arch/x86/mm/pat.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  * Loosely based on earlier PAT patchset from Eric Biederman and Andi Kleen.
   8  */
   9
  10 #include <linux/mm.h>
  11 #include <linux/kernel.h>
  12 #include <linux/gfp.h>
  13 #include <linux/fs.h>
  14
  15 #include <asm/msr.h>
  16 #include <asm/tlbflush.h>
  17 #include <asm/processor.h>
  18 #include <asm/pgtable.h>
  19 #include <asm/pat.h>
  20 #include <asm/e820.h>
  21 #include <asm/cacheflush.h>
  22 #include <asm/fcntl.h>
  23 #include <asm/mtrr.h>
  24
  25 int pat_wc_enabled = 1;
  26
  27 static u64 __read_mostly boot_pat_state;
  28
  29 static int nopat(char *str)
  30 {
  31         pat_wc_enabled = 0;
  32         printk(KERN_INFO "x86: PAT support disabled.\n");
  33
  34         return 0;
  35 }
  36 early_param("nopat", nopat);
  37
  38 static int pat_known_cpu(void)
  39 {
  40         if (!pat_wc_enabled)
  41                 return 0;
  42
  43         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
  44             (boot_cpu_data.x86 == 0xF ||
  45              (boot_cpu_data.x86 == 6 && boot_cpu_data.x86_model >= 15))) {
  46                 if (cpu_has_pat) {
  47                         return 1;
  48                 }
  49         }
  50
  51         pat_wc_enabled = 0;
  52         printk(KERN_INFO "CPU and/or kernel does not support PAT.\n");
  53         return 0;
  54 }
  55
  56 enum {
  57         PAT_UC = 0,             /* uncached */
  58         PAT_WC = 1,             /* Write combining */
  59         PAT_WT = 4,             /* Write Through */
  60         PAT_WP = 5,             /* Write Protected */
  61         PAT_WB = 6,             /* Write Back (default) */
  62         PAT_UC_MINUS = 7,       /* UC, but can be overriden by MTRR */
  63 };
  64
  65 #define PAT(x,y)        ((u64)PAT_ ## y << ((x)*8))
  66
  67 void pat_init(void)
  68 {
  69         u64 pat;
  70
  71 #ifndef CONFIG_X86_PAT
  72         nopat(NULL);
  73 #endif
  74
  75         /* Boot CPU enables PAT based on CPU feature */
  76         if (!smp_processor_id() && !pat_known_cpu())
  77                 return;
  78
  79         /* APs enable PAT iff boot CPU has enabled it before */
  80         if (smp_processor_id() && !pat_wc_enabled)
  81                 return;
  82
  83         /* Set PWT to Write-Combining. All other bits stay the same */
  84         /*
  85          * PTE encoding used in Linux:
  86          *      PAT
  87          *      |PCD
  88          *      ||PWT
  89          *      |||
  90          *      000 WB          _PAGE_CACHE_WB
  91          *      001 WC          _PAGE_CACHE_WC
  92          *      010 UC-         _PAGE_CACHE_UC_MINUS
  93          *      011 UC          _PAGE_CACHE_UC
  94          * PAT bit unused
  95          */
  96         pat = PAT(0,WB) | PAT(1,WC) | PAT(2,UC_MINUS) | PAT(3,UC) |
  97               PAT(4,WB) | PAT(5,WC) | PAT(6,UC_MINUS) | PAT(7,UC);
  98
  99         /* Boot CPU check */
 100         if (!smp_processor_id()) {
 101                 rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
 102         }
 103
 104         wrmsrl(MSR_IA32_CR_PAT, pat);
 105         printk(KERN_INFO "x86 PAT enabled: cpu %d, old 0x%Lx, new 0x%Lx\n",
 106                smp_processor_id(), boot_pat_state, pat);
 107 }
 108
 109 #undef PAT
 110
 111 static char *cattr_name(unsigned long flags)
 112 {
 113         switch (flags & _PAGE_CACHE_MASK) {
 114                 case _PAGE_CACHE_UC:            return "uncached";
 115                 case _PAGE_CACHE_UC_MINUS:      return "uncached-minus";
 116                 case _PAGE_CACHE_WB:            return "write-back";
 117                 case _PAGE_CACHE_WC:            return "write-combining";
 118                 default:                        return "broken";
 119         }
 120 }
 121
 122 /*
 123  * The global memtype list keeps track of memory type for specific
 124  * physical memory areas. Conflicting memory types in different
 125  * mappings can cause CPU cache corruption. To avoid this we keep track.
 126  *
 127  * The list is sorted based on starting address and can contain multiple
 128  * entries for each address (this allows reference counting for overlapping
 129  * areas). All the aliases have the same cache attributes of course.
 130  * Zero attributes are represented as holes.
 131  *
 132  * Currently the data structure is a list because the number of mappings
 133  * are expected to be relatively small. If this should be a problem
 134  * it could be changed to a rbtree or similar.
 135  *
 136  * memtype_lock protects the whole list.
 137  */
 138
 139 struct memtype {
 140         u64 start;
 141         u64 end;
 142         unsigned long type;
 143         struct list_head nd;
 144 };
 145
 146 static LIST_HEAD(memtype_list);
 147 static DEFINE_SPINLOCK(memtype_lock);   /* protects memtype list */
 148
 149 /*
 150  * Does intersection of PAT memory type and MTRR memory type and returns
 151  * the resulting memory type as PAT understands it.
 152  * (Type in pat and mtrr will not have same value)
 153  * The intersection is based on "Effective Memory Type" tables in IA-32
 154  * SDM vol 3a
 155  */
 156 static int pat_x_mtrr_type(u64 start, u64 end, unsigned long prot,
 157                                 unsigned long *ret_prot)
 158 {
 159         unsigned long pat_type;
 160         u8 mtrr_type;
 161
 162         mtrr_type = mtrr_type_lookup(start, end);
 163         if (mtrr_type == 0xFF) {                /* MTRR not enabled */
 164                 *ret_prot = prot;
 165                 return 0;
 166         }
 167         if (mtrr_type == 0xFE) {                /* MTRR match error */
 168                 *ret_prot = _PAGE_CACHE_UC;
 169                 return -1;
 170         }
 171         if (mtrr_type != MTRR_TYPE_UNCACHABLE &&
 172             mtrr_type != MTRR_TYPE_WRBACK &&
 173             mtrr_type != MTRR_TYPE_WRCOMB) {    /* MTRR type unhandled */
 174                 *ret_prot = _PAGE_CACHE_UC;
 175                 return -1;
 176         }
 177
 178         pat_type = prot & _PAGE_CACHE_MASK;
 179         prot &= (~_PAGE_CACHE_MASK);
 180
 181         /* Currently doing intersection by hand. Optimize it later. */
 182         if (pat_type == _PAGE_CACHE_WC) {
 183                 *ret_prot = prot | _PAGE_CACHE_WC;
 184         } else if (pat_type == _PAGE_CACHE_UC_MINUS) {
 185                 *ret_prot = prot | _PAGE_CACHE_UC_MINUS;
 186         } else if (pat_type == _PAGE_CACHE_UC ||
 187                    mtrr_type == MTRR_TYPE_UNCACHABLE) {
 188                 *ret_prot = prot | _PAGE_CACHE_UC;
 189         } else if (mtrr_type == MTRR_TYPE_WRCOMB) {
 190                 *ret_prot = prot | _PAGE_CACHE_WC;
 191         } else {
 192                 *ret_prot = prot | _PAGE_CACHE_WB;
 193         }
 194
 195         return 0;
 196 }
 197
 198 int reserve_memtype(u64 start, u64 end, unsigned long req_type,
 199                         unsigned long *ret_type)
 200 {
 201         struct memtype *new_entry = NULL;
 202         struct memtype *parse;
 203         unsigned long actual_type;
 204         int err = 0;
 205
 206         /* Only track when pat_wc_enabled */
 207         if (!pat_wc_enabled) {
 208                 if (ret_type)
 209                         *ret_type = req_type;
 210
 211                 return 0;
 212         }
 213
 214         /* Low ISA region is always mapped WB in page table. No need to track */
 215         if (start >= ISA_START_ADDRESS && (end - 1) <= ISA_END_ADDRESS) {
 216                 if (ret_type)
 217                         *ret_type = _PAGE_CACHE_WB;
 218
 219                 return 0;
 220         }
 221
 222         req_type &= _PAGE_CACHE_MASK;
 223         err = pat_x_mtrr_type(start, end, req_type, &actual_type);
 224         if (err) {
 225                 if (ret_type)
 226                         *ret_type = actual_type;
 227
 228                 return -EINVAL;
 229         }
 230
 231         new_entry  = kmalloc(sizeof(struct memtype), GFP_KERNEL);
 232         if (!new_entry)
 233                 return -ENOMEM;
 234
 235         new_entry->start = start;
 236         new_entry->end = end;
 237         new_entry->type = actual_type;
 238
 239         if (ret_type)
 240                 *ret_type = actual_type;
 241
 242         spin_lock(&memtype_lock);
 243
 244         /* Search for existing mapping that overlaps the current range */
 245         list_for_each_entry(parse, &memtype_list, nd) {
 246                 struct memtype *saved_ptr;
 247
 248                 if (parse->start >= end) {
 249                         printk("New Entry\n");
 250                         list_add(&new_entry->nd, parse->nd.prev);
 251                         new_entry = NULL;
 252                         break;
 253                 }
 254
 255                 if (start <= parse->start && end >= parse->start) {
 256                         if (actual_type != parse->type && ret_type) {
 257                                 actual_type = parse->type;
 258                                 *ret_type = actual_type;
 259                                 new_entry->type = actual_type;
 260                         }
 261
 262                         if (actual_type != parse->type) {
 263                                 printk(
 264                 KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
 265                                         current->comm, current->pid,
 266                                         start, end,
 267                                         cattr_name(actual_type),
 268                                         cattr_name(parse->type));
 269                                 err = -EBUSY;
 270                                 break;
 271                         }
 272
 273                         saved_ptr = parse;
 274                         /*
 275                          * Check to see whether the request overlaps more
 276                          * than one entry in the list
 277                          */
 278                         list_for_each_entry_continue(parse, &memtype_list, nd) {
 279                                 if (end <= parse->start) {
 280                                         break;
 281                                 }
 282
 283                                 if (actual_type != parse->type) {
 284                                         printk(
 285                 KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
 286                                                 current->comm, current->pid,
 287                                                 start, end,
 288                                                 cattr_name(actual_type),
 289                                                 cattr_name(parse->type));
 290                                         err = -EBUSY;
 291                                         break;
 292                                 }
 293                         }
 294
 295                         if (err) {
 296                                 break;
 297                         }
 298
 299                         printk("Overlap at 0x%Lx-0x%Lx\n",
 300                                saved_ptr->start, saved_ptr->end);
 301                         /* No conflict. Go ahead and add this new entry */
 302                         list_add(&new_entry->nd, saved_ptr->nd.prev);
 303                         new_entry = NULL;
 304                         break;
 305                 }
 306
 307                 if (start < parse->end) {
 308                         if (actual_type != parse->type && ret_type) {
 309                                 actual_type = parse->type;
 310                                 *ret_type = actual_type;
 311                                 new_entry->type = actual_type;
 312                         }
 313
 314                         if (actual_type != parse->type) {
 315                                 printk(
 316                 KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
 317                                         current->comm, current->pid,
 318                                         start, end,
 319                                         cattr_name(actual_type),
 320                                         cattr_name(parse->type));
 321                                 err = -EBUSY;
 322                                 break;
 323                         }
 324
 325                         saved_ptr = parse;
 326                         /*
 327                          * Check to see whether the request overlaps more
 328                          * than one entry in the list
 329                          */
 330                         list_for_each_entry_continue(parse, &memtype_list, nd) {
 331                                 if (end <= parse->start) {
 332                                         break;
 333                                 }
 334
 335                                 if (actual_type != parse->type) {
 336                                         printk(
 337                 KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
 338                                                 current->comm, current->pid,
 339                                                 start, end,
 340                                                 cattr_name(actual_type),
 341                                                 cattr_name(parse->type));
 342                                         err = -EBUSY;
 343                                         break;
 344                                 }
 345                         }
 346
 347                         if (err) {
 348                                 break;
 349                         }
 350
 351                         printk("Overlap at 0x%Lx-0x%Lx\n",
 352                                saved_ptr->start, saved_ptr->end);
 353                         /* No conflict. Go ahead and add this new entry */
 354                         list_add(&new_entry->nd, &saved_ptr->nd);
 355                         new_entry = NULL;
 356                         break;
 357                 }
 358         }
 359
 360         if (err) {
 361                 printk(
 362         "reserve_memtype failed 0x%Lx-0x%Lx, track %s, req %s\n",
 363                         start, end, cattr_name(new_entry->type),
 364                         cattr_name(req_type));
 365                 kfree(new_entry);
 366                 spin_unlock(&memtype_lock);
 367                 return err;
 368         }
 369
 370         if (new_entry) {
 371                 /* No conflict. Not yet added to the list. Add to the tail */
 372                 list_add_tail(&new_entry->nd, &memtype_list);
 373                 printk("New Entry\n");
 374         }
 375
 376         if (ret_type) {
 377                 printk(
 378         "reserve_memtype added 0x%Lx-0x%Lx, track %s, req %s, ret %s\n",
 379                         start, end, cattr_name(actual_type),
 380                         cattr_name(req_type), cattr_name(*ret_type));
 381         } else {
 382                 printk(
 383         "reserve_memtype added 0x%Lx-0x%Lx, track %s, req %s\n",
 384                         start, end, cattr_name(actual_type),
 385                         cattr_name(req_type));
 386         }
 387
 388         spin_unlock(&memtype_lock);
 389         return err;
 390 }
 391
 392 int free_memtype(u64 start, u64 end)
 393 {
 394         struct memtype *ml;
 395         int err = -EINVAL;
 396
 397         /* Only track when pat_wc_enabled */
 398         if (!pat_wc_enabled) {
 399                 return 0;
 400         }
 401
 402         /* Low ISA region is always mapped WB. No need to track */
 403         if (start >= ISA_START_ADDRESS && end <= ISA_END_ADDRESS) {
 404                 return 0;
 405         }
 406
 407         spin_lock(&memtype_lock);
 408         list_for_each_entry(ml, &memtype_list, nd) {
 409                 if (ml->start == start && ml->end == end) {
 410                         list_del(&ml->nd);
 411                         kfree(ml);
 412                         err = 0;
 413                         break;
 414                 }
 415         }
 416         spin_unlock(&memtype_lock);
 417
 418         if (err) {
 419                 printk(KERN_DEBUG "%s:%d freeing invalid memtype %Lx-%Lx\n",
 420                         current->comm, current->pid, start, end);
 421         }
 422
 423         printk( "free_memtype request 0x%Lx-0x%Lx\n", start, end);
 424         return err;
 425 }
 426