On POWER9, there are entries in /memory@ which are not standard memory
These new memory entries are related to NVLINK and the recommend way to
check if this is a memory region that the OS should use
is parsing 'linux,usable-memory' property instead of 'reg'. In machine AC922, both properties has _different_ values in fact.
If you use these NVlink memory regions as standard memory regions, you
are going to hit a machine check exception (MCE) with DAR
~0xc00003fffffd7000 and dsisr = 0x8000.