linux-kernel - Re: [PATCH 4/4] arm64: support batched/deferred tlb shootdown during page reclamation

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Date:   Fri, 8 Jul 2022 09:10:23 +1200
From:   Barry Song <21cnbao@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        LAK <linux-arm-kernel@...ts.infradead.org>, x86 <x86@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        Arnd Bergmann <arnd@...db.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Darren Hart <darren@...amperecomputing.com>,
        Yicong Yang <yangyicong@...ilicon.com>, huzhanyuan@...o.com,
        李培锋(wink) <lipeifeng@...o.com>,
        张诗明(Simon Zhang) 
        <zhangshiming@...o.com>, 郭健 <guojian@...o.com>,
        real mz <realmz6@...il.com>,
        Barry Song <v-songbaohua@...o.com>,
        Nadav Amit <namit@...are.com>, Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH 4/4] arm64: support batched/deferred tlb shootdown during
 page reclamation

On Fri, Jul 8, 2022 at 1:50 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Fri, Jul 08, 2022 at 12:52:42AM +1200, Barry Song wrote:
>
> > diff --git a/arch/arm64/include/asm/tlbbatch.h b/arch/arm64/include/asm/tlbbatch.h
> > new file mode 100644
> > index 000000000000..fedb0b87b8db
> > --- /dev/null
> > +++ b/arch/arm64/include/asm/tlbbatch.h
> > @@ -0,0 +1,12 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef _ARCH_ARM64_TLBBATCH_H
> > +#define _ARCH_ARM64_TLBBATCH_H
> > +
> > +struct arch_tlbflush_unmap_batch {
> > +     /*
> > +      * For arm64, HW can do tlb shootdown, so we don't
> > +      * need to record cpumask for sending IPI
> > +      */
> > +};
> > +
> > +#endif /* _ARCH_ARM64_TLBBATCH_H */
> > diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> > index 412a3b9a3c25..b3ed163267ca 100644
> > --- a/arch/arm64/include/asm/tlbflush.h
> > +++ b/arch/arm64/include/asm/tlbflush.h
> > @@ -272,6 +272,19 @@ static inline void flush_tlb_page(struct vm_area_struct *vma,
> >       dsb(ish);
> >  }
> >
> > +static inline void arch_tlbbatch_add_mm(struct arch_tlbflush_unmap_batch *batch,
> > +                                     struct mm_struct *mm,
> > +                                     struct vm_area_struct *vma,
> > +                                     unsigned long uaddr)
> > +{
> > +     flush_tlb_page_nosync(vma, uaddr);
> > +}
>
> You're passing that vma along just to get the mm, that's quite silly and
> trivially fixed.

Yes, this was silly. will include your fix in v2.

>
>
> diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> index 412a3b9a3c25..87505ecce1f0 100644
> --- a/arch/arm64/include/asm/tlbflush.h
> +++ b/arch/arm64/include/asm/tlbflush.h
> @@ -254,17 +254,23 @@ static inline void flush_tlb_mm(struct mm_struct *mm)
>         dsb(ish);
>  }
>
> -static inline void flush_tlb_page_nosync(struct vm_area_struct *vma,
> -                                        unsigned long uaddr)
> +static inline void __flush_tlb_page_nosync(struct mm_struct *mm,
> +                                          unsigned long uaddr)
>  {
>         unsigned long addr;
>
>         dsb(ishst);
> -       addr = __TLBI_VADDR(uaddr, ASID(vma->vm_mm));
> +       addr = __TLBI_VADDR(uaddr, ASID(mm));
>         __tlbi(vale1is, addr);
>         __tlbi_user(vale1is, addr);
>  }
>
> +static inline void flush_tlb_page_nosync(struct vm_area_struct *vma,
> +                                        unsigned long uaddr)
> +{
> +       return __flush_tlb_page_nosync(vma->vm_mm, uaddr);
> +}
> +
>  static inline void flush_tlb_page(struct vm_area_struct *vma,
>                                   unsigned long uaddr)
>  {

Thanks
Barry