Re: [Crash-utility] [PATCH] ppc64: do page traversal if vmemmap_list not populated

Hi, Aditya Thank you for the patch. On Mon, Sep 11, 2023 at 8:00 PM <crash-utility-request(a)redhat.com&gt; wrote: Can you help to describe in detail how to reproduce this issue? Or does this require any kernel configs to be enabled first? I did not reproduce the current issue with '/proc/kcore' or vmcore(via cp). Test kernel commit: ce9ecca0238b ("Linux 6.6-rc2") # ./crash /home/linux/vmlinux /var/crash/127.0.0.1-2023-09-18-06\:58\:57/vmcore crash 8.0.3++ Copyright (C) 2002-2022 Red Hat, Inc. Copyright (C) 2004, 2005, 2006, 2010 IBM Corporation Copyright (C) 1999-2006 Hewlett-Packard Co Copyright (C) 2005, 2006, 2011, 2012 Fujitsu Limited Copyright (C) 2006, 2007 VA Linux Systems Japan K.K. Copyright (C) 2005, 2011, 2020-2022 NEC Corporation Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc. Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc. Copyright (C) 2015, 2021 VMware, Inc. 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KERNEL: /home/linux/vmlinux DUMPFILE: /var/crash/127.0.0.1-2023-09-18-06:58:57/vmcore CPUS: 8 DATE: Mon Sep 18 06:57:40 EDT 2023 UPTIME: 00:03:19 LOAD AVERAGE: 0.20, 0.31, 0.14 TASKS: 186 NODENAME: ibm-p9z-16-lp10.khw3.lab.eng.bos.redhat.com RELEASE: 6.6.0-rc2 VERSION: #2 SMP Mon Sep 18 06:11:14 EDT 2023 MACHINE: ppc64le (2800 Mhz) MEMORY: 16 GB PANIC: "Kernel panic - not syncing: sysrq triggered crash" PID: 4337 COMMAND: "bash" TASK: c000000052a49900 [THREAD_INFO: c000000052a49900] CPU: 3 STATE: TASK_RUNNING (PANIC) crash Thanks Lianbo also fails in absence of 'vmemmap_list' in upstream linux > The fix for makedumpfile will also been sent to upstream > --- > --- > ppc64.c | 47 +++++++++++++++++++++++++++++++++-------------- > 1 file changed, 33 insertions(+), 14 deletions(-) > diff --git a/ppc64.c b/ppc64.c > index fc34006f4863..1e84c5f56773 100644 > --- a/ppc64.c > +++ b/ppc64.c > @@ -1280,8 +1280,30 @@ void ppc64_vmemmap_init(void) > long backing_size, virt_addr_offset, phys_offset, list_offset; > ulong *vmemmap_list; > char *vmemmap_buf; > - struct machine_specific *ms; > - > + struct machine_specific *ms = machdep->machspec; > + > + ld = &list_data; > + BZERO(ld, sizeof(struct list_data)); > + > + /* > + * vmemmap_list is missing or set to 0 in the kernel would imply > + * vmemmap region is mapped in the kernel pagetable. So, read > vmemmap_list > + * anyway and use the translation method accordingly. > + */ > + readmem(symbol_value("vmemmap_list"), KVADDR, &ld->start, > sizeof(void *), > + "vmemmap_list", RETURN_ON_ERROR); > + if (!ld->start) { > + /* > + * vmemmap_list is set to 0 or missing. Do kernel > pagetable walk > + * for vmemmamp address translation. > + */ > + ms->vmemmap_list = NULL; > + ms->vmemmap_cnt = 0; > + > + machdep->flags |= VMEMMAP_AWARE; > + return; > + } > + > if (!(kernel_symbol_exists("vmemmap_list")) || > !(kernel_symbol_exists("mmu_psize_defs")) || > !(kernel_symbol_exists("mmu_vmemmap_psize")) || > @@ -1293,8 +1315,6 @@ void ppc64_vmemmap_init(void) > !MEMBER_EXISTS("vmemmap_backing", "list")) > return; > - ms = machdep->machspec; > - > backing_size = STRUCT_SIZE("vmemmap_backing"); > virt_addr_offset = MEMBER_OFFSET("vmemmap_backing", "virt_addr"); > phys_offset = MEMBER_OFFSET("vmemmap_backing", "phys"); > @@ -1313,14 +1333,8 @@ void ppc64_vmemmap_init(void) > ms->vmemmap_psize = 1 << shift; > - ld = &list_data; > - BZERO(ld, sizeof(struct list_data)); > - if (!readmem(symbol_value("vmemmap_list"), > - KVADDR, &ld->start, sizeof(void *), "vmemmap_list", > - RETURN_ON_ERROR)) > - return; > - ld->end = symbol_value("vmemmap_list"); > - ld->list_head_offset = list_offset; > + ld->end = symbol_value("vmemmap_list"); > + ld->list_head_offset = list_offset; > hq_open(); > cnt = do_list(ld); > @@ -1366,7 +1380,7 @@ ppc64_vmemmap_to_phys(ulong kvaddr, physaddr_t > *paddr, int verbose) > { > int i; > ulong offset; > - struct machine_specific *ms; > + struct machine_specific *ms = machdep->machspec; > if (!(machdep->flags & VMEMMAP_AWARE)) { > /* > @@ -1386,7 +1400,12 @@ ppc64_vmemmap_to_phys(ulong kvaddr, physaddr_t > *paddr, int verbose) > return FALSE; > } > - ms = machdep->machspec; > + /** > + * When vmemmap_list is not populated, kernel does the mapping in > init_mm > + * page table, so do a pagetable walk in kernel page table > + */ > + if (!ms->vmemmap_list) > + return ppc64_vtop_level4(kvaddr, (ulong > *)vt->kernel_pgd[0], paddr, verbose); > for (i = 0; i < ms->vmemmap_cnt; i++) { > if ((kvaddr >= ms->vmemmap_list[i].virt) && > -- > 2.41.0