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Subject: Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Scott Wood <scottwood@freescale.com>
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Date: Tue, 20 May 2008 18:02:18 -0400
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On Tue, 2008-05-20 at 16:38 -0500, Scott Wood wrote:
> It looks like we rely on -fno-strict-aliasing to prevent reordering 
> ordinary memory accesses (such as to DMA descriptors) past the I/O 
> access.  It won't prevent reordering of memory reads around an I/O
> read, 
> though, which could be a problem if the I/O read result determines
> the 
> validity of the DMA buffer.  IMHO, a memory clobber would be better.

We probably want a full "memory" clobber then...

Ben.