Re: [Intel IOMMU][patch 8/8] Preserve some Virtual Address when devices cannot address entire range.

H. Peter Anvin
2007-04-25T01:13:14Z

Andi Kleen wrote:
> On Tuesday 24 April 2007 23:50:26 David Miller wrote:
>> From: Ashok Raj <ashok.raj@intel.com>
>> 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".

-hpa