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Fri, 4 Sep 2020 11:33:29 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5703342047; Fri, 4 Sep 2020 11:33:29 +0000 (GMT) Received: from localhost.localdomain (unknown [9.145.183.173]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 4 Sep 2020 11:33:29 +0000 (GMT) Subject: Re: [PATCH 2/2] s390x: Add 3f program exception handler To: Heiko Carstens Cc: linux-s390@vger.kernel.org, borntraeger@de.ibm.com, gor@linux.ibm.com, imbrenda@linux.ibm.com, kvm@vger.kernel.org, david@redhat.com References: <20200903131435.2535-1-frankja@linux.ibm.com> <20200903131435.2535-3-frankja@linux.ibm.com> <20200904103543.GD6075@osiris> From: Janosch Frank Autocrypt: addr=frankja@linux.ibm.com; prefer-encrypt=mutual; keydata= mQINBFubpD4BEADX0uhkRhkj2AVn7kI4IuPY3A8xKat0ihuPDXbynUC77mNox7yvK3X5QBO6 qLqYr+qrG3buymJJRD9xkp4mqgasHdB5WR9MhXWKH08EvtvAMkEJLnqxgbqf8td3pCQ2cEpv 15mH49iKSmlTcJ+PvJpGZcq/jE42u9/0YFHhozm8GfQdb9SOI/wBSsOqcXcLTUeAvbdqSBZe zuMRBivJQQI1esD9HuADmxdE7c4AeMlap9MvxvUtWk4ZJ/1Z3swMVCGzZb2Xg/9jZpLsyQzb lDbbTlEeyBACeED7DYLZI3d0SFKeJZ1SUyMmSOcr9zeSh4S4h4w8xgDDGmeDVygBQZa1HaoL Esb8Y4avOYIgYDhgkCh0nol7XQ5i/yKLtnNThubAcxNyryw1xSstnKlxPRoxtqTsxMAiSekk 0m3WJwvwd1s878HrQNK0orWd8BzzlSswzjNfQYLF466JOjHPWFOok9pzRs+ucrs6MUwDJj0S cITWU9Rxb04XyigY4XmZ8dywaxwi2ZVTEg+MD+sPmRrTw+5F+sU83cUstuymF3w1GmyofgsU Z+/ldjToHnq21MNa1wx0lCEipCCyE/8K9B9bg9pUwy5lfx7yORP3JuAUfCYb8DVSHWBPHKNj HTOLb2g2UT65AjZEQE95U2AY9iYm5usMqaWD39pAHfhC09/7NQARAQABtCVKYW5vc2NoIEZy YW5rIDxmcmFua2phQGxpbnV4LmlibS5jb20+iQI3BBMBCAAhBQJbm6Q+AhsjBQsJCAcCBhUI CQoLAgQWAgMBAh4BAheAAAoJEONU5rjiOLn4p9gQALjkdj5euJVI2nNT3/IAxAhQSmRhPEt0 AmnCYnuTcHRWPujNr5kqgtyER9+EMQ0ZkX44JU2q7OWxTdSNSAN/5Z7qmOR9JySvDOf4d3mS bMB5zxL9d8SbnSs1uW96H9ZBTlTQnmLfsiM9TetAjSrR8nUmjGhe2YUhJLR1v1LguME+YseT eXnLzIzqqpu311/eYiiIGcmaOjPCE+vFjcXL5oLnGUE73qSYiujwhfPCCUK0850o1fUAYq5p CNBCoKT4OddZR+0itKc/cT6NwEDwdokeg0+rAhxb4Rv5oFO70lziBplEjOxu3dqgIKbHbjza EXTb+mr7VI9O4tTdqrwJo2q9zLqqOfDBi7NDvZFLzaCewhbdEpDYVu6/WxprAY94hY3F4trT rQMHJKQENtF6ZTQc9fcT5I3gAmP+OEvDE5hcTALpWm6Z6SzxO7gEYCnF+qGXqp8sJVrweMub UscyLqHoqdZC2UG4LQ1OJ97nzDpIRe0g6oJ9ZIYHKmfw5jjwH6rASTld5MFWajWdNsqK15k/ RZnHAGICKVIBOBsq26m4EsBlfCdt3b/6emuBjUXR1pyjHMz2awWzCq6/6OWs5eANZ0sdosNq dq2v0ULYTazJz2rlCXV89qRa7ukkNwdBSZNEwsD4eEMicj1LSrqWDZMAALw50L4jxaMD7lPL jJbauQINBFubpD4BEADAcUTRqXF/aY53OSH7IwIK9lFKxIm0IoFkOEh7LMfp7FGzaP7ANrZd cIzhZi38xyOkcaFY+npGEWvko7rlIAn0JpBO4x3hfhmhBD/WSY8LQIFQNNjEm3vzrMo7b9Jb JAqQxfbURY3Dql3GUzeWTG9uaJ00u+EEPlY8zcVShDltIl5PLih20e8xgTnNzx5c110lQSu0 iZv2lAE6DM+2bJQTsMSYiwKlwTuv9LI9Chnoo6+tsN55NqyMxYqJgElk3VzlTXSr3+rtSCwf tq2cinETbzxc1XuhIX6pu/aCGnNfuEkM34b7G1D6CPzDMqokNFbyoO6DQ1+fW6c5gctXg/lZ 602iEl4C4rgcr3+EpfoPUWzKeM8JXv5Kpq4YDxhvbitr8Dm8gr38+UKFZKlWLlwhQ56r/zAU v6LIsm11GmFs2/cmgD1bqBTNHHcTWwWtRTLgmnqJbVisMJuYJt4KNPqphTWsPY8SEtbufIlY HXOJ2lqUzOReTrie2u0qcSvGAbSfec9apTFl2Xko/ddqPcZMpKhBiXmY8tJzSPk3+G4tqur4 6TYAm5ouitJsgAR61Cu7s+PNuq/pTLDhK+6/Njmc94NGBcRA4qTuysEGE79vYWP2oIAU4Fv6 gqaWHZ4MEI2XTqH8wiwzPdCQPYsSE0fXWiYu7ObeErT6iLSTZGx4rQARAQABiQIfBBgBCAAJ BQJbm6Q+AhsMAAoJEONU5rjiOLn4DDEP/RuyckW65SZcPG4cMfNgWxZF8rVjeVl/9PBfy01K 8R0hajU40bWtXSMiby7j0/dMjz99jN6L+AJHJvrLz4qYRzn2Ys843W+RfXj62Zde4YNBE5SL jJweRCbMWKaJLj6499fctxTyeb9+AMLQS4yRSwHuAZLmAb5AyCW1gBcTWZb8ON5BmWnRqeGm IgC1EvCnHy++aBnHTn0m+zV89BhTLTUal35tcjUFwluBY39R2ux/HNlBO1GY3Z+WYXhBvq7q katThLjaQSmnOrMhzqYmdShP1leFTVbzXUUIYv/GbynO/YrL2gaQpaP1bEUEi8lUAfXJbEWG dnHFkciryi092E8/9j89DJg4mmZqOau7TtUxjRMlBcIliXkzSLUk+QvD4LK1kWievJse4mte FBdkWHfP4BH/+8DxapRcG1UAheSnSRQ5LiO50annOB7oXF+vgKIaie2TBfZxQNGAs3RQ+bga DchCqFm5adiSP5+OT4NjkKUeGpBe/aRyQSle/RropTgCi85pje/juYEn2P9UAgkfBJrOHvQ9 Z+2Sva8FRd61NJLkCJ4LFumRn9wQlX2icFbi8UDV3do0hXJRRYTWCxrHscMhkrFWLhYiPF4i phX7UNdOWBQ90qpHyAxHmDazdo27gEjfvsgYMdveKknEOTEb5phwxWgg7BcIDoJf9UMC Message-ID: <36e1c11c-c4a2-6ae2-b341-7d582203d031@linux.ibm.com> Date: Fri, 4 Sep 2020 13:33:28 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200904103543.GD6075@osiris> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="R0pLoHIvQxnoeDOKoMKKZHuT4PSxwBQtC" X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-09-04_06:2020-09-04,2020-09-04 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 phishscore=0 adultscore=0 mlxlogscore=999 spamscore=0 bulkscore=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0 clxscore=1015 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009040100 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --R0pLoHIvQxnoeDOKoMKKZHuT4PSxwBQtC Content-Type: multipart/mixed; boundary="gTcbVriBs7lyOx8yYKq2peyJQlKqyu5Tr" --gTcbVriBs7lyOx8yYKq2peyJQlKqyu5Tr Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 9/4/20 12:35 PM, Heiko Carstens wrote: > On Thu, Sep 03, 2020 at 09:14:35AM -0400, Janosch Frank wrote: >> Program exception 3f (secure storage violation) can only be detected >> when the CPU is running in SIE with a format 4 state description, >> e.g. running a protected guest. Because of this and because user >> space partly controls the guest memory mapping and can trigger this >> exception, we want to send a SIGSEGV to the process running the guest >> and not panic the kernel. >> >> Signed-off-by: Janosch Frank >> CC: # 5.7+ >> Fixes: 084ea4d611a3 ("s390/mm: add (non)secure page access exceptions = handlers") >> Reviewed-by: Claudio Imbrenda >> --- >> arch/s390/kernel/pgm_check.S | 2 +- >> arch/s390/mm/fault.c | 23 +++++++++++++++++++++++ >> 2 files changed, 24 insertions(+), 1 deletion(-) >> >> diff --git a/arch/s390/kernel/pgm_check.S b/arch/s390/kernel/pgm_check= =2ES >> index 2c27907a5ffc..9a92638360ee 100644 >> --- a/arch/s390/kernel/pgm_check.S >> +++ b/arch/s390/kernel/pgm_check.S >> @@ -80,7 +80,7 @@ PGM_CHECK(do_dat_exception) /* 3b */ >> PGM_CHECK_DEFAULT /* 3c */ >> PGM_CHECK(do_secure_storage_access) /* 3d */ >> PGM_CHECK(do_non_secure_storage_access) /* 3e */ >> -PGM_CHECK_DEFAULT /* 3f */ >> +PGM_CHECK(do_secure_storage_violation) /* 3f */ >> PGM_CHECK(monitor_event_exception) /* 40 */ >> PGM_CHECK_DEFAULT /* 41 */ >> PGM_CHECK_DEFAULT /* 42 */ >> diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c >> index 4c8c063bce5b..20abb7c5c540 100644 >> --- a/arch/s390/mm/fault.c >> +++ b/arch/s390/mm/fault.c >> @@ -859,6 +859,24 @@ void do_non_secure_storage_access(struct pt_regs = *regs) >> } >> NOKPROBE_SYMBOL(do_non_secure_storage_access); >> =20 >> +void do_secure_storage_violation(struct pt_regs *regs) >> +{ >> + char buf[TASK_COMM_LEN]; >> + >> + /* >> + * Either KVM messed up the secure guest mapping or the same >> + * page is mapped into multiple secure guests. >> + * >> + * This exception is only triggered when a guest 2 is running >> + * and can therefore never occur in kernel context. >> + */ >> + printk_ratelimited(KERN_WARNING >> + "Secure storage violation in task: %s, pid %d\n", >> + get_task_comm(buf, current), task_pid_nr(current)); >=20 > Why get_task_comm() and task_pid_nr() instead of simply current->comm > and current->pid? Normally if there are functions to get data I assume those should be used= =2E > Also: is the dmesg message of any value? Yes, it's import for administrators to know that an exception caused this segfault and not some memory shenanigans. As the exception only occurs if a guest runs in unsupported modes like sharing the memory between two secure guests it's a good first indication what went wrong. >=20 >> + send_sig(SIGSEGV, current, 0); >> +} >> +NOKPROBE_SYMBOL(do_secure_storage_violation);> > Why is this NOKPROBE? Can this deadlock? Right, we don't need to export this at all, this was copied over from the export function above. --gTcbVriBs7lyOx8yYKq2peyJQlKqyu5Tr-- --R0pLoHIvQxnoeDOKoMKKZHuT4PSxwBQtC Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEwGNS88vfc9+v45Yq41TmuOI4ufgFAl9SJggACgkQ41TmuOI4 ufijEA//ci8Z+hrIydllOPAvpGImC3hQj3IEKWQSA7AEXvSVKbNV5SoBiAFcmCKy UaK79mI3VbgydHpDx6THvgZ3qNGjHGomCJ2WxKFmi+Y03a8tMP0XWFeSEn7dC1a+ 1R7CWVvA9b/ZpwzZ3BxdkHxw06vs5pUZryiUQCMtJLdwhxAnYJe1Mggr13CsC4QD djjUQ2dKWBfwBLFIivFXQWIKlG6RA545vtMQNvs7YFY/+0PXNNMnc/zpAkOU5muJ WHI4G38iXVhvlIcmpcB7fEDu4fXWHyHZnEWVWh/e5tsabWPwpd0jHZuYjRWyg9bu ySBOJeEkirBXkrddHVdcp7553hnezs9VtwSSzZ/FT1lJ17tF4+St6KJcdhsE8UKL HY0brhmPfNaS0bmSby5X8lp0KvGZLclSLypXO/8XD3UMXVR5UI00J39apo70BKsm WuwzxFjPOz4Ia2qofKPWbzzih5uQQKDAxlP7QOR3Z45+wyO79zAMrPEK3fSa1aVb CnXScEtaBe1I9iY5tr6RLcrubKpI763ST9TA1YoOa8S/4JddJANljJ91BmC40Ij7 CksJMQNkGApCTmWzSGVhANVKLM8KH5zc3vCdPoNGKlr02bhVz/BOKg+vmljg+xUS x7C73Qgy2sSfK20KZZ8heDUMLSmYCWGuqFxneIq8XnR/DShTfZw= =CCcz -----END PGP SIGNATURE----- --R0pLoHIvQxnoeDOKoMKKZHuT4PSxwBQtC--