What is Persistent Memory Region?

NVM Express Base Specification Features

Persistent Memory Region (PMR) is an optinal area of persistent memory that is located on the NVMe device, that can be read with standard PCIe memory reads/writes. This could be extra DRAM that is power protected, storage class memory or other new memory types. The use cases are not defined by the NVMe specification, but there are many useful needs for a general purpose PMR.