arch/i386/kernel/cpu/common.c

   1 #include <linux/init.h>
   2 #include <linux/string.h>
   3 #include <linux/delay.h>
   4 #include <linux/smp.h>
   5 #include <linux/module.h>
   6 #include <linux/percpu.h>
   7 #include <asm/semaphore.h>
   8 #include <asm/processor.h>
   9 #include <asm/i387.h>
  10 #include <asm/msr.h>
  11 #include <asm/io.h>
  12 #include <asm/mmu_context.h>
  13 #ifdef CONFIG_X86_LOCAL_APIC
  14 #include <asm/mpspec.h>
  15 #include <asm/apic.h>
  16 #include <mach_apic.h>
  17 #endif
  18
  19 #include "cpu.h"
  20
  21 DEFINE_PER_CPU(struct desc_struct, cpu_gdt_table[GDT_ENTRIES]);
  22 EXPORT_PER_CPU_SYMBOL(cpu_gdt_table);
  23
  24 DEFINE_PER_CPU(unsigned char, cpu_16bit_stack[CPU_16BIT_STACK_SIZE]);
  25 EXPORT_PER_CPU_SYMBOL(cpu_16bit_stack);
  26
  27 static int cachesize_override __initdata = -1;
  28 static int disable_x86_fxsr __initdata = 0;
  29 static int disable_x86_serial_nr __initdata = 1;
  30
  31 struct cpu_dev * cpu_devs[X86_VENDOR_NUM] = {};
  32
  33 extern void mcheck_init(struct cpuinfo_x86 *c);
  34
  35 extern int disable_pse;
  36
  37 static void default_init(struct cpuinfo_x86 * c)
  38 {
  39         /* Not much we can do here... */
  40         /* Check if at least it has cpuid */
  41         if (c->cpuid_level == -1) {
  42                 /* No cpuid. It must be an ancient CPU */
  43                 if (c->x86 == 4)
  44                         strcpy(c->x86_model_id, "486");
  45                 else if (c->x86 == 3)
  46                         strcpy(c->x86_model_id, "386");
  47         }
  48 }
  49
  50 static struct cpu_dev default_cpu = {
  51         .c_init = default_init,
  52 };
  53 static struct cpu_dev * this_cpu = &default_cpu;
  54
  55 static int __init cachesize_setup(char *str)
  56 {
  57         get_option (&str, &cachesize_override);
  58         return 1;
  59 }
  60 __setup("cachesize=", cachesize_setup);
  61
  62 int __init get_model_name(struct cpuinfo_x86 *c)
  63 {
  64         unsigned int *v;
  65         char *p, *q;
  66
  67         if (cpuid_eax(0x80000000) < 0x80000004)
  68                 return 0;
  69
  70         v = (unsigned int *) c->x86_model_id;
  71         cpuid(0x80000002, &v[0], &v[1], &v[2], &v[3]);
  72         cpuid(0x80000003, &v[4], &v[5], &v[6], &v[7]);
  73         cpuid(0x80000004, &v[8], &v[9], &v[10], &v[11]);
  74         c->x86_model_id[48] = 0;
  75
  76         /* Intel chips right-justify this string for some dumb reason;
  77            undo that brain damage */
  78         p = q = &c->x86_model_id[0];
  79         while ( *p == ' ' )
  80              p++;
  81         if ( p != q ) {
  82              while ( *p )
  83                   *q++ = *p++;
  84              while ( q <= &c->x86_model_id[48] )
  85                   *q++ = '\0';  /* Zero-pad the rest */
  86         }
  87
  88         return 1;
  89 }
  90
  91
  92 void __init display_cacheinfo(struct cpuinfo_x86 *c)
  93 {
  94         unsigned int n, dummy, ecx, edx, l2size;
  95
  96         n = cpuid_eax(0x80000000);
  97
  98         if (n >= 0x80000005) {
  99                 cpuid(0x80000005, &dummy, &dummy, &ecx, &edx);
 100                 printk(KERN_INFO "CPU: L1 I Cache: %dK (%d bytes/line), D cache %dK (%d bytes/line)\n",
 101                         edx>>24, edx&0xFF, ecx>>24, ecx&0xFF);
 102                 c->x86_cache_size=(ecx>>24)+(edx>>24);
 103         }
 104
 105         if (n < 0x80000006)     /* Some chips just has a large L1. */
 106                 return;
 107
 108         ecx = cpuid_ecx(0x80000006);
 109         l2size = ecx >> 16;
 110
 111         /* do processor-specific cache resizing */
 112         if (this_cpu->c_size_cache)
 113                 l2size = this_cpu->c_size_cache(c,l2size);
 114
 115         /* Allow user to override all this if necessary. */
 116         if (cachesize_override != -1)
 117                 l2size = cachesize_override;
 118
 119         if ( l2size == 0 )
 120                 return;         /* Again, no L2 cache is possible */
 121
 122         c->x86_cache_size = l2size;
 123
 124         printk(KERN_INFO "CPU: L2 Cache: %dK (%d bytes/line)\n",
 125                l2size, ecx & 0xFF);
 126 }
 127
 128 /* Naming convention should be: <Name> [(<Codename>)] */
 129 /* This table only is used unless init_<vendor>() below doesn't set it; */
 130 /* in particular, if CPUID levels 0x80000002..4 are supported, this isn't used */
 131
 132 /* Look up CPU names by table lookup. */
 133 static char __init *table_lookup_model(struct cpuinfo_x86 *c)
 134 {
 135         struct cpu_model_info *info;
 136
 137         if ( c->x86_model >= 16 )
 138                 return NULL;    /* Range check */
 139
 140         if (!this_cpu)
 141                 return NULL;
 142
 143         info = this_cpu->c_models;
 144
 145         while (info && info->family) {
 146                 if (info->family == c->x86)
 147                         return info->model_names[c->x86_model];
 148                 info++;
 149         }
 150         return NULL;            /* Not found */
 151 }
 152
 153
 154 void __init get_cpu_vendor(struct cpuinfo_x86 *c, int early)
 155 {
 156         char *v = c->x86_vendor_id;
 157         int i;
 158
 159         for (i = 0; i < X86_VENDOR_NUM; i++) {
 160                 if (cpu_devs[i]) {
 161                         if (!strcmp(v,cpu_devs[i]->c_ident[0]) ||
 162                             (cpu_devs[i]->c_ident[1] &&
 163                              !strcmp(v,cpu_devs[i]->c_ident[1]))) {
 164                                 c->x86_vendor = i;
 165                                 if (!early)
 166                                         this_cpu = cpu_devs[i];
 167                                 break;
 168                         }
 169                 }
 170         }
 171 }
 172
 173
 174 static int __init x86_fxsr_setup(char * s)
 175 {
 176         disable_x86_fxsr = 1;
 177         return 1;
 178 }
 179 __setup("nofxsr", x86_fxsr_setup);
 180
 181
 182 /* Standard macro to see if a specific flag is changeable */
 183 static inline int flag_is_changeable_p(u32 flag)
 184 {
 185         u32 f1, f2;
 186
 187         asm("pushfl\n\t"
 188             "pushfl\n\t"
 189             "popl %0\n\t"
 190             "movl %0,%1\n\t"
 191             "xorl %2,%0\n\t"
 192             "pushl %0\n\t"
 193             "popfl\n\t"
 194             "pushfl\n\t"
 195             "popl %0\n\t"
 196             "popfl\n\t"
 197             : "=&r" (f1), "=&r" (f2)
 198             : "ir" (flag));
 199
 200         return ((f1^f2) & flag) != 0;
 201 }
 202
 203
 204 /* Probe for the CPUID instruction */
 205 static int __init have_cpuid_p(void)
 206 {
 207         return flag_is_changeable_p(X86_EFLAGS_ID);
 208 }
 209
 210 /* Do minimum CPU detection early.
 211    Fields really needed: vendor, cpuid_level, family, model, mask, cache alignment.
 212    The others are not touched to avoid unwanted side effects. */
 213 static void __init early_cpu_detect(void)
 214 {
 215         struct cpuinfo_x86 *c = &boot_cpu_data;
 216
 217         c->x86_cache_alignment = 32;
 218
 219         if (!have_cpuid_p())
 220                 return;
 221
 222         /* Get vendor name */
 223         cpuid(0x00000000, &c->cpuid_level,
 224               (int *)&c->x86_vendor_id[0],
 225               (int *)&c->x86_vendor_id[8],
 226               (int *)&c->x86_vendor_id[4]);
 227
 228         get_cpu_vendor(c, 1);
 229
 230         c->x86 = 4;
 231         if (c->cpuid_level >= 0x00000001) {
 232                 u32 junk, tfms, cap0, misc;
 233                 cpuid(0x00000001, &tfms, &misc, &junk, &cap0);
 234                 c->x86 = (tfms >> 8) & 15;
 235                 c->x86_model = (tfms >> 4) & 15;
 236                 if (c->x86 == 0xf) {
 237                         c->x86 += (tfms >> 20) & 0xff;
 238                         c->x86_model += ((tfms >> 16) & 0xF) << 4;
 239                 }
 240                 c->x86_mask = tfms & 15;
 241                 if (cap0 & (1<<19))
 242                         c->x86_cache_alignment = ((misc >> 8) & 0xff) * 8;
 243         }
 244
 245         early_intel_workaround(c);
 246 }
 247
 248 void __init generic_identify(struct cpuinfo_x86 * c)
 249 {
 250         u32 tfms, xlvl;
 251         int junk;
 252
 253         if (have_cpuid_p()) {
 254                 /* Get vendor name */
 255                 cpuid(0x00000000, &c->cpuid_level,
 256                       (int *)&c->x86_vendor_id[0],
 257                       (int *)&c->x86_vendor_id[8],
 258                       (int *)&c->x86_vendor_id[4]);
 259
 260                 get_cpu_vendor(c, 0);
 261                 /* Initialize the standard set of capabilities */
 262                 /* Note that the vendor-specific code below might override */
 263
 264                 /* Intel-defined flags: level 0x00000001 */
 265                 if ( c->cpuid_level >= 0x00000001 ) {
 266                         u32 capability, excap;
 267                         cpuid(0x00000001, &tfms, &junk, &excap, &capability);
 268                         c->x86_capability[0] = capability;
 269                         c->x86_capability[4] = excap;
 270                         c->x86 = (tfms >> 8) & 15;
 271                         c->x86_model = (tfms >> 4) & 15;
 272                         if (c->x86 == 0xf) {
 273                                 c->x86 += (tfms >> 20) & 0xff;
 274                                 c->x86_model += ((tfms >> 16) & 0xF) << 4;
 275                         }
 276                         c->x86_mask = tfms & 15;
 277                 } else {
 278                         /* Have CPUID level 0 only - unheard of */
 279                         c->x86 = 4;
 280                 }
 281
 282                 /* AMD-defined flags: level 0x80000001 */
 283                 xlvl = cpuid_eax(0x80000000);
 284                 if ( (xlvl & 0xffff0000) == 0x80000000 ) {
 285                         if ( xlvl >= 0x80000001 ) {
 286                                 c->x86_capability[1] = cpuid_edx(0x80000001);
 287                                 c->x86_capability[6] = cpuid_ecx(0x80000001);
 288                         }
 289                         if ( xlvl >= 0x80000004 )
 290                                 get_model_name(c); /* Default name */
 291                 }
 292         }
 293 }
 294
 295 static void __init squash_the_stupid_serial_number(struct cpuinfo_x86 *c)
 296 {
 297         if (cpu_has(c, X86_FEATURE_PN) && disable_x86_serial_nr ) {
 298                 /* Disable processor serial number */
 299                 unsigned long lo,hi;
 300                 rdmsr(MSR_IA32_BBL_CR_CTL,lo,hi);
 301                 lo |= 0x200000;
 302                 wrmsr(MSR_IA32_BBL_CR_CTL,lo,hi);
 303                 printk(KERN_NOTICE "CPU serial number disabled.\n");
 304                 clear_bit(X86_FEATURE_PN, c->x86_capability);
 305
 306                 /* Disabling the serial number may affect the cpuid level */
 307                 c->cpuid_level = cpuid_eax(0);
 308         }
 309 }
 310
 311 static int __init x86_serial_nr_setup(char *s)
 312 {
 313         disable_x86_serial_nr = 0;
 314         return 1;
 315 }
 316 __setup("serialnumber", x86_serial_nr_setup);
 317
 318
 319
 320 /*
 321  * This does the hard work of actually picking apart the CPU stuff...
 322  */
 323 void __init identify_cpu(struct cpuinfo_x86 *c)
 324 {
 325         int i;
 326
 327         c->loops_per_jiffy = loops_per_jiffy;
 328         c->x86_cache_size = -1;
 329         c->x86_vendor = X86_VENDOR_UNKNOWN;
 330         c->cpuid_level = -1;    /* CPUID not detected */
 331         c->x86_model = c->x86_mask = 0; /* So far unknown... */
 332         c->x86_vendor_id[0] = '\0'; /* Unset */
 333         c->x86_model_id[0] = '\0';  /* Unset */
 334         c->x86_num_cores = 1;
 335         memset(&c->x86_capability, 0, sizeof c->x86_capability);
 336
 337         if (!have_cpuid_p()) {
 338                 /* First of all, decide if this is a 486 or higher */
 339                 /* It's a 486 if we can modify the AC flag */
 340                 if ( flag_is_changeable_p(X86_EFLAGS_AC) )
 341                         c->x86 = 4;
 342                 else
 343                         c->x86 = 3;
 344         }
 345
 346         generic_identify(c);
 347
 348         printk(KERN_DEBUG "CPU: After generic identify, caps:");
 349         for (i = 0; i < NCAPINTS; i++)
 350                 printk(" %08lx", c->x86_capability[i]);
 351         printk("\n");
 352
 353         if (this_cpu->c_identify) {
 354                 this_cpu->c_identify(c);
 355
 356                 printk(KERN_DEBUG "CPU: After vendor identify, caps:");
 357                 for (i = 0; i < NCAPINTS; i++)
 358                         printk(" %08lx", c->x86_capability[i]);
 359                 printk("\n");
 360         }
 361
 362         /*
 363          * Vendor-specific initialization.  In this section we
 364          * canonicalize the feature flags, meaning if there are
 365          * features a certain CPU supports which CPUID doesn't
 366          * tell us, CPUID claiming incorrect flags, or other bugs,
 367          * we handle them here.
 368          *
 369          * At the end of this section, c->x86_capability better
 370          * indicate the features this CPU genuinely supports!
 371          */
 372         if (this_cpu->c_init)
 373                 this_cpu->c_init(c);
 374
 375         /* Disable the PN if appropriate */
 376         squash_the_stupid_serial_number(c);
 377
 378         /*
 379          * The vendor-specific functions might have changed features.  Now
 380          * we do "generic changes."
 381          */
 382
 383         /* TSC disabled? */
 384         if ( tsc_disable )
 385                 clear_bit(X86_FEATURE_TSC, c->x86_capability);
 386
 387         /* FXSR disabled? */
 388         if (disable_x86_fxsr) {
 389                 clear_bit(X86_FEATURE_FXSR, c->x86_capability);
 390                 clear_bit(X86_FEATURE_XMM, c->x86_capability);
 391         }
 392
 393         if (disable_pse)
 394                 clear_bit(X86_FEATURE_PSE, c->x86_capability);
 395
 396         /* If the model name is still unset, do table lookup. */
 397         if ( !c->x86_model_id[0] ) {
 398                 char *p;
 399                 p = table_lookup_model(c);
 400                 if ( p )
 401                         strcpy(c->x86_model_id, p);
 402                 else
 403                         /* Last resort... */
 404                         sprintf(c->x86_model_id, "%02x/%02x",
 405                                 c->x86_vendor, c->x86_model);
 406         }
 407
 408         /* Now the feature flags better reflect actual CPU features! */
 409
 410         printk(KERN_DEBUG "CPU: After all inits, caps:");
 411         for (i = 0; i < NCAPINTS; i++)
 412                 printk(" %08lx", c->x86_capability[i]);
 413         printk("\n");
 414
 415         /*
 416          * On SMP, boot_cpu_data holds the common feature set between
 417          * all CPUs; so make sure that we indicate which features are
 418          * common between the CPUs.  The first time this routine gets
 419          * executed, c == &boot_cpu_data.
 420          */
 421         if ( c != &boot_cpu_data ) {
 422                 /* AND the already accumulated flags with these */
 423                 for ( i = 0 ; i < NCAPINTS ; i++ )
 424                         boot_cpu_data.x86_capability[i] &= c->x86_capability[i];
 425         }
 426
 427         /* Init Machine Check Exception if available. */
 428 #ifdef CONFIG_X86_MCE
 429         mcheck_init(c);
 430 #endif
 431 }
 432
 433 #ifdef CONFIG_X86_HT
 434 void __init detect_ht(struct cpuinfo_x86 *c)
 435 {
 436         u32     eax, ebx, ecx, edx;
 437         int     index_lsb, index_msb, tmp;
 438         int     cpu = smp_processor_id();
 439
 440         if (!cpu_has(c, X86_FEATURE_HT))
 441                 return;
 442
 443         cpuid(1, &eax, &ebx, &ecx, &edx);
 444         smp_num_siblings = (ebx & 0xff0000) >> 16;
 445
 446         if (smp_num_siblings == 1) {
 447                 printk(KERN_INFO  "CPU: Hyper-Threading is disabled\n");
 448         } else if (smp_num_siblings > 1 ) {
 449                 index_lsb = 0;
 450                 index_msb = 31;
 451
 452                 if (smp_num_siblings > NR_CPUS) {
 453                         printk(KERN_WARNING "CPU: Unsupported number of the siblings %d", smp_num_siblings);
 454                         smp_num_siblings = 1;
 455                         return;
 456                 }
 457                 tmp = smp_num_siblings;
 458                 while ((tmp & 1) == 0) {
 459                         tmp >>=1 ;
 460                         index_lsb++;
 461                 }
 462                 tmp = smp_num_siblings;
 463                 while ((tmp & 0x80000000 ) == 0) {
 464                         tmp <<=1 ;
 465                         index_msb--;
 466                 }
 467                 if (index_lsb != index_msb )
 468                         index_msb++;
 469                 phys_proc_id[cpu] = phys_pkg_id((ebx >> 24) & 0xFF, index_msb);
 470
 471                 printk(KERN_INFO  "CPU: Physical Processor ID: %d\n",
 472                        phys_proc_id[cpu]);
 473         }
 474 }
 475 #endif
 476
 477 void __init print_cpu_info(struct cpuinfo_x86 *c)
 478 {
 479         char *vendor = NULL;
 480
 481         if (c->x86_vendor < X86_VENDOR_NUM)
 482                 vendor = this_cpu->c_vendor;
 483         else if (c->cpuid_level >= 0)
 484                 vendor = c->x86_vendor_id;
 485
 486         if (vendor && strncmp(c->x86_model_id, vendor, strlen(vendor)))
 487                 printk("%s ", vendor);
 488
 489         if (!c->x86_model_id[0])
 490                 printk("%d86", c->x86);
 491         else
 492                 printk("%s", c->x86_model_id);
 493
 494         if (c->x86_mask || c->cpuid_level >= 0)
 495                 printk(" stepping %02x\n", c->x86_mask);
 496         else
 497                 printk("\n");
 498 }
 499
 500 cpumask_t cpu_initialized __initdata = CPU_MASK_NONE;
 501
 502 /* This is hacky. :)
 503  * We're emulating future behavior.
 504  * In the future, the cpu-specific init functions will be called implicitly
 505  * via the magic of initcalls.
 506  * They will insert themselves into the cpu_devs structure.
 507  * Then, when cpu_init() is called, we can just iterate over that array.
 508  */
 509
 510 extern int intel_cpu_init(void);
 511 extern int cyrix_init_cpu(void);
 512 extern int nsc_init_cpu(void);
 513 extern int amd_init_cpu(void);
 514 extern int centaur_init_cpu(void);
 515 extern int transmeta_init_cpu(void);
 516 extern int rise_init_cpu(void);
 517 extern int nexgen_init_cpu(void);
 518 extern int umc_init_cpu(void);
 519
 520 void __init early_cpu_init(void)
 521 {
 522         intel_cpu_init();
 523         cyrix_init_cpu();
 524         nsc_init_cpu();
 525         amd_init_cpu();
 526         centaur_init_cpu();
 527         transmeta_init_cpu();
 528         rise_init_cpu();
 529         nexgen_init_cpu();
 530         umc_init_cpu();
 531         early_cpu_detect();
 532
 533 #ifdef CONFIG_DEBUG_PAGEALLOC
 534         /* pse is not compatible with on-the-fly unmapping,
 535          * disable it even if the cpus claim to support it.
 536          */
 537         clear_bit(X86_FEATURE_PSE, boot_cpu_data.x86_capability);
 538         disable_pse = 1;
 539 #endif
 540 }
 541 /*
 542  * cpu_init() initializes state that is per-CPU. Some data is already
 543  * initialized (naturally) in the bootstrap process, such as the GDT
 544  * and IDT. We reload them nevertheless, this function acts as a
 545  * 'CPU state barrier', nothing should get across.
 546  */
 547 void __init cpu_init (void)
 548 {
 549         int cpu = smp_processor_id();
 550         struct tss_struct * t = &per_cpu(init_tss, cpu);
 551         struct thread_struct *thread = &current->thread;
 552         __u32 stk16_off = (__u32)&per_cpu(cpu_16bit_stack, cpu);
 553
 554         if (cpu_test_and_set(cpu, cpu_initialized)) {
 555                 printk(KERN_WARNING "CPU#%d already initialized!\n", cpu);
 556                 for (;;) local_irq_enable();
 557         }
 558         printk(KERN_INFO "Initializing CPU#%d\n", cpu);
 559
 560         if (cpu_has_vme || cpu_has_tsc || cpu_has_de)
 561                 clear_in_cr4(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);
 562         if (tsc_disable && cpu_has_tsc) {
 563                 printk(KERN_NOTICE "Disabling TSC...\n");
 564                 /**** FIX-HPA: DOES THIS REALLY BELONG HERE? ****/
 565                 clear_bit(X86_FEATURE_TSC, boot_cpu_data.x86_capability);
 566                 set_in_cr4(X86_CR4_TSD);
 567         }
 568
 569         /*
 570          * Initialize the per-CPU GDT with the boot GDT,
 571          * and set up the GDT descriptor:
 572          */
 573         memcpy(&per_cpu(cpu_gdt_table, cpu), cpu_gdt_table,
 574                GDT_SIZE);
 575
 576         /* Set up GDT entry for 16bit stack */
 577         *(__u64 *)&(per_cpu(cpu_gdt_table, cpu)[GDT_ENTRY_ESPFIX_SS]) |=
 578                 ((((__u64)stk16_off) << 16) & 0x000000ffffff0000ULL) |
 579                 ((((__u64)stk16_off) << 32) & 0xff00000000000000ULL) |
 580                 (CPU_16BIT_STACK_SIZE - 1);
 581
 582         cpu_gdt_descr[cpu].size = GDT_SIZE - 1;
 583         cpu_gdt_descr[cpu].address =
 584             (unsigned long)&per_cpu(cpu_gdt_table, cpu);
 585
 586         /*
 587          * Set up the per-thread TLS descriptor cache:
 588          */
 589         memcpy(thread->tls_array, &per_cpu(cpu_gdt_table, cpu),
 590                 GDT_ENTRY_TLS_ENTRIES * 8);
 591
 592         __asm__ __volatile__("lgdt %0" : : "m" (cpu_gdt_descr[cpu]));
 593         __asm__ __volatile__("lidt %0" : : "m" (idt_descr));
 594
 595         /*
 596          * Delete NT
 597          */
 598         __asm__("pushfl ; andl $0xffffbfff,(%esp) ; popfl");
 599
 600         /*
 601          * Set up and load the per-CPU TSS and LDT
 602          */
 603         atomic_inc(&init_mm.mm_count);
 604         current->active_mm = &init_mm;
 605         if (current->mm)
 606                 BUG();
 607         enter_lazy_tlb(&init_mm, current);
 608
 609         load_esp0(t, thread);
 610         set_tss_desc(cpu,t);
 611         load_TR_desc();
 612         load_LDT(&init_mm.context);
 613
 614         /* Set up doublefault TSS pointer in the GDT */
 615         __set_tss_desc(cpu, GDT_ENTRY_DOUBLEFAULT_TSS, &doublefault_tss);
 616
 617         /* Clear %fs and %gs. */
 618         asm volatile ("xorl %eax, %eax; movl %eax, %fs; movl %eax, %gs");
 619
 620         /* Clear all 6 debug registers: */
 621
 622 #define CD(register) __asm__("movl %0,%%db" #register ::"r"(0) );
 623
 624         CD(0); CD(1); CD(2); CD(3); /* no db4 and db5 */; CD(6); CD(7);
 625
 626 #undef CD
 627
 628         /*
 629          * Force FPU initialization:
 630          */
 631         current_thread_info()->status = 0;
 632         clear_used_math();
 633         mxcsr_feature_mask_init();
 634 }