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Subject: Re: TASK_SIZE default 0x80000000 ?
From: Benjamin Herrenschmidt <benh@au1.ibm.com>
To: Kumar Gala <galak@kernel.crashing.org>
In-Reply-To: <796C20BF-1592-4F07-B83B-5EA35CADBA01@kernel.crashing.org>
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	<796C20BF-1592-4F07-B83B-5EA35CADBA01@kernel.crashing.org>
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Date: Mon, 08 Oct 2007 07:05:23 +1000
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Cc: PowerPC dev list <linuxppc-dev@ozlabs.org>,
	Paul Mackerras <paulus@samba.org>
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> Can you explain (a) further -- I'm assuming the BAT mapping is 1:1  
> for that region?
> 
> For (b) it looks like:
> * 40x, 44x, fsl-booke compare against TASK_SIZE in their software  
> handlers.
> * 8xx still tests 0x80000000
> * 6xx (603) compares against KERNELBASE
> 
> It would seem like we should set the default on 8xx & PReP to  
> 0x80000000 and not allow it to be modified since that will break the  
> world and for everything else move it to match KERNELBASE.  Any  
> issues with that?

The proper value is neither :-)

It should be compared against PAGE_OFFSET.

Ben.