From: Ryan Roberts <ryan.roberts@arm.com> mainline inclusion from mainline-v6.9-rc1 commit fb5451e5f72b31002760083a99fbb41771c4f1ad category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9CUEQ CVE: NA ------------------------------------------------- When core code iterates over a range of ptes and calls ptep_get() for each of them, if the range happens to cover contpte mappings, the number of pte reads becomes amplified by a factor of the number of PTEs in a contpte block. This is because for each call to ptep_get(), the implementation must read all of the ptes in the contpte block to which it belongs to gather the access and dirty bits. This causes a hotspot for fork(), as well as operations that unmap memory such as munmap(), exit and madvise(MADV_DONTNEED). Fortunately we can fix this by implementing pte_batch_hint() which allows their iterators to skip getting the contpte tail ptes when gathering the batch of ptes to operate on. This results in the number of PTE reads returning to 1 per pte. Link: https://lkml.kernel.org/r/20240215103205.2607016-17-ryan.roberts@arm.com Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> Acked-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: David Hildenbrand <david@redhat.com> Tested-by: John Hubbard <jhubbard@nvidia.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Barry Song <21cnbao@gmail.com> Cc: Borislav Petkov (AMD) <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Morse <james.morse@arm.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will@kernel.org> Cc: Yang Shi <shy828301@gmail.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> (cherry picked from commit fb5451e5f72b31002760083a99fbb41771c4f1ad) Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> --- arch/arm64/include/asm/pgtable.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index a8f1a35e3086..d759a20d2929 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1213,6 +1213,15 @@ static inline void contpte_try_unfold(struct mm_struct *mm, unsigned long addr, __contpte_try_unfold(mm, addr, ptep, pte); } +#define pte_batch_hint pte_batch_hint +static inline unsigned int pte_batch_hint(pte_t *ptep, pte_t pte) +{ + if (!pte_valid_cont(pte)) + return 1; + + return CONT_PTES - (((unsigned long)ptep >> 3) & (CONT_PTES - 1)); +} + /* * The below functions constitute the public API that arm64 presents to the * core-mm to manipulate PTE entries within their page tables (or at least this -- 2.27.0