On Wed, Aug 30, 2023 at 06:50:32AM -0700, Christoph Hellwig wrote: > I know I'm chiming in a bit late, but what ultimate user space is going > to use this? We should not add anything to the kernel that can't > be used without fully open user space. qemu will get the matching VFIO userspace patches, I think they were posted someplace already. > vfio has traditionally been a bit special as it "just" passes devices > through, so any user space could just be a user space driver for a > random device on $FOO bus, including an actual Linux driver in a VM, > but this driver has very specific semantics for a very specific piece > of hardware, so it really needs to be treated like a generic GPU driver > or accelerator driver. This is basically a pre-CXL driver. It takes a PCI device and some non-standard CXL-ish metadata and adapts it to VFIO. In a post-CXL world this same functionality of managing the 'cache coherent BAR' for VFIO would be done generically by some generic vfio-cxl driver. Jason
