linux-phytec-ti

iommu/vt-d: Handle Caching Mode implementations of SVM

Not entirely clear why, but it seems we need to reserve PASID zero and
flush it when we make a PASID entry present.

Quite we we couldn't use the true PASID value, isn't clear.

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