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  * setup the xstate image representing the init state
 297  */
 298 static void __init setup_init_fpu_buf(void)
 299 {
 300         static int on_boot_cpu = 1;
 301
 302         WARN_ON_FPU(!on_boot_cpu);
 303         on_boot_cpu = 0;
 304
 305         if (!cpu_has_xsave)
 306                 return;
 307
 308         setup_xstate_features();
 309         print_xstate_features();
 310
 311         if (cpu_has_xsaves) {
 312                 init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
 313                 init_fpstate.xsave.header.xfeatures = xfeatures_mask;
 314         }
 315
 316         /*
 317          * Init all the features state with header_bv being 0x0
 318          */
 319         copy_kernel_to_xregs_booting(&init_fpstate.xsave);
 320
 321         /*
 322          * Dump the init state again. This is to identify the init state
 323          * of any feature which is not represented by all zero's.
 324          */
 325         copy_xregs_to_kernel_booting(&init_fpstate.xsave);
 326 }
 327
 328 static int xfeature_is_supervisor(int xfeature_nr)
 329 {
 330         /*
 331          * We currently do not support supervisor states, but if
 332          * we did, we could find out like this.
 333          *
 334          * SDM says: If state component i is a user state component,
 335          * ECX[0] return 0; if state component i is a supervisor
 336          * state component, ECX[0] returns 1.
 337         u32 eax, ebx, ecx, edx;
 338         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx;
 339         return !!(ecx & 1);
 340         */
 341         return 0;
 342 }
 343 /*
 344 static int xfeature_is_user(int xfeature_nr)
 345 {
 346         return !xfeature_is_supervisor(xfeature_nr);
 347 }
 348 */
 349
 350 /*
 351  * This check is important because it is easy to get XSTATE_*
 352  * confused with XSTATE_BIT_*.
 353  */
 354 #define CHECK_XFEATURE(nr) do {         \
 355         WARN_ON(nr < FIRST_EXTENDED_XFEATURE);  \
 356         WARN_ON(nr >= XFEATURE_MAX);    \
 357 } while (0)
 358
 359 /*
 360  * We could cache this like xstate_size[], but we only use
 361  * it here, so it would be a waste of space.
 362  */
 363 static int xfeature_is_aligned(int xfeature_nr)
 364 {
 365         u32 eax, ebx, ecx, edx;
 366
 367         CHECK_XFEATURE(xfeature_nr);
 368         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 369         /*
 370          * The value returned by ECX[1] indicates the alignment
 371          * of state component i when the compacted format
 372          * of the extended region of an XSAVE area is used
 373          */
 374         return !!(ecx & 2);
 375 }
 376
 377 static int xfeature_uncompacted_offset(int xfeature_nr)
 378 {
 379         u32 eax, ebx, ecx, edx;
 380
 381         CHECK_XFEATURE(xfeature_nr);
 382         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 383         return ebx;
 384 }
 385
 386 static int xfeature_size(int xfeature_nr)
 387 {
 388         u32 eax, ebx, ecx, edx;
 389
 390         CHECK_XFEATURE(xfeature_nr);
 391         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 392         return eax;
 393 }
 394
 395 /*
 396  * 'XSAVES' implies two different things:
 397  * 1. saving of supervisor/system state
 398  * 2. using the compacted format
 399  *
 400  * Use this function when dealing with the compacted format so
 401  * that it is obvious which aspect of 'XSAVES' is being handled
 402  * by the calling code.
 403  */
 404 static int using_compacted_format(void)
 405 {
 406         return cpu_has_xsaves;
 407 }
 408
 409 static void __xstate_dump_leaves(void)
 410 {
 411         int i;
 412         u32 eax, ebx, ecx, edx;
 413         static int should_dump = 1;
 414
 415         if (!should_dump)
 416                 return;
 417         should_dump = 0;
 418         /*
 419          * Dump out a few leaves past the ones that we support
 420          * just in case there are some goodies up there
 421          */
 422         for (i = 0; i < XFEATURE_MAX + 10; i++) {
 423                 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 424                 pr_warn("CPUID[%02x, %02x]: eax=%08x ebx=%08x ecx=%08x edx=%08x\n",
 425                         XSTATE_CPUID, i, eax, ebx, ecx, edx);
 426         }
 427 }
 428
 429 #define XSTATE_WARN_ON(x) do {                                                  \
 430         if (WARN_ONCE(x, "XSAVE consistency problem, dumping leaves")) {        \
 431                 __xstate_dump_leaves();                                         \
 432         }                                                                       \
 433 } while (0)
 434
 435 #define XCHECK_SZ(sz, nr, nr_macro, __struct) do {                      \
 436         if ((nr == nr_macro) &&                                         \
 437             WARN_ONCE(sz != sizeof(__struct),                           \
 438                 "%s: struct is %zu bytes, cpu state %d bytes\n",        \
 439                 __stringify(nr_macro), sizeof(__struct), sz)) {         \
 440                 __xstate_dump_leaves();                                 \
 441         }                                                               \
 442 } while (0)
 443
 444 /*
 445  * We have a C struct for each 'xstate'.  We need to ensure
 446  * that our software representation matches what the CPU
 447  * tells us about the state's size.
 448  */
 449 static void check_xstate_against_struct(int nr)
 450 {
 451         /*
 452          * Ask the CPU for the size of the state.
 453          */
 454         int sz = xfeature_size(nr);
 455         /*
 456          * Match each CPU state with the corresponding software
 457          * structure.
 458          */
 459         XCHECK_SZ(sz, nr, XFEATURE_YMM,       struct ymmh_struct);
 460         XCHECK_SZ(sz, nr, XFEATURE_BNDREGS,   struct mpx_bndreg_state);
 461         XCHECK_SZ(sz, nr, XFEATURE_BNDCSR,    struct mpx_bndcsr_state);
 462         XCHECK_SZ(sz, nr, XFEATURE_OPMASK,    struct avx_512_opmask_state);
 463         XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);
 464         XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM,  struct avx_512_hi16_state);
 465
 466         /*
 467          * Make *SURE* to add any feature numbers in below if
 468          * there are "holes" in the xsave state component
 469          * numbers.
 470          */
 471         if ((nr < XFEATURE_YMM) ||
 472             (nr >= XFEATURE_MAX)) {
 473                 WARN_ONCE(1, "no structure for xstate: %d\n", nr);
 474                 XSTATE_WARN_ON(1);
 475         }
 476 }
 477
 478 /*
 479  * This essentially double-checks what the cpu told us about
 480  * how large the XSAVE buffer needs to be.  We are recalculating
 481  * it to be safe.
 482  */
 483 static void do_extra_xstate_size_checks(void)
 484 {
 485         int paranoid_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
 486         int i;
 487
 488         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 489                 if (!xfeature_enabled(i))
 490                         continue;
 491
 492                 check_xstate_against_struct(i);
 493                 /*
 494                  * Supervisor state components can be managed only by
 495                  * XSAVES, which is compacted-format only.
 496                  */
 497                 if (!using_compacted_format())
 498                         XSTATE_WARN_ON(xfeature_is_supervisor(i));
 499
 500                 /* Align from the end of the previous feature */
 501                 if (xfeature_is_aligned(i))
 502                         paranoid_xstate_size = ALIGN(paranoid_xstate_size, 64);
 503                 /*
 504                  * The offset of a given state in the non-compacted
 505                  * format is given to us in a CPUID leaf.  We check
 506                  * them for being ordered (increasing offsets) in
 507                  * setup_xstate_features().
 508                  */
 509                 if (!using_compacted_format())
 510                         paranoid_xstate_size = xfeature_uncompacted_offset(i);
 511                 /*
 512                  * The compacted-format offset always depends on where
 513                  * the previous state ended.
 514                  */
 515                 paranoid_xstate_size += xfeature_size(i);
 516         }
 517         XSTATE_WARN_ON(paranoid_xstate_size != xstate_size);
 518 }
 519
 520 /*
 521  * Calculate total size of enabled xstates in XCR0/xfeatures_mask.
 522  *
 523  * Note the SDM's wording here.  "sub-function 0" only enumerates
 524  * the size of the *user* states.  If we use it to size a buffer
 525  * that we use 'XSAVES' on, we could potentially overflow the
 526  * buffer because 'XSAVES' saves system states too.
 527  *
 528  * Note that we do not currently set any bits on IA32_XSS so
 529  * 'XCR0 | IA32_XSS == XCR0' for now.
 530  */
 531 static unsigned int __init calculate_xstate_size(void)
 532 {
 533         unsigned int eax, ebx, ecx, edx;
 534         unsigned int calculated_xstate_size;
 535
 536         if (!cpu_has_xsaves) {
 537                 /*
 538                  * - CPUID function 0DH, sub-function 0:
 539                  *    EBX enumerates the size (in bytes) required by
 540                  *    the XSAVE instruction for an XSAVE area
 541                  *    containing all the *user* state components
 542                  *    corresponding to bits currently set in XCR0.
 543                  */
 544                 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 545                 calculated_xstate_size = ebx;
 546         } else {
 547                 /*
 548                  * - CPUID function 0DH, sub-function 1:
 549                  *    EBX enumerates the size (in bytes) required by
 550                  *    the XSAVES instruction for an XSAVE area
 551                  *    containing all the state components
 552                  *    corresponding to bits currently set in
 553                  *    XCR0 | IA32_XSS.
 554                  */
 555                 cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
 556                 calculated_xstate_size = ebx;
 557         }
 558         return calculated_xstate_size;
 559 }
 560
 561 /*
 562  * Will the runtime-enumerated 'xstate_size' fit in the init
 563  * task's statically-allocated buffer?
 564  */
 565 static bool is_supported_xstate_size(unsigned int test_xstate_size)
 566 {
 567         if (test_xstate_size <= sizeof(union fpregs_state))
 568                 return true;
 569
 570         pr_warn("x86/fpu: xstate buffer too small (%zu < %d), disabling xsave\n",
 571                         sizeof(union fpregs_state), test_xstate_size);
 572         return false;
 573 }
 574
 575 static int init_xstate_size(void)
 576 {
 577         /* Recompute the context size for enabled features: */
 578         unsigned int possible_xstate_size = calculate_xstate_size();
 579
 580         /* Ensure we have the space to store all enabled: */
 581         if (!is_supported_xstate_size(possible_xstate_size))
 582                 return -EINVAL;
 583
 584         /*
 585          * The size is OK, we are definitely going to use xsave,
 586          * make it known to the world that we need more space.
 587          */
 588         xstate_size = possible_xstate_size;
 589         do_extra_xstate_size_checks();
 590         return 0;
 591 }
 592
 593 /*
 594  * We enabled the XSAVE hardware, but something went wrong and
 595  * we can not use it.  Disable it.
 596  */
 597 static void fpu__init_disable_system_xstate(void)
 598 {
 599         xfeatures_mask = 0;
 600         cr4_clear_bits(X86_CR4_OSXSAVE);
 601         fpu__xstate_clear_all_cpu_caps();
 602 }
 603
 604 /*
 605  * Enable and initialize the xsave feature.
 606  * Called once per system bootup.
 607  */
 608 void __init fpu__init_system_xstate(void)
 609 {
 610         unsigned int eax, ebx, ecx, edx;
 611         static int on_boot_cpu = 1;
 612         int err;
 613
 614         WARN_ON_FPU(!on_boot_cpu);
 615         on_boot_cpu = 0;
 616
 617         if (!cpu_has_xsave) {
 618                 pr_info("x86/fpu: Legacy x87 FPU detected.\n");
 619                 return;
 620         }
 621
 622         if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
 623                 WARN_ON_FPU(1);
 624                 return;
 625         }
 626
 627         cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 628         xfeatures_mask = eax + ((u64)edx << 32);
 629
 630         if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
 631                 pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
 632                 BUG();
 633         }
 634
 635         /* Support only the state known to the OS: */
 636         xfeatures_mask = xfeatures_mask & XCNTXT_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         xsave = &current->thread.fpu.state.xsave;
 698         /*
 699          * We should not ever be requesting features that we
 700          * have not enabled.  Remember that pcntxt_mask is
 701          * what we write to the XCR0 register.
 702          */
 703         WARN_ONCE(!(xfeatures_mask & xstate_feature),
 704                   "get of unsupported state");
 705         /*
 706          * This assumes the last 'xsave*' instruction to
 707          * have requested that 'xstate_feature' be saved.
 708          * If it did not, we might be seeing and old value
 709          * of the field in the buffer.
 710          *
 711          * This can happen because the last 'xsave' did not
 712          * request that this feature be saved (unlikely)
 713          * or because the "init optimization" caused it
 714          * to not be saved.
 715          */
 716         if (!(xsave->header.xfeatures & xstate_feature))
 717                 return NULL;
 718
 719         return (void *)xsave + xstate_comp_offsets[feature_nr];
 720 }
 721 EXPORT_SYMBOL_GPL(get_xsave_addr);
 722
 723 /*
 724  * This wraps up the common operations that need to occur when retrieving
 725  * data from xsave state.  It first ensures that the current task was
 726  * using the FPU and retrieves the data in to a buffer.  It then calculates
 727  * the offset of the requested field in the buffer.
 728  *
 729  * This function is safe to call whether the FPU is in use or not.
 730  *
 731  * Note that this only works on the current task.
 732  *
 733  * Inputs:
 734  *      @xsave_state: state which is defined in xsave.h (e.g. XFEATURE_MASK_FP,
 735  *      XFEATURE_MASK_SSE, etc...)
 736  * Output:
 737  *      address of the state in the xsave area or NULL if the state
 738  *      is not present or is in its 'init state'.
 739  */
 740 const void *get_xsave_field_ptr(int xsave_state)
 741 {
 742         struct fpu *fpu = &current->thread.fpu;
 743
 744         if (!fpu->fpstate_active)
 745                 return NULL;
 746         /*
 747          * fpu__save() takes the CPU's xstate registers
 748          * and saves them off to the 'fpu memory buffer.
 749          */
 750         fpu__save(fpu);
 751
 752         return get_xsave_addr(&fpu->state.xsave, xsave_state);
 753 }