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From:   Guo Ren <guoren@kernel.org>
Date:   Wed, 24 Nov 2021 15:22:26 +0800
Message-ID: <CAJF2gTRAXAmo4cVSfArf=eMU9CxXZr3kjaKcQ1u8764cnL+N_Q@mail.gmail.com>
Subject: Re: [PATCH] riscv: Fixup one-page wasting
To:     Anup Patel <anup@brainfault.org>
Cc:     "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        linux-csky@vger.kernel.org, Guo Ren <guoren@linux.alibaba.com>,
        Alexandre Ghiti <alex@ghiti.fr>,
        Atish Patra <Atish.Patra@wdc.com>
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On Wed, Nov 24, 2021 at 2:55 PM Anup Patel <anup@brainfault.org> wrote:
>
> On Wed, Nov 24, 2021 at 11:35 AM <guoren@kernel.org> wrote:
> >
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > For small memory systems(Allwinner D1s/F133), one page size memory
> > cannot be ignored.
> >
> > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > Cc: Alexandre Ghiti <alex@ghiti.fr>
> > Cc: Anup Patel <anup@brainfault.org>
> > Cc: Atish Patra <Atish.Patra@wdc.com>
>
> This PATCH breaks the CPU hotplug functionality.
>
> When a CPU/HART is turned off and turned on at runtime, the
> low-level relocate() will be called to enable MMU on the CPU
> being brought-up which in-turn uses trampoline_pg_dir.
Yeah, I forgot that.

How about removing trampoline_pg_dir totally and using
early_pg_dir/swapper_pg_dir for relocate directly?

>
> Regards,
> Anup
>
> > ---
> >  arch/riscv/mm/init.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > index 24b2b8044602..097bb3bc4020 100644
> > --- a/arch/riscv/mm/init.c
> > +++ b/arch/riscv/mm/init.c
> > @@ -241,9 +241,9 @@ unsigned long riscv_pfn_base __ro_after_init;
> >  EXPORT_SYMBOL(riscv_pfn_base);
> >
> >  pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
> > -pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
> >  static pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
> >
> > +pgd_t trampoline_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
> >  pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
> >  static pmd_t __maybe_unused early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
> >
> > --
> > 2.25.1
> >


-- 
Best Regards
 Guo Ren

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