On Thu, Nov 10, 2011 at 10:35:34PM +0800, cody wrote:

Yes I totally agree page-size is not required for unmap operations
and should not be added as parameter to map/unmap operations. I am
not saying the unmap operation, but the IOTLB flush operation. My
point is we also may also need to add similar logic in IOTLB flush
code (such as in Intel IOMMU dirver) to grantee that when issuing
IOTLB flush command for large page, we will still meet the hardware
limitation of flushing large page. Seems for Intel IOMMU the only
limitation is the mask value (indicating number of 4k-pages) cannot
be smaller than the value to cover large page, and seems current
Intel IOMMU driver code has covered this case well. I am not
familiar with how AMD IOMMU issues IOTLB flush command, it should be
able to handle this large page case too. So at this moment, this
patch should not have any issues :)

The map-operation actually takes a size, as it should. The idea is to
change this function to a map_page interface which takes a page-size
parameter, but thats another story.
The IOTLB flushing is not exposed by the IOMMU-API anyway. To whatever
is necessary to do that, it is the business of the IOMMU driver. So in
the unmap-path the driver finds out the page-size to unmap and can
immediatly flush the IOTLB for that page.


	Joerg

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