On Fri, Apr 03, 2026 at 12:35:45PM -0700, Dan Williams wrote: > > + /* > > + * CXL device memory is RAM, not MMIO. Use memremap() rather than > > Right, CXL.mem is RAM, not MMIO, so I question why is this not being > mapped via a RAM mechanism? Can you explain a bit more about why reusing > vfio MMIO mapping mechanisms is suitable here and what happens when we > get to questions like guest_memfd integration, page conversions, and > large page mapping support?
None of that is applicable to VFIO. VFIO owns the entire address space and does not share it with the mm or anything else. > Maybe this is the start of the conversation for something simple, but I > would actually prefer uncached ioremap() if only to avoid all the > coherence management and suitability of MMIO mechanisms questions. The entire thing needs to be mmapable in a cache coherent way since that is what the HW semantic is. If you try to do something else you will break KVM support since it follows the VMA. Jason
