typedef enum _MI_SYSTEM_VA_TYPE
{
         MiVaUnused = 0,
         MiVaSessionSpace = 1,
         MiVaProcessSpace = 2,
         MiVaBootLoaded = 3,
         MiVaPfnDatabase = 4,
         MiVaNonPagedPool = 5,
         MiVaPagedPool = 6,
         MiVaSpecialPool = 7,
         MiVaSystemCache = 8,
         MiVaSystemPtes = 9,
         MiVaHal = 10,
         MiVaSessionGlobalSpace = 11,
         MiVaMaximumType = 12
} MI_SYSTEM_VA_TYPE;

Windows Vista Kernel Structures