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 /*
  17  * Although we spell it out in here, the Processor Trace
  18  * xfeature is completely unused.  We use other mechanisms
  19  * to save/restore PT state in Linux.
  20  */
  21 static const char *xfeature_names[] =
  22 {
  23         "x87 floating point registers"  ,
  24         "SSE registers"                 ,
  25         "AVX registers"                 ,
  26         "MPX bounds registers"          ,
  27         "MPX CSR"                       ,
  28         "AVX-512 opmask"                ,
  29         "AVX-512 Hi256"                 ,
  30         "AVX-512 ZMM_Hi256"             ,
  31         "Processor Trace (unused)"      ,
  32         "Protection Keys User registers",
  33         "unknown xstate feature"        ,
  34 };
  35
  36 /*
  37  * Mask of xstate features supported by the CPU and the kernel:
  38  */
  39 u64 xfeatures_mask __read_mostly;
  40
  41 static unsigned int xstate_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
  42 static unsigned int xstate_sizes[XFEATURE_MAX]   = { [ 0 ... XFEATURE_MAX - 1] = -1};
  43 static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8];
  44
  45 /*
  46  * Clear all of the X86_FEATURE_* bits that are unavailable
  47  * when the CPU has no XSAVE support.
  48  */
  49 void fpu__xstate_clear_all_cpu_caps(void)
  50 {
  51         setup_clear_cpu_cap(X86_FEATURE_XSAVE);
  52         setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
  53         setup_clear_cpu_cap(X86_FEATURE_XSAVEC);
  54         setup_clear_cpu_cap(X86_FEATURE_XSAVES);
  55         setup_clear_cpu_cap(X86_FEATURE_AVX);
  56         setup_clear_cpu_cap(X86_FEATURE_AVX2);
  57         setup_clear_cpu_cap(X86_FEATURE_AVX512F);
  58         setup_clear_cpu_cap(X86_FEATURE_AVX512PF);
  59         setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
  60         setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
  61         setup_clear_cpu_cap(X86_FEATURE_MPX);
  62         setup_clear_cpu_cap(X86_FEATURE_XGETBV1);
  63         setup_clear_cpu_cap(X86_FEATURE_PKU);
  64 }
  65
  66 /*
  67  * Return whether the system supports a given xfeature.
  68  *
  69  * Also return the name of the (most advanced) feature that the caller requested:
  70  */
  71 int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name)
  72 {
  73         u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask;
  74
  75         if (unlikely(feature_name)) {
  76                 long xfeature_idx, max_idx;
  77                 u64 xfeatures_print;
  78                 /*
  79                  * So we use FLS here to be able to print the most advanced
  80                  * feature that was requested but is missing. So if a driver
  81                  * asks about "XFEATURE_MASK_SSE | XFEATURE_MASK_YMM" we'll print the
  82                  * missing AVX feature - this is the most informative message
  83                  * to users:
  84                  */
  85                 if (xfeatures_missing)
  86                         xfeatures_print = xfeatures_missing;
  87                 else
  88                         xfeatures_print = xfeatures_needed;
  89
  90                 xfeature_idx = fls64(xfeatures_print)-1;
  91                 max_idx = ARRAY_SIZE(xfeature_names)-1;
  92                 xfeature_idx = min(xfeature_idx, max_idx);
  93
  94                 *feature_name = xfeature_names[xfeature_idx];
  95         }
  96
  97         if (xfeatures_missing)
  98                 return 0;
  99
 100         return 1;
 101 }
 102 EXPORT_SYMBOL_GPL(cpu_has_xfeatures);
 103
 104 /*
 105  * When executing XSAVEOPT (or other optimized XSAVE instructions), if
 106  * a processor implementation detects that an FPU state component is still
 107  * (or is again) in its initialized state, it may clear the corresponding
 108  * bit in the header.xfeatures field, and can skip the writeout of registers
 109  * to the corresponding memory layout.
 110  *
 111  * This means that when the bit is zero, the state component might still contain
 112  * some previous - non-initialized register state.
 113  *
 114  * Before writing xstate information to user-space we sanitize those components,
 115  * to always ensure that the memory layout of a feature will be in the init state
 116  * if the corresponding header bit is zero. This is to ensure that user-space doesn't
 117  * see some stale state in the memory layout during signal handling, debugging etc.
 118  */
 119 void fpstate_sanitize_xstate(struct fpu *fpu)
 120 {
 121         struct fxregs_state *fx = &fpu->state.fxsave;
 122         int feature_bit;
 123         u64 xfeatures;
 124
 125         if (!use_xsaveopt())
 126                 return;
 127
 128         xfeatures = fpu->state.xsave.header.xfeatures;
 129
 130         /*
 131          * None of the feature bits are in init state. So nothing else
 132          * to do for us, as the memory layout is up to date.
 133          */
 134         if ((xfeatures & xfeatures_mask) == xfeatures_mask)
 135                 return;
 136
 137         /*
 138          * FP is in init state
 139          */
 140         if (!(xfeatures & XFEATURE_MASK_FP)) {
 141                 fx->cwd = 0x37f;
 142                 fx->swd = 0;
 143                 fx->twd = 0;
 144                 fx->fop = 0;
 145                 fx->rip = 0;
 146                 fx->rdp = 0;
 147                 memset(&fx->st_space[0], 0, 128);
 148         }
 149
 150         /*
 151          * SSE is in init state
 152          */
 153         if (!(xfeatures & XFEATURE_MASK_SSE))
 154                 memset(&fx->xmm_space[0], 0, 256);
 155
 156         /*
 157          * First two features are FPU and SSE, which above we handled
 158          * in a special way already:
 159          */
 160         feature_bit = 0x2;
 161         xfeatures = (xfeatures_mask & ~xfeatures) >> 2;
 162
 163         /*
 164          * Update all the remaining memory layouts according to their
 165          * standard xstate layout, if their header bit is in the init
 166          * state:
 167          */
 168         while (xfeatures) {
 169                 if (xfeatures & 0x1) {
 170                         int offset = xstate_offsets[feature_bit];
 171                         int size = xstate_sizes[feature_bit];
 172
 173                         memcpy((void *)fx + offset,
 174                                (void *)&init_fpstate.xsave + offset,
 175                                size);
 176                 }
 177
 178                 xfeatures >>= 1;
 179                 feature_bit++;
 180         }
 181 }
 182
 183 /*
 184  * Enable the extended processor state save/restore feature.
 185  * Called once per CPU onlining.
 186  */
 187 void fpu__init_cpu_xstate(void)
 188 {
 189         if (!cpu_has_xsave || !xfeatures_mask)
 190                 return;
 191
 192         cr4_set_bits(X86_CR4_OSXSAVE);
 193         xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 194 }
 195
 196 /*
 197  * Note that in the future we will likely need a pair of
 198  * functions here: one for user xstates and the other for
 199  * system xstates.  For now, they are the same.
 200  */
 201 static int xfeature_enabled(enum xfeature xfeature)
 202 {
 203         return !!(xfeatures_mask & (1UL << xfeature));
 204 }
 205
 206 /*
 207  * Record the offsets and sizes of various xstates contained
 208  * in the XSAVE state memory layout.
 209  */
 210 static void __init setup_xstate_features(void)
 211 {
 212         u32 eax, ebx, ecx, edx, i;
 213         /* start at the beginnning of the "extended state" */
 214         unsigned int last_good_offset = offsetof(struct xregs_state,
 215                                                  extended_state_area);
 216
 217         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 218                 if (!xfeature_enabled(i))
 219                         continue;
 220
 221                 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 222                 xstate_offsets[i] = ebx;
 223                 xstate_sizes[i] = eax;
 224                 /*
 225                  * In our xstate size checks, we assume that the
 226                  * highest-numbered xstate feature has the
 227                  * highest offset in the buffer.  Ensure it does.
 228                  */
 229                 WARN_ONCE(last_good_offset > xstate_offsets[i],
 230                         "x86/fpu: misordered xstate at %d\n", last_good_offset);
 231                 last_good_offset = xstate_offsets[i];
 232
 233                 printk(KERN_INFO "x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n", i, ebx, i, eax);
 234         }
 235 }
 236
 237 static void __init print_xstate_feature(u64 xstate_mask)
 238 {
 239         const char *feature_name;
 240
 241         if (cpu_has_xfeatures(xstate_mask, &feature_name))
 242                 pr_info("x86/fpu: Supporting XSAVE feature 0x%03Lx: '%s'\n", xstate_mask, feature_name);
 243 }
 244
 245 /*
 246  * Print out all the supported xstate features:
 247  */
 248 static void __init print_xstate_features(void)
 249 {
 250         print_xstate_feature(XFEATURE_MASK_FP);
 251         print_xstate_feature(XFEATURE_MASK_SSE);
 252         print_xstate_feature(XFEATURE_MASK_YMM);
 253         print_xstate_feature(XFEATURE_MASK_BNDREGS);
 254         print_xstate_feature(XFEATURE_MASK_BNDCSR);
 255         print_xstate_feature(XFEATURE_MASK_OPMASK);
 256         print_xstate_feature(XFEATURE_MASK_ZMM_Hi256);
 257         print_xstate_feature(XFEATURE_MASK_Hi16_ZMM);
 258         print_xstate_feature(XFEATURE_MASK_PKRU);
 259 }
 260
 261 /*
 262  * This function sets up offsets and sizes of all extended states in
 263  * xsave area. This supports both standard format and compacted format
 264  * of the xsave aread.
 265  */
 266 static void __init setup_xstate_comp(void)
 267 {
 268         unsigned int xstate_comp_sizes[sizeof(xfeatures_mask)*8];
 269         int i;
 270
 271         /*
 272          * The FP xstates and SSE xstates are legacy states. They are always
 273          * in the fixed offsets in the xsave area in either compacted form
 274          * or standard form.
 275          */
 276         xstate_comp_offsets[0] = 0;
 277         xstate_comp_offsets[1] = offsetof(struct fxregs_state, xmm_space);
 278
 279         if (!cpu_has_xsaves) {
 280                 for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 281                         if (xfeature_enabled(i)) {
 282                                 xstate_comp_offsets[i] = xstate_offsets[i];
 283                                 xstate_comp_sizes[i] = xstate_sizes[i];
 284                         }
 285                 }
 286                 return;
 287         }
 288
 289         xstate_comp_offsets[FIRST_EXTENDED_XFEATURE] =
 290                 FXSAVE_SIZE + XSAVE_HDR_SIZE;
 291
 292         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 293                 if (xfeature_enabled(i))
 294                         xstate_comp_sizes[i] = xstate_sizes[i];
 295                 else
 296                         xstate_comp_sizes[i] = 0;
 297
 298                 if (i > FIRST_EXTENDED_XFEATURE)
 299                         xstate_comp_offsets[i] = xstate_comp_offsets[i-1]
 300                                         + xstate_comp_sizes[i-1];
 301
 302         }
 303 }
 304
 305 /*
 306  * setup the xstate image representing the init state
 307  */
 308 static void __init setup_init_fpu_buf(void)
 309 {
 310         static int on_boot_cpu __initdata = 1;
 311
 312         WARN_ON_FPU(!on_boot_cpu);
 313         on_boot_cpu = 0;
 314
 315         if (!cpu_has_xsave)
 316                 return;
 317
 318         setup_xstate_features();
 319         print_xstate_features();
 320
 321         if (cpu_has_xsaves) {
 322                 init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
 323                 init_fpstate.xsave.header.xfeatures = xfeatures_mask;
 324         }
 325
 326         /*
 327          * Init all the features state with header_bv being 0x0
 328          */
 329         copy_kernel_to_xregs_booting(&init_fpstate.xsave);
 330
 331         /*
 332          * Dump the init state again. This is to identify the init state
 333          * of any feature which is not represented by all zero's.
 334          */
 335         copy_xregs_to_kernel_booting(&init_fpstate.xsave);
 336 }
 337
 338 static int xfeature_is_supervisor(int xfeature_nr)
 339 {
 340         /*
 341          * We currently do not support supervisor states, but if
 342          * we did, we could find out like this.
 343          *
 344          * SDM says: If state component i is a user state component,
 345          * ECX[0] return 0; if state component i is a supervisor
 346          * state component, ECX[0] returns 1.
 347         u32 eax, ebx, ecx, edx;
 348         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx;
 349         return !!(ecx & 1);
 350         */
 351         return 0;
 352 }
 353 /*
 354 static int xfeature_is_user(int xfeature_nr)
 355 {
 356         return !xfeature_is_supervisor(xfeature_nr);
 357 }
 358 */
 359
 360 /*
 361  * This check is important because it is easy to get XSTATE_*
 362  * confused with XSTATE_BIT_*.
 363  */
 364 #define CHECK_XFEATURE(nr) do {         \
 365         WARN_ON(nr < FIRST_EXTENDED_XFEATURE);  \
 366         WARN_ON(nr >= XFEATURE_MAX);    \
 367 } while (0)
 368
 369 /*
 370  * We could cache this like xstate_size[], but we only use
 371  * it here, so it would be a waste of space.
 372  */
 373 static int xfeature_is_aligned(int xfeature_nr)
 374 {
 375         u32 eax, ebx, ecx, edx;
 376
 377         CHECK_XFEATURE(xfeature_nr);
 378         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 379         /*
 380          * The value returned by ECX[1] indicates the alignment
 381          * of state component i when the compacted format
 382          * of the extended region of an XSAVE area is used
 383          */
 384         return !!(ecx & 2);
 385 }
 386
 387 static int xfeature_uncompacted_offset(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 ebx;
 394 }
 395
 396 static int xfeature_size(int xfeature_nr)
 397 {
 398         u32 eax, ebx, ecx, edx;
 399
 400         CHECK_XFEATURE(xfeature_nr);
 401         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 402         return eax;
 403 }
 404
 405 /*
 406  * 'XSAVES' implies two different things:
 407  * 1. saving of supervisor/system state
 408  * 2. using the compacted format
 409  *
 410  * Use this function when dealing with the compacted format so
 411  * that it is obvious which aspect of 'XSAVES' is being handled
 412  * by the calling code.
 413  */
 414 static int using_compacted_format(void)
 415 {
 416         return cpu_has_xsaves;
 417 }
 418
 419 static void __xstate_dump_leaves(void)
 420 {
 421         int i;
 422         u32 eax, ebx, ecx, edx;
 423         static int should_dump = 1;
 424
 425         if (!should_dump)
 426                 return;
 427         should_dump = 0;
 428         /*
 429          * Dump out a few leaves past the ones that we support
 430          * just in case there are some goodies up there
 431          */
 432         for (i = 0; i < XFEATURE_MAX + 10; i++) {
 433                 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 434                 pr_warn("CPUID[%02x, %02x]: eax=%08x ebx=%08x ecx=%08x edx=%08x\n",
 435                         XSTATE_CPUID, i, eax, ebx, ecx, edx);
 436         }
 437 }
 438
 439 #define XSTATE_WARN_ON(x) do {                                                  \
 440         if (WARN_ONCE(x, "XSAVE consistency problem, dumping leaves")) {        \
 441                 __xstate_dump_leaves();                                         \
 442         }                                                                       \
 443 } while (0)
 444
 445 #define XCHECK_SZ(sz, nr, nr_macro, __struct) do {                      \
 446         if ((nr == nr_macro) &&                                         \
 447             WARN_ONCE(sz != sizeof(__struct),                           \
 448                 "%s: struct is %zu bytes, cpu state %d bytes\n",        \
 449                 __stringify(nr_macro), sizeof(__struct), sz)) {         \
 450                 __xstate_dump_leaves();                                 \
 451         }                                                               \
 452 } while (0)
 453
 454 /*
 455  * We have a C struct for each 'xstate'.  We need to ensure
 456  * that our software representation matches what the CPU
 457  * tells us about the state's size.
 458  */
 459 static void check_xstate_against_struct(int nr)
 460 {
 461         /*
 462          * Ask the CPU for the size of the state.
 463          */
 464         int sz = xfeature_size(nr);
 465         /*
 466          * Match each CPU state with the corresponding software
 467          * structure.
 468          */
 469         XCHECK_SZ(sz, nr, XFEATURE_YMM,       struct ymmh_struct);
 470         XCHECK_SZ(sz, nr, XFEATURE_BNDREGS,   struct mpx_bndreg_state);
 471         XCHECK_SZ(sz, nr, XFEATURE_BNDCSR,    struct mpx_bndcsr_state);
 472         XCHECK_SZ(sz, nr, XFEATURE_OPMASK,    struct avx_512_opmask_state);
 473         XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);
 474         XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM,  struct avx_512_hi16_state);
 475         XCHECK_SZ(sz, nr, XFEATURE_PKRU,      struct pkru_state);
 476
 477         /*
 478          * Make *SURE* to add any feature numbers in below if
 479          * there are "holes" in the xsave state component
 480          * numbers.
 481          */
 482         if ((nr < XFEATURE_YMM) ||
 483             (nr >= XFEATURE_MAX) ||
 484             (nr == XFEATURE_PT_UNIMPLEMENTED_SO_FAR)) {
 485                 WARN_ONCE(1, "no structure for xstate: %d\n", nr);
 486                 XSTATE_WARN_ON(1);
 487         }
 488 }
 489
 490 /*
 491  * This essentially double-checks what the cpu told us about
 492  * how large the XSAVE buffer needs to be.  We are recalculating
 493  * it to be safe.
 494  */
 495 static void do_extra_xstate_size_checks(void)
 496 {
 497         int paranoid_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
 498         int i;
 499
 500         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 501                 if (!xfeature_enabled(i))
 502                         continue;
 503
 504                 check_xstate_against_struct(i);
 505                 /*
 506                  * Supervisor state components can be managed only by
 507                  * XSAVES, which is compacted-format only.
 508                  */
 509                 if (!using_compacted_format())
 510                         XSTATE_WARN_ON(xfeature_is_supervisor(i));
 511
 512                 /* Align from the end of the previous feature */
 513                 if (xfeature_is_aligned(i))
 514                         paranoid_xstate_size = ALIGN(paranoid_xstate_size, 64);
 515                 /*
 516                  * The offset of a given state in the non-compacted
 517                  * format is given to us in a CPUID leaf.  We check
 518                  * them for being ordered (increasing offsets) in
 519                  * setup_xstate_features().
 520                  */
 521                 if (!using_compacted_format())
 522                         paranoid_xstate_size = xfeature_uncompacted_offset(i);
 523                 /*
 524                  * The compacted-format offset always depends on where
 525                  * the previous state ended.
 526                  */
 527                 paranoid_xstate_size += xfeature_size(i);
 528         }
 529         XSTATE_WARN_ON(paranoid_xstate_size != xstate_size);
 530 }
 531
 532 /*
 533  * Calculate total size of enabled xstates in XCR0/xfeatures_mask.
 534  *
 535  * Note the SDM's wording here.  "sub-function 0" only enumerates
 536  * the size of the *user* states.  If we use it to size a buffer
 537  * that we use 'XSAVES' on, we could potentially overflow the
 538  * buffer because 'XSAVES' saves system states too.
 539  *
 540  * Note that we do not currently set any bits on IA32_XSS so
 541  * 'XCR0 | IA32_XSS == XCR0' for now.
 542  */
 543 static unsigned int __init calculate_xstate_size(void)
 544 {
 545         unsigned int eax, ebx, ecx, edx;
 546         unsigned int calculated_xstate_size;
 547
 548         if (!cpu_has_xsaves) {
 549                 /*
 550                  * - CPUID function 0DH, sub-function 0:
 551                  *    EBX enumerates the size (in bytes) required by
 552                  *    the XSAVE instruction for an XSAVE area
 553                  *    containing all the *user* state components
 554                  *    corresponding to bits currently set in XCR0.
 555                  */
 556                 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 557                 calculated_xstate_size = ebx;
 558         } else {
 559                 /*
 560                  * - CPUID function 0DH, sub-function 1:
 561                  *    EBX enumerates the size (in bytes) required by
 562                  *    the XSAVES instruction for an XSAVE area
 563                  *    containing all the state components
 564                  *    corresponding to bits currently set in
 565                  *    XCR0 | IA32_XSS.
 566                  */
 567                 cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
 568                 calculated_xstate_size = ebx;
 569         }
 570         return calculated_xstate_size;
 571 }
 572
 573 /*
 574  * Will the runtime-enumerated 'xstate_size' fit in the init
 575  * task's statically-allocated buffer?
 576  */
 577 static bool is_supported_xstate_size(unsigned int test_xstate_size)
 578 {
 579         if (test_xstate_size <= sizeof(union fpregs_state))
 580                 return true;
 581
 582         pr_warn("x86/fpu: xstate buffer too small (%zu < %d), disabling xsave\n",
 583                         sizeof(union fpregs_state), test_xstate_size);
 584         return false;
 585 }
 586
 587 static int init_xstate_size(void)
 588 {
 589         /* Recompute the context size for enabled features: */
 590         unsigned int possible_xstate_size = calculate_xstate_size();
 591
 592         /* Ensure we have the space to store all enabled: */
 593         if (!is_supported_xstate_size(possible_xstate_size))
 594                 return -EINVAL;
 595
 596         /*
 597          * The size is OK, we are definitely going to use xsave,
 598          * make it known to the world that we need more space.
 599          */
 600         xstate_size = possible_xstate_size;
 601         do_extra_xstate_size_checks();
 602         return 0;
 603 }
 604
 605 /*
 606  * We enabled the XSAVE hardware, but something went wrong and
 607  * we can not use it.  Disable it.
 608  */
 609 static void fpu__init_disable_system_xstate(void)
 610 {
 611         xfeatures_mask = 0;
 612         cr4_clear_bits(X86_CR4_OSXSAVE);
 613         fpu__xstate_clear_all_cpu_caps();
 614 }
 615
 616 /*
 617  * Enable and initialize the xsave feature.
 618  * Called once per system bootup.
 619  */
 620 void __init fpu__init_system_xstate(void)
 621 {
 622         unsigned int eax, ebx, ecx, edx;
 623         static int on_boot_cpu __initdata = 1;
 624         int err;
 625
 626         WARN_ON_FPU(!on_boot_cpu);
 627         on_boot_cpu = 0;
 628
 629         if (!cpu_has_xsave) {
 630                 pr_info("x86/fpu: Legacy x87 FPU detected.\n");
 631                 return;
 632         }
 633
 634         if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
 635                 WARN_ON_FPU(1);
 636                 return;
 637         }
 638
 639         cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 640         xfeatures_mask = eax + ((u64)edx << 32);
 641
 642         if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
 643                 pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
 644                 BUG();
 645         }
 646
 647         xfeatures_mask &= fpu__get_supported_xfeatures_mask();
 648
 649         /* Enable xstate instructions to be able to continue with initialization: */
 650         fpu__init_cpu_xstate();
 651         err = init_xstate_size();
 652         if (err) {
 653                 /* something went wrong, boot without any XSAVE support */
 654                 fpu__init_disable_system_xstate();
 655                 return;
 656         }
 657
 658         update_regset_xstate_info(xstate_size, xfeatures_mask);
 659         fpu__init_prepare_fx_sw_frame();
 660         setup_init_fpu_buf();
 661         setup_xstate_comp();
 662
 663         pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
 664                 xfeatures_mask,
 665                 xstate_size,
 666                 cpu_has_xsaves ? "compacted" : "standard");
 667 }
 668
 669 /*
 670  * Restore minimal FPU state after suspend:
 671  */
 672 void fpu__resume_cpu(void)
 673 {
 674         /*
 675          * Restore XCR0 on xsave capable CPUs:
 676          */
 677         if (cpu_has_xsave)
 678                 xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 679 }
 680
 681 /*
 682  * Given the xsave area and a state inside, this function returns the
 683  * address of the state.
 684  *
 685  * This is the API that is called to get xstate address in either
 686  * standard format or compacted format of xsave area.
 687  *
 688  * Note that if there is no data for the field in the xsave buffer
 689  * this will return NULL.
 690  *
 691  * Inputs:
 692  *      xstate: the thread's storage area for all FPU data
 693  *      xstate_feature: state which is defined in xsave.h (e.g.
 694  *      XFEATURE_MASK_FP, XFEATURE_MASK_SSE, etc...)
 695  * Output:
 696  *      address of the state in the xsave area, or NULL if the
 697  *      field is not present in the xsave buffer.
 698  */
 699 void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
 700 {
 701         int feature_nr = fls64(xstate_feature) - 1;
 702         /*
 703          * Do we even *have* xsave state?
 704          */
 705         if (!boot_cpu_has(X86_FEATURE_XSAVE))
 706                 return NULL;
 707
 708         /*
 709          * We should not ever be requesting features that we
 710          * have not enabled.  Remember that pcntxt_mask is
 711          * what we write to the XCR0 register.
 712          */
 713         WARN_ONCE(!(xfeatures_mask & xstate_feature),
 714                   "get of unsupported state");
 715         /*
 716          * This assumes the last 'xsave*' instruction to
 717          * have requested that 'xstate_feature' be saved.
 718          * If it did not, we might be seeing and old value
 719          * of the field in the buffer.
 720          *
 721          * This can happen because the last 'xsave' did not
 722          * request that this feature be saved (unlikely)
 723          * or because the "init optimization" caused it
 724          * to not be saved.
 725          */
 726         if (!(xsave->header.xfeatures & xstate_feature))
 727                 return NULL;
 728
 729         return (void *)xsave + xstate_comp_offsets[feature_nr];
 730 }
 731 EXPORT_SYMBOL_GPL(get_xsave_addr);
 732
 733 /*
 734  * This wraps up the common operations that need to occur when retrieving
 735  * data from xsave state.  It first ensures that the current task was
 736  * using the FPU and retrieves the data in to a buffer.  It then calculates
 737  * the offset of the requested field in the buffer.
 738  *
 739  * This function is safe to call whether the FPU is in use or not.
 740  *
 741  * Note that this only works on the current task.
 742  *
 743  * Inputs:
 744  *      @xsave_state: state which is defined in xsave.h (e.g. XFEATURE_MASK_FP,
 745  *      XFEATURE_MASK_SSE, etc...)
 746  * Output:
 747  *      address of the state in the xsave area or NULL if the state
 748  *      is not present or is in its 'init state'.
 749  */
 750 const void *get_xsave_field_ptr(int xsave_state)
 751 {
 752         struct fpu *fpu = &current->thread.fpu;
 753
 754         if (!fpu->fpstate_active)
 755                 return NULL;
 756         /*
 757          * fpu__save() takes the CPU's xstate registers
 758          * and saves them off to the 'fpu memory buffer.
 759          */
 760         fpu__save(fpu);
 761
 762         return get_xsave_addr(&fpu->state.xsave, xsave_state);
 763 }