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SubjectRe: [PATCH 1/3] arm64: hugetlb: Fix huge_pte_offset to return poisoned page table entries
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On 4/12/2017 8:04 AM, Punit Agrawal wrote:
> When memory failure is enabled, a poisoned hugepage pte is marked as a
> swap entry. huge_pte_offset() does not return the poisoned page table
> entries when it encounters PUD/PMD hugepages.
>
> This behaviour of huge_pte_offset() leads to error such as below when
> munmap is called on poisoned hugepages.
>
> [ 344.165544] mm/pgtable-generic.c:33: bad pmd 000000083af00074.
>
> Fix huge_pte_offset() to return the poisoned pte which is then
> appropriately handled by the generic layer code.
>
> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Steve Capper <steve.capper@arm.com>
> Cc: David Woods <dwoods@mellanox.com>
Tested-by: Tyler Baicar <tbaicar@codeaurora.org>

Thanks,
Tyler
> ---
> arch/arm64/mm/hugetlbpage.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index 7514a000e361..5f1832165d69 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -143,15 +143,24 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
> pr_debug("%s: addr:0x%lx pgd:%p\n", __func__, addr, pgd);
> if (!pgd_present(*pgd))
> return NULL;
> - pud = pud_offset(pgd, addr);
> - if (!pud_present(*pud))
> - return NULL;
>
> - if (pud_huge(*pud))
> + pud = pud_offset(pgd, addr);
> + /*
> + * In case of HW Poisoning, a hugepage pud/pmd can contain
> + * poisoned entries. Poisoned entries are marked as swap
> + * entries.
> + *
> + * For puds/pmds that are not present, check to see if it
> + * could be a swap entry (!present and !none).
> + */
> + if ((!pte_present(pud_pte(*pud)) && !pud_none(*pud)) || pud_huge(*pud))
> return (pte_t *)pud;
> +
> pmd = pmd_offset(pud, addr);
> - if (!pmd_present(*pmd))
> + if (pmd_none(*pmd))
> return NULL;
> + if (!pmd_present(*pmd) && !pmd_none(*pmd))
> + return (pte_t *)pmd;
>
> if (pte_cont(pmd_pte(*pmd))) {
> pmd = pmd_offset(
> @@ -160,6 +169,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
> }
> if (pmd_huge(*pmd))
> return (pte_t *)pmd;
> +
> pte = pte_offset_kernel(pmd, addr);
> if (pte_present(*pte) && pte_cont(*pte)) {
> pte = pte_offset_kernel(

--
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Qualcomm Technologies, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.

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