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: <87r25g662n.fsf@concordia.ellerman.id.au>
Date:   Tue, 20 Aug 2019 10:20:16 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Nicholas Piggin <npiggin@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        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.

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?

cheers