linux-kernel - Re: [PATCH 3/4] mmu_gather: Let there be one tlb_{start,end}

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Date:   Fri, 8 Jul 2022 14:32:49 +0100
From:   Will Deacon <will@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Jann Horn <jannh@...gle.com>,
        Linus Torvalds <torvalds@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Dave Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Guo Ren <guoren@...nel.org>, David Miller <davem@...emloft.net>
Subject: Re: [PATCH 3/4] mmu_gather: Let there be one tlb_{start,end}_vma()
 implementation

On Fri, Jul 08, 2022 at 09:18:05AM +0200, Peter Zijlstra wrote:
> Now that architectures are no longer allowed to override
> tlb_{start,end}_vma() re-arrange code so that there is only one
> implementation for each of these functions.
> 
> This much simplifies trying to figure out what they actually do.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  include/asm-generic/tlb.h |   15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
> 
> --- a/include/asm-generic/tlb.h
> +++ b/include/asm-generic/tlb.h
> @@ -346,8 +346,8 @@ static inline void __tlb_reset_range(str
>  
>  #ifdef CONFIG_MMU_GATHER_NO_RANGE
>  
> -#if defined(tlb_flush) || defined(tlb_start_vma) || defined(tlb_end_vma)
> -#error MMU_GATHER_NO_RANGE relies on default tlb_flush(), tlb_start_vma() and tlb_end_vma()
> +#if defined(tlb_flush)
> +#error MMU_GATHER_NO_RANGE relies on default tlb_flush()
>  #endif
>  
>  /*
> @@ -367,17 +367,10 @@ static inline void tlb_flush(struct mmu_
>  static inline void
>  tlb_update_vma_flags(struct mmu_gather *tlb, struct vm_area_struct *vma) { }
>  
> -#define tlb_end_vma tlb_end_vma
> -static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma) { }
> -
>  #else /* CONFIG_MMU_GATHER_NO_RANGE */
>  
>  #ifndef tlb_flush
>  
> -#if defined(tlb_start_vma) || defined(tlb_end_vma)
> -#error Default tlb_flush() relies on default tlb_start_vma() and tlb_end_vma()
> -#endif
> -
>  /*
>   * When an architecture does not provide its own tlb_flush() implementation
>   * but does have a reasonably efficient flush_vma_range() implementation
> @@ -498,7 +491,6 @@ static inline unsigned long tlb_get_unma
>   * case where we're doing a full MM flush.  When we're doing a munmap,
>   * the vmas are adjusted to only cover the region to be torn down.
>   */
> -#ifndef tlb_start_vma
>  static inline void tlb_start_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
>  {
>  	if (tlb->fullmm)
> @@ -509,9 +501,7 @@ static inline void tlb_start_vma(struct
>  	flush_cache_range(vma, vma->vm_start, vma->vm_end);
>  #endif
>  }
> -#endif
>  
> -#ifndef tlb_end_vma
>  static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
>  {
>  	if (tlb->fullmm || IS_ENABLED(CONFIG_MMU_GATHER_MERGE_VMAS))
> @@ -525,7 +515,6 @@ static inline void tlb_end_vma(struct mm
>  	 */
>  	tlb_flush_mmu_tlbonly(tlb);
>  }
> -#endif

Much nicer:

Acked-by: Will Deacon <will@...nel.org>

Will