Messages in this thread |  | | From | "Huang, Ying" <> | | Subject | Re: [v2 PATCH] arm64: mm: Fix kexec failure after pte_mkwrite_novma() change | | Date | Tue, 02 Dec 2025 13:42:17 +0800 |
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Jianpeng Chang <jianpeng.chang.cn@windriver.com> writes:
> Commit 143937ca51cc ("arm64, mm: avoid always making PTE dirty in > pte_mkwrite()") modified pte_mkwrite_novma() to only clear PTE_RDONLY > when the page is already dirty (PTE_DIRTY is set). While this optimization > prevents unnecessary dirty page marking in normal memory management paths, > it breaks kexec on some platforms like NXP LS1043. > > The issue occurs in the kexec code path: > 1. machine_kexec_post_load() calls trans_pgd_create_copy() to create a > writable copy of the linear mapping > 2. _copy_pte() calls pte_mkwrite_novma() to ensure all pages in the copy > are writable for the new kernel image copying > 3. With the new logic, clean pages (without PTE_DIRTY) remain read-only > 4. When kexec tries to copy the new kernel image through the linear > mapping, it fails on read-only pages, causing the system to hang > after "Bye!" > > The same issue affects hibernation which uses the same trans_pgd code path. > > Fix this by explicitly clearing PTE_RDONLY in _copy_pte() for both > kexec and hibernation, ensuring all pages in the temporary mapping are > writable regardless of their dirty state. This preserves the original > commit's optimization for normal memory management while fixing the > kexec/hibernation regression. > > Fixes: 143937ca51cc ("arm64, mm: avoid always making PTE dirty in pte_mkwrite()") > Signed-off-by: Jianpeng Chang <jianpeng.chang.cn@windriver.com>
LGTM, Thanks! Feel free to add my
Reviewed-by: Huang Ying <ying.huang@linux.alibaba.com>
in the future versions.
> --- > v2: > - Use pte_mkwrite_novma(pte_mkdirty(pte)) instead of manual bit manipulation > - Updated comments to clarify pte_mkwrite_novma() alone cannot be used > v1: https://lore.kernel.org/all/20251127034350.3600454-1-jianpeng.chang.cn@windriver.com/ > > arch/arm64/mm/trans_pgd.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c > index 18543b603c77..08f5ee6643e1 100644 > --- a/arch/arm64/mm/trans_pgd.c > +++ b/arch/arm64/mm/trans_pgd.c > @@ -40,8 +40,13 @@ static void _copy_pte(pte_t *dst_ptep, pte_t *src_ptep, unsigned long addr) > * Resume will overwrite areas that may be marked > * read only (code, rodata). Clear the RDONLY bit from > * the temporary mappings we use during restore. > + * > + * For kexec/hibernation, we need writable access to all > + * pages in the linear mapping to copy the new kernel image. > + * Mark pages dirty first to ensure pte_mkwrite_novma() > + * clears PTE_RDONLY. > */ > - __set_pte(dst_ptep, pte_mkwrite_novma(pte)); > + __set_pte(dst_ptep, pte_mkwrite_novma(pte_mkdirty(pte))); > } else if (!pte_none(pte)) { > /* > * debug_pagealloc will removed the PTE_VALID bit if > @@ -57,7 +62,7 @@ static void _copy_pte(pte_t *dst_ptep, pte_t *src_ptep, unsigned long addr) > */ > BUG_ON(!pfn_valid(pte_pfn(pte))); > > - __set_pte(dst_ptep, pte_mkvalid(pte_mkwrite_novma(pte))); > + __set_pte(dst_ptep, pte_mkvalid(pte_mkwrite_novma(pte_mkdirty(pte)))); > } > }
--- Best Regards, Huang, Ying
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