typedef struct _MMVAD
{
     ULONG u1;
     PMMVAD LeftChild;
     PMMVAD RightChild;
     ULONG StartingVpn;
     ULONG EndingVpn;
     ULONG u;
     EX_PUSH_LOCK PushLock;
     ULONG u5;
     ULONG u2;
     union
     {
          PSUBSECTION Subsection;
          PMSUBSECTION MappedSubsection;
     };
     PMMPTE FirstPrototypePte;
     PMMPTE LastContiguousPte;
} MMVAD, *PMMVAD;

Windows Vista Kernel Structures