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Date: Wed, 30 Sep 2020 14:18:59 +0100 From: Will Deacon <will@...nel.org> To: linux-arm-kernel@...ts.infradead.org Cc: linux-kernel@...r.kernel.org, kernel-team@...roid.com, Will Deacon <will@...nel.org>, Catalin Marinas <catalin.marinas@....com> Subject: [PATCH] arm64: mm: Make flush_tlb_fix_spurious_fault() a no-op Our use of broadcast TLB maintenance means that spurious page-faults that have been handled already by another CPU do not require additional TLB maintenance. Make flush_tlb_fix_spurious_fault() a no-op and rely on the existing TLB invalidation instead. Add an explicit flush_tlb_page() when making a page dirty, as the TLB is permitted to cache the old read-only entry. Cc: Catalin Marinas <catalin.marinas@....com> Link: https://lore.kernel.org/r/20200728092220.GA21800@willie-the-truck Signed-off-by: Will Deacon <will@...nel.org> --- arch/arm64/include/asm/pgtable.h | 8 ++++++++ arch/arm64/mm/fault.c | 4 +++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index bc68da9f5706..02ad3105c14c 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -50,6 +50,14 @@ extern void __pgd_error(const char *file, int line, unsigned long val); __flush_tlb_range(vma, addr, end, PUD_SIZE, false, 1) #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ +/* + * Outside of a few very special situations (e.g. hibernation), we always + * use broadcast TLB invalidation instructions, therefore a spurious page + * fault on one CPU which has been handled concurrently by another CPU + * does not need to perform additional invalidation. + */ +#define flush_tlb_fix_spurious_fault(vma, address) do { } while (0) + /* * ZERO_PAGE is a global shared page that is always zero: used * for zero-mapped memory areas etc.. diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index f07333e86c2f..a696a7921da4 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -218,7 +218,9 @@ int ptep_set_access_flags(struct vm_area_struct *vma, pteval = cmpxchg_relaxed(&pte_val(*ptep), old_pteval, pteval); } while (pteval != old_pteval); - flush_tlb_fix_spurious_fault(vma, address); + /* Invalidate a stale read-only entry */ + if (dirty) + flush_tlb_page(vma, address); return 1; } -- 2.28.0.709.gb0816b6eb0-goog
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