MIPS R4000 Microprocessor User's Manual 79
Memory Management
64-bit Kernel Mode, Kernel Space (xkseg)
In Kernel mode, when KX = 1 in the Status register and bits 63:62 of the 64-
bit virtual address are 11
2
, the address space selected is one of the
following:
• kernel virtual space, xkseg, the current kernel virtual space; the
virtual address is extended with the contents of the 8-bit ASID
field to form a unique virtual address
• one of the four 32-bit kernel compatibility spaces, as described
in the next section.
64-bit Kernel Mode, Compatibility Spaces (ckseg1:0, cksseg, ckseg3)
In Kernel mode, when KX = 1 in the Status register, bits 63:62 of the 64-bit
virtual address are 11
2
, and bits 61:31 of the virtual address equal –1, the
lower two bytes of address, as shown in Figure 4-6, select one of the
following 512-Mbyte compatibility spaces.
• ckseg0. This 64-bit virtual address space is an unmapped
region, compatible with the 32-bit address model kseg0. The K0
field of the Config register, described in this chapter, controls
cacheability and coherency.
• ckseg1. This 64-bit virtual address space is an unmapped and
uncached region, compatible with the 32-bit address model
kseg1.
• cksseg. This 64-bit virtual address space is the current
supervisor virtual space, compatible with the 32-bit address
model ksseg.
• ckseg3. This 64-bit virtual address space is kernel virtual space,
compatible with the 32-bit address model kseg3.
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