linux-kernel - Re: [PATCH v2 2/4] riscv: Improve flush_tlb

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Message-ID: <20230728-50d247a7253aaf9468cd8b3d@orel>
Date:   Fri, 28 Jul 2023 15:40:40 +0200
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Alexandre Ghiti <alexghiti@...osinc.com>
Cc:     Will Deacon <will@...nel.org>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nick Piggin <npiggin@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Mayuresh Chitale <mchitale@...tanamicro.com>,
        Vincent Chen <vincent.chen@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] riscv: Improve flush_tlb_range() for hugetlb pages

On Thu, Jul 27, 2023 at 08:55:51PM +0200, Alexandre Ghiti wrote:
> flush_tlb_range() uses a fixed stride of PAGE_SIZE and in its current form,
> when a hugetlb mapping needs to be flushed, flush_tlb_range() flushes the
> whole tlb: so set a stride of the size of the hugetlb mapping in order to
> only flush the hugetlb mapping.
> 
> Note that THPs are directly handled by flush_pmd_tlb_range().
> 
> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
> ---
>  arch/riscv/mm/tlbflush.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
> index fa03289853d8..3e4acef1f6bc 100644
> --- a/arch/riscv/mm/tlbflush.c
> +++ b/arch/riscv/mm/tlbflush.c
> @@ -3,6 +3,7 @@
>  #include <linux/mm.h>
>  #include <linux/smp.h>
>  #include <linux/sched.h>
> +#include <linux/hugetlb.h>
>  #include <asm/sbi.h>
>  #include <asm/mmu_context.h>
>  
> @@ -147,7 +148,14 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
>  void flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
>  		     unsigned long end)
>  {
> -	__flush_tlb_range(vma->vm_mm, start, end - start, PAGE_SIZE);
> +	unsigned long stride_shift;
> +
> +	stride_shift = is_vm_hugetlb_page(vma) ?
> +				huge_page_shift(hstate_vma(vma)) :
> +				PAGE_SHIFT;

We want the size below instead of the shift, so we can just use
huge_page_size() and PAGE_SIZE here.

> +
> +	__flush_tlb_range(vma->vm_mm,
> +			  start, end - start, 1 << stride_shift);

Shouldn't need to wrap this line.

>  }
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  void flush_pmd_tlb_range(struct vm_area_struct *vma, unsigned long start,
> -- 
> 2.39.2
>

Otherwise,

Reviewed-by: Andrew Jones <ajones@...tanamicro.com>

Thanks,
drew