arch/x86/kernel/fpu/xstate.c

   1 /*
   2  * xsave/xrstor support.
   3  *
   4  * Author: Suresh Siddha <suresh.b.siddha@intel.com>
   5  */
   6 #include <linux/compat.h>
   7 #include <linux/cpu.h>
   8
   9 #include <asm/fpu/api.h>
  10 #include <asm/fpu/internal.h>
  11 #include <asm/fpu/signal.h>
  12 #include <asm/fpu/regset.h>
  13
  14 #include <asm/tlbflush.h>
  15
  16 static const char *xfeature_names[] =
  17 {
  18         "x87 floating point registers"  ,
  19         "SSE registers"                 ,
  20         "AVX registers"                 ,
  21         "MPX bounds registers"          ,
  22         "MPX CSR"                       ,
  23         "AVX-512 opmask"                ,
  24         "AVX-512 Hi256"                 ,
  25         "AVX-512 ZMM_Hi256"             ,
  26         "unknown xstate feature"        ,
  27 };
  28
  29 /*
  30  * Mask of xstate features supported by the CPU and the kernel:
  31  */
  32 u64 xfeatures_mask __read_mostly;
  33
  34 static unsigned int xstate_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
  35 static unsigned int xstate_sizes[XFEATURE_MAX]   = { [ 0 ... XFEATURE_MAX - 1] = -1};
  36 static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8];
  37
  38 /*
  39  * Clear all of the X86_FEATURE_* bits that are unavailable
  40  * when the CPU has no XSAVE support.
  41  */
  42 void fpu__xstate_clear_all_cpu_caps(void)
  43 {
  44         setup_clear_cpu_cap(X86_FEATURE_XSAVE);
  45         setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
  46         setup_clear_cpu_cap(X86_FEATURE_XSAVEC);
  47         setup_clear_cpu_cap(X86_FEATURE_XSAVES);
  48         setup_clear_cpu_cap(X86_FEATURE_AVX);
  49         setup_clear_cpu_cap(X86_FEATURE_AVX2);
  50         setup_clear_cpu_cap(X86_FEATURE_AVX512F);
  51         setup_clear_cpu_cap(X86_FEATURE_AVX512PF);
  52         setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
  53         setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
  54         setup_clear_cpu_cap(X86_FEATURE_AVX512DQ);
  55         setup_clear_cpu_cap(X86_FEATURE_AVX512BW);
  56         setup_clear_cpu_cap(X86_FEATURE_AVX512VL);
  57         setup_clear_cpu_cap(X86_FEATURE_MPX);
  58         setup_clear_cpu_cap(X86_FEATURE_XGETBV1);
  59 }
  60
  61 /*
  62  * Return whether the system supports a given xfeature.
  63  *
  64  * Also return the name of the (most advanced) feature that the caller requested:
  65  */
  66 int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name)
  67 {
  68         u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask;
  69
  70         if (unlikely(feature_name)) {
  71                 long xfeature_idx, max_idx;
  72                 u64 xfeatures_print;
  73                 /*
  74                  * So we use FLS here to be able to print the most advanced
  75                  * feature that was requested but is missing. So if a driver
  76                  * asks about "XFEATURE_MASK_SSE | XFEATURE_MASK_YMM" we'll print the
  77                  * missing AVX feature - this is the most informative message
  78                  * to users:
  79                  */
  80                 if (xfeatures_missing)
  81                         xfeatures_print = xfeatures_missing;
  82                 else
  83                         xfeatures_print = xfeatures_needed;
  84
  85                 xfeature_idx = fls64(xfeatures_print)-1;
  86                 max_idx = ARRAY_SIZE(xfeature_names)-1;
  87                 xfeature_idx = min(xfeature_idx, max_idx);
  88
  89                 *feature_name = xfeature_names[xfeature_idx];
  90         }
  91
  92         if (xfeatures_missing)
  93                 return 0;
  94
  95         return 1;
  96 }
  97 EXPORT_SYMBOL_GPL(cpu_has_xfeatures);
  98
  99 /*
 100  * When executing XSAVEOPT (or other optimized XSAVE instructions), if
 101  * a processor implementation detects that an FPU state component is still
 102  * (or is again) in its initialized state, it may clear the corresponding
 103  * bit in the header.xfeatures field, and can skip the writeout of registers
 104  * to the corresponding memory layout.
 105  *
 106  * This means that when the bit is zero, the state component might still contain
 107  * some previous - non-initialized register state.
 108  *
 109  * Before writing xstate information to user-space we sanitize those components,
 110  * to always ensure that the memory layout of a feature will be in the init state
 111  * if the corresponding header bit is zero. This is to ensure that user-space doesn't
 112  * see some stale state in the memory layout during signal handling, debugging etc.
 113  */
 114 void fpstate_sanitize_xstate(struct fpu *fpu)
 115 {
 116         struct fxregs_state *fx = &fpu->state.fxsave;
 117         int feature_bit;
 118         u64 xfeatures;
 119
 120         if (!use_xsaveopt())
 121                 return;
 122
 123         xfeatures = fpu->state.xsave.header.xfeatures;
 124
 125         /*
 126          * None of the feature bits are in init state. So nothing else
 127          * to do for us, as the memory layout is up to date.
 128          */
 129         if ((xfeatures & xfeatures_mask) == xfeatures_mask)
 130                 return;
 131
 132         /*
 133          * FP is in init state
 134          */
 135         if (!(xfeatures & XFEATURE_MASK_FP)) {
 136                 fx->cwd = 0x37f;
 137                 fx->swd = 0;
 138                 fx->twd = 0;
 139                 fx->fop = 0;
 140                 fx->rip = 0;
 141                 fx->rdp = 0;
 142                 memset(&fx->st_space[0], 0, 128);
 143         }
 144
 145         /*
 146          * SSE is in init state
 147          */
 148         if (!(xfeatures & XFEATURE_MASK_SSE))
 149                 memset(&fx->xmm_space[0], 0, 256);
 150
 151         /*
 152          * First two features are FPU and SSE, which above we handled
 153          * in a special way already:
 154          */
 155         feature_bit = 0x2;
 156         xfeatures = (xfeatures_mask & ~xfeatures) >> 2;
 157
 158         /*
 159          * Update all the remaining memory layouts according to their
 160          * standard xstate layout, if their header bit is in the init
 161          * state:
 162          */
 163         while (xfeatures) {
 164                 if (xfeatures & 0x1) {
 165                         int offset = xstate_offsets[feature_bit];
 166                         int size = xstate_sizes[feature_bit];
 167
 168                         memcpy((void *)fx + offset,
 169                                (void *)&init_fpstate.xsave + offset,
 170                                size);
 171                 }
 172
 173                 xfeatures >>= 1;
 174                 feature_bit++;
 175         }
 176 }
 177
 178 /*
 179  * Enable the extended processor state save/restore feature.
 180  * Called once per CPU onlining.
 181  */
 182 void fpu__init_cpu_xstate(void)
 183 {
 184         if (!cpu_has_xsave || !xfeatures_mask)
 185                 return;
 186
 187         cr4_set_bits(X86_CR4_OSXSAVE);
 188         xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 189 }
 190
 191 /*
 192  * Note that in the future we will likely need a pair of
 193  * functions here: one for user xstates and the other for
 194  * system xstates.  For now, they are the same.
 195  */
 196 static int xfeature_enabled(enum xfeature xfeature)
 197 {
 198         return !!(xfeatures_mask & (1UL << xfeature));
 199 }
 200
 201 /*
 202  * Record the offsets and sizes of various xstates contained
 203  * in the XSAVE state memory layout.
 204  */
 205 static void __init setup_xstate_features(void)
 206 {
 207         u32 eax, ebx, ecx, edx, i;
 208         /* start at the beginnning of the "extended state" */
 209         unsigned int last_good_offset = offsetof(struct xregs_state,
 210                                                  extended_state_area);
 211
 212         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 213                 if (!xfeature_enabled(i))
 214                         continue;
 215
 216                 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 217                 xstate_offsets[i] = ebx;
 218                 xstate_sizes[i] = eax;
 219                 /*
 220                  * In our xstate size checks, we assume that the
 221                  * highest-numbered xstate feature has the
 222                  * highest offset in the buffer.  Ensure it does.
 223                  */
 224                 WARN_ONCE(last_good_offset > xstate_offsets[i],
 225                         "x86/fpu: misordered xstate at %d\n", last_good_offset);
 226                 last_good_offset = xstate_offsets[i];
 227
 228                 printk(KERN_INFO "x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n", i, ebx, i, eax);
 229         }
 230 }
 231
 232 static void __init print_xstate_feature(u64 xstate_mask)
 233 {
 234         const char *feature_name;
 235
 236         if (cpu_has_xfeatures(xstate_mask, &feature_name))
 237                 pr_info("x86/fpu: Supporting XSAVE feature 0x%02Lx: '%s'\n", xstate_mask, feature_name);
 238 }
 239
 240 /*
 241  * Print out all the supported xstate features:
 242  */
 243 static void __init print_xstate_features(void)
 244 {
 245         print_xstate_feature(XFEATURE_MASK_FP);
 246         print_xstate_feature(XFEATURE_MASK_SSE);
 247         print_xstate_feature(XFEATURE_MASK_YMM);
 248         print_xstate_feature(XFEATURE_MASK_BNDREGS);
 249         print_xstate_feature(XFEATURE_MASK_BNDCSR);
 250         print_xstate_feature(XFEATURE_MASK_OPMASK);
 251         print_xstate_feature(XFEATURE_MASK_ZMM_Hi256);
 252         print_xstate_feature(XFEATURE_MASK_Hi16_ZMM);
 253 }
 254
 255 /*
 256  * This function sets up offsets and sizes of all extended states in
 257  * xsave area. This supports both standard format and compacted format
 258  * of the xsave aread.
 259  */
 260 static void __init setup_xstate_comp(void)
 261 {
 262         unsigned int xstate_comp_sizes[sizeof(xfeatures_mask)*8];
 263         int i;
 264
 265         /*
 266          * The FP xstates and SSE xstates are legacy states. They are always
 267          * in the fixed offsets in the xsave area in either compacted form
 268          * or standard form.
 269          */
 270         xstate_comp_offsets[0] = 0;
 271         xstate_comp_offsets[1] = offsetof(struct fxregs_state, xmm_space);
 272
 273         if (!cpu_has_xsaves) {
 274                 for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 275                         if (xfeature_enabled(i)) {
 276                                 xstate_comp_offsets[i] = xstate_offsets[i];
 277                                 xstate_comp_sizes[i] = xstate_sizes[i];
 278                         }
 279                 }
 280                 return;
 281         }
 282
 283         xstate_comp_offsets[FIRST_EXTENDED_XFEATURE] =
 284                 FXSAVE_SIZE + XSAVE_HDR_SIZE;
 285
 286         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 287                 if (xfeature_enabled(i))
 288                         xstate_comp_sizes[i] = xstate_sizes[i];
 289                 else
 290                         xstate_comp_sizes[i] = 0;
 291
 292                 if (i > FIRST_EXTENDED_XFEATURE)
 293                         xstate_comp_offsets[i] = xstate_comp_offsets[i-1]
 294                                         + xstate_comp_sizes[i-1];
 295
 296         }
 297 }
 298
 299 /*
 300  * setup the xstate image representing the init state
 301  */
 302 static void __init setup_init_fpu_buf(void)
 303 {
 304         static int on_boot_cpu __initdata = 1;
 305
 306         WARN_ON_FPU(!on_boot_cpu);
 307         on_boot_cpu = 0;
 308
 309         if (!cpu_has_xsave)
 310                 return;
 311
 312         setup_xstate_features();
 313         print_xstate_features();
 314
 315         if (cpu_has_xsaves) {
 316                 init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
 317                 init_fpstate.xsave.header.xfeatures = xfeatures_mask;
 318         }
 319
 320         /*
 321          * Init all the features state with header_bv being 0x0
 322          */
 323         copy_kernel_to_xregs_booting(&init_fpstate.xsave);
 324
 325         /*
 326          * Dump the init state again. This is to identify the init state
 327          * of any feature which is not represented by all zero's.
 328          */
 329         copy_xregs_to_kernel_booting(&init_fpstate.xsave);
 330 }
 331
 332 static int xfeature_is_supervisor(int xfeature_nr)
 333 {
 334         /*
 335          * We currently do not support supervisor states, but if
 336          * we did, we could find out like this.
 337          *
 338          * SDM says: If state component i is a user state component,
 339          * ECX[0] return 0; if state component i is a supervisor
 340          * state component, ECX[0] returns 1.
 341         u32 eax, ebx, ecx, edx;
 342         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx;
 343         return !!(ecx & 1);
 344         */
 345         return 0;
 346 }
 347 /*
 348 static int xfeature_is_user(int xfeature_nr)
 349 {
 350         return !xfeature_is_supervisor(xfeature_nr);
 351 }
 352 */
 353
 354 /*
 355  * This check is important because it is easy to get XSTATE_*
 356  * confused with XSTATE_BIT_*.
 357  */
 358 #define CHECK_XFEATURE(nr) do {         \
 359         WARN_ON(nr < FIRST_EXTENDED_XFEATURE);  \
 360         WARN_ON(nr >= XFEATURE_MAX);    \
 361 } while (0)
 362
 363 /*
 364  * We could cache this like xstate_size[], but we only use
 365  * it here, so it would be a waste of space.
 366  */
 367 static int xfeature_is_aligned(int xfeature_nr)
 368 {
 369         u32 eax, ebx, ecx, edx;
 370
 371         CHECK_XFEATURE(xfeature_nr);
 372         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 373         /*
 374          * The value returned by ECX[1] indicates the alignment
 375          * of state component i when the compacted format
 376          * of the extended region of an XSAVE area is used
 377          */
 378         return !!(ecx & 2);
 379 }
 380
 381 static int xfeature_uncompacted_offset(int xfeature_nr)
 382 {
 383         u32 eax, ebx, ecx, edx;
 384
 385         CHECK_XFEATURE(xfeature_nr);
 386         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 387         return ebx;
 388 }
 389
 390 static int xfeature_size(int xfeature_nr)
 391 {
 392         u32 eax, ebx, ecx, edx;
 393
 394         CHECK_XFEATURE(xfeature_nr);
 395         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 396         return eax;
 397 }
 398
 399 /*
 400  * 'XSAVES' implies two different things:
 401  * 1. saving of supervisor/system state
 402  * 2. using the compacted format
 403  *
 404  * Use this function when dealing with the compacted format so
 405  * that it is obvious which aspect of 'XSAVES' is being handled
 406  * by the calling code.
 407  */
 408 static int using_compacted_format(void)
 409 {
 410         return cpu_has_xsaves;
 411 }
 412
 413 static void __xstate_dump_leaves(void)
 414 {
 415         int i;
 416         u32 eax, ebx, ecx, edx;
 417         static int should_dump = 1;
 418
 419         if (!should_dump)
 420                 return;
 421         should_dump = 0;
 422         /*
 423          * Dump out a few leaves past the ones that we support
 424          * just in case there are some goodies up there
 425          */
 426         for (i = 0; i < XFEATURE_MAX + 10; i++) {
 427                 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 428                 pr_warn("CPUID[%02x, %02x]: eax=%08x ebx=%08x ecx=%08x edx=%08x\n",
 429                         XSTATE_CPUID, i, eax, ebx, ecx, edx);
 430         }
 431 }
 432
 433 #define XSTATE_WARN_ON(x) do {                                                  \
 434         if (WARN_ONCE(x, "XSAVE consistency problem, dumping leaves")) {        \
 435                 __xstate_dump_leaves();                                         \
 436         }                                                                       \
 437 } while (0)
 438
 439 #define XCHECK_SZ(sz, nr, nr_macro, __struct) do {                      \
 440         if ((nr == nr_macro) &&                                         \
 441             WARN_ONCE(sz != sizeof(__struct),                           \
 442                 "%s: struct is %zu bytes, cpu state %d bytes\n",        \
 443                 __stringify(nr_macro), sizeof(__struct), sz)) {         \
 444                 __xstate_dump_leaves();                                 \
 445         }                                                               \
 446 } while (0)
 447
 448 /*
 449  * We have a C struct for each 'xstate'.  We need to ensure
 450  * that our software representation matches what the CPU
 451  * tells us about the state's size.
 452  */
 453 static void check_xstate_against_struct(int nr)
 454 {
 455         /*
 456          * Ask the CPU for the size of the state.
 457          */
 458         int sz = xfeature_size(nr);
 459         /*
 460          * Match each CPU state with the corresponding software
 461          * structure.
 462          */
 463         XCHECK_SZ(sz, nr, XFEATURE_YMM,       struct ymmh_struct);
 464         XCHECK_SZ(sz, nr, XFEATURE_BNDREGS,   struct mpx_bndreg_state);
 465         XCHECK_SZ(sz, nr, XFEATURE_BNDCSR,    struct mpx_bndcsr_state);
 466         XCHECK_SZ(sz, nr, XFEATURE_OPMASK,    struct avx_512_opmask_state);
 467         XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);
 468         XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM,  struct avx_512_hi16_state);
 469
 470         /*
 471          * Make *SURE* to add any feature numbers in below if
 472          * there are "holes" in the xsave state component
 473          * numbers.
 474          */
 475         if ((nr < XFEATURE_YMM) ||
 476             (nr >= XFEATURE_MAX)) {
 477                 WARN_ONCE(1, "no structure for xstate: %d\n", nr);
 478                 XSTATE_WARN_ON(1);
 479         }
 480 }
 481
 482 /*
 483  * This essentially double-checks what the cpu told us about
 484  * how large the XSAVE buffer needs to be.  We are recalculating
 485  * it to be safe.
 486  */
 487 static void do_extra_xstate_size_checks(void)
 488 {
 489         int paranoid_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
 490         int i;
 491
 492         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 493                 if (!xfeature_enabled(i))
 494                         continue;
 495
 496                 check_xstate_against_struct(i);
 497                 /*
 498                  * Supervisor state components can be managed only by
 499                  * XSAVES, which is compacted-format only.
 500                  */
 501                 if (!using_compacted_format())
 502                         XSTATE_WARN_ON(xfeature_is_supervisor(i));
 503
 504                 /* Align from the end of the previous feature */
 505                 if (xfeature_is_aligned(i))
 506                         paranoid_xstate_size = ALIGN(paranoid_xstate_size, 64);
 507                 /*
 508                  * The offset of a given state in the non-compacted
 509                  * format is given to us in a CPUID leaf.  We check
 510                  * them for being ordered (increasing offsets) in
 511                  * setup_xstate_features().
 512                  */
 513                 if (!using_compacted_format())
 514                         paranoid_xstate_size = xfeature_uncompacted_offset(i);
 515                 /*
 516                  * The compacted-format offset always depends on where
 517                  * the previous state ended.
 518                  */
 519                 paranoid_xstate_size += xfeature_size(i);
 520         }
 521         XSTATE_WARN_ON(paranoid_xstate_size != xstate_size);
 522 }
 523
 524 /*
 525  * Calculate total size of enabled xstates in XCR0/xfeatures_mask.
 526  *
 527  * Note the SDM's wording here.  "sub-function 0" only enumerates
 528  * the size of the *user* states.  If we use it to size a buffer
 529  * that we use 'XSAVES' on, we could potentially overflow the
 530  * buffer because 'XSAVES' saves system states too.
 531  *
 532  * Note that we do not currently set any bits on IA32_XSS so
 533  * 'XCR0 | IA32_XSS == XCR0' for now.
 534  */
 535 static unsigned int __init calculate_xstate_size(void)
 536 {
 537         unsigned int eax, ebx, ecx, edx;
 538         unsigned int calculated_xstate_size;
 539
 540         if (!cpu_has_xsaves) {
 541                 /*
 542                  * - CPUID function 0DH, sub-function 0:
 543                  *    EBX enumerates the size (in bytes) required by
 544                  *    the XSAVE instruction for an XSAVE area
 545                  *    containing all the *user* state components
 546                  *    corresponding to bits currently set in XCR0.
 547                  */
 548                 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 549                 calculated_xstate_size = ebx;
 550         } else {
 551                 /*
 552                  * - CPUID function 0DH, sub-function 1:
 553                  *    EBX enumerates the size (in bytes) required by
 554                  *    the XSAVES instruction for an XSAVE area
 555                  *    containing all the state components
 556                  *    corresponding to bits currently set in
 557                  *    XCR0 | IA32_XSS.
 558                  */
 559                 cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
 560                 calculated_xstate_size = ebx;
 561         }
 562         return calculated_xstate_size;
 563 }
 564
 565 /*
 566  * Will the runtime-enumerated 'xstate_size' fit in the init
 567  * task's statically-allocated buffer?
 568  */
 569 static bool is_supported_xstate_size(unsigned int test_xstate_size)
 570 {
 571         if (test_xstate_size <= sizeof(union fpregs_state))
 572                 return true;
 573
 574         pr_warn("x86/fpu: xstate buffer too small (%zu < %d), disabling xsave\n",
 575                         sizeof(union fpregs_state), test_xstate_size);
 576         return false;
 577 }
 578
 579 static int init_xstate_size(void)
 580 {
 581         /* Recompute the context size for enabled features: */
 582         unsigned int possible_xstate_size = calculate_xstate_size();
 583
 584         /* Ensure we have the space to store all enabled: */
 585         if (!is_supported_xstate_size(possible_xstate_size))
 586                 return -EINVAL;
 587
 588         /*
 589          * The size is OK, we are definitely going to use xsave,
 590          * make it known to the world that we need more space.
 591          */
 592         xstate_size = possible_xstate_size;
 593         do_extra_xstate_size_checks();
 594         return 0;
 595 }
 596
 597 /*
 598  * We enabled the XSAVE hardware, but something went wrong and
 599  * we can not use it.  Disable it.
 600  */
 601 static void fpu__init_disable_system_xstate(void)
 602 {
 603         xfeatures_mask = 0;
 604         cr4_clear_bits(X86_CR4_OSXSAVE);
 605         fpu__xstate_clear_all_cpu_caps();
 606 }
 607
 608 /*
 609  * Enable and initialize the xsave feature.
 610  * Called once per system bootup.
 611  */
 612 void __init fpu__init_system_xstate(void)
 613 {
 614         unsigned int eax, ebx, ecx, edx;
 615         static int on_boot_cpu __initdata = 1;
 616         int err;
 617
 618         WARN_ON_FPU(!on_boot_cpu);
 619         on_boot_cpu = 0;
 620
 621         if (!cpu_has_xsave) {
 622                 pr_info("x86/fpu: Legacy x87 FPU detected.\n");
 623                 return;
 624         }
 625
 626         if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
 627                 WARN_ON_FPU(1);
 628                 return;
 629         }
 630
 631         cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 632         xfeatures_mask = eax + ((u64)edx << 32);
 633
 634         if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
 635                 pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
 636                 BUG();
 637         }
 638
 639         xfeatures_mask &= fpu__get_supported_xfeatures_mask();
 640
 641         /* Enable xstate instructions to be able to continue with initialization: */
 642         fpu__init_cpu_xstate();
 643         err = init_xstate_size();
 644         if (err) {
 645                 /* something went wrong, boot without any XSAVE support */
 646                 fpu__init_disable_system_xstate();
 647                 return;
 648         }
 649
 650         update_regset_xstate_info(xstate_size, xfeatures_mask);
 651         fpu__init_prepare_fx_sw_frame();
 652         setup_init_fpu_buf();
 653         setup_xstate_comp();
 654
 655         pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
 656                 xfeatures_mask,
 657                 xstate_size,
 658                 cpu_has_xsaves ? "compacted" : "standard");
 659 }
 660
 661 /*
 662  * Restore minimal FPU state after suspend:
 663  */
 664 void fpu__resume_cpu(void)
 665 {
 666         /*
 667          * Restore XCR0 on xsave capable CPUs:
 668          */
 669         if (cpu_has_xsave)
 670                 xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 671 }
 672
 673 /*
 674  * Given the xsave area and a state inside, this function returns the
 675  * address of the state.
 676  *
 677  * This is the API that is called to get xstate address in either
 678  * standard format or compacted format of xsave area.
 679  *
 680  * Note that if there is no data for the field in the xsave buffer
 681  * this will return NULL.
 682  *
 683  * Inputs:
 684  *      xstate: the thread's storage area for all FPU data
 685  *      xstate_feature: state which is defined in xsave.h (e.g.
 686  *      XFEATURE_MASK_FP, XFEATURE_MASK_SSE, etc...)
 687  * Output:
 688  *      address of the state in the xsave area, or NULL if the
 689  *      field is not present in the xsave buffer.
 690  */
 691 void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
 692 {
 693         int feature_nr = fls64(xstate_feature) - 1;
 694         /*
 695          * Do we even *have* xsave state?
 696          */
 697         if (!boot_cpu_has(X86_FEATURE_XSAVE))
 698                 return NULL;
 699
 700         /*
 701          * We should not ever be requesting features that we
 702          * have not enabled.  Remember that pcntxt_mask is
 703          * what we write to the XCR0 register.
 704          */
 705         WARN_ONCE(!(xfeatures_mask & xstate_feature),
 706                   "get of unsupported state");
 707         /*
 708          * This assumes the last 'xsave*' instruction to
 709          * have requested that 'xstate_feature' be saved.
 710          * If it did not, we might be seeing and old value
 711          * of the field in the buffer.
 712          *
 713          * This can happen because the last 'xsave' did not
 714          * request that this feature be saved (unlikely)
 715          * or because the "init optimization" caused it
 716          * to not be saved.
 717          */
 718         if (!(xsave->header.xfeatures & xstate_feature))
 719                 return NULL;
 720
 721         return (void *)xsave + xstate_comp_offsets[feature_nr];
 722 }
 723 EXPORT_SYMBOL_GPL(get_xsave_addr);
 724
 725 /*
 726  * This wraps up the common operations that need to occur when retrieving
 727  * data from xsave state.  It first ensures that the current task was
 728  * using the FPU and retrieves the data in to a buffer.  It then calculates
 729  * the offset of the requested field in the buffer.
 730  *
 731  * This function is safe to call whether the FPU is in use or not.
 732  *
 733  * Note that this only works on the current task.
 734  *
 735  * Inputs:
 736  *      @xsave_state: state which is defined in xsave.h (e.g. XFEATURE_MASK_FP,
 737  *      XFEATURE_MASK_SSE, etc...)
 738  * Output:
 739  *      address of the state in the xsave area or NULL if the state
 740  *      is not present or is in its 'init state'.
 741  */
 742 const void *get_xsave_field_ptr(int xsave_state)
 743 {
 744         struct fpu *fpu = &current->thread.fpu;
 745
 746         if (!fpu->fpstate_active)
 747                 return NULL;
 748         /*
 749          * fpu__save() takes the CPU's xstate registers
 750          * and saves them off to the 'fpu memory buffer.
 751          */
 752         fpu__save(fpu);
 753
 754         return get_xsave_addr(&fpu->state.xsave, xsave_state);
 755 }