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.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 /* Update 'subtree_max_end' for a node, based on node and its children */
  58 static void memtype_rb_augment_cb(struct rb_node *node, void *__unused)
  59 {
  60         struct memtype *data;
  61         u64 max_end, child_max_end;
  62
  63         if (!node)
  64                 return;
  65
  66         data = container_of(node, struct memtype, rb);
  67         max_end = data->end;
  68
  69         child_max_end = get_subtree_max_end(node->rb_right);
  70         if (child_max_end > max_end)
  71                 max_end = child_max_end;
  72
  73         child_max_end = get_subtree_max_end(node->rb_left);
  74         if (child_max_end > max_end)
  75                 max_end = child_max_end;
  76
  77         data->subtree_max_end = max_end;
  78 }
  79
  80 /* Find the first (lowest start addr) overlapping range from rb tree */
  81 static struct memtype *memtype_rb_lowest_match(struct rb_root *root,
  82                                 u64 start, u64 end)
  83 {
  84         struct rb_node *node = root->rb_node;
  85         struct memtype *last_lower = NULL;
  86
  87         while (node) {
  88                 struct memtype *data = container_of(node, struct memtype, rb);
  89
  90                 if (get_subtree_max_end(node->rb_left) > start) {
  91                         /* Lowest overlap if any must be on left side */
  92                         node = node->rb_left;
  93                 } else if (is_node_overlap(data, start, end)) {
  94                         last_lower = data;
  95                         break;
  96                 } else if (start >= data->start) {
  97                         /* Lowest overlap if any must be on right side */
  98                         node = node->rb_right;
  99                 } else {
 100                         break;
 101                 }
 102         }
 103         return last_lower; /* Returns NULL if there is no overlap */
 104 }
 105
 106 static struct memtype *memtype_rb_exact_match(struct rb_root *root,
 107                                 u64 start, u64 end)
 108 {
 109         struct memtype *match;
 110
 111         match = memtype_rb_lowest_match(root, start, end);
 112         while (match != NULL && match->start < end) {
 113                 struct rb_node *node;
 114
 115                 if (match->start == start && match->end == end)
 116                         return match;
 117
 118                 node = rb_next(&match->rb);
 119                 if (node)
 120                         match = container_of(node, struct memtype, rb);
 121                 else
 122                         match = NULL;
 123         }
 124
 125         return NULL; /* Returns NULL if there is no exact match */
 126 }
 127
 128 static int memtype_rb_check_conflict(struct rb_root *root,
 129                                 u64 start, u64 end,
 130                                 unsigned long reqtype, unsigned long *newtype)
 131 {
 132         struct rb_node *node;
 133         struct memtype *match;
 134         int found_type = reqtype;
 135
 136         match = memtype_rb_lowest_match(&memtype_rbroot, start, end);
 137         if (match == NULL)
 138                 goto success;
 139
 140         if (match->type != found_type && newtype == NULL)
 141                 goto failure;
 142
 143         dprintk("Overlap at 0x%Lx-0x%Lx\n", match->start, match->end);
 144         found_type = match->type;
 145
 146         node = rb_next(&match->rb);
 147         while (node) {
 148                 match = container_of(node, struct memtype, rb);
 149
 150                 if (match->start >= end) /* Checked all possible matches */
 151                         goto success;
 152
 153                 if (is_node_overlap(match, start, end) &&
 154                     match->type != found_type) {
 155                         goto failure;
 156                 }
 157
 158                 node = rb_next(&match->rb);
 159         }
 160 success:
 161         if (newtype)
 162                 *newtype = found_type;
 163
 164         return 0;
 165
 166 failure:
 167         printk(KERN_INFO "%s:%d conflicting memory types "
 168                 "%Lx-%Lx %s<->%s\n", current->comm, current->pid, start,
 169                 end, cattr_name(found_type), cattr_name(match->type));
 170         return -EBUSY;
 171 }
 172
 173 static void memtype_rb_insert(struct rb_root *root, struct memtype *newdata)
 174 {
 175         struct rb_node **node = &(root->rb_node);
 176         struct rb_node *parent = NULL;
 177
 178         while (*node) {
 179                 struct memtype *data = container_of(*node, struct memtype, rb);
 180
 181                 parent = *node;
 182                 if (newdata->start <= data->start)
 183                         node = &((*node)->rb_left);
 184                 else if (newdata->start > data->start)
 185                         node = &((*node)->rb_right);
 186         }
 187
 188         rb_link_node(&newdata->rb, parent, node);
 189         rb_insert_color(&newdata->rb, root);
 190         rb_augment_insert(&newdata->rb, memtype_rb_augment_cb, NULL);
 191 }
 192
 193 int rbt_memtype_check_insert(struct memtype *new, unsigned long *ret_type)
 194 {
 195         int err = 0;
 196
 197         err = memtype_rb_check_conflict(&memtype_rbroot, new->start, new->end,
 198                                                 new->type, ret_type);
 199
 200         if (!err) {
 201                 if (ret_type)
 202                         new->type = *ret_type;
 203
 204                 new->subtree_max_end = new->end;
 205                 memtype_rb_insert(&memtype_rbroot, new);
 206         }
 207         return err;
 208 }
 209
 210 struct memtype *rbt_memtype_erase(u64 start, u64 end)
 211 {
 212         struct rb_node *deepest;
 213         struct memtype *data;
 214
 215         data = memtype_rb_exact_match(&memtype_rbroot, start, end);
 216         if (!data)
 217                 goto out;
 218
 219         deepest = rb_augment_erase_begin(&data->rb);
 220         rb_erase(&data->rb, &memtype_rbroot);
 221         rb_augment_erase_end(deepest, memtype_rb_augment_cb, NULL);
 222 out:
 223         return data;
 224 }
 225
 226 struct memtype *rbt_memtype_lookup(u64 addr)
 227 {
 228         struct memtype *data;
 229         data = memtype_rb_lowest_match(&memtype_rbroot, addr, addr + PAGE_SIZE);
 230         return data;
 231 }
 232
 233 #if defined(CONFIG_DEBUG_FS)
 234 int rbt_memtype_copy_nth_element(struct memtype *out, loff_t pos)
 235 {
 236         struct rb_node *node;
 237         int i = 1;
 238
 239         node = rb_first(&memtype_rbroot);
 240         while (node && pos != i) {
 241                 node = rb_next(node);
 242                 i++;
 243         }
 244
 245         if (node) { /* pos == i */
 246                 struct memtype *this = container_of(node, struct memtype, rb);
 247                 *out = *this;
 248                 return 0;
 249         } else {
 250                 return 1;
 251         }
 252 }
 253 #endif