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-rw-r--r--arch/x86/kernel/smpboot.c1439
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diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
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+/*
+ * 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 <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];
+#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 };
+
+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);
+}
+
+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.
+ */
+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.
+ */
+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);
+ }
+
+ /* 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
+}
+
+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
+
+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;
+
+ /*
+ * 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);
+
+ 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");
+ 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_possible_map);
+ 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 + USER_PGD_PTRS,
+ min_t(unsigned long, KERNEL_PGD_PTRS, USER_PGD_PTRS));
+ flush_tlb_all();
+#endif
+
+ err = do_boot_cpu(apicid, cpu);
+ if (err < 0) {
+ Dprintk("do_boot_cpu failed %d\n", err);
+ return err;
+ }
+
+ /*
+ * 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_isset(cpu, cpu_online_map)) {
+ 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
+ if (nmi_watchdog == NMI_LOCAL_APIC) {
+ printk(KERN_INFO "activating minimal APIC for"
+ "NMI watchdog use.\n");
+ connect_bsp_APIC();
+ setup_local_APIC();
+ end_local_APIC_setup();
+ }
+#endif
+ return -1;
+ }
+
+ return 0;
+}
+
+static void __init smp_cpu_index_default(void)
+{
+ int i;
+ struct cpuinfo_x86 *c;
+
+ for_each_cpu_mask(i, cpu_possible_map) {
+ 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)
+{
+ 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();
+ return;
+ }
+
+ 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();
+}
+/*
+ * 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_X86_32
+ zap_low_mappings();
+#endif
+}
+
+#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 */
+
+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);
+}
+
+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);