On Fri, Feb 21, 2025 at 03:39:45PM +0000, Robin Murphy wrote:

Yuck. Realistically we are going to have no more than two different
implementations of this; a fiddly callback interface seems overkill. All we
should need in the domain is a simple indicator of *which* MSI translation
scheme is in use (if it can't be squeezed into the domain type itself), then
iommu_dma_prepare_msi() can simply dispatch between iommu-dma and IOMMUFD
based on that, and then it's easy to solve all the other fragility issues
too.

That would make module dependency problems, we have so far avoided
having the core kernel hard depend on iommufd.

Jason