diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush.h b/arch/powerpc/include/asm/book3s/64/tlbflush.h index d2e80f178b6d..206f920fe5b9 100644 --- a/arch/powerpc/include/asm/book3s/64/tlbflush.h +++ b/arch/powerpc/include/asm/book3s/64/tlbflush.h @@ -138,9 +138,29 @@ static inline void flush_all_mm(struct mm_struct *mm) 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); + /* + * Book3S 64 does not require spurious fault flushes because the PTE + * must be re-fetched in case of an access permission problem. So the + * only reason for a spurious fault should be concurrent modification + * to the PTE, in which case the PTE will eventually be re-fetched by + * the MMU when it attempts the access again. + * + * See: Power ISA Version 3.1B, 6.10.1.2 Modifying a Translation Table + * Entry, 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 Reference or Change bit to + * 1 or to upgrade access authority, 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 in POWER9 does not perform this PTE re-fetch, but + * it avoids the spurious fault problem by flushing the TLB before + * upgrading PTE permissions, see radix__ptep_set_access_flags. + */ } extern bool tlbie_capable;