x86: fix cpu hotplug crash

[linux-2.6/mini2440.git] / arch / x86 / kernel / smpboot.c

/*
 *      x86 SMP booting functions
 *
 *      (c) 1995 Alan Cox, Building #3 <alan@redhat.com>
 *      (c) 1998, 1999, 2000 Ingo Molnar <mingo@redhat.com>
 *      Copyright 2001 Andi Kleen, SuSE Labs.
 *
 *      Much of the core SMP work is based on previous work by Thomas Radke, to
 *      whom a great many thanks are extended.
 *
 *      Thanks to Intel for making available several different Pentium,
 *      Pentium Pro and Pentium-II/Xeon MP machines.
 *      Original development of Linux SMP code supported by Caldera.
 *
 *      This code is released under the GNU General Public License version 2 or
 *      later.
 *
 *      Fixes
 *              Felix Koop      :       NR_CPUS used properly
 *              Jose Renau      :       Handle single CPU case.
 *              Alan Cox        :       By repeated request 8) - Total BogoMIPS report.
 *              Greg Wright     :       Fix for kernel stacks panic.
 *              Erich Boleyn    :       MP v1.4 and additional changes.
 *      Matthias Sattler        :       Changes for 2.1 kernel map.
 *      Michel Lespinasse       :       Changes for 2.1 kernel map.
 *      Michael Chastain        :       Change trampoline.S to gnu as.
 *              Alan Cox        :       Dumb bug: 'B' step PPro's are fine
 *              Ingo Molnar     :       Added APIC timers, based on code
 *                                      from Jose Renau
 *              Ingo Molnar     :       various cleanups and rewrites
 *              Tigran Aivazian :       fixed "0.00 in /proc/uptime on SMP" bug.
 *      Maciej W. Rozycki       :       Bits for genuine 82489DX APICs
 *      Andi Kleen              :       Changed for SMP boot into long mode.
 *              Martin J. Bligh :       Added support for multi-quad systems
 *              Dave Jones      :       Report invalid combinations of Athlon CPUs.
 *              Rusty Russell   :       Hacked into shape for new "hotplug" boot process.
 *      Andi Kleen              :       Converted to new state machine.
 *      Ashok Raj               :       CPU hotplug support
 *      Glauber Costa           :       i386 and x86_64 integration
 */

#include <linux/init.h>
#include <linux/smp.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/percpu.h>
#include <linux/bootmem.h>
#include <linux/err.h>
#include <linux/nmi.h>

#include <asm/acpi.h>
#include <asm/desc.h>
#include <asm/nmi.h>
#include <asm/irq.h>
#include <asm/smp.h>
#include <asm/trampoline.h>
#include <asm/cpu.h>
#include <asm/numa.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/mtrr.h>
#include <asm/nmi.h>
#include <asm/vmi.h>
#include <asm/genapic.h>
#include <linux/mc146818rtc.h>

#include <mach_apic.h>
#include <mach_wakecpu.h>
#include <smpboot_hooks.h>

/*
 * FIXME: For x86_64, those are defined in other files. But moving them here,
 * would make the setup areas dependent on smp, which is a loss. When we
 * integrate apic between arches, we can probably do a better job, but
 * right now, they'll stay here -- glommer
 */

/* which logical CPU number maps to which CPU (physical APIC ID) */
u16 x86_cpu_to_apicid_init[NR_CPUS] __initdata =
                        { [0 ... NR_CPUS-1] = BAD_APICID };
void *x86_cpu_to_apicid_early_ptr;

u16 x86_bios_cpu_apicid_init[NR_CPUS] __initdata
                                = { [0 ... NR_CPUS-1] = BAD_APICID };
void *x86_bios_cpu_apicid_early_ptr;

#ifdef CONFIG_X86_32
u8 apicid_2_node[MAX_APICID];
static int low_mappings;
#endif

/* State of each CPU */
DEFINE_PER_CPU(int, cpu_state) = { 0 };

/* Store all idle threads, this can be reused instead of creating
* a new thread. Also avoids complicated thread destroy functionality
* for idle threads.
*/
#ifdef CONFIG_HOTPLUG_CPU
/*
 * Needed only for CONFIG_HOTPLUG_CPU because __cpuinitdata is
 * removed after init for !CONFIG_HOTPLUG_CPU.
 */
static DEFINE_PER_CPU(struct task_struct *, idle_thread_array);
#define get_idle_for_cpu(x)      (per_cpu(idle_thread_array, x))
#define set_idle_for_cpu(x, p)   (per_cpu(idle_thread_array, x) = (p))
#else
struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;
#define get_idle_for_cpu(x)      (idle_thread_array[(x)])
#define set_idle_for_cpu(x, p)   (idle_thread_array[(x)] = (p))
#endif

/* Number of siblings per CPU package */
int smp_num_siblings = 1;
EXPORT_SYMBOL(smp_num_siblings);

/* Last level cache ID of each logical CPU */
DEFINE_PER_CPU(u16, cpu_llc_id) = BAD_APICID;

/* bitmap of online cpus */
cpumask_t cpu_online_map __read_mostly;
EXPORT_SYMBOL(cpu_online_map);

cpumask_t cpu_callin_map;
cpumask_t cpu_callout_map;
cpumask_t cpu_possible_map;
EXPORT_SYMBOL(cpu_possible_map);

/* representing HT siblings of each logical CPU */
DEFINE_PER_CPU(cpumask_t, cpu_sibling_map);
EXPORT_PER_CPU_SYMBOL(cpu_sibling_map);

/* representing HT and core siblings of each logical CPU */
DEFINE_PER_CPU(cpumask_t, cpu_core_map);
EXPORT_PER_CPU_SYMBOL(cpu_core_map);

/* Per CPU bogomips and other parameters */
DEFINE_PER_CPU_SHARED_ALIGNED(struct cpuinfo_x86, cpu_info);
EXPORT_PER_CPU_SYMBOL(cpu_info);

static atomic_t init_deasserted;

static int boot_cpu_logical_apicid;

/* representing cpus for which sibling maps can be computed */
static cpumask_t cpu_sibling_setup_map;

/* Set if we find a B stepping CPU */
int __cpuinitdata smp_b_stepping;

#if defined(CONFIG_NUMA) && defined(CONFIG_X86_32)

/* which logical CPUs are on which nodes */
cpumask_t node_to_cpumask_map[MAX_NUMNODES] __read_mostly =
                                { [0 ... MAX_NUMNODES-1] = CPU_MASK_NONE };
EXPORT_SYMBOL(node_to_cpumask_map);
/* which node each logical CPU is on */
int cpu_to_node_map[NR_CPUS] __read_mostly = { [0 ... NR_CPUS-1] = 0 };
EXPORT_SYMBOL(cpu_to_node_map);

/* set up a mapping between cpu and node. */
static void map_cpu_to_node(int cpu, int node)
{
        printk(KERN_INFO "Mapping cpu %d to node %d\n", cpu, node);
        cpu_set(cpu, node_to_cpumask_map[node]);
        cpu_to_node_map[cpu] = node;
}

/* undo a mapping between cpu and node. */
static void unmap_cpu_to_node(int cpu)
{
        int node;

        printk(KERN_INFO "Unmapping cpu %d from all nodes\n", cpu);
        for (node = 0; node < MAX_NUMNODES; node++)
                cpu_clear(cpu, node_to_cpumask_map[node]);
        cpu_to_node_map[cpu] = 0;
}
#else /* !(CONFIG_NUMA && CONFIG_X86_32) */
#define map_cpu_to_node(cpu, node)      ({})
#define unmap_cpu_to_node(cpu)  ({})
#endif

#ifdef CONFIG_X86_32
u8 cpu_2_logical_apicid[NR_CPUS] __read_mostly =
                                        { [0 ... NR_CPUS-1] = BAD_APICID };

static void map_cpu_to_logical_apicid(void)
{
        int cpu = smp_processor_id();
        int apicid = logical_smp_processor_id();
        int node = apicid_to_node(apicid);

        if (!node_online(node))
                node = first_online_node;

        cpu_2_logical_apicid[cpu] = apicid;
        map_cpu_to_node(cpu, node);
}

static void unmap_cpu_to_logical_apicid(int cpu)
{
        cpu_2_logical_apicid[cpu] = BAD_APICID;
        unmap_cpu_to_node(cpu);
}
#else
#define unmap_cpu_to_logical_apicid(cpu) do {} while (0)
#define map_cpu_to_logical_apicid()  do {} while (0)
#endif

/*
 * Report back to the Boot Processor.
 * Running on AP.
 */
static void __cpuinit smp_callin(void)
{
        int cpuid, phys_id;
        unsigned long timeout;

        /*
         * If waken up by an INIT in an 82489DX configuration
         * we may get here before an INIT-deassert IPI reaches
         * our local APIC.  We have to wait for the IPI or we'll
         * lock up on an APIC access.
         */
        wait_for_init_deassert(&init_deasserted);

        /*
         * (This works even if the APIC is not enabled.)
         */
        phys_id = GET_APIC_ID(read_apic_id());
        cpuid = smp_processor_id();
        if (cpu_isset(cpuid, cpu_callin_map)) {
                panic("%s: phys CPU#%d, CPU#%d already present??\n", __func__,
                                        phys_id, cpuid);
        }
        Dprintk("CPU#%d (phys ID: %d) waiting for CALLOUT\n", cpuid, phys_id);

        /*
         * STARTUP IPIs are fragile beasts as they might sometimes
         * trigger some glue motherboard logic. Complete APIC bus
         * silence for 1 second, this overestimates the time the
         * boot CPU is spending to send the up to 2 STARTUP IPIs
         * by a factor of two. This should be enough.
         */

        /*
         * Waiting 2s total for startup (udelay is not yet working)
         */
        timeout = jiffies + 2*HZ;
        while (time_before(jiffies, timeout)) {
                /*
                 * Has the boot CPU finished it's STARTUP sequence?
                 */
                if (cpu_isset(cpuid, cpu_callout_map))
                        break;
                cpu_relax();
        }

        if (!time_before(jiffies, timeout)) {
                panic("%s: CPU%d started up but did not get a callout!\n",
                      __func__, cpuid);
        }

        /*
         * the boot CPU has finished the init stage and is spinning
         * on callin_map until we finish. We are free to set up this
         * CPU, first the APIC. (this is probably redundant on most
         * boards)
         */

        Dprintk("CALLIN, before setup_local_APIC().\n");
        smp_callin_clear_local_apic();
        setup_local_APIC();
        end_local_APIC_setup();
        map_cpu_to_logical_apicid();

        /*
         * Get our bogomips.
         *
         * Need to enable IRQs because it can take longer and then
         * the NMI watchdog might kill us.
         */
        local_irq_enable();
        calibrate_delay();
        local_irq_disable();
        Dprintk("Stack at about %p\n", &cpuid);

        /*
         * Save our processor parameters
         */
        smp_store_cpu_info(cpuid);

        /*
         * Allow the master to continue.
         */
        cpu_set(cpuid, cpu_callin_map);
}

/*
 * Activate a secondary processor.
 */
static void __cpuinit start_secondary(void *unused)
{
        /*
         * Don't put *anything* before cpu_init(), SMP booting is too
         * fragile that we want to limit the things done here to the
         * most necessary things.
         */
#ifdef CONFIG_VMI
        vmi_bringup();
#endif
        cpu_init();
        preempt_disable();
        smp_callin();

        /* otherwise gcc will move up smp_processor_id before the cpu_init */
        barrier();
        /*
         * Check TSC synchronization with the BP:
         */
        check_tsc_sync_target();

        if (nmi_watchdog == NMI_IO_APIC) {
                disable_8259A_irq(0);
                enable_NMI_through_LVT0();
                enable_8259A_irq(0);
        }

#ifdef CONFIG_X86_32
        while (low_mappings)
                cpu_relax();
        __flush_tlb_all();
#endif

        /* This must be done before setting cpu_online_map */
        set_cpu_sibling_map(raw_smp_processor_id());
        wmb();

        /*
         * We need to hold call_lock, so there is no inconsistency
         * between the time smp_call_function() determines number of
         * IPI recipients, and the time when the determination is made
         * for which cpus receive the IPI. Holding this
         * lock helps us to not include this cpu in a currently in progress
         * smp_call_function().
         */
        lock_ipi_call_lock();
#ifdef CONFIG_X86_64
        spin_lock(&vector_lock);

        /* Setup the per cpu irq handling data structures */
        __setup_vector_irq(smp_processor_id());
        /*
         * Allow the master to continue.
         */
        spin_unlock(&vector_lock);
#endif
        cpu_set(smp_processor_id(), cpu_online_map);
        unlock_ipi_call_lock();
        per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;

        setup_secondary_clock();

        wmb();
        cpu_idle();
}

#ifdef CONFIG_X86_32
/*
 * Everything has been set up for the secondary
 * CPUs - they just need to reload everything
 * from the task structure
 * This function must not return.
 */
void __devinit initialize_secondary(void)
{
        /*
         * We don't actually need to load the full TSS,
         * basically just the stack pointer and the ip.
         */

        asm volatile(
                "movl %0,%%esp\n\t"
                "jmp *%1"
                :
                :"m" (current->thread.sp), "m" (current->thread.ip));
}
#endif

static void __cpuinit smp_apply_quirks(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_X86_32
        /*
         * Mask B, Pentium, but not Pentium MMX
         */
        if (c->x86_vendor == X86_VENDOR_INTEL &&
            c->x86 == 5 &&
            c->x86_mask >= 1 && c->x86_mask <= 4 &&
            c->x86_model <= 3)
                /*
                 * Remember we have B step Pentia with bugs
                 */
                smp_b_stepping = 1;

        /*
         * Certain Athlons might work (for various values of 'work') in SMP
         * but they are not certified as MP capable.
         */
        if ((c->x86_vendor == X86_VENDOR_AMD) && (c->x86 == 6)) {

                if (num_possible_cpus() == 1)
                        goto valid_k7;

                /* Athlon 660/661 is valid. */
                if ((c->x86_model == 6) && ((c->x86_mask == 0) ||
                    (c->x86_mask == 1)))
                        goto valid_k7;

                /* Duron 670 is valid */
                if ((c->x86_model == 7) && (c->x86_mask == 0))
                        goto valid_k7;

                /*
                 * Athlon 662, Duron 671, and Athlon >model 7 have capability
                 * bit. It's worth noting that the A5 stepping (662) of some
                 * Athlon XP's have the MP bit set.
                 * See http://www.heise.de/newsticker/data/jow-18.10.01-000 for
                 * more.
                 */
                if (((c->x86_model == 6) && (c->x86_mask >= 2)) ||
                    ((c->x86_model == 7) && (c->x86_mask >= 1)) ||
                     (c->x86_model > 7))
                        if (cpu_has_mp)
                                goto valid_k7;

                /* If we get here, not a certified SMP capable AMD system. */
                add_taint(TAINT_UNSAFE_SMP);
        }

valid_k7:
        ;
#endif
}

static void __cpuinit smp_checks(void)
{
        if (smp_b_stepping)
                printk(KERN_WARNING "WARNING: SMP operation may be unreliable"
                                    "with B stepping processors.\n");

        /*
         * Don't taint if we are running SMP kernel on a single non-MP
         * approved Athlon
         */
        if (tainted & TAINT_UNSAFE_SMP) {
                if (num_online_cpus())
                        printk(KERN_INFO "WARNING: This combination of AMD"
                                "processors is not suitable for SMP.\n");
                else
                        tainted &= ~TAINT_UNSAFE_SMP;
        }
}

/*
 * The bootstrap kernel entry code has set these up. Save them for
 * a given CPU
 */

void __cpuinit smp_store_cpu_info(int id)
{
        struct cpuinfo_x86 *c = &cpu_data(id);

        *c = boot_cpu_data;
        c->cpu_index = id;
        if (id != 0)
                identify_secondary_cpu(c);
        smp_apply_quirks(c);
}


void __cpuinit set_cpu_sibling_map(int cpu)
{
        int i;
        struct cpuinfo_x86 *c = &cpu_data(cpu);

        cpu_set(cpu, cpu_sibling_setup_map);

        if (smp_num_siblings > 1) {
                for_each_cpu_mask(i, cpu_sibling_setup_map) {
                        if (c->phys_proc_id == cpu_data(i).phys_proc_id &&
                            c->cpu_core_id == cpu_data(i).cpu_core_id) {
                                cpu_set(i, per_cpu(cpu_sibling_map, cpu));
                                cpu_set(cpu, per_cpu(cpu_sibling_map, i));
                                cpu_set(i, per_cpu(cpu_core_map, cpu));
                                cpu_set(cpu, per_cpu(cpu_core_map, i));
                                cpu_set(i, c->llc_shared_map);
                                cpu_set(cpu, cpu_data(i).llc_shared_map);
                        }
                }
        } else {
                cpu_set(cpu, per_cpu(cpu_sibling_map, cpu));
        }

        cpu_set(cpu, c->llc_shared_map);

        if (current_cpu_data.x86_max_cores == 1) {
                per_cpu(cpu_core_map, cpu) = per_cpu(cpu_sibling_map, cpu);
                c->booted_cores = 1;
                return;
        }

        for_each_cpu_mask(i, cpu_sibling_setup_map) {
                if (per_cpu(cpu_llc_id, cpu) != BAD_APICID &&
                    per_cpu(cpu_llc_id, cpu) == per_cpu(cpu_llc_id, i)) {
                        cpu_set(i, c->llc_shared_map);
                        cpu_set(cpu, cpu_data(i).llc_shared_map);
                }
                if (c->phys_proc_id == cpu_data(i).phys_proc_id) {
                        cpu_set(i, per_cpu(cpu_core_map, cpu));
                        cpu_set(cpu, per_cpu(cpu_core_map, i));
                        /*
                         *  Does this new cpu bringup a new core?
                         */
                        if (cpus_weight(per_cpu(cpu_sibling_map, cpu)) == 1) {
                                /*
                                 * for each core in package, increment
                                 * the booted_cores for this new cpu
                                 */
                                if (first_cpu(per_cpu(cpu_sibling_map, i)) == i)
                                        c->booted_cores++;
                                /*
                                 * increment the core count for all
                                 * the other cpus in this package
                                 */
                                if (i != cpu)
                                        cpu_data(i).booted_cores++;
                        } else if (i != cpu && !c->booted_cores)
                                c->booted_cores = cpu_data(i).booted_cores;
                }
        }
}

/* maps the cpu to the sched domain representing multi-core */
cpumask_t cpu_coregroup_map(int cpu)
{
        struct cpuinfo_x86 *c = &cpu_data(cpu);
        /*
         * For perf, we return last level cache shared map.
         * And for power savings, we return cpu_core_map
         */
        if (sched_mc_power_savings || sched_smt_power_savings)
                return per_cpu(cpu_core_map, cpu);
        else
                return c->llc_shared_map;
}

#ifdef CONFIG_X86_32
/*
 * We are called very early to get the low memory for the
 * SMP bootup trampoline page.
 */
void __init smp_alloc_memory(void)
{
        trampoline_base = alloc_bootmem_low_pages(PAGE_SIZE);
        /*
         * Has to be in very low memory so we can execute
         * real-mode AP code.
         */
        if (__pa(trampoline_base) >= 0x9F000)
                BUG();
}
#endif

static void impress_friends(void)
{
        int cpu;
        unsigned long bogosum = 0;
        /*
         * Allow the user to impress friends.
         */
        Dprintk("Before bogomips.\n");
        for_each_possible_cpu(cpu)
                if (cpu_isset(cpu, cpu_callout_map))
                        bogosum += cpu_data(cpu).loops_per_jiffy;
        printk(KERN_INFO
                "Total of %d processors activated (%lu.%02lu BogoMIPS).\n",
                num_online_cpus(),
                bogosum/(500000/HZ),
                (bogosum/(5000/HZ))%100);

        Dprintk("Before bogocount - setting activated=1.\n");
}

static inline void __inquire_remote_apic(int apicid)
{
        unsigned i, regs[] = { APIC_ID >> 4, APIC_LVR >> 4, APIC_SPIV >> 4 };
        char *names[] = { "ID", "VERSION", "SPIV" };
        int timeout;
        u32 status;

        printk(KERN_INFO "Inquiring remote APIC #%d...\n", apicid);

        for (i = 0; i < ARRAY_SIZE(regs); i++) {
                printk(KERN_INFO "... APIC #%d %s: ", apicid, names[i]);

                /*
                 * Wait for idle.
                 */
                status = safe_apic_wait_icr_idle();
                if (status)
                        printk(KERN_CONT
                               "a previous APIC delivery may have failed\n");

                apic_write_around(APIC_ICR2, SET_APIC_DEST_FIELD(apicid));
                apic_write_around(APIC_ICR, APIC_DM_REMRD | regs[i]);

                timeout = 0;
                do {
                        udelay(100);
                        status = apic_read(APIC_ICR) & APIC_ICR_RR_MASK;
                } while (status == APIC_ICR_RR_INPROG && timeout++ < 1000);

                switch (status) {
                case APIC_ICR_RR_VALID:
                        status = apic_read(APIC_RRR);
                        printk(KERN_CONT "%08x\n", status);
                        break;
                default:
                        printk(KERN_CONT "failed\n");
                }
        }
}

#ifdef WAKE_SECONDARY_VIA_NMI
/*
 * Poke the other CPU in the eye via NMI to wake it up. Remember that the normal
 * INIT, INIT, STARTUP sequence will reset the chip hard for us, and this
 * won't ... remember to clear down the APIC, etc later.
 */
static int __devinit
wakeup_secondary_cpu(int logical_apicid, unsigned long start_eip)
{
        unsigned long send_status, accept_status = 0;
        int maxlvt;

        /* Target chip */
        apic_write_around(APIC_ICR2, SET_APIC_DEST_FIELD(logical_apicid));

        /* Boot on the stack */
        /* Kick the second */
        apic_write_around(APIC_ICR, APIC_DM_NMI | APIC_DEST_LOGICAL);

        Dprintk("Waiting for send to finish...\n");
        send_status = safe_apic_wait_icr_idle();

        /*
         * Give the other CPU some time to accept the IPI.
         */
        udelay(200);
        /*
         * Due to the Pentium erratum 3AP.
         */
        maxlvt = lapic_get_maxlvt();
        if (maxlvt > 3) {
                apic_read_around(APIC_SPIV);
                apic_write(APIC_ESR, 0);
        }
        accept_status = (apic_read(APIC_ESR) & 0xEF);
        Dprintk("NMI sent.\n");

        if (send_status)
                printk(KERN_ERR "APIC never delivered???\n");
        if (accept_status)
                printk(KERN_ERR "APIC delivery error (%lx).\n", accept_status);

        return (send_status | accept_status);
}
#endif  /* WAKE_SECONDARY_VIA_NMI */

#ifdef WAKE_SECONDARY_VIA_INIT
static int __devinit
wakeup_secondary_cpu(int phys_apicid, unsigned long start_eip)
{
        unsigned long send_status, accept_status = 0;
        int maxlvt, num_starts, j;

        if (get_uv_system_type() == UV_NON_UNIQUE_APIC) {
                send_status = uv_wakeup_secondary(phys_apicid, start_eip);
                atomic_set(&init_deasserted, 1);
                return send_status;
        }

        /*
         * Be paranoid about clearing APIC errors.
         */
        if (APIC_INTEGRATED(apic_version[phys_apicid])) {
                apic_read_around(APIC_SPIV);
                apic_write(APIC_ESR, 0);
                apic_read(APIC_ESR);
        }

        Dprintk("Asserting INIT.\n");

        /*
         * Turn INIT on target chip
         */
        apic_write_around(APIC_ICR2, SET_APIC_DEST_FIELD(phys_apicid));

        /*
         * Send IPI
         */
        apic_write_around(APIC_ICR, APIC_INT_LEVELTRIG | APIC_INT_ASSERT
                                | APIC_DM_INIT);

        Dprintk("Waiting for send to finish...\n");
        send_status = safe_apic_wait_icr_idle();

        mdelay(10);

        Dprintk("Deasserting INIT.\n");

        /* Target chip */
        apic_write_around(APIC_ICR2, SET_APIC_DEST_FIELD(phys_apicid));

        /* Send IPI */
        apic_write_around(APIC_ICR, APIC_INT_LEVELTRIG | APIC_DM_INIT);

        Dprintk("Waiting for send to finish...\n");
        send_status = safe_apic_wait_icr_idle();

        mb();
        atomic_set(&init_deasserted, 1);

        /*
         * Should we send STARTUP IPIs ?
         *
         * Determine this based on the APIC version.
         * If we don't have an integrated APIC, don't send the STARTUP IPIs.
         */
        if (APIC_INTEGRATED(apic_version[phys_apicid]))
                num_starts = 2;
        else
                num_starts = 0;

        /*
         * Paravirt / VMI wants a startup IPI hook here to set up the
         * target processor state.
         */
        startup_ipi_hook(phys_apicid, (unsigned long) start_secondary,
#ifdef CONFIG_X86_64
                         (unsigned long)init_rsp);
#else
                         (unsigned long)stack_start.sp);
#endif

        /*
         * Run STARTUP IPI loop.
         */
        Dprintk("#startup loops: %d.\n", num_starts);

        maxlvt = lapic_get_maxlvt();

        for (j = 1; j <= num_starts; j++) {
                Dprintk("Sending STARTUP #%d.\n", j);
                apic_read_around(APIC_SPIV);
                apic_write(APIC_ESR, 0);
                apic_read(APIC_ESR);
                Dprintk("After apic_write.\n");

                /*
                 * STARTUP IPI
                 */

                /* Target chip */
                apic_write_around(APIC_ICR2, SET_APIC_DEST_FIELD(phys_apicid));

                /* Boot on the stack */
                /* Kick the second */
                apic_write_around(APIC_ICR, APIC_DM_STARTUP
                                        | (start_eip >> 12));

                /*
                 * Give the other CPU some time to accept the IPI.
                 */
                udelay(300);

                Dprintk("Startup point 1.\n");

                Dprintk("Waiting for send to finish...\n");
                send_status = safe_apic_wait_icr_idle();

                /*
                 * Give the other CPU some time to accept the IPI.
                 */
                udelay(200);
                /*
                 * Due to the Pentium erratum 3AP.
                 */
                if (maxlvt > 3) {
                        apic_read_around(APIC_SPIV);
                        apic_write(APIC_ESR, 0);
                }
                accept_status = (apic_read(APIC_ESR) & 0xEF);
                if (send_status || accept_status)
                        break;
        }
        Dprintk("After Startup.\n");

        if (send_status)
                printk(KERN_ERR "APIC never delivered???\n");
        if (accept_status)
                printk(KERN_ERR "APIC delivery error (%lx).\n", accept_status);

        return (send_status | accept_status);
}
#endif  /* WAKE_SECONDARY_VIA_INIT */

struct create_idle {
        struct work_struct work;
        struct task_struct *idle;
        struct completion done;
        int cpu;
};

static void __cpuinit do_fork_idle(struct work_struct *work)
{
        struct create_idle *c_idle =
                container_of(work, struct create_idle, work);

        c_idle->idle = fork_idle(c_idle->cpu);
        complete(&c_idle->done);
}

static int __cpuinit do_boot_cpu(int apicid, int cpu)
/*
 * NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad
 * (ie clustered apic addressing mode), this is a LOGICAL apic ID.
 * Returns zero if CPU booted OK, else error code from wakeup_secondary_cpu.
 */
{
        unsigned long boot_error = 0;
        int timeout;
        unsigned long start_ip;
        unsigned short nmi_high = 0, nmi_low = 0;
        struct create_idle c_idle = {
                .cpu = cpu,
                .done = COMPLETION_INITIALIZER_ONSTACK(c_idle.done),
        };
        INIT_WORK(&c_idle.work, do_fork_idle);
#ifdef CONFIG_X86_64
        /* allocate memory for gdts of secondary cpus. Hotplug is considered */
        if (!cpu_gdt_descr[cpu].address &&
                !(cpu_gdt_descr[cpu].address = get_zeroed_page(GFP_KERNEL))) {
                printk(KERN_ERR "Failed to allocate GDT for CPU %d\n", cpu);
                return -1;
        }

        /* Allocate node local memory for AP pdas */
        if (cpu_pda(cpu) == &boot_cpu_pda[cpu]) {
                struct x8664_pda *newpda, *pda;
                int node = cpu_to_node(cpu);
                pda = cpu_pda(cpu);
                newpda = kmalloc_node(sizeof(struct x8664_pda), GFP_ATOMIC,
                                      node);
                if (newpda) {
                        memcpy(newpda, pda, sizeof(struct x8664_pda));
                        cpu_pda(cpu) = newpda;
                } else
                        printk(KERN_ERR
                "Could not allocate node local PDA for CPU %d on node %d\n",
                                cpu, node);
        }
#endif

        alternatives_smp_switch(1);

        c_idle.idle = get_idle_for_cpu(cpu);

        /*
         * We can't use kernel_thread since we must avoid to
         * reschedule the child.
         */
        if (c_idle.idle) {
                c_idle.idle->thread.sp = (unsigned long) (((struct pt_regs *)
                        (THREAD_SIZE +  task_stack_page(c_idle.idle))) - 1);
                init_idle(c_idle.idle, cpu);
                goto do_rest;
        }

        if (!keventd_up() || current_is_keventd())
                c_idle.work.func(&c_idle.work);
        else {
                schedule_work(&c_idle.work);
                wait_for_completion(&c_idle.done);
        }

        if (IS_ERR(c_idle.idle)) {
                printk("failed fork for CPU %d\n", cpu);
                return PTR_ERR(c_idle.idle);
        }

        set_idle_for_cpu(cpu, c_idle.idle);
do_rest:
#ifdef CONFIG_X86_32
        per_cpu(current_task, cpu) = c_idle.idle;
        init_gdt(cpu);
        early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
        c_idle.idle->thread.ip = (unsigned long) start_secondary;
        /* Stack for startup_32 can be just as for start_secondary onwards */
        stack_start.sp = (void *) c_idle.idle->thread.sp;
        irq_ctx_init(cpu);
#else
        cpu_pda(cpu)->pcurrent = c_idle.idle;
        init_rsp = c_idle.idle->thread.sp;
        load_sp0(&per_cpu(init_tss, cpu), &c_idle.idle->thread);
        initial_code = (unsigned long)start_secondary;
        clear_tsk_thread_flag(c_idle.idle, TIF_FORK);
#endif

        /* start_ip had better be page-aligned! */
        start_ip = setup_trampoline();

        /* So we see what's up   */
        printk(KERN_INFO "Booting processor %d/%d ip %lx\n",
                          cpu, apicid, start_ip);

        /*
         * This grunge runs the startup process for
         * the targeted processor.
         */

        atomic_set(&init_deasserted, 0);

        if (get_uv_system_type() != UV_NON_UNIQUE_APIC) {

                Dprintk("Setting warm reset code and vector.\n");

                store_NMI_vector(&nmi_high, &nmi_low);

                smpboot_setup_warm_reset_vector(start_ip);
                /*
                 * Be paranoid about clearing APIC errors.
                */
                apic_write(APIC_ESR, 0);
                apic_read(APIC_ESR);
        }

        /*
         * Starting actual IPI sequence...
         */
        boot_error = wakeup_secondary_cpu(apicid, start_ip);

        if (!boot_error) {
                /*
                 * allow APs to start initializing.
                 */
                Dprintk("Before Callout %d.\n", cpu);
                cpu_set(cpu, cpu_callout_map);
                Dprintk("After Callout %d.\n", cpu);

                /*
                 * Wait 5s total for a response
                 */
                for (timeout = 0; timeout < 50000; timeout++) {
                        if (cpu_isset(cpu, cpu_callin_map))
                                break;  /* It has booted */
                        udelay(100);
                }

                if (cpu_isset(cpu, cpu_callin_map)) {
                        /* number CPUs logically, starting from 1 (BSP is 0) */
                        Dprintk("OK.\n");
                        printk(KERN_INFO "CPU%d: ", cpu);
                        print_cpu_info(&cpu_data(cpu));
                        Dprintk("CPU has booted.\n");
                } else {
                        boot_error = 1;
                        if (*((volatile unsigned char *)trampoline_base)
                                        == 0xA5)
                                /* trampoline started but...? */
                                printk(KERN_ERR "Stuck ??\n");
                        else
                                /* trampoline code not run */
                                printk(KERN_ERR "Not responding.\n");
                        if (get_uv_system_type() != UV_NON_UNIQUE_APIC)
                                inquire_remote_apic(apicid);
                }
        }

        if (boot_error) {
                /* Try to put things back the way they were before ... */
                unmap_cpu_to_logical_apicid(cpu);
#ifdef CONFIG_X86_64
                clear_node_cpumask(cpu); /* was set by numa_add_cpu */
#endif
                cpu_clear(cpu, cpu_callout_map); /* was set by do_boot_cpu() */
                cpu_clear(cpu, cpu_initialized); /* was set by cpu_init() */
                cpu_clear(cpu, cpu_present_map);
                per_cpu(x86_cpu_to_apicid, cpu) = BAD_APICID;
        }

        /* mark "stuck" area as not stuck */
        *((volatile unsigned long *)trampoline_base) = 0;

        /*
         * Cleanup possible dangling ends...
         */
        smpboot_restore_warm_reset_vector();

        return boot_error;
}

int __cpuinit native_cpu_up(unsigned int cpu)
{
        int apicid = cpu_present_to_apicid(cpu);
        unsigned long flags;
        int err;

        WARN_ON(irqs_disabled());

        Dprintk("++++++++++++++++++++=_---CPU UP  %u\n", cpu);

        if (apicid == BAD_APICID || apicid == boot_cpu_physical_apicid ||
            !physid_isset(apicid, phys_cpu_present_map)) {
                printk(KERN_ERR "%s: bad cpu %d\n", __func__, cpu);
                return -EINVAL;
        }

        /*
         * Already booted CPU?
         */
        if (cpu_isset(cpu, cpu_callin_map)) {
                Dprintk("do_boot_cpu %d Already started\n", cpu);
                return -ENOSYS;
        }

        /*
         * Save current MTRR state in case it was changed since early boot
         * (e.g. by the ACPI SMI) to initialize new CPUs with MTRRs in sync:
         */
        mtrr_save_state();

        per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;

#ifdef CONFIG_X86_32
        /* init low mem mapping */
        clone_pgd_range(swapper_pg_dir, swapper_pg_dir + KERNEL_PGD_BOUNDARY,
                min_t(unsigned long, KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY));
        flush_tlb_all();
        low_mappings = 1;

        err = do_boot_cpu(apicid, cpu);

        zap_low_mappings();
        low_mappings = 0;
#else
        err = do_boot_cpu(apicid, cpu);
#endif
        if (err) {
                Dprintk("do_boot_cpu failed %d\n", err);
                return -EIO;
        }

        /*
         * Check TSC synchronization with the AP (keep irqs disabled
         * while doing so):
         */
        local_irq_save(flags);
        check_tsc_sync_source(cpu);
        local_irq_restore(flags);

        while (!cpu_online(cpu)) {
                cpu_relax();
                touch_nmi_watchdog();
        }

        return 0;
}

/*
 * Fall back to non SMP mode after errors.
 *
 * RED-PEN audit/test this more. I bet there is more state messed up here.
 */
static __init void disable_smp(void)
{
        cpu_present_map = cpumask_of_cpu(0);
        cpu_possible_map = cpumask_of_cpu(0);
#ifdef CONFIG_X86_32
        smpboot_clear_io_apic_irqs();
#endif
        if (smp_found_config)
                phys_cpu_present_map =
                                physid_mask_of_physid(boot_cpu_physical_apicid);
        else
                phys_cpu_present_map = physid_mask_of_physid(0);
        map_cpu_to_logical_apicid();
        cpu_set(0, per_cpu(cpu_sibling_map, 0));
        cpu_set(0, per_cpu(cpu_core_map, 0));
}

/*
 * Various sanity checks.
 */
static int __init smp_sanity_check(unsigned max_cpus)
{
        preempt_disable();
        if (!physid_isset(hard_smp_processor_id(), phys_cpu_present_map)) {
                printk(KERN_WARNING "weird, boot CPU (#%d) not listed"
                                    "by the BIOS.\n", hard_smp_processor_id());
                physid_set(hard_smp_processor_id(), phys_cpu_present_map);
        }

        /*
         * If we couldn't find an SMP configuration at boot time,
         * get out of here now!
         */
        if (!smp_found_config && !acpi_lapic) {
                preempt_enable();
                printk(KERN_NOTICE "SMP motherboard not detected.\n");
                disable_smp();
                if (APIC_init_uniprocessor())
                        printk(KERN_NOTICE "Local APIC not detected."
                                           " Using dummy APIC emulation.\n");
                return -1;
        }

        /*
         * Should not be necessary because the MP table should list the boot
         * CPU too, but we do it for the sake of robustness anyway.
         */
        if (!check_phys_apicid_present(boot_cpu_physical_apicid)) {
                printk(KERN_NOTICE
                        "weird, boot CPU (#%d) not listed by the BIOS.\n",
                        boot_cpu_physical_apicid);
                physid_set(hard_smp_processor_id(), phys_cpu_present_map);
        }
        preempt_enable();

        /*
         * If we couldn't find a local APIC, then get out of here now!
         */
        if (APIC_INTEGRATED(apic_version[boot_cpu_physical_apicid]) &&
            !cpu_has_apic) {
                printk(KERN_ERR "BIOS bug, local APIC #%d not detected!...\n",
                        boot_cpu_physical_apicid);
                printk(KERN_ERR "... forcing use of dummy APIC emulation."
                                "(tell your hw vendor)\n");
                smpboot_clear_io_apic();
                return -1;
        }

        verify_local_APIC();

        /*
         * If SMP should be disabled, then really disable it!
         */
        if (!max_cpus) {
                printk(KERN_INFO "SMP mode deactivated,"
                                 "forcing use of dummy APIC emulation.\n");
                smpboot_clear_io_apic();
#ifdef CONFIG_X86_32
                connect_bsp_APIC();
#endif
                setup_local_APIC();
                end_local_APIC_setup();
                return -1;
        }

        return 0;
}

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

        for_each_possible_cpu(i) {
                c = &cpu_data(i);
                /* mark all to hotplug */
                c->cpu_index = NR_CPUS;
        }
}

/*
 * Prepare for SMP bootup.  The MP table or ACPI has been read
 * earlier.  Just do some sanity checking here and enable APIC mode.
 */
void __init native_smp_prepare_cpus(unsigned int max_cpus)
{
        preempt_disable();
        nmi_watchdog_default();
        smp_cpu_index_default();
        current_cpu_data = boot_cpu_data;
        cpu_callin_map = cpumask_of_cpu(0);
        mb();
        /*
         * Setup boot CPU information
         */
        smp_store_cpu_info(0); /* Final full version of the data */
        boot_cpu_logical_apicid = logical_smp_processor_id();
        current_thread_info()->cpu = 0;  /* needed? */
        set_cpu_sibling_map(0);

        if (smp_sanity_check(max_cpus) < 0) {
                printk(KERN_INFO "SMP disabled\n");
                disable_smp();
                goto out;
        }

        preempt_disable();
        if (GET_APIC_ID(read_apic_id()) != boot_cpu_physical_apicid) {
                panic("Boot APIC ID in local APIC unexpected (%d vs %d)",
                     GET_APIC_ID(read_apic_id()), boot_cpu_physical_apicid);
                /* Or can we switch back to PIC here? */
        }
        preempt_enable();

#ifdef CONFIG_X86_32
        connect_bsp_APIC();
#endif
        /*
         * Switch from PIC to APIC mode.
         */
        setup_local_APIC();

#ifdef CONFIG_X86_64
        /*
         * Enable IO APIC before setting up error vector
         */
        if (!skip_ioapic_setup && nr_ioapics)
                enable_IO_APIC();
#endif
        end_local_APIC_setup();

        map_cpu_to_logical_apicid();

        setup_portio_remap();

        smpboot_setup_io_apic();
        /*
         * Set up local APIC timer on boot CPU.
         */

        printk(KERN_INFO "CPU%d: ", 0);
        print_cpu_info(&cpu_data(0));
        setup_boot_clock();
out:
        preempt_enable();
}
/*
 * Early setup to make printk work.
 */
void __init native_smp_prepare_boot_cpu(void)
{
        int me = smp_processor_id();
#ifdef CONFIG_X86_32
        init_gdt(me);
        switch_to_new_gdt();
#endif
        /* already set me in cpu_online_map in boot_cpu_init() */
        cpu_set(me, cpu_callout_map);
        per_cpu(cpu_state, me) = CPU_ONLINE;
}

void __init native_smp_cpus_done(unsigned int max_cpus)
{
        Dprintk("Boot done.\n");

        impress_friends();
        smp_checks();
#ifdef CONFIG_X86_IO_APIC
        setup_ioapic_dest();
#endif
        check_nmi_watchdog();
}

#ifdef CONFIG_HOTPLUG_CPU

#  ifdef CONFIG_X86_32
void cpu_exit_clear(void)
{
        int cpu = raw_smp_processor_id();

        idle_task_exit();

        cpu_uninit();
        irq_ctx_exit(cpu);

        cpu_clear(cpu, cpu_callout_map);
        cpu_clear(cpu, cpu_callin_map);

        unmap_cpu_to_logical_apicid(cpu);
}
#  endif /* CONFIG_X86_32 */

static void remove_siblinginfo(int cpu)
{
        int sibling;
        struct cpuinfo_x86 *c = &cpu_data(cpu);

        for_each_cpu_mask(sibling, per_cpu(cpu_core_map, cpu)) {
                cpu_clear(cpu, per_cpu(cpu_core_map, sibling));
                /*/
                 * last thread sibling in this cpu core going down
                 */
                if (cpus_weight(per_cpu(cpu_sibling_map, cpu)) == 1)
                        cpu_data(sibling).booted_cores--;
        }

        for_each_cpu_mask(sibling, per_cpu(cpu_sibling_map, cpu))
                cpu_clear(cpu, per_cpu(cpu_sibling_map, sibling));
        cpus_clear(per_cpu(cpu_sibling_map, cpu));
        cpus_clear(per_cpu(cpu_core_map, cpu));
        c->phys_proc_id = 0;
        c->cpu_core_id = 0;
        cpu_clear(cpu, cpu_sibling_setup_map);
}

static int additional_cpus __initdata = -1;

static __init int setup_additional_cpus(char *s)
{
        return s && get_option(&s, &additional_cpus) ? 0 : -EINVAL;
}
early_param("additional_cpus", setup_additional_cpus);

/*
 * cpu_possible_map should be static, it cannot change as cpu's
 * are onlined, or offlined. The reason is per-cpu data-structures
 * are allocated by some modules at init time, and dont expect to
 * do this dynamically on cpu arrival/departure.
 * cpu_present_map on the other hand can change dynamically.
 * In case when cpu_hotplug is not compiled, then we resort to current
 * behaviour, which is cpu_possible == cpu_present.
 * - Ashok Raj
 *
 * Three ways to find out the number of additional hotplug CPUs:
 * - If the BIOS specified disabled CPUs in ACPI/mptables use that.
 * - The user can overwrite it with additional_cpus=NUM
 * - Otherwise don't reserve additional CPUs.
 * We do this because additional CPUs waste a lot of memory.
 * -AK
 */
__init void prefill_possible_map(void)
{
        int i;
        int possible;

        if (additional_cpus == -1) {
                if (disabled_cpus > 0)
                        additional_cpus = disabled_cpus;
                else
                        additional_cpus = 0;
        }
        possible = num_processors + additional_cpus;
        if (possible > NR_CPUS)
                possible = NR_CPUS;

        printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n",
                possible, max_t(int, possible - num_processors, 0));

        for (i = 0; i < possible; i++)
                cpu_set(i, cpu_possible_map);
}

static void __ref remove_cpu_from_maps(int cpu)
{
        cpu_clear(cpu, cpu_online_map);
#ifdef CONFIG_X86_64
        cpu_clear(cpu, cpu_callout_map);
        cpu_clear(cpu, cpu_callin_map);
        /* was set by cpu_init() */
        clear_bit(cpu, (unsigned long *)&cpu_initialized);
        clear_node_cpumask(cpu);
#endif
}

int __cpu_disable(void)
{
        int cpu = smp_processor_id();

        /*
         * Perhaps use cpufreq to drop frequency, but that could go
         * into generic code.
         *
         * We won't take down the boot processor on i386 due to some
         * interrupts only being able to be serviced by the BSP.
         * Especially so if we're not using an IOAPIC   -zwane
         */
        if (cpu == 0)
                return -EBUSY;

        if (nmi_watchdog == NMI_LOCAL_APIC)
                stop_apic_nmi_watchdog(NULL);
        clear_local_APIC();

        /*
         * HACK:
         * Allow any queued timer interrupts to get serviced
         * This is only a temporary solution until we cleanup
         * fixup_irqs as we do for IA64.
         */
        local_irq_enable();
        mdelay(1);

        local_irq_disable();
        remove_siblinginfo(cpu);

        /* It's now safe to remove this processor from the online map */
        remove_cpu_from_maps(cpu);
        fixup_irqs(cpu_online_map);
        return 0;
}

void __cpu_die(unsigned int cpu)
{
        /* We don't do anything here: idle task is faking death itself. */
        unsigned int i;

        for (i = 0; i < 10; i++) {
                /* They ack this in play_dead by setting CPU_DEAD */
                if (per_cpu(cpu_state, cpu) == CPU_DEAD) {
                        printk(KERN_INFO "CPU %d is now offline\n", cpu);
                        if (1 == num_online_cpus())
                                alternatives_smp_switch(0);
                        return;
                }
                msleep(100);
        }
        printk(KERN_ERR "CPU %u didn't die...\n", cpu);
}
#else /* ... !CONFIG_HOTPLUG_CPU */
int __cpu_disable(void)
{
        return -ENOSYS;
}

void __cpu_die(unsigned int cpu)
{
        /* We said "no" in __cpu_disable */
        BUG();
}
#endif

/*
 * If the BIOS enumerates physical processors before logical,
 * maxcpus=N at enumeration-time can be used to disable HT.
 */
static int __init parse_maxcpus(char *arg)
{
        extern unsigned int maxcpus;

        maxcpus = simple_strtoul(arg, NULL, 0);
        return 0;
}
early_param("maxcpus", parse_maxcpus);