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                                 enum page_cache_mode reqtype,
 126                                 enum page_cache_mode *newtype)
 127 {
 128         struct rb_node *node;
 129         struct memtype *match;
 130         enum page_cache_mode found_type = reqtype;
 131
 132         match = memtype_rb_lowest_match(&memtype_rbroot, start, end);
 133         if (match == NULL)
 134                 goto success;
 135
 136         if (match->type != found_type && newtype == NULL)
 137                 goto failure;
 138
 139         dprintk("Overlap at 0x%Lx-0x%Lx\n", match->start, match->end);
 140         found_type = match->type;
 141
 142         node = rb_next(&match->rb);
 143         while (node) {
 144                 match = container_of(node, struct memtype, rb);
 145
 146                 if (match->start >= end) /* Checked all possible matches */
 147                         goto success;
 148
 149                 if (is_node_overlap(match, start, end) &&
 150                     match->type != found_type) {
 151                         goto failure;
 152                 }
 153
 154                 node = rb_next(&match->rb);
 155         }
 156 success:
 157         if (newtype)
 158                 *newtype = found_type;
 159
 160         return 0;
 161
 162 failure:
 163         printk(KERN_INFO "%s:%d conflicting memory types "
 164                 "%Lx-%Lx %s<->%s\n", current->comm, current->pid, start,
 165                 end, cattr_name(found_type), cattr_name(match->type));
 166         return -EBUSY;
 167 }
 168
 169 static void memtype_rb_insert(struct rb_root *root, struct memtype *newdata)
 170 {
 171         struct rb_node **node = &(root->rb_node);
 172         struct rb_node *parent = NULL;
 173
 174         while (*node) {
 175                 struct memtype *data = container_of(*node, struct memtype, rb);
 176
 177                 parent = *node;
 178                 if (data->subtree_max_end < newdata->end)
 179                         data->subtree_max_end = newdata->end;
 180                 if (newdata->start <= data->start)
 181                         node = &((*node)->rb_left);
 182                 else if (newdata->start > data->start)
 183                         node = &((*node)->rb_right);
 184         }
 185
 186         newdata->subtree_max_end = newdata->end;
 187         rb_link_node(&newdata->rb, parent, node);
 188         rb_insert_augmented(&newdata->rb, root, &memtype_rb_augment_cb);
 189 }
 190
 191 int rbt_memtype_check_insert(struct memtype *new,
 192                              enum page_cache_mode *ret_type)
 193 {
 194         int err = 0;
 195
 196         err = memtype_rb_check_conflict(&memtype_rbroot, new->start, new->end,
 197                                                 new->type, ret_type);
 198
 199         if (!err) {
 200                 if (ret_type)
 201                         new->type = *ret_type;
 202
 203                 new->subtree_max_end = new->end;
 204                 memtype_rb_insert(&memtype_rbroot, new);
 205         }
 206         return err;
 207 }
 208
 209 struct memtype *rbt_memtype_erase(u64 start, u64 end)
 210 {
 211         struct memtype *data;
 212
 213         data = memtype_rb_exact_match(&memtype_rbroot, start, end);
 214         if (!data)
 215                 goto out;
 216
 217         rb_erase_augmented(&data->rb, &memtype_rbroot, &memtype_rb_augment_cb);
 218 out:
 219         return data;
 220 }
 221
 222 struct memtype *rbt_memtype_lookup(u64 addr)
 223 {
 224         struct memtype *data;
 225         data = memtype_rb_lowest_match(&memtype_rbroot, addr, addr + PAGE_SIZE);
 226         return data;
 227 }
 228
 229 #if defined(CONFIG_DEBUG_FS)
 230 int rbt_memtype_copy_nth_element(struct memtype *out, loff_t pos)
 231 {
 232         struct rb_node *node;
 233         int i = 1;
 234
 235         node = rb_first(&memtype_rbroot);
 236         while (node && pos != i) {
 237                 node = rb_next(node);
 238                 i++;
 239         }
 240
 241         if (node) { /* pos == i */
 242                 struct memtype *this = container_of(node, struct memtype, rb);
 243                 *out = *this;
 244                 return 0;
 245         } else {
 246                 return 1;
 247         }
 248 }
 249 #endif