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[deliverable/linux.git] / arch / powerpc / include / asm / pte-hash32.h
1 #ifndef _ASM_POWERPC_PTE_HASH32_H
2 #define _ASM_POWERPC_PTE_HASH32_H
3 #ifdef __KERNEL__
4
5 /*
6 * The "classic" 32-bit implementation of the PowerPC MMU uses a hash
7 * table containing PTEs, together with a set of 16 segment registers,
8 * to define the virtual to physical address mapping.
9 *
10 * We use the hash table as an extended TLB, i.e. a cache of currently
11 * active mappings. We maintain a two-level page table tree, much
12 * like that used by the i386, for the sake of the Linux memory
13 * management code. Low-level assembler code in hash_low_32.S
14 * (procedure hash_page) is responsible for extracting ptes from the
15 * tree and putting them into the hash table when necessary, and
16 * updating the accessed and modified bits in the page table tree.
17 */
18
19 #define _PAGE_PRESENT 0x001 /* software: pte contains a translation */
20 #define _PAGE_HASHPTE 0x002 /* hash_page has made an HPTE for this pte */
21 #define _PAGE_FILE 0x004 /* when !present: nonlinear file mapping */
22 #define _PAGE_USER 0x004 /* usermode access allowed */
23 #define _PAGE_GUARDED 0x008 /* G: prohibit speculative access */
24 #define _PAGE_COHERENT 0x010 /* M: enforce memory coherence (SMP systems) */
25 #define _PAGE_NO_CACHE 0x020 /* I: cache inhibit */
26 #define _PAGE_WRITETHRU 0x040 /* W: cache write-through */
27 #define _PAGE_DIRTY 0x080 /* C: page changed */
28 #define _PAGE_ACCESSED 0x100 /* R: page referenced */
29 #define _PAGE_EXEC 0x200 /* software: i-cache coherency required */
30 #define _PAGE_RW 0x400 /* software: user write access allowed */
31 #define _PAGE_SPECIAL 0x800 /* software: Special page */
32
33 #ifdef CONFIG_PTE_64BIT
34 /* We never clear the high word of the pte */
35 #define _PTE_NONE_MASK (0xffffffff00000000ULL | _PAGE_HASHPTE)
36 #else
37 #define _PTE_NONE_MASK _PAGE_HASHPTE
38 #endif
39
40 #define _PMD_PRESENT 0
41 #define _PMD_PRESENT_MASK (PAGE_MASK)
42 #define _PMD_BAD (~PAGE_MASK)
43
44 /* Hash table based platforms need atomic updates of the linux PTE */
45 #define PTE_ATOMIC_UPDATES 1
46
47
48 #endif /* __KERNEL__ */
49 #endif /* _ASM_POWERPC_PTE_HASH32_H */
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