linux-kernel - Re: [PATCH v3 2/2] LoongArch: update local TLB if PTE entry exists

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Date:   Thu, 29 Sep 2022 19:42:32 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Qi Zheng <zhengqi.arch@...edance.com>
Cc:     akpm@...ux-foundation.org, maobibo@...ngson.cn,
        chenhuacai@...ngson.cn, songmuchun@...edance.com, david@...hat.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        loongarch@...ts.linux.dev, chris@...kel.net, jcmvbkbc@...il.com
Subject: Re: [PATCH v3 2/2] LoongArch: update local TLB if PTE entry exists

Hi, all,

Should this patch go via mm tree or loongarch tree? If via mm tree, then

Acked-by: Huacai Chen <chenhuacai@...ngson.cn>

On Thu, Sep 29, 2022 at 7:23 PM Qi Zheng <zhengqi.arch@...edance.com> wrote:
>
> Currently, the implementation of update_mmu_tlb() is empty if
> __HAVE_ARCH_UPDATE_MMU_TLB is not defined. Then if two threads
> concurrently fault at the same page, the second thread that did
> not win the race will give up and do nothing. In the LoongArch
> architecture, this second thread will trigger another fault,
> and only updates its local TLB.
>
> Instead of triggering another fault, it's better to implement
> update_mmu_tlb() to directly update the local TLB of the second
> thread. Just do it.
>
> Suggested-by: Bibo Mao <maobibo@...ngson.cn>
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> ---
>  arch/loongarch/include/asm/pgtable.h | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
> index 8ea57e2f0e04..946704bee599 100644
> --- a/arch/loongarch/include/asm/pgtable.h
> +++ b/arch/loongarch/include/asm/pgtable.h
> @@ -412,6 +412,9 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
>         __update_tlb(vma, address, ptep);
>  }
>
> +#define __HAVE_ARCH_UPDATE_MMU_TLB
> +#define update_mmu_tlb update_mmu_cache
> +
>  static inline void update_mmu_cache_pmd(struct vm_area_struct *vma,
>                         unsigned long address, pmd_t *pmdp)
>  {
> --
> 2.20.1
>
>