From 6d8278c414cb24ac2b424f50afa99d13a49064b7 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Fri, 1 Jun 2018 20:01:16 +1000 Subject: [PATCH] powerpc/64s/radix: do not flush TLB on spurious fault In the case of a spurious fault (which can happen due to a race with another thread that changes the page table), the default Linux mm code calls flush_tlb_page for that address. This is not required because the pte will be re-fetched. Hash does not wire this up to a hardware TLB flush for this reason. This patch avoids the flush for radix. >From Power ISA v3.0B, p.1090: Setting a Reference or Change Bit or Upgrading Access Authority (PTE Subject to Atomic Hardware Updates) If the only change being made to a valid PTE that is subject to atomic hardware updates is to set the Refer- ence or Change bit to 1 or to add access authorities, a simpler sequence suffices because the translation hardware will refetch the PTE if an access is attempted for which the only problems were reference and/or change bits needing to be set or insufficient access authority. The nest MMU on POWER9 does not re-fetch the PTE after such an access attempt before faulting, so address spaces with a coprocessor attached will continue to flush in these cases. This reduces tlbies for a kernel compile workload from 0.95M to 0.90M. fork --fork --exec benchmark improved 0.5% (12300->12400). Reviewed-by: Aneesh Kumar K.V Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/book3s/64/tlbflush.h | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush.h b/arch/powerpc/include/asm/book3s/64/tlbflush.h index 0cac17253513..ebf572ea621e 100644 --- a/arch/powerpc/include/asm/book3s/64/tlbflush.h +++ b/arch/powerpc/include/asm/book3s/64/tlbflush.h @@ -4,7 +4,7 @@ #define MMU_NO_CONTEXT ~0UL - +#include #include #include @@ -137,6 +137,16 @@ static inline void flush_all_mm(struct mm_struct *mm) #define flush_tlb_page(vma, addr) local_flush_tlb_page(vma, addr) #define flush_all_mm(mm) local_flush_all_mm(mm) #endif /* CONFIG_SMP */ + +#define flush_tlb_fix_spurious_fault flush_tlb_fix_spurious_fault +static inline void flush_tlb_fix_spurious_fault(struct vm_area_struct *vma, + unsigned long address) +{ + /* See ptep_set_access_flags comment */ + if (atomic_read(&vma->vm_mm->context.copros) > 0) + flush_tlb_page(vma, address); +} + /* * flush the page walk cache for the address */