iommu/vt-d: Be less pessimistic about domain coherency where possible

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In commit 2e12bc29 ("intel-iommu: Default to non-coherent for domains
unattached to iommus") we decided to err on the side of caution and
always assume that it's possible that a device will be attached which is
behind a non-coherent IOMMU.

In some cases, however, that just *cannot* happen. If there *are* no
IOMMUs in the system which are non-coherent, then we don't need to do
it. And flushing the dcache is a *significant* performance hit.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

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David Woodhouse 2014-03-11 17:10:29 -07:00 • committed by David Woodhouse

parent 214e39aa36

commit d050196087

1 changed files with 17 additions and 4 deletions

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drivers/iommu/intel-iommu.c

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