// SPDX-License-Identifier: GPL-2.0-only
/*
* SMP boot-related support
*
* Copyright (C) 1998-2003, 2005 Hewlett-Packard Co
* David Mosberger-Tang <davidm@hpl.hp.com>
* Copyright (C) 2001, 2004-2005 Intel Corp
* Rohit Seth <rohit.seth@intel.com>
* Suresh Siddha <suresh.b.siddha@intel.com>
* Gordon Jin <gordon.jin@intel.com>
* Ashok Raj <ashok.raj@intel.com>
*
* 01/05/16 Rohit Seth <rohit.seth@intel.com> Moved SMP booting functions from smp.c to here.
* 01/04/27 David Mosberger <davidm@hpl.hp.com> Added ITC synching code.
* 02/07/31 David Mosberger <davidm@hpl.hp.com> 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 <ashok.raj@intel.com> Added CPU Hotplug Support
* 04/12/26 Jin Gordon <gordon.jin@intel.com>
* 04/12/26 Rohit Seth <rohit.seth@intel.com>
* Add multi-threading and multi-core detection
* 05/01/30 Suresh Siddha <suresh.b.siddha@intel.com>
* Setup cpu_sibling_map and cpu_core_map
*/
#include <linux/module.h>
#include <linux/acpi.h>
#include <linux/memblock.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/efi.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/mca.h>
#include <asm/page.h>
#include <asm/processor.h>
#include <asm/ptrace.h>
#include <asm/sal.h>
#include <asm/tlbflush.h>
#include <asm/unistd.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 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 smp_setup_percpu_timer(void)
{
}
static void
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;
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 */
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.
*/
cpumask_set_cpu(cpuid, &cpu_callin_map);
Dprintk("Stack on CPU %d at about %p\n",cpuid, &cpuid);
}
/*
* Activate a secondary processor. head.S calls this.
*/
int
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();
smp_callin();
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
return 0;
}
static int
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);
ia64_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 (cpumask_test_cpu(cpu, &cpu_callin_map))
break; /* It has booted */
barrier(); /* Make sure we re-read cpu_callin_map */
udelay(100);
}
Dprintk("\n");
if (!cpumask_test_cpu(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();
cpumask_set_cpu(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 smp_prepare_boot_cpu(void)
{
set_cpu_online(smp_processor_id(), true);
cpumask_set_cpu(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;
}
#ifdef CONFIG_HOTPLUG_CPU
static inline void
clear_cpu_sibling_map(int cpu)
{
int i;
for_each_cpu(i, &per_cpu(cpu_sibling_map, cpu))
cpumask_clear_cpu(cpu, &per_cpu(cpu_sibling_map, i));
for_each_cpu(i, &cpu_core_map[cpu])
cpumask_clear_cpu(cpu, &cpu_core_map[i]);
per_cpu(cpu_sibling_map, cpu) = cpu_core_map[cpu] = CPU_MASK_NONE;
}
static void
remove_siblinginfo(int cpu)
{
if (cpu_data(cpu)->threads_per_core == 1 &&
cpu_data(cpu)->cores_per_socket == 1) {
cpumask_clear_cpu(cpu, &cpu_core_map[cpu]);
cpumask_clear_cpu(cpu, &per_cpu(cpu_sibling_map, cpu));
return;
}
/* 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);
}
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();
cpumask_clear_cpu(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 set_cpu_sibling_map(int cpu)
{
int i;
for_each_online_cpu(i) {
if ((cpu_data(cpu)->socket_id == cpu_data(i)->socket_id)) {
cpumask_set_cpu(i, &cpu_core_map[cpu]);
cpumask_set_cpu(cpu, &cpu_core_map[i]);
if (cpu_data(cpu)->core_id == cpu_data(i)->core_id) {
cpumask_set_cpu(i,
&per_cpu(cpu_sibling_map, cpu));
cpumask_set_cpu(cpu,
&per_cpu(cpu_sibling_map, i));
}
}
}
}
int
__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 (cpumask_test_cpu(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) {
cpumask_set_cpu(cpu, &per_cpu(cpu_sibling_map, cpu));
cpumask_set_cpu(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 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);