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In-Reply-To: <mhng-60806045-5ac7-4057-b596-a4d9cb79b7be@palmerdabbelt-glaptop>
From:   Guo Ren <guoren@kernel.org>
Date:   Sun, 30 May 2021 13:33:52 +0800
Message-ID: <CAJF2gTSPQmWLon40GafUjEjeMfu3ZPsPREzE+4W5+0uWjj=F_A@mail.gmail.com>
Subject: Re: [PATCH V4 1/2] riscv: Fixup _PAGE_GLOBAL in _PAGE_KERNEL
To:     Palmer Dabbelt <palmerdabbelt@google.com>
Cc:     Anup Patel <Anup.Patel@wdc.com>, Arnd Bergmann <arnd@arndb.de>,
        Christoph Hellwig <hch@lst.de>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        linux-sunxi@lists.linux.dev, Guo Ren <guoren@linux.alibaba.com>
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On Sun, May 30, 2021 at 7:42 AM <palmerdabbelt@google.com> wrote:
>
> On Tue, 25 May 2021 22:49:20 PDT (-0700), guoren@kernel.org wrote:
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > Kernel virtual address translation should avoid to use ASIDs or it'll
> > cause more TLB-miss and TLB-refill. Because the current ASID in satp
> > belongs to the current process, but the target kernel va TLB entry's
> > ASID still belongs to the previous process.
>
> Sorry, I still can't quite figure out what this is trying to say.  I
> went ahead and re-wrote the commit text to
>
>     riscv: Use global mappings for kernel pages
>
>     We map kernel pages into all addresses spages, so they can be marked as
>     global.  This allows hardware to avoid flushing the kernel mappings when
>     moving between address spaces.
Okay

>
> LMK if I'm misunderstanding something here, it's on for-next.
>
> >
> > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > Reviewed-by: Anup Patel <anup@brainfault.org>
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> > Cc: Palmer Dabbelt <palmerdabbelt@google.com>
> > ---
> >  arch/riscv/include/asm/pgtable.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> > index 9469f46..346a3c6 100644
> > --- a/arch/riscv/include/asm/pgtable.h
> > +++ b/arch/riscv/include/asm/pgtable.h
> > @@ -134,7 +134,8 @@
> >                               | _PAGE_WRITE \
> >                               | _PAGE_PRESENT \
> >                               | _PAGE_ACCESSED \
> > -                             | _PAGE_DIRTY)
> > +                             | _PAGE_DIRTY \
> > +                             | _PAGE_GLOBAL)
> >
> >  #define PAGE_KERNEL          __pgprot(_PAGE_KERNEL)
> >  #define PAGE_KERNEL_READ     __pgprot(_PAGE_KERNEL & ~_PAGE_WRITE)


-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/