linux-kernel - Re: [PATCH v4 2/5] powerpc/mm/slice: Enhance for supporting PPC32

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Message-ID: <20180211235944.14c2be39@roar.ozlabs.ibm.com>
Date:   Sun, 11 Feb 2018 23:59:44 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Scott Wood <oss@...error.net>, aneesh.kumar@...ux.vnet.ibm.com,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v4 2/5] powerpc/mm/slice: Enhance for supporting PPC32

On Sat, 10 Feb 2018 13:54:27 +0100 (CET)
Christophe Leroy <christophe.leroy@....fr> wrote:

> In preparation for the following patch which will fix an issue on
> the 8xx by re-using the 'slices', this patch enhances the
> 'slices' implementation to support 32 bits CPUs.
> 
> On PPC32, the address space is limited to 4Gbytes, hence only the low
> slices will be used.
> 
> This patch moves "slices" functions prototypes from page64.h to slice.h
> 
> The high slices use bitmaps. As bitmap functions are not prepared to
> handling bitmaps of size 0, the bitmap_xxx() calls are wrapped into
> slice_bitmap_xxx() functions which will void on PPC32

On this last point, I think it would be better to put these with the
existing slice bitmap functions in slice.c and just have a few #ifdefs
for SLICE_NUM_HIGH == 0.

Thanks,
Nick