[Qemu-devel] [RFC 0/13] Support for guest visible IOMMUs

[David Gibson]

Here is the latest update of my series of patches adding
infrastructure to allow the emulation of guest visible IOMMUs.  I
think this is conceptually ready to go, but I'm sending it as an RFC
for now because it needs a bit more testing and review, particularly
of the invalidation paths.  I believe the first two preliminary
patches are already on their way invia the USB tree.

The big change since the last version is improved handling of IOMMU
invalidations versus dma_memory_map():

It's no longer necessary to have a "cancel" callback which must
synchronously cancel any current usage of a dma_memory_map() buffer.
Instead, we delay the completion of invalidate operations until
outstanding maps are gone.  Later patches do add a cancel callback to
accelerate that freeing up, but it no longer has the potentially
tricky to accomplish synchronous requirements.

I'm really hoping I can get some extra review of this code path.  I
believe it's correct, but it's not straightforward to test, since it
will not be exercise by correct guest software.

There are also some more minor updates based on the previous round of
feedback.