[PATCH 06/10] arm64: tlbflush: avoid flushing when fullmm == 1

[Catalin Marinas]

On Thu, Sep 17, 2015 at 01:50:15PM +0100, Will Deacon wrote:
> The TLB gather code sets fullmm=1 when tearing down the entire address
> space for an mm_struct on exit or execve. Given that the ASID allocator
> will never re-allocate a dirty ASID, this flushing is not needed and can
> simply be avoided in the flushing code.
> 
> Signed-off-by: Will Deacon <will.deacon at arm.com>
> ---
>  arch/arm64/include/asm/tlb.h | 26 +++++++++++++++-----------
>  1 file changed, 15 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
> index d6e6b6660380..ffdaea7954bb 100644
> --- a/arch/arm64/include/asm/tlb.h
> +++ b/arch/arm64/include/asm/tlb.h
> @@ -37,17 +37,21 @@ static inline void __tlb_remove_table(void *_table)
>  
>  static inline void tlb_flush(struct mmu_gather *tlb)
>  {
> -	if (tlb->fullmm) {
> -		flush_tlb_mm(tlb->mm);
> -	} else {
> -		struct vm_area_struct vma = { .vm_mm = tlb->mm, };
> -		/*
> -		 * The intermediate page table levels are already handled by
> -		 * the __(pte|pmd|pud)_free_tlb() functions, so last level
> -		 * TLBI is sufficient here.
> -		 */
> -		__flush_tlb_range(&vma, tlb->start, tlb->end, true);
> -	}
> +	struct vm_area_struct vma = { .vm_mm = tlb->mm, };
> +
> +	/*
> +	 * The ASID allocator will either invalidate the ASID or mark
> +	 * it as used.
> +	 */
> +	if (tlb->fullmm)
> +		return;

BTW, do we actually need this flush_tlb_mm() with the current ASID
allocator? It doesn't reuse old ASIDs either before a full TLBI (just
trying to remember if we had any logic; or maybe it was needed before
non-lazy __pte_free_tlb).

-- 
Catalin