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Message-ID: <d86b6d7f-0ab3-4737-85cd-70cddcffc1e8@arm.com>
Date: Thu, 6 Feb 2025 16:25:04 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Ryan Roberts <ryan.roberts@....com>,
Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
Muchun Song <muchun.song@...ux.dev>,
Pasha Tatashin <pasha.tatashin@...een.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Uladzislau Rezki <urezki@...il.com>, Christoph Hellwig <hch@...radead.org>,
Mark Rutland <mark.rutland@....com>, Ard Biesheuvel <ardb@...nel.org>,
Dev Jain <dev.jain@....com>, Alexandre Ghiti <alexghiti@...osinc.com>,
Steve Capper <steve.capper@...aro.org>, Kevin Brodsky <kevin.brodsky@....com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 05/16] mm/page_table_check: Batch-check pmds/puds just
like ptes
On 2/5/25 20:39, Ryan Roberts wrote:
> Convert page_table_check_p[mu]d_set(...) to
> page_table_check_p[mu]ds_set(..., nr) to allow checking a contiguous set
> of pmds/puds in single batch. We retain page_table_check_p[mu]d_set(...)
> as macros that call new batch functions with nr=1 for compatibility.
>
> arm64 is about to reorganise its pte/pmd/pud helpers to reuse more code
> and to allow the implementation for huge_pte to more efficiently set
> ptes/pmds/puds in batches. We need these batch-helpers to make the
> refactoring possible.
A very small nit.
Although this justification here is reasonable enough but not sure if
platform specific requirements, need to be spelled out in such detail
for a generic MM change.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
Regardless, LGTM.
Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>
> include/linux/page_table_check.h | 30 +++++++++++++++++-----------
> mm/page_table_check.c | 34 +++++++++++++++++++-------------
> 2 files changed, 38 insertions(+), 26 deletions(-)
>
> diff --git a/include/linux/page_table_check.h b/include/linux/page_table_check.h
> index 6722941c7cb8..289620d4aad3 100644
> --- a/include/linux/page_table_check.h
> +++ b/include/linux/page_table_check.h
> @@ -19,8 +19,10 @@ void __page_table_check_pmd_clear(struct mm_struct *mm, pmd_t pmd);
> void __page_table_check_pud_clear(struct mm_struct *mm, pud_t pud);
> void __page_table_check_ptes_set(struct mm_struct *mm, pte_t *ptep, pte_t pte,
> unsigned int nr);
> -void __page_table_check_pmd_set(struct mm_struct *mm, pmd_t *pmdp, pmd_t pmd);
> -void __page_table_check_pud_set(struct mm_struct *mm, pud_t *pudp, pud_t pud);
> +void __page_table_check_pmds_set(struct mm_struct *mm, pmd_t *pmdp, pmd_t pmd,
> + unsigned int nr);
> +void __page_table_check_puds_set(struct mm_struct *mm, pud_t *pudp, pud_t pud,
> + unsigned int nr);
> void __page_table_check_pte_clear_range(struct mm_struct *mm,
> unsigned long addr,
> pmd_t pmd);
> @@ -74,22 +76,22 @@ static inline void page_table_check_ptes_set(struct mm_struct *mm,
> __page_table_check_ptes_set(mm, ptep, pte, nr);
> }
>
> -static inline void page_table_check_pmd_set(struct mm_struct *mm, pmd_t *pmdp,
> - pmd_t pmd)
> +static inline void page_table_check_pmds_set(struct mm_struct *mm,
> + pmd_t *pmdp, pmd_t pmd, unsigned int nr)
> {
> if (static_branch_likely(&page_table_check_disabled))
> return;
>
> - __page_table_check_pmd_set(mm, pmdp, pmd);
> + __page_table_check_pmds_set(mm, pmdp, pmd, nr);
> }
>
> -static inline void page_table_check_pud_set(struct mm_struct *mm, pud_t *pudp,
> - pud_t pud)
> +static inline void page_table_check_puds_set(struct mm_struct *mm,
> + pud_t *pudp, pud_t pud, unsigned int nr)
> {
> if (static_branch_likely(&page_table_check_disabled))
> return;
>
> - __page_table_check_pud_set(mm, pudp, pud);
> + __page_table_check_puds_set(mm, pudp, pud, nr);
> }
>
> static inline void page_table_check_pte_clear_range(struct mm_struct *mm,
> @@ -129,13 +131,13 @@ static inline void page_table_check_ptes_set(struct mm_struct *mm,
> {
> }
>
> -static inline void page_table_check_pmd_set(struct mm_struct *mm, pmd_t *pmdp,
> - pmd_t pmd)
> +static inline void page_table_check_pmds_set(struct mm_struct *mm,
> + pmd_t *pmdp, pmd_t pmd, unsigned int nr)
> {
> }
>
> -static inline void page_table_check_pud_set(struct mm_struct *mm, pud_t *pudp,
> - pud_t pud)
> +static inline void page_table_check_puds_set(struct mm_struct *mm,
> + pud_t *pudp, pud_t pud, unsigned int nr)
> {
> }
>
> @@ -146,4 +148,8 @@ static inline void page_table_check_pte_clear_range(struct mm_struct *mm,
> }
>
> #endif /* CONFIG_PAGE_TABLE_CHECK */
> +
> +#define page_table_check_pmd_set(mm, pmdp, pmd) page_table_check_pmds_set(mm, pmdp, pmd, 1)
> +#define page_table_check_pud_set(mm, pudp, pud) page_table_check_puds_set(mm, pudp, pud, 1)
> +
> #endif /* __LINUX_PAGE_TABLE_CHECK_H */
> diff --git a/mm/page_table_check.c b/mm/page_table_check.c
> index 509c6ef8de40..dae4a7d776b3 100644
> --- a/mm/page_table_check.c
> +++ b/mm/page_table_check.c
> @@ -234,33 +234,39 @@ static inline void page_table_check_pmd_flags(pmd_t pmd)
> WARN_ON_ONCE(swap_cached_writable(pmd_to_swp_entry(pmd)));
> }
>
> -void __page_table_check_pmd_set(struct mm_struct *mm, pmd_t *pmdp, pmd_t pmd)
> +void __page_table_check_pmds_set(struct mm_struct *mm, pmd_t *pmdp, pmd_t pmd,
> + unsigned int nr)
> {
> + unsigned int i;
> + unsigned long stride = PMD_SIZE >> PAGE_SHIFT;
> +
> if (&init_mm == mm)
> return;
>
> page_table_check_pmd_flags(pmd);
>
> - __page_table_check_pmd_clear(mm, *pmdp);
> - if (pmd_user_accessible_page(pmd)) {
> - page_table_check_set(pmd_pfn(pmd), PMD_SIZE >> PAGE_SHIFT,
> - pmd_write(pmd));
> - }
> + for (i = 0; i < nr; i++)
> + __page_table_check_pmd_clear(mm, *(pmdp + i));
> + if (pmd_user_accessible_page(pmd))
> + page_table_check_set(pmd_pfn(pmd), stride * nr, pmd_write(pmd));
> }
> -EXPORT_SYMBOL(__page_table_check_pmd_set);
> +EXPORT_SYMBOL(__page_table_check_pmds_set);
>
> -void __page_table_check_pud_set(struct mm_struct *mm, pud_t *pudp, pud_t pud)
> +void __page_table_check_puds_set(struct mm_struct *mm, pud_t *pudp, pud_t pud,
> + unsigned int nr)
> {
> + unsigned int i;
> + unsigned long stride = PUD_SIZE >> PAGE_SHIFT;
> +
> if (&init_mm == mm)
> return;
>
> - __page_table_check_pud_clear(mm, *pudp);
> - if (pud_user_accessible_page(pud)) {
> - page_table_check_set(pud_pfn(pud), PUD_SIZE >> PAGE_SHIFT,
> - pud_write(pud));
> - }
> + for (i = 0; i < nr; i++)
> + __page_table_check_pud_clear(mm, *(pudp + i));
> + if (pud_user_accessible_page(pud))
> + page_table_check_set(pud_pfn(pud), stride * nr, pud_write(pud));
> }
> -EXPORT_SYMBOL(__page_table_check_pud_set);
> +EXPORT_SYMBOL(__page_table_check_puds_set);
>
> void __page_table_check_pte_clear_range(struct mm_struct *mm,
> unsigned long addr,
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