Merge branch 'x86/debug' into x86/cpu

[linux-2.6/verdex.git] / arch / x86 / kernel / cpu / common_64.c

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/bootmem.h>
#include <linux/bitops.h>
#include <linux/module.h>
#include <linux/kgdb.h>
#include <linux/topology.h>
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/percpu.h>
#include <asm/i387.h>
#include <asm/msr.h>
#include <asm/io.h>
#include <asm/linkage.h>
#include <asm/mmu_context.h>
#include <asm/mtrr.h>
#include <asm/mce.h>
#include <asm/pat.h>
#include <asm/asm.h>
#include <asm/numa.h>
#ifdef CONFIG_X86_LOCAL_APIC
#include <asm/mpspec.h>
#include <asm/apic.h>
#include <mach_apic.h>
#endif
#include <asm/pda.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/desc.h>
#include <asm/atomic.h>
#include <asm/proto.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/genapic.h>

#include "cpu.h"

/* We need valid kernel segments for data and code in long mode too
 * IRET will check the segment types  kkeil 2000/10/28
 * Also sysret mandates a special GDT layout
 */
/* The TLS descriptors are currently at a different place compared to i386.
   Hopefully nobody expects them at a fixed place (Wine?) */
DEFINE_PER_CPU(struct gdt_page, gdt_page) = { .gdt = {
        [GDT_ENTRY_KERNEL32_CS] = { { { 0x0000ffff, 0x00cf9b00 } } },
        [GDT_ENTRY_KERNEL_CS] = { { { 0x0000ffff, 0x00af9b00 } } },
        [GDT_ENTRY_KERNEL_DS] = { { { 0x0000ffff, 0x00cf9300 } } },
        [GDT_ENTRY_DEFAULT_USER32_CS] = { { { 0x0000ffff, 0x00cffb00 } } },
        [GDT_ENTRY_DEFAULT_USER_DS] = { { { 0x0000ffff, 0x00cff300 } } },
        [GDT_ENTRY_DEFAULT_USER_CS] = { { { 0x0000ffff, 0x00affb00 } } },
} };
EXPORT_PER_CPU_SYMBOL_GPL(gdt_page);

__u32 cleared_cpu_caps[NCAPINTS] __cpuinitdata;

/* 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);
}

struct cpu_dev *cpu_devs[X86_VENDOR_NUM] = {};

static void __cpuinit default_init(struct cpuinfo_x86 *c)
{
        display_cacheinfo(c);
}

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

int __cpuinit get_model_name(struct cpuinfo_x86 *c)
{
        unsigned int *v;

        if (c->extended_cpuid_level < 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;
        return 1;
}


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

        n = c->extended_cpuid_level;

        if (n >= 0x80000005) {
                cpuid(0x80000005, &dummy, &ebx, &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);
                /* On K8 L1 TLB is inclusive, so don't count it */
                c->x86_tlbsize = 0;
        }

        if (n >= 0x80000006) {
                cpuid(0x80000006, &dummy, &ebx, &ecx, &edx);
                ecx = cpuid_ecx(0x80000006);
                c->x86_cache_size = ecx >> 16;
                c->x86_tlbsize += ((ebx >> 16) & 0xfff) + (ebx & 0xfff);

                printk(KERN_INFO "CPU: L2 Cache: %dK (%d bytes/line)\n",
                c->x86_cache_size, ecx & 0xFF);
        }
}

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

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


        if (!cpu_has(c, X86_FEATURE_HT))
                return;
        if (cpu_has(c, X86_FEATURE_CMP_LEGACY))
                goto out;

        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 "
                               "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(index_msb);

                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(index_msb) &
                                               ((1 << core_bits) - 1);
        }
out:
        if ((c->x86_max_cores * smp_num_siblings) > 1) {
                printk(KERN_INFO  "CPU: Physical Processor ID: %d\n",
                       c->phys_proc_id);
                printk(KERN_INFO  "CPU: Processor Core ID: %d\n",
                       c->cpu_core_id);
        }

#endif
}

static void __cpuinit get_cpu_vendor(struct cpuinfo_x86 *c)
{
        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;
                                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;
}

static void __init early_cpu_support_print(void)
{
        int i,j;
        struct cpu_dev *cpu_devx;

        printk("KERNEL supported cpus:\n");
        for (i = 0; i < X86_VENDOR_NUM; i++) {
                cpu_devx = cpu_devs[i];
                if (!cpu_devx)
                        continue;
                for (j = 0; j < 2; j++) {
                        if (!cpu_devx->c_ident[j])
                                continue;
                        printk("  %s %s\n", cpu_devx->c_vendor,
                                cpu_devx->c_ident[j]);
                }
        }
}

/*
 * 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.
 *
 * Note: no 64-bit chip is known to lack these, but put the code here
 * for consistency with 32 bits, and to make it utterly trivial to
 * diagnose the problem should it ever surface.
 */
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 early_identify_cpu(struct cpuinfo_x86 *c);

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_support_print();
        early_identify_cpu(&boot_cpu_data);
}

/* Do some early cpuid on the boot CPU to get some parameter that are
   needed before check_bugs. Everything advanced is in identify_cpu
   below. */
static void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c)
{
        u32 tfms, xlvl;

        c->loops_per_jiffy = loops_per_jiffy;
        c->x86_cache_size = -1;
        c->x86_vendor = X86_VENDOR_UNKNOWN;
        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_clflush_size = 64;
        c->x86_cache_alignment = c->x86_clflush_size;
        c->x86_max_cores = 1;
        c->x86_coreid_bits = 0;
        c->extended_cpuid_level = 0;
        memset(&c->x86_capability, 0, sizeof c->x86_capability);

        /* 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);

        /* 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 misc;
                cpuid(0x00000001, &tfms, &misc, &c->x86_capability[4],
                      &c->x86_capability[0]);
                c->x86 = (tfms >> 8) & 0xf;
                c->x86_model = (tfms >> 4) & 0xf;
                c->x86_mask = tfms & 0xf;
                if (c->x86 == 0xf)
                        c->x86 += (tfms >> 20) & 0xff;
                if (c->x86 >= 0x6)
                        c->x86_model += ((tfms >> 16) & 0xF) << 4;
                if (test_cpu_cap(c, X86_FEATURE_CLFLSH))
                        c->x86_clflush_size = ((misc >> 8) & 0xff) * 8;
        } else {
                /* Have CPUID level 0 only - unheard of */
                c->x86 = 4;
        }

        c->initial_apicid = (cpuid_ebx(1) >> 24) & 0xff;
#ifdef CONFIG_SMP
        c->phys_proc_id = c->initial_apicid;
#endif
        /* AMD-defined flags: level 0x80000001 */
        xlvl = cpuid_eax(0x80000000);
        c->extended_cpuid_level = xlvl;
        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 */
        }

        /* Transmeta-defined flags: level 0x80860001 */
        xlvl = cpuid_eax(0x80860000);
        if ((xlvl & 0xffff0000) == 0x80860000) {
                /* Don't set x86_cpuid_level here for now to not confuse. */
                if (xlvl >= 0x80860001)
                        c->x86_capability[2] = cpuid_edx(0x80860001);
        }

        if (c->extended_cpuid_level >= 0x80000007)
                c->x86_power = cpuid_edx(0x80000007);

        if (c->extended_cpuid_level >= 0x80000008) {
                u32 eax = cpuid_eax(0x80000008);

                c->x86_virt_bits = (eax >> 8) & 0xff;
                c->x86_phys_bits = eax & 0xff;
        }

        detect_nopl(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);

        validate_pat_support(c);
}

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

        early_identify_cpu(c);

        init_scattered_cpuid_features(c);

        c->apicid = phys_pkg_id(0);

        /*
         * 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);

        detect_ht(c);

        /*
         * 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];

#ifdef CONFIG_X86_MCE
        mcheck_init(c);
#endif
        select_idle_routine(c);

#ifdef CONFIG_NUMA
        numa_add_cpu(smp_processor_id());
#endif

}

void __cpuinit identify_boot_cpu(void)
{
        identify_cpu(&boot_cpu_data);
}

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

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

struct msr_range {
        unsigned min;
        unsigned max;
};

static struct msr_range msr_range_array[] __cpuinitdata = {
        { 0x00000000, 0x00000418},
        { 0xc0000000, 0xc000040b},
        { 0xc0010000, 0xc0010142},
        { 0xc0011000, 0xc001103b},
};

static void __cpuinit print_cpu_msr(void)
{
        unsigned index;
        u64 val;
        int i;
        unsigned index_min, index_max;

        for (i = 0; i < ARRAY_SIZE(msr_range_array); i++) {
                index_min = msr_range_array[i].min;
                index_max = msr_range_array[i].max;
                for (index = index_min; index < index_max; index++) {
                        if (rdmsrl_amd_safe(index, &val))
                                continue;
                        printk(KERN_INFO " MSR%08x: %016llx\n", index, val);
                }
        }
}

static int show_msr __cpuinitdata;
static __init int setup_show_msr(char *arg)
{
        int num;

        get_option(&arg, &num);

        if (num > 0)
                show_msr = num;
        return 1;
}
__setup("show_msr=", setup_show_msr);

void __cpuinit print_cpu_info(struct cpuinfo_x86 *c)
{
        if (c->x86_model_id[0])
                printk(KERN_CONT "%s", c->x86_model_id);

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

#ifdef CONFIG_SMP
        if (c->cpu_index < show_msr)
                print_cpu_msr();
#else
        if (show_msr)
                print_cpu_msr();
#endif
}

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;

struct x8664_pda **_cpu_pda __read_mostly;
EXPORT_SYMBOL(_cpu_pda);

struct desc_ptr idt_descr = { 256 * 16 - 1, (unsigned long) idt_table };

char boot_cpu_stack[IRQSTACKSIZE] __page_aligned_bss;

unsigned long __supported_pte_mask __read_mostly = ~0UL;
EXPORT_SYMBOL_GPL(__supported_pte_mask);

static int do_not_nx __cpuinitdata;

/* noexec=on|off
Control non executable mappings for 64bit processes.

on      Enable(default)
off     Disable
*/
static int __init nonx_setup(char *str)
{
        if (!str)
                return -EINVAL;
        if (!strncmp(str, "on", 2)) {
                __supported_pte_mask |= _PAGE_NX;
                do_not_nx = 0;
        } else if (!strncmp(str, "off", 3)) {
                do_not_nx = 1;
                __supported_pte_mask &= ~_PAGE_NX;
        }
        return 0;
}
early_param("noexec", nonx_setup);

int force_personality32;

/* noexec32=on|off
Control non executable heap for 32bit processes.
To control the stack too use noexec=off

on      PROT_READ does not imply PROT_EXEC for 32bit processes (default)
off     PROT_READ implies PROT_EXEC
*/
static int __init nonx32_setup(char *str)
{
        if (!strcmp(str, "on"))
                force_personality32 &= ~READ_IMPLIES_EXEC;
        else if (!strcmp(str, "off"))
                force_personality32 |= READ_IMPLIES_EXEC;
        return 1;
}
__setup("noexec32=", nonx32_setup);

void pda_init(int cpu)
{
        struct x8664_pda *pda = cpu_pda(cpu);

        /* Setup up data that may be needed in __get_free_pages early */
        loadsegment(fs, 0);
        loadsegment(gs, 0);
        /* Memory clobbers used to order PDA accessed */
        mb();
        wrmsrl(MSR_GS_BASE, pda);
        mb();

        pda->cpunumber = cpu;
        pda->irqcount = -1;
        pda->kernelstack = (unsigned long)stack_thread_info() -
                                 PDA_STACKOFFSET + THREAD_SIZE;
        pda->active_mm = &init_mm;
        pda->mmu_state = 0;

        if (cpu == 0) {
                /* others are initialized in smpboot.c */
                pda->pcurrent = &init_task;
                pda->irqstackptr = boot_cpu_stack;
        } else {
                pda->irqstackptr = (char *)
                        __get_free_pages(GFP_ATOMIC, IRQSTACK_ORDER);
                if (!pda->irqstackptr)
                        panic("cannot allocate irqstack for cpu %d", cpu);

                if (pda->nodenumber == 0 && cpu_to_node(cpu) != NUMA_NO_NODE)
                        pda->nodenumber = cpu_to_node(cpu);
        }

        pda->irqstackptr += IRQSTACKSIZE-64;
}

char boot_exception_stacks[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ +
                           DEBUG_STKSZ] __page_aligned_bss;

extern asmlinkage void ignore_sysret(void);

/* May not be marked __init: used by software suspend */
void syscall_init(void)
{
        /*
         * LSTAR and STAR live in a bit strange symbiosis.
         * They both write to the same internal register. STAR allows to
         * set CS/DS but only a 32bit target. LSTAR sets the 64bit rip.
         */
        wrmsrl(MSR_STAR,  ((u64)__USER32_CS)<<48  | ((u64)__KERNEL_CS)<<32);
        wrmsrl(MSR_LSTAR, system_call);
        wrmsrl(MSR_CSTAR, ignore_sysret);

#ifdef CONFIG_IA32_EMULATION
        syscall32_cpu_init();
#endif

        /* Flags to clear on syscall */
        wrmsrl(MSR_SYSCALL_MASK,
               X86_EFLAGS_TF|X86_EFLAGS_DF|X86_EFLAGS_IF|X86_EFLAGS_IOPL);
}

void __cpuinit check_efer(void)
{
        unsigned long efer;

        rdmsrl(MSR_EFER, efer);
        if (!(efer & EFER_NX) || do_not_nx)
                __supported_pte_mask &= ~_PAGE_NX;
}

unsigned long kernel_eflags;

/*
 * Copies of the original ist values from the tss are only accessed during
 * debugging, no special alignment required.
 */
DEFINE_PER_CPU(struct orig_ist, orig_ist);

/*
 * 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.
 * A lot of state is already set up in PDA init.
 */
void __cpuinit cpu_init(void)
{
        int cpu = stack_smp_processor_id();
        struct tss_struct *t = &per_cpu(init_tss, cpu);
        struct orig_ist *orig_ist = &per_cpu(orig_ist, cpu);
        unsigned long v;
        char *estacks = NULL;
        struct task_struct *me;
        int i;

        /* CPU 0 is initialised in head64.c */
        if (cpu != 0)
                pda_init(cpu);
        else
                estacks = boot_exception_stacks;

        me = current;

        if (cpu_test_and_set(cpu, cpu_initialized))
                panic("CPU#%d already initialized!\n", cpu);

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

        clear_in_cr4(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);

        /*
         * Initialize the per-CPU GDT with the boot GDT,
         * and set up the GDT descriptor:
         */

        switch_to_new_gdt();
        load_idt((const struct desc_ptr *)&idt_descr);

        memset(me->thread.tls_array, 0, GDT_ENTRY_TLS_ENTRIES * 8);
        syscall_init();

        wrmsrl(MSR_FS_BASE, 0);
        wrmsrl(MSR_KERNEL_GS_BASE, 0);
        barrier();

        check_efer();

        /*
         * set up and load the per-CPU TSS
         */
        for (v = 0; v < N_EXCEPTION_STACKS; v++) {
                static const unsigned int order[N_EXCEPTION_STACKS] = {
                        [0 ... N_EXCEPTION_STACKS - 1] = EXCEPTION_STACK_ORDER,
                        [DEBUG_STACK - 1] = DEBUG_STACK_ORDER
                };
                if (cpu) {
                        estacks = (char *)__get_free_pages(GFP_ATOMIC, order[v]);
                        if (!estacks)
                                panic("Cannot allocate exception stack %ld %d\n",
                                      v, cpu);
                }
                estacks += PAGE_SIZE << order[v];
                orig_ist->ist[v] = t->x86_tss.ist[v] = (unsigned long)estacks;
        }

        t->x86_tss.io_bitmap_base = offsetof(struct tss_struct, io_bitmap);
        /*
         * <= is required because the CPU will access up to
         * 8 bits beyond the end of the IO permission bitmap.
         */
        for (i = 0; i <= IO_BITMAP_LONGS; i++)
                t->io_bitmap[i] = ~0UL;

        atomic_inc(&init_mm.mm_count);
        me->active_mm = &init_mm;
        if (me->mm)
                BUG();
        enter_lazy_tlb(&init_mm, me);

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

#ifdef CONFIG_KGDB
        /*
         * If the kgdb is connected no debug regs should be altered.  This
         * is only applicable when KGDB and a KGDB I/O module are built
         * into the kernel and you are using early debugging with
         * kgdbwait. KGDB will control the kernel HW breakpoint registers.
         */
        if (kgdb_connected && arch_kgdb_ops.correct_hw_break)
                arch_kgdb_ops.correct_hw_break();
        else {
#endif
        /*
         * Clear all 6 debug registers:
         */

        set_debugreg(0UL, 0);
        set_debugreg(0UL, 1);
        set_debugreg(0UL, 2);
        set_debugreg(0UL, 3);
        set_debugreg(0UL, 6);
        set_debugreg(0UL, 7);
#ifdef CONFIG_KGDB
        /* If the kgdb is connected no debug regs should be altered. */
        }
#endif

        fpu_init();

        raw_local_save_flags(kernel_eflags);

        if (is_uv_system())
                uv_cpu_init();
}