Re: [Intel IOMMU][patch 8/8] Preserve some Virtual Address when devicescannot address entire range.

From: H. Peter Anvin
Date: Tue Apr 24 2007 - 21:13:30 EST

Andi Kleen wrote:
On Tuesday 24 April 2007 23:50:26 David Miller wrote:
From: Ashok Raj <ashok.raj@xxxxxxxxx>
Date: Tue, 24 Apr 2007 14:38:35 -0700

Its not clear if we have a very generic device breakage.. most devices
on these platforms are going to be more recent, (except maybe some
legacy fd)...
I'm not so sure, there are some "modern" sound cards that have
a 31-bit DMA addressing limitation because they use the 31st
bit as a status bit in their DMA descriptors :-)

There's also a 2GB only megaraid RAID controller that's pretty popular because Dell shipped it for a long time.

You can probably find almost any possible bitmask if you look long enough. Hardware vendors are notorious for this kind of "optimizations".

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