linux-kernel - Re: [PATCH v2 5/6] mm: tlb: Provide flush_*_tlb

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Date:   Fri, 22 May 2020 16:42:55 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Zhenyu Ye <yezhenyu2@...wei.com>
Cc:     peterz@...radead.org, mark.rutland@....com, will@...nel.org,
        aneesh.kumar@...ux.ibm.com, akpm@...ux-foundation.org,
        npiggin@...il.com, arnd@...db.de, rostedt@...dmis.org,
        maz@...nel.org, suzuki.poulose@....com, tglx@...utronix.de,
        yuzhao@...gle.com, Dave.Martin@....com, steven.price@....com,
        broonie@...nel.org, guohanjun@...wei.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org, arm@...nel.org,
        xiexiangyou@...wei.com, prime.zeng@...ilicon.com,
        zhangshaokun@...ilicon.com, kuhn.chenqun@...wei.com
Subject: Re: [PATCH v2 5/6] mm: tlb: Provide flush_*_tlb_range wrappers

On Thu, Apr 23, 2020 at 09:56:55PM +0800, Zhenyu Ye wrote:
> diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
> index 3d7c01e76efc..3eff199d3507 100644
> --- a/mm/pgtable-generic.c
> +++ b/mm/pgtable-generic.c
> @@ -101,6 +101,28 @@ pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address,
>  
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  
> +#ifndef __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
> +
> +#define FLUSH_Pxx_TLB_RANGE(_pxx)					\
> +void flush_##_pxx##_tlb_range(struct vm_area_struct *vma,		\
> +			      unsigned long addr, unsigned long end)	\
> +{									\
> +		struct mmu_gather tlb;					\
> +									\
> +		tlb_gather_mmu(&tlb, vma->vm_mm, addr, end);		\
> +		tlb_start_vma(&tlb, vma);				\
> +		tlb_flush_##_pxx##_range(&tlb, addr, end - addr);	\
> +		tlb_end_vma(&tlb, vma);					\
> +		tlb_finish_mmu(&tlb, addr, end);			\
> +}

I may have confused myself (flush_p??_tlb_* vs. tlb_flush_p??_*) but do
actually need this whole tlb_gather thing here? IIUC (by grep'ing),
flush_p?d_tlb_range() is only called on huge pages, so we should know
the level already.

-- 
Catalin