include/asm-s390/tlb.h

   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/swap.h>
  26 #include <asm/processor.h>
  27 #include <asm/pgalloc.h>
  28 #include <asm/smp.h>
  29 #include <asm/tlbflush.h>
  30
  31 #ifndef CONFIG_SMP
  32 #define TLB_NR_PTRS     1
  33 #else
  34 #define TLB_NR_PTRS     508
  35 #endif
  36
  37 struct mmu_gather {
  38         struct mm_struct *mm;
  39         unsigned int fullmm;
  40         unsigned int nr_ptes;
  41         unsigned int nr_pmds;
  42         void *array[TLB_NR_PTRS];
  43 };
  44
  45 DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
  46
  47 static inline struct mmu_gather *tlb_gather_mmu(struct mm_struct *mm,
  48                                                 unsigned int full_mm_flush)
  49 {
  50         struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);
  51
  52         tlb->mm = mm;
  53         tlb->fullmm = full_mm_flush || (num_online_cpus() == 1) ||
  54                 (atomic_read(&mm->mm_users) <= 1 && mm == current->active_mm);
  55         tlb->nr_ptes = 0;
  56         tlb->nr_pmds = TLB_NR_PTRS;
  57         if (tlb->fullmm)
  58                 __tlb_flush_mm(mm);
  59         return tlb;
  60 }
  61
  62 static inline void tlb_flush_mmu(struct mmu_gather *tlb,
  63                                  unsigned long start, unsigned long end)
  64 {
  65         if (!tlb->fullmm && (tlb->nr_ptes > 0 || tlb->nr_pmds < TLB_NR_PTRS))
  66                 __tlb_flush_mm(tlb->mm);
  67         while (tlb->nr_ptes > 0)
  68                 pte_free(tlb->array[--tlb->nr_ptes]);
  69         while (tlb->nr_pmds < TLB_NR_PTRS)
  70                 pmd_free((pmd_t *) tlb->array[tlb->nr_pmds++]);
  71 }
  72
  73 static inline void tlb_finish_mmu(struct mmu_gather *tlb,
  74                                   unsigned long start, unsigned long end)
  75 {
  76         tlb_flush_mmu(tlb, start, end);
  77
  78         /* keep the page table cache within bounds */
  79         check_pgt_cache();
  80
  81         put_cpu_var(mmu_gathers);
  82 }
  83
  84 /*
  85  * Release the page cache reference for a pte removed by
  86  * tlb_ptep_clear_flush. In both flush modes the tlb fo a page cache page
  87  * has already been freed, so just do free_page_and_swap_cache.
  88  */
  89 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
  90 {
  91         free_page_and_swap_cache(page);
  92 }
  93
  94 /*
  95  * pte_free_tlb frees a pte table and clears the CRSTE for the
  96  * page table from the tlb.
  97  */
  98 static inline void pte_free_tlb(struct mmu_gather *tlb, struct page *page)
  99 {
 100         if (!tlb->fullmm) {
 101                 tlb->array[tlb->nr_ptes++] = page;
 102                 if (tlb->nr_ptes >= tlb->nr_pmds)
 103                         tlb_flush_mmu(tlb, 0, 0);
 104         } else
 105                 pte_free(page);
 106 }
 107
 108 /*
 109  * pmd_free_tlb frees a pmd table and clears the CRSTE for the
 110  * segment table entry from the tlb.
 111  */
 112 static inline void pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
 113 {
 114 #ifdef __s390x__
 115         if (!tlb->fullmm) {
 116                 tlb->array[--tlb->nr_pmds] = (struct page *) pmd;
 117                 if (tlb->nr_ptes >= tlb->nr_pmds)
 118                         tlb_flush_mmu(tlb, 0, 0);
 119         } else
 120                 pmd_free(pmd);
 121 #endif
 122 }
 123
 124 #define pud_free_tlb(tlb, pud)                  do { } while (0)
 125
 126 #define tlb_start_vma(tlb, vma)                 do { } while (0)
 127 #define tlb_end_vma(tlb, vma)                   do { } while (0)
 128 #define tlb_remove_tlb_entry(tlb, ptep, addr)   do { } while (0)
 129 #define tlb_migrate_finish(mm)                  do { } while (0)
 130
 131 #endif /* _S390_TLB_H */