeed6VO+IE1IBOP49erRGrLrGHa3FG5r0N 9/9OtXAgX0X5dwxpMSOhpNpGafsJHfuATMQnd51a2k3GSK7jAGz5kT/+Anm8gjWHYXBP zQ== Received: from ppma05fra.de.ibm.com (6c.4a.5195.ip4.static.sl-reverse.com [149.81.74.108]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3nqhqa97j3-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 13 Feb 2023 09:21:55 +0000 Received: from pps.filterd (ppma05fra.de.ibm.com [127.0.0.1]) by ppma05fra.de.ibm.com (8.17.1.19/8.17.1.19) with ESMTP id 31D8fYK6008513; Mon, 13 Feb 2023 09:21:53 GMT Received: from smtprelay01.fra02v.mail.ibm.com ([9.218.2.227]) by ppma05fra.de.ibm.com (PPS) with ESMTPS id 3np2n69tas-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 13 Feb 2023 09:21:53 +0000 Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay01.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 31D9Ln5W48628012 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 13 Feb 2023 09:21:50 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D8F3420043; Mon, 13 Feb 2023 09:21:49 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 858ED20040; Mon, 13 Feb 2023 09:21:49 +0000 (GMT) Received: from [9.171.76.240] (unknown [9.171.76.240]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 13 Feb 2023 09:21:49 +0000 (GMT) Message-ID: <38deba59-ac91-0196-d7f0-e7846a7531b3@linux.ibm.com> Date: Mon, 13 Feb 2023 10:21:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [PATCH v3 1/1] KVM: s390: pv: fix external interruption loop not always detected Content-Language: en-US To: Nico Boehr , borntraeger@linux.ibm.com, imbrenda@linux.ibm.com Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org References: <20230213085520.100756-1-nrb@linux.ibm.com> <20230213085520.100756-2-nrb@linux.ibm.com> From: Janosch Frank In-Reply-To: <20230213085520.100756-2-nrb@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed X-TM-AS-GCONF: 00 X-Proofpoint-GUID: CIDdRPkDhr7ntLr0XG-aocxo_lSlfdXp X-Proofpoint-ORIG-GUID: CIDdRPkDhr7ntLr0XG-aocxo_lSlfdXp Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.930,Hydra:6.0.562,FMLib:17.11.170.22 definitions=2023-02-13_04,2023-02-09_03,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 clxscore=1015 mlxscore=0 lowpriorityscore=0 phishscore=0 spamscore=0 priorityscore=1501 mlxlogscore=729 adultscore=0 malwarescore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2302130081 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 2/13/23 09:55, Nico Boehr wrote: > To determine whether the guest has caused an external interruption loop > upon code 20 (external interrupt) intercepts, the ext_new_psw needs to > be inspected to see whether external interrupts are enabled. > > Under non-PV, ext_new_psw can simply be taken from guest lowcore. Under > PV, KVM can only access the encrypted guest lowcore and hence the > ext_new_psw must not be taken from guest lowcore. > > handle_external_interrupt() incorrectly did that and hence was not able > to reliably tell whether an external interruption loop is happening or > not. False negatives cause spurious failures of my kvm-unit-test > for extint loops[1] under PV. > > Since code 20 is only caused under PV if and only if the guest's > ext_new_psw is enabled for external interrupts, false positive detection > of a external interruption loop can not happen. > > Fix this issue by instead looking at the guest PSW in the state > description. Since the PSW swap for external interrupt is done by the > ultravisor before the intercept is caused, this reliably tells whether > the guest is enabled for external interrupts in the ext_new_psw. > > Also update the comments to explain better what is happening. > > [1] https://lore.kernel.org/kvm/20220812062151.1980937-4-nrb@linux.ibm.com/ > > Signed-off-by: Nico Boehr > --- Reviewed-by: Janosch Frank