linux-kernel - Re: [PATCH] powerpc/mm: dump block address translation on book3s/32

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Date:   Fri, 16 Nov 2018 21:20:56 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christophe LEROY <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>, npiggin@...il.com,
        rashmicy@...il.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc/mm: dump block address translation on book3s/32

Christophe LEROY <christophe.leroy@....fr> writes:

> Le 15/11/2018 à 12:46, Michael Ellerman a écrit :
>> Christophe Leroy <christophe.leroy@....fr> writes:
>> 
>>> This patch adds a debugfs file to dump block address translation:
>>>
>>> ~# cat /sys/kernel/debug/block_address_translation
>> 
>> My instinct is it should be in /sys/kernel/debug/powerpc. But I guess
>> the other page table dump files are not.
>
> Lol.
>
> Looks like we have the same instinct ...
>
> But you rejected my patch https://patchwork.ozlabs.org/patch/750426/ :)

Haha. My argument was that the kernel page table dump is not powerpc
specific, but this file *is* powerpc specific. Though I guess it's in
the same are as the page table / hash table dump, so it may as well live
next to them.

>>> diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
>>> index ca96e7be4d0e..2adad10b5856 100644
>>> --- a/arch/powerpc/mm/Makefile
>>> +++ b/arch/powerpc/mm/Makefile
>>> @@ -47,7 +47,7 @@ ifdef CONFIG_PPC_PTDUMP
>>>   obj-$(CONFIG_4xx)		+= dump_linuxpagetables-generic.o
>>>   obj-$(CONFIG_PPC_8xx)		+= dump_linuxpagetables-8xx.o
>>>   obj-$(CONFIG_PPC_BOOK3E_MMU)	+= dump_linuxpagetables-generic.o
>>> -obj-$(CONFIG_PPC_BOOK3S_32)	+= dump_linuxpagetables-generic.o
>>> +obj-$(CONFIG_PPC_BOOK3S_32)	+= dump_linuxpagetables-generic.o dump_bats.o
>> 
>> BOOK3S_32 covers quite a lot of CPUs.
>> 
>> But below the only check is that you're on 601 or 603.
>> 
>> So is the 603 code going to work on all other BOOK3S_32 CPUs?
>
> If I understand function setbat() correctly, it should.
>
> See 
> https://elixir.bootlin.com/linux/v4.20-rc1/source/arch/powerpc/mm/ppc_mmu_32.c#L115 
> Tell me if you see something I missed.

I don't know those 32-bit CPUs at all, so as long as you've thought
about it that's good enough for me. We can catch bugs in testing anyway.

cheers