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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 7 Feb 2020 11:28:12 -0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 017BSBdQ50659552 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 7 Feb 2020 11:28:11 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C0919A4060; Fri, 7 Feb 2020 11:28:11 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 921FFA405B; Fri, 7 Feb 2020 11:28:11 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.152.224.61]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 7 Feb 2020 11:28:11 +0000 (GMT) Subject: Re: [PATCH] pc-bios/s390x: Pack ResetInfo struct To: Thomas Huth , "Jason J. Herne" , qemu-devel@nongnu.org, qemu-s390x@nongnu.org, cohuck@redhat.com References: <20200205182126.13010-1-jjherne@linux.ibm.com> <896302f7-ec21-6108-6dde-f5a7439d87ab@redhat.com> From: Christian Borntraeger Autocrypt: addr=borntraeger@de.ibm.com; prefer-encrypt=mutual; keydata= xsFNBE6cPPgBEAC2VpALY0UJjGmgAmavkL/iAdqul2/F9ONz42K6NrwmT+SI9CylKHIX+fdf J34pLNJDmDVEdeb+brtpwC9JEZOLVE0nb+SR83CsAINJYKG3V1b3Kfs0hydseYKsBYqJTN2j CmUXDYq9J7uOyQQ7TNVoQejmpp5ifR4EzwIFfmYDekxRVZDJygD0wL/EzUr8Je3/j548NLyL 4Uhv6CIPf3TY3/aLVKXdxz/ntbLgMcfZsDoHgDk3lY3r1iwbWwEM2+eYRdSZaR4VD+JRD7p8 0FBadNwWnBce1fmQp3EklodGi5y7TNZ/CKdJ+jRPAAnw7SINhSd7PhJMruDAJaUlbYaIm23A +82g+IGe4z9tRGQ9TAflezVMhT5J3ccu6cpIjjvwDlbxucSmtVi5VtPAMTLmfjYp7VY2Tgr+ T92v7+V96jAfE3Zy2nq52e8RDdUo/F6faxcumdl+aLhhKLXgrozpoe2nL0Nyc2uqFjkjwXXI OBQiaqGeWtxeKJP+O8MIpjyGuHUGzvjNx5S/592TQO3phpT5IFWfMgbu4OreZ9yekDhf7Cvn /fkYsiLDz9W6Clihd/xlpm79+jlhm4E3xBPiQOPCZowmHjx57mXVAypOP2Eu+i2nyQrkapaY IdisDQfWPdNeHNOiPnPS3+GhVlPcqSJAIWnuO7Ofw1ZVOyg/jwARAQABzUNDaHJpc3RpYW4g Qm9ybnRyYWVnZXIgKDJuZCBJQk0gYWRkcmVzcykgPGJvcm50cmFlZ2VyQGxpbnV4LmlibS5j b20+wsF5BBMBAgAjBQJdP/hMAhsDBwsJCAcDAgEGFQgCCQoLBBYCAwECHgECF4AACgkQEXu8 gLWmHHy/pA/+JHjpEnd01A0CCyfVnb5fmcOlQ0LdmoKWLWPvU840q65HycCBFTt6V62cDljB kXFFxMNA4y/2wqU0H5/CiL963y3gWIiJsZa4ent+KrHl5GK1nIgbbesfJyA7JqlB0w/E/SuY NRQwIWOo/uEvOgXnk/7+rtvBzNaPGoGiiV1LZzeaxBVWrqLtmdi1iulW/0X/AlQPuF9dD1Px hx+0mPjZ8ClLpdSp5d0yfpwgHtM1B7KMuQPQZGFKMXXTUd3ceBUGGczsgIMipZWJukqMJiJj QIMH0IN7XYErEnhf0GCxJ3xAn/J7iFpPFv8sFZTvukntJXSUssONnwiKuld6ttUaFhSuSoQg OFYR5v7pOfinM0FcScPKTkrRsB5iUvpdthLq5qgwdQjmyINt3cb+5aSvBX2nNN135oGOtlb5 tf4dh00kUR8XFHRrFxXx4Dbaw4PKgV3QLIHKEENlqnthH5t0tahDygQPnSucuXbVQEcDZaL9 WgJqlRAAj0pG8M6JNU5+2ftTFXoTcoIUbb0KTOibaO9zHVeGegwAvPLLNlKHiHXcgLX1tkjC DrvE2Z0e2/4q7wgZgn1kbvz7ZHQZB76OM2mjkFu7QNHlRJ2VXJA8tMXyTgBX6kq1cYMmd/Hl OhFrAU3QO1SjCsXA2CDk9MM1471mYB3CTXQuKzXckJnxHkHOwU0ETpw8+AEQAJjyNXvMQdJN t07BIPDtbAQk15FfB0hKuyZVs+0lsjPKBZCamAAexNRk11eVGXK/YrqwjChkk60rt3q5i42u PpNMO9aS8cLPOfVft89Y654Qd3Rs1WRFIQq9xLjdLfHh0i0jMq5Ty+aiddSXpZ7oU6E+ud+X Czs3k5RAnOdW6eV3+v10sUjEGiFNZwzN9Udd6PfKET0J70qjnpY3NuWn5Sp1ZEn6lkq2Zm+G 9G3FlBRVClT30OWeiRHCYB6e6j1x1u/rSU4JiNYjPwSJA8EPKnt1s/Eeq37qXXvk+9DYiHdT PcOa3aNCSbIygD3jyjkg6EV9ZLHibE2R/PMMid9FrqhKh/cwcYn9FrT0FE48/2IBW5mfDpAd YvpawQlRz3XJr2rYZJwMUm1y+49+1ZmDclaF3s9dcz2JvuywNq78z/VsUfGz4Sbxy4ShpNpG REojRcz/xOK+FqNuBk+HoWKw6OxgRzfNleDvScVmbY6cQQZfGx/T7xlgZjl5Mu/2z+ofeoxb vWWM1YCJAT91GFvj29Wvm8OAPN/+SJj8LQazd9uGzVMTz6lFjVtH7YkeW/NZrP6znAwv5P1a DdQfiB5F63AX++NlTiyA+GD/ggfRl68LheSskOcxDwgI5TqmaKtX1/8RkrLpnzO3evzkfJb1 D5qh3wM1t7PZ+JWTluSX8W25ABEBAAHCwV8EGAECAAkFAk6cPPgCGwwACgkQEXu8gLWmHHz8 2w//VjRlX+tKF3szc0lQi4X0t+pf88uIsvR/a1GRZpppQbn1jgE44hgF559K6/yYemcvTR7r 6Xt7cjWGS4wfaR0+pkWV+2dbw8Xi4DI07/fN00NoVEpYUUnOnupBgychtVpxkGqsplJZQpng v6fauZtyEcUK3dLJH3TdVQDLbUcL4qZpzHbsuUnTWsmNmG4Vi0NsEt1xyd/Wuw+0kM/oFEH1 4BN6X9xZcG8GYUbVUd8+bmio8ao8m0tzo4pseDZFo4ncDmlFWU6hHnAVfkAs4tqA6/fl7RLN JuWBiOL/mP5B6HDQT9JsnaRdzqF73FnU2+WrZPjinHPLeE74istVgjbowvsgUqtzjPIG5pOj cAsKoR0M1womzJVRfYauWhYiW/KeECklci4TPBDNx7YhahSUlexfoftltJA8swRshNA/M90/ i9zDo9ySSZHwsGxG06ZOH5/MzG6HpLja7g8NTgA0TD5YaFm/oOnsQVsf2DeAGPS2xNirmknD jaqYefx7yQ7FJXXETd2uVURiDeNEFhVZWb5CiBJM5c6qQMhmkS4VyT7/+raaEGgkEKEgHOWf ZDP8BHfXtszHqI3Fo1F4IKFo/AP8GOFFxMRgbvlAs8z/+rEEaQYjxYJqj08raw6P4LFBqozr nS4h0HDFPrrp1C2EMVYIQrMokWvlFZbCpsdYbBI= Date: Fri, 7 Feb 2020 12:28:11 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <896302f7-ec21-6108-6dde-f5a7439d87ab@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20020711-0008-0000-0000-00000350A707 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20020711-0009-0000-0000-00004A713E0B Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.572 definitions=2020-02-07_01:2020-02-07, 2020-02-06 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 clxscore=1011 impostorscore=0 malwarescore=0 priorityscore=1501 adultscore=0 mlxlogscore=999 suspectscore=0 bulkscore=0 lowpriorityscore=0 spamscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002070088 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] X-Received-From: 148.163.158.5 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Jason, can you run objdump -Sdr on jump2ipl.o on a broken variant? On 06.02.20 12:00, Thomas Huth wrote: > On 06/02/2020 11.09, Christian Borntraeger wrote: >> >> >> On 05.02.20 19:21, Jason J. Herne wrote: >>> This fixes vfio-ccw when booting non-Linux operating systems. Without this >>> struct being packed, a few extra bytes of low core memory get overwritten when >>> we assign a value to memory address 0 in jump_to_IPL_2. This is enough to >>> cause some non-Linux OSes of fail when booting. >>> >>> The problem was introduced by: >>> 5c6f0d5f46a77d77 "pc-bios/s390x: Fix reset psw mask". >>> >>> The fix is to pack the struct thereby removing the 4 bytes of padding that get >>> added at the end, likely to allow an array of these structs to naturally align >>> on an 8-byte boundary. >>> >>> Fixes: 5c6f0d5f46a7 ("pc-bios/s390x: Fix reset psw mask") >>> CC: Janosch Frank >>> Signed-off-by: Jason J. Herne >>> --- >>> pc-bios/s390-ccw/jump2ipl.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c >>> index da13c43cc0..1e9eaa037f 100644 >>> --- a/pc-bios/s390-ccw/jump2ipl.c >>> +++ b/pc-bios/s390-ccw/jump2ipl.c >>> @@ -18,7 +18,7 @@ >>> typedef struct ResetInfo { >>> uint64_t ipl_psw; >>> uint32_t ipl_continue; >>> -} ResetInfo; >>> +} __attribute__((packed)) ResetInfo; >>> >>> static ResetInfo save; >> >> Just looked into that. >> >> We do save the old content in "save" and restore the old memory content. >> >> static void jump_to_IPL_2(void) >> { >> ResetInfo *current = 0; >> >> void (*ipl)(void) = (void *) (uint64_t) current->ipl_continue; >> --->*current = save; >> ipl(); /* should not return */ >> } >> >> void jump_to_IPL_code(uint64_t address) >> { >> /* store the subsystem information _after_ the bootmap was loaded */ >> write_subsystem_identification(); >> >> /* prevent unknown IPL types in the guest */ >> if (iplb.pbt == S390_IPL_TYPE_QEMU_SCSI) { >> iplb.pbt = S390_IPL_TYPE_CCW; >> set_iplb(&iplb); >> } >> >> /* >> * The IPL PSW is at address 0. We also must not overwrite the >> * content of non-BIOS memory after we loaded the guest, so we >> * save the original content and restore it in jump_to_IPL_2. >> */ >> ResetInfo *current = 0; >> >> --->save = *current; > > Right, and this should also work without your modification. I've stared > at the code a couple of weeks ago, looking for a very similar issue: > > https://lists.gnu.org/archive/html/qemu-devel/2019-12/msg03484.html > > ... but in the end, the problem was something else: > > https://lists.gnu.org/archive/html/qemu-devel/2019-12/msg03520.html > > and the fix had been done in the startup code of the test: > > https://lists.gnu.org/archive/html/qemu-devel/2019-12/msg04225.html > > So I'd guess that you face the very same problem here. That means, you > either have to convince the non-Linux OS to check their startup code > whether they depend on zeroed registers somewhere, or we fix this issue > for good in jump_to_IPL_2() by clearing the registers there before > jumping into the OS code (which we likely should do anyway since the OS > may expect a clean state). > > Thomas > >