struct DBGKD_READ_WRITE_IO_EXTENDED64

typedef struct _DBGKD_READ_WRITE_IO_EXTENDED64
{
     ULONG DataSize;
     ULONG InterfaceType;
     ULONG BusNumber;
     ULONG AddressSpace;
     UINT64 IoAddress;
     ULONG DataValue;
} DBGKD_READ_WRITE_IO_EXTENDED64, *PDBGKD_READ_WRITE_IO_EXTENDED64;

Windows Vista Kernel Structures