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Message-ID: <fde425d3-699e-4e72-8823-2f50629468d0@arm.com>
Date: Thu, 6 Feb 2025 13:07:32 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Anshuman Khandual <anshuman.khandual@....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 06/02/2025 10:55, Anshuman Khandual wrote:
> 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.
Personally I find the "why" to be the most useful part of a commit log. I'd
prefer to leave it in unless any mm people complain.
>
>>
>> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
>> ---
>
> Regardless, LGTM.
>
> Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>
Thanks!
>
>> 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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