Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6 into lvs-next-2.6

[mirror_ubuntu-artful-kernel.git] / arch / x86 / kernel / cpu / common.c

#include <linux/init.h>
#include <linux/string.h>
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/bootmem.h>
#include <asm/processor.h>
#include <asm/i387.h>
#include <asm/msr.h>
#include <asm/io.h>
#include <asm/mmu_context.h>
#include <asm/mtrr.h>
#include <asm/mce.h>
#include <asm/pat.h>
#include <asm/asm.h>
#ifdef CONFIG_X86_LOCAL_APIC
#include <asm/mpspec.h>
#include <asm/apic.h>
#include <mach_apic.h>
#endif

#include "cpu.h"

DEFINE_PER_CPU(struct gdt_page, gdt_page) = { .gdt = {
        [GDT_ENTRY_KERNEL_CS] = { { { 0x0000ffff, 0x00cf9a00 } } },
        [GDT_ENTRY_KERNEL_DS] = { { { 0x0000ffff, 0x00cf9200 } } },
        [GDT_ENTRY_DEFAULT_USER_CS] = { { { 0x0000ffff, 0x00cffa00 } } },
        [GDT_ENTRY_DEFAULT_USER_DS] = { { { 0x0000ffff, 0x00cff200 } } },
        /*
         * Segments used for calling PnP BIOS have byte granularity.
         * They code segments and data segments have fixed 64k limits,
         * the transfer segment sizes are set at run time.
         */
        /* 32-bit code */
        [GDT_ENTRY_PNPBIOS_CS32] = { { { 0x0000ffff, 0x00409a00 } } },
        /* 16-bit code */
        [GDT_ENTRY_PNPBIOS_CS16] = { { { 0x0000ffff, 0x00009a00 } } },
        /* 16-bit data */
        [GDT_ENTRY_PNPBIOS_DS] = { { { 0x0000ffff, 0x00009200 } } },
        /* 16-bit data */
        [GDT_ENTRY_PNPBIOS_TS1] = { { { 0x00000000, 0x00009200 } } },
        /* 16-bit data */
        [GDT_ENTRY_PNPBIOS_TS2] = { { { 0x00000000, 0x00009200 } } },
        /*
         * The APM segments have byte granularity and their bases
         * are set at run time.  All have 64k limits.
         */
        /* 32-bit code */
        [GDT_ENTRY_APMBIOS_BASE] = { { { 0x0000ffff, 0x00409a00 } } },
        /* 16-bit code */
        [GDT_ENTRY_APMBIOS_BASE+1] = { { { 0x0000ffff, 0x00009a00 } } },
        /* data */
        [GDT_ENTRY_APMBIOS_BASE+2] = { { { 0x0000ffff, 0x00409200 } } },

        [GDT_ENTRY_ESPFIX_SS] = { { { 0x00000000, 0x00c09200 } } },
        [GDT_ENTRY_PERCPU] = { { { 0x00000000, 0x00000000 } } },
} };
EXPORT_PER_CPU_SYMBOL_GPL(gdt_page);

__u32 cleared_cpu_caps[NCAPINTS] __cpuinitdata;

static int cachesize_override __cpuinitdata = -1;
static int disable_x86_serial_nr __cpuinitdata = 1;

struct cpu_dev *cpu_devs[X86_VENDOR_NUM] = {};

static void __cpuinit default_init(struct cpuinfo_x86 *c)
{
        /* Not much we can do here... */
        /* Check if at least it has cpuid */
        if (c->cpuid_level == -1) {
                /* No cpuid. It must be an ancient CPU */
                if (c->x86 == 4)
                        strcpy(c->x86_model_id, "486");
                else if (c->x86 == 3)
                        strcpy(c->x86_model_id, "386");
        }
}

static struct cpu_dev __cpuinitdata default_cpu = {
        .c_init = default_init,
        .c_vendor = "Unknown",
};
static struct cpu_dev *this_cpu __cpuinitdata = &default_cpu;

static int __init cachesize_setup(char *str)
{
        get_option(&str, &cachesize_override);
        return 1;
}
__setup("cachesize=", cachesize_setup);

int __cpuinit get_model_name(struct cpuinfo_x86 *c)
{
        unsigned int *v;
        char *p, *q;

        if (cpuid_eax(0x80000000) < 0x80000004)
                return 0;

        v = (unsigned int *) c->x86_model_id;
        cpuid(0x80000002, &v[0], &v[1], &v[2], &v[3]);
        cpuid(0x80000003, &v[4], &v[5], &v[6], &v[7]);
        cpuid(0x80000004, &v[8], &v[9], &v[10], &v[11]);
        c->x86_model_id[48] = 0;

        /* Intel chips right-justify this string for some dumb reason;
           undo that brain damage */
        p = q = &c->x86_model_id[0];
        while (*p == ' ')
             p++;
        if (p != q) {
             while (*p)
                  *q++ = *p++;
             while (q <= &c->x86_model_id[48])
                  *q++ = '\0';  /* Zero-pad the rest */
        }

        return 1;
}


void __cpuinit display_cacheinfo(struct cpuinfo_x86 *c)
{
        unsigned int n, dummy, ecx, edx, l2size;

        n = cpuid_eax(0x80000000);

        if (n >= 0x80000005) {
                cpuid(0x80000005, &dummy, &dummy, &ecx, &edx);
                printk(KERN_INFO "CPU: L1 I Cache: %dK (%d bytes/line), D cache %dK (%d bytes/line)\n",
                        edx>>24, edx&0xFF, ecx>>24, ecx&0xFF);
                c->x86_cache_size = (ecx>>24)+(edx>>24);
        }

        if (n < 0x80000006)     /* Some chips just has a large L1. */
                return;

        ecx = cpuid_ecx(0x80000006);
        l2size = ecx >> 16;

        /* do processor-specific cache resizing */
        if (this_cpu->c_size_cache)
                l2size = this_cpu->c_size_cache(c, l2size);

        /* Allow user to override all this if necessary. */
        if (cachesize_override != -1)
                l2size = cachesize_override;

        if (l2size == 0)
                return;         /* Again, no L2 cache is possible */

        c->x86_cache_size = l2size;

        printk(KERN_INFO "CPU: L2 Cache: %dK (%d bytes/line)\n",
               l2size, ecx & 0xFF);
}

/*
 * Naming convention should be: <Name> [(<Codename>)]
 * This table only is used unless init_<vendor>() below doesn't set it;
 * in particular, if CPUID levels 0x80000002..4 are supported, this isn't used
 *
 */

/* Look up CPU names by table lookup. */
static char __cpuinit *table_lookup_model(struct cpuinfo_x86 *c)
{
        struct cpu_model_info *info;

        if (c->x86_model >= 16)
                return NULL;    /* Range check */

        if (!this_cpu)
                return NULL;

        info = this_cpu->c_models;

        while (info && info->family) {
                if (info->family == c->x86)
                        return info->model_names[c->x86_model];
                info++;
        }
        return NULL;            /* Not found */
}


static void __cpuinit get_cpu_vendor(struct cpuinfo_x86 *c, int early)
{
        char *v = c->x86_vendor_id;
        int i;
        static int printed;

        for (i = 0; i < X86_VENDOR_NUM; i++) {
                if (cpu_devs[i]) {
                        if (!strcmp(v, cpu_devs[i]->c_ident[0]) ||
                            (cpu_devs[i]->c_ident[1] &&
                             !strcmp(v, cpu_devs[i]->c_ident[1]))) {
                                c->x86_vendor = i;
                                if (!early)
                                        this_cpu = cpu_devs[i];
                                return;
                        }
                }
        }
        if (!printed) {
                printed++;
                printk(KERN_ERR "CPU: Vendor unknown, using generic init.\n");
                printk(KERN_ERR "CPU: Your system may be unstable.\n");
        }
        c->x86_vendor = X86_VENDOR_UNKNOWN;
        this_cpu = &default_cpu;
}


static int __init x86_fxsr_setup(char *s)
{
        setup_clear_cpu_cap(X86_FEATURE_FXSR);
        setup_clear_cpu_cap(X86_FEATURE_XMM);
        return 1;
}
__setup("nofxsr", x86_fxsr_setup);


static int __init x86_sep_setup(char *s)
{
        setup_clear_cpu_cap(X86_FEATURE_SEP);
        return 1;
}
__setup("nosep", x86_sep_setup);


/* Standard macro to see if a specific flag is changeable */
static inline int flag_is_changeable_p(u32 flag)
{
        u32 f1, f2;

        asm("pushfl\n\t"
            "pushfl\n\t"
            "popl %0\n\t"
            "movl %0,%1\n\t"
            "xorl %2,%0\n\t"
            "pushl %0\n\t"
            "popfl\n\t"
            "pushfl\n\t"
            "popl %0\n\t"
            "popfl\n\t"
            : "=&r" (f1), "=&r" (f2)
            : "ir" (flag));

        return ((f1^f2) & flag) != 0;
}


/* Probe for the CPUID instruction */
static int __cpuinit have_cpuid_p(void)
{
        return flag_is_changeable_p(X86_EFLAGS_ID);
}

void __init cpu_detect(struct cpuinfo_x86 *c)
{
        /* Get vendor name */
        cpuid(0x00000000, (unsigned int *)&c->cpuid_level,
              (unsigned int *)&c->x86_vendor_id[0],
              (unsigned int *)&c->x86_vendor_id[8],
              (unsigned int *)&c->x86_vendor_id[4]);

        c->x86 = 4;
        if (c->cpuid_level >= 0x00000001) {
                u32 junk, tfms, cap0, misc;
                cpuid(0x00000001, &tfms, &misc, &junk, &cap0);
                c->x86 = (tfms >> 8) & 15;
                c->x86_model = (tfms >> 4) & 15;
                if (c->x86 == 0xf)
                        c->x86 += (tfms >> 20) & 0xff;
                if (c->x86 >= 0x6)
                        c->x86_model += ((tfms >> 16) & 0xF) << 4;
                c->x86_mask = tfms & 15;
                if (cap0 & (1<<19)) {
                        c->x86_cache_alignment = ((misc >> 8) & 0xff) * 8;
                        c->x86_clflush_size = ((misc >> 8) & 0xff) * 8;
                }
        }
}
static void __cpuinit early_get_cap(struct cpuinfo_x86 *c)
{
        u32 tfms, xlvl;
        unsigned int ebx;

        memset(&c->x86_capability, 0, sizeof c->x86_capability);
        if (have_cpuid_p()) {
                /* Intel-defined flags: level 0x00000001 */
                if (c->cpuid_level >= 0x00000001) {
                        u32 capability, excap;
                        cpuid(0x00000001, &tfms, &ebx, &excap, &capability);
                        c->x86_capability[0] = capability;
                        c->x86_capability[4] = excap;
                }

                /* AMD-defined flags: level 0x80000001 */
                xlvl = cpuid_eax(0x80000000);
                if ((xlvl & 0xffff0000) == 0x80000000) {
                        if (xlvl >= 0x80000001) {
                                c->x86_capability[1] = cpuid_edx(0x80000001);
                                c->x86_capability[6] = cpuid_ecx(0x80000001);
                        }
                }

        }

}

/*
 * Do minimum CPU detection early.
 * Fields really needed: vendor, cpuid_level, family, model, mask,
 * cache alignment.
 * The others are not touched to avoid unwanted side effects.
 *
 * WARNING: this function is only called on the BP.  Don't add code here
 * that is supposed to run on all CPUs.
 */
static void __init early_cpu_detect(void)
{
        struct cpuinfo_x86 *c = &boot_cpu_data;

        c->x86_cache_alignment = 32;
        c->x86_clflush_size = 32;

        if (!have_cpuid_p())
                return;

        cpu_detect(c);

        get_cpu_vendor(c, 1);

        early_get_cap(c);

        if (c->x86_vendor != X86_VENDOR_UNKNOWN &&
            cpu_devs[c->x86_vendor]->c_early_init)
                cpu_devs[c->x86_vendor]->c_early_init(c);
}

/*
 * The NOPL instruction is supposed to exist on all CPUs with
 * family >= 6, unfortunately, that's not true in practice because
 * of early VIA chips and (more importantly) broken virtualizers that
 * are not easy to detect.  Hence, probe for it based on first
 * principles.
 */
static void __cpuinit detect_nopl(struct cpuinfo_x86 *c)
{
        const u32 nopl_signature = 0x888c53b1; /* Random number */
        u32 has_nopl = nopl_signature;

        clear_cpu_cap(c, X86_FEATURE_NOPL);
        if (c->x86 >= 6) {
                asm volatile("\n"
                             "1:      .byte 0x0f,0x1f,0xc0\n" /* nopl %eax */
                             "2:\n"
                             "        .section .fixup,\"ax\"\n"
                             "3:      xor %0,%0\n"
                             "        jmp 2b\n"
                             "        .previous\n"
                             _ASM_EXTABLE(1b,3b)
                             : "+a" (has_nopl));

                if (has_nopl == nopl_signature)
                        set_cpu_cap(c, X86_FEATURE_NOPL);
        }
}

static void __cpuinit generic_identify(struct cpuinfo_x86 *c)
{
        u32 tfms, xlvl;
        unsigned int ebx;

        if (have_cpuid_p()) {
                /* Get vendor name */
                cpuid(0x00000000, (unsigned int *)&c->cpuid_level,
                      (unsigned int *)&c->x86_vendor_id[0],
                      (unsigned int *)&c->x86_vendor_id[8],
                      (unsigned int *)&c->x86_vendor_id[4]);

                get_cpu_vendor(c, 0);
                /* Initialize the standard set of capabilities */
                /* Note that the vendor-specific code below might override */
                /* Intel-defined flags: level 0x00000001 */
                if (c->cpuid_level >= 0x00000001) {
                        u32 capability, excap;
                        cpuid(0x00000001, &tfms, &ebx, &excap, &capability);
                        c->x86_capability[0] = capability;
                        c->x86_capability[4] = excap;
                        c->x86 = (tfms >> 8) & 15;
                        c->x86_model = (tfms >> 4) & 15;
                        if (c->x86 == 0xf)
                                c->x86 += (tfms >> 20) & 0xff;
                        if (c->x86 >= 0x6)
                                c->x86_model += ((tfms >> 16) & 0xF) << 4;
                        c->x86_mask = tfms & 15;
                        c->initial_apicid = (ebx >> 24) & 0xFF;
#ifdef CONFIG_X86_HT
                        c->apicid = phys_pkg_id(c->initial_apicid, 0);
                        c->phys_proc_id = c->initial_apicid;
#else
                        c->apicid = c->initial_apicid;
#endif
                        if (test_cpu_cap(c, X86_FEATURE_CLFLSH))
                                c->x86_clflush_size = ((ebx >> 8) & 0xff) * 8;
                } else {
                        /* Have CPUID level 0 only - unheard of */
                        c->x86 = 4;
                }

                /* AMD-defined flags: level 0x80000001 */
                xlvl = cpuid_eax(0x80000000);
                if ((xlvl & 0xffff0000) == 0x80000000) {
                        if (xlvl >= 0x80000001) {
                                c->x86_capability[1] = cpuid_edx(0x80000001);
                                c->x86_capability[6] = cpuid_ecx(0x80000001);
                        }
                        if (xlvl >= 0x80000004)
                                get_model_name(c); /* Default name */
                }

                init_scattered_cpuid_features(c);
                detect_nopl(c);
        }
}

static void __cpuinit squash_the_stupid_serial_number(struct cpuinfo_x86 *c)
{
        if (cpu_has(c, X86_FEATURE_PN) && disable_x86_serial_nr) {
                /* Disable processor serial number */
                unsigned long lo, hi;
                rdmsr(MSR_IA32_BBL_CR_CTL, lo, hi);
                lo |= 0x200000;
                wrmsr(MSR_IA32_BBL_CR_CTL, lo, hi);
                printk(KERN_NOTICE "CPU serial number disabled.\n");
                clear_cpu_cap(c, X86_FEATURE_PN);

                /* Disabling the serial number may affect the cpuid level */
                c->cpuid_level = cpuid_eax(0);
        }
}

static int __init x86_serial_nr_setup(char *s)
{
        disable_x86_serial_nr = 0;
        return 1;
}
__setup("serialnumber", x86_serial_nr_setup);



/*
 * This does the hard work of actually picking apart the CPU stuff...
 */
static void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
{
        int i;

        c->loops_per_jiffy = loops_per_jiffy;
        c->x86_cache_size = -1;
        c->x86_vendor = X86_VENDOR_UNKNOWN;
        c->cpuid_level = -1;    /* CPUID not detected */
        c->x86_model = c->x86_mask = 0; /* So far unknown... */
        c->x86_vendor_id[0] = '\0'; /* Unset */
        c->x86_model_id[0] = '\0';  /* Unset */
        c->x86_max_cores = 1;
        c->x86_clflush_size = 32;
        memset(&c->x86_capability, 0, sizeof c->x86_capability);

        if (!have_cpuid_p()) {
                /*
                 * First of all, decide if this is a 486 or higher
                 * It's a 486 if we can modify the AC flag
                 */
                if (flag_is_changeable_p(X86_EFLAGS_AC))
                        c->x86 = 4;
                else
                        c->x86 = 3;
        }

        generic_identify(c);

        if (this_cpu->c_identify)
                this_cpu->c_identify(c);

        /*
         * Vendor-specific initialization.  In this section we
         * canonicalize the feature flags, meaning if there are
         * features a certain CPU supports which CPUID doesn't
         * tell us, CPUID claiming incorrect flags, or other bugs,
         * we handle them here.
         *
         * At the end of this section, c->x86_capability better
         * indicate the features this CPU genuinely supports!
         */
        if (this_cpu->c_init)
                this_cpu->c_init(c);

        /* Disable the PN if appropriate */
        squash_the_stupid_serial_number(c);

        /*
         * The vendor-specific functions might have changed features.  Now
         * we do "generic changes."
         */

        /* If the model name is still unset, do table lookup. */
        if (!c->x86_model_id[0]) {
                char *p;
                p = table_lookup_model(c);
                if (p)
                        strcpy(c->x86_model_id, p);
                else
                        /* Last resort... */
                        sprintf(c->x86_model_id, "%02x/%02x",
                                c->x86, c->x86_model);
        }

        /*
         * On SMP, boot_cpu_data holds the common feature set between
         * all CPUs; so make sure that we indicate which features are
         * common between the CPUs.  The first time this routine gets
         * executed, c == &boot_cpu_data.
         */
        if (c != &boot_cpu_data) {
                /* AND the already accumulated flags with these */
                for (i = 0 ; i < NCAPINTS ; i++)
                        boot_cpu_data.x86_capability[i] &= c->x86_capability[i];
        }

        /* Clear all flags overriden by options */
        for (i = 0; i < NCAPINTS; i++)
                c->x86_capability[i] &= ~cleared_cpu_caps[i];

        /* Init Machine Check Exception if available. */
        mcheck_init(c);

        select_idle_routine(c);
}

void __init identify_boot_cpu(void)
{
        identify_cpu(&boot_cpu_data);
        sysenter_setup();
        enable_sep_cpu();
}

void __cpuinit identify_secondary_cpu(struct cpuinfo_x86 *c)
{
        BUG_ON(c == &boot_cpu_data);
        identify_cpu(c);
        enable_sep_cpu();
        mtrr_ap_init();
}

#ifdef CONFIG_X86_HT
void __cpuinit detect_ht(struct cpuinfo_x86 *c)
{
        u32     eax, ebx, ecx, edx;
        int     index_msb, core_bits;

        cpuid(1, &eax, &ebx, &ecx, &edx);

        if (!cpu_has(c, X86_FEATURE_HT) || cpu_has(c, X86_FEATURE_CMP_LEGACY))
                return;

        smp_num_siblings = (ebx & 0xff0000) >> 16;

        if (smp_num_siblings == 1) {
                printk(KERN_INFO  "CPU: Hyper-Threading is disabled\n");
        } else if (smp_num_siblings > 1) {

                if (smp_num_siblings > NR_CPUS) {
                        printk(KERN_WARNING "CPU: Unsupported number of the "
                                        "siblings %d", smp_num_siblings);
                        smp_num_siblings = 1;
                        return;
                }

                index_msb = get_count_order(smp_num_siblings);
                c->phys_proc_id = phys_pkg_id(c->initial_apicid, index_msb);

                printk(KERN_INFO  "CPU: Physical Processor ID: %d\n",
                       c->phys_proc_id);

                smp_num_siblings = smp_num_siblings / c->x86_max_cores;

                index_msb = get_count_order(smp_num_siblings) ;

                core_bits = get_count_order(c->x86_max_cores);

                c->cpu_core_id = phys_pkg_id(c->initial_apicid, index_msb) &
                                               ((1 << core_bits) - 1);

                if (c->x86_max_cores > 1)
                        printk(KERN_INFO  "CPU: Processor Core ID: %d\n",
                               c->cpu_core_id);
        }
}
#endif

static __init int setup_noclflush(char *arg)
{
        setup_clear_cpu_cap(X86_FEATURE_CLFLSH);
        return 1;
}
__setup("noclflush", setup_noclflush);

void __cpuinit print_cpu_info(struct cpuinfo_x86 *c)
{
        char *vendor = NULL;

        if (c->x86_vendor < X86_VENDOR_NUM)
                vendor = this_cpu->c_vendor;
        else if (c->cpuid_level >= 0)
                vendor = c->x86_vendor_id;

        if (vendor && strncmp(c->x86_model_id, vendor, strlen(vendor)))
                printk("%s ", vendor);

        if (!c->x86_model_id[0])
                printk("%d86", c->x86);
        else
                printk("%s", c->x86_model_id);

        if (c->x86_mask || c->cpuid_level >= 0)
                printk(" stepping %02x\n", c->x86_mask);
        else
                printk("\n");
}

static __init int setup_disablecpuid(char *arg)
{
        int bit;
        if (get_option(&arg, &bit) && bit < NCAPINTS*32)
                setup_clear_cpu_cap(bit);
        else
                return 0;
        return 1;
}
__setup("clearcpuid=", setup_disablecpuid);

cpumask_t cpu_initialized __cpuinitdata = CPU_MASK_NONE;

void __init early_cpu_init(void)
{
        struct cpu_vendor_dev *cvdev;

        for (cvdev = __x86cpuvendor_start ;
             cvdev < __x86cpuvendor_end   ;
             cvdev++)
                cpu_devs[cvdev->vendor] = cvdev->cpu_dev;

        early_cpu_detect();
        validate_pat_support(&boot_cpu_data);
}

/* Make sure %fs is initialized properly in idle threads */
struct pt_regs * __cpuinit idle_regs(struct pt_regs *regs)
{
        memset(regs, 0, sizeof(struct pt_regs));
        regs->fs = __KERNEL_PERCPU;
        return regs;
}

/* Current gdt points %fs at the "master" per-cpu area: after this,
 * it's on the real one. */
void switch_to_new_gdt(void)
{
        struct desc_ptr gdt_descr;

        gdt_descr.address = (long)get_cpu_gdt_table(smp_processor_id());
        gdt_descr.size = GDT_SIZE - 1;
        load_gdt(&gdt_descr);
        asm("mov %0, %%fs" : : "r" (__KERNEL_PERCPU) : "memory");
}

/*
 * cpu_init() initializes state that is per-CPU. Some data is already
 * initialized (naturally) in the bootstrap process, such as the GDT
 * and IDT. We reload them nevertheless, this function acts as a
 * 'CPU state barrier', nothing should get across.
 */
void __cpuinit cpu_init(void)
{
        int cpu = smp_processor_id();
        struct task_struct *curr = current;
        struct tss_struct *t = &per_cpu(init_tss, cpu);
        struct thread_struct *thread = &curr->thread;

        if (cpu_test_and_set(cpu, cpu_initialized)) {
                printk(KERN_WARNING "CPU#%d already initialized!\n", cpu);
                for (;;) local_irq_enable();
        }

        printk(KERN_INFO "Initializing CPU#%d\n", cpu);

        if (cpu_has_vme || cpu_has_tsc || cpu_has_de)
                clear_in_cr4(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);

        load_idt(&idt_descr);
        switch_to_new_gdt();

        /*
         * Set up and load the per-CPU TSS and LDT
         */
        atomic_inc(&init_mm.mm_count);
        curr->active_mm = &init_mm;
        if (curr->mm)
                BUG();
        enter_lazy_tlb(&init_mm, curr);

        load_sp0(t, thread);
        set_tss_desc(cpu, t);
        load_TR_desc();
        load_LDT(&init_mm.context);

#ifdef CONFIG_DOUBLEFAULT
        /* Set up doublefault TSS pointer in the GDT */
        __set_tss_desc(cpu, GDT_ENTRY_DOUBLEFAULT_TSS, &doublefault_tss);
#endif

        /* Clear %gs. */
        asm volatile ("mov %0, %%gs" : : "r" (0));

        /* Clear all 6 debug registers: */
        set_debugreg(0, 0);
        set_debugreg(0, 1);
        set_debugreg(0, 2);
        set_debugreg(0, 3);
        set_debugreg(0, 6);
        set_debugreg(0, 7);

        /*
         * Force FPU initialization:
         */
        current_thread_info()->status = 0;
        clear_used_math();
        mxcsr_feature_mask_init();
}

#ifdef CONFIG_HOTPLUG_CPU
void __cpuinit cpu_uninit(void)
{
        int cpu = raw_smp_processor_id();
        cpu_clear(cpu, cpu_initialized);

        /* lazy TLB state */
        per_cpu(cpu_tlbstate, cpu).state = 0;
        per_cpu(cpu_tlbstate, cpu).active_mm = &init_mm;
}
#endif