linux-kernel - Re: [PATCH] powerpc/32s: Slenderize

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Date:   Mon, 3 Feb 2020 16:57:18 +0000
From:   Joakim Tjernlund <Joakim.Tjernlund@...inera.com>
To:     "christophe.leroy@....fr" <christophe.leroy@....fr>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "paulus@...ba.org" <paulus@...ba.org>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>
CC:     "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] powerpc/32s: Slenderize _tlbia() for powerpc 603/603e

On Mon, 2020-02-03 at 16:47 +0000, Christophe Leroy wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
> 
> 
> _tlbia() is a function used only on 603/603e core, ie on CPUs which
> don't have a hash table.
> 
> _tlbia() uses the tlbia macro which implements a loop of 1024 tlbie.
> 
> On the 603/603e core, flushing the entire TLB requires no more than
> 32 tlbie.
> 
> Replace tlbia by a loop of 32 tlbie.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> ---
>  arch/powerpc/mm/book3s32/hash_low.S | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/mm/book3s32/hash_low.S b/arch/powerpc/mm/book3s32/hash_low.S
> index c11b0a005196..a5039ad10429 100644
> --- a/arch/powerpc/mm/book3s32/hash_low.S
> +++ b/arch/powerpc/mm/book3s32/hash_low.S
> @@ -696,18 +696,21 @@ _GLOBAL(_tlbia)
>         bne-    10b
>         stwcx.  r8,0,r9
>         bne-    10b
> +#endif /* CONFIG_SMP */
> +       li      r5, 32
> +       lis     r4, KERNELBASE@h
> +       mtctr   r5
>         sync
> -       tlbia
> +0:     tlbie   r4
> +       addi    r4, r4, 0x1000

Is page size always 4096 here or does it not matter ?

> +       bdnz    0b
>         sync
> +#ifdef CONFIG_SMP
>         TLBSYNC
>         li      r0,0
>         stw     r0,0(r9)                /* clear mmu_hash_lock */
>         mtmsr   r10
>         SYNC_601
>         isync
> -#else /* CONFIG_SMP */
> -       sync
> -       tlbia
> -       sync
>  #endif /* CONFIG_SMP */
>         blr
> --
> 2.25.0
>