[PATCH] i386, apic: clean up the APIC code

[linux-2.6/linux-2.6-openrd.git] / arch / i386 / 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>
 *
 *      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
 *              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. */


/* SMP boot always wants to use real time delay to allow sufficient time for
 * the APs to come online */
#define USE_REAL_TIME_DELAY

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>

#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/kernel_stat.h>
#include <linux/smp_lock.h>
#include <linux/bootmem.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/percpu.h>

#include <linux/delay.h>
#include <linux/mc146818rtc.h>
#include <asm/tlbflush.h>
#include <asm/desc.h>
#include <asm/arch_hooks.h>
#include <asm/nmi.h>
#include <asm/pda.h>
#include <asm/genapic.h>

#include <mach_apic.h>
#include <mach_wakecpu.h>
#include <smpboot_hooks.h>
#include <asm/vmi.h>

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

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

/* Last level cache ID of each logical CPU */
int cpu_llc_id[NR_CPUS] __cpuinitdata = {[0 ... NR_CPUS-1] = BAD_APICID};

/* representing HT siblings of each logical CPU */
cpumask_t cpu_sibling_map[NR_CPUS] __read_mostly;
EXPORT_SYMBOL(cpu_sibling_map);

/* representing HT and core siblings of each logical CPU */
cpumask_t cpu_core_map[NR_CPUS] __read_mostly;
EXPORT_SYMBOL(cpu_core_map);

/* 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;
EXPORT_SYMBOL(cpu_callout_map);
cpumask_t cpu_possible_map;
EXPORT_SYMBOL(cpu_possible_map);
static cpumask_t smp_commenced_mask;

/* Per CPU bogomips and other parameters */
struct cpuinfo_x86 cpu_data[NR_CPUS] __cacheline_aligned;
EXPORT_SYMBOL(cpu_data);

u8 x86_cpu_to_apicid[NR_CPUS] __read_mostly =
                        { [0 ... NR_CPUS-1] = 0xff };
EXPORT_SYMBOL(x86_cpu_to_apicid);

u8 apicid_2_node[MAX_APICID];

/*
 * Trampoline 80x86 program as an array.
 */

extern unsigned char trampoline_data [];
extern unsigned char trampoline_end  [];
static unsigned char *trampoline_base;
static int trampoline_exec;

static void map_cpu_to_logical_apicid(void);

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

/*
 * Currently trivial. Write the real->protected mode
 * bootstrap into the page concerned. The caller
 * has made sure it's suitably aligned.
 */

static unsigned long __devinit setup_trampoline(void)
{
        memcpy(trampoline_base, trampoline_data, trampoline_end - trampoline_data);
        return virt_to_phys(trampoline_base);
}

/*
 * We are called very early to get the low memory for the
 * SMP bootup trampoline page.
 */
void __init smp_alloc_memory(void)
{
        trampoline_base = (void *) 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();
        /*
         * Make the SMP trampoline executable:
         */
        trampoline_exec = set_kernel_exec((unsigned long)trampoline_base, 1);
}

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

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

        *c = boot_cpu_data;
        if (id!=0)
                identify_cpu(c);
        /*
         * 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, it's not a certified SMP capable AMD system. */
                add_taint(TAINT_UNSAFE_SMP);
        }

valid_k7:
        ;
}

extern void calibrate_delay(void);

static atomic_t init_deasserted;

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(apic_read(APIC_ID));
        cpuid = smp_processor_id();
        if (cpu_isset(cpuid, cpu_callin_map)) {
                printk("huh, phys CPU#%d, CPU#%d already present??\n",
                                        phys_id, cpuid);
                BUG();
        }
        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;
                rep_nop();
        }

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

        /*
         * 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();
        map_cpu_to_logical_apicid();

        /*
         * Get our bogomips.
         */
        calibrate_delay();
        Dprintk("Stack at about %p\n",&cpuid);

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

        disable_APIC_timer();

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

static int cpucount;

/* 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 cpu_core_map[cpu];
        else
                return c->llc_shared_map;
}

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

static inline void
set_cpu_sibling_map(int cpu)
{
        int i;
        struct cpuinfo_x86 *c = cpu_data;

        cpu_set(cpu, cpu_sibling_setup_map);

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

        cpu_set(cpu, c[cpu].llc_shared_map);

        if (current_cpu_data.x86_max_cores == 1) {
                cpu_core_map[cpu] = cpu_sibling_map[cpu];
                c[cpu].booted_cores = 1;
                return;
        }

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

/*
 * Activate a secondary processor.
 */
static void __cpuinit start_secondary(void *unused)
{
        /*
         * Don't put *anything* before secondary_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
        secondary_cpu_init();
        preempt_disable();
        smp_callin();
        while (!cpu_isset(smp_processor_id(), smp_commenced_mask))
                rep_nop();
        /*
         * Check TSC synchronization with the BP:
         */
        check_tsc_sync_target();

        setup_secondary_clock();
        if (nmi_watchdog == NMI_IO_APIC) {
                disable_8259A_irq(0);
                enable_NMI_through_LVT0(NULL);
                enable_8259A_irq(0);
        }
        enable_APIC_timer();
        /*
         * low-memory mappings have been cleared, flush them from
         * the local TLBs too.
         */
        local_flush_tlb();

        /* 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 receipients, 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();
        cpu_set(smp_processor_id(), cpu_online_map);
        unlock_ipi_call_lock();
        per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;

        /* We can take interrupts now: we're officially "up". */
        local_irq_enable();

        wmb();
        cpu_idle();
}

/*
 * 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)
{
        /*
         * switch to the per CPU GDT we already set up
         * in do_boot_cpu()
         */
        cpu_set_gdt(current_thread_info()->cpu);

        /*
         * We don't actually need to load the full TSS,
         * basically just the stack pointer and the eip.
         */

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

/* Static state in head.S used to set up a CPU */
extern struct {
        void * esp;
        unsigned short ss;
} stack_start;
extern struct i386_pda *start_pda;

#ifdef CONFIG_NUMA

/* which logical CPUs are on which nodes */
cpumask_t node_2_cpu_mask[MAX_NUMNODES] __read_mostly =
                                { [0 ... MAX_NUMNODES-1] = CPU_MASK_NONE };
EXPORT_SYMBOL(node_2_cpu_mask);
/* which node each logical CPU is on */
int cpu_2_node[NR_CPUS] __read_mostly = { [0 ... NR_CPUS-1] = 0 };
EXPORT_SYMBOL(cpu_2_node);

/* set up a mapping between cpu and node. */
static inline void map_cpu_to_node(int cpu, int node)
{
        printk("Mapping cpu %d to node %d\n", cpu, node);
        cpu_set(cpu, node_2_cpu_mask[node]);
        cpu_2_node[cpu] = node;
}

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

        printk("Unmapping cpu %d from all nodes\n", cpu);
        for (node = 0; node < MAX_NUMNODES; node ++)
                cpu_clear(cpu, node_2_cpu_mask[node]);
        cpu_2_node[cpu] = 0;
}
#else /* !CONFIG_NUMA */

#define map_cpu_to_node(cpu, node)      ({})
#define unmap_cpu_to_node(cpu)  ({})

#endif /* CONFIG_NUMA */

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);
}

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

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

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

                /*
                 * Wait for idle.
                 */
                apic_wait_icr_idle();

                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("%08x\n", status);
                        break;
                default:
                        printk("failed\n");
                }
        }
}
#endif

#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 = 0, accept_status = 0;
        int timeout, 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");
        timeout = 0;
        do {
                Dprintk("+");
                udelay(100);
                send_status = apic_read(APIC_ICR) & APIC_ICR_BUSY;
        } while (send_status && (timeout++ < 1000));

        /*
         * 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("APIC never delivered???\n");
        if (accept_status)
                printk("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 = 0, accept_status = 0;
        int maxlvt, timeout, num_starts, j;

        /*
         * 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");
        timeout = 0;
        do {
                Dprintk("+");
                udelay(100);
                send_status = apic_read(APIC_ICR) & APIC_ICR_BUSY;
        } while (send_status && (timeout++ < 1000));

        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");
        timeout = 0;
        do {
                Dprintk("+");
                udelay(100);
                send_status = apic_read(APIC_ICR) & APIC_ICR_BUSY;
        } while (send_status && (timeout++ < 1000));

        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,
                         (unsigned long) stack_start.esp);

        /*
         * 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");
                timeout = 0;
                do {
                        Dprintk("+");
                        udelay(100);
                        send_status = apic_read(APIC_ICR) & APIC_ICR_BUSY;
                } while (send_status && (timeout++ < 1000));

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

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

extern cpumask_t cpu_initialized;
static inline int alloc_cpu_id(void)
{
        cpumask_t       tmp_map;
        int cpu;
        cpus_complement(tmp_map, cpu_present_map);
        cpu = first_cpu(tmp_map);
        if (cpu >= NR_CPUS)
                return -ENODEV;
        return cpu;
}

#ifdef CONFIG_HOTPLUG_CPU
static struct task_struct * __devinitdata cpu_idle_tasks[NR_CPUS];
static inline struct task_struct * alloc_idle_task(int cpu)
{
        struct task_struct *idle;

        if ((idle = cpu_idle_tasks[cpu]) != NULL) {
                /* initialize thread_struct.  we really want to avoid destroy
                 * idle tread
                 */
                idle->thread.esp = (unsigned long)task_pt_regs(idle);
                init_idle(idle, cpu);
                return idle;
        }
        idle = fork_idle(cpu);

        if (!IS_ERR(idle))
                cpu_idle_tasks[cpu] = idle;
        return idle;
}
#else
#define alloc_idle_task(cpu) fork_idle(cpu)
#endif

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.
 */
{
        struct task_struct *idle;
        unsigned long boot_error;
        int timeout;
        unsigned long start_eip;
        unsigned short nmi_high = 0, nmi_low = 0;

        /*
         * We can't use kernel_thread since we must avoid to
         * reschedule the child.
         */
        idle = alloc_idle_task(cpu);
        if (IS_ERR(idle))
                panic("failed fork for CPU %d", cpu);

        /* Pre-allocate and initialize the CPU's GDT and PDA so it
           doesn't have to do any memory allocation during the
           delicate CPU-bringup phase. */
        if (!init_gdt(cpu, idle)) {
                printk(KERN_INFO "Couldn't allocate GDT/PDA for CPU %d\n", cpu);
                return -1;      /* ? */
        }

        idle->thread.eip = (unsigned long) start_secondary;
        /* start_eip had better be page-aligned! */
        start_eip = setup_trampoline();

        ++cpucount;
        alternatives_smp_switch(1);

        /* So we see what's up   */
        printk("Booting processor %d/%d eip %lx\n", cpu, apicid, start_eip);
        /* Stack for startup_32 can be just as for start_secondary onwards */
        stack_start.esp = (void *) idle->thread.esp;

        irq_ctx_init(cpu);

        x86_cpu_to_apicid[cpu] = apicid;
        /*
         * This grunge runs the startup process for
         * the targeted processor.
         */

        atomic_set(&init_deasserted, 0);

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

        store_NMI_vector(&nmi_high, &nmi_low);

        smpboot_setup_warm_reset_vector(start_eip);

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

        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("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("Stuck ??\n");
                        else
                                /* trampoline code not run */
                                printk("Not responding.\n");
                        inquire_remote_apic(apicid);
                }
        }

        if (boot_error) {
                /* Try to put things back the way they were before ... */
                unmap_cpu_to_logical_apicid(cpu);
                cpu_clear(cpu, cpu_callout_map); /* was set here (do_boot_cpu()) */
                cpu_clear(cpu, cpu_initialized); /* was set by cpu_init() */
                cpucount--;
        } else {
                x86_cpu_to_apicid[cpu] = apicid;
                cpu_set(cpu, cpu_present_map);
        }

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

        return boot_error;
}

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

        idle_task_exit();

        cpucount --;
        cpu_uninit();
        irq_ctx_exit(cpu);

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

        cpu_clear(cpu, smp_commenced_mask);
        unmap_cpu_to_logical_apicid(cpu);
}

struct warm_boot_cpu_info {
        struct completion *complete;
        struct work_struct task;
        int apicid;
        int cpu;
};

static void __cpuinit do_warm_boot_cpu(struct work_struct *work)
{
        struct warm_boot_cpu_info *info =
                container_of(work, struct warm_boot_cpu_info, task);
        do_boot_cpu(info->apicid, info->cpu);
        complete(info->complete);
}

static int __cpuinit __smp_prepare_cpu(int cpu)
{
        DECLARE_COMPLETION_ONSTACK(done);
        struct warm_boot_cpu_info info;
        int     apicid, ret;
        struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);

        apicid = x86_cpu_to_apicid[cpu];
        if (apicid == BAD_APICID) {
                ret = -ENODEV;
                goto exit;
        }

        /*
         * the CPU isn't initialized at boot time, allocate gdt table here.
         * cpu_init will initialize it
         */
        if (!cpu_gdt_descr->address) {
                cpu_gdt_descr->address = get_zeroed_page(GFP_KERNEL);
                if (!cpu_gdt_descr->address)
                        printk(KERN_CRIT "CPU%d failed to allocate GDT\n", cpu);
                        ret = -ENOMEM;
                        goto exit;
        }

        info.complete = &done;
        info.apicid = apicid;
        info.cpu = cpu;
        INIT_WORK(&info.task, do_warm_boot_cpu);

        /* init low mem mapping */
        clone_pgd_range(swapper_pg_dir, swapper_pg_dir + USER_PGD_PTRS,
                        min_t(unsigned long, KERNEL_PGD_PTRS, USER_PGD_PTRS));
        flush_tlb_all();
        schedule_work(&info.task);
        wait_for_completion(&done);

        zap_low_mappings();
        ret = 0;
exit:
        return ret;
}
#endif

static void smp_tune_scheduling(void)
{
        unsigned long cachesize;       /* kB   */

        if (cpu_khz) {
                cachesize = boot_cpu_data.x86_cache_size;

                if (cachesize > 0)
                        max_cache_size = cachesize * 1024;
        }
}

/*
 * Cycle through the processors sending APIC IPIs to boot each.
 */

static int boot_cpu_logical_apicid;
/* Where the IO area was mapped on multiquad, always 0 otherwise */
void *xquad_portio;
#ifdef CONFIG_X86_NUMAQ
EXPORT_SYMBOL(xquad_portio);
#endif

static void __init smp_boot_cpus(unsigned int max_cpus)
{
        int apicid, cpu, bit, kicked;
        unsigned long bogosum = 0;

        /*
         * Setup boot CPU information
         */
        smp_store_cpu_info(0); /* Final full version of the data */
        printk("CPU%d: ", 0);
        print_cpu_info(&cpu_data[0]);

        boot_cpu_physical_apicid = GET_APIC_ID(apic_read(APIC_ID));
        boot_cpu_logical_apicid = logical_smp_processor_id();
        x86_cpu_to_apicid[0] = boot_cpu_physical_apicid;

        current_thread_info()->cpu = 0;
        smp_tune_scheduling();

        set_cpu_sibling_map(0);

        /*
         * If we couldn't find an SMP configuration at boot time,
         * get out of here now!
         */
        if (!smp_found_config && !acpi_lapic) {
                printk(KERN_NOTICE "SMP motherboard not detected.\n");
                smpboot_clear_io_apic_irqs();
                phys_cpu_present_map = physid_mask_of_physid(0);
                if (APIC_init_uniprocessor())
                        printk(KERN_NOTICE "Local APIC not detected."
                                           " Using dummy APIC emulation.\n");
                map_cpu_to_logical_apicid();
                cpu_set(0, cpu_sibling_map[0]);
                cpu_set(0, cpu_core_map[0]);
                return;
        }

        /*
         * Should not be necessary because the MP table should list the boot
         * CPU too, but we do it for the sake of robustness anyway.
         * Makes no sense to do this check in clustered apic mode, so skip it
         */
        if (!check_phys_apicid_present(boot_cpu_physical_apicid)) {
                printk("weird, boot CPU (#%d) not listed by the BIOS.\n",
                                boot_cpu_physical_apicid);
                physid_set(hard_smp_processor_id(), phys_cpu_present_map);
        }

        /*
         * 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_irqs();
                phys_cpu_present_map = physid_mask_of_physid(0);
                cpu_set(0, cpu_sibling_map[0]);
                cpu_set(0, cpu_core_map[0]);
                return;
        }

        verify_local_APIC();

        /*
         * If SMP should be disabled, then really disable it!
         */
        if (!max_cpus) {
                smp_found_config = 0;
                printk(KERN_INFO "SMP mode deactivated, forcing use of dummy APIC emulation.\n");
                smpboot_clear_io_apic_irqs();
                phys_cpu_present_map = physid_mask_of_physid(0);
                cpu_set(0, cpu_sibling_map[0]);
                cpu_set(0, cpu_core_map[0]);
                return;
        }

        connect_bsp_APIC();
        setup_local_APIC();
        map_cpu_to_logical_apicid();


        setup_portio_remap();

        /*
         * Scan the CPU present map and fire up the other CPUs via do_boot_cpu
         *
         * In clustered apic mode, phys_cpu_present_map is a constructed thus:
         * bits 0-3 are quad0, 4-7 are quad1, etc. A perverse twist on the 
         * clustered apic ID.
         */
        Dprintk("CPU present map: %lx\n", physids_coerce(phys_cpu_present_map));

        kicked = 1;
        for (bit = 0; kicked < NR_CPUS && bit < MAX_APICS; bit++) {
                apicid = cpu_present_to_apicid(bit);
                /*
                 * Don't even attempt to start the boot CPU!
                 */
                if ((apicid == boot_cpu_apicid) || (apicid == BAD_APICID))
                        continue;

                if (!check_apicid_present(bit))
                        continue;
                if (max_cpus <= cpucount+1)
                        continue;

                if (((cpu = alloc_cpu_id()) <= 0) || do_boot_cpu(apicid, cpu))
                        printk("CPU #%d not responding - cannot use it.\n",
                                                                apicid);
                else
                        ++kicked;
        }

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

        /*
         * Allow the user to impress friends.
         */
        Dprintk("Before bogomips.\n");
        for (cpu = 0; cpu < NR_CPUS; 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",
                cpucount+1,
                bogosum/(500000/HZ),
                (bogosum/(5000/HZ))%100);
        
        Dprintk("Before bogocount - setting activated=1.\n");

        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 (cpucount)
                        printk (KERN_INFO "WARNING: This combination of AMD processors is not suitable for SMP.\n");
                else
                        tainted &= ~TAINT_UNSAFE_SMP;
        }

        Dprintk("Boot done.\n");

        /*
         * construct cpu_sibling_map[], so that we can tell sibling CPUs
         * efficiently.
         */
        for (cpu = 0; cpu < NR_CPUS; cpu++) {
                cpus_clear(cpu_sibling_map[cpu]);
                cpus_clear(cpu_core_map[cpu]);
        }

        cpu_set(0, cpu_sibling_map[0]);
        cpu_set(0, cpu_core_map[0]);

        smpboot_setup_io_apic();

        setup_boot_clock();
}

/* These are wrappers to interface to the new boot process.  Someone
   who understands all this stuff should rewrite it properly. --RR 15/Jul/02 */
void __init smp_prepare_cpus(unsigned int max_cpus)
{
        smp_commenced_mask = cpumask_of_cpu(0);
        cpu_callin_map = cpumask_of_cpu(0);
        mb();
        smp_boot_cpus(max_cpus);
}

void __devinit smp_prepare_boot_cpu(void)
{
        cpu_set(smp_processor_id(), cpu_online_map);
        cpu_set(smp_processor_id(), cpu_callout_map);
        cpu_set(smp_processor_id(), cpu_present_map);
        cpu_set(smp_processor_id(), cpu_possible_map);
        per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
}

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

        for_each_cpu_mask(sibling, cpu_core_map[cpu]) {
                cpu_clear(cpu, cpu_core_map[sibling]);
                /*
                 * last thread sibling in this cpu core going down
                 */
                if (cpus_weight(cpu_sibling_map[cpu]) == 1)
                        c[sibling].booted_cores--;
        }
                        
        for_each_cpu_mask(sibling, cpu_sibling_map[cpu])
                cpu_clear(cpu, cpu_sibling_map[sibling]);
        cpus_clear(cpu_sibling_map[cpu]);
        cpus_clear(cpu_core_map[cpu]);
        c[cpu].phys_proc_id = 0;
        c[cpu].cpu_core_id = 0;
        cpu_clear(cpu, cpu_sibling_setup_map);
}

int __cpu_disable(void)
{
        cpumask_t map = cpu_online_map;
        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();
        /* Allow any queued timer interrupts to get serviced */
        local_irq_enable();
        mdelay(1);
        local_irq_disable();

        remove_siblinginfo(cpu);

        cpu_clear(cpu, map);
        fixup_irqs(map);
        /* It's now safe to remove this processor from the online map */
        cpu_clear(cpu, 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 ("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 /* CONFIG_HOTPLUG_CPU */

int __cpuinit __cpu_up(unsigned int cpu)
{
#ifdef CONFIG_HOTPLUG_CPU
        int ret=0;

        /*
         * We do warm boot only on cpus that had booted earlier
         * Otherwise cold boot is all handled from smp_boot_cpus().
         * cpu_callin_map is set during AP kickstart process. Its reset
         * when a cpu is taken offline from cpu_exit_clear().
         */
        if (!cpu_isset(cpu, cpu_callin_map))
                ret = __smp_prepare_cpu(cpu);

        if (ret)
                return -EIO;
#endif

        /* In case one didn't come up */
        if (!cpu_isset(cpu, cpu_callin_map)) {
                printk(KERN_DEBUG "skipping cpu%d, didn't come online\n", cpu);
                local_irq_enable();
                return -EIO;
        }

        local_irq_enable();

        per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
        /* Unleash the CPU! */
        cpu_set(cpu, smp_commenced_mask);

        /*
         * Check TSC synchronization with the AP:
         */
        check_tsc_sync_source(cpu);

        while (!cpu_isset(cpu, cpu_online_map))
                cpu_relax();

#ifdef CONFIG_X86_GENERICARCH
        if (num_online_cpus() > 8 && genapic == &apic_default)
                panic("Default flat APIC routing can't be used with > 8 cpus\n");
#endif

        return 0;
}

void __init smp_cpus_done(unsigned int max_cpus)
{
#ifdef CONFIG_X86_IO_APIC
        setup_ioapic_dest();
#endif
        zap_low_mappings();
#ifndef CONFIG_HOTPLUG_CPU
        /*
         * Disable executability of the SMP trampoline:
         */
        set_kernel_exec((unsigned long)trampoline_base, trampoline_exec);
#endif
}

void __init smp_intr_init(void)
{
        /*
         * IRQ0 must be given a fixed assignment and initialized,
         * because it's used before the IO-APIC is set up.
         */
        set_intr_gate(FIRST_DEVICE_VECTOR, interrupt[0]);

        /*
         * The reschedule interrupt is a CPU-to-CPU reschedule-helper
         * IPI, driven by wakeup.
         */
        set_intr_gate(RESCHEDULE_VECTOR, reschedule_interrupt);

        /* IPI for invalidation */
        set_intr_gate(INVALIDATE_TLB_VECTOR, invalidate_interrupt);

        /* IPI for generic function call */
        set_intr_gate(CALL_FUNCTION_VECTOR, call_function_interrupt);
}

/*
 * 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);