Chapter 4
78 MIPS R4000 Microprocessor User's Manual
64-bit Kernel Mode, Current Supervisor Space (xksseg)
In Kernel mode, when KX = 1 in the Status register and bits 63:62 of the 64-
bit virtual address are 01
2
, the xksseg virtual address space is selected; it is
the current supervisor virtual space. The virtual address is extended with
the contents of the 8-bit ASID field to form a unique virtual address.
64-bit Kernel Mode, Physical Spaces (xkphys)
In Kernel mode, when KX = 1 in the Status register and bits 63:62 of the 64-
bit virtual address are 10
2
, the xkphys virtual address space is selected; it is
a set of eight 2
36
-byte kernel physical spaces. Accesses with address bits
58:36 not equal to 0 cause an address error.
References to this space are not mapped; the physical address selected is
taken from bits 35:0 of the virtual address. Bits 61:59 of the virtual address
specify the cacheability and coherency attributes, as shown in Table 4-5.
Table 4-5 Cacheability and Coherency Attributes
Value (61:59) Cacheability and Coherency Attributes Starting Address
0 Reserved 0x8000 0000 0000 0000
1 Reserved 0x8800 0000 0000 0000
2 Uncached 0x9000 0000 0000 0000
3 Cacheable, noncoherent 0x9800 0000 0000 0000
4 Cacheable, coherent exclusive 0xA000 0000 0000 0000
5 Cacheable, coherent exclusive on write 0xA800 0000 0000 0000
6 Cacheable, coherent update on write 0xB000 0000 0000 0000
7 Reserved 0xB800 0000 0000 0000
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