arch/s390/include/asm/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_pxds;
  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_pxds = 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_pxds < TLB_NR_PTRS))
  66                 __tlb_flush_mm(tlb->mm);
  67         while (tlb->nr_ptes > 0)
  68                 pte_free(tlb->mm, tlb->array[--tlb->nr_ptes]);
  69         while (tlb->nr_pxds < TLB_NR_PTRS)
  70                 /* pgd_free frees the pointer as region or segment table */
  71                 pgd_free(tlb->mm, tlb->array[tlb->nr_pxds++]);
  72 }
  73
  74 static inline void tlb_finish_mmu(struct mmu_gather *tlb,
  75                                   unsigned long start, unsigned long end)
  76 {
  77         tlb_flush_mmu(tlb, start, end);
  78
  79         /* keep the page table cache within bounds */
  80         check_pgt_cache();
  81
  82         put_cpu_var(mmu_gathers);
  83 }
  84
  85 /*
  86  * Release the page cache reference for a pte removed by
  87  * tlb_ptep_clear_flush. In both flush modes the tlb fo a page cache page
  88  * has already been freed, so just do free_page_and_swap_cache.
  89  */
  90 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
  91 {
  92         free_page_and_swap_cache(page);
  93 }
  94
  95 /*
  96  * pte_free_tlb frees a pte table and clears the CRSTE for the
  97  * page table from the tlb.
  98  */
  99 static inline void pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte,
 100                                 unsigned long address)
 101 {
 102         if (!tlb->fullmm) {
 103                 tlb->array[tlb->nr_ptes++] = pte;
 104                 if (tlb->nr_ptes >= tlb->nr_pxds)
 105                         tlb_flush_mmu(tlb, 0, 0);
 106         } else
 107                 pte_free(tlb->mm, pte);
 108 }
 109
 110 /*
 111  * pmd_free_tlb frees a pmd table and clears the CRSTE for the
 112  * segment table entry from the tlb.
 113  * If the mm uses a two level page table the single pmd is freed
 114  * as the pgd. pmd_free_tlb checks the asce_limit against 2GB
 115  * to avoid the double free of the pmd in this case.
 116  */
 117 static inline void pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd,
 118                                 unsigned long address)
 119 {
 120 #ifdef __s390x__
 121         if (tlb->mm->context.asce_limit <= (1UL << 31))
 122                 return;
 123         if (!tlb->fullmm) {
 124                 tlb->array[--tlb->nr_pxds] = pmd;
 125                 if (tlb->nr_ptes >= tlb->nr_pxds)
 126                         tlb_flush_mmu(tlb, 0, 0);
 127         } else
 128                 pmd_free(tlb->mm, pmd);
 129 #endif
 130 }
 131
 132 /*
 133  * pud_free_tlb frees a pud table and clears the CRSTE for the
 134  * region third table entry from the tlb.
 135  * If the mm uses a three level page table the single pud is freed
 136  * as the pgd. pud_free_tlb checks the asce_limit against 4TB
 137  * to avoid the double free of the pud in this case.
 138  */
 139 static inline void pud_free_tlb(struct mmu_gather *tlb, pud_t *pud,
 140                                 unsigned long address)
 141 {
 142 #ifdef __s390x__
 143         if (tlb->mm->context.asce_limit <= (1UL << 42))
 144                 return;
 145         if (!tlb->fullmm) {
 146                 tlb->array[--tlb->nr_pxds] = pud;
 147                 if (tlb->nr_ptes >= tlb->nr_pxds)
 148                         tlb_flush_mmu(tlb, 0, 0);
 149         } else
 150                 pud_free(tlb->mm, pud);
 151 #endif
 152 }
 153
 154 #define tlb_start_vma(tlb, vma)                 do { } while (0)
 155 #define tlb_end_vma(tlb, vma)                   do { } while (0)
 156 #define tlb_remove_tlb_entry(tlb, ptep, addr)   do { } while (0)
 157 #define tlb_migrate_finish(mm)                  do { } while (0)
 158
 159 #endif /* _S390_TLB_H */