Re: [PATCH v6 11/18] arm64/mm: Split __flush_tlb_range() to elide trailing DSB

[Mark Rutland]

On Thu, Feb 15, 2024 at 10:31:58AM +0000, Ryan Roberts wrote:
> Split __flush_tlb_range() into __flush_tlb_range_nosync() +
> __flush_tlb_range(), in the same way as the existing flush_tlb_page()
> arrangement. This allows calling __flush_tlb_range_nosync() to elide the
> trailing DSB. Forthcoming "contpte" code will take advantage of this
> when clearing the young bit from a contiguous range of ptes.
> 
> Ordering between dsb and mmu_notifier_arch_invalidate_secondary_tlbs()
> has changed, but now aligns with the ordering of __flush_tlb_page(). It
> has been discussed that __flush_tlb_page() may be wrong though.
> Regardless, both will be resolved separately if needed.
> 
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> Tested-by: John Hubbard <jhubbard@xxxxxxxxxx>
> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>

Acked-by: Mark Rutland <mark.rutland@xxxxxxx>

Mark.

> ---
>  arch/arm64/include/asm/tlbflush.h | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> index 1deb5d789c2e..3b0e8248e1a4 100644
> --- a/arch/arm64/include/asm/tlbflush.h
> +++ b/arch/arm64/include/asm/tlbflush.h
> @@ -422,7 +422,7 @@ do {									\
>  #define __flush_s2_tlb_range_op(op, start, pages, stride, tlb_level) \
>  	__flush_tlb_range_op(op, start, pages, stride, 0, tlb_level, false, kvm_lpa2_is_enabled());
>  
> -static inline void __flush_tlb_range(struct vm_area_struct *vma,
> +static inline void __flush_tlb_range_nosync(struct vm_area_struct *vma,
>  				     unsigned long start, unsigned long end,
>  				     unsigned long stride, bool last_level,
>  				     int tlb_level)
> @@ -456,10 +456,19 @@ static inline void __flush_tlb_range(struct vm_area_struct *vma,
>  		__flush_tlb_range_op(vae1is, start, pages, stride, asid,
>  				     tlb_level, true, lpa2_is_enabled());
>  
> -	dsb(ish);
>  	mmu_notifier_arch_invalidate_secondary_tlbs(vma->vm_mm, start, end);
>  }
>  
> +static inline void __flush_tlb_range(struct vm_area_struct *vma,
> +				     unsigned long start, unsigned long end,
> +				     unsigned long stride, bool last_level,
> +				     int tlb_level)
> +{
> +	__flush_tlb_range_nosync(vma, start, end, stride,
> +				 last_level, tlb_level);
> +	dsb(ish);
> +}
> +
>  static inline void flush_tlb_range(struct vm_area_struct *vma,
>  				   unsigned long start, unsigned long end)
>  {
> -- 
> 2.25.1
>