RE: [PATCH v8 2/3] arm64: mm: implement arch_faults_on_old_pte() on arm64

2019-09-23 Thread Justin He (Arm Technology China)
inux-kernel@vger.kernel.org; linux- > m...@kvack.org; Suzuki Poulose ; Punit > Agrawal ; Anshuman Khandual > ; Alex Van Brunt > ; Robin Murphy ; > Thomas Gleixner ; Andrew Morton foundation.org>; Jérôme Glisse ; Ralph Campbell > ; hejia...@gmail.com; Kaly Xin (Arm Technology &g

Re: [PATCH v8 2/3] arm64: mm: implement arch_faults_on_old_pte() on arm64

2019-09-23 Thread Catalin Marinas
On Sat, Sep 21, 2019 at 09:50:53PM +0800, Jia He wrote: > diff --git a/arch/arm64/include/asm/pgtable.h > b/arch/arm64/include/asm/pgtable.h > index e09760ece844..4a9939615e41 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -868,6 +868,18 @@ static

[PATCH v8 2/3] arm64: mm: implement arch_faults_on_old_pte() on arm64

2019-09-21 Thread Jia He
On arm64 without hardware Access Flag, copying fromuser will fail because the pte is old and cannot be marked young. So we always end up with zeroed page after fork() + CoW for pfn mappings. we don't always have a hardware-managed access flag on arm64. Hence implement arch_faults_on_old_pte on