16.2 Virtual Address Space

Address Space Access Privilege Differences Between the R4400 and R1000

• Access to the 64-bit user space in 64-bit Supervisor or Kernel mode (xsuseg or xkuseg) is controlled by the UX bit. If UX=0, the 64-bit Supervisor and Kernel modes can only access the 32-bit user space (suseg or kuseg).
• Access to the 64-bit supervisor space in Kernel mode (xksseg) is controlled by the SX bit. If SX=0, the 64-bit Kernel mode can only access the 32-bit supervisor space (ksseg).

The R10000 processor implements the same access privileges for 32-bit processor modes as in the R4400. The Table 16-2 summarizes the access privileges for all processor modes in the R10000 processor.

Table 16-2 Access Privileges for User, Supervisor and Kernel Mode Operations