smpboot.c

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/*
 * SMP boot-related support
 *
 * Copyright (C) 1998-2003, 2005 Hewlett-Packard Co
 *  David Mosberger-Tang <[email protected]>
 * Copyright (C) 2001, 2004-2005 Intel Corp
 *  Rohit Seth <[email protected]>
 *  Suresh Siddha <[email protected]>
 *  Gordon Jin <[email protected]>
 *  Ashok Raj  <[email protected]>
 *
 * 01/05/16 Rohit Seth <[email protected]>   Moved SMP booting functions from smp.c to here.
 * 01/04/27 David Mosberger <[email protected]> Added ITC synching code.
 * 02/07/31 David Mosberger <[email protected]> Switch over to hotplug-CPU boot-sequence.
 *                      smp_boot_cpus()/smp_commence() is replaced by
 *                      smp_prepare_cpus()/__cpu_up()/smp_cpus_done().
 * 04/06/21 Ashok Raj       <[email protected]> Added CPU Hotplug Support
 * 04/12/26 Jin Gordon <[email protected]>
 * 04/12/26 Rohit Seth <[email protected]>
 *                      Add multi-threading and multi-core detection
 * 05/01/30 Suresh Siddha <[email protected]>
 *                      Setup cpu_sibling_map and cpu_core_map
 */

#include <linux/module.h>
#include <linux/acpi.h>
#include <linux/bootmem.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/kernel_stat.h>
#include <linux/mm.h>
#include <linux/notifier.h>
#include <linux/smp.h>
#include <linux/spinlock.h>
#include <linux/efi.h>
#include <linux/percpu.h>
#include <linux/bitops.h>

#include <linux/atomic.h>
#include <asm/cache.h>
#include <asm/current.h>
#include <asm/delay.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/machvec.h>
#include <asm/mca.h>
#include <asm/page.h>
#include <asm/paravirt.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/ptrace.h>
#include <asm/sal.h>
#include <asm/tlbflush.h>
#include <asm/unistd.h>
#include <asm/sn/arch.h>

#define SMP_DEBUG 0

#if SMP_DEBUG
#define Dprintk(x...)  printk(x)
#else
#define Dprintk(x...)
#endif

#ifdef CONFIG_HOTPLUG_CPU
#ifdef CONFIG_PERMIT_BSP_REMOVE
#define bsp_remove_ok   1
#else
#define bsp_remove_ok   0
#endif

/*
 * Global array allocated for NR_CPUS at boot time
 */
struct sal_to_os_boot sal_boot_rendez_state[NR_CPUS];

/*
 * start_ap in head.S uses this to store current booting cpu
 * info.
 */
struct sal_to_os_boot *sal_state_for_booting_cpu = &sal_boot_rendez_state[0];

#define set_brendez_area(x) (sal_state_for_booting_cpu = &sal_boot_rendez_state[(x)]);

#else
#define set_brendez_area(x)
#endif


/*
 * ITC synchronization related stuff:
 */
#define MASTER  (0)
#define SLAVE   (SMP_CACHE_BYTES/8)

#define NUM_ROUNDS  64  /* magic value */
#define NUM_ITERS   5   /* likewise */

static DEFINE_SPINLOCK(itc_sync_lock);
static volatile unsigned long go[SLAVE + 1];

#define DEBUG_ITC_SYNC  0

extern void start_ap (void);
extern unsigned long ia64_iobase;

struct task_struct *task_for_booting_cpu;

/*
 * State for each CPU
 */
DEFINE_PER_CPU(int, cpu_state);

cpumask_t cpu_core_map[NR_CPUS] __cacheline_aligned;
EXPORT_SYMBOL(cpu_core_map);
DEFINE_PER_CPU_SHARED_ALIGNED(cpumask_t, cpu_sibling_map);
EXPORT_PER_CPU_SYMBOL(cpu_sibling_map);

int smp_num_siblings = 1;

/* which logical CPU number maps to which CPU (physical APIC ID) */
volatile int ia64_cpu_to_sapicid[NR_CPUS];
EXPORT_SYMBOL(ia64_cpu_to_sapicid);

static volatile cpumask_t cpu_callin_map;

struct smp_boot_data smp_boot_data __initdata;

unsigned long ap_wakeup_vector = -1; /* External Int use to wakeup APs */

char __initdata no_int_routing;

unsigned char smp_int_redirect; /* are INT and IPI redirectable by the chipset? */

#ifdef CONFIG_FORCE_CPEI_RETARGET
#define CPEI_OVERRIDE_DEFAULT   (1)
#else
#define CPEI_OVERRIDE_DEFAULT   (0)
#endif

unsigned int force_cpei_retarget = CPEI_OVERRIDE_DEFAULT;

static int __init
cmdl_force_cpei(char *str)
{
    int value=0;

    get_option (&str, &value);
    force_cpei_retarget = value;

    return 1;
}

__setup("force_cpei=", cmdl_force_cpei);

static int __init
nointroute (char *str)
{
    no_int_routing = 1;
    printk ("no_int_routing on\n");
    return 1;
}

__setup("nointroute", nointroute);

static void fix_b0_for_bsp(void)
{
#ifdef CONFIG_HOTPLUG_CPU
    int cpuid;
    static int fix_bsp_b0 = 1;

    cpuid = smp_processor_id();

    /*
     * Cache the b0 value on the first AP that comes up
     */
    if (!(fix_bsp_b0 && cpuid))
        return;

    sal_boot_rendez_state[0].br[0] = sal_boot_rendez_state[cpuid].br[0];
    printk ("Fixed BSP b0 value from CPU %d\n", cpuid);

    fix_bsp_b0 = 0;
#endif
}

void
sync_master (void *arg)
{
    unsigned long flags, i;

    go[MASTER] = 0;

    local_irq_save(flags);
    {
        for (i = 0; i < NUM_ROUNDS*NUM_ITERS; ++i) {
            while (!go[MASTER])
                cpu_relax();
            go[MASTER] = 0;
            go[SLAVE] = ia64_get_itc();
        }
    }
    local_irq_restore(flags);
}

/*
 * Return the number of cycles by which our itc differs from the itc on the master
 * (time-keeper) CPU.  A positive number indicates our itc is ahead of the master,
 * negative that it is behind.
 */
static inline long
get_delta (long *rt, long *master)
{
    unsigned long best_t0 = 0, best_t1 = ~0UL, best_tm = 0;
    unsigned long tcenter, t0, t1, tm;
    long i;

    for (i = 0; i < NUM_ITERS; ++i) {
        t0 = ia64_get_itc();
        go[MASTER] = 1;
        while (!(tm = go[SLAVE]))
            cpu_relax();
        go[SLAVE] = 0;
        t1 = ia64_get_itc();

        if (t1 - t0 < best_t1 - best_t0)
            best_t0 = t0, best_t1 = t1, best_tm = tm;
    }

    *rt = best_t1 - best_t0;
    *master = best_tm - best_t0;

    /* average best_t0 and best_t1 without overflow: */
    tcenter = (best_t0/2 + best_t1/2);
    if (best_t0 % 2 + best_t1 % 2 == 2)
        ++tcenter;
    return tcenter - best_tm;
}

/*
 * Synchronize ar.itc of the current (slave) CPU with the ar.itc of the MASTER CPU
 * (normally the time-keeper CPU).  We use a closed loop to eliminate the possibility of
 * unaccounted-for errors (such as getting a machine check in the middle of a calibration
 * step).  The basic idea is for the slave to ask the master what itc value it has and to
 * read its own itc before and after the master responds.  Each iteration gives us three
 * timestamps:
 *
 *  slave       master
 *
 *  t0 ---\
 *             ---\
 *         --->
 *          tm
 *         /---
 *         /---
 *  t1 <---
 *
 *
 * The goal is to adjust the slave's ar.itc such that tm falls exactly half-way between t0
 * and t1.  If we achieve this, the clocks are synchronized provided the interconnect
 * between the slave and the master is symmetric.  Even if the interconnect were
 * asymmetric, we would still know that the synchronization error is smaller than the
 * roundtrip latency (t0 - t1).
 *
 * When the interconnect is quiet and symmetric, this lets us synchronize the itc to
 * within one or two cycles.  However, we can only *guarantee* that the synchronization is
 * accurate to within a round-trip time, which is typically in the range of several
 * hundred cycles (e.g., ~500 cycles).  In practice, this means that the itc's are usually
 * almost perfectly synchronized, but we shouldn't assume that the accuracy is much better
 * than half a micro second or so.
 */
void
ia64_sync_itc (unsigned int master)
{
    long i, delta, adj, adjust_latency = 0, done = 0;
    unsigned long flags, rt, master_time_stamp, bound;
#if DEBUG_ITC_SYNC
    struct {
        long rt;    /* roundtrip time */
        long master;    /* master's timestamp */
        long diff;  /* difference between midpoint and master's timestamp */
        long lat;   /* estimate of itc adjustment latency */
    } t[NUM_ROUNDS];
#endif

    /*
     * Make sure local timer ticks are disabled while we sync.  If
     * they were enabled, we'd have to worry about nasty issues
     * like setting the ITC ahead of (or a long time before) the
     * next scheduled tick.
     */
    BUG_ON((ia64_get_itv() & (1 << 16)) == 0);

    go[MASTER] = 1;

    if (smp_call_function_single(master, sync_master, NULL, 0) < 0) {
        printk(KERN_ERR "sync_itc: failed to get attention of CPU %u!\n", master);
        return;
    }

    while (go[MASTER])
        cpu_relax();    /* wait for master to be ready */

    spin_lock_irqsave(&itc_sync_lock, flags);
    {
        for (i = 0; i < NUM_ROUNDS; ++i) {
            delta = get_delta(&rt, &master_time_stamp);
            if (delta == 0) {
                done = 1;   /* let's lock on to this... */
                bound = rt;
            }

            if (!done) {
                if (i > 0) {
                    adjust_latency += -delta;
                    adj = -delta + adjust_latency/4;
                } else
                    adj = -delta;

                ia64_set_itc(ia64_get_itc() + adj);
            }
#if DEBUG_ITC_SYNC
            t[i].rt = rt;
            t[i].master = master_time_stamp;
            t[i].diff = delta;
            t[i].lat = adjust_latency/4;
#endif
        }
    }
    spin_unlock_irqrestore(&itc_sync_lock, flags);

#if DEBUG_ITC_SYNC
    for (i = 0; i < NUM_ROUNDS; ++i)
        printk("rt=%5ld master=%5ld diff=%5ld adjlat=%5ld\n",
               t[i].rt, t[i].master, t[i].diff, t[i].lat);
#endif

    printk(KERN_INFO "CPU %d: synchronized ITC with CPU %u (last diff %ld cycles, "
           "maxerr %lu cycles)\n", smp_processor_id(), master, delta, rt);
}

/*
 * Ideally sets up per-cpu profiling hooks.  Doesn't do much now...
 */
static inline void __devinit
smp_setup_percpu_timer (void)
{
}

static void __cpuinit
smp_callin (void)
{
    int cpuid, phys_id, itc_master;
    struct cpuinfo_ia64 *last_cpuinfo, *this_cpuinfo;
    extern void ia64_init_itm(void);
    extern volatile int time_keeper_id;

#ifdef CONFIG_PERFMON
    extern void pfm_init_percpu(void);
#endif

    cpuid = smp_processor_id();
    phys_id = hard_smp_processor_id();
    itc_master = time_keeper_id;

    if (cpu_online(cpuid)) {
        printk(KERN_ERR "huh, phys CPU#0x%x, CPU#0x%x already present??\n",
               phys_id, cpuid);
        BUG();
    }

    fix_b0_for_bsp();

    /*
     * numa_node_id() works after this.
     */
    set_numa_node(cpu_to_node_map[cpuid]);
    set_numa_mem(local_memory_node(cpu_to_node_map[cpuid]));

    spin_lock(&vector_lock);
    /* Setup the per cpu irq handling data structures */
    __setup_vector_irq(cpuid);
    notify_cpu_starting(cpuid);
    set_cpu_online(cpuid, true);
    per_cpu(cpu_state, cpuid) = CPU_ONLINE;
    spin_unlock(&vector_lock);

    smp_setup_percpu_timer();

    ia64_mca_cmc_vector_setup();    /* Setup vector on AP */

#ifdef CONFIG_PERFMON
    pfm_init_percpu();
#endif

    local_irq_enable();

    if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
        /*
         * Synchronize the ITC with the BP.  Need to do this after irqs are
         * enabled because ia64_sync_itc() calls smp_call_function_single(), which
         * calls spin_unlock_bh(), which calls spin_unlock_bh(), which calls
         * local_bh_enable(), which bugs out if irqs are not enabled...
         */
        Dprintk("Going to syncup ITC with ITC Master.\n");
        ia64_sync_itc(itc_master);
    }

    /*
     * Get our bogomips.
     */
    ia64_init_itm();

    /*
     * Delay calibration can be skipped if new processor is identical to the
     * previous processor.
     */
    last_cpuinfo = cpu_data(cpuid - 1);
    this_cpuinfo = local_cpu_data;
    if (last_cpuinfo->itc_freq != this_cpuinfo->itc_freq ||
        last_cpuinfo->proc_freq != this_cpuinfo->proc_freq ||
        last_cpuinfo->features != this_cpuinfo->features ||
        last_cpuinfo->revision != this_cpuinfo->revision ||
        last_cpuinfo->family != this_cpuinfo->family ||
        last_cpuinfo->archrev != this_cpuinfo->archrev ||
        last_cpuinfo->model != this_cpuinfo->model)
        calibrate_delay();
    local_cpu_data->loops_per_jiffy = loops_per_jiffy;

    /*
     * Allow the master to continue.
     */
    cpu_set(cpuid, cpu_callin_map);
    Dprintk("Stack on CPU %d at about %p\n",cpuid, &cpuid);
}


/*
 * Activate a secondary processor.  head.S calls this.
 */
int __cpuinit
start_secondary (void *unused)
{
    /* Early console may use I/O ports */
    ia64_set_kr(IA64_KR_IO_BASE, __pa(ia64_iobase));
#ifndef CONFIG_PRINTK_TIME
    Dprintk("start_secondary: starting CPU 0x%x\n", hard_smp_processor_id());
#endif
    efi_map_pal_code();
    cpu_init();
    preempt_disable();
    smp_callin();

    cpu_idle();
    return 0;
}

struct pt_regs * __cpuinit idle_regs(struct pt_regs *regs)
{
    return NULL;
}

static int __cpuinit
do_boot_cpu (int sapicid, int cpu, struct task_struct *idle)
{
    int timeout;

    task_for_booting_cpu = idle;
    Dprintk("Sending wakeup vector %lu to AP 0x%x/0x%x.\n", ap_wakeup_vector, cpu, sapicid);

    set_brendez_area(cpu);
    platform_send_ipi(cpu, ap_wakeup_vector, IA64_IPI_DM_INT, 0);

    /*
     * Wait 10s total for the AP to start
     */
    Dprintk("Waiting on callin_map ...");
    for (timeout = 0; timeout < 100000; timeout++) {
        if (cpu_isset(cpu, cpu_callin_map))
            break;  /* It has booted */
        udelay(100);
    }
    Dprintk("\n");

    if (!cpu_isset(cpu, cpu_callin_map)) {
        printk(KERN_ERR "Processor 0x%x/0x%x is stuck.\n", cpu, sapicid);
        ia64_cpu_to_sapicid[cpu] = -1;
        set_cpu_online(cpu, false);  /* was set in smp_callin() */
        return -EINVAL;
    }
    return 0;
}

static int __init
decay (char *str)
{
    int ticks;
    get_option (&str, &ticks);
    return 1;
}

__setup("decay=", decay);

/*
 * Initialize the logical CPU number to SAPICID mapping
 */
void __init
smp_build_cpu_map (void)
{
    int sapicid, cpu, i;
    int boot_cpu_id = hard_smp_processor_id();

    for (cpu = 0; cpu < NR_CPUS; cpu++) {
        ia64_cpu_to_sapicid[cpu] = -1;
    }

    ia64_cpu_to_sapicid[0] = boot_cpu_id;
    init_cpu_present(cpumask_of(0));
    set_cpu_possible(0, true);
    for (cpu = 1, i = 0; i < smp_boot_data.cpu_count; i++) {
        sapicid = smp_boot_data.cpu_phys_id[i];
        if (sapicid == boot_cpu_id)
            continue;
        set_cpu_present(cpu, true);
        set_cpu_possible(cpu, true);
        ia64_cpu_to_sapicid[cpu] = sapicid;
        cpu++;
    }
}

/*
 * Cycle through the APs sending Wakeup IPIs to boot each.
 */
void __init
smp_prepare_cpus (unsigned int max_cpus)
{
    int boot_cpu_id = hard_smp_processor_id();

    /*
     * Initialize the per-CPU profiling counter/multiplier
     */

    smp_setup_percpu_timer();

    cpu_set(0, cpu_callin_map);

    local_cpu_data->loops_per_jiffy = loops_per_jiffy;
    ia64_cpu_to_sapicid[0] = boot_cpu_id;

    printk(KERN_INFO "Boot processor id 0x%x/0x%x\n", 0, boot_cpu_id);

    current_thread_info()->cpu = 0;

    /*
     * If SMP should be disabled, then really disable it!
     */
    if (!max_cpus) {
        printk(KERN_INFO "SMP mode deactivated.\n");
        init_cpu_online(cpumask_of(0));
        init_cpu_present(cpumask_of(0));
        init_cpu_possible(cpumask_of(0));
        return;
    }
}

void __devinit smp_prepare_boot_cpu(void)
{
    set_cpu_online(smp_processor_id(), true);
    cpu_set(smp_processor_id(), cpu_callin_map);
    set_numa_node(cpu_to_node_map[smp_processor_id()]);
    per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
    paravirt_post_smp_prepare_boot_cpu();
}

#ifdef CONFIG_HOTPLUG_CPU
static inline void
clear_cpu_sibling_map(int cpu)
{
    int i;

    for_each_cpu_mask(i, per_cpu(cpu_sibling_map, cpu))
        cpu_clear(cpu, per_cpu(cpu_sibling_map, i));
    for_each_cpu_mask(i, cpu_core_map[cpu])
        cpu_clear(cpu, cpu_core_map[i]);

    per_cpu(cpu_sibling_map, cpu) = cpu_core_map[cpu] = CPU_MASK_NONE;
}

static void
remove_siblinginfo(int cpu)
{
    int last = 0;

    if (cpu_data(cpu)->threads_per_core == 1 &&
        cpu_data(cpu)->cores_per_socket == 1) {
        cpu_clear(cpu, cpu_core_map[cpu]);
        cpu_clear(cpu, per_cpu(cpu_sibling_map, cpu));
        return;
    }

    last = (cpus_weight(cpu_core_map[cpu]) == 1 ? 1 : 0);

    /* remove it from all sibling map's */
    clear_cpu_sibling_map(cpu);
}

extern void fixup_irqs(void);

int migrate_platform_irqs(unsigned int cpu)
{
    int new_cpei_cpu;
    struct irq_data *data = NULL;
    const struct cpumask *mask;
    int         retval = 0;

    /*
     * dont permit CPEI target to removed.
     */
    if (cpe_vector > 0 && is_cpu_cpei_target(cpu)) {
        printk ("CPU (%d) is CPEI Target\n", cpu);
        if (can_cpei_retarget()) {
            /*
             * Now re-target the CPEI to a different processor
             */
            new_cpei_cpu = cpumask_any(cpu_online_mask);
            mask = cpumask_of(new_cpei_cpu);
            set_cpei_target_cpu(new_cpei_cpu);
            data = irq_get_irq_data(ia64_cpe_irq);
            /*
             * Switch for now, immediately, we need to do fake intr
             * as other interrupts, but need to study CPEI behaviour with
             * polling before making changes.
             */
            if (data && data->chip) {
                data->chip->irq_disable(data);
                data->chip->irq_set_affinity(data, mask, false);
                data->chip->irq_enable(data);
                printk ("Re-targeting CPEI to cpu %d\n", new_cpei_cpu);
            }
        }
        if (!data) {
            printk ("Unable to retarget CPEI, offline cpu [%d] failed\n", cpu);
            retval = -EBUSY;
        }
    }
    return retval;
}

/* must be called with cpucontrol mutex held */
int __cpu_disable(void)
{
    int cpu = smp_processor_id();

    /*
     * dont permit boot processor for now
     */
    if (cpu == 0 && !bsp_remove_ok) {
        printk ("Your platform does not support removal of BSP\n");
        return (-EBUSY);
    }

    if (ia64_platform_is("sn2")) {
        if (!sn_cpu_disable_allowed(cpu))
            return -EBUSY;
    }

    set_cpu_online(cpu, false);

    if (migrate_platform_irqs(cpu)) {
        set_cpu_online(cpu, true);
        return -EBUSY;
    }

    remove_siblinginfo(cpu);
    fixup_irqs();
    local_flush_tlb_all();
    cpu_clear(cpu, cpu_callin_map);
    return 0;
}

void __cpu_die(unsigned int cpu)
{
    unsigned int i;

    for (i = 0; i < 100; 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);
            return;
        }
        msleep(100);
    }
    printk(KERN_ERR "CPU %u didn't die...\n", cpu);
}
#endif /* CONFIG_HOTPLUG_CPU */

void
smp_cpus_done (unsigned int dummy)
{
    int cpu;
    unsigned long bogosum = 0;

    /*
     * Allow the user to impress friends.
     */

    for_each_online_cpu(cpu) {
        bogosum += cpu_data(cpu)->loops_per_jiffy;
    }

    printk(KERN_INFO "Total of %d processors activated (%lu.%02lu BogoMIPS).\n",
           (int)num_online_cpus(), bogosum/(500000/HZ), (bogosum/(5000/HZ))%100);
}

static inline void __devinit
set_cpu_sibling_map(int cpu)
{
    int i;

    for_each_online_cpu(i) {
        if ((cpu_data(cpu)->socket_id == cpu_data(i)->socket_id)) {
            cpu_set(i, cpu_core_map[cpu]);
            cpu_set(cpu, cpu_core_map[i]);
            if (cpu_data(cpu)->core_id == cpu_data(i)->core_id) {
                cpu_set(i, per_cpu(cpu_sibling_map, cpu));
                cpu_set(cpu, per_cpu(cpu_sibling_map, i));
            }
        }
    }
}

int __cpuinit
__cpu_up(unsigned int cpu, struct task_struct *tidle)
{
    int ret;
    int sapicid;

    sapicid = ia64_cpu_to_sapicid[cpu];
    if (sapicid == -1)
        return -EINVAL;

    /*
     * Already booted cpu? not valid anymore since we dont
     * do idle loop tightspin anymore.
     */
    if (cpu_isset(cpu, cpu_callin_map))
        return -EINVAL;

    per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
    /* Processor goes to start_secondary(), sets online flag */
    ret = do_boot_cpu(sapicid, cpu, tidle);
    if (ret < 0)
        return ret;

    if (cpu_data(cpu)->threads_per_core == 1 &&
        cpu_data(cpu)->cores_per_socket == 1) {
        cpu_set(cpu, per_cpu(cpu_sibling_map, cpu));
        cpu_set(cpu, cpu_core_map[cpu]);
        return 0;
    }

    set_cpu_sibling_map(cpu);

    return 0;
}

/*
 * Assume that CPUs have been discovered by some platform-dependent interface.  For
 * SoftSDV/Lion, that would be ACPI.
 *
 * Setup of the IPI irq handler is done in irq.c:init_IRQ_SMP().
 */
void __init
init_smp_config(void)
{
    struct fptr {
        unsigned long fp;
        unsigned long gp;
    } *ap_startup;
    long sal_ret;

    /* Tell SAL where to drop the APs.  */
    ap_startup = (struct fptr *) start_ap;
    sal_ret = ia64_sal_set_vectors(SAL_VECTOR_OS_BOOT_RENDEZ,
                       ia64_tpa(ap_startup->fp), ia64_tpa(ap_startup->gp), 0, 0, 0, 0);
    if (sal_ret < 0)
        printk(KERN_ERR "SMP: Can't set SAL AP Boot Rendezvous: %s\n",
               ia64_sal_strerror(sal_ret));
}

/*
 * identify_siblings(cpu) gets called from identify_cpu. This populates the 
 * information related to logical execution units in per_cpu_data structure.
 */
void __devinit
identify_siblings(struct cpuinfo_ia64 *c)
{
    long status;
    u16 pltid;
    pal_logical_to_physical_t info;

    status = ia64_pal_logical_to_phys(-1, &info);
    if (status != PAL_STATUS_SUCCESS) {
        if (status != PAL_STATUS_UNIMPLEMENTED) {
            printk(KERN_ERR
                "ia64_pal_logical_to_phys failed with %ld\n",
                status);
            return;
        }

        info.overview_ppid = 0;
        info.overview_cpp  = 1;
        info.overview_tpc  = 1;
    }

    status = ia64_sal_physical_id_info(&pltid);
    if (status != PAL_STATUS_SUCCESS) {
        if (status != PAL_STATUS_UNIMPLEMENTED)
            printk(KERN_ERR
                "ia64_sal_pltid failed with %ld\n",
                status);
        return;
    }

    c->socket_id =  (pltid << 8) | info.overview_ppid;

    if (info.overview_cpp == 1 && info.overview_tpc == 1)
        return;

    c->cores_per_socket = info.overview_cpp;
    c->threads_per_core = info.overview_tpc;
    c->num_log = info.overview_num_log;

    c->core_id = info.log1_cid;
    c->thread_id = info.log1_tid;
}

/*
 * returns non zero, if multi-threading is enabled
 * on at least one physical package. Due to hotplug cpu
 * and (maxcpus=), all threads may not necessarily be enabled
 * even though the processor supports multi-threading.
 */
int is_multithreading_enabled(void)
{
    int i, j;

    for_each_present_cpu(i) {
        for_each_present_cpu(j) {
            if (j == i)
                continue;
            if ((cpu_data(j)->socket_id == cpu_data(i)->socket_id)) {
                if (cpu_data(j)->core_id == cpu_data(i)->core_id)
                    return 1;
            }
        }
    }
    return 0;
}
EXPORT_SYMBOL_GPL(is_multithreading_enabled);