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Wed, 22 Jul 2020 08:05:54 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F1489A4062; Wed, 22 Jul 2020 08:05:53 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 999B8A405C; Wed, 22 Jul 2020 08:05:53 +0000 (GMT) Received: from localhost.localdomain (unknown [9.145.169.63]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 22 Jul 2020 08:05:53 +0000 (GMT) Subject: Re: [PATCH] pc-bios: s390x: Add a comment to the io and external new PSW setup To: Christian Borntraeger , qemu-devel@nongnu.org References: <033b0db7-7b7d-6eb0-9018-bcc342f13509@de.ibm.com> <20200715140820.3401-1-frankja@linux.ibm.com> <3216babd-433b-4ec7-5333-43a75df2e331@de.ibm.com> <2e6134fb-3e34-4d3a-1bf8-1665ceffef38@de.ibm.com> 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: Date: Wed, 22 Jul 2020 10:05:53 +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: <2e6134fb-3e34-4d3a-1bf8-1665ceffef38@de.ibm.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="KVP8ySZ9JH0NvRpzZnHODUlmqqda8d5hi" X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-07-22_03:2020-07-22, 2020-07-22 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 priorityscore=1501 bulkscore=0 mlxlogscore=999 clxscore=1015 phishscore=0 mlxscore=0 lowpriorityscore=0 suspectscore=0 impostorscore=0 adultscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007220061 Received-SPF: pass client-ip=148.163.156.1; envelope-from=frankja@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/22 02:50:42 X-ACL-Warn: Detected OS = Linux 3.x [generic] [fuzzy] X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-1, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: thuth@redhat.com, cohuck@redhat.com, david@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --KVP8ySZ9JH0NvRpzZnHODUlmqqda8d5hi Content-Type: multipart/mixed; boundary="3CEmtN9ZyS6Q3rKd3GbygFp76aliqiolf" --3CEmtN9ZyS6Q3rKd3GbygFp76aliqiolf Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 7/22/20 9:39 AM, Christian Borntraeger wrote: >=20 >=20 > On 22.07.20 09:24, Janosch Frank wrote: >> On 7/22/20 8:43 AM, Christian Borntraeger wrote: >>> >>> >>> On 15.07.20 16:08, Janosch Frank wrote: >>>> Normally they don't need to be set up before waiting for an interrup= t >>>> but are set up on boot. The BIOS however might overwrite the lowcore= >>>> (and hence the PSWs) when loading a blob into memory and therefore >>>> needs to set up those PSWs more often. >>> >>> Now when I read the new comment this actually inidicates a bug.=20 >>> When do we restore the original content? If the loaded program >>> does have interrupt handlers in the original image and relies on that= >>> then we are broken, no? >> >> I haven't seen references to a save/restore functionality for those >> PSWs. And I also think it's not that easy to do because we have multip= le >> ways of loading data and if we want to print when loading we might end= >> up overwriting and then saving the written value for a later restore. >> >> I need to have a closer look at how virtio works, but wouldn't we have= a >> chicken - egg problem with IO interrupts for IO that writes the prefix= ? >> >> The BIOS often has "interesting" solutions to problems. >> If you have a quick fix, be my guest and send it. If not I'd put it on= >> my todo list or let Stefan make it a proper dev item. >=20 > Maybe a global fixup table in BIOS memory that restores all the memory = that > we messed with when we hand over control? Can you at least change the c= omment > here to add a fixme? Sure >=20 >> >>> >>>> >>>> Signed-off-by: Janosch Frank >>>> --- >>>> pc-bios/s390-ccw/start.S | 10 ++++++++-- >>>> 1 file changed, 8 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/pc-bios/s390-ccw/start.S b/pc-bios/s390-ccw/start.S >>>> index 01c4c21b26..b0fcb918cc 100644 >>>> --- a/pc-bios/s390-ccw/start.S >>>> +++ b/pc-bios/s390-ccw/start.S >>>> @@ -64,7 +64,10 @@ consume_sclp_int: >>>> stctg %c0,%c0,0(%r15) >>>> oi 6(%r15),0x2 >>>> lctlg %c0,%c0,0(%r15) >>>> - /* prepare external call handler */ >>>> + /* >>>> + * Prepare external new PSW as it might have been overwritt= en >>>> + * by a loaded blob >>>> + */ >>>> larl %r1, external_new_code >>>> stg %r1, 0x1b8 >>>> larl %r1, external_new_mask >>>> @@ -84,7 +87,10 @@ consume_io_int: >>>> stctg %c6,%c6,0(%r15) >>>> oi 4(%r15), 0xff >>>> lctlg %c6,%c6,0(%r15) >>>> - /* prepare i/o call handler */ >>>> + /* >>>> + * Prepare i/o new PSW as it might have been overwritten >>>> + * by a loaded blob >>>> + */ >>>> larl %r1, io_new_code >>>> stg %r1, 0x1f8 >>>> larl %r1, io_new_mask >>>> >> >> --3CEmtN9ZyS6Q3rKd3GbygFp76aliqiolf-- --KVP8ySZ9JH0NvRpzZnHODUlmqqda8d5hi Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEwGNS88vfc9+v45Yq41TmuOI4ufgFAl8X82EACgkQ41TmuOI4 ufhu+A/8Cy8mEmR3Z+VT+5vkn1ZD9d35Cq8RP6TDc/+m/vOfav9sMuIAYUpoWIAN oKKU7ZFgifigrh61dBxwo3g3Lt7bziNMR8VuAj74nTxBeZ8YpGdDQkUKPpG2N39B tdva386bxdvFUw+bGgOGCnwB1M+zrLcv0AozKkoQvjlqNunVy0zsUkS+HiH6ZKS2 SEODPN7TQQiT3S4deRPUFODF7EgQ9kGGrKAhWxiQojWUOYamWrVQfkEzqnZZ97Wr 2OGHw+avrEvJ52AQN7hpunXQTWBDv0FNxKhacFcwN63t/cGG3yBVSdX5eVUDv9s0 c8Ig6a+N8lpZINXS1MK7nAB8ej/shlTcxdR6lPp17DV7asElJY+SdABIuL4wcjtd Xugg13QJiA8ZCyJ6rP1Mr7HSQU0xDna0uQo2jKu18l8KEOLYJvn7oFrdMcMmqV4u O7nlSdrPgswwjQVe6JWpsf/Lrs5/2llxS6DePvAJpsDTPISQUFqdJCu6/GEeky0x S3ZjzDf6Px6RuU511q7UuxjpaMeCOyj1dRUCxN/iZoRF/aWeOGJfbvfOb1lYwgxh +c6gUusjOtvzed7T9jhNb2LjSSLinldcNBtfiROe5DioGavsjnCtE9q7gmbWuBLS tfaQBMxZ6IkqvUSjFvc+WG7m2qWpPnz7o9yajHVadctH0Pawl0M= =g1te -----END PGP SIGNATURE----- --KVP8ySZ9JH0NvRpzZnHODUlmqqda8d5hi--