arch/powerpc/mm/mmu_context_book3s64.c

   1 /*
   2  *  MMU context allocation for 64-bit kernels.
   3  *
   4  *  Copyright (C) 2004 Anton Blanchard, IBM Corp. <anton@samba.org>
   5  *
   6  *  This program is free software; you can redistribute it and/or
   7  *  modify it under the terms of the GNU General Public License
   8  *  as published by the Free Software Foundation; either version
   9  *  2 of the License, or (at your option) any later version.
  10  *
  11  */
  12
  13 #include <linux/sched.h>
  14 #include <linux/kernel.h>
  15 #include <linux/errno.h>
  16 #include <linux/string.h>
  17 #include <linux/types.h>
  18 #include <linux/mm.h>
  19 #include <linux/spinlock.h>
  20 #include <linux/idr.h>
  21 #include <linux/export.h>
  22 #include <linux/gfp.h>
  23 #include <linux/slab.h>
  24
  25 #include <asm/mmu_context.h>
  26 #include <asm/pgalloc.h>
  27
  28 static DEFINE_SPINLOCK(mmu_context_lock);
  29 static DEFINE_IDA(mmu_context_ida);
  30
  31 static int alloc_context_id(int min_id, int max_id)
  32 {
  33         int index, err;
  34
  35 again:
  36         if (!ida_pre_get(&mmu_context_ida, GFP_KERNEL))
  37                 return -ENOMEM;
  38
  39         spin_lock(&mmu_context_lock);
  40         err = ida_get_new_above(&mmu_context_ida, min_id, &index);
  41         spin_unlock(&mmu_context_lock);
  42
  43         if (err == -EAGAIN)
  44                 goto again;
  45         else if (err)
  46                 return err;
  47
  48         if (index > max_id) {
  49                 spin_lock(&mmu_context_lock);
  50                 ida_remove(&mmu_context_ida, index);
  51                 spin_unlock(&mmu_context_lock);
  52                 return -ENOMEM;
  53         }
  54
  55         return index;
  56 }
  57
  58 void hash__reserve_context_id(int id)
  59 {
  60         int rc, result = 0;
  61
  62         do {
  63                 if (!ida_pre_get(&mmu_context_ida, GFP_KERNEL))
  64                         break;
  65
  66                 spin_lock(&mmu_context_lock);
  67                 rc = ida_get_new_above(&mmu_context_ida, id, &result);
  68                 spin_unlock(&mmu_context_lock);
  69         } while (rc == -EAGAIN);
  70
  71         WARN(result != id, "mmu: Failed to reserve context id %d (rc %d)\n", id, result);
  72 }
  73
  74 int hash__alloc_context_id(void)
  75 {
  76         unsigned long max;
  77
  78         if (mmu_has_feature(MMU_FTR_68_BIT_VA))
  79                 max = MAX_USER_CONTEXT;
  80         else
  81                 max = MAX_USER_CONTEXT_65BIT_VA;
  82
  83         return alloc_context_id(MIN_USER_CONTEXT, max);
  84 }
  85 EXPORT_SYMBOL_GPL(hash__alloc_context_id);
  86
  87 static int hash__init_new_context(struct mm_struct *mm)
  88 {
  89         int index;
  90
  91         index = hash__alloc_context_id();
  92         if (index < 0)
  93                 return index;
  94
  95         /*
  96          * We do switch_slb() early in fork, even before we setup the
  97          * mm->context.addr_limit. Default to max task size so that we copy the
  98          * default values to paca which will help us to handle slb miss early.
  99          */
 100         mm->context.addr_limit = DEFAULT_MAP_WINDOW_USER64;
 101
 102         /*
 103          * The old code would re-promote on fork, we don't do that when using
 104          * slices as it could cause problem promoting slices that have been
 105          * forced down to 4K.
 106          *
 107          * For book3s we have MMU_NO_CONTEXT set to be ~0. Hence check
 108          * explicitly against context.id == 0. This ensures that we properly
 109          * initialize context slice details for newly allocated mm's (which will
 110          * have id == 0) and don't alter context slice inherited via fork (which
 111          * will have id != 0).
 112          *
 113          * We should not be calling init_new_context() on init_mm. Hence a
 114          * check against 0 is OK.
 115          */
 116         if (mm->context.id == 0)
 117                 slice_set_user_psize(mm, mmu_virtual_psize);
 118
 119         subpage_prot_init_new_context(mm);
 120
 121         return index;
 122 }
 123
 124 static int radix__init_new_context(struct mm_struct *mm)
 125 {
 126         unsigned long rts_field;
 127         int index, max_id;
 128
 129         max_id = (1 << mmu_pid_bits) - 1;
 130         index = alloc_context_id(mmu_base_pid, max_id);
 131         if (index < 0)
 132                 return index;
 133
 134         /*
 135          * set the process table entry,
 136          */
 137         rts_field = radix__get_tree_size();
 138         process_tb[index].prtb0 = cpu_to_be64(rts_field | __pa(mm->pgd) | RADIX_PGD_INDEX_SIZE);
 139
 140         /*
 141          * Order the above store with subsequent update of the PID
 142          * register (at which point HW can start loading/caching
 143          * the entry) and the corresponding load by the MMU from
 144          * the L2 cache.
 145          */
 146         asm volatile("ptesync;isync" : : : "memory");
 147
 148         mm->context.npu_context = NULL;
 149
 150         return index;
 151 }
 152
 153 int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 154 {
 155         int index;
 156
 157         if (radix_enabled())
 158                 index = radix__init_new_context(mm);
 159         else
 160                 index = hash__init_new_context(mm);
 161
 162         if (index < 0)
 163                 return index;
 164
 165         mm->context.id = index;
 166
 167 #ifdef CONFIG_PPC_64K_PAGES
 168         mm->context.pte_frag = NULL;
 169 #endif
 170 #ifdef CONFIG_SPAPR_TCE_IOMMU
 171         mm_iommu_init(mm);
 172 #endif
 173         atomic_set(&mm->context.active_cpus, 0);
 174
 175         return 0;
 176 }
 177
 178 void __destroy_context(int context_id)
 179 {
 180         spin_lock(&mmu_context_lock);
 181         ida_remove(&mmu_context_ida, context_id);
 182         spin_unlock(&mmu_context_lock);
 183 }
 184 EXPORT_SYMBOL_GPL(__destroy_context);
 185
 186 #ifdef CONFIG_PPC_64K_PAGES
 187 static void destroy_pagetable_page(struct mm_struct *mm)
 188 {
 189         int count;
 190         void *pte_frag;
 191         struct page *page;
 192
 193         pte_frag = mm->context.pte_frag;
 194         if (!pte_frag)
 195                 return;
 196
 197         page = virt_to_page(pte_frag);
 198         /* drop all the pending references */
 199         count = ((unsigned long)pte_frag & ~PAGE_MASK) >> PTE_FRAG_SIZE_SHIFT;
 200         /* We allow PTE_FRAG_NR fragments from a PTE page */
 201         if (page_ref_sub_and_test(page, PTE_FRAG_NR - count)) {
 202                 pgtable_page_dtor(page);
 203                 free_hot_cold_page(page, 0);
 204         }
 205 }
 206
 207 #else
 208 static inline void destroy_pagetable_page(struct mm_struct *mm)
 209 {
 210         return;
 211 }
 212 #endif
 213
 214 void destroy_context(struct mm_struct *mm)
 215 {
 216 #ifdef CONFIG_SPAPR_TCE_IOMMU
 217         WARN_ON_ONCE(!list_empty(&mm->context.iommu_group_mem_list));
 218 #endif
 219         if (radix_enabled()) {
 220                 /*
 221                  * Radix doesn't have a valid bit in the process table
 222                  * entries. However we know that at least P9 implementation
 223                  * will avoid caching an entry with an invalid RTS field,
 224                  * and 0 is invalid. So this will do.
 225                  */
 226                 process_tb[mm->context.id].prtb0 = 0;
 227         } else
 228                 subpage_prot_free(mm);
 229         destroy_pagetable_page(mm);
 230         __destroy_context(mm->context.id);
 231         mm->context.id = MMU_NO_CONTEXT;
 232 }
 233
 234 #ifdef CONFIG_PPC_RADIX_MMU
 235 void radix__switch_mmu_context(struct mm_struct *prev, struct mm_struct *next)
 236 {
 237
 238         if (cpu_has_feature(CPU_FTR_POWER9_DD1)) {
 239                 isync();
 240                 mtspr(SPRN_PID, next->context.id);
 241                 isync();
 242                 asm volatile(PPC_INVALIDATE_ERAT : : :"memory");
 243         } else {
 244                 mtspr(SPRN_PID, next->context.id);
 245                 isync();
 246         }
 247 }
 248 #endif