On Sun, Jun 19, 2022 at 10:51:47PM -0700, Christoph Hellwig wrote: > On Mon, Jun 20, 2022 at 12:00:46AM -0300, Jason Gunthorpe wrote: > > On Fri, Jun 17, 2022 at 01:54:05AM -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. > > > > AFAIK you can.. The whole follow_pte() mechanism allows raw PFNs to be > > loaded into the type1 maps and the pin API will happily return > > them. This happens in almost every qemu scenario because PCI MMIO BAR > > memory ends up routed down this path. > > Indeed, my read wasn't deep enough. Which means that we can't change > the ->pin_pages interface to return a struct pages array, as we don't > have one for those. Actually. gvt requires a struct page, and both s390 seem to require normal non-I/O, non-remapped kernel pointers. So I think for the vfio_pin_pages we can assume that we only want page backed memory and remove the follow_fault_pfn case entirely. But we'll probably have to keep it for the vfio_iommu_replay case that is not tied to emulated IOMMU drivers.
