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To: David Miller <davem@davemloft.net>
Cc: ak@suse.de, ashok.raj@intel.com, linux-kernel@vger.kernel.org,
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       shaohua.li@intel.com
Subject: Re: [Intel IOMMU][patch 8/8] Preserve some Virtual Address when devices cannot address entire range.
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From: Roland Dreier <rdreier@cisco.com>
Date: Tue, 24 Apr 2007 14:32:42 -0700
In-Reply-To: <20070424.142351.62664098.davem@davemloft.net> (David Miller's message of "Tue, 24 Apr 2007 14:23:51 -0700 (PDT)")
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 > My suggestion would be to allocate top-down in the 32-bit IOMMU space.

I think that's good for normal things, but it's not unreasonable to
want to map > 4 GB of memory at once for an Infiniband device.

So maybe we would want some heuristics about the size of the mapping
being requested or the amount of 32-bit space left to decide whether a
mapping should be below 4 GB.

 - R.