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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 9A67F100004 X-Stat-Signature: k9jpprtrdap8m9nc8d7g9iks7rarqzy5 X-HE-Tag: 1751278225-164312 X-HE-Meta: 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 iKQxzrPQ mpisaUV0M8NkHYkmpIKwC6fXI47tIh/BAxaQLab2rLq2tHzOGfUJKkdmNbxsClK9YXjf2laNxWtKoN3cQboOLDYARHju1+PiGqPT9Q+Y3edzqgyQLoH1/CMzlCmZD2pM5m2/AWGUwghk0+Ou2H5azOj0DUdnBEun7PKf6rO7FMskjHr2kIWi1jZ11SQ71ZoobPdXZB52UN/JDDUhoupWoTWrya2yEuVOh502PEnPRYb5JmiNGxGygljY1wTaeVHvffnRwuLymr2ytVi/8yY2M38vIN4NviRv55J7h X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 28/06/2025 12:34, Dev Jain wrote: > Batch ptep_modify_prot_start/commit in preparation for optimizing mprotect. > Architecture can override these helpers; in case not, they are implemented > as a simple loop over the corresponding single pte helpers. > > Signed-off-by: Dev Jain > --- > include/linux/pgtable.h | 83 ++++++++++++++++++++++++++++++++++++++++- > mm/mprotect.c | 4 +- > 2 files changed, 84 insertions(+), 3 deletions(-) > > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h > index cf1515c163e2..662f39e7475a 100644 > --- a/include/linux/pgtable.h > +++ b/include/linux/pgtable.h > @@ -1331,7 +1331,8 @@ static inline pte_t ptep_modify_prot_start(struct vm_area_struct *vma, > > /* > * Commit an update to a pte, leaving any hardware-controlled bits in > - * the PTE unmodified. > + * the PTE unmodified. The pte may have been "upgraded" w.r.t a/d bits compared > + * to the old_pte, as in, it may have a/d bits on which were off in old_pte. I find this last sentance a bit confusing. I think what you are trying to say is somehthing like: """ old_pte is the value returned from ptep_modify_prot_start() but may additionally have have young and/or dirty bits set where previously they were not. """ ? > */ > static inline void ptep_modify_prot_commit(struct vm_area_struct *vma, > unsigned long addr, > @@ -1340,6 +1341,86 @@ static inline void ptep_modify_prot_commit(struct vm_area_struct *vma, > __ptep_modify_prot_commit(vma, addr, ptep, pte); > } > #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */ > + > +/** > + * modify_prot_start_ptes - Start a pte protection read-modify-write transaction > + * over a batch of ptes, which protects against asynchronous hardware > + * modifications to the ptes. The intention is not to prevent the hardware from > + * making pte updates, but to prevent any updates it may make from being lost. > + * Please see the comment above ptep_modify_prot_start() for full description. > + * > + * @vma: The virtual memory area the pages are mapped into. > + * @addr: Address the first page is mapped at. > + * @ptep: Page table pointer for the first entry. > + * @nr: Number of entries. > + * > + * May be overridden by the architecture; otherwise, implemented as a simple > + * loop over ptep_modify_prot_start(), collecting the a/d bits from each pte > + * in the batch. > + * > + * Note that PTE bits in the PTE batch besides the PFN can differ. > + * > + * Context: The caller holds the page table lock. The PTEs map consecutive > + * pages that belong to the same folio. The PTEs are all in the same PMD. > + * Since the batch is determined from folio_pte_batch, the PTEs must differ > + * only in a/d bits (and the soft dirty bit; see fpb_t flags in > + * mprotect_folio_pte_batch()). This last sentence is confusing... You had previous said the PFN can differ, but here you imply on a, d and sd bits are allowed to differ. > + */ > +#ifndef modify_prot_start_ptes > +static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma, > + unsigned long addr, pte_t *ptep, unsigned int nr) > +{ > + pte_t pte, tmp_pte; > + > + pte = ptep_modify_prot_start(vma, addr, ptep); > + while (--nr) { > + ptep++; > + addr += PAGE_SIZE; > + tmp_pte = ptep_modify_prot_start(vma, addr, ptep); > + if (pte_dirty(tmp_pte)) > + pte = pte_mkdirty(pte); > + if (pte_young(tmp_pte)) > + pte = pte_mkyoung(pte); > + } > + return pte; > +} > +#endif > + > +/** > + * modify_prot_commit_ptes - Commit an update to a batch of ptes, leaving any > + * hardware-controlled bits in the PTE unmodified. > + * > + * @vma: The virtual memory area the pages are mapped into. > + * @addr: Address the first page is mapped at. > + * @ptep: Page table pointer for the first entry. > + * @old_pte: Old page table entry (for the first entry) which is now cleared. > + * @pte: New page table entry to be set. > + * @nr: Number of entries. > + * > + * May be overridden by the architecture; otherwise, implemented as a simple > + * loop over ptep_modify_prot_commit(). > + * > + * Context: The caller holds the page table lock. The PTEs are all in the same > + * PMD. On exit, the set ptes in the batch map the same folio. The pte may have > + * been "upgraded" w.r.t a/d bits compared to the old_pte, as in, it may have > + * a/d bits on which were off in old_pte. Same comment as for ptep_modify_prot_start(). > + */ > +#ifndef modify_prot_commit_ptes > +static inline void modify_prot_commit_ptes(struct vm_area_struct *vma, unsigned long addr, > + pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr) > +{ > + int i; > + > + for (i = 0; i < nr; ++i) { > + ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte); > + ptep++; > + addr += PAGE_SIZE; > + old_pte = pte_next_pfn(old_pte); > + pte = pte_next_pfn(pte); > + } > +} > +#endif > + > #endif /* CONFIG_MMU */ > > /* > diff --git a/mm/mprotect.c b/mm/mprotect.c > index af10a7fbe6b8..627b0d67cc4a 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -206,7 +206,7 @@ static long change_pte_range(struct mmu_gather *tlb, > continue; > } > > - oldpte = ptep_modify_prot_start(vma, addr, pte); > + oldpte = modify_prot_start_ptes(vma, addr, pte, nr_ptes); You're calling this with nr_ptes = 0 for the prot_numa case. But the implementation expects minimum nr_ptes == 1. > ptent = pte_modify(oldpte, newprot); > > if (uffd_wp) > @@ -232,7 +232,7 @@ static long change_pte_range(struct mmu_gather *tlb, > can_change_pte_writable(vma, addr, ptent)) > ptent = pte_mkwrite(ptent, vma); > > - ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent); > + modify_prot_commit_ptes(vma, addr, pte, oldpte, ptent, nr_ptes); > if (pte_needs_flush(oldpte, ptent)) > tlb_flush_pte_range(tlb, addr, PAGE_SIZE); > pages++;