linux-kernel - Re: [RFC 11/20] mm/tlb: remove arch-specific tlb_start/end

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Date:   Mon, 1 Feb 2021 13:09:43 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Nadav Amit <nadav.amit@...il.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Nadav Amit <namit@...are.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
        Nick Piggin <npiggin@...il.com>, linux-csky@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        x86@...nel.org
Subject: Re: [RFC 11/20] mm/tlb: remove arch-specific tlb_start/end_vma()

On Sat, Jan 30, 2021 at 04:11:23PM -0800, Nadav Amit wrote:

> diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
> index 427bfcc6cdec..b97136b7010b 100644
> --- a/include/asm-generic/tlb.h
> +++ b/include/asm-generic/tlb.h
> @@ -334,8 +334,8 @@ static inline void __tlb_reset_range(struct mmu_gather *tlb)
>  
>  #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
>  
>  /*
> @@ -362,10 +362,6 @@ static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vm
>  
>  #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

#ifdef CONFIG_ARCH_WANT_AGGRESSIVE_TLB_FLUSH_BATCHING
#error ....
#endif

goes here...


>  static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
>  {
>  	if (tlb->fullmm)
>  		return;
>  
> +	if (IS_ENABLED(CONFIG_ARCH_WANT_AGGRESSIVE_TLB_FLUSH_BATCHING))
> +		return;

Also, can you please stick to the CONFIG_MMU_GATHER_* namespace?

I also don't think AGRESSIVE_FLUSH_BATCHING quite captures what it does.
How about:

	CONFIG_MMU_GATHER_NO_PER_VMA_FLUSH

?