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So we want a strict cacheable mapping even if there is > no user/VMM mapping alias. Is it because KVM cannot do cache maintenance > on the PFNMAP or because the device does not support other memory types? > Both valid reasons though. Lack of cache maintenance is the main problem for the vfio-grace device > In this case KVM still needs to know the properties of the device. Not > sure how it could best do this without a vma. Well, the idea I hope to succeed with would annotate this kind of information inside the page list that would be exchanged through the FD. There is an monstrous thread here about this topic: https://lore.kernel.org/all/20250107142719.179636-1-yilun.xu@linux.intel.com/ I can't find it in the huge thread but I did explain some thoughts on how it could work Jason