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imf03.hostedemail.com; dkim=none; spf=pass (imf03.hostedemail.com: domain of dev.jain@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=dev.jain@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1751110521; a=rsa-sha256; cv=none; b=dUDLY2VzKtJ5Rs6fOop4WoN1dWqhUlX4po0DBKnVZd7+X8L8vh5YkFuPpTjSI6dunwhIk/ 4CaEKELIUbTUqVSSw365S1V1UXBHh6DuFAzzKVlUnQeI2wdiJDvEwHOALTn3Oq9kWJf3Dz Z4+lCLJbc3Q6S7huAbxmKfixgsNnafY= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 47E391BD0; Sat, 28 Jun 2025 04:35:03 -0700 (PDT) Received: from MacBook-Pro.blr.arm.com (MacBook-Pro.blr.arm.com [10.164.18.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 6A4413F762; Sat, 28 Jun 2025 04:35:12 -0700 (PDT) From: Dev Jain To: akpm@linux-foundation.org Cc: ryan.roberts@arm.com, david@redhat.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, anshuman.khandual@arm.com, peterx@redhat.com, joey.gouly@arm.com, ioworker0@gmail.com, baohua@kernel.org, kevin.brodsky@arm.com, quic_zhenhuah@quicinc.com, christophe.leroy@csgroup.eu, yangyicong@hisilicon.com, linux-arm-kernel@lists.infradead.org, hughd@google.com, yang@os.amperecomputing.com, ziy@nvidia.com, Dev Jain Subject: [PATCH v4 2/4] mm: Add batched versions of ptep_modify_prot_start/commit Date: Sat, 28 Jun 2025 17:04:33 +0530 Message-Id: <20250628113435.46678-3-dev.jain@arm.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20250628113435.46678-1-dev.jain@arm.com> References: <20250628113435.46678-1-dev.jain@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 38E0E20008 X-Stat-Signature: pkz6rge9wxzkfugcsnxtbs8njjee9gts X-HE-Tag: 1751110520-783215 X-HE-Meta: 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 rp7hnSq1 vTkYKgOeUDUKnnunqf0x6X1SXSB+JZnml3OyQW0+fU+od+VtOUQlkjux2VA/YGh/iQUREC6aq8vBHgWwKcyDGYyznd8gs9jtnA88ca9dBrAg7K4t9hyGPNjoZ9jOhnPfSc6AFTSRpimbHxncOnRs9ijptf27mBOx5eh7EAsYMlx5wZtS+cIzeoBAUtfXrwQxXduO/5bByNjSAAALxJsj7rObEpLAbvbiSkAZpYaNBgpePYEk= 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: 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. */ 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()). + */ +#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. + */ +#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); 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++; -- 2.30.2