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 };
  33
  34 /*
  35  * Mask of xstate features supported by the CPU and the kernel:
  36  */
  37 u64 xfeatures_mask __read_mostly;
  38
  39 static unsigned int xstate_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
  40 static unsigned int xstate_sizes[XFEATURE_MAX]   = { [ 0 ... XFEATURE_MAX - 1] = -1};
  41 static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8];
  42
  43 /*
  44  * Clear all of the X86_FEATURE_* bits that are unavailable
  45  * when the CPU has no XSAVE support.
  46  */
  47 void fpu__xstate_clear_all_cpu_caps(void)
  48 {
  49         setup_clear_cpu_cap(X86_FEATURE_XSAVE);
  50         setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
  51         setup_clear_cpu_cap(X86_FEATURE_XSAVEC);
  52         setup_clear_cpu_cap(X86_FEATURE_XSAVES);
  53         setup_clear_cpu_cap(X86_FEATURE_AVX);
  54         setup_clear_cpu_cap(X86_FEATURE_AVX2);
  55         setup_clear_cpu_cap(X86_FEATURE_AVX512F);
  56         setup_clear_cpu_cap(X86_FEATURE_AVX512PF);
  57         setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
  58         setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
  59         setup_clear_cpu_cap(X86_FEATURE_MPX);
  60         setup_clear_cpu_cap(X86_FEATURE_XGETBV1);
  61 }
  62
  63 /*
  64  * Return whether the system supports a given xfeature.
  65  *
  66  * Also return the name of the (most advanced) feature that the caller requested:
  67  */
  68 int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name)
  69 {
  70         u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask;
  71
  72         if (unlikely(feature_name)) {
  73                 long xfeature_idx, max_idx;
  74                 u64 xfeatures_print;
  75                 /*
  76                  * So we use FLS here to be able to print the most advanced
  77                  * feature that was requested but is missing. So if a driver
  78                  * asks about "XFEATURE_MASK_SSE | XFEATURE_MASK_YMM" we'll print the
  79                  * missing AVX feature - this is the most informative message
  80                  * to users:
  81                  */
  82                 if (xfeatures_missing)
  83                         xfeatures_print = xfeatures_missing;
  84                 else
  85                         xfeatures_print = xfeatures_needed;
  86
  87                 xfeature_idx = fls64(xfeatures_print)-1;
  88                 max_idx = ARRAY_SIZE(xfeature_names)-1;
  89                 xfeature_idx = min(xfeature_idx, max_idx);
  90
  91                 *feature_name = xfeature_names[xfeature_idx];
  92         }
  93
  94         if (xfeatures_missing)
  95                 return 0;
  96
  97         return 1;
  98 }
  99 EXPORT_SYMBOL_GPL(cpu_has_xfeatures);
 100
 101 /*
 102  * When executing XSAVEOPT (or other optimized XSAVE instructions), if
 103  * a processor implementation detects that an FPU state component is still
 104  * (or is again) in its initialized state, it may clear the corresponding
 105  * bit in the header.xfeatures field, and can skip the writeout of registers
 106  * to the corresponding memory layout.
 107  *
 108  * This means that when the bit is zero, the state component might still contain
 109  * some previous - non-initialized register state.
 110  *
 111  * Before writing xstate information to user-space we sanitize those components,
 112  * to always ensure that the memory layout of a feature will be in the init state
 113  * if the corresponding header bit is zero. This is to ensure that user-space doesn't
 114  * see some stale state in the memory layout during signal handling, debugging etc.
 115  */
 116 void fpstate_sanitize_xstate(struct fpu *fpu)
 117 {
 118         struct fxregs_state *fx = &fpu->state.fxsave;
 119         int feature_bit;
 120         u64 xfeatures;
 121
 122         if (!use_xsaveopt())
 123                 return;
 124
 125         xfeatures = fpu->state.xsave.header.xfeatures;
 126
 127         /*
 128          * None of the feature bits are in init state. So nothing else
 129          * to do for us, as the memory layout is up to date.
 130          */
 131         if ((xfeatures & xfeatures_mask) == xfeatures_mask)
 132                 return;
 133
 134         /*
 135          * FP is in init state
 136          */
 137         if (!(xfeatures & XFEATURE_MASK_FP)) {
 138                 fx->cwd = 0x37f;
 139                 fx->swd = 0;
 140                 fx->twd = 0;
 141                 fx->fop = 0;
 142                 fx->rip = 0;
 143                 fx->rdp = 0;
 144                 memset(&fx->st_space[0], 0, 128);
 145         }
 146
 147         /*
 148          * SSE is in init state
 149          */
 150         if (!(xfeatures & XFEATURE_MASK_SSE))
 151                 memset(&fx->xmm_space[0], 0, 256);
 152
 153         /*
 154          * First two features are FPU and SSE, which above we handled
 155          * in a special way already:
 156          */
 157         feature_bit = 0x2;
 158         xfeatures = (xfeatures_mask & ~xfeatures) >> 2;
 159
 160         /*
 161          * Update all the remaining memory layouts according to their
 162          * standard xstate layout, if their header bit is in the init
 163          * state:
 164          */
 165         while (xfeatures) {
 166                 if (xfeatures & 0x1) {
 167                         int offset = xstate_offsets[feature_bit];
 168                         int size = xstate_sizes[feature_bit];
 169
 170                         memcpy((void *)fx + offset,
 171                                (void *)&init_fpstate.xsave + offset,
 172                                size);
 173                 }
 174
 175                 xfeatures >>= 1;
 176                 feature_bit++;
 177         }
 178 }
 179
 180 /*
 181  * Enable the extended processor state save/restore feature.
 182  * Called once per CPU onlining.
 183  */
 184 void fpu__init_cpu_xstate(void)
 185 {
 186         if (!cpu_has_xsave || !xfeatures_mask)
 187                 return;
 188
 189         cr4_set_bits(X86_CR4_OSXSAVE);
 190         xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 191 }
 192
 193 /*
 194  * Note that in the future we will likely need a pair of
 195  * functions here: one for user xstates and the other for
 196  * system xstates.  For now, they are the same.
 197  */
 198 static int xfeature_enabled(enum xfeature xfeature)
 199 {
 200         return !!(xfeatures_mask & (1UL << xfeature));
 201 }
 202
 203 /*
 204  * Record the offsets and sizes of various xstates contained
 205  * in the XSAVE state memory layout.
 206  */
 207 static void __init setup_xstate_features(void)
 208 {
 209         u32 eax, ebx, ecx, edx, i;
 210         /* start at the beginnning of the "extended state" */
 211         unsigned int last_good_offset = offsetof(struct xregs_state,
 212                                                  extended_state_area);
 213
 214         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 215                 if (!xfeature_enabled(i))
 216                         continue;
 217
 218                 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 219                 xstate_offsets[i] = ebx;
 220                 xstate_sizes[i] = eax;
 221                 /*
 222                  * In our xstate size checks, we assume that the
 223                  * highest-numbered xstate feature has the
 224                  * highest offset in the buffer.  Ensure it does.
 225                  */
 226                 WARN_ONCE(last_good_offset > xstate_offsets[i],
 227                         "x86/fpu: misordered xstate at %d\n", last_good_offset);
 228                 last_good_offset = xstate_offsets[i];
 229
 230                 printk(KERN_INFO "x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n", i, ebx, i, eax);
 231         }
 232 }
 233
 234 static void __init print_xstate_feature(u64 xstate_mask)
 235 {
 236         const char *feature_name;
 237
 238         if (cpu_has_xfeatures(xstate_mask, &feature_name))
 239                 pr_info("x86/fpu: Supporting XSAVE feature 0x%02Lx: '%s'\n", xstate_mask, feature_name);
 240 }
 241
 242 /*
 243  * Print out all the supported xstate features:
 244  */
 245 static void __init print_xstate_features(void)
 246 {
 247         print_xstate_feature(XFEATURE_MASK_FP);
 248         print_xstate_feature(XFEATURE_MASK_SSE);
 249         print_xstate_feature(XFEATURE_MASK_YMM);
 250         print_xstate_feature(XFEATURE_MASK_BNDREGS);
 251         print_xstate_feature(XFEATURE_MASK_BNDCSR);
 252         print_xstate_feature(XFEATURE_MASK_OPMASK);
 253         print_xstate_feature(XFEATURE_MASK_ZMM_Hi256);
 254         print_xstate_feature(XFEATURE_MASK_Hi16_ZMM);
 255 }
 256
 257 /*
 258  * This function sets up offsets and sizes of all extended states in
 259  * xsave area. This supports both standard format and compacted format
 260  * of the xsave aread.
 261  */
 262 static void __init setup_xstate_comp(void)
 263 {
 264         unsigned int xstate_comp_sizes[sizeof(xfeatures_mask)*8];
 265         int i;
 266
 267         /*
 268          * The FP xstates and SSE xstates are legacy states. They are always
 269          * in the fixed offsets in the xsave area in either compacted form
 270          * or standard form.
 271          */
 272         xstate_comp_offsets[0] = 0;
 273         xstate_comp_offsets[1] = offsetof(struct fxregs_state, xmm_space);
 274
 275         if (!cpu_has_xsaves) {
 276                 for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 277                         if (xfeature_enabled(i)) {
 278                                 xstate_comp_offsets[i] = xstate_offsets[i];
 279                                 xstate_comp_sizes[i] = xstate_sizes[i];
 280                         }
 281                 }
 282                 return;
 283         }
 284
 285         xstate_comp_offsets[FIRST_EXTENDED_XFEATURE] =
 286                 FXSAVE_SIZE + XSAVE_HDR_SIZE;
 287
 288         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 289                 if (xfeature_enabled(i))
 290                         xstate_comp_sizes[i] = xstate_sizes[i];
 291                 else
 292                         xstate_comp_sizes[i] = 0;
 293
 294                 if (i > FIRST_EXTENDED_XFEATURE)
 295                         xstate_comp_offsets[i] = xstate_comp_offsets[i-1]
 296                                         + xstate_comp_sizes[i-1];
 297
 298         }
 299 }
 300
 301 /*
 302  * setup the xstate image representing the init state
 303  */
 304 static void __init setup_init_fpu_buf(void)
 305 {
 306         static int on_boot_cpu __initdata = 1;
 307
 308         WARN_ON_FPU(!on_boot_cpu);
 309         on_boot_cpu = 0;
 310
 311         if (!cpu_has_xsave)
 312                 return;
 313
 314         setup_xstate_features();
 315         print_xstate_features();
 316
 317         if (cpu_has_xsaves) {
 318                 init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
 319                 init_fpstate.xsave.header.xfeatures = xfeatures_mask;
 320         }
 321
 322         /*
 323          * Init all the features state with header_bv being 0x0
 324          */
 325         copy_kernel_to_xregs_booting(&init_fpstate.xsave);
 326
 327         /*
 328          * Dump the init state again. This is to identify the init state
 329          * of any feature which is not represented by all zero's.
 330          */
 331         copy_xregs_to_kernel_booting(&init_fpstate.xsave);
 332 }
 333
 334 static int xfeature_is_supervisor(int xfeature_nr)
 335 {
 336         /*
 337          * We currently do not support supervisor states, but if
 338          * we did, we could find out like this.
 339          *
 340          * SDM says: If state component i is a user state component,
 341          * ECX[0] return 0; if state component i is a supervisor
 342          * state component, ECX[0] returns 1.
 343         u32 eax, ebx, ecx, edx;
 344         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx;
 345         return !!(ecx & 1);
 346         */
 347         return 0;
 348 }
 349 /*
 350 static int xfeature_is_user(int xfeature_nr)
 351 {
 352         return !xfeature_is_supervisor(xfeature_nr);
 353 }
 354 */
 355
 356 /*
 357  * This check is important because it is easy to get XSTATE_*
 358  * confused with XSTATE_BIT_*.
 359  */
 360 #define CHECK_XFEATURE(nr) do {         \
 361         WARN_ON(nr < FIRST_EXTENDED_XFEATURE);  \
 362         WARN_ON(nr >= XFEATURE_MAX);    \
 363 } while (0)
 364
 365 /*
 366  * We could cache this like xstate_size[], but we only use
 367  * it here, so it would be a waste of space.
 368  */
 369 static int xfeature_is_aligned(int xfeature_nr)
 370 {
 371         u32 eax, ebx, ecx, edx;
 372
 373         CHECK_XFEATURE(xfeature_nr);
 374         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 375         /*
 376          * The value returned by ECX[1] indicates the alignment
 377          * of state component i when the compacted format
 378          * of the extended region of an XSAVE area is used
 379          */
 380         return !!(ecx & 2);
 381 }
 382
 383 static int xfeature_uncompacted_offset(int xfeature_nr)
 384 {
 385         u32 eax, ebx, ecx, edx;
 386
 387         CHECK_XFEATURE(xfeature_nr);
 388         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 389         return ebx;
 390 }
 391
 392 static int xfeature_size(int xfeature_nr)
 393 {
 394         u32 eax, ebx, ecx, edx;
 395
 396         CHECK_XFEATURE(xfeature_nr);
 397         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 398         return eax;
 399 }
 400
 401 /*
 402  * 'XSAVES' implies two different things:
 403  * 1. saving of supervisor/system state
 404  * 2. using the compacted format
 405  *
 406  * Use this function when dealing with the compacted format so
 407  * that it is obvious which aspect of 'XSAVES' is being handled
 408  * by the calling code.
 409  */
 410 static int using_compacted_format(void)
 411 {
 412         return cpu_has_xsaves;
 413 }
 414
 415 static void __xstate_dump_leaves(void)
 416 {
 417         int i;
 418         u32 eax, ebx, ecx, edx;
 419         static int should_dump = 1;
 420
 421         if (!should_dump)
 422                 return;
 423         should_dump = 0;
 424         /*
 425          * Dump out a few leaves past the ones that we support
 426          * just in case there are some goodies up there
 427          */
 428         for (i = 0; i < XFEATURE_MAX + 10; i++) {
 429                 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 430                 pr_warn("CPUID[%02x, %02x]: eax=%08x ebx=%08x ecx=%08x edx=%08x\n",
 431                         XSTATE_CPUID, i, eax, ebx, ecx, edx);
 432         }
 433 }
 434
 435 #define XSTATE_WARN_ON(x) do {                                                  \
 436         if (WARN_ONCE(x, "XSAVE consistency problem, dumping leaves")) {        \
 437                 __xstate_dump_leaves();                                         \
 438         }                                                                       \
 439 } while (0)
 440
 441 #define XCHECK_SZ(sz, nr, nr_macro, __struct) do {                      \
 442         if ((nr == nr_macro) &&                                         \
 443             WARN_ONCE(sz != sizeof(__struct),                           \
 444                 "%s: struct is %zu bytes, cpu state %d bytes\n",        \
 445                 __stringify(nr_macro), sizeof(__struct), sz)) {         \
 446                 __xstate_dump_leaves();                                 \
 447         }                                                               \
 448 } while (0)
 449
 450 /*
 451  * We have a C struct for each 'xstate'.  We need to ensure
 452  * that our software representation matches what the CPU
 453  * tells us about the state's size.
 454  */
 455 static void check_xstate_against_struct(int nr)
 456 {
 457         /*
 458          * Ask the CPU for the size of the state.
 459          */
 460         int sz = xfeature_size(nr);
 461         /*
 462          * Match each CPU state with the corresponding software
 463          * structure.
 464          */
 465         XCHECK_SZ(sz, nr, XFEATURE_YMM,       struct ymmh_struct);
 466         XCHECK_SZ(sz, nr, XFEATURE_BNDREGS,   struct mpx_bndreg_state);
 467         XCHECK_SZ(sz, nr, XFEATURE_BNDCSR,    struct mpx_bndcsr_state);
 468         XCHECK_SZ(sz, nr, XFEATURE_OPMASK,    struct avx_512_opmask_state);
 469         XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);
 470         XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM,  struct avx_512_hi16_state);
 471
 472         /*
 473          * Make *SURE* to add any feature numbers in below if
 474          * there are "holes" in the xsave state component
 475          * numbers.
 476          */
 477         if ((nr < XFEATURE_YMM) ||
 478             (nr >= XFEATURE_MAX) ||
 479             (nr == XFEATURE_PT_UNIMPLEMENTED_SO_FAR)) {
 480                 WARN_ONCE(1, "no structure for xstate: %d\n", nr);
 481                 XSTATE_WARN_ON(1);
 482         }
 483 }
 484
 485 /*
 486  * This essentially double-checks what the cpu told us about
 487  * how large the XSAVE buffer needs to be.  We are recalculating
 488  * it to be safe.
 489  */
 490 static void do_extra_xstate_size_checks(void)
 491 {
 492         int paranoid_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
 493         int i;
 494
 495         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 496                 if (!xfeature_enabled(i))
 497                         continue;
 498
 499                 check_xstate_against_struct(i);
 500                 /*
 501                  * Supervisor state components can be managed only by
 502                  * XSAVES, which is compacted-format only.
 503                  */
 504                 if (!using_compacted_format())
 505                         XSTATE_WARN_ON(xfeature_is_supervisor(i));
 506
 507                 /* Align from the end of the previous feature */
 508                 if (xfeature_is_aligned(i))
 509                         paranoid_xstate_size = ALIGN(paranoid_xstate_size, 64);
 510                 /*
 511                  * The offset of a given state in the non-compacted
 512                  * format is given to us in a CPUID leaf.  We check
 513                  * them for being ordered (increasing offsets) in
 514                  * setup_xstate_features().
 515                  */
 516                 if (!using_compacted_format())
 517                         paranoid_xstate_size = xfeature_uncompacted_offset(i);
 518                 /*
 519                  * The compacted-format offset always depends on where
 520                  * the previous state ended.
 521                  */
 522                 paranoid_xstate_size += xfeature_size(i);
 523         }
 524         XSTATE_WARN_ON(paranoid_xstate_size != xstate_size);
 525 }
 526
 527 /*
 528  * Calculate total size of enabled xstates in XCR0/xfeatures_mask.
 529  *
 530  * Note the SDM's wording here.  "sub-function 0" only enumerates
 531  * the size of the *user* states.  If we use it to size a buffer
 532  * that we use 'XSAVES' on, we could potentially overflow the
 533  * buffer because 'XSAVES' saves system states too.
 534  *
 535  * Note that we do not currently set any bits on IA32_XSS so
 536  * 'XCR0 | IA32_XSS == XCR0' for now.
 537  */
 538 static unsigned int __init calculate_xstate_size(void)
 539 {
 540         unsigned int eax, ebx, ecx, edx;
 541         unsigned int calculated_xstate_size;
 542
 543         if (!cpu_has_xsaves) {
 544                 /*
 545                  * - CPUID function 0DH, sub-function 0:
 546                  *    EBX enumerates the size (in bytes) required by
 547                  *    the XSAVE instruction for an XSAVE area
 548                  *    containing all the *user* state components
 549                  *    corresponding to bits currently set in XCR0.
 550                  */
 551                 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 552                 calculated_xstate_size = ebx;
 553         } else {
 554                 /*
 555                  * - CPUID function 0DH, sub-function 1:
 556                  *    EBX enumerates the size (in bytes) required by
 557                  *    the XSAVES instruction for an XSAVE area
 558                  *    containing all the state components
 559                  *    corresponding to bits currently set in
 560                  *    XCR0 | IA32_XSS.
 561                  */
 562                 cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
 563                 calculated_xstate_size = ebx;
 564         }
 565         return calculated_xstate_size;
 566 }
 567
 568 /*
 569  * Will the runtime-enumerated 'xstate_size' fit in the init
 570  * task's statically-allocated buffer?
 571  */
 572 static bool is_supported_xstate_size(unsigned int test_xstate_size)
 573 {
 574         if (test_xstate_size <= sizeof(union fpregs_state))
 575                 return true;
 576
 577         pr_warn("x86/fpu: xstate buffer too small (%zu < %d), disabling xsave\n",
 578                         sizeof(union fpregs_state), test_xstate_size);
 579         return false;
 580 }
 581
 582 static int init_xstate_size(void)
 583 {
 584         /* Recompute the context size for enabled features: */
 585         unsigned int possible_xstate_size = calculate_xstate_size();
 586
 587         /* Ensure we have the space to store all enabled: */
 588         if (!is_supported_xstate_size(possible_xstate_size))
 589                 return -EINVAL;
 590
 591         /*
 592          * The size is OK, we are definitely going to use xsave,
 593          * make it known to the world that we need more space.
 594          */
 595         xstate_size = possible_xstate_size;
 596         do_extra_xstate_size_checks();
 597         return 0;
 598 }
 599
 600 /*
 601  * We enabled the XSAVE hardware, but something went wrong and
 602  * we can not use it.  Disable it.
 603  */
 604 static void fpu__init_disable_system_xstate(void)
 605 {
 606         xfeatures_mask = 0;
 607         cr4_clear_bits(X86_CR4_OSXSAVE);
 608         fpu__xstate_clear_all_cpu_caps();
 609 }
 610
 611 /*
 612  * Enable and initialize the xsave feature.
 613  * Called once per system bootup.
 614  */
 615 void __init fpu__init_system_xstate(void)
 616 {
 617         unsigned int eax, ebx, ecx, edx;
 618         static int on_boot_cpu __initdata = 1;
 619         int err;
 620
 621         WARN_ON_FPU(!on_boot_cpu);
 622         on_boot_cpu = 0;
 623
 624         if (!cpu_has_xsave) {
 625                 pr_info("x86/fpu: Legacy x87 FPU detected.\n");
 626                 return;
 627         }
 628
 629         if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
 630                 WARN_ON_FPU(1);
 631                 return;
 632         }
 633
 634         cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 635         xfeatures_mask = eax + ((u64)edx << 32);
 636
 637         if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
 638                 pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
 639                 BUG();
 640         }
 641
 642         xfeatures_mask &= fpu__get_supported_xfeatures_mask();
 643
 644         /* Enable xstate instructions to be able to continue with initialization: */
 645         fpu__init_cpu_xstate();
 646         err = init_xstate_size();
 647         if (err) {
 648                 /* something went wrong, boot without any XSAVE support */
 649                 fpu__init_disable_system_xstate();
 650                 return;
 651         }
 652
 653         update_regset_xstate_info(xstate_size, xfeatures_mask);
 654         fpu__init_prepare_fx_sw_frame();
 655         setup_init_fpu_buf();
 656         setup_xstate_comp();
 657
 658         pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
 659                 xfeatures_mask,
 660                 xstate_size,
 661                 cpu_has_xsaves ? "compacted" : "standard");
 662 }
 663
 664 /*
 665  * Restore minimal FPU state after suspend:
 666  */
 667 void fpu__resume_cpu(void)
 668 {
 669         /*
 670          * Restore XCR0 on xsave capable CPUs:
 671          */
 672         if (cpu_has_xsave)
 673                 xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 674 }
 675
 676 /*
 677  * Given the xsave area and a state inside, this function returns the
 678  * address of the state.
 679  *
 680  * This is the API that is called to get xstate address in either
 681  * standard format or compacted format of xsave area.
 682  *
 683  * Note that if there is no data for the field in the xsave buffer
 684  * this will return NULL.
 685  *
 686  * Inputs:
 687  *      xstate: the thread's storage area for all FPU data
 688  *      xstate_feature: state which is defined in xsave.h (e.g.
 689  *      XFEATURE_MASK_FP, XFEATURE_MASK_SSE, etc...)
 690  * Output:
 691  *      address of the state in the xsave area, or NULL if the
 692  *      field is not present in the xsave buffer.
 693  */
 694 void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
 695 {
 696         int feature_nr = fls64(xstate_feature) - 1;
 697         /*
 698          * Do we even *have* xsave state?
 699          */
 700         if (!boot_cpu_has(X86_FEATURE_XSAVE))
 701                 return NULL;
 702
 703         /*
 704          * We should not ever be requesting features that we
 705          * have not enabled.  Remember that pcntxt_mask is
 706          * what we write to the XCR0 register.
 707          */
 708         WARN_ONCE(!(xfeatures_mask & xstate_feature),
 709                   "get of unsupported state");
 710         /*
 711          * This assumes the last 'xsave*' instruction to
 712          * have requested that 'xstate_feature' be saved.
 713          * If it did not, we might be seeing and old value
 714          * of the field in the buffer.
 715          *
 716          * This can happen because the last 'xsave' did not
 717          * request that this feature be saved (unlikely)
 718          * or because the "init optimization" caused it
 719          * to not be saved.
 720          */
 721         if (!(xsave->header.xfeatures & xstate_feature))
 722                 return NULL;
 723
 724         return (void *)xsave + xstate_comp_offsets[feature_nr];
 725 }
 726 EXPORT_SYMBOL_GPL(get_xsave_addr);
 727
 728 /*
 729  * This wraps up the common operations that need to occur when retrieving
 730  * data from xsave state.  It first ensures that the current task was
 731  * using the FPU and retrieves the data in to a buffer.  It then calculates
 732  * the offset of the requested field in the buffer.
 733  *
 734  * This function is safe to call whether the FPU is in use or not.
 735  *
 736  * Note that this only works on the current task.
 737  *
 738  * Inputs:
 739  *      @xsave_state: state which is defined in xsave.h (e.g. XFEATURE_MASK_FP,
 740  *      XFEATURE_MASK_SSE, etc...)
 741  * Output:
 742  *      address of the state in the xsave area or NULL if the state
 743  *      is not present or is in its 'init state'.
 744  */
 745 const void *get_xsave_field_ptr(int xsave_state)
 746 {
 747         struct fpu *fpu = &current->thread.fpu;
 748
 749         if (!fpu->fpstate_active)
 750                 return NULL;
 751         /*
 752          * fpu__save() takes the CPU's xstate registers
 753          * and saves them off to the 'fpu memory buffer.
 754          */
 755         fpu__save(fpu);
 756
 757         return get_xsave_addr(&fpu->state.xsave, xsave_state);
 758 }