Re: [RFC 01/10] x86/mm: Reimplement flush_tlb_page() using flush_tlb_mm_range()

Borislav Petkov
2017-05-11T17:41:39Z

On Sun, May 07, 2017 at 05:38:30AM -0700, Andy Lutomirski wrote:
> flush_tlb_page() was very similar to flush_tlb_mm_range() except that
> it had a couple of issues:
>
> - It was missing an smp_mb() in the case where
> current->active_mm != mm. (This is a longstanding bug reported by
> Nadav Amit.)
>
> - It was missing tracepoints and vm counter updates.
>
> The only reason that I can see for keeping it at as a separate
> function is that it could avoid a few branches that
> flush_tlb_mm_range() needs to decide to flush just one page. This
> hardly seems worthwhile. If we decide we want to get rid of those
> branches again, a better way would be to introduce an
> __flush_tlb_mm_range() helper and make both flush_tlb_page() and
> flush_tlb_mm_range() use it.
>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Cc: Nadav Amit <namit@vmware.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> arch/x86/include/asm/tlbflush.h | 6 +++++-
> arch/x86/mm/tlb.c | 27 ---------------------------
> 2 files changed, 5 insertions(+), 28 deletions(-)
>
> diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
> index 6ed9ea469b48..5ed64cdaf536 100644
> --- a/arch/x86/include/asm/tlbflush.h
> +++ b/arch/x86/include/asm/tlbflush.h
> @@ -307,11 +307,15 @@ static inline void flush_tlb_kernel_range(unsigned long start,
> flush_tlb_mm_range(vma->vm_mm, start, end, vma->vm_flags)
>
> extern void flush_tlb_all(void);
> -extern void flush_tlb_page(struct vm_area_struct *, unsigned long);
> extern void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
> unsigned long end, unsigned long vmflag);
> extern void flush_tlb_kernel_range(unsigned long start, unsigned long end);
>
> +static inline void flush_tlb_page(struct vm_area_struct *vma, unsigned long a)
> +{
> + flush_tlb_mm_range(vma->vm_mm, a, a + PAGE_SIZE, 0);

VM_NONE);

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Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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