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Tue, 16 Apr 2024 20:58:11 +0000 (GMT) From: Gaurav Batra To: mpe@ellerman.id.au Subject: [PATCH] powerpc/pseries/iommu: LPAR panics when rebooted with a frozen PE Date: Tue, 16 Apr 2024 15:58:10 -0500 Message-Id: <20240416205810.28754-1-gbatra@linux.ibm.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: FFIbu3AmgFr5jzFif36LvECCj2PoSxqU X-Proofpoint-ORIG-GUID: FFIbu3AmgFr5jzFif36LvECCj2PoSxqU X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-04-16_18,2024-04-16_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 lowpriorityscore=0 suspectscore=0 spamscore=0 bulkscore=0 adultscore=0 mlxlogscore=999 impostorscore=0 mlxscore=0 priorityscore=1501 malwarescore=0 clxscore=1011 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2404010000 definitions=main-2404160134 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Gaurav Batra , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" At the time of LPAR reboot, partition firmware provides Open Firmware property ibm,dma-window for the PE. This property is provided on the PCI bus the PE is attached to. There are execptions where the partition firmware might not provide this property for the PE at the time of LPAR reboot. One of the scenario is where the firmware has frozen the PE due to some error conditions. This PE is frozen for 24 hours or unless the whole system is reinitialized. Within this time frame, if the LPAR is rebooted, the frozen PE will be presented to the LPAR but ibm,dma-window property could be missing. Today, under these circumstances, the LPAR oopses with NULL pointer dereference, when configuring the PCI bus the PE is attached to. BUG: Kernel NULL pointer dereference on read at 0x000000c8 Faulting instruction address: 0xc0000000001024c0 Oops: Kernel access of bad area, sig: 7 [#1] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries Modules linked in: Supported: Yes CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.4.0-150600.9-default #1 Hardware name: IBM,9043-MRX POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1060.00 (NM1060_023) hv:phyp pSeries NIP: c0000000001024c0 LR: c0000000001024b0 CTR: c000000000102450 REGS: c0000000037db5c0 TRAP: 0300 Not tainted (6.4.0-150600.9-default) MSR: 8000000002009033 CR: 28000822 XER: 00000000 CFAR: c00000000010254c DAR: 00000000000000c8 DSISR: 00080000 IRQMASK: 0 ... NIP [c0000000001024c0] pci_dma_bus_setup_pSeriesLP+0x70/0x2a0 LR [c0000000001024b0] pci_dma_bus_setup_pSeriesLP+0x60/0x2a0 Call Trace: pci_dma_bus_setup_pSeriesLP+0x60/0x2a0 (unreliable) pcibios_setup_bus_self+0x1c0/0x370 __of_scan_bus+0x2f8/0x330 pcibios_scan_phb+0x280/0x3d0 pcibios_init+0x88/0x12c do_one_initcall+0x60/0x320 kernel_init_freeable+0x344/0x3e4 kernel_init+0x34/0x1d0 ret_from_kernel_user_thread+0x14/0x1c Fixes: b1fc44eaa9ba ("pseries/iommu/ddw: Fix kdump to work in absence of ibm,dma-window") Signed-off-by: Gaurav Batra --- arch/powerpc/platforms/pseries/iommu.c | 8 ++++++++ 1 file changed, 8 insertions(+) base-commit: 2c71fdf02a95b3dd425b42f28fd47fb2b1d22702 diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c index e8c4129697b1..e808d5b1fa49 100644 --- a/arch/powerpc/platforms/pseries/iommu.c +++ b/arch/powerpc/platforms/pseries/iommu.c @@ -786,8 +786,16 @@ static void pci_dma_bus_setup_pSeriesLP(struct pci_bus *bus) * parent bus. During reboot, there will be ibm,dma-window property to * define DMA window. For kdump, there will at least be default window or DDW * or both. + * There is an exception to the above. In case the PE goes into frozen + * state, firmware may not provide ibm,dma-window property at the time + * of LPAR reboot. */ + if (!pdn) { + pr_debug(" no ibm,dma-window property !\n"); + return; + } + ppci = PCI_DN(pdn); pr_debug(" parent is %pOF, iommu_table: 0x%p\n",