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Date: Thu, 29 Mar 2007 09:52:52 -0500
To: Jake Moilanen <moilanen@austin.ibm.com>
Subject: Re: [PATCH] DMA 4GB boundary protection
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From: olof@lixom.net (Olof Johansson)
Cc: paulus@samba.org, linuxppc-dev@ozlabs.org
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On Thu, Mar 29, 2007 at 08:44:02AM -0500, Jake Moilanen wrote:
> On Thu, 2007-03-29 at 09:23 +1000, Benjamin Herrenschmidt wrote:
> > On Wed, 2007-03-28 at 13:17 -0500, Jake Moilanen wrote:
> > 
> > > One more try.
> > 
> > And patch is still mangled....
> 
> Hrm....I should just go back to Sylpheed.  
> 
> Unmangled version:
> 
> 
> There are many adapters which can not handle DMAing acrosss any 4 GB
> boundary.  For instance the latest Emulex adapters.  
> 
> This normally is not an issue as firmware gives dma-windows under
> 4gigs.  However, some of the new System-P boxes have dma-windows above
> 4gigs, and this present a problem.
> 
> During initialization of the IOMMU tables, the last entry at each 4GB
> boundary is marked as used.  Thus no mappings can cross the boundary.
> If a table ends at a 4GB boundary, the entry is not marked as used.
> 
> A boot option to remove this 4GB protection is given w/ protect4gb=off.
> This exposes the potential issue for driver and hardware development
> purposes.
> 
> Signed-off-by: Jake Moilanen <moilanen@austin.ibm.com>

Acked-by: Olof Johansson <olof@lixom.net>


-Olof