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Date: Tue, 29 May 2007 18:46:55 -0500
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: Saving to 32 bits of GPRs in signal context
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From: olof@lixom.net (Olof Johansson)
Cc: Ulrich Weigand <Ulrich.Weigand@de.ibm.com>,
	Steve Munroe <sjmunroe@us.ibm.com>,
	linuxppc-dev list <linuxppc-dev@ozlabs.org>,
	Paul Mackerras <paulus@samba.org>, Anton Blanchard <anton@samba.org>
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On Wed, May 30, 2007 at 07:32:33AM +1000, Benjamin Herrenschmidt wrote:
> On Tue, 2007-05-29 at 08:10 -0500, Kumar Gala wrote:
> > This is all problematic since some 64-bit implementations may not  
> > guarantee the upper bits are valid when in 32-bit mode.  Look at the  
> > 'Computation Modes' section in the architecture specs 2.03 or
> > greater  
> > for embedded processors. 
> 
> Yuck. Well, we might need to export a spearate CPU feature bit to
> indicate that it's the case then.

No need for a new bit, you should be able to key off of PPC_FEATURE_64
&& !PPC_FEATURE_BOOKE.


-Olof