2fd0c8e7ca
The KPI allows to map very large contigous physical memory regions into KVA, which are not covered by DMAP. I see both with QEMU and with some real hardware started shipping, the regions for NVDIMMs might be very far apart from the normal RAM, and we expect that at least initial users of NVDIMM could install very large amount of such memory. IMO it is not reasonable to extend DMAP to cover that far-away regions both because it could overflow existing 4T window for DMAP in KVA, and because it costs in page table pages allocations, for gap and for possibly unused NV RAM. Also, KPI provides some special functionality for fast cache flushing based on the knowledge of the NVRAM mapping use. Reviewed by: alc, markj Sponsored by: The FreeBSD Foundation Approved by: re (gjb) MFC after: 1 week Differential revision: https://reviews.freebsd.org/D17070
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