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SubjectRe: [PATCH v4 2/7] iommu/core: split mapping to page sizes as supported by the hardware
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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AMD Operating System Research Center

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