typedef struct _MMPFN
{
     ULONG u1;
     ULONG u2;
     union
     {
          PMMPTE PteAddress;
          PVOID VolatilePteAddress;
     };
     ULONG u3;
     union
     {
          MMPTE OriginalPte;
          LONG AweReferenceCount;
     };
     ULONG u4;
} MMPFN, *PMMPFN;

Windows Vista Kernel Structures