On Sat, Jun 18, 2022 at 11:18:17PM -0700, Christoph Hellwig wrote: > > > There is a bunch of code an comments in the iommu type1 code that > > > suggest we can pin memory that is not page backed. > > > > Would you mind explaining the use case for pinning memory that > > isn't page backed? And do we have such use case so far? > > Sorry, I should have deleted that sentence. I wrote it before spending > some more time to dig through the code and all the locked memory has > page backing. There just seem to be a lot of checks left inbetween > if a pfn is page backed, mostly due to the pfn based calling convetions. OK. We'd be safe to move on then. Thanks for the clarification. > > I can do that. I tried once, but there were just too much changes > > inside type1 code that felt like a chain reaction. If we plan to > > eventually replace with IOMMUFD implementations, these changes in > > type1 might not be necessary, I thought. > > To make sure we keep full compatibility I suspect the final iommufd > implementation has to be gradutally created from the existing code > anyway. Hmm. I think Jason can give some insight. Meanwhile, I will try to add a patch to type1 code, in case we'd end up with what you suspected.
