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[XFEATURES_NR_MAX] = { [ 0 ... XFEATURES_NR_MAX - 1] = -1};
  35 static unsigned int xstate_sizes[XFEATURES_NR_MAX]   = { [ 0 ... XFEATURES_NR_MAX - 1] = -1};
  36 static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8];
  37
  38 /* The number of supported xfeatures in xfeatures_mask: */
  39 static unsigned int xfeatures_nr;
  40
  41 /*
  42  * Return whether the system supports a given xfeature.
  43  *
  44  * Also return the name of the (most advanced) feature that the caller requested:
  45  */
  46 int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name)
  47 {
  48         u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask;
  49
  50         if (unlikely(feature_name)) {
  51                 long xfeature_idx, max_idx;
  52                 u64 xfeatures_print;
  53                 /*
  54                  * So we use FLS here to be able to print the most advanced
  55                  * feature that was requested but is missing. So if a driver
  56                  * asks about "XSTATE_SSE | XSTATE_YMM" we'll print the
  57                  * missing AVX feature - this is the most informative message
  58                  * to users:
  59                  */
  60                 if (xfeatures_missing)
  61                         xfeatures_print = xfeatures_missing;
  62                 else
  63                         xfeatures_print = xfeatures_needed;
  64
  65                 xfeature_idx = fls64(xfeatures_print)-1;
  66                 max_idx = ARRAY_SIZE(xfeature_names)-1;
  67                 xfeature_idx = min(xfeature_idx, max_idx);
  68
  69                 *feature_name = xfeature_names[xfeature_idx];
  70         }
  71
  72         if (xfeatures_missing)
  73                 return 0;
  74
  75         return 1;
  76 }
  77 EXPORT_SYMBOL_GPL(cpu_has_xfeatures);
  78
  79 /*
  80  * When executing XSAVEOPT (or other optimized XSAVE instructions), if
  81  * a processor implementation detects that an FPU state component is still
  82  * (or is again) in its initialized state, it may clear the corresponding
  83  * bit in the header.xfeatures field, and can skip the writeout of registers
  84  * to the corresponding memory layout.
  85  *
  86  * This means that when the bit is zero, the state component might still contain
  87  * some previous - non-initialized register state.
  88  *
  89  * Before writing xstate information to user-space we sanitize those components,
  90  * to always ensure that the memory layout of a feature will be in the init state
  91  * if the corresponding header bit is zero. This is to ensure that user-space doesn't
  92  * see some stale state in the memory layout during signal handling, debugging etc.
  93  */
  94 void fpstate_sanitize_xstate(struct fpu *fpu)
  95 {
  96         struct fxregs_state *fx = &fpu->state.fxsave;
  97         int feature_bit;
  98         u64 xfeatures;
  99
 100         if (!use_xsaveopt())
 101                 return;
 102
 103         xfeatures = fpu->state.xsave.header.xfeatures;
 104
 105         /*
 106          * None of the feature bits are in init state. So nothing else
 107          * to do for us, as the memory layout is up to date.
 108          */
 109         if ((xfeatures & xfeatures_mask) == xfeatures_mask)
 110                 return;
 111
 112         /*
 113          * FP is in init state
 114          */
 115         if (!(xfeatures & XSTATE_FP)) {
 116                 fx->cwd = 0x37f;
 117                 fx->swd = 0;
 118                 fx->twd = 0;
 119                 fx->fop = 0;
 120                 fx->rip = 0;
 121                 fx->rdp = 0;
 122                 memset(&fx->st_space[0], 0, 128);
 123         }
 124
 125         /*
 126          * SSE is in init state
 127          */
 128         if (!(xfeatures & XSTATE_SSE))
 129                 memset(&fx->xmm_space[0], 0, 256);
 130
 131         /*
 132          * First two features are FPU and SSE, which above we handled
 133          * in a special way already:
 134          */
 135         feature_bit = 0x2;
 136         xfeatures = (xfeatures_mask & ~xfeatures) >> 2;
 137
 138         /*
 139          * Update all the remaining memory layouts according to their
 140          * standard xstate layout, if their header bit is in the init
 141          * state:
 142          */
 143         while (xfeatures) {
 144                 if (xfeatures & 0x1) {
 145                         int offset = xstate_offsets[feature_bit];
 146                         int size = xstate_sizes[feature_bit];
 147
 148                         memcpy((void *)fx + offset,
 149                                (void *)&init_fpstate.xsave + offset,
 150                                size);
 151                 }
 152
 153                 xfeatures >>= 1;
 154                 feature_bit++;
 155         }
 156 }
 157
 158 /*
 159  * Enable the extended processor state save/restore feature.
 160  * Called once per CPU onlining.
 161  */
 162 void fpu__init_cpu_xstate(void)
 163 {
 164         if (!cpu_has_xsave || !xfeatures_mask)
 165                 return;
 166
 167         cr4_set_bits(X86_CR4_OSXSAVE);
 168         xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 169 }
 170
 171 /*
 172  * Record the offsets and sizes of various xstates contained
 173  * in the XSAVE state memory layout.
 174  *
 175  * ( Note that certain features might be non-present, for them
 176  *   we'll have 0 offset and 0 size. )
 177  */
 178 static void __init setup_xstate_features(void)
 179 {
 180         u32 eax, ebx, ecx, edx, leaf;
 181
 182         xfeatures_nr = fls64(xfeatures_mask);
 183
 184         for (leaf = 2; leaf < xfeatures_nr; leaf++) {
 185                 cpuid_count(XSTATE_CPUID, leaf, &eax, &ebx, &ecx, &edx);
 186
 187                 xstate_offsets[leaf] = ebx;
 188                 xstate_sizes[leaf] = eax;
 189
 190                 printk(KERN_INFO "x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n", leaf, ebx, leaf, eax);
 191         }
 192 }
 193
 194 static void __init print_xstate_feature(u64 xstate_mask)
 195 {
 196         const char *feature_name;
 197
 198         if (cpu_has_xfeatures(xstate_mask, &feature_name))
 199                 pr_info("x86/fpu: Supporting XSAVE feature 0x%02Lx: '%s'\n", xstate_mask, feature_name);
 200 }
 201
 202 /*
 203  * Print out all the supported xstate features:
 204  */
 205 static void __init print_xstate_features(void)
 206 {
 207         print_xstate_feature(XSTATE_FP);
 208         print_xstate_feature(XSTATE_SSE);
 209         print_xstate_feature(XSTATE_YMM);
 210         print_xstate_feature(XSTATE_BNDREGS);
 211         print_xstate_feature(XSTATE_BNDCSR);
 212         print_xstate_feature(XSTATE_OPMASK);
 213         print_xstate_feature(XSTATE_ZMM_Hi256);
 214         print_xstate_feature(XSTATE_Hi16_ZMM);
 215 }
 216
 217 /*
 218  * This function sets up offsets and sizes of all extended states in
 219  * xsave area. This supports both standard format and compacted format
 220  * of the xsave aread.
 221  */
 222 static void __init setup_xstate_comp(void)
 223 {
 224         unsigned int xstate_comp_sizes[sizeof(xfeatures_mask)*8];
 225         int i;
 226
 227         /*
 228          * The FP xstates and SSE xstates are legacy states. They are always
 229          * in the fixed offsets in the xsave area in either compacted form
 230          * or standard form.
 231          */
 232         xstate_comp_offsets[0] = 0;
 233         xstate_comp_offsets[1] = offsetof(struct fxregs_state, xmm_space);
 234
 235         if (!cpu_has_xsaves) {
 236                 for (i = 2; i < xfeatures_nr; i++) {
 237                         if (test_bit(i, (unsigned long *)&xfeatures_mask)) {
 238                                 xstate_comp_offsets[i] = xstate_offsets[i];
 239                                 xstate_comp_sizes[i] = xstate_sizes[i];
 240                         }
 241                 }
 242                 return;
 243         }
 244
 245         xstate_comp_offsets[2] = FXSAVE_SIZE + XSAVE_HDR_SIZE;
 246
 247         for (i = 2; i < xfeatures_nr; i++) {
 248                 if (test_bit(i, (unsigned long *)&xfeatures_mask))
 249                         xstate_comp_sizes[i] = xstate_sizes[i];
 250                 else
 251                         xstate_comp_sizes[i] = 0;
 252
 253                 if (i > 2)
 254                         xstate_comp_offsets[i] = xstate_comp_offsets[i-1]
 255                                         + xstate_comp_sizes[i-1];
 256
 257         }
 258 }
 259
 260 /*
 261  * setup the xstate image representing the init state
 262  */
 263 static void __init setup_init_fpu_buf(void)
 264 {
 265         static int on_boot_cpu = 1;
 266
 267         WARN_ON_FPU(!on_boot_cpu);
 268         on_boot_cpu = 0;
 269
 270         if (!cpu_has_xsave)
 271                 return;
 272
 273         setup_xstate_features();
 274         print_xstate_features();
 275
 276         if (cpu_has_xsaves) {
 277                 init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
 278                 init_fpstate.xsave.header.xfeatures = xfeatures_mask;
 279         }
 280
 281         /*
 282          * Init all the features state with header_bv being 0x0
 283          */
 284         copy_kernel_to_xregs_booting(&init_fpstate.xsave);
 285
 286         /*
 287          * Dump the init state again. This is to identify the init state
 288          * of any feature which is not represented by all zero's.
 289          */
 290         copy_xregs_to_kernel_booting(&init_fpstate.xsave);
 291 }
 292
 293 /*
 294  * Calculate total size of enabled xstates in XCR0/xfeatures_mask.
 295  */
 296 static void __init init_xstate_size(void)
 297 {
 298         unsigned int eax, ebx, ecx, edx;
 299         int i;
 300
 301         if (!cpu_has_xsaves) {
 302                 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 303                 xstate_size = ebx;
 304                 return;
 305         }
 306
 307         xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
 308         for (i = 2; i < 64; i++) {
 309                 if (test_bit(i, (unsigned long *)&xfeatures_mask)) {
 310                         cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 311                         xstate_size += eax;
 312                 }
 313         }
 314 }
 315
 316 /*
 317  * Enable and initialize the xsave feature.
 318  * Called once per system bootup.
 319  */
 320 void __init fpu__init_system_xstate(void)
 321 {
 322         unsigned int eax, ebx, ecx, edx;
 323         static int on_boot_cpu = 1;
 324
 325         WARN_ON_FPU(!on_boot_cpu);
 326         on_boot_cpu = 0;
 327
 328         if (!cpu_has_xsave) {
 329                 pr_info("x86/fpu: Legacy x87 FPU detected.\n");
 330                 return;
 331         }
 332
 333         if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
 334                 WARN_ON_FPU(1);
 335                 return;
 336         }
 337
 338         cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 339         xfeatures_mask = eax + ((u64)edx << 32);
 340
 341         if ((xfeatures_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
 342                 pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
 343                 BUG();
 344         }
 345
 346         /* Support only the state known to the OS: */
 347         xfeatures_mask = xfeatures_mask & XCNTXT_MASK;
 348
 349         /* Enable xstate instructions to be able to continue with initialization: */
 350         fpu__init_cpu_xstate();
 351
 352         /* Recompute the context size for enabled features: */
 353         init_xstate_size();
 354
 355         update_regset_xstate_info(xstate_size, xfeatures_mask);
 356         fpu__init_prepare_fx_sw_frame();
 357         setup_init_fpu_buf();
 358         setup_xstate_comp();
 359
 360         pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
 361                 xfeatures_mask,
 362                 xstate_size,
 363                 cpu_has_xsaves ? "compacted" : "standard");
 364 }
 365
 366 /*
 367  * Restore minimal FPU state after suspend:
 368  */
 369 void fpu__resume_cpu(void)
 370 {
 371         /*
 372          * Restore XCR0 on xsave capable CPUs:
 373          */
 374         if (cpu_has_xsave)
 375                 xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 376 }
 377
 378 /*
 379  * Given the xsave area and a state inside, this function returns the
 380  * address of the state.
 381  *
 382  * This is the API that is called to get xstate address in either
 383  * standard format or compacted format of xsave area.
 384  *
 385  * Note that if there is no data for the field in the xsave buffer
 386  * this will return NULL.
 387  *
 388  * Inputs:
 389  *      xstate: the thread's storage area for all FPU data
 390  *      xstate_feature: state which is defined in xsave.h (e.g.
 391  *      XSTATE_FP, XSTATE_SSE, etc...)
 392  * Output:
 393  *      address of the state in the xsave area, or NULL if the
 394  *      field is not present in the xsave buffer.
 395  */
 396 void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
 397 {
 398         int feature_nr = fls64(xstate_feature) - 1;
 399         /*
 400          * Do we even *have* xsave state?
 401          */
 402         if (!boot_cpu_has(X86_FEATURE_XSAVE))
 403                 return NULL;
 404
 405         xsave = &current->thread.fpu.state.xsave;
 406         /*
 407          * We should not ever be requesting features that we
 408          * have not enabled.  Remember that pcntxt_mask is
 409          * what we write to the XCR0 register.
 410          */
 411         WARN_ONCE(!(xfeatures_mask & xstate_feature),
 412                   "get of unsupported state");
 413         /*
 414          * This assumes the last 'xsave*' instruction to
 415          * have requested that 'xstate_feature' be saved.
 416          * If it did not, we might be seeing and old value
 417          * of the field in the buffer.
 418          *
 419          * This can happen because the last 'xsave' did not
 420          * request that this feature be saved (unlikely)
 421          * or because the "init optimization" caused it
 422          * to not be saved.
 423          */
 424         if (!(xsave->header.xfeatures & xstate_feature))
 425                 return NULL;
 426
 427         return (void *)xsave + xstate_comp_offsets[feature_nr];
 428 }
 429 EXPORT_SYMBOL_GPL(get_xsave_addr);
 430
 431 /*
 432  * This wraps up the common operations that need to occur when retrieving
 433  * data from xsave state.  It first ensures that the current task was
 434  * using the FPU and retrieves the data in to a buffer.  It then calculates
 435  * the offset of the requested field in the buffer.
 436  *
 437  * This function is safe to call whether the FPU is in use or not.
 438  *
 439  * Note that this only works on the current task.
 440  *
 441  * Inputs:
 442  *      @xsave_state: state which is defined in xsave.h (e.g. XSTATE_FP,
 443  *      XSTATE_SSE, etc...)
 444  * Output:
 445  *      address of the state in the xsave area or NULL if the state
 446  *      is not present or is in its 'init state'.
 447  */
 448 const void *get_xsave_field_ptr(int xsave_state)
 449 {
 450         struct fpu *fpu = &current->thread.fpu;
 451
 452         if (!fpu->fpstate_active)
 453                 return NULL;
 454         /*
 455          * fpu__save() takes the CPU's xstate registers
 456          * and saves them off to the 'fpu memory buffer.
 457          */
 458         fpu__save(fpu);
 459
 460         return get_xsave_addr(&fpu->state.xsave, xsave_state);
 461 }