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tlb.h
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1 #ifndef _S390_TLB_H
2 #define _S390_TLB_H
3 
4 /*
5  * TLB flushing on s390 is complicated. The following requirement
6  * from the principles of operation is the most arduous:
7  *
8  * "A valid table entry must not be changed while it is attached
9  * to any CPU and may be used for translation by that CPU except to
10  * (1) invalidate the entry by using INVALIDATE PAGE TABLE ENTRY,
11  * or INVALIDATE DAT TABLE ENTRY, (2) alter bits 56-63 of a page
12  * table entry, or (3) make a change by means of a COMPARE AND SWAP
13  * AND PURGE instruction that purges the TLB."
14  *
15  * The modification of a pte of an active mm struct therefore is
16  * a two step process: i) invalidate the pte, ii) store the new pte.
17  * This is true for the page protection bit as well.
18  * The only possible optimization is to flush at the beginning of
19  * a tlb_gather_mmu cycle if the mm_struct is currently not in use.
20  *
21  * Pages used for the page tables is a different story. FIXME: more
22  */
23 
24 #include <linux/mm.h>
25 #include <linux/pagemap.h>
26 #include <linux/swap.h>
27 #include <asm/processor.h>
28 #include <asm/pgalloc.h>
29 #include <asm/tlbflush.h>
30 
31 struct mmu_gather {
32  struct mm_struct *mm;
34  unsigned int fullmm;
35 };
36 
38  struct rcu_head rcu;
39  unsigned int nr;
40  void *tables[0];
41 };
42 
43 #define MAX_TABLE_BATCH \
44  ((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))
45 
46 extern void tlb_table_flush(struct mmu_gather *tlb);
47 extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
48 
49 static inline void tlb_gather_mmu(struct mmu_gather *tlb,
50  struct mm_struct *mm,
51  unsigned int full_mm_flush)
52 {
53  tlb->mm = mm;
54  tlb->fullmm = full_mm_flush;
55  tlb->batch = NULL;
56  if (tlb->fullmm)
57  __tlb_flush_mm(mm);
58 }
59 
60 static inline void tlb_flush_mmu(struct mmu_gather *tlb)
61 {
62  tlb_table_flush(tlb);
63 }
64 
65 static inline void tlb_finish_mmu(struct mmu_gather *tlb,
66  unsigned long start, unsigned long end)
67 {
68  tlb_table_flush(tlb);
69 }
70 
71 /*
72  * Release the page cache reference for a pte removed by
73  * tlb_ptep_clear_flush. In both flush modes the tlb for a page cache page
74  * has already been freed, so just do free_page_and_swap_cache.
75  */
76 static inline int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
77 {
79  return 1; /* avoid calling tlb_flush_mmu */
80 }
81 
82 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
83 {
85 }
86 
87 /*
88  * pte_free_tlb frees a pte table and clears the CRSTE for the
89  * page table from the tlb.
90  */
91 static inline void pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte,
92  unsigned long address)
93 {
94  if (!tlb->fullmm)
95  return page_table_free_rcu(tlb, (unsigned long *) pte);
96  page_table_free(tlb->mm, (unsigned long *) pte);
97 }
98 
99 /*
100  * pmd_free_tlb frees a pmd table and clears the CRSTE for the
101  * segment table entry from the tlb.
102  * If the mm uses a two level page table the single pmd is freed
103  * as the pgd. pmd_free_tlb checks the asce_limit against 2GB
104  * to avoid the double free of the pmd in this case.
105  */
106 static inline void pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd,
107  unsigned long address)
108 {
109 #ifdef CONFIG_64BIT
110  if (tlb->mm->context.asce_limit <= (1UL << 31))
111  return;
112  if (!tlb->fullmm)
113  return tlb_remove_table(tlb, pmd);
114  crst_table_free(tlb->mm, (unsigned long *) pmd);
115 #endif
116 }
117 
118 /*
119  * pud_free_tlb frees a pud table and clears the CRSTE for the
120  * region third table entry from the tlb.
121  * If the mm uses a three level page table the single pud is freed
122  * as the pgd. pud_free_tlb checks the asce_limit against 4TB
123  * to avoid the double free of the pud in this case.
124  */
125 static inline void pud_free_tlb(struct mmu_gather *tlb, pud_t *pud,
126  unsigned long address)
127 {
128 #ifdef CONFIG_64BIT
129  if (tlb->mm->context.asce_limit <= (1UL << 42))
130  return;
131  if (!tlb->fullmm)
132  return tlb_remove_table(tlb, pud);
133  crst_table_free(tlb->mm, (unsigned long *) pud);
134 #endif
135 }
136 
137 #define tlb_start_vma(tlb, vma) do { } while (0)
138 #define tlb_end_vma(tlb, vma) do { } while (0)
139 #define tlb_remove_tlb_entry(tlb, ptep, addr) do { } while (0)
140 #define tlb_remove_pmd_tlb_entry(tlb, pmdp, addr) do { } while (0)
141 #define tlb_migrate_finish(mm) do { } while (0)
142 
143 #endif /* _S390_TLB_H */