IOVA allocation improvements for iommu-dma

Hi all,

Here's the first bit of lock contention removal to chew on - feedback welcome! Note that for the current users of the io-pgtable framework, this is most likely to simply push more contention onto the io-pgtable lock, so may not show a great improvement alone. Will and I both have rough proof-of-concept implementations of lock-free io-pgtable code which we need to sit down and agree on at some point, hopefullt fairly soon.

I've taken the opportunity to do a bit of cleanup and refactoring within the series to make the final state of the code nicer, but the diffstat still turns out surprisingly reasonable in the end - it would actually be negative but for the new comments!

Magnus, Shimoda-san, the first two patches should be of interest as they constitute the allocation rework I mentioned a while back[1] - if you still need to implement that scary workaround, this should make it simple to hook IPMMU-specific calls into the alloc and free paths, and let the driver take care of the details internally.

Robin.

[1]:https://lists.linuxfoundation.org/pipermail/iommu/2017-January/020189.html

Robin Murphy (3):
iommu/dma: Convert to address-based allocation
iommu/dma: Clean up MSI IOVA allocation
iommu/dma: Plumb in the per-CPU IOVA caches

 drivers/iommu/dma-iommu.c | 176 ++++++++++++++++++++++++----------------------
 1 file changed, 90 insertions(+), 86 deletions(-)

2.11.0.dirty