Re: [PATCH v2] x86: remove the BIOS memory corruption check feature

[Luiz Capitulino <luizcap@redhat.com>]

On 10/9/26 4:16 PM, Luiz Capitulino wrote:
> 
> 
> On 10/9/26 2:06 PM, Thorsten Blum wrote:
>> On Mon, Jul 20, 2026 at 04:41:05PM -0400, Luiz Capitulino wrote:
>>> By default, the BIOS memory corruption check works by reserving the
>>> first 64 KiB physical area from memblock, zeroing it and then scanning it
>>> periodically.
>>>
>>> However, this functionality has been broken since v5.13 by two commits:
>>>
>>> - Commit a799c2bd29d1 ("x86/setup: Consolidate early memory reservations").
>>>    Moved trim_low_memory_range() into early_reserve_memory(), which runs
>>>    earlier in setup_arch(), causing the first 64 KiB to be reserved (when
>>>    CONFIG_X86_RESERVE_LOW=64) before setup_bios_corruption_check() runs
>>>
>>> - Commit f1d4d47c5851 ("x86/setup: Always reserve the first 1M of RAM").
>>>    Hardcodes the reservation of the first 64 KiB early in
>>>    early_reserve_memory()
>>>
>>> It might be possible to get this feature to work by allowing
>>> setup_bios_corruption_check() to run first, but it's just not worth it
>>> given that the kernel will never access this memory area anyways.
>>>
>>> Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
>>> ---
>>>
>>> Changelog
>>> =========
>>>
>>> v2
>>> - Rebase against latest Linus tree (v7.2-rc4)
>>> - Improve changelog
>>>
>>>   .../admin-guide/kernel-parameters.txt         |  23 ---
>>>   arch/x86/Kconfig                              |  30 ---
>>>   arch/x86/configs/i386_defconfig               |   1 -
>>>   arch/x86/configs/x86_64_defconfig             |   1 -
>>>   arch/x86/include/asm/bios_ebda.h              |  17 --
>>>   arch/x86/include/asm/setup.h                  |   1 -
>>>   arch/x86/kernel/Makefile                      |   2 -
>>>   arch/x86/kernel/check.c                       | 187 ------------------
>>>   arch/x86/kernel/setup.c                       |   4 -
>>>   9 files changed, 266 deletions(-)
>>>   delete mode 100644 arch/x86/kernel/check.c
>>
>> Hi Luiz,
> 
> Hey,
> 
>> v2 no longer applies to mainline - are you planning to rebase it for v3?
> 
> If we plan to merge it, I can :)
> 
>> Regarding the changelog: did you consider that the check is only broken
>> for the default size? Booting with
>>
>>    memory_corruption_check=1 memory_corruption_check_size=256K
>>
>> still works and I get:
>>
>>    check: Scanning 1 areas for low memory corruption
>>    check: Scanning for low memory corruption every 60 seconds
> 
> Yes, but IIRC this won't reserve the first 64K and my understanding
> is that checking the first 64K was the main point of the feature.

I've just sent v3. I improved the changelog based on your feedback.

Also, I realized that v2 doesn't apply because it was mangled by my MUA.
I sent v3 with git-send-email so it should apply now.