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Date: Fri, 30 May 2014 19:02:12 +0100
From: Will Deacon <will.deacon@arm.com>
To: Rob Herring <robherring2@gmail.com>
Cc: Liu Hua <sdu.liu@huawei.com>,
        Russell King - ARM Linux <linux@arm.linux.org.uk>,
        Nicolas Pitre <nicolas.pitre@linaro.org>,
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	<linux-arm-kernel@lists.infradead.org>,
        Rabin Vincent <rabin@rab.in>
Subject: Re: [PATCH v3 2/2] ARM : change fixmap mapping region to support 32
 CPUs
Message-ID: <20140530180212.GF22895@arm.com>
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On Fri, May 30, 2014 at 04:33:46PM +0100, Rob Herring wrote:
> On Tue, Apr 15, 2014 at 6:06 AM, Liu Hua <sdu.liu@huawei.com> wrote:
> > In 32-bit ARM systems, the fixmap mapping region can support
> > no more than 14 CPUs(total: 896k; one CPU: 64K). And we can
> > configure NR_CPUS up to 32. So there is a mismatch.
> >
> > This patch moves fixmapping region downwards to region
> > 0xffc00000-0xffe00000. Then the fixmap mapping region can
> > support up to 32 CPUs
> 
> Ugg, this series breaks using fixmap for anything other than kmap
> since 32 cpus requires all 2MB of the region and nothing is left.
> There's work in flight to support early_ioremap, early console, and RO
> text patching which all use the fixmap region.
> 
> There's a couple of options to solve this:
> 
> - Only support up to 16 cpus. It could be anywhere between 17-31, but
> that seems somewhat unlikely. Are we really ever going to see 32-bit
> 32 core systems?

I'd be fine with restricting the limit to 16 CPUs.

Will