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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 20021318-0016-0000-0000-000002E68AC1 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20021318-0017-0000-0000-000033498E68 Message-Id: <941cc201-4c33-0ad3-ecc8-eab2709d350d@de.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.572 definitions=2020-02-13_06:2020-02-12, 2020-02-13 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 adultscore=0 malwarescore=0 mlxscore=0 impostorscore=0 phishscore=0 priorityscore=1501 suspectscore=0 lowpriorityscore=0 mlxlogscore=999 spamscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002130129 Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by mx0a-001b2d01.pphosted.com id 01DIIriE149134 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] X-Received-From: 148.163.156.1 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" On 13.02.20 19:02, Jason J. Herne wrote: > On 2/6/20 5:09 AM, 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 overwri= tten when >>> we=C2=A0 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 natura= lly align >>> on an 8-byte boundary. >>> >>> Fixes: 5c6f0d5f46a7 ("pc-bios/s390x: Fix reset psw mask") >>> CC: Janosch Frank >>> Signed-off-by: Jason J. Herne >>> --- >>> =C2=A0 pc-bios/s390-ccw/jump2ipl.c | 2 +- >>> =C2=A0 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 @@ >>> =C2=A0 typedef struct ResetInfo { >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 uint64_t ipl_psw; >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 uint32_t ipl_continue; >>> -} ResetInfo; >>> +} __attribute__((packed)) ResetInfo; >>> =C2=A0 =C2=A0 static ResetInfo save; >> >> Just looked into that. >> >> We do save the old content in "save" and restore the old memory conten= t. >> >> static void jump_to_IPL_2(void) >> { >> =C2=A0=C2=A0=C2=A0=C2=A0 ResetInfo *current =3D 0; >> >> =C2=A0=C2=A0=C2=A0=C2=A0 void (*ipl)(void) =3D (void *) (uint64_t) cur= rent->ipl_continue; >> --->*current =3D save; >> =C2=A0=C2=A0=C2=A0=C2=A0 ipl(); /* should not return */ >> } >> >> void jump_to_IPL_code(uint64_t address) >> { >> =C2=A0=C2=A0=C2=A0=C2=A0 /* store the subsystem information _after_ th= e bootmap was loaded */ >> =C2=A0=C2=A0=C2=A0=C2=A0 write_subsystem_identification(); >> >> =C2=A0=C2=A0=C2=A0=C2=A0 /* prevent unknown IPL types in the guest */ >> =C2=A0=C2=A0=C2=A0=C2=A0 if (iplb.pbt =3D=3D S390_IPL_TYPE_QEMU_SCSI) = { >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 iplb.pbt =3D S390_IPL= _TYPE_CCW; >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 set_iplb(&iplb); >> =C2=A0=C2=A0=C2=A0=C2=A0 } >> >> =C2=A0=C2=A0=C2=A0=C2=A0 /* >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * The IPL PSW is at address 0. We also = must not overwrite the >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * content of non-BIOS memory after we l= oaded the guest, so we >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * save the original content and restore= it in jump_to_IPL_2. >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */ >> =C2=A0=C2=A0=C2=A0=C2=A0 ResetInfo *current =3D 0; >> >> --->save =3D *current; >> >> >> >> does something like >> >> >> diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c >> index da13c43cc0..8839226803 100644 >> --- a/pc-bios/s390-ccw/jump2ipl.c >> +++ b/pc-bios/s390-ccw/jump2ipl.c >> @@ -18,6 +18,7 @@ >> =C2=A0 typedef struct ResetInfo { >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 uint64_t ipl_psw; >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 uint32_t ipl_continue; >> +=C2=A0=C2=A0=C2=A0 uint32_t pad; >> =C2=A0 } ResetInfo; >> =C2=A0 =C2=A0 static ResetInfo save; >> >> >> also work? If yes, both variants are valid. Either packed or explicit = padding. >> >=20 > I don't believe this will work. I think the problem is that we're overw= riting too much memory when we cast address 0 as a ResetInfo and then ove= rwrite it (*current =3D save). I think we need the struct to be sized at = 12-bytes instead of 16. >=20 The idea of the code is that we _save_ the original content from address = 0 to save and _restore_ it before jumping into final code. I do not yet u= nderstand why this does not work.