arch/x86/mm/pat_rbtree.c

   1 /*
   2  * Handle caching attributes in page tables (PAT)
   3  *
   4  * Authors: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
   5  *          Suresh B Siddha <suresh.b.siddha@intel.com>
   6  *
   7  * Interval tree (augmented rbtree) used to store the PAT memory type
   8  * reservations.
   9  */
  10
  11 #include <linux/seq_file.h>
  12 #include <linux/debugfs.h>
  13 #include <linux/kernel.h>
  14 #include <linux/module.h>
  15 #include <linux/rbtree_augmented.h>
  16 #include <linux/sched.h>
  17 #include <linux/gfp.h>
  18
  19 #include <asm/pgtable.h>
  20 #include <asm/pat.h>
  21
  22 #include "pat_internal.h"
  23
  24 /*
  25  * The memtype tree keeps track of memory type for specific
  26  * physical memory areas. Without proper tracking, conflicting memory
  27  * types in different mappings can cause CPU cache corruption.
  28  *
  29  * The tree is an interval tree (augmented rbtree) with tree ordered
  30  * on starting address. Tree can contain multiple entries for
  31  * different regions which overlap. All the aliases have the same
  32  * cache attributes of course.
  33  *
  34  * memtype_lock protects the rbtree.
  35  */
  36
  37 static struct rb_root memtype_rbroot = RB_ROOT;
  38
  39 static int is_node_overlap(struct memtype *node, u64 start, u64 end)
  40 {
  41         if (node->start >= end || node->end <= start)
  42                 return 0;
  43
  44         return 1;
  45 }
  46
  47 static u64 get_subtree_max_end(struct rb_node *node)
  48 {
  49         u64 ret = 0;
  50         if (node) {
  51                 struct memtype *data = container_of(node, struct memtype, rb);
  52                 ret = data->subtree_max_end;
  53         }
  54         return ret;
  55 }
  56
  57 static u64 compute_subtree_max_end(struct memtype *data)
  58 {
  59         u64 max_end = data->end, child_max_end;
  60
  61         child_max_end = get_subtree_max_end(data->rb.rb_right);
  62         if (child_max_end > max_end)
  63                 max_end = child_max_end;
  64
  65         child_max_end = get_subtree_max_end(data->rb.rb_left);
  66         if (child_max_end > max_end)
  67                 max_end = child_max_end;
  68
  69         return max_end;
  70 }
  71
  72 RB_DECLARE_CALLBACKS(static, memtype_rb_augment_cb, struct memtype, rb,
  73                      u64, subtree_max_end, compute_subtree_max_end)
  74
  75 /* Find the first (lowest start addr) overlapping range from rb tree */
  76 static struct memtype *memtype_rb_lowest_match(struct rb_root *root,
  77                                 u64 start, u64 end)
  78 {
  79         struct rb_node *node = root->rb_node;
  80         struct memtype *last_lower = NULL;
  81
  82         while (node) {
  83                 struct memtype *data = container_of(node, struct memtype, rb);
  84
  85                 if (get_subtree_max_end(node->rb_left) > start) {
  86                         /* Lowest overlap if any must be on left side */
  87                         node = node->rb_left;
  88                 } else if (is_node_overlap(data, start, end)) {
  89                         last_lower = data;
  90                         break;
  91                 } else if (start >= data->start) {
  92                         /* Lowest overlap if any must be on right side */
  93                         node = node->rb_right;
  94                 } else {
  95                         break;
  96                 }
  97         }
  98         return last_lower; /* Returns NULL if there is no overlap */
  99 }
 100
 101 static struct memtype *memtype_rb_exact_match(struct rb_root *root,
 102                                 u64 start, u64 end)
 103 {
 104         struct memtype *match;
 105
 106         match = memtype_rb_lowest_match(root, start, end);
 107         while (match != NULL && match->start < end) {
 108                 struct rb_node *node;
 109
 110                 if (match->start == start && match->end == end)
 111                         return match;
 112
 113                 node = rb_next(&match->rb);
 114                 if (node)
 115                         match = container_of(node, struct memtype, rb);
 116                 else
 117                         match = NULL;
 118         }
 119
 120         return NULL; /* Returns NULL if there is no exact match */
 121 }
 122
 123 static int memtype_rb_check_conflict(struct rb_root *root,
 124                                 u64 start, u64 end,
 125                                 unsigned long reqtype, unsigned long *newtype)
 126 {
 127         struct rb_node *node;
 128         struct memtype *match;
 129         int found_type = reqtype;
 130
 131         match = memtype_rb_lowest_match(&memtype_rbroot, start, end);
 132         if (match == NULL)
 133                 goto success;
 134
 135         if (match->type != found_type && newtype == NULL)
 136                 goto failure;
 137
 138         dprintk("Overlap at 0x%Lx-0x%Lx\n", match->start, match->end);
 139         found_type = match->type;
 140
 141         node = rb_next(&match->rb);
 142         while (node) {
 143                 match = container_of(node, struct memtype, rb);
 144
 145                 if (match->start >= end) /* Checked all possible matches */
 146                         goto success;
 147
 148                 if (is_node_overlap(match, start, end) &&
 149                     match->type != found_type) {
 150                         goto failure;
 151                 }
 152
 153                 node = rb_next(&match->rb);
 154         }
 155 success:
 156         if (newtype)
 157                 *newtype = found_type;
 158
 159         return 0;
 160
 161 failure:
 162         printk(KERN_INFO "%s:%d conflicting memory types "
 163                 "%Lx-%Lx %s<->%s\n", current->comm, current->pid, start,
 164                 end, cattr_name(found_type), cattr_name(match->type));
 165         return -EBUSY;
 166 }
 167
 168 static void memtype_rb_insert(struct rb_root *root, struct memtype *newdata)
 169 {
 170         struct rb_node **node = &(root->rb_node);
 171         struct rb_node *parent = NULL;
 172
 173         while (*node) {
 174                 struct memtype *data = container_of(*node, struct memtype, rb);
 175
 176                 parent = *node;
 177                 if (data->subtree_max_end < newdata->end)
 178                         data->subtree_max_end = newdata->end;
 179                 if (newdata->start <= data->start)
 180                         node = &((*node)->rb_left);
 181                 else if (newdata->start > data->start)
 182                         node = &((*node)->rb_right);
 183         }
 184
 185         newdata->subtree_max_end = newdata->end;
 186         rb_link_node(&newdata->rb, parent, node);
 187         rb_insert_augmented(&newdata->rb, root, &memtype_rb_augment_cb);
 188 }
 189
 190 int rbt_memtype_check_insert(struct memtype *new, unsigned long *ret_type)
 191 {
 192         int err = 0;
 193
 194         err = memtype_rb_check_conflict(&memtype_rbroot, new->start, new->end,
 195                                                 new->type, ret_type);
 196
 197         if (!err) {
 198                 if (ret_type)
 199                         new->type = *ret_type;
 200
 201                 new->subtree_max_end = new->end;
 202                 memtype_rb_insert(&memtype_rbroot, new);
 203         }
 204         return err;
 205 }
 206
 207 struct memtype *rbt_memtype_erase(u64 start, u64 end)
 208 {
 209         struct memtype *data;
 210
 211         data = memtype_rb_exact_match(&memtype_rbroot, start, end);
 212         if (!data)
 213                 goto out;
 214
 215         rb_erase_augmented(&data->rb, &memtype_rbroot, &memtype_rb_augment_cb);
 216 out:
 217         return data;
 218 }
 219
 220 struct memtype *rbt_memtype_lookup(u64 addr)
 221 {
 222         struct memtype *data;
 223         data = memtype_rb_lowest_match(&memtype_rbroot, addr, addr + PAGE_SIZE);
 224         return data;
 225 }
 226
 227 #if defined(CONFIG_DEBUG_FS)
 228 int rbt_memtype_copy_nth_element(struct memtype *out, loff_t pos)
 229 {
 230         struct rb_node *node;
 231         int i = 1;
 232
 233         node = rb_first(&memtype_rbroot);
 234         while (node && pos != i) {
 235                 node = rb_next(node);
 236                 i++;
 237         }
 238
 239         if (node) { /* pos == i */
 240                 struct memtype *this = container_of(node, struct memtype, rb);
 241                 *out = *this;
 242                 return 0;
 243         } else {
 244                 return 1;
 245         }
 246 }
 247 #endif