arch/x86/mm/pat_rbtree.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Handle caching attributes in page tables (PAT)
   4  *
   5  * Authors: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
   6  *          Suresh B Siddha <suresh.b.siddha@intel.com>
   7  *
   8  * Interval tree (augmented rbtree) used to store the PAT memory type
   9  * reservations.
  10  */
  11
  12 #include <linux/seq_file.h>
  13 #include <linux/debugfs.h>
  14 #include <linux/kernel.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 = rb_entry(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 = rb_entry(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 enum {
 102         MEMTYPE_EXACT_MATCH     = 0,
 103         MEMTYPE_END_MATCH       = 1
 104 };
 105
 106 static struct memtype *memtype_rb_match(struct rb_root *root,
 107                                 u64 start, u64 end, int match_type)
 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_type == MEMTYPE_EXACT_MATCH) &&
 116                     (match->start == start) && (match->end == end))
 117                         return match;
 118
 119                 if ((match_type == MEMTYPE_END_MATCH) &&
 120                     (match->start < start) && (match->end == end))
 121                         return match;
 122
 123                 node = rb_next(&match->rb);
 124                 if (node)
 125                         match = rb_entry(node, struct memtype, rb);
 126                 else
 127                         match = NULL;
 128         }
 129
 130         return NULL; /* Returns NULL if there is no match */
 131 }
 132
 133 static int memtype_rb_check_conflict(struct rb_root *root,
 134                                 u64 start, u64 end,
 135                                 enum page_cache_mode reqtype,
 136                                 enum page_cache_mode *newtype)
 137 {
 138         struct rb_node *node;
 139         struct memtype *match;
 140         enum page_cache_mode found_type = reqtype;
 141
 142         match = memtype_rb_lowest_match(&memtype_rbroot, start, end);
 143         if (match == NULL)
 144                 goto success;
 145
 146         if (match->type != found_type && newtype == NULL)
 147                 goto failure;
 148
 149         dprintk("Overlap at 0x%Lx-0x%Lx\n", match->start, match->end);
 150         found_type = match->type;
 151
 152         node = rb_next(&match->rb);
 153         while (node) {
 154                 match = rb_entry(node, struct memtype, rb);
 155
 156                 if (match->start >= end) /* Checked all possible matches */
 157                         goto success;
 158
 159                 if (is_node_overlap(match, start, end) &&
 160                     match->type != found_type) {
 161                         goto failure;
 162                 }
 163
 164                 node = rb_next(&match->rb);
 165         }
 166 success:
 167         if (newtype)
 168                 *newtype = found_type;
 169
 170         return 0;
 171
 172 failure:
 173         pr_info("x86/PAT: %s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
 174                 current->comm, current->pid, start, end,
 175                 cattr_name(found_type), cattr_name(match->type));
 176         return -EBUSY;
 177 }
 178
 179 static void memtype_rb_insert(struct rb_root *root, struct memtype *newdata)
 180 {
 181         struct rb_node **node = &(root->rb_node);
 182         struct rb_node *parent = NULL;
 183
 184         while (*node) {
 185                 struct memtype *data = rb_entry(*node, struct memtype, rb);
 186
 187                 parent = *node;
 188                 if (data->subtree_max_end < newdata->end)
 189                         data->subtree_max_end = newdata->end;
 190                 if (newdata->start <= data->start)
 191                         node = &((*node)->rb_left);
 192                 else if (newdata->start > data->start)
 193                         node = &((*node)->rb_right);
 194         }
 195
 196         newdata->subtree_max_end = newdata->end;
 197         rb_link_node(&newdata->rb, parent, node);
 198         rb_insert_augmented(&newdata->rb, root, &memtype_rb_augment_cb);
 199 }
 200
 201 int rbt_memtype_check_insert(struct memtype *new,
 202                              enum page_cache_mode *ret_type)
 203 {
 204         int err = 0;
 205
 206         err = memtype_rb_check_conflict(&memtype_rbroot, new->start, new->end,
 207                                                 new->type, ret_type);
 208
 209         if (!err) {
 210                 if (ret_type)
 211                         new->type = *ret_type;
 212
 213                 new->subtree_max_end = new->end;
 214                 memtype_rb_insert(&memtype_rbroot, new);
 215         }
 216         return err;
 217 }
 218
 219 struct memtype *rbt_memtype_erase(u64 start, u64 end)
 220 {
 221         struct memtype *data;
 222
 223         /*
 224          * Since the memtype_rbroot tree allows overlapping ranges,
 225          * rbt_memtype_erase() checks with EXACT_MATCH first, i.e. free
 226          * a whole node for the munmap case.  If no such entry is found,
 227          * it then checks with END_MATCH, i.e. shrink the size of a node
 228          * from the end for the mremap case.
 229          */
 230         data = memtype_rb_match(&memtype_rbroot, start, end,
 231                                 MEMTYPE_EXACT_MATCH);
 232         if (!data) {
 233                 data = memtype_rb_match(&memtype_rbroot, start, end,
 234                                         MEMTYPE_END_MATCH);
 235                 if (!data)
 236                         return ERR_PTR(-EINVAL);
 237         }
 238
 239         if (data->start == start) {
 240                 /* munmap: erase this node */
 241                 rb_erase_augmented(&data->rb, &memtype_rbroot,
 242                                         &memtype_rb_augment_cb);
 243         } else {
 244                 /* mremap: update the end value of this node */
 245                 rb_erase_augmented(&data->rb, &memtype_rbroot,
 246                                         &memtype_rb_augment_cb);
 247                 data->end = start;
 248                 data->subtree_max_end = data->end;
 249                 memtype_rb_insert(&memtype_rbroot, data);
 250                 return NULL;
 251         }
 252
 253         return data;
 254 }
 255
 256 struct memtype *rbt_memtype_lookup(u64 addr)
 257 {
 258         return memtype_rb_lowest_match(&memtype_rbroot, addr, addr + PAGE_SIZE);
 259 }
 260
 261 #if defined(CONFIG_DEBUG_FS)
 262 int rbt_memtype_copy_nth_element(struct memtype *out, loff_t pos)
 263 {
 264         struct rb_node *node;
 265         int i = 1;
 266
 267         node = rb_first(&memtype_rbroot);
 268         while (node && pos != i) {
 269                 node = rb_next(node);
 270                 i++;
 271         }
 272
 273         if (node) { /* pos == i */
 274                 struct memtype *this = rb_entry(node, struct memtype, rb);
 275                 *out = *this;
 276                 return 0;
 277         } else {
 278                 return 1;
 279         }
 280 }
 281 #endif