Question about Address Range Validation in Crash Kernel Allocation
Dave Young
dyoung at redhat.com
Fri Mar 22 00:26:21 PDT 2024
Hi,
On Fri, 22 Mar 2024 at 09:16, Baoquan He <bhe at redhat.com> wrote:
>
> 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.
The mem_attr_table memory falls into a EFI Boot Service Data region
[ 0.000000] efi: mem22: [Boot Data | | | | | | | | | |
|WB|WT|WC|UC] range=[0x0000000051329000-0x000000005cefefff] (187MB)
>
> [ 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.
I think the whole EFI Boot Data region should be reserved temperately
by efi_reserve_boot_services, but if they should be reserved partially
as multiple smaller regions I'm not sure, I added Ard and EFI list in
another reply, let's see how EFI people think.
>
> >
> > [ 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.
Agreed
>
>
> (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
> > >>>
> > >>> .
> > >>>
> > >>
> > >> _______________________________________________
> > >> kexec mailing list
> > >> kexec at lists.infradead.org
> > >> http://lists.infradead.org/mailman/listinfo/kexec
> > >
> > > .
> > >
> >
>
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