MI386.H

The public symbol file NTKRPAMP.PDB for the original release of Windows 10 tells that the kernel is built with the MI386.H header at

d:\th\minkernel\ntos\mm\i386

and draws from it the following type definitions:

Line Number	Type
835	struct _MMPTE_SOFTWARE
847	struct _MMPTE_TIMESTAMP
860	struct _MMPTE_TRANSITION
873	struct _MMPTE_PROTOTYPE
886	struct _MMPTE_SUBSECTION
895	struct _MMPTE_LIST
919	struct _MMPTE_HIGHLOW
928	struct _MMPTE_HARDWARE
997	struct _MMPTE
998	unnamed union for u in _MMPTE
1161	struct _PAE_PAGEINFO
1167	struct _PAE_ENTRY

The header MI386.H is not known in any Device Driver Kit (DDK) or Windows Driver Kit (WDK).