Re: [PATCH 01/34] AMD IOMMU: add Kconfig entry

[Muli Ben-Yehuda]

On Fri, Jun 27, 2008 at 03:39:31PM -0500, Duran, Leo wrote:

> 2) IOMMU will not translate if the exclusion range has been enabled, and
> the DMA address falls inside that range.
> The exclusion range can be enabled for specific devices, or for all
> devices... Enabling the exclusion range can be considered a 'performance
> optimization' (no table-walks), with the caveat of not being able to
> provide protection for devices sharing the exclusion range (BTW, there's
> a single exclusion address range per IOMMU).

So, if I understand this correctly, could we implement Joerg's
"almost-direct-map" by having 0-64MB translated for host-owned
devices, and then 64MB-end excluded (again, for host-owned devices
only)? If yes, it should provide a small boost in performance (may or
may not be measurable) over having 64MB-end be an identity
translation.

Cheers,
Muli
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