linux-kernel - Re: [PATCH v1 2/6] powerpc/8xx: Always pin kernel text TLB

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Message-ID: <87ft4ese7q.fsf@mpe.ellerman.id.au>
Date:   Thu, 10 Dec 2020 11:21:29 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v1 2/6] powerpc/8xx: Always pin kernel text TLB

Christophe Leroy <christophe.leroy@...roup.eu> writes:
> Le 09/12/2020 à 11:43, Michael Ellerman a écrit :
>> Christophe Leroy <christophe.leroy@...roup.eu> writes:
>>> There is no big poing in not pinning kernel text anymore, as now
>>> we can keep pinned TLB even with things like DEBUG_PAGEALLOC.
>>>
>>> Remove CONFIG_PIN_TLB_TEXT, making it always right.
>>>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
>>> ---
>>>   arch/powerpc/Kconfig               |  3 +--
>>>   arch/powerpc/kernel/head_8xx.S     | 20 +++-----------------
>>>   arch/powerpc/mm/nohash/8xx.c       |  3 +--
>>>   arch/powerpc/platforms/8xx/Kconfig |  7 -------
>>>   4 files changed, 5 insertions(+), 28 deletions(-)
>>>
>> ...
>>> diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c
>>> index 231ca95f9ffb..19a3eec1d8c5 100644
>>> --- a/arch/powerpc/mm/nohash/8xx.c
>>> +++ b/arch/powerpc/mm/nohash/8xx.c
>>> @@ -186,8 +186,7 @@ void mmu_mark_initmem_nx(void)
>>>   	mmu_mapin_ram_chunk(0, boundary, PAGE_KERNEL_TEXT, false);
>>>   	mmu_mapin_ram_chunk(boundary, einittext8, PAGE_KERNEL, false);
>>>   
>>> -	if (IS_ENABLED(CONFIG_PIN_TLB_TEXT))
>>> -		mmu_pin_tlb(block_mapped_ram, false);
>>> +	mmu_pin_tlb(block_mapped_ram, false);
>>>   }
>> 
>> This broke mpc885_ads_defconfig with:
>
> :surprise:
>
> How did I get it working ? Anyway, thanks for fixing it.

No worries. I figured you must have tested with some other series(s)
applied and/or with different configs, it happens :)

cheers