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