Messages in this thread | | | Date | Mon, 11 Sep 2023 12:13:09 -0500 | Subject | Re: kexec reboot failed due to commit 75d090fd167ac | From | Tom Lendacky <> |
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On 9/11/23 10:53, Kirill A. Shutemov wrote: > On Mon, Sep 11, 2023 at 10:33:01AM -0500, Tom Lendacky wrote: >> On 9/11/23 09:57, Kirill A. Shutemov wrote: >>> On Mon, Sep 11, 2023 at 10:56:36PM +0800, Dave Young wrote: >>>>> early console in extract_kernel >>>>> input_data: 0x000000807eb433a8 >>>>> input_len: 0x0000000000d26271 >>>>> output: 0x000000807b000000 >>>>> output_len: 0x0000000004800c10 >>>>> kernel_total_size: 0x0000000003e28000 >>>>> needed_size: 0x0000000004a00000 >>>>> trampoline_32bit: 0x000000000009d000 >>>>> >>>>> Decompressing Linux... out of pgt_buf in arch/x86/boot/compressed/ident_map_64.c!? >>>>> pages->pgt_buf_offset: 0x0000000000006000 >>>>> pages->pgt_buf_size: 0x0000000000006000 >>>>> >>>>> >>>>> Error: kernel_ident_mapping_init() failed >>>>> >>>>> It crashes on #PF due to stbl->nr_tables dereference in >>>>> efi_get_conf_table() called from init_unaccepted_memory(). >>>>> >>>>> I don't see anything special about stbl location: 0x775d6018. >>>>> >>>>> One other bit of information: disabling 5-level paging also helps the >>>>> issue. >>>>> >>>>> I will debug further. >>> >>> The problem is not limited to unaccepted memory, it also triggers if we >>> reach efi_get_rsdp_addr() in the same setup. >>> >>> I think we have several problems here. >>> >>> - 6 pages for !RANDOMIZE_BASE is only enough for kernel, cmdline, >>> boot_data and setup_data if we assume that they are in different 1G >>> regions and do not cross the 1G boundaries. 4-level paging: 1 for PGD, 1 >>> for PUD, 4 for PMD tables. >>> >>> Looks like we never map EFI/ACPI memory explicitly. >>> >>> It might work if kernel/cmdline/... are in single 1G and we have >>> spare pages to handle page faults. >>> >>> - No spare memory to handle mapping for cc_info and cc_info->cpuid_phys; >>> >>> - I didn't increase BOOT_INIT_PGT_SIZE when added 5-level paging support. >>> And if start pagetables from scratch ('else' case of 'if (p4d_offset...)) >>> we run out of memory. >>> >>> I believe similar logic would apply for BOOT_PGT_SIZE for RANDOMIZE_BASE=y >>> case. >>> >>> I don't know what the right fix here. We can increase the constants to be >>> enough to cover existing cases, but it is very fragile. I am not sure I >>> saw all users. Some of them could silently handled with pagefault handler >>> in some setups. And it is hard to catch new users during code review. >>> >>> Also I'm not sure why do we need pagefault handler there. Looks like it >>> just masking problems. I think everything has to be mapped explicitly. >>> >>> Any comments? >> >> There was a similar related issue around the cc_info blob that is captured >> here: https://lore.kernel.org/lkml/20230601072043.24439-1-ltao@redhat.com/ >> >> Personally, I'm a fan of mapping the EFI tables that will be passed to the >> kexec/kdump kernel. To me, that seems to more closely match the valid >> mappings for the tables when control is transferred to the OS from UEFI on >> the initial boot. > > I don't see how it would help if initialize_identity_maps() resets > pagetables. See 'else' case of 'if (p4d_offset...).
Ok, I see what you mean now.
Thanks, Tom
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