linux-kernel - Re: [PATCH v1 05/10] powerpc/mm: Do early ioremaps from top to bottom on PPC64 too.

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Message-ID: <fdfc4c49-d6b9-4458-2465-666a2e10680d@c-s.fr>
Date:   Tue, 20 Aug 2019 07:10:03 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        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 05/10] powerpc/mm: Do early ioremaps from top to bottom
 on PPC64 too.



Le 20/08/2019 à 02:20, Michael Ellerman a écrit :
> Nicholas Piggin <npiggin@...il.com> writes:
>> Christophe Leroy's on August 14, 2019 6:11 am:
>>> Until vmalloc system is up and running, ioremap basically
>>> allocates addresses at the border of the IOREMAP area.
>>>
>>> On PPC32, addresses are allocated down from the top of the area
>>> while on PPC64, addresses are allocated up from the base of the
>>> area.
>>   
>> This series looks pretty good to me, but I'm not sure about this patch.
>>
>> It seems like quite a small divergence in terms of code, and it looks
>> like the final result still has some ifdefs in these functions. Maybe
>> you could just keep existing behaviour for this cleanup series so it
>> does not risk triggering some obscure regression?
> 
> Yeah that is also my feeling. Changing it *should* work, and I haven't
> found anything that breaks yet, but it's one of those things that's
> bound to break something for some obscure reason.
> 
> Christophe do you think you can rework it to retain the different
> allocation directions at least for now?
> 

Yes I have started addressing the comments I received, and I think for 
now I'll keep all the machinery aside from the merge. Not sure yet if 
I'll leave it in pgtables_32/64.c or if I'll add ioremap_32/64.c

Christophe