Hello lijiang, On Mon, Sep 18, 2023 at 07:34:04PM +0800, lijiang wrote: > Hi, Aditya > Thank you for the patch. > > On Mon, Sep 11, 2023 at 8:00 PM <crash-utility-request@xxxxxxxxxx> wrote: > > > ... > > > > Currently 'crash-tool' fails on vmcore collected on upstream kernel on > > PowerPC64 with the error: > > > > crash: invalid kernel virtual address: 0 type: "first list entry > > > > Presently the address translation for vmemmap addresses is done using > > the vmemmap_list. But with the below commit in Linux, vmemmap_list can > > be empty, in case of Radix MMU on PowerPC64 > > > > 368a0590d954: (powerpc/book3s64/vmemmap: switch radix to use a > > different vmemmap handling function) > > > > In case vmemmap_list is empty, then it's head is NULL, which crash tries > > to access and fails due to accessing NULL. > > > > Instead of depending on 'vmemmap_list' for address translation for > > vmemmap addresses, do a kernel pagetable walk to get the physical > > address associated with given virtual address > > > > Reviewed-by: Hari Bathini <hbathini@xxxxxxxxxxxxx> > > Signed-off-by: Aditya Gupta <adityag@xxxxxxxxxxxxx> > > > > --- > > > > Testing > > ======= > > > > Git tree with patch applied: > > https://github.com/adi-g15-ibm/crash/tree/bugzilla-203296-list-v1 > > > > This can be tested with '/proc/vmcore' as the vmcore, since makedumpfile > > > > 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 Thanks for testing it. This issue occurs only in case of Radix MMU. Overall, these are all the requirements: 1. Upstream linux (master branch) (your commit will also work, ce9ecca0238b) 2. 'CONFIG_PPC_BOOK3S_64' should be 'y' in kernel config (this should be there in default configs) 3. Check in dmesg of the crashed kernel, if it prints 'hash-mmu' or 'radix-mmu'. It should be 'radix-mmu'. I guess, the system that was crashed might be using 'hash-mmu'. > also fails in absence of 'vmemmap_list' in upstream linux Yes, it will fail in Hash MMU case, as we depend on 'vmemmap_list' in that case, as the virtual to physical address mapping is not available in page table, in case of Hash-MMU. Only in radix MMU case, it will still work, even if 'vmemmap_list' is removed, since we have the mappings in kernel page table, which is used by this patch. Let me know if the issue still doesn't reproduce even after using a system with Radix MMU. Thanks, - Aditya Gupta -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/crash-utility Contribution Guidelines: https://github.com/crash-utility/crash/wiki
