Question about Address Range Validation in Crash Kernel Allocation
Baoquan He
bhe at redhat.com
Thu Mar 21 18:16:15 PDT 2024
On 03/21/24 at 08:37pm, Li Huafei wrote:
>
>
> On 2024/3/21 18:06, Dave Young wrote:
> > Hi,
> >
> > On Thu, 21 Mar 2024 at 17:49, Li Huafei <lihuafei1 at huawei.com> wrote:
> >>
> >> Hi Baoquan，
> >>
> >> On 2024/3/21 17:17, chenhaixiang (A) wrote:
> >>>
> >>>>> I'm sorry for the delay. Here are some details from the boot log and
> >>>> /proc/iomem:
> >>>>> The Boot log:
> >>>>> [ 0.000000] Linux version 6.8.0 (root at localhost.localdomain) (gcc (GCC)
> >>>> 10.3.1, GNU ld (GNU Binutils) 2.37) #3 SMP PREEMPT_DYNAMIC Wed Mar 20
> >>>> 11:46:11 UTC 2024
> >>>>> [ 0.000000] Command line: BOOT_IMAGE=/vmlinuz-6.8.0
> >>>> root=/dev/mapper/root ro crashkernel=512M resume=/dev/mapper/swap
> >>>> rd.lvm.lv=root rd.lvm.lv=swap crash_kexec_post_notifiers softlockup_panic=1
> >>>> reserve_kbox_mem=16M fsck.mode=auto fsck.repair=yes panic=3
> >>>> nmi_watchdog=1 quiet rd.shell=0 memblock=debug efi=debug
> >>>> console=ttyS0,115200n8 console=tty0
> >>>> ......snip...
> >>>>> [ 0.022622] memblock_phys_alloc_range: 536870912 bytes align=0x1000000
> >>>> from=0x0000000000000000 max_addr=0x0000000100000000
> >>>> reserve_crashkernel_generic+0x7c/0x220
> >>>>> [ 0.022628] memblock_phys_alloc_range: 536870912 bytes align=0x1000000
> >>>> from=0x0000000100000000 max_addr=0x0000400000000000
> >>>> reserve_crashkernel_generic+0x7c/0x220
> >>>>> [ 0.022632] memblock_reserve: [0x000000c01f000000-0x000000c03effffff]
> >>>> memblock_alloc_range_nid+0xee/0x170
> >>>>> [ 0.022634] memblock_phys_alloc_range: 268435456 bytes align=0x1000000
> >>>> from=0x0000000000000000 max_addr=0x0000000100000000
> >>>> reserve_crashkernel_generic+0x11d/0x220
> >>>>> [ 0.022638] memblock_reserve: [0x0000000049000000-0x0000000058ffffff]
> >>>> memblock_alloc_range_nid+0xee/0x170
> >>>>> [ 0.022640] crashkernel low memory reserved: 0x49000000 - 0x59000000
> >>>> (256 MB)
> >>>>> [ 0.022641] crashkernel reserved: 0x000000c01f000000 -
> >>>> 0x000000c03f000000 (512 MB)
> >>>>
> >>>> Here, crashkernel,low is reserved in region: [0x49000000 - 0x59000000] (256
> >>>> MB)
> >>>> crashkernel,high is reserved in region: [0x000000c01f000000 -
> >>>> 0x000000c03f000000] (512 MB) ......
> >>>>> [ 0.029839] memblock_reserve: [0x000000c03ffff740-0x000000c03fffff7f]
> >>>> memblock_alloc_range_nid+0xee/0x170
> >>>>> [ 0.029843] e820: update [mem 0x53cbd000-0x53ccffff] usable ==>
> >>>> reserved
> >>>>> [ 0.029861] TSC deadline timer available
> >>>>
> >>>> Then here, region [0x53cbd000-0x53ccffff] is reserved in e820, and print abvoe
> >>>> "usable ==> reserved". This should be the step which prevents earlier reserved
> >>>> crashkernel,low from being added to iomem tree. I am not sure what triggered
> >>>> the e820 update.
> >>
> >> We added dump_stack () printing in efi_mem_reserve () and found that
> >> [0x53cbd000-0x53ccffff] was reserved by BGRT:
> >>
> >> [ 0.032259] e820: update [mem 0x53cbd000-0x53ccffff] usable ==>
> >> reserved
> >> [ 0.032262] CPU: 0 PID: 0 Comm: swapper Not tainted
> >> 5.10.0-60.18.0.50.h820.eulerosv2r11.x86_64 #7
> >> [ 0.032263] Hardware name: Huawei 2288H V5/BC11SPSCB0, BIOS 8.25
> >> 08/30/2022
> >> [ 0.032264] Call Trace:
> >> [ 0.032265] ? dump_stack+0x57/0x6e
> >> [ 0.032267] ? bgrt_init+0xc2/0xc2
> >> [ 0.032268] ? __e820__range_update+0x7a/0x1d6
> >> [ 0.032270] ? bgrt_init+0xc2/0xc2
> >> [ 0.032272] ? bgrt_init+0xc2/0xc2
> >> [ 0.032274] ? efi_arch_mem_reserve+0x1a3/0x1d0
> >> [ 0.032276] ? efi_mem_reserve+0x2d/0x42
> >> [ 0.032278] ? acpi_parse_bgrt+0xa/0x11
> >> [ 0.032279] ? acpi_table_parse+0x86/0xbc
> >> [ 0.032281] ? acpi_boot_init+0x79/0xad
> >> [ 0.032282] ? setup_arch+0x835/0x954
> >> [ 0.032284] ? start_kernel+0x5d/0x455
> >> [ 0.032286] ? secondary_startup_64_no_verify+0xc2/0xcb
> >>
> >> efi_reserve_boot_services() has reserved memory of type
> >> EFI_BOOT_SERVICES_CODE & EFI_BOOT_SERVICES_DATA before crashkernel.
> >> efi_bgrt_init() assumes that EFI_BOOT_SERVICES_DATA is not reserved by
> >> other modules. Then, the e820_table is directly updated, and the BGRT
> >> memory is reserved.
> >>
> >> However, memblock_is_region_reserved() in efi_reserve_boot_services()
> >> returns true when the ranges only overlap.
> >>
> >> already_reserved = memblock_is_region_reserved(start, size);
> >
> > Do you mean efi_reserve_boot_services is supposed to reserve the bgrt
> > memory but it does not reserve it due to the region overlapping with
> > some other reserved region? If so can you debug and find what exact
> > memblock reserved region overlaps with the bgrt?
>
> Yes. I added the following debug print to efi_reserve_boot_services():
>
> --- a/arch/x86/platform/efi/quirks.c
> +++ b/arch/x86/platform/efi/quirks.c
> @@ -339,6 +339,10 @@ void __init efi_reserve_boot_services(void)
>
> already_reserved = memblock_is_region_reserved(start, size);
>
> + pr_info("kdumpdebug: efi_reserve_boot_services start 0x%lu, "
> + "size 0x%lx, type 0x%lx, already_reserved %d\n",
> + start, size, md->type, already_reserved);
> +
> /*
> * Because the following memblock_reserve() is paired
> * with memblock_free_late() for this region in
>
It's great debugging and analysis, thanks you guys. Now there are
several questions:
1) why memory region [0x5976a018-0x5976abc7] is reserved by memblock
for efi_mem_attr_table. It's supposed to be outside of the
EFI_BOOT_SERVICES_DATA area? We may need check here if it's a bug.
[ 0.000000] random: crng init done
[ 0.000000] memblock_reserve: [0x000000005976a018-0x000000005976abc7] efi_memattr_init+0x51/0xa0
> This memory [0x0000005976a018-0x00000005976abc7] is reserved here, which belongs to EFI_BOOT_SERVICES_DATA.
> [ 0.000000] memblock_reserve: [0x000000005976a018-0x000000005976abc7] efi_memattr_init+0x51/0xa0
> It falls in the following range
> [ 0.000000] efi: mem22: [Boot Data | | | | | | | | | | |WB|WT|WC|UC] range=[0x0000000051329000-0x000000005cefefff] (187MB)
>
> in efi_reserve_boot_services(), [0x0000005132900-0x00000005cefeff] will not be fully reserved because [0x0000005976a018-0x0000005976abc7]
> has already been reserved and overlaps with [0x0000005976a018-0x0000005976abc7]
2) Because efi_mem_attr_table memblock reserved [0x5976a018-0x5976abc7],
the whole EFI_BOOT_SERVICES_DATA area [0x5132900-0x5cefeff] is not
memblock reserved for later free. Excep of the small area, do we need
still memblock reserve the remaining area, we may need check if this is
a bug.
>
> [ 0.021316] efi: kdumpdebug: efi_reserve_boot_services start 0x51329000, size 0xbbd6000, type 0x4, already_reserved 1
>
> It is not reserved by memblock, this free memory region is allocated by crashkernel
>
> [ 0.022597] crashkernel low memory reserved: 0x49000000 - 0x59000000 (256 MB)
> [ 0.022599] crashkernel reserved: 0x000000c01f000000 - 0x000000c03f000000 (512 MB)
>
> In efi_bgrt_init (), it is assumed that the memory of the EFI_BOOT_SERVICES_DATA type has been successfully
> reserved. Therefore, the address in the range is directly used. As a result, the memory overlaps with
> the crashkernel region.
(3) efi_bgrt_init() should be innocent because it's supposed to safely
use the area according to the existing efi quirk handling.
(4) the deferring of adding crashh_low_res to iomem exposed the above
efi issue. When we cancel the deferring of crashh_res inserting into
iomem, we can see that the brgt area is reserved inside crashkernel
region, that's problematic.
2d4fd058-60efefff : System RAM
2d4fd058-58ffffff : System RAM
49000000-58ffffff : Crash kernel
53cbd000-53ccffff : Reserved <---
60eff000-704fefff : Reserved
--
93dd424000-93dd9fffff : Kernel bss
c01f000000-c03effffff : Crash kernel
d0000000000-d0fffffffff : PCI Bus 0000:00
d0000000000-d00001fffff : PCI Bus 0000:01
>
> [ 0.029694] e820: update [mem 0x53cbd000-0x53ccffff] usable ==> reserved
> >
> > BTW, the previous email threads are weird, and not threading
> > correctly, hard to find information.
>
> It should be because the log content is too large and has been put on hold. In my previous email, I received a prompt:
>
> The reason it is being held:
>
> Message body is too big: 248998 bytes with a limit of 40 KB
>
>
> >
> >>
> >> /*
> >> * Because the following memblock_reserve() is paired
> >> * with memblock_free_late() for this region in
> >> * efi_free_boot_services(), we must be extremely
> >> * careful not to reserve, and subsequently free,
> >> * critical regions of memory (like the kernel image) or
> >> * those regions that somebody else has already
> >> * reserved.
> >> *
> >> * A good example of a critical region that must not be
> >> * freed is page zero (first 4Kb of memory), which may
> >> * contain boot services code/data but is marked
> >> * E820_TYPE_RESERVED by trim_bios_range().
> >> */
> >> if (!already_reserved) {
> >> memblock_reserve(start, size);
> >>
> >> /*
> >> * If we are the first to reserve the region, no
> >> * one else cares about it. We own it and can
> >> * free it later.
> >> */
> >> if (can_free_region(start, size))
> >> continue;
> >> }
> >>
> >> As a result, some memory of EFI_BOOT_SERVICES_DATA is not reserved in
> >> advance. The subsequent crashkernel happens to reserve this portion of
> >> memory, which conflicts with BGRT.
> >>
> >>> Current analysis suggests that efi_reserve_boot_services() is causing the update of the e820 table.
> >>>
> >>>>
> >>>> How do you boot into your new 6.8.0 kernel? Used kexec -l to jump into the 2nd
> >>>> kernel, or reboot from bios/firmware boot up into 6.8.0?
> >>> It's reboot from bios boot up into 6.8.0. I attempted to revert the below patch,
> >>> and this time the conflicting segment "53cbd000-53ccffff" also appeared in the /proc/iomem
> >>> of the 6.8 kernel.
> >>>
> >>> 2d4fd058-60efefff : System RAM
> >>> 2d4fd058-58ffffff : System RAM
> >>> 49000000-58ffffff : Crash kernel
> >>> 53cbd000-53ccffff : Reserved
> >>> 60eff000-704fefff : Reserved
> >>> --
> >>> 93dd424000-93dd9fffff : Kernel bss
> >>> c01f000000-c03effffff : Crash kernel
> >>> d0000000000-d0fffffffff : PCI Bus 0000:00
> >>> d0000000000-d00001fffff : PCI Bus 0000:01
> >>>>
> >>>> Reverting below commit should fix your problem, can you try it?
> >>>>
> >>>> commit 4a693ce65b186fddc1a73621bd6f941e6e3eca21
> >>>> Author: Huacai Chen <chenhuacai at kernel.org>
> >>>> Date: Fri Dec 29 16:02:13 2023 +0800
> >>>>
> >>>> kdump: defer the insertion of crashkernel resources
> >>>
> >>> .
> >>>
> >>
> >> _______________________________________________
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> >> http://lists.infradead.org/mailman/listinfo/kexec
> >
> > .
> >
>
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