The public symbol file NTKRPAMP.PDB for the original release of Windows 10 tells that the kernel is built with the CM_X.H header at


and draws from it the following type definition:

Line Number Type Remarks
46 enum _REG_NOTIFY_CLASS line 24207 in WDM.H;
line 22172 in NTOSP.H

The header CM_X.H is not known in any Device Driver Kit (DDK) or Windows Driver Kit (WDK).