x86/entry/64: Stop initializing TSS.sp0 at boot

[linux.git] / arch / x86 / kernel / cpu / common.c

#include <linux/bootmem.h>
#include <linux/linkage.h>
#include <linux/bitops.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/percpu.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/sched/mm.h>
#include <linux/sched/clock.h>
#include <linux/sched/task.h>
#include <linux/init.h>
#include <linux/kprobes.h>
#include <linux/kgdb.h>
#include <linux/smp.h>
#include <linux/io.h>
#include <linux/syscore_ops.h>

#include <asm/stackprotector.h>
#include <asm/perf_event.h>
#include <asm/mmu_context.h>
#include <asm/archrandom.h>
#include <asm/hypervisor.h>
#include <asm/processor.h>
#include <asm/tlbflush.h>
#include <asm/debugreg.h>
#include <asm/sections.h>
#include <asm/vsyscall.h>
#include <linux/topology.h>
#include <linux/cpumask.h>
#include <asm/pgtable.h>
#include <linux/atomic.h>
#include <asm/proto.h>
#include <asm/setup.h>
#include <asm/apic.h>
#include <asm/desc.h>
#include <asm/fpu/internal.h>
#include <asm/mtrr.h>
#include <asm/hwcap2.h>
#include <linux/numa.h>
#include <asm/asm.h>
#include <asm/bugs.h>
#include <asm/cpu.h>
#include <asm/mce.h>
#include <asm/msr.h>
#include <asm/pat.h>
#include <asm/microcode.h>
#include <asm/microcode_intel.h>

#ifdef CONFIG_X86_LOCAL_APIC
#include <asm/uv/uv.h>
#endif

#include "cpu.h"

u32 elf_hwcap2 __read_mostly;

/* all of these masks are initialized in setup_cpu_local_masks() */
cpumask_var_t cpu_initialized_mask;
cpumask_var_t cpu_callout_mask;
cpumask_var_t cpu_callin_mask;

/* representing cpus for which sibling maps can be computed */
cpumask_var_t cpu_sibling_setup_mask;

/* correctly size the local cpu masks */
void __init setup_cpu_local_masks(void)
{
        alloc_bootmem_cpumask_var(&cpu_initialized_mask);
        alloc_bootmem_cpumask_var(&cpu_callin_mask);
        alloc_bootmem_cpumask_var(&cpu_callout_mask);
        alloc_bootmem_cpumask_var(&cpu_sibling_setup_mask);
}

static void default_init(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_X86_64
        cpu_detect_cache_sizes(c);
#else
        /* 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");
        }
#endif
}

static const struct cpu_dev default_cpu = {
        .c_init         = default_init,
        .c_vendor       = "Unknown",
        .c_x86_vendor   = X86_VENDOR_UNKNOWN,
};

static const struct cpu_dev *this_cpu = &default_cpu;

DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = {
#ifdef CONFIG_X86_64
        /*
         * 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
         *
         * TLS descriptors are currently at a different place compared to i386.
         * Hopefully nobody expects them at a fixed place (Wine?)
         */
        [GDT_ENTRY_KERNEL32_CS]         = GDT_ENTRY_INIT(0xc09b, 0, 0xfffff),
        [GDT_ENTRY_KERNEL_CS]           = GDT_ENTRY_INIT(0xa09b, 0, 0xfffff),
        [GDT_ENTRY_KERNEL_DS]           = GDT_ENTRY_INIT(0xc093, 0, 0xfffff),
        [GDT_ENTRY_DEFAULT_USER32_CS]   = GDT_ENTRY_INIT(0xc0fb, 0, 0xfffff),
        [GDT_ENTRY_DEFAULT_USER_DS]     = GDT_ENTRY_INIT(0xc0f3, 0, 0xfffff),
        [GDT_ENTRY_DEFAULT_USER_CS]     = GDT_ENTRY_INIT(0xa0fb, 0, 0xfffff),
#else
        [GDT_ENTRY_KERNEL_CS]           = GDT_ENTRY_INIT(0xc09a, 0, 0xfffff),
        [GDT_ENTRY_KERNEL_DS]           = GDT_ENTRY_INIT(0xc092, 0, 0xfffff),
        [GDT_ENTRY_DEFAULT_USER_CS]     = GDT_ENTRY_INIT(0xc0fa, 0, 0xfffff),
        [GDT_ENTRY_DEFAULT_USER_DS]     = GDT_ENTRY_INIT(0xc0f2, 0, 0xfffff),
        /*
         * 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]        = GDT_ENTRY_INIT(0x409a, 0, 0xffff),
        /* 16-bit code */
        [GDT_ENTRY_PNPBIOS_CS16]        = GDT_ENTRY_INIT(0x009a, 0, 0xffff),
        /* 16-bit data */
        [GDT_ENTRY_PNPBIOS_DS]          = GDT_ENTRY_INIT(0x0092, 0, 0xffff),
        /* 16-bit data */
        [GDT_ENTRY_PNPBIOS_TS1]         = GDT_ENTRY_INIT(0x0092, 0, 0),
        /* 16-bit data */
        [GDT_ENTRY_PNPBIOS_TS2]         = GDT_ENTRY_INIT(0x0092, 0, 0),
        /*
         * 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]        = GDT_ENTRY_INIT(0x409a, 0, 0xffff),
        /* 16-bit code */
        [GDT_ENTRY_APMBIOS_BASE+1]      = GDT_ENTRY_INIT(0x009a, 0, 0xffff),
        /* data */
        [GDT_ENTRY_APMBIOS_BASE+2]      = GDT_ENTRY_INIT(0x4092, 0, 0xffff),

        [GDT_ENTRY_ESPFIX_SS]           = GDT_ENTRY_INIT(0xc092, 0, 0xfffff),
        [GDT_ENTRY_PERCPU]              = GDT_ENTRY_INIT(0xc092, 0, 0xfffff),
        GDT_STACK_CANARY_INIT
#endif
} };
EXPORT_PER_CPU_SYMBOL_GPL(gdt_page);

static int __init x86_mpx_setup(char *s)
{
        /* require an exact match without trailing characters */
        if (strlen(s))
                return 0;

        /* do not emit a message if the feature is not present */
        if (!boot_cpu_has(X86_FEATURE_MPX))
                return 1;

        setup_clear_cpu_cap(X86_FEATURE_MPX);
        pr_info("nompx: Intel Memory Protection Extensions (MPX) disabled\n");
        return 1;
}
__setup("nompx", x86_mpx_setup);

#ifdef CONFIG_X86_64
static int __init x86_nopcid_setup(char *s)
{
        /* nopcid doesn't accept parameters */
        if (s)
                return -EINVAL;

        /* do not emit a message if the feature is not present */
        if (!boot_cpu_has(X86_FEATURE_PCID))
                return 0;

        setup_clear_cpu_cap(X86_FEATURE_PCID);
        pr_info("nopcid: PCID feature disabled\n");
        return 0;
}
early_param("nopcid", x86_nopcid_setup);
#endif

static int __init x86_noinvpcid_setup(char *s)
{
        /* noinvpcid doesn't accept parameters */
        if (s)
                return -EINVAL;

        /* do not emit a message if the feature is not present */
        if (!boot_cpu_has(X86_FEATURE_INVPCID))
                return 0;

        setup_clear_cpu_cap(X86_FEATURE_INVPCID);
        pr_info("noinvpcid: INVPCID feature disabled\n");
        return 0;
}
early_param("noinvpcid", x86_noinvpcid_setup);

#ifdef CONFIG_X86_32
static int cachesize_override = -1;
static int disable_x86_serial_nr = 1;

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

        /*
         * Cyrix and IDT cpus allow disabling of CPUID
         * so the code below may return different results
         * when it is executed before and after enabling
         * the CPUID. Add "volatile" to not allow gcc to
         * optimize the subsequent calls to this function.
         */
        asm volatile ("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 */
int have_cpuid_p(void)
{
        return flag_is_changeable_p(X86_EFLAGS_ID);
}

static void squash_the_stupid_serial_number(struct cpuinfo_x86 *c)
{
        unsigned long lo, hi;

        if (!cpu_has(c, X86_FEATURE_PN) || !disable_x86_serial_nr)
                return;

        /* Disable processor serial number: */

        rdmsr(MSR_IA32_BBL_CR_CTL, lo, hi);
        lo |= 0x200000;
        wrmsr(MSR_IA32_BBL_CR_CTL, lo, hi);

        pr_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);
#else
static inline int flag_is_changeable_p(u32 flag)
{
        return 1;
}
static inline void squash_the_stupid_serial_number(struct cpuinfo_x86 *c)
{
}
#endif

static __init int setup_disable_smep(char *arg)
{
        setup_clear_cpu_cap(X86_FEATURE_SMEP);
        /* Check for things that depend on SMEP being enabled: */
        check_mpx_erratum(&boot_cpu_data);
        return 1;
}
__setup("nosmep", setup_disable_smep);

static __always_inline void setup_smep(struct cpuinfo_x86 *c)
{
        if (cpu_has(c, X86_FEATURE_SMEP))
                cr4_set_bits(X86_CR4_SMEP);
}

static __init int setup_disable_smap(char *arg)
{
        setup_clear_cpu_cap(X86_FEATURE_SMAP);
        return 1;
}
__setup("nosmap", setup_disable_smap);

static __always_inline void setup_smap(struct cpuinfo_x86 *c)
{
        unsigned long eflags = native_save_fl();

        /* This should have been cleared long ago */
        BUG_ON(eflags & X86_EFLAGS_AC);

        if (cpu_has(c, X86_FEATURE_SMAP)) {
#ifdef CONFIG_X86_SMAP
                cr4_set_bits(X86_CR4_SMAP);
#else
                cr4_clear_bits(X86_CR4_SMAP);
#endif
        }
}

/*
 * Protection Keys are not available in 32-bit mode.
 */
static bool pku_disabled;

static __always_inline void setup_pku(struct cpuinfo_x86 *c)
{
        /* check the boot processor, plus compile options for PKU: */
        if (!cpu_feature_enabled(X86_FEATURE_PKU))
                return;
        /* checks the actual processor's cpuid bits: */
        if (!cpu_has(c, X86_FEATURE_PKU))
                return;
        if (pku_disabled)
                return;

        cr4_set_bits(X86_CR4_PKE);
        /*
         * Seting X86_CR4_PKE will cause the X86_FEATURE_OSPKE
         * cpuid bit to be set.  We need to ensure that we
         * update that bit in this CPU's "cpu_info".
         */
        get_cpu_cap(c);
}

#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
static __init int setup_disable_pku(char *arg)
{
        /*
         * Do not clear the X86_FEATURE_PKU bit.  All of the
         * runtime checks are against OSPKE so clearing the
         * bit does nothing.
         *
         * This way, we will see "pku" in cpuinfo, but not
         * "ospke", which is exactly what we want.  It shows
         * that the CPU has PKU, but the OS has not enabled it.
         * This happens to be exactly how a system would look
         * if we disabled the config option.
         */
        pr_info("x86: 'nopku' specified, disabling Memory Protection Keys\n");
        pku_disabled = true;
        return 1;
}
__setup("nopku", setup_disable_pku);
#endif /* CONFIG_X86_64 */

/*
 * Some CPU features depend on higher CPUID levels, which may not always
 * be available due to CPUID level capping or broken virtualization
 * software.  Add those features to this table to auto-disable them.
 */
struct cpuid_dependent_feature {
        u32 feature;
        u32 level;
};

static const struct cpuid_dependent_feature
cpuid_dependent_features[] = {
        { X86_FEATURE_MWAIT,            0x00000005 },
        { X86_FEATURE_DCA,              0x00000009 },
        { X86_FEATURE_XSAVE,            0x0000000d },
        { 0, 0 }
};

static void filter_cpuid_features(struct cpuinfo_x86 *c, bool warn)
{
        const struct cpuid_dependent_feature *df;

        for (df = cpuid_dependent_features; df->feature; df++) {

                if (!cpu_has(c, df->feature))
                        continue;
                /*
                 * Note: cpuid_level is set to -1 if unavailable, but
                 * extended_extended_level is set to 0 if unavailable
                 * and the legitimate extended levels are all negative
                 * when signed; hence the weird messing around with
                 * signs here...
                 */
                if (!((s32)df->level < 0 ?
                     (u32)df->level > (u32)c->extended_cpuid_level :
                     (s32)df->level > (s32)c->cpuid_level))
                        continue;

                clear_cpu_cap(c, df->feature);
                if (!warn)
                        continue;

                pr_warn("CPU: CPU feature " X86_CAP_FMT " disabled, no CPUID level 0x%x\n",
                        x86_cap_flag(df->feature), df->level);
        }
}

/*
 * 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 const char *table_lookup_model(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_X86_32
        const struct legacy_cpu_model_info *info;

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

        if (!this_cpu)
                return NULL;

        info = this_cpu->legacy_models;

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

__u32 cpu_caps_cleared[NCAPINTS];
__u32 cpu_caps_set[NCAPINTS];

void load_percpu_segment(int cpu)
{
#ifdef CONFIG_X86_32
        loadsegment(fs, __KERNEL_PERCPU);
#else
        __loadsegment_simple(gs, 0);
        wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu));
#endif
        load_stack_canary_segment();
}

/* Setup the fixmap mapping only once per-processor */
static inline void setup_fixmap_gdt(int cpu)
{
#ifdef CONFIG_X86_64
        /* On 64-bit systems, we use a read-only fixmap GDT. */
        pgprot_t prot = PAGE_KERNEL_RO;
#else
        /*
         * On native 32-bit systems, the GDT cannot be read-only because
         * our double fault handler uses a task gate, and entering through
         * a task gate needs to change an available TSS to busy.  If the GDT
         * is read-only, that will triple fault.
         *
         * On Xen PV, the GDT must be read-only because the hypervisor requires
         * it.
         */
        pgprot_t prot = boot_cpu_has(X86_FEATURE_XENPV) ?
                PAGE_KERNEL_RO : PAGE_KERNEL;
#endif

        __set_fixmap(get_cpu_gdt_ro_index(cpu), get_cpu_gdt_paddr(cpu), prot);
}

/* Load the original GDT from the per-cpu structure */
void load_direct_gdt(int cpu)
{
        struct desc_ptr gdt_descr;

        gdt_descr.address = (long)get_cpu_gdt_rw(cpu);
        gdt_descr.size = GDT_SIZE - 1;
        load_gdt(&gdt_descr);
}
EXPORT_SYMBOL_GPL(load_direct_gdt);

/* Load a fixmap remapping of the per-cpu GDT */
void load_fixmap_gdt(int cpu)
{
        struct desc_ptr gdt_descr;

        gdt_descr.address = (long)get_cpu_gdt_ro(cpu);
        gdt_descr.size = GDT_SIZE - 1;
        load_gdt(&gdt_descr);
}
EXPORT_SYMBOL_GPL(load_fixmap_gdt);

/*
 * Current gdt points %fs at the "master" per-cpu area: after this,
 * it's on the real one.
 */
void switch_to_new_gdt(int cpu)
{
        /* Load the original GDT */
        load_direct_gdt(cpu);
        /* Reload the per-cpu base */
        load_percpu_segment(cpu);
}

static const struct cpu_dev *cpu_devs[X86_VENDOR_NUM] = {};

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

        if (c->extended_cpuid_level < 0x80000004)
                return;

        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;

        /* Trim whitespace */
        p = q = s = &c->x86_model_id[0];

        while (*p == ' ')
                p++;

        while (*p) {
                /* Note the last non-whitespace index */
                if (!isspace(*p))
                        s = q;

                *q++ = *p++;
        }

        *(s + 1) = '\0';
}

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

        n = c->extended_cpuid_level;

        if (n >= 0x80000005) {
                cpuid(0x80000005, &dummy, &ebx, &ecx, &edx);
                c->x86_cache_size = (ecx>>24) + (edx>>24);
#ifdef CONFIG_X86_64
                /* On K8 L1 TLB is inclusive, so don't count it */
                c->x86_tlbsize = 0;
#endif
        }

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

        cpuid(0x80000006, &dummy, &ebx, &ecx, &edx);
        l2size = ecx >> 16;

#ifdef CONFIG_X86_64
        c->x86_tlbsize += ((ebx >> 16) & 0xfff) + (ebx & 0xfff);
#else
        /* do processor-specific cache resizing */
        if (this_cpu->legacy_cache_size)
                l2size = this_cpu->legacy_cache_size(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 */
#endif

        c->x86_cache_size = l2size;
}

u16 __read_mostly tlb_lli_4k[NR_INFO];
u16 __read_mostly tlb_lli_2m[NR_INFO];
u16 __read_mostly tlb_lli_4m[NR_INFO];
u16 __read_mostly tlb_lld_4k[NR_INFO];
u16 __read_mostly tlb_lld_2m[NR_INFO];
u16 __read_mostly tlb_lld_4m[NR_INFO];
u16 __read_mostly tlb_lld_1g[NR_INFO];

static void cpu_detect_tlb(struct cpuinfo_x86 *c)
{
        if (this_cpu->c_detect_tlb)
                this_cpu->c_detect_tlb(c);

        pr_info("Last level iTLB entries: 4KB %d, 2MB %d, 4MB %d\n",
                tlb_lli_4k[ENTRIES], tlb_lli_2m[ENTRIES],
                tlb_lli_4m[ENTRIES]);

        pr_info("Last level dTLB entries: 4KB %d, 2MB %d, 4MB %d, 1GB %d\n",
                tlb_lld_4k[ENTRIES], tlb_lld_2m[ENTRIES],
                tlb_lld_4m[ENTRIES], tlb_lld_1g[ENTRIES]);
}

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

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

        if (cpu_has(c, X86_FEATURE_CMP_LEGACY))
                goto out;

        if (cpu_has(c, X86_FEATURE_XTOPOLOGY))
                return;

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

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

        if (smp_num_siblings == 1) {
                pr_info_once("CPU0: Hyper-Threading is disabled\n");
                goto out;
        }

        if (smp_num_siblings <= 1)
                goto out;

        index_msb = get_count_order(smp_num_siblings);
        c->phys_proc_id = apic->phys_pkg_id(c->initial_apicid, 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 = apic->phys_pkg_id(c->initial_apicid, index_msb) &
                                       ((1 << core_bits) - 1);

out:
        if (!printed && (c->x86_max_cores * smp_num_siblings) > 1) {
                pr_info("CPU: Physical Processor ID: %d\n",
                        c->phys_proc_id);
                pr_info("CPU: Processor Core ID: %d\n",
                        c->cpu_core_id);
                printed = 1;
        }
#endif
}

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

        for (i = 0; i < X86_VENDOR_NUM; i++) {
                if (!cpu_devs[i])
                        break;

                if (!strcmp(v, cpu_devs[i]->c_ident[0]) ||
                    (cpu_devs[i]->c_ident[1] &&
                     !strcmp(v, cpu_devs[i]->c_ident[1]))) {

                        this_cpu = cpu_devs[i];
                        c->x86_vendor = this_cpu->c_x86_vendor;
                        return;
                }
        }

        pr_err_once("CPU: vendor_id '%s' unknown, using generic init.\n" \
                    "CPU: Your system may be unstable.\n", v);

        c->x86_vendor = X86_VENDOR_UNKNOWN;
        this_cpu = &default_cpu;
}

void 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;
        /* Intel-defined flags: level 0x00000001 */
        if (c->cpuid_level >= 0x00000001) {
                u32 junk, tfms, cap0, misc;

                cpuid(0x00000001, &tfms, &misc, &junk, &cap0);
                c->x86          = x86_family(tfms);
                c->x86_model    = x86_model(tfms);
                c->x86_mask     = x86_stepping(tfms);

                if (cap0 & (1<<19)) {
                        c->x86_clflush_size = ((misc >> 8) & 0xff) * 8;
                        c->x86_cache_alignment = c->x86_clflush_size;
                }
        }
}

static void apply_forced_caps(struct cpuinfo_x86 *c)
{
        int i;

        for (i = 0; i < NCAPINTS; i++) {
                c->x86_capability[i] &= ~cpu_caps_cleared[i];
                c->x86_capability[i] |= cpu_caps_set[i];
        }
}

void get_cpu_cap(struct cpuinfo_x86 *c)
{
        u32 eax, ebx, ecx, edx;

        /* Intel-defined flags: level 0x00000001 */
        if (c->cpuid_level >= 0x00000001) {
                cpuid(0x00000001, &eax, &ebx, &ecx, &edx);

                c->x86_capability[CPUID_1_ECX] = ecx;
                c->x86_capability[CPUID_1_EDX] = edx;
        }

        /* Thermal and Power Management Leaf: level 0x00000006 (eax) */
        if (c->cpuid_level >= 0x00000006)
                c->x86_capability[CPUID_6_EAX] = cpuid_eax(0x00000006);

        /* Additional Intel-defined flags: level 0x00000007 */
        if (c->cpuid_level >= 0x00000007) {
                cpuid_count(0x00000007, 0, &eax, &ebx, &ecx, &edx);
                c->x86_capability[CPUID_7_0_EBX] = ebx;
                c->x86_capability[CPUID_7_ECX] = ecx;
        }

        /* Extended state features: level 0x0000000d */
        if (c->cpuid_level >= 0x0000000d) {
                cpuid_count(0x0000000d, 1, &eax, &ebx, &ecx, &edx);

                c->x86_capability[CPUID_D_1_EAX] = eax;
        }

        /* Additional Intel-defined flags: level 0x0000000F */
        if (c->cpuid_level >= 0x0000000F) {

                /* QoS sub-leaf, EAX=0Fh, ECX=0 */
                cpuid_count(0x0000000F, 0, &eax, &ebx, &ecx, &edx);
                c->x86_capability[CPUID_F_0_EDX] = edx;

                if (cpu_has(c, X86_FEATURE_CQM_LLC)) {
                        /* will be overridden if occupancy monitoring exists */
                        c->x86_cache_max_rmid = ebx;

                        /* QoS sub-leaf, EAX=0Fh, ECX=1 */
                        cpuid_count(0x0000000F, 1, &eax, &ebx, &ecx, &edx);
                        c->x86_capability[CPUID_F_1_EDX] = edx;

                        if ((cpu_has(c, X86_FEATURE_CQM_OCCUP_LLC)) ||
                              ((cpu_has(c, X86_FEATURE_CQM_MBM_TOTAL)) ||
                               (cpu_has(c, X86_FEATURE_CQM_MBM_LOCAL)))) {
                                c->x86_cache_max_rmid = ecx;
                                c->x86_cache_occ_scale = ebx;
                        }
                } else {
                        c->x86_cache_max_rmid = -1;
                        c->x86_cache_occ_scale = -1;
                }
        }

        /* AMD-defined flags: level 0x80000001 */
        eax = cpuid_eax(0x80000000);
        c->extended_cpuid_level = eax;

        if ((eax & 0xffff0000) == 0x80000000) {
                if (eax >= 0x80000001) {
                        cpuid(0x80000001, &eax, &ebx, &ecx, &edx);

                        c->x86_capability[CPUID_8000_0001_ECX] = ecx;
                        c->x86_capability[CPUID_8000_0001_EDX] = edx;
                }
        }

        if (c->extended_cpuid_level >= 0x80000007) {
                cpuid(0x80000007, &eax, &ebx, &ecx, &edx);

                c->x86_capability[CPUID_8000_0007_EBX] = ebx;
                c->x86_power = edx;
        }

        if (c->extended_cpuid_level >= 0x80000008) {
                cpuid(0x80000008, &eax, &ebx, &ecx, &edx);

                c->x86_virt_bits = (eax >> 8) & 0xff;
                c->x86_phys_bits = eax & 0xff;
                c->x86_capability[CPUID_8000_0008_EBX] = ebx;
        }
#ifdef CONFIG_X86_32
        else if (cpu_has(c, X86_FEATURE_PAE) || cpu_has(c, X86_FEATURE_PSE36))
                c->x86_phys_bits = 36;
#endif

        if (c->extended_cpuid_level >= 0x8000000a)
                c->x86_capability[CPUID_8000_000A_EDX] = cpuid_edx(0x8000000a);

        init_scattered_cpuid_features(c);

        /*
         * Clear/Set all flags overridden by options, after probe.
         * This needs to happen each time we re-probe, which may happen
         * several times during CPU initialization.
         */
        apply_forced_caps(c);
}

static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_X86_32
        int i;

        /*
         * 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;

        for (i = 0; i < X86_VENDOR_NUM; i++)
                if (cpu_devs[i] && cpu_devs[i]->c_identify) {
                        c->x86_vendor_id[0] = 0;
                        cpu_devs[i]->c_identify(c);
                        if (c->x86_vendor_id[0]) {
                                get_cpu_vendor(c);
                                break;
                        }
                }
#endif
}

/*
 * 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_identify_cpu(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_X86_64
        c->x86_clflush_size = 64;
        c->x86_phys_bits = 36;
        c->x86_virt_bits = 48;
#else
        c->x86_clflush_size = 32;
        c->x86_phys_bits = 32;
        c->x86_virt_bits = 32;
#endif
        c->x86_cache_alignment = c->x86_clflush_size;

        memset(&c->x86_capability, 0, sizeof c->x86_capability);
        c->extended_cpuid_level = 0;

        /* cyrix could have cpuid enabled via c_identify()*/
        if (have_cpuid_p()) {
                cpu_detect(c);
                get_cpu_vendor(c);
                get_cpu_cap(c);
                setup_force_cpu_cap(X86_FEATURE_CPUID);

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

                c->cpu_index = 0;
                filter_cpuid_features(c, false);

                if (this_cpu->c_bsp_init)
                        this_cpu->c_bsp_init(c);
        } else {
                identify_cpu_without_cpuid(c);
                setup_clear_cpu_cap(X86_FEATURE_CPUID);
        }

        setup_force_cpu_cap(X86_FEATURE_ALWAYS);
        fpu__init_system(c);

#ifdef CONFIG_X86_32
        /*
         * Regardless of whether PCID is enumerated, the SDM says
         * that it can't be enabled in 32-bit mode.
         */
        setup_clear_cpu_cap(X86_FEATURE_PCID);
#endif
}

void __init early_cpu_init(void)
{
        const struct cpu_dev *const *cdev;
        int count = 0;

#ifdef CONFIG_PROCESSOR_SELECT
        pr_info("KERNEL supported cpus:\n");
#endif

        for (cdev = __x86_cpu_dev_start; cdev < __x86_cpu_dev_end; cdev++) {
                const struct cpu_dev *cpudev = *cdev;

                if (count >= X86_VENDOR_NUM)
                        break;
                cpu_devs[count] = cpudev;
                count++;

#ifdef CONFIG_PROCESSOR_SELECT
                {
                        unsigned int j;

                        for (j = 0; j < 2; j++) {
                                if (!cpudev->c_ident[j])
                                        continue;
                                pr_info("  %s %s\n", cpudev->c_vendor,
                                        cpudev->c_ident[j]);
                        }
                }
#endif
        }
        early_identify_cpu(&boot_cpu_data);
}

/*
 * The NOPL instruction is supposed to exist on all CPUs of 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. In the latter case it doesn't even *fail* reliably, so
 * probing for it doesn't even work. Disable it completely on 32-bit
 * unless we can find a reliable way to detect all the broken cases.
 * Enable it explicitly on 64-bit for non-constant inputs of cpu_has().
 */
static void detect_nopl(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_X86_32
        clear_cpu_cap(c, X86_FEATURE_NOPL);
#else
        set_cpu_cap(c, X86_FEATURE_NOPL);
#endif
}

static void detect_null_seg_behavior(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_X86_64
        /*
         * Empirically, writing zero to a segment selector on AMD does
         * not clear the base, whereas writing zero to a segment
         * selector on Intel does clear the base.  Intel's behavior
         * allows slightly faster context switches in the common case
         * where GS is unused by the prev and next threads.
         *
         * Since neither vendor documents this anywhere that I can see,
         * detect it directly instead of hardcoding the choice by
         * vendor.
         *
         * I've designated AMD's behavior as the "bug" because it's
         * counterintuitive and less friendly.
         */

        unsigned long old_base, tmp;
        rdmsrl(MSR_FS_BASE, old_base);
        wrmsrl(MSR_FS_BASE, 1);
        loadsegment(fs, 0);
        rdmsrl(MSR_FS_BASE, tmp);
        if (tmp != 0)
                set_cpu_bug(c, X86_BUG_NULL_SEG);
        wrmsrl(MSR_FS_BASE, old_base);
#endif
}

static void generic_identify(struct cpuinfo_x86 *c)
{
        c->extended_cpuid_level = 0;

        if (!have_cpuid_p())
                identify_cpu_without_cpuid(c);

        /* cyrix could have cpuid enabled via c_identify()*/
        if (!have_cpuid_p())
                return;

        cpu_detect(c);

        get_cpu_vendor(c);

        get_cpu_cap(c);

        if (c->cpuid_level >= 0x00000001) {
                c->initial_apicid = (cpuid_ebx(1) >> 24) & 0xFF;
#ifdef CONFIG_X86_32
# ifdef CONFIG_SMP
                c->apicid = apic->phys_pkg_id(c->initial_apicid, 0);
# else
                c->apicid = c->initial_apicid;
# endif
#endif
                c->phys_proc_id = c->initial_apicid;
        }

        get_model_name(c); /* Default name */

        detect_nopl(c);

        detect_null_seg_behavior(c);

        /*
         * ESPFIX is a strange bug.  All real CPUs have it.  Paravirt
         * systems that run Linux at CPL > 0 may or may not have the
         * issue, but, even if they have the issue, there's absolutely
         * nothing we can do about it because we can't use the real IRET
         * instruction.
         *
         * NB: For the time being, only 32-bit kernels support
         * X86_BUG_ESPFIX as such.  64-bit kernels directly choose
         * whether to apply espfix using paravirt hooks.  If any
         * non-paravirt system ever shows up that does *not* have the
         * ESPFIX issue, we can change this.
         */
#ifdef CONFIG_X86_32
# ifdef CONFIG_PARAVIRT
        do {
                extern void native_iret(void);
                if (pv_cpu_ops.iret == native_iret)
                        set_cpu_bug(c, X86_BUG_ESPFIX);
        } while (0);
# else
        set_cpu_bug(c, X86_BUG_ESPFIX);
# endif
#endif
}

static void x86_init_cache_qos(struct cpuinfo_x86 *c)
{
        /*
         * The heavy lifting of max_rmid and cache_occ_scale are handled
         * in get_cpu_cap().  Here we just set the max_rmid for the boot_cpu
         * in case CQM bits really aren't there in this CPU.
         */
        if (c != &boot_cpu_data) {
                boot_cpu_data.x86_cache_max_rmid =
                        min(boot_cpu_data.x86_cache_max_rmid,
                            c->x86_cache_max_rmid);
        }
}

/*
 * Validate that ACPI/mptables have the same information about the
 * effective APIC id and update the package map.
 */
static void validate_apic_and_package_id(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_SMP
        unsigned int apicid, cpu = smp_processor_id();

        apicid = apic->cpu_present_to_apicid(cpu);

        if (apicid != c->apicid) {
                pr_err(FW_BUG "CPU%u: APIC id mismatch. Firmware: %x APIC: %x\n",
                       cpu, apicid, c->initial_apicid);
        }
        BUG_ON(topology_update_package_map(c->phys_proc_id, cpu));
#else
        c->logical_proc_id = 0;
#endif
}

/*
 * This does the hard work of actually picking apart the CPU stuff...
 */
static void 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->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_coreid_bits = 0;
        c->cu_id = 0xff;
#ifdef CONFIG_X86_64
        c->x86_clflush_size = 64;
        c->x86_phys_bits = 36;
        c->x86_virt_bits = 48;
#else
        c->cpuid_level = -1;    /* CPUID not detected */
        c->x86_clflush_size = 32;
        c->x86_phys_bits = 32;
        c->x86_virt_bits = 32;
#endif
        c->x86_cache_alignment = c->x86_clflush_size;
        memset(&c->x86_capability, 0, sizeof c->x86_capability);

        generic_identify(c);

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

        /* Clear/Set all flags overridden by options, after probe */
        apply_forced_caps(c);

#ifdef CONFIG_X86_64
        c->apicid = apic->phys_pkg_id(c->initial_apicid, 0);
#endif

        /*
         * 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);

        /* Set up SMEP/SMAP */
        setup_smep(c);
        setup_smap(c);

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

        /* Filter out anything that depends on CPUID levels we don't have */
        filter_cpuid_features(c, true);

        /* If the model name is still unset, do table lookup. */
        if (!c->x86_model_id[0]) {
                const 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);
        }

#ifdef CONFIG_X86_64
        detect_ht(c);
#endif

        x86_init_rdrand(c);
        x86_init_cache_qos(c);
        setup_pku(c);

        /*
         * Clear/Set all flags overridden by options, need do it
         * before following smp all cpus cap AND.
         */
        apply_forced_caps(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];

                /* OR, i.e. replicate the bug flags */
                for (i = NCAPINTS; i < NCAPINTS + NBUGINTS; i++)
                        c->x86_capability[i] |= boot_cpu_data.x86_capability[i];
        }

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

        select_idle_routine(c);

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

/*
 * Set up the CPU state needed to execute SYSENTER/SYSEXIT instructions
 * on 32-bit kernels:
 */
#ifdef CONFIG_X86_32
void enable_sep_cpu(void)
{
        struct tss_struct *tss;
        int cpu;

        if (!boot_cpu_has(X86_FEATURE_SEP))
                return;

        cpu = get_cpu();
        tss = &per_cpu(cpu_tss, cpu);

        /*
         * We cache MSR_IA32_SYSENTER_CS's value in the TSS's ss1 field --
         * see the big comment in struct x86_hw_tss's definition.
         */

        tss->x86_tss.ss1 = __KERNEL_CS;
        wrmsr(MSR_IA32_SYSENTER_CS, tss->x86_tss.ss1, 0);

        wrmsr(MSR_IA32_SYSENTER_ESP,
              (unsigned long)tss + offsetofend(struct tss_struct, SYSENTER_stack),
              0);

        wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long)entry_SYSENTER_32, 0);

        put_cpu();
}
#endif

void __init identify_boot_cpu(void)
{
        identify_cpu(&boot_cpu_data);
#ifdef CONFIG_X86_32
        sysenter_setup();
        enable_sep_cpu();
#endif
        cpu_detect_tlb(&boot_cpu_data);
}

void identify_secondary_cpu(struct cpuinfo_x86 *c)
{
        BUG_ON(c == &boot_cpu_data);
        identify_cpu(c);
#ifdef CONFIG_X86_32
        enable_sep_cpu();
#endif
        mtrr_ap_init();
        validate_apic_and_package_id(c);
}

static __init int setup_noclflush(char *arg)
{
        setup_clear_cpu_cap(X86_FEATURE_CLFLUSH);
        setup_clear_cpu_cap(X86_FEATURE_CLFLUSHOPT);
        return 1;
}
__setup("noclflush", setup_noclflush);

void print_cpu_info(struct cpuinfo_x86 *c)
{
        const 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 && !strstr(c->x86_model_id, vendor))
                pr_cont("%s ", vendor);

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

        pr_cont(" (family: 0x%x, model: 0x%x", c->x86, c->x86_model);

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

/*
 * clearcpuid= was already parsed in fpu__init_parse_early_param.
 * But we need to keep a dummy __setup around otherwise it would
 * show up as an environment variable for init.
 */
static __init int setup_clearcpuid(char *arg)
{
        return 1;
}
__setup("clearcpuid=", setup_clearcpuid);

#ifdef CONFIG_X86_64
DEFINE_PER_CPU_FIRST(union irq_stack_union,
                     irq_stack_union) __aligned(PAGE_SIZE) __visible;

/*
 * The following percpu variables are hot.  Align current_task to
 * cacheline size such that they fall in the same cacheline.
 */
DEFINE_PER_CPU(struct task_struct *, current_task) ____cacheline_aligned =
        &init_task;
EXPORT_PER_CPU_SYMBOL(current_task);

DEFINE_PER_CPU(char *, irq_stack_ptr) =
        init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE;

DEFINE_PER_CPU(unsigned int, irq_count) __visible = -1;

DEFINE_PER_CPU(int, __preempt_count) = INIT_PREEMPT_COUNT;
EXPORT_PER_CPU_SYMBOL(__preempt_count);

/*
 * Special IST stacks which the CPU switches to when it calls
 * an IST-marked descriptor entry. Up to 7 stacks (hardware
 * limit), all of them are 4K, except the debug stack which
 * is 8K.
 */
static const unsigned int exception_stack_sizes[N_EXCEPTION_STACKS] = {
          [0 ... N_EXCEPTION_STACKS - 1]        = EXCEPTION_STKSZ,
          [DEBUG_STACK - 1]                     = DEBUG_STKSZ
};

static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks
        [(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]);

/* May not be marked __init: used by software suspend */
void syscall_init(void)
{
        wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);
        wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64);

#ifdef CONFIG_IA32_EMULATION
        wrmsrl(MSR_CSTAR, (unsigned long)entry_SYSCALL_compat);
        /*
         * This only works on Intel CPUs.
         * On AMD CPUs these MSRs are 32-bit, CPU truncates MSR_IA32_SYSENTER_EIP.
         * This does not cause SYSENTER to jump to the wrong location, because
         * AMD doesn't allow SYSENTER in long mode (either 32- or 64-bit).
         */
        wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
        wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL);
        wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)entry_SYSENTER_compat);
#else
        wrmsrl(MSR_CSTAR, (unsigned long)ignore_sysret);
        wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG);
        wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL);
        wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL);
#endif

        /* Flags to clear on syscall */
        wrmsrl(MSR_SYSCALL_MASK,
               X86_EFLAGS_TF|X86_EFLAGS_DF|X86_EFLAGS_IF|
               X86_EFLAGS_IOPL|X86_EFLAGS_AC|X86_EFLAGS_NT);
}

/*
 * 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);

static DEFINE_PER_CPU(unsigned long, debug_stack_addr);
DEFINE_PER_CPU(int, debug_stack_usage);

int is_debug_stack(unsigned long addr)
{
        return __this_cpu_read(debug_stack_usage) ||
                (addr <= __this_cpu_read(debug_stack_addr) &&
                 addr > (__this_cpu_read(debug_stack_addr) - DEBUG_STKSZ));
}
NOKPROBE_SYMBOL(is_debug_stack);

DEFINE_PER_CPU(u32, debug_idt_ctr);

void debug_stack_set_zero(void)
{
        this_cpu_inc(debug_idt_ctr);
        load_current_idt();
}
NOKPROBE_SYMBOL(debug_stack_set_zero);

void debug_stack_reset(void)
{
        if (WARN_ON(!this_cpu_read(debug_idt_ctr)))
                return;
        if (this_cpu_dec_return(debug_idt_ctr) == 0)
                load_current_idt();
}
NOKPROBE_SYMBOL(debug_stack_reset);

#else   /* CONFIG_X86_64 */

DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;
EXPORT_PER_CPU_SYMBOL(current_task);
DEFINE_PER_CPU(int, __preempt_count) = INIT_PREEMPT_COUNT;
EXPORT_PER_CPU_SYMBOL(__preempt_count);

/*
 * On x86_32, vm86 modifies tss.sp0, so sp0 isn't a reliable way to find
 * the top of the kernel stack.  Use an extra percpu variable to track the
 * top of the kernel stack directly.
 */
DEFINE_PER_CPU(unsigned long, cpu_current_top_of_stack) =
        (unsigned long)&init_thread_union + THREAD_SIZE;
EXPORT_PER_CPU_SYMBOL(cpu_current_top_of_stack);

#ifdef CONFIG_CC_STACKPROTECTOR
DEFINE_PER_CPU_ALIGNED(struct stack_canary, stack_canary);
#endif

#endif  /* CONFIG_X86_64 */

/*
 * Clear all 6 debug registers:
 */
static void clear_all_debug_regs(void)
{
        int i;

        for (i = 0; i < 8; i++) {
                /* Ignore db4, db5 */
                if ((i == 4) || (i == 5))
                        continue;

                set_debugreg(0, i);
        }
}

#ifdef CONFIG_KGDB
/*
 * Restore debug regs if using kgdbwait and you have a kernel debugger
 * connection established.
 */
static void dbg_restore_debug_regs(void)
{
        if (unlikely(kgdb_connected && arch_kgdb_ops.correct_hw_break))
                arch_kgdb_ops.correct_hw_break();
}
#else /* ! CONFIG_KGDB */
#define dbg_restore_debug_regs()
#endif /* ! CONFIG_KGDB */

static void wait_for_master_cpu(int cpu)
{
#ifdef CONFIG_SMP
        /*
         * wait for ACK from master CPU before continuing
         * with AP initialization
         */
        WARN_ON(cpumask_test_and_set_cpu(cpu, cpu_initialized_mask));
        while (!cpumask_test_cpu(cpu, cpu_callout_mask))
                cpu_relax();
#endif
}

/*
 * 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 for 64 bit
 */
#ifdef CONFIG_X86_64

void cpu_init(void)
{
        struct orig_ist *oist;
        struct task_struct *me;
        struct tss_struct *t;
        unsigned long v;
        int cpu = raw_smp_processor_id();
        int i;

        wait_for_master_cpu(cpu);

        /*
         * Initialize the CR4 shadow before doing anything that could
         * try to read it.
         */
        cr4_init_shadow();

        if (cpu)
                load_ucode_ap();

        t = &per_cpu(cpu_tss, cpu);
        oist = &per_cpu(orig_ist, cpu);

#ifdef CONFIG_NUMA
        if (this_cpu_read(numa_node) == 0 &&
            early_cpu_to_node(cpu) != NUMA_NO_NODE)
                set_numa_node(early_cpu_to_node(cpu));
#endif

        me = current;

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

        cr4_clear_bits(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(cpu);
        loadsegment(fs, 0);

        load_current_idt();

        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();

        x86_configure_nx();
        x2apic_setup();

        /*
         * set up and load the per-CPU TSS
         */
        if (!oist->ist[0]) {
                char *estacks = per_cpu(exception_stacks, cpu);

                for (v = 0; v < N_EXCEPTION_STACKS; v++) {
                        estacks += exception_stack_sizes[v];
                        oist->ist[v] = t->x86_tss.ist[v] =
                                        (unsigned long)estacks;
                        if (v == DEBUG_STACK-1)
                                per_cpu(debug_stack_addr, cpu) = (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;

        mmgrab(&init_mm);
        me->active_mm = &init_mm;
        BUG_ON(me->mm);
        initialize_tlbstate_and_flush();
        enter_lazy_tlb(&init_mm, me);

        /*
         * Initialize the TSS.  Don't bother initializing sp0, as the initial
         * task never enters user mode.
         */
        set_tss_desc(cpu, t);
        load_TR_desc();

        load_mm_ldt(&init_mm);

        clear_all_debug_regs();
        dbg_restore_debug_regs();

        fpu__init_cpu();

        if (is_uv_system())
                uv_cpu_init();

        setup_fixmap_gdt(cpu);
        load_fixmap_gdt(cpu);
}

#else

void cpu_init(void)
{
        int cpu = smp_processor_id();
        struct task_struct *curr = current;
        struct tss_struct *t = &per_cpu(cpu_tss, cpu);

        wait_for_master_cpu(cpu);

        /*
         * Initialize the CR4 shadow before doing anything that could
         * try to read it.
         */
        cr4_init_shadow();

        show_ucode_info_early();

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

        if (cpu_feature_enabled(X86_FEATURE_VME) ||
            boot_cpu_has(X86_FEATURE_TSC) ||
            boot_cpu_has(X86_FEATURE_DE))
                cr4_clear_bits(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);

        load_current_idt();
        switch_to_new_gdt(cpu);

        /*
         * Set up and load the per-CPU TSS and LDT
         */
        mmgrab(&init_mm);
        curr->active_mm = &init_mm;
        BUG_ON(curr->mm);
        initialize_tlbstate_and_flush();
        enter_lazy_tlb(&init_mm, curr);

        /*
         * Initialize the TSS.  Don't bother initializing sp0, as the initial
         * task never enters user mode.
         */
        set_tss_desc(cpu, t);
        load_TR_desc();

        load_mm_ldt(&init_mm);

        t->x86_tss.io_bitmap_base = offsetof(struct tss_struct, io_bitmap);

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

        clear_all_debug_regs();
        dbg_restore_debug_regs();

        fpu__init_cpu();

        setup_fixmap_gdt(cpu);
        load_fixmap_gdt(cpu);
}
#endif

static void bsp_resume(void)
{
        if (this_cpu->c_bsp_resume)
                this_cpu->c_bsp_resume(&boot_cpu_data);
}

static struct syscore_ops cpu_syscore_ops = {
        .resume         = bsp_resume,
};

static int __init init_cpu_syscore(void)
{
        register_syscore_ops(&cpu_syscore_ops);
        return 0;
}
core_initcall(init_cpu_syscore);