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CHAPTER 5 MEMORY MANAGEMENT SYSTEM
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(8) xkphys (64-bit Kernel mode, physical spaces)
When the KX = 1 in the Status register and bits 63 and 62 of the virtual address space are 10, the virtual
address space is called xkphys and selected as either cached or uncached. If any of bits 58 to 32 of the
address is 1, an attempt to access that address results in an address error.
Whether cache can be used or not is determined by bits 59 to 61 of the virtual address. Table 5-5 shows
cacheability corresponding to 8 address spaces.
Table 5-5. Cacheability and the xkphys Address Space
Bits 61-59
Cacheability
Start address
0
Cached
0x8000 0000 0000 0000
to
0x8000 0000 FFFF FFFF
1
Cached
0x8800 0000 0000 0000
to
0x8800 0000 FFFF FFFF
2
Uncached
0x9000 0000 0000 0000
to
0x9000 0000 FFFF FFFF
3
Cached
0x9800 0000 0000 0000
to
0x9800 0000 FFFF FFFF
4
Cached
0xA000 0000 0000 0000
to
0xA000 0000 FFFF FFFF
5
Cached
0xA800 0000 0000 0000
to
0xA800 0000 FFFF FFFF
6
Cached
0xB000 0000 0000 0000
to
0xB000 0000 FFFF FFFF
7
Cached
0xB800 0000 0000 0000
to
0xB800 0000 FFFF FFFF
(9) xkseg (64-bit Kernel mode, physical spaces)
When the KX = 1 in the Status register and bits 63 and 62 of the virtual address space are 11, the virtual
address space is called xkseg and selected as either 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
References to xkseg are mapped through TLB. Whether cache can be used or not is determined by bit C of
each page’s TLB entry.
one of the four 32-bit kernel compatibility spaces, as described in the next section.