Message-ID: <476AD84E.4000507@opengridcomputing.com>
Date: Thu, 20 Dec 2007 15:02:06 -0600
From: Steve Wise <swise@opengridcomputing.com>
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To: benh@au1.ibm.com
CC: Roland Dreier <rdreier@cisco.com>, linux-kernel@vger.kernel.org,
       OpenFabrics General <general@lists.openfabrics.org>,
       Benjamin Herrenschmidt <bherren@au1.ibm.com>,
       Wen Xiong <wenxiong@us.ibm.com>, Olof Johansson <olof@lixom.net>,
       Paul Mackerras <pmac@au1.ibm.com>
Subject: Re: iommu dma mapping alignment requirements
References: <476AA2E2.5010007@opengridcomputing.com> <1198181862.6779.3.camel@pasglop>
In-Reply-To: <1198181862.6779.3.camel@pasglop>
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Benjamin Herrenschmidt wrote:
> Adding A few more people to the discussion. You may well be right and we
> would have to provide the same alignment, though that sucks a bit as one
> of the reason we switched to 4K for the IOMMU is that the iommu space
> available on pSeries is very small and we were running out of it with
> 64K pages and lots of networking activity.
> 

But smarter NIC drivers can resolve this too, I think, but perhaps 
carving up full pages of mapped buffers instead of just assuming mapping 
is free...

perhaps...
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