linux-kernel - Re: [PATCH 1/6] powerpc/mm/32: Use pfn_valid to check if pointer is in RAM

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Message-ID: <20180221144410.ckm4m366scrgk2rm@latitude>
Date:   Wed, 21 Feb 2018 15:44:10 +0100
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
To:     Jonathan Neuschäfer <j.neuschaefer@....net>
Cc:     christophe leroy <christophe.leroy@....fr>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>, linux-mm@...ck.org,
        Joel Stanley <joel@....id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Balbir Singh <bsingharora@...il.com>,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH 1/6] powerpc/mm/32: Use pfn_valid to check if pointer is
 in RAM

On Wed, Feb 21, 2018 at 02:51:19PM +0100, Jonathan Neuschäfer wrote:
[...]
> While looking through arch/powerpc/mm, I noticed that there's a
> page_is_ram function, which simply uses the memblocks directly, on
> PPC32.

Oops, I misread the code here. memblock is used on PPC64.

> It seems like a good candidate for the RAM check in
> __ioremap_caller, except that there's this code, which apparently
> trashes memblock 0 completely on non-CONFIG_NEED_MULTIPLE_NODES:
> 
>   https://elixir.bootlin.com/linux/v4.16-rc2/source/arch/powerpc/mm/mem.c#L223
> 
> 
> Thanks,
> Jonathan Neuschäfer



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