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_MPX);
  55 }
  56
  57 /*
  58  * Return whether the system supports a given xfeature.
  59  *
  60  * Also return the name of the (most advanced) feature that the caller requested:
  61  */
  62 int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name)
  63 {
  64         u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask;
  65
  66         if (unlikely(feature_name)) {
  67                 long xfeature_idx, max_idx;
  68                 u64 xfeatures_print;
  69                 /*
  70                  * So we use FLS here to be able to print the most advanced
  71                  * feature that was requested but is missing. So if a driver
  72                  * asks about "XFEATURE_MASK_SSE | XFEATURE_MASK_YMM" we'll print the
  73                  * missing AVX feature - this is the most informative message
  74                  * to users:
  75                  */
  76                 if (xfeatures_missing)
  77                         xfeatures_print = xfeatures_missing;
  78                 else
  79                         xfeatures_print = xfeatures_needed;
  80
  81                 xfeature_idx = fls64(xfeatures_print)-1;
  82                 max_idx = ARRAY_SIZE(xfeature_names)-1;
  83                 xfeature_idx = min(xfeature_idx, max_idx);
  84
  85                 *feature_name = xfeature_names[xfeature_idx];
  86         }
  87
  88         if (xfeatures_missing)
  89                 return 0;
  90
  91         return 1;
  92 }
  93 EXPORT_SYMBOL_GPL(cpu_has_xfeatures);
  94
  95 /*
  96  * When executing XSAVEOPT (or other optimized XSAVE instructions), if
  97  * a processor implementation detects that an FPU state component is still
  98  * (or is again) in its initialized state, it may clear the corresponding
  99  * bit in the header.xfeatures field, and can skip the writeout of registers
 100  * to the corresponding memory layout.
 101  *
 102  * This means that when the bit is zero, the state component might still contain
 103  * some previous - non-initialized register state.
 104  *
 105  * Before writing xstate information to user-space we sanitize those components,
 106  * to always ensure that the memory layout of a feature will be in the init state
 107  * if the corresponding header bit is zero. This is to ensure that user-space doesn't
 108  * see some stale state in the memory layout during signal handling, debugging etc.
 109  */
 110 void fpstate_sanitize_xstate(struct fpu *fpu)
 111 {
 112         struct fxregs_state *fx = &fpu->state.fxsave;
 113         int feature_bit;
 114         u64 xfeatures;
 115
 116         if (!use_xsaveopt())
 117                 return;
 118
 119         xfeatures = fpu->state.xsave.header.xfeatures;
 120
 121         /*
 122          * None of the feature bits are in init state. So nothing else
 123          * to do for us, as the memory layout is up to date.
 124          */
 125         if ((xfeatures & xfeatures_mask) == xfeatures_mask)
 126                 return;
 127
 128         /*
 129          * FP is in init state
 130          */
 131         if (!(xfeatures & XFEATURE_MASK_FP)) {
 132                 fx->cwd = 0x37f;
 133                 fx->swd = 0;
 134                 fx->twd = 0;
 135                 fx->fop = 0;
 136                 fx->rip = 0;
 137                 fx->rdp = 0;
 138                 memset(&fx->st_space[0], 0, 128);
 139         }
 140
 141         /*
 142          * SSE is in init state
 143          */
 144         if (!(xfeatures & XFEATURE_MASK_SSE))
 145                 memset(&fx->xmm_space[0], 0, 256);
 146
 147         /*
 148          * First two features are FPU and SSE, which above we handled
 149          * in a special way already:
 150          */
 151         feature_bit = 0x2;
 152         xfeatures = (xfeatures_mask & ~xfeatures) >> 2;
 153
 154         /*
 155          * Update all the remaining memory layouts according to their
 156          * standard xstate layout, if their header bit is in the init
 157          * state:
 158          */
 159         while (xfeatures) {
 160                 if (xfeatures & 0x1) {
 161                         int offset = xstate_offsets[feature_bit];
 162                         int size = xstate_sizes[feature_bit];
 163
 164                         memcpy((void *)fx + offset,
 165                                (void *)&init_fpstate.xsave + offset,
 166                                size);
 167                 }
 168
 169                 xfeatures >>= 1;
 170                 feature_bit++;
 171         }
 172 }
 173
 174 /*
 175  * Enable the extended processor state save/restore feature.
 176  * Called once per CPU onlining.
 177  */
 178 void fpu__init_cpu_xstate(void)
 179 {
 180         if (!cpu_has_xsave || !xfeatures_mask)
 181                 return;
 182
 183         cr4_set_bits(X86_CR4_OSXSAVE);
 184         xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 185 }
 186
 187 /*
 188  * Note that in the future we will likely need a pair of
 189  * functions here: one for user xstates and the other for
 190  * system xstates.  For now, they are the same.
 191  */
 192 static int xfeature_enabled(enum xfeature xfeature)
 193 {
 194         return !!(xfeatures_mask & (1UL << xfeature));
 195 }
 196
 197 /*
 198  * Record the offsets and sizes of various xstates contained
 199  * in the XSAVE state memory layout.
 200  */
 201 static void __init setup_xstate_features(void)
 202 {
 203         u32 eax, ebx, ecx, edx, i;
 204         /* start at the beginnning of the "extended state" */
 205         unsigned int last_good_offset = offsetof(struct xregs_state,
 206                                                  extended_state_area);
 207
 208         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 209                 if (!xfeature_enabled(i))
 210                         continue;
 211
 212                 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 213                 xstate_offsets[i] = ebx;
 214                 xstate_sizes[i] = eax;
 215                 /*
 216                  * In our xstate size checks, we assume that the
 217                  * highest-numbered xstate feature has the
 218                  * highest offset in the buffer.  Ensure it does.
 219                  */
 220                 WARN_ONCE(last_good_offset > xstate_offsets[i],
 221                         "x86/fpu: misordered xstate at %d\n", last_good_offset);
 222                 last_good_offset = xstate_offsets[i];
 223
 224                 printk(KERN_INFO "x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n", i, ebx, i, eax);
 225         }
 226 }
 227
 228 static void __init print_xstate_feature(u64 xstate_mask)
 229 {
 230         const char *feature_name;
 231
 232         if (cpu_has_xfeatures(xstate_mask, &feature_name))
 233                 pr_info("x86/fpu: Supporting XSAVE feature 0x%02Lx: '%s'\n", xstate_mask, feature_name);
 234 }
 235
 236 /*
 237  * Print out all the supported xstate features:
 238  */
 239 static void __init print_xstate_features(void)
 240 {
 241         print_xstate_feature(XFEATURE_MASK_FP);
 242         print_xstate_feature(XFEATURE_MASK_SSE);
 243         print_xstate_feature(XFEATURE_MASK_YMM);
 244         print_xstate_feature(XFEATURE_MASK_BNDREGS);
 245         print_xstate_feature(XFEATURE_MASK_BNDCSR);
 246         print_xstate_feature(XFEATURE_MASK_OPMASK);
 247         print_xstate_feature(XFEATURE_MASK_ZMM_Hi256);
 248         print_xstate_feature(XFEATURE_MASK_Hi16_ZMM);
 249 }
 250
 251 /*
 252  * This function sets up offsets and sizes of all extended states in
 253  * xsave area. This supports both standard format and compacted format
 254  * of the xsave aread.
 255  */
 256 static void __init setup_xstate_comp(void)
 257 {
 258         unsigned int xstate_comp_sizes[sizeof(xfeatures_mask)*8];
 259         int i;
 260
 261         /*
 262          * The FP xstates and SSE xstates are legacy states. They are always
 263          * in the fixed offsets in the xsave area in either compacted form
 264          * or standard form.
 265          */
 266         xstate_comp_offsets[0] = 0;
 267         xstate_comp_offsets[1] = offsetof(struct fxregs_state, xmm_space);
 268
 269         if (!cpu_has_xsaves) {
 270                 for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 271                         if (xfeature_enabled(i)) {
 272                                 xstate_comp_offsets[i] = xstate_offsets[i];
 273                                 xstate_comp_sizes[i] = xstate_sizes[i];
 274                         }
 275                 }
 276                 return;
 277         }
 278
 279         xstate_comp_offsets[FIRST_EXTENDED_XFEATURE] =
 280                 FXSAVE_SIZE + XSAVE_HDR_SIZE;
 281
 282         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 283                 if (xfeature_enabled(i))
 284                         xstate_comp_sizes[i] = xstate_sizes[i];
 285                 else
 286                         xstate_comp_sizes[i] = 0;
 287
 288                 if (i > FIRST_EXTENDED_XFEATURE)
 289                         xstate_comp_offsets[i] = xstate_comp_offsets[i-1]
 290                                         + xstate_comp_sizes[i-1];
 291
 292         }
 293 }
 294
 295 /*
 296  * All supported features have either init state all zeros or are
 297  * handled in setup_init_fpu() individually. This is an explicit
 298  * feature list and does not use XFEATURE_MASK*SUPPORTED to catch
 299  * newly added supported features at build time and make people
 300  * actually look at the init state for the new feature.
 301  */
 302 #define XFEATURES_INIT_FPSTATE_HANDLED          \
 303         (XFEATURE_MASK_FP |                     \
 304          XFEATURE_MASK_SSE |                    \
 305          XFEATURE_MASK_YMM |                    \
 306          XFEATURE_MASK_OPMASK |                 \
 307          XFEATURE_MASK_ZMM_Hi256 |              \
 308          XFEATURE_MASK_Hi16_ZMM  |              \
 309          XFEATURE_MASK_BNDREGS |                \
 310          XFEATURE_MASK_BNDCSR)
 311
 312 /*
 313  * setup the xstate image representing the init state
 314  */
 315 static void __init setup_init_fpu_buf(void)
 316 {
 317         static int on_boot_cpu = 1;
 318
 319         BUILD_BUG_ON(XCNTXT_MASK != XFEATURES_INIT_FPSTATE_HANDLED);
 320
 321         WARN_ON_FPU(!on_boot_cpu);
 322         on_boot_cpu = 0;
 323
 324         if (!cpu_has_xsave)
 325                 return;
 326
 327         setup_xstate_features();
 328         print_xstate_features();
 329
 330         if (cpu_has_xsaves) {
 331                 init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
 332                 init_fpstate.xsave.header.xfeatures = xfeatures_mask;
 333         }
 334
 335         /*
 336          * Init all the features state with header_bv being 0x0
 337          */
 338         copy_kernel_to_xregs_booting(&init_fpstate.xsave);
 339
 340         /*
 341          * All components are now in init state. Read the state back so
 342          * that init_fpstate contains all non-zero init state. This only
 343          * works with XSAVE, but not with XSAVEOPT and XSAVES because
 344          * those use the init optimization which skips writing data for
 345          * components in init state.
 346          *
 347          * XSAVE could be used, but that would require to reshuffle the
 348          * data when XSAVES is available because XSAVES uses xstate
 349          * compaction. But doing so is a pointless exercise because most
 350          * components have an all zeros init state except for the legacy
 351          * ones (FP and SSE). Those can be saved with FXSAVE into the
 352          * legacy area. Adding new features requires to ensure that init
 353          * state is all zeroes or if not to add the necessary handling
 354          * here.
 355          */
 356         fxsave(&init_fpstate.fxsave);
 357 }
 358
 359 static int xfeature_is_supervisor(int xfeature_nr)
 360 {
 361         /*
 362          * We currently do not support supervisor states, but if
 363          * we did, we could find out like this.
 364          *
 365          * SDM says: If state component i is a user state component,
 366          * ECX[0] return 0; if state component i is a supervisor
 367          * state component, ECX[0] returns 1.
 368         u32 eax, ebx, ecx, edx;
 369         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx;
 370         return !!(ecx & 1);
 371         */
 372         return 0;
 373 }
 374 /*
 375 static int xfeature_is_user(int xfeature_nr)
 376 {
 377         return !xfeature_is_supervisor(xfeature_nr);
 378 }
 379 */
 380
 381 /*
 382  * This check is important because it is easy to get XSTATE_*
 383  * confused with XSTATE_BIT_*.
 384  */
 385 #define CHECK_XFEATURE(nr) do {         \
 386         WARN_ON(nr < FIRST_EXTENDED_XFEATURE);  \
 387         WARN_ON(nr >= XFEATURE_MAX);    \
 388 } while (0)
 389
 390 /*
 391  * We could cache this like xstate_size[], but we only use
 392  * it here, so it would be a waste of space.
 393  */
 394 static int xfeature_is_aligned(int xfeature_nr)
 395 {
 396         u32 eax, ebx, ecx, edx;
 397
 398         CHECK_XFEATURE(xfeature_nr);
 399         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 400         /*
 401          * The value returned by ECX[1] indicates the alignment
 402          * of state component i when the compacted format
 403          * of the extended region of an XSAVE area is used
 404          */
 405         return !!(ecx & 2);
 406 }
 407
 408 static int xfeature_uncompacted_offset(int xfeature_nr)
 409 {
 410         u32 eax, ebx, ecx, edx;
 411
 412         CHECK_XFEATURE(xfeature_nr);
 413         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 414         return ebx;
 415 }
 416
 417 static int xfeature_size(int xfeature_nr)
 418 {
 419         u32 eax, ebx, ecx, edx;
 420
 421         CHECK_XFEATURE(xfeature_nr);
 422         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 423         return eax;
 424 }
 425
 426 /*
 427  * 'XSAVES' implies two different things:
 428  * 1. saving of supervisor/system state
 429  * 2. using the compacted format
 430  *
 431  * Use this function when dealing with the compacted format so
 432  * that it is obvious which aspect of 'XSAVES' is being handled
 433  * by the calling code.
 434  */
 435 static int using_compacted_format(void)
 436 {
 437         return cpu_has_xsaves;
 438 }
 439
 440 static void __xstate_dump_leaves(void)
 441 {
 442         int i;
 443         u32 eax, ebx, ecx, edx;
 444         static int should_dump = 1;
 445
 446         if (!should_dump)
 447                 return;
 448         should_dump = 0;
 449         /*
 450          * Dump out a few leaves past the ones that we support
 451          * just in case there are some goodies up there
 452          */
 453         for (i = 0; i < XFEATURE_MAX + 10; i++) {
 454                 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 455                 pr_warn("CPUID[%02x, %02x]: eax=%08x ebx=%08x ecx=%08x edx=%08x\n",
 456                         XSTATE_CPUID, i, eax, ebx, ecx, edx);
 457         }
 458 }
 459
 460 #define XSTATE_WARN_ON(x) do {                                                  \
 461         if (WARN_ONCE(x, "XSAVE consistency problem, dumping leaves")) {        \
 462                 __xstate_dump_leaves();                                         \
 463         }                                                                       \
 464 } while (0)
 465
 466 #define XCHECK_SZ(sz, nr, nr_macro, __struct) do {                      \
 467         if ((nr == nr_macro) &&                                         \
 468             WARN_ONCE(sz != sizeof(__struct),                           \
 469                 "%s: struct is %zu bytes, cpu state %d bytes\n",        \
 470                 __stringify(nr_macro), sizeof(__struct), sz)) {         \
 471                 __xstate_dump_leaves();                                 \
 472         }                                                               \
 473 } while (0)
 474
 475 /*
 476  * We have a C struct for each 'xstate'.  We need to ensure
 477  * that our software representation matches what the CPU
 478  * tells us about the state's size.
 479  */
 480 static void check_xstate_against_struct(int nr)
 481 {
 482         /*
 483          * Ask the CPU for the size of the state.
 484          */
 485         int sz = xfeature_size(nr);
 486         /*
 487          * Match each CPU state with the corresponding software
 488          * structure.
 489          */
 490         XCHECK_SZ(sz, nr, XFEATURE_YMM,       struct ymmh_struct);
 491         XCHECK_SZ(sz, nr, XFEATURE_BNDREGS,   struct mpx_bndreg_state);
 492         XCHECK_SZ(sz, nr, XFEATURE_BNDCSR,    struct mpx_bndcsr_state);
 493         XCHECK_SZ(sz, nr, XFEATURE_OPMASK,    struct avx_512_opmask_state);
 494         XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);
 495         XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM,  struct avx_512_hi16_state);
 496
 497         /*
 498          * Make *SURE* to add any feature numbers in below if
 499          * there are "holes" in the xsave state component
 500          * numbers.
 501          */
 502         if ((nr < XFEATURE_YMM) ||
 503             (nr >= XFEATURE_MAX)) {
 504                 WARN_ONCE(1, "no structure for xstate: %d\n", nr);
 505                 XSTATE_WARN_ON(1);
 506         }
 507 }
 508
 509 /*
 510  * This essentially double-checks what the cpu told us about
 511  * how large the XSAVE buffer needs to be.  We are recalculating
 512  * it to be safe.
 513  */
 514 static void do_extra_xstate_size_checks(void)
 515 {
 516         int paranoid_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
 517         int i;
 518
 519         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 520                 if (!xfeature_enabled(i))
 521                         continue;
 522
 523                 check_xstate_against_struct(i);
 524                 /*
 525                  * Supervisor state components can be managed only by
 526                  * XSAVES, which is compacted-format only.
 527                  */
 528                 if (!using_compacted_format())
 529                         XSTATE_WARN_ON(xfeature_is_supervisor(i));
 530
 531                 /* Align from the end of the previous feature */
 532                 if (xfeature_is_aligned(i))
 533                         paranoid_xstate_size = ALIGN(paranoid_xstate_size, 64);
 534                 /*
 535                  * The offset of a given state in the non-compacted
 536                  * format is given to us in a CPUID leaf.  We check
 537                  * them for being ordered (increasing offsets) in
 538                  * setup_xstate_features().
 539                  */
 540                 if (!using_compacted_format())
 541                         paranoid_xstate_size = xfeature_uncompacted_offset(i);
 542                 /*
 543                  * The compacted-format offset always depends on where
 544                  * the previous state ended.
 545                  */
 546                 paranoid_xstate_size += xfeature_size(i);
 547         }
 548         XSTATE_WARN_ON(paranoid_xstate_size != xstate_size);
 549 }
 550
 551 /*
 552  * Calculate total size of enabled xstates in XCR0/xfeatures_mask.
 553  *
 554  * Note the SDM's wording here.  "sub-function 0" only enumerates
 555  * the size of the *user* states.  If we use it to size a buffer
 556  * that we use 'XSAVES' on, we could potentially overflow the
 557  * buffer because 'XSAVES' saves system states too.
 558  *
 559  * Note that we do not currently set any bits on IA32_XSS so
 560  * 'XCR0 | IA32_XSS == XCR0' for now.
 561  */
 562 static unsigned int __init calculate_xstate_size(void)
 563 {
 564         unsigned int eax, ebx, ecx, edx;
 565         unsigned int calculated_xstate_size;
 566
 567         if (!cpu_has_xsaves) {
 568                 /*
 569                  * - CPUID function 0DH, sub-function 0:
 570                  *    EBX enumerates the size (in bytes) required by
 571                  *    the XSAVE instruction for an XSAVE area
 572                  *    containing all the *user* state components
 573                  *    corresponding to bits currently set in XCR0.
 574                  */
 575                 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 576                 calculated_xstate_size = ebx;
 577         } else {
 578                 /*
 579                  * - CPUID function 0DH, sub-function 1:
 580                  *    EBX enumerates the size (in bytes) required by
 581                  *    the XSAVES instruction for an XSAVE area
 582                  *    containing all the state components
 583                  *    corresponding to bits currently set in
 584                  *    XCR0 | IA32_XSS.
 585                  */
 586                 cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
 587                 calculated_xstate_size = ebx;
 588         }
 589         return calculated_xstate_size;
 590 }
 591
 592 /*
 593  * Will the runtime-enumerated 'xstate_size' fit in the init
 594  * task's statically-allocated buffer?
 595  */
 596 static bool is_supported_xstate_size(unsigned int test_xstate_size)
 597 {
 598         if (test_xstate_size <= sizeof(union fpregs_state))
 599                 return true;
 600
 601         pr_warn("x86/fpu: xstate buffer too small (%zu < %d), disabling xsave\n",
 602                         sizeof(union fpregs_state), test_xstate_size);
 603         return false;
 604 }
 605
 606 static int init_xstate_size(void)
 607 {
 608         /* Recompute the context size for enabled features: */
 609         unsigned int possible_xstate_size = calculate_xstate_size();
 610
 611         /* Ensure we have the space to store all enabled: */
 612         if (!is_supported_xstate_size(possible_xstate_size))
 613                 return -EINVAL;
 614
 615         /*
 616          * The size is OK, we are definitely going to use xsave,
 617          * make it known to the world that we need more space.
 618          */
 619         xstate_size = possible_xstate_size;
 620         do_extra_xstate_size_checks();
 621         return 0;
 622 }
 623
 624 /*
 625  * We enabled the XSAVE hardware, but something went wrong and
 626  * we can not use it.  Disable it.
 627  */
 628 static void fpu__init_disable_system_xstate(void)
 629 {
 630         xfeatures_mask = 0;
 631         cr4_clear_bits(X86_CR4_OSXSAVE);
 632         fpu__xstate_clear_all_cpu_caps();
 633 }
 634
 635 /*
 636  * Enable and initialize the xsave feature.
 637  * Called once per system bootup.
 638  */
 639 void __init fpu__init_system_xstate(void)
 640 {
 641         unsigned int eax, ebx, ecx, edx;
 642         static int on_boot_cpu = 1;
 643         int err;
 644
 645         WARN_ON_FPU(!on_boot_cpu);
 646         on_boot_cpu = 0;
 647
 648         if (!cpu_has_xsave) {
 649                 pr_info("x86/fpu: Legacy x87 FPU detected.\n");
 650                 return;
 651         }
 652
 653         if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
 654                 WARN_ON_FPU(1);
 655                 return;
 656         }
 657
 658         cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 659         xfeatures_mask = eax + ((u64)edx << 32);
 660
 661         if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
 662                 pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
 663                 BUG();
 664         }
 665
 666         xfeatures_mask &= fpu__get_supported_xfeatures_mask();
 667
 668         /* Enable xstate instructions to be able to continue with initialization: */
 669         fpu__init_cpu_xstate();
 670         err = init_xstate_size();
 671         if (err) {
 672                 /* something went wrong, boot without any XSAVE support */
 673                 fpu__init_disable_system_xstate();
 674                 return;
 675         }
 676
 677         update_regset_xstate_info(xstate_size, xfeatures_mask);
 678         fpu__init_prepare_fx_sw_frame();
 679         setup_init_fpu_buf();
 680         setup_xstate_comp();
 681
 682         pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
 683                 xfeatures_mask,
 684                 xstate_size,
 685                 cpu_has_xsaves ? "compacted" : "standard");
 686 }
 687
 688 /*
 689  * Restore minimal FPU state after suspend:
 690  */
 691 void fpu__resume_cpu(void)
 692 {
 693         /*
 694          * Restore XCR0 on xsave capable CPUs:
 695          */
 696         if (cpu_has_xsave)
 697                 xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 698 }
 699
 700 /*
 701  * Given the xsave area and a state inside, this function returns the
 702  * address of the state.
 703  *
 704  * This is the API that is called to get xstate address in either
 705  * standard format or compacted format of xsave area.
 706  *
 707  * Note that if there is no data for the field in the xsave buffer
 708  * this will return NULL.
 709  *
 710  * Inputs:
 711  *      xstate: the thread's storage area for all FPU data
 712  *      xstate_feature: state which is defined in xsave.h (e.g.
 713  *      XFEATURE_MASK_FP, XFEATURE_MASK_SSE, etc...)
 714  * Output:
 715  *      address of the state in the xsave area, or NULL if the
 716  *      field is not present in the xsave buffer.
 717  */
 718 void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
 719 {
 720         int feature_nr = fls64(xstate_feature) - 1;
 721         /*
 722          * Do we even *have* xsave state?
 723          */
 724         if (!boot_cpu_has(X86_FEATURE_XSAVE))
 725                 return NULL;
 726
 727         /*
 728          * We should not ever be requesting features that we
 729          * have not enabled.  Remember that pcntxt_mask is
 730          * what we write to the XCR0 register.
 731          */
 732         WARN_ONCE(!(xfeatures_mask & xstate_feature),
 733                   "get of unsupported state");
 734         /*
 735          * This assumes the last 'xsave*' instruction to
 736          * have requested that 'xstate_feature' be saved.
 737          * If it did not, we might be seeing and old value
 738          * of the field in the buffer.
 739          *
 740          * This can happen because the last 'xsave' did not
 741          * request that this feature be saved (unlikely)
 742          * or because the "init optimization" caused it
 743          * to not be saved.
 744          */
 745         if (!(xsave->header.xfeatures & xstate_feature))
 746                 return NULL;
 747
 748         return (void *)xsave + xstate_comp_offsets[feature_nr];
 749 }
 750 EXPORT_SYMBOL_GPL(get_xsave_addr);
 751
 752 /*
 753  * This wraps up the common operations that need to occur when retrieving
 754  * data from xsave state.  It first ensures that the current task was
 755  * using the FPU and retrieves the data in to a buffer.  It then calculates
 756  * the offset of the requested field in the buffer.
 757  *
 758  * This function is safe to call whether the FPU is in use or not.
 759  *
 760  * Note that this only works on the current task.
 761  *
 762  * Inputs:
 763  *      @xsave_state: state which is defined in xsave.h (e.g. XFEATURE_MASK_FP,
 764  *      XFEATURE_MASK_SSE, etc...)
 765  * Output:
 766  *      address of the state in the xsave area or NULL if the state
 767  *      is not present or is in its 'init state'.
 768  */
 769 const void *get_xsave_field_ptr(int xsave_state)
 770 {
 771         struct fpu *fpu = &current->thread.fpu;
 772
 773         if (!fpu->fpstate_active)
 774                 return NULL;
 775         /*
 776          * fpu__save() takes the CPU's xstate registers
 777          * and saves them off to the 'fpu memory buffer.
 778          */
 779         fpu__save(fpu);
 780
 781         return get_xsave_addr(&fpu->state.xsave, xsave_state);
 782 }