Re: [PATCH v4] KHO: Fix boot failure due to kmemleak access to non-PRESENT pages

[Pratyush Yadav <pratyush@kernel.org>]

On Thu, Nov 27 2025, ranxiaokai627@163.com wrote:

> From: Ran Xiaokai <ran.xiaokai@zte.com.cn>
>
> When booting with debug_pagealloc=on while having:
> CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT=y
> CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=n
> the system fails to boot due to page faults during kmemleak scanning.
>
> This occurs because:
> With debug_pagealloc is enabled, __free_pages() invokes
> debug_pagealloc_unmap_pages(), clearing the _PAGE_PRESENT bit for
> freed pages in the kernel page table.
> KHO scratch areas are allocated from memblock and noted by kmemleak. But
> these areas don't remain reserved but released later to the page allocator
> using init_cma_reserved_pageblock(). This causes subsequent kmemleak scans
> access non-PRESENT pages, leading to fatal page faults.
>
> Mark scratch areas with kmemleak_ignore_phys() after they are allocated
> from memblock to exclude them from kmemleak scanning before they are
> released to buddy allocator to fix this.
>
> Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers")
> Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

Reviewed-by: Pratyush Yadav <pratyush@kernel.org>

Thanks!

[...]

-- 
Regards,
Pratyush Yadav