On 14/03/25 7:57 pm, Yeo Reum Yun wrote:

Hi Dev,

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Since pxd_clear_bad() is an operation changing the state of the page tables, we should call arch_sync_kernel_mappings() post this.

Fixes: e80d3909be42 ("mm: track page table modifications in __apply_to_page_range()") Cc: stable@vger.kernel.org Signed-off-by: Dev Jain dev.jain@arm.com

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mm/memory.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/mm/memory.c b/mm/memory.c index 78c7ee62795e..9a4a8c710be0 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2987,6 +2987,7 @@ static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud, if (!create) continue; pmd_clear_bad(pmd);

•                 *mask = PGTBL_PMD_MODIFIED;
  

Oh well, I guess these should have been *mask |= PGTBL_PMD_MODIFIED.

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           }
           err = apply_to_pte_range(mm, pmd, addr, next,
                                    fn, data, create, mask);

@@ -3023,6 +3024,7 @@ static int apply_to_pud_range(struct mm_struct *mm, p4d_t *p4d, if (!create) continue; pud_clear_bad(pud);

•                 *mask = PGTBL_PUD_MODIFIED;
           }
           err = apply_to_pmd_range(mm, pud, addr, next,
                                    fn, data, create, mask);
  

@@ -3059,6 +3061,7 @@ static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd, if (!create) continue; p4d_clear_bad(p4d);

•                 *mask = PGTBL_P4D_MODIFIED;
           }
           err = apply_to_pud_range(mm, p4d, addr, next,
                                    fn, data, create, mask);
  

@@ -3095,6 +3098,7 @@ static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr, if (!create) continue; pgd_clear_bad(pgd);

•                 mask = PGTBL_PGD_MODIFIED;
  

...

           }
           err = apply_to_p4d_range(mm, pgd, addr, next,
                                    fn, data, create, &mask);

I don't think this wouldn't need. the pXd_clear_bad() is only called at creation of each level of page table, and when it clear, the following, apply_to_pXd_range() function would be set the make properly via pXd_alloc() and apply_to_pte_range().

Makes sense. But pxd_clear_bad() gets called in case of !pxd_none(), so while creating, why would the page containing the page table not be none? I believe it should be cleared already?

Thanks.