linux-kernel - Re: [PATCH v7 06/12] arm64: tlb: Refactor the core flush algorithm of __flush_tlb

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Date:   Wed, 2 Aug 2023 16:31:18 -0700
From:   Raghavendra Rao Ananta <rananta@...gle.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Jing Zhang <jingzhangos@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-mips@...r.kernel.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Catalin Marinas <catalin.marinas@....com>,
        Gavin Shan <gshan@...hat.com>,
        Shaoqin Huang <shahuang@...hat.com>
Subject: Re: [PATCH v7 06/12] arm64: tlb: Refactor the core flush algorithm of __flush_tlb_range

On Wed, Aug 2, 2023 at 8:58 AM Marc Zyngier <maz@...nel.org> wrote:
>
> On Mon, 31 Jul 2023 18:36:47 +0100,
> Raghavendra Rao Ananta <rananta@...gle.com> wrote:
> >
> > On Thu, Jul 27, 2023 at 3:58 AM Marc Zyngier <maz@...nel.org> wrote:
> > >
> > > On Sat, 22 Jul 2023 03:22:45 +0100,
> > > Raghavendra Rao Ananta <rananta@...gle.com> wrote:
> > > >
> > > > Currently, the core TLB flush functionality of __flush_tlb_range()
> > > > hardcodes vae1is (and variants) for the flush operation. In the
> > > > upcoming patches, the KVM code reuses this core algorithm with
> > > > ipas2e1is for range based TLB invalidations based on the IPA.
> > > > Hence, extract the core flush functionality of __flush_tlb_range()
> > > > into its own macro that accepts an 'op' argument to pass any
> > > > TLBI operation, such that other callers (KVM) can benefit.
> > > >
> > > > No functional changes intended.
> > > >
> > > > Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
> > > > Reviewed-by: Catalin Marinas <catalin.marinas@....com>
> > > > Reviewed-by: Gavin Shan <gshan@...hat.com>
> > > > Reviewed-by: Shaoqin Huang <shahuang@...hat.com>
> > > > ---
> > > >  arch/arm64/include/asm/tlbflush.h | 109 +++++++++++++++---------------
> > > >  1 file changed, 56 insertions(+), 53 deletions(-)
> > > >
> > > > diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> > > > index 412a3b9a3c25..f7fafba25add 100644
> > > > --- a/arch/arm64/include/asm/tlbflush.h
> > > > +++ b/arch/arm64/include/asm/tlbflush.h
> > > > @@ -278,14 +278,62 @@ static inline void flush_tlb_page(struct vm_area_struct *vma,
> > > >   */
> > > >  #define MAX_TLBI_OPS PTRS_PER_PTE
> > > >
> > > > +/* When the CPU does not support TLB range operations, flush the TLB
> > > > + * entries one by one at the granularity of 'stride'. If the TLB
> > > > + * range ops are supported, then:
> > >
> > > Comment format (the original was correct).
> > >
> > Isn't the format the same as original? Or are you referring to the
> > fact that it needs to be placed inside the macro definition?
>
> No, I'm referring to the multiline comment that starts with:
>
>         /*  When the CPU does not support TLB range operations...
>
> instead of the required:
>
>         /*
>          * When the CPU does not support TLB range operations
>
> which was correct before the coment was moved.
>
Oh I see! I'll fix it in v8.

Thanks,
Raghavendra
> Thanks,
>
>         M.
>
> --
> Without deviation from the norm, progress is not possible.