arch/x86/kernel/apic_64.c

/*
 *	Local APIC handling, local APIC timers
 *
 *	(c) 1999, 2000 Ingo Molnar <mingo@redhat.com>
 *
 *	Fixes
 *	Maciej W. Rozycki	:	Bits for genuine 82489DX APICs;
 *					thanks to Eric Gilmore
 *					and Rolf G. Tews
 *					for testing these extensively.
 *	Maciej W. Rozycki	:	Various updates and fixes.
 *	Mikael Pettersson	:	Power Management for UP-APIC.
 *	Pavel Machek and
 *	Mikael Pettersson	:	PM converted to driver model.
 */

#include <linux/init.h>

#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/bootmem.h>
#include <linux/interrupt.h>
#include <linux/mc146818rtc.h>
#include <linux/kernel_stat.h>
#include <linux/sysdev.h>
#include <linux/ioport.h>
#include <linux/clockchips.h>
#include <linux/acpi_pmtmr.h>
#include <linux/module.h>
#include <linux/dmar.h>

#include <asm/atomic.h>
#include <asm/smp.h>
#include <asm/mtrr.h>
#include <asm/mpspec.h>
#include <asm/hpet.h>
#include <asm/pgalloc.h>
#include <asm/nmi.h>
#include <asm/idle.h>
#include <asm/proto.h>
#include <asm/timex.h>
#include <asm/apic.h>
#include <asm/i8259.h>

#include <mach_ipi.h>
#include <mach_apic.h>

/* Disable local APIC timer from the kernel commandline or via dmi quirk */
static int disable_apic_timer __cpuinitdata;
static int apic_calibrate_pmtmr __initdata;
int disable_apic;
int disable_x2apic;
int x2apic;

/* x2apic enabled before OS handover */
int x2apic_preenabled;

/* Local APIC timer works in C2 */
int local_apic_timer_c2_ok;
EXPORT_SYMBOL_GPL(local_apic_timer_c2_ok);

/*
 * Debug level, exported for io_apic.c
 */
unsigned int apic_verbosity;

/* Have we found an MP table */
int smp_found_config;

static struct resource lapic_resource = {
	.name = "Local APIC",
	.flags = IORESOURCE_MEM | IORESOURCE_BUSY,
};

static unsigned int calibration_result;

static int lapic_next_event(unsigned long delta,
			    struct clock_event_device *evt);
static void lapic_timer_setup(enum clock_event_mode mode,
			      struct clock_event_device *evt);
static void lapic_timer_broadcast(cpumask_t mask);
static void apic_pm_activate(void);

/*
 * The local apic timer can be used for any function which is CPU local.
 */
static struct clock_event_device lapic_clockevent = {
	.name		= "lapic",
	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT
			| CLOCK_EVT_FEAT_C3STOP | CLOCK_EVT_FEAT_DUMMY,
	.shift		= 32,
	.set_mode	= lapic_timer_setup,
	.set_next_event	= lapic_next_event,
	.broadcast	= lapic_timer_broadcast,
	.rating		= 100,
	.irq		= -1,
};
static DEFINE_PER_CPU(struct clock_event_device, lapic_events);

static unsigned long apic_phys;
unsigned int __cpuinitdata maxcpus = NR_CPUS;

unsigned long mp_lapic_addr;

/*
 * Get the LAPIC version
 */
static inline int lapic_get_version(void)
{
	return GET_APIC_VERSION(apic_read(APIC_LVR));
}

/*
 * Check, if the APIC is integrated or a separate chip
 */
static inline int lapic_is_integrated(void)
{
#ifdef CONFIG_X86_64
	return 1;
#else
	return APIC_INTEGRATED(lapic_get_version());
#endif
}

/*
 * Check, whether this is a modern or a first generation APIC
 */
static int modern_apic(void)
{
	/* AMD systems use old APIC versions, so check the CPU */
	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
	    boot_cpu_data.x86 >= 0xf)
		return 1;
	return lapic_get_version() >= 0x14;
}

/*
 * Paravirt kernels also might be using these below ops. So we still
 * use generic apic_read()/apic_write(), which might be pointing to different
 * ops in PARAVIRT case.
 */
void xapic_wait_icr_idle(void)
{
	while (apic_read(APIC_ICR) & APIC_ICR_BUSY)
		cpu_relax();
}

u32 safe_xapic_wait_icr_idle(void)
{
	u32 send_status;
	int timeout;

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

	return send_status;
}

void xapic_icr_write(u32 low, u32 id)
{
	apic_write(APIC_ICR2, SET_APIC_DEST_FIELD(id));
	apic_write(APIC_ICR, low);
}

u64 xapic_icr_read(void)
{
	u32 icr1, icr2;

	icr2 = apic_read(APIC_ICR2);
	icr1 = apic_read(APIC_ICR);

	return icr1 | ((u64)icr2 << 32);
}

static struct apic_ops xapic_ops = {
	.read = native_apic_mem_read,
	.write = native_apic_mem_write,
	.icr_read = xapic_icr_read,
	.icr_write = xapic_icr_write,
	.wait_icr_idle = xapic_wait_icr_idle,
	.safe_wait_icr_idle = safe_xapic_wait_icr_idle,
};

struct apic_ops __read_mostly *apic_ops = &xapic_ops;
EXPORT_SYMBOL_GPL(apic_ops);

static void x2apic_wait_icr_idle(void)
{
	/* no need to wait for icr idle in x2apic */
	return;
}

static u32 safe_x2apic_wait_icr_idle(void)
{
	/* no need to wait for icr idle in x2apic */
	return 0;
}

void x2apic_icr_write(u32 low, u32 id)
{
	wrmsrl(APIC_BASE_MSR + (APIC_ICR >> 4), ((__u64) id) << 32 | low);
}

u64 x2apic_icr_read(void)
{
	unsigned long val;

	rdmsrl(APIC_BASE_MSR + (APIC_ICR >> 4), val);
	return val;
}

static struct apic_ops x2apic_ops = {
	.read = native_apic_msr_read,
	.write = native_apic_msr_write,
	.icr_read = x2apic_icr_read,
	.icr_write = x2apic_icr_write,
	.wait_icr_idle = x2apic_wait_icr_idle,
	.safe_wait_icr_idle = safe_x2apic_wait_icr_idle,
};

/**
 * enable_NMI_through_LVT0 - enable NMI through local vector table 0
 */
void __cpuinit enable_NMI_through_LVT0(void)
{
	unsigned int v;

	/* unmask and set to NMI */
	v = APIC_DM_NMI;

	/* Level triggered for 82489DX (32bit mode) */
	if (!lapic_is_integrated())
		v |= APIC_LVT_LEVEL_TRIGGER;

	apic_write(APIC_LVT0, v);
}

/**
 * lapic_get_maxlvt - get the maximum number of local vector table entries
 */
int lapic_get_maxlvt(void)
{
	unsigned int v;

	v = apic_read(APIC_LVR);
	/*
	 * - we always have APIC integrated on 64bit mode
	 * - 82489DXs do not report # of LVT entries
	 */
	return APIC_INTEGRATED(GET_APIC_VERSION(v)) ? GET_APIC_MAXLVT(v) : 2;
}

/*
 * Local APIC timer
 */

/* Clock divisor is set to 1 */
#define APIC_DIVISOR 1

/*
 * This function sets up the local APIC timer, with a timeout of
 * 'clocks' APIC bus clock. During calibration we actually call
 * this function twice on the boot CPU, once with a bogus timeout
 * value, second time for real. The other (noncalibrating) CPUs
 * call this function only once, with the real, calibrated value.
 *
 * We do reads before writes even if unnecessary, to get around the
 * P5 APIC double write bug.
 */
static void __setup_APIC_LVTT(unsigned int clocks, int oneshot, int irqen)
{
	unsigned int lvtt_value, tmp_value;

	lvtt_value = LOCAL_TIMER_VECTOR;
	if (!oneshot)
		lvtt_value |= APIC_LVT_TIMER_PERIODIC;
	if (!lapic_is_integrated())
		lvtt_value |= SET_APIC_TIMER_BASE(APIC_TIMER_BASE_DIV);

	if (!irqen)
		lvtt_value |= APIC_LVT_MASKED;

	apic_write(APIC_LVTT, lvtt_value);

	/*
	 * Divide PICLK by 16
	 */
	tmp_value = apic_read(APIC_TDCR);
	apic_write(APIC_TDCR, (tmp_value
				& ~(APIC_TDR_DIV_1 | APIC_TDR_DIV_TMBASE))
				| APIC_TDR_DIV_16);

	if (!oneshot)
		apic_write(APIC_TMICT, clocks / APIC_DIVISOR);
}

/*
 * Setup extended LVT, AMD specific (K8, family 10h)
 *
 * Vector mappings are hard coded. On K8 only offset 0 (APIC500) and
 * MCE interrupts are supported. Thus MCE offset must be set to 0.
 */

#define APIC_EILVT_LVTOFF_MCE 0
#define APIC_EILVT_LVTOFF_IBS 1

static void setup_APIC_eilvt(u8 lvt_off, u8 vector, u8 msg_type, u8 mask)
{
	unsigned long reg = (lvt_off << 4) + APIC_EILVT0;
	unsigned int  v   = (mask << 16) | (msg_type << 8) | vector;

	apic_write(reg, v);
}

u8 setup_APIC_eilvt_mce(u8 vector, u8 msg_type, u8 mask)
{
	setup_APIC_eilvt(APIC_EILVT_LVTOFF_MCE, vector, msg_type, mask);
	return APIC_EILVT_LVTOFF_MCE;
}

u8 setup_APIC_eilvt_ibs(u8 vector, u8 msg_type, u8 mask)
{
	setup_APIC_eilvt(APIC_EILVT_LVTOFF_IBS, vector, msg_type, mask);
	return APIC_EILVT_LVTOFF_IBS;
}

/*
 * Program the next event, relative to now
 */
static int lapic_next_event(unsigned long delta,
			    struct clock_event_device *evt)
{
	apic_write(APIC_TMICT, delta);
	return 0;
}

/*
 * Setup the lapic timer in periodic or oneshot mode
 */
static void lapic_timer_setup(enum clock_event_mode mode,
			      struct clock_event_device *evt)
{
	unsigned long flags;
	unsigned int v;

	/* Lapic used as dummy for broadcast ? */
	if (evt->features & CLOCK_EVT_FEAT_DUMMY)
		return;

	local_irq_save(flags);

	switch (mode) {
	case CLOCK_EVT_MODE_PERIODIC:
	case CLOCK_EVT_MODE_ONESHOT:
		__setup_APIC_LVTT(calibration_result,
				  mode != CLOCK_EVT_MODE_PERIODIC, 1);
		break;
	case CLOCK_EVT_MODE_UNUSED:
	case CLOCK_EVT_MODE_SHUTDOWN:
		v = apic_read(APIC_LVTT);
		v |= (APIC_LVT_MASKED | LOCAL_TIMER_VECTOR);
		apic_write(APIC_LVTT, v);
		break;
	case CLOCK_EVT_MODE_RESUME:
		/* Nothing to do here */
		break;
	}

	local_irq_restore(flags);
}

/*
 * Local APIC timer broadcast function
 */
static void lapic_timer_broadcast(cpumask_t mask)
{
#ifdef CONFIG_SMP
	send_IPI_mask(mask, LOCAL_TIMER_VECTOR);
#endif
}

/*
 * Setup the local APIC timer for this CPU. Copy the initilized values
 * of the boot CPU and register the clock event in the framework.
 */
static void setup_APIC_timer(void)
{
	struct clock_event_device *levt = &__get_cpu_var(lapic_events);

	memcpy(levt, &lapic_clockevent, sizeof(*levt));
	levt->cpumask = cpumask_of_cpu(smp_processor_id());

	clockevents_register_device(levt);
}

/*
 * In this function we calibrate APIC bus clocks to the external
 * timer. Unfortunately we cannot use jiffies and the timer irq
 * to calibrate, since some later bootup code depends on getting
 * the first irq? Ugh.
 *
 * We want to do the calibration only once since we
 * want to have local timer irqs syncron. CPUs connected
 * by the same APIC bus have the very same bus frequency.
 * And we want to have irqs off anyways, no accidental
 * APIC irq that way.
 */

#define TICK_COUNT 100000000

static int __init calibrate_APIC_clock(void)
{
	unsigned apic, apic_start;
	unsigned long tsc, tsc_start;
	int result;

	local_irq_disable();

	/*
	 * Put whatever arbitrary (but long enough) timeout
	 * value into the APIC clock, we just want to get the
	 * counter running for calibration.
	 *
	 * No interrupt enable !
	 */
	__setup_APIC_LVTT(250000000, 0, 0);

	apic_start = apic_read(APIC_TMCCT);
#ifdef CONFIG_X86_PM_TIMER
	if (apic_calibrate_pmtmr && pmtmr_ioport) {
		pmtimer_wait(5000);  /* 5ms wait */
		apic = apic_read(APIC_TMCCT);
		result = (apic_start - apic) * 1000L / 5;
	} else
#endif
	{
		rdtscll(tsc_start);

		do {
			apic = apic_read(APIC_TMCCT);
			rdtscll(tsc);
		} while ((tsc - tsc_start) < TICK_COUNT &&
				(apic_start - apic) < TICK_COUNT);

		result = (apic_start - apic) * 1000L * tsc_khz /
					(tsc - tsc_start);
	}

	local_irq_enable();

	printk(KERN_DEBUG "APIC timer calibration result %d\n", result);

	printk(KERN_INFO "Detected %d.%03d MHz APIC timer.\n",
		result / 1000 / 1000, result / 1000 % 1000);

	/* Calculate the scaled math multiplication factor */
	lapic_clockevent.mult = div_sc(result, NSEC_PER_SEC,
				       lapic_clockevent.shift);
	lapic_clockevent.max_delta_ns =
		clockevent_delta2ns(0x7FFFFF, &lapic_clockevent);
	lapic_clockevent.min_delta_ns =
		clockevent_delta2ns(0xF, &lapic_clockevent);

	calibration_result = (result * APIC_DIVISOR) / HZ;

	/*
	 * Do a sanity check on the APIC calibration result
	 */
	if (calibration_result < (1000000 / HZ)) {
		printk(KERN_WARNING
			"APIC frequency too slow, disabling apic timer\n");
		return -1;
	}

	return 0;
}

/*
 * Setup the boot APIC
 *
 * Calibrate and verify the result.
 */
void __init setup_boot_APIC_clock(void)
{
	/*
	 * The local apic timer can be disabled via the kernel
	 * commandline or from the CPU detection code. Register the lapic
	 * timer as a dummy clock event source on SMP systems, so the
	 * broadcast mechanism is used. On UP systems simply ignore it.
	 */
	if (disable_apic_timer) {
		printk(KERN_INFO "Disabling APIC timer\n");
		/* No broadcast on UP ! */
		if (num_possible_cpus() > 1) {
			lapic_clockevent.mult = 1;
			setup_APIC_timer();
		}
		return;
	}

	apic_printk(APIC_VERBOSE, "Using local APIC timer interrupts.\n"
		    "calibrating APIC timer ...\n");

	if (calibrate_APIC_clock()) {
		/* No broadcast on UP ! */
		if (num_possible_cpus() > 1)
			setup_APIC_timer();
		return;
	}

	/*
	 * If nmi_watchdog is set to IO_APIC, we need the
	 * PIT/HPET going.  Otherwise register lapic as a dummy
	 * device.
	 */
	if (nmi_watchdog != NMI_IO_APIC)
		lapic_clockevent.features &= ~CLOCK_EVT_FEAT_DUMMY;
	else
		printk(KERN_WARNING "APIC timer registered as dummy,"
			" due to nmi_watchdog=%d!\n", nmi_watchdog);

	/* Setup the lapic or request the broadcast */
	setup_APIC_timer();
}

void __cpuinit setup_secondary_APIC_clock(void)
{
	setup_APIC_timer();
}

/*
 * The guts of the apic timer interrupt
 */
static void local_apic_timer_interrupt(void)
{
	int cpu = smp_processor_id();
	struct clock_event_device *evt = &per_cpu(lapic_events, cpu);

	/*
	 * Normally we should not be here till LAPIC has been initialized but
	 * in some cases like kdump, its possible that there is a pending LAPIC
	 * timer interrupt from previous kernel's context and is delivered in
	 * new kernel the moment interrupts are enabled.
	 *
	 * Interrupts are enabled early and LAPIC is setup much later, hence
	 * its possible that when we get here evt->event_handler is NULL.
	 * Check for event_handler being NULL and discard the interrupt as
	 * spurious.
	 */
	if (!evt->event_handler) {
		printk(KERN_WARNING
		       "Spurious LAPIC timer interrupt on cpu %d\n", cpu);
		/* Switch it off */
		lapic_timer_setup(CLOCK_EVT_MODE_SHUTDOWN, evt);
		return;
	}

	/*
	 * the NMI deadlock-detector uses this.
	 */
	add_pda(apic_timer_irqs, 1);

	evt->event_handler(evt);
}

/*
 * Local APIC timer interrupt. This is the most natural way for doing
 * local interrupts, but local timer interrupts can be emulated by
 * broadcast interrupts too. [in case the hw doesn't support APIC timers]
 *
 * [ if a single-CPU system runs an SMP kernel then we call the local
 *   interrupt as well. Thus we cannot inline the local irq ... ]
 */
void smp_apic_timer_interrupt(struct pt_regs *regs)
{
	struct pt_regs *old_regs = set_irq_regs(regs);

	/*
	 * NOTE! We'd better ACK the irq immediately,
	 * because timer handling can be slow.
	 */
	ack_APIC_irq();
	/*
	 * update_process_times() expects us to have done irq_enter().
	 * Besides, if we don't timer interrupts ignore the global
	 * interrupt lock, which is the WrongThing (tm) to do.
	 */
	exit_idle();
	irq_enter();
	local_apic_timer_interrupt();
	irq_exit();

	set_irq_regs(old_regs);
}

int setup_profiling_timer(unsigned int multiplier)
{
	return -EINVAL;
}


/*
 * Local APIC start and shutdown
 */

/**
 * clear_local_APIC - shutdown the local APIC
 *
 * This is called, when a CPU is disabled and before rebooting, so the state of
 * the local APIC has no dangling leftovers. Also used to cleanout any BIOS
 * leftovers during boot.
 */
void clear_local_APIC(void)
{
	int maxlvt;
	u32 v;

	/* APIC hasn't been mapped yet */
	if (!apic_phys)
		return;

	maxlvt = lapic_get_maxlvt();
	/*
	 * Masking an LVT entry can trigger a local APIC error
	 * if the vector is zero. Mask LVTERR first to prevent this.
	 */
	if (maxlvt >= 3) {
		v = ERROR_APIC_VECTOR; /* any non-zero vector will do */
		apic_write(APIC_LVTERR, v | APIC_LVT_MASKED);
	}
	/*
	 * Careful: we have to set masks only first to deassert
	 * any level-triggered sources.
	 */
	v = apic_read(APIC_LVTT);
	apic_write(APIC_LVTT, v | APIC_LVT_MASKED);
	v = apic_read(APIC_LVT0);
	apic_write(APIC_LVT0, v | APIC_LVT_MASKED);
	v = apic_read(APIC_LVT1);
	apic_write(APIC_LVT1, v | APIC_LVT_MASKED);
	if (maxlvt >= 4) {
		v = apic_read(APIC_LVTPC);
		apic_write(APIC_LVTPC, v | APIC_LVT_MASKED);
	}

	/* lets not touch this if we didn't frob it */
#if defined(CONFIG_X86_MCE_P4THERMAL) || defined(X86_MCE_INTEL)
	if (maxlvt >= 5) {
		v = apic_read(APIC_LVTTHMR);
		apic_write(APIC_LVTTHMR, v | APIC_LVT_MASKED);
	}
#endif
	/*
	 * Clean APIC state for other OSs:
	 */
	apic_write(APIC_LVTT, APIC_LVT_MASKED);
	apic_write(APIC_LVT0, APIC_LVT_MASKED);
	apic_write(APIC_LVT1, APIC_LVT_MASKED);
	if (maxlvt >= 3)
		apic_write(APIC_LVTERR, APIC_LVT_MASKED);
	if (maxlvt >= 4)
		apic_write(APIC_LVTPC, APIC_LVT_MASKED);

	/* Integrated APIC (!82489DX) ? */
	if (lapic_is_integrated()) {
		if (maxlvt > 3)
			/* Clear ESR due to Pentium errata 3AP and 11AP */
			apic_write(APIC_ESR, 0);
		apic_read(APIC_ESR);
	}
}

/**
 * disable_local_APIC - clear and disable the local APIC
 */
void disable_local_APIC(void)
{
	unsigned int value;

	clear_local_APIC();

	/*
	 * Disable APIC (implies clearing of registers
	 * for 82489DX!).
	 */
	value = apic_read(APIC_SPIV);
	value &= ~APIC_SPIV_APIC_ENABLED;
	apic_write(APIC_SPIV, value);

#ifdef CONFIG_X86_32
	/*
	 * When LAPIC was disabled by the BIOS and enabled by the kernel,
	 * restore the disabled state.
	 */
	if (enabled_via_apicbase) {
		unsigned int l, h;

		rdmsr(MSR_IA32_APICBASE, l, h);
		l &= ~MSR_IA32_APICBASE_ENABLE;
		wrmsr(MSR_IA32_APICBASE, l, h);
	}
#endif
}

void lapic_shutdown(void)
{
	unsigned long flags;

	if (!cpu_has_apic)
		return;

	local_irq_save(flags);

	disable_local_APIC();

	local_irq_restore(flags);
}

/*
 * This is to verify that we're looking at a real local APIC.
 * Check these against your board if the CPUs aren't getting
 * started for no apparent reason.
 */
int __init verify_local_APIC(void)
{
	unsigned int reg0, reg1;

	/*
	 * The version register is read-only in a real APIC.
	 */
	reg0 = apic_read(APIC_LVR);
	apic_printk(APIC_DEBUG, "Getting VERSION: %x\n", reg0);
	apic_write(APIC_LVR, reg0 ^ APIC_LVR_MASK);
	reg1 = apic_read(APIC_LVR);
	apic_printk(APIC_DEBUG, "Getting VERSION: %x\n", reg1);

	/*
	 * The two version reads above should print the same
	 * numbers.  If the second one is different, then we
	 * poke at a non-APIC.
	 */
	if (reg1 != reg0)
		return 0;

	/*
	 * Check if the version looks reasonably.
	 */
	reg1 = GET_APIC_VERSION(reg0);
	if (reg1 == 0x00 || reg1 == 0xff)
		return 0;
	reg1 = lapic_get_maxlvt();
	if (reg1 < 0x02 || reg1 == 0xff)
		return 0;

	/*
	 * The ID register is read/write in a real APIC.
	 */
	reg0 = apic_read(APIC_ID);
	apic_printk(APIC_DEBUG, "Getting ID: %x\n", reg0);
	apic_write(APIC_ID, reg0 ^ APIC_ID_MASK);
	reg1 = apic_read(APIC_ID);
	apic_printk(APIC_DEBUG, "Getting ID: %x\n", reg1);
	apic_write(APIC_ID, reg0);
	if (reg1 != (reg0 ^ APIC_ID_MASK))
		return 0;

	/*
	 * The next two are just to see if we have sane values.
	 * They're only really relevant if we're in Virtual Wire
	 * compatibility mode, but most boxes are anymore.
	 */
	reg0 = apic_read(APIC_LVT0);
	apic_printk(APIC_DEBUG, "Getting LVT0: %x\n", reg0);
	reg1 = apic_read(APIC_LVT1);
	apic_printk(APIC_DEBUG, "Getting LVT1: %x\n", reg1);

	return 1;
}

/**
 * sync_Arb_IDs - synchronize APIC bus arbitration IDs
 */
void __init sync_Arb_IDs(void)
{
	/*
	 * Unsupported on P4 - see Intel Dev. Manual Vol. 3, Ch. 8.6.1 And not
	 * needed on AMD.
	 */
	if (modern_apic() || boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
		return;

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

	apic_printk(APIC_DEBUG, "Synchronizing Arb IDs.\n");
	apic_write(APIC_ICR, APIC_DEST_ALLINC |
			APIC_INT_LEVELTRIG | APIC_DM_INIT);
}

/*
 * An initial setup of the virtual wire mode.
 */
void __init init_bsp_APIC(void)
{
	unsigned int value;

	/*
	 * Don't do the setup now if we have a SMP BIOS as the
	 * through-I/O-APIC virtual wire mode might be active.
	 */
	if (smp_found_config || !cpu_has_apic)
		return;

	/*
	 * Do not trust the local APIC being empty at bootup.
	 */
	clear_local_APIC();

	/*
	 * Enable APIC.
	 */
	value = apic_read(APIC_SPIV);
	value &= ~APIC_VECTOR_MASK;
	value |= APIC_SPIV_APIC_ENABLED;

#ifdef CONFIG_X86_32
	/* This bit is reserved on P4/Xeon and should be cleared */
	if ((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) &&
	    (boot_cpu_data.x86 == 15))
		value &= ~APIC_SPIV_FOCUS_DISABLED;
	else
#endif
		value |= APIC_SPIV_FOCUS_DISABLED;
	value |= SPURIOUS_APIC_VECTOR;
	apic_write(APIC_SPIV, value);

	/*
	 * Set up the virtual wire mode.
	 */
	apic_write(APIC_LVT0, APIC_DM_EXTINT);
	value = APIC_DM_NMI;
	if (!lapic_is_integrated())		/* 82489DX */
		value |= APIC_LVT_LEVEL_TRIGGER;
	apic_write(APIC_LVT1, value);
}

/**
 * setup_local_APIC - setup the local APIC
 */
void __cpuinit setup_local_APIC(void)
{
	unsigned int value;
	int i, j;

	preempt_disable();
	value = apic_read(APIC_LVR);

	BUILD_BUG_ON((SPURIOUS_APIC_VECTOR & 0x0f) != 0x0f);

	/*
	 * Double-check whether this APIC is really registered.
	 * This is meaningless in clustered apic mode, so we skip it.
	 */
	if (!apic_id_registered())
		BUG();

	/*
	 * Intel recommends to set DFR, LDR and TPR before enabling
	 * an APIC.  See e.g. "AP-388 82489DX User's Manual" (Intel
	 * document number 292116).  So here it goes...
	 */
	init_apic_ldr();

	/*
	 * Set Task Priority to 'accept all'. We never change this
	 * later on.
	 */
	value = apic_read(APIC_TASKPRI);
	value &= ~APIC_TPRI_MASK;
	apic_write(APIC_TASKPRI, value);

	/*
	 * After a crash, we no longer service the interrupts and a pending
	 * interrupt from previous kernel might still have ISR bit set.
	 *
	 * Most probably by now CPU has serviced that pending interrupt and
	 * it might not have done the ack_APIC_irq() because it thought,
	 * interrupt came from i8259 as ExtInt. LAPIC did not get EOI so it
	 * does not clear the ISR bit and cpu thinks it has already serivced
	 * the interrupt. Hence a vector might get locked. It was noticed
	 * for timer irq (vector 0x31). Issue an extra EOI to clear ISR.
	 */
	for (i = APIC_ISR_NR - 1; i >= 0; i--) {
		value = apic_read(APIC_ISR + i*0x10);
		for (j = 31; j >= 0; j--) {
			if (value & (1<<j))
				ack_APIC_irq();
		}
	}

	/*
	 * Now that we are all set up, enable the APIC
	 */
	value = apic_read(APIC_SPIV);
	value &= ~APIC_VECTOR_MASK;
	/*
	 * Enable APIC
	 */
	value |= APIC_SPIV_APIC_ENABLED;

	/* We always use processor focus */

	/*
	 * Set spurious IRQ vector
	 */
	value |= SPURIOUS_APIC_VECTOR;
	apic_write(APIC_SPIV, value);

	/*
	 * Set up LVT0, LVT1:
	 *
	 * set up through-local-APIC on the BP's LINT0. This is not
	 * strictly necessary in pure symmetric-IO mode, but sometimes
	 * we delegate interrupts to the 8259A.
	 */
	/*
	 * TODO: set up through-local-APIC from through-I/O-APIC? --macro
	 */
	value = apic_read(APIC_LVT0) & APIC_LVT_MASKED;
	if (!smp_processor_id() && !value) {
		value = APIC_DM_EXTINT;
		apic_printk(APIC_VERBOSE, "enabled ExtINT on CPU#%d\n",
			    smp_processor_id());
	} else {
		value = APIC_DM_EXTINT | APIC_LVT_MASKED;
		apic_printk(APIC_VERBOSE, "masked ExtINT on CPU#%d\n",
			    smp_processor_id());
	}
	apic_write(APIC_LVT0, value);

	/*
	 * only the BP should see the LINT1 NMI signal, obviously.
	 */
	if (!smp_processor_id())
		value = APIC_DM_NMI;
	else
		value = APIC_DM_NMI | APIC_LVT_MASKED;
	apic_write(APIC_LVT1, value);
	preempt_enable();
}

static void __cpuinit lapic_setup_esr(void)
{
	unsigned maxlvt = lapic_get_maxlvt();

	apic_write(APIC_LVTERR, ERROR_APIC_VECTOR);
	/*
	 * spec says clear errors after enabling vector.
	 */
	if (maxlvt > 3)
		apic_write(APIC_ESR, 0);
}

void __cpuinit end_local_APIC_setup(void)
{
	lapic_setup_esr();
	setup_apic_nmi_watchdog(NULL);
	apic_pm_activate();
}

void check_x2apic(void)
{
	int msr, msr2;

	rdmsr(MSR_IA32_APICBASE, msr, msr2);

	if (msr & X2APIC_ENABLE) {
		printk("x2apic enabled by BIOS, switching to x2apic ops\n");
		x2apic_preenabled = x2apic = 1;
		apic_ops = &x2apic_ops;
	}
}

void enable_x2apic(void)
{
	int msr, msr2;

	rdmsr(MSR_IA32_APICBASE, msr, msr2);
	if (!(msr & X2APIC_ENABLE)) {
		printk("Enabling x2apic\n");
		wrmsr(MSR_IA32_APICBASE, msr | X2APIC_ENABLE, 0);
	}
}

void enable_IR_x2apic(void)
{
#ifdef CONFIG_INTR_REMAP
	int ret;
	unsigned long flags;

	if (!cpu_has_x2apic)
		return;

	if (!x2apic_preenabled && disable_x2apic) {
		printk(KERN_INFO
		       "Skipped enabling x2apic and Interrupt-remapping "
		       "because of nox2apic\n");
		return;
	}

	if (x2apic_preenabled && disable_x2apic)
		panic("Bios already enabled x2apic, can't enforce nox2apic");

	if (!x2apic_preenabled && skip_ioapic_setup) {
		printk(KERN_INFO
		       "Skipped enabling x2apic and Interrupt-remapping "
		       "because of skipping io-apic setup\n");
		return;
	}

	ret = dmar_table_init();
	if (ret) {
		printk(KERN_INFO
		       "dmar_table_init() failed with %d:\n", ret);

		if (x2apic_preenabled)
			panic("x2apic enabled by bios. But IR enabling failed");
		else
			printk(KERN_INFO
			       "Not enabling x2apic,Intr-remapping\n");
		return;
	}

	local_irq_save(flags);
	mask_8259A();
	save_mask_IO_APIC_setup();

	ret = enable_intr_remapping(1);

	if (ret && x2apic_preenabled) {
		local_irq_restore(flags);
		panic("x2apic enabled by bios. But IR enabling failed");
	}

	if (ret)
		goto end;

	if (!x2apic) {
		x2apic = 1;
		apic_ops = &x2apic_ops;
		enable_x2apic();
	}
end:
	if (ret)
		/*
		 * IR enabling failed
		 */
		restore_IO_APIC_setup();
	else
		reinit_intr_remapped_IO_APIC(x2apic_preenabled);

	unmask_8259A();
	local_irq_restore(flags);

	if (!ret) {
		if (!x2apic_preenabled)
			printk(KERN_INFO
			       "Enabled x2apic and interrupt-remapping\n");
		else
			printk(KERN_INFO
			       "Enabled Interrupt-remapping\n");
	} else
		printk(KERN_ERR
		       "Failed to enable Interrupt-remapping and x2apic\n");
#else
	if (!cpu_has_x2apic)
		return;

	if (x2apic_preenabled)
		panic("x2apic enabled prior OS handover,"
		      " enable CONFIG_INTR_REMAP");

	printk(KERN_INFO "Enable CONFIG_INTR_REMAP for enabling intr-remapping "
	       " and x2apic\n");
#endif

	return;
}

/*
 * Detect and enable local APICs on non-SMP boards.
 * Original code written by Keir Fraser.
 * On AMD64 we trust the BIOS - if it says no APIC it is likely
 * not correctly set up (usually the APIC timer won't work etc.)
 */
static int __init detect_init_APIC(void)
{
	if (!cpu_has_apic) {
		printk(KERN_INFO "No local APIC present\n");
		return -1;
	}

	mp_lapic_addr = APIC_DEFAULT_PHYS_BASE;
	boot_cpu_physical_apicid = 0;
	return 0;
}

void __init early_init_lapic_mapping(void)
{
	unsigned long phys_addr;

	/*
	 * If no local APIC can be found then go out
	 * : it means there is no mpatable and MADT
	 */
	if (!smp_found_config)
		return;

	phys_addr = mp_lapic_addr;

	set_fixmap_nocache(FIX_APIC_BASE, phys_addr);
	apic_printk(APIC_VERBOSE, "mapped APIC to %16lx (%16lx)\n",
		    APIC_BASE, phys_addr);

	/*
	 * Fetch the APIC ID of the BSP in case we have a
	 * default configuration (or the MP table is broken).
	 */
	boot_cpu_physical_apicid = read_apic_id();
}

/**
 * init_apic_mappings - initialize APIC mappings
 */
void __init init_apic_mappings(void)
{
	if (x2apic) {
		boot_cpu_physical_apicid = read_apic_id();
		return;
	}

	/*
	 * If no local APIC can be found then set up a fake all
	 * zeroes page to simulate the local APIC and another
	 * one for the IO-APIC.
	 */
	if (!smp_found_config && detect_init_APIC()) {
		apic_phys = (unsigned long) alloc_bootmem_pages(PAGE_SIZE);
		apic_phys = __pa(apic_phys);
	} else
		apic_phys = mp_lapic_addr;

	set_fixmap_nocache(FIX_APIC_BASE, apic_phys);
	apic_printk(APIC_VERBOSE, "mapped APIC to %16lx (%16lx)\n",
				APIC_BASE, apic_phys);

	/*
	 * Fetch the APIC ID of the BSP in case we have a
	 * default configuration (or the MP table is broken).
	 */
	boot_cpu_physical_apicid = read_apic_id();
}

/*
 * This initializes the IO-APIC and APIC hardware if this is
 * a UP kernel.
 */
int __init APIC_init_uniprocessor(void)
{
	if (disable_apic) {
		printk(KERN_INFO "Apic disabled\n");
		return -1;
	}
	if (!cpu_has_apic) {
		disable_apic = 1;
		printk(KERN_INFO "Apic disabled by BIOS\n");
		return -1;
	}

	enable_IR_x2apic();
	setup_apic_routing();

	verify_local_APIC();

	connect_bsp_APIC();

	physid_set_mask_of_physid(boot_cpu_physical_apicid, &phys_cpu_present_map);
	apic_write(APIC_ID, SET_APIC_ID(boot_cpu_physical_apicid));

	setup_local_APIC();

	/*
	 * Now enable IO-APICs, actually call clear_IO_APIC
	 * We need clear_IO_APIC before enabling vector on BP
	 */
	if (!skip_ioapic_setup && nr_ioapics)
		enable_IO_APIC();

	if (!smp_found_config || skip_ioapic_setup || !nr_ioapics)
		localise_nmi_watchdog();
	end_local_APIC_setup();

	if (smp_found_config && !skip_ioapic_setup && nr_ioapics)
		setup_IO_APIC();
	else
		nr_ioapics = 0;
	setup_boot_APIC_clock();
	check_nmi_watchdog();
	return 0;
}

/*
 * Local APIC interrupts
 */

/*
 * This interrupt should _never_ happen with our APIC/SMP architecture
 */
asmlinkage void smp_spurious_interrupt(void)
{
	unsigned int v;
	exit_idle();
	irq_enter();
	/*
	 * Check if this really is a spurious interrupt and ACK it
	 * if it is a vectored one.  Just in case...
	 * Spurious interrupts should not be ACKed.
	 */
	v = apic_read(APIC_ISR + ((SPURIOUS_APIC_VECTOR & ~0x1f) >> 1));
	if (v & (1 << (SPURIOUS_APIC_VECTOR & 0x1f)))
		ack_APIC_irq();

	add_pda(irq_spurious_count, 1);
	irq_exit();
}

/*
 * This interrupt should never happen with our APIC/SMP architecture
 */
asmlinkage void smp_error_interrupt(void)
{
	unsigned int v, v1;

	exit_idle();
	irq_enter();
	/* First tickle the hardware, only then report what went on. -- REW */
	v = apic_read(APIC_ESR);
	apic_write(APIC_ESR, 0);
	v1 = apic_read(APIC_ESR);
	ack_APIC_irq();
	atomic_inc(&irq_err_count);

	/* Here is what the APIC error bits mean:
	   0: Send CS error
	   1: Receive CS error
	   2: Send accept error
	   3: Receive accept error
	   4: Reserved
	   5: Send illegal vector
	   6: Received illegal vector
	   7: Illegal register address
	*/
	printk(KERN_DEBUG "APIC error on CPU%d: %02x(%02x)\n",
		smp_processor_id(), v , v1);
	irq_exit();
}

/**
 *  * connect_bsp_APIC - attach the APIC to the interrupt system
 *   */
void __init connect_bsp_APIC(void)
{
	enable_apic_mode();
}

/**
 * disconnect_bsp_APIC - detach the APIC from the interrupt system
 * @virt_wire_setup:	indicates, whether virtual wire mode is selected
 *
 * Virtual wire mode is necessary to deliver legacy interrupts even when the
 * APIC is disabled.
 */
void disconnect_bsp_APIC(int virt_wire_setup)
{
	/* Go back to Virtual Wire compatibility mode */
	unsigned long value;

	/* For the spurious interrupt use vector F, and enable it */
	value = apic_read(APIC_SPIV);
	value &= ~APIC_VECTOR_MASK;
	value |= APIC_SPIV_APIC_ENABLED;
	value |= 0xf;
	apic_write(APIC_SPIV, value);

	if (!virt_wire_setup) {
		/*
		 * For LVT0 make it edge triggered, active high,
		 * external and enabled
		 */
		value = apic_read(APIC_LVT0);
		value &= ~(APIC_MODE_MASK | APIC_SEND_PENDING |
			APIC_INPUT_POLARITY | APIC_LVT_REMOTE_IRR |
			APIC_LVT_LEVEL_TRIGGER | APIC_LVT_MASKED);
		value |= APIC_LVT_REMOTE_IRR | APIC_SEND_PENDING;
		value = SET_APIC_DELIVERY_MODE(value, APIC_MODE_EXTINT);
		apic_write(APIC_LVT0, value);
	} else {
		/* Disable LVT0 */
		apic_write(APIC_LVT0, APIC_LVT_MASKED);
	}

	/* For LVT1 make it edge triggered, active high, nmi and enabled */
	value = apic_read(APIC_LVT1);
	value &= ~(APIC_MODE_MASK | APIC_SEND_PENDING |
			APIC_INPUT_POLARITY | APIC_LVT_REMOTE_IRR |
			APIC_LVT_LEVEL_TRIGGER | APIC_LVT_MASKED);
	value |= APIC_LVT_REMOTE_IRR | APIC_SEND_PENDING;
	value = SET_APIC_DELIVERY_MODE(value, APIC_MODE_NMI);
	apic_write(APIC_LVT1, value);
}

void __cpuinit generic_processor_info(int apicid, int version)
{
	int cpu;
	cpumask_t tmp_map;

	if (num_processors >= NR_CPUS) {
		printk(KERN_WARNING "WARNING: NR_CPUS limit of %i reached."
		       " Processor ignored.\n", NR_CPUS);
		return;
	}

	if (num_processors >= maxcpus) {
		printk(KERN_WARNING "WARNING: maxcpus limit of %i reached."
		       " Processor ignored.\n", maxcpus);
		return;
	}

	num_processors++;
	cpus_complement(tmp_map, cpu_present_map);
	cpu = first_cpu(tmp_map);

	physid_set(apicid, phys_cpu_present_map);
	if (apicid == boot_cpu_physical_apicid) {
		/*
		 * x86_bios_cpu_apicid is required to have processors listed
		 * in same order as logical cpu numbers. Hence the first
		 * entry is BSP, and so on.
		 */
		cpu = 0;
	}
	if (apicid > max_physical_apicid)
		max_physical_apicid = apicid;

	/* are we being called early in kernel startup? */
	if (early_per_cpu_ptr(x86_cpu_to_apicid)) {
		u16 *cpu_to_apicid = early_per_cpu_ptr(x86_cpu_to_apicid);
		u16 *bios_cpu_apicid = early_per_cpu_ptr(x86_bios_cpu_apicid);

		cpu_to_apicid[cpu] = apicid;
		bios_cpu_apicid[cpu] = apicid;
	} else {
		per_cpu(x86_cpu_to_apicid, cpu) = apicid;
		per_cpu(x86_bios_cpu_apicid, cpu) = apicid;
	}

	cpu_set(cpu, cpu_possible_map);
	cpu_set(cpu, cpu_present_map);
}

int hard_smp_processor_id(void)
{
	return read_apic_id();
}

/*
 * Power management
 */
#ifdef CONFIG_PM

static struct {
	/*
	 * 'active' is true if the local APIC was enabled by us and
	 * not the BIOS; this signifies that we are also responsible
	 * for disabling it before entering apm/acpi suspend
	 */
	int active;
	/* r/w apic fields */
	unsigned int apic_id;
	unsigned int apic_taskpri;
	unsigned int apic_ldr;
	unsigned int apic_dfr;
	unsigned int apic_spiv;
	unsigned int apic_lvtt;
	unsigned int apic_lvtpc;
	unsigned int apic_lvt0;
	unsigned int apic_lvt1;
	unsigned int apic_lvterr;
	unsigned int apic_tmict;
	unsigned int apic_tdcr;
	unsigned int apic_thmr;
} apic_pm_state;

static int lapic_suspend(struct sys_device *dev, pm_message_t state)
{
	unsigned long flags;
	int maxlvt;

	if (!apic_pm_state.active)
		return 0;

	maxlvt = lapic_get_maxlvt();

	apic_pm_state.apic_id = apic_read(APIC_ID);
	apic_pm_state.apic_taskpri = apic_read(APIC_TASKPRI);
	apic_pm_state.apic_ldr = apic_read(APIC_LDR);
	apic_pm_state.apic_dfr = apic_read(APIC_DFR);
	apic_pm_state.apic_spiv = apic_read(APIC_SPIV);
	apic_pm_state.apic_lvtt = apic_read(APIC_LVTT);
	if (maxlvt >= 4)
		apic_pm_state.apic_lvtpc = apic_read(APIC_LVTPC);
	apic_pm_state.apic_lvt0 = apic_read(APIC_LVT0);
	apic_pm_state.apic_lvt1 = apic_read(APIC_LVT1);
	apic_pm_state.apic_lvterr = apic_read(APIC_LVTERR);
	apic_pm_state.apic_tmict = apic_read(APIC_TMICT);
	apic_pm_state.apic_tdcr = apic_read(APIC_TDCR);
#if defined(CONFIG_X86_MCE_P4THERMAL) || defined(CONFIG_X86_MCE_INTEL)
	if (maxlvt >= 5)
		apic_pm_state.apic_thmr = apic_read(APIC_LVTTHMR);
#endif

	local_irq_save(flags);
	disable_local_APIC();
	local_irq_restore(flags);
	return 0;
}

static int lapic_resume(struct sys_device *dev)
{
	unsigned int l, h;
	unsigned long flags;
	int maxlvt;

	if (!apic_pm_state.active)
		return 0;

	maxlvt = lapic_get_maxlvt();

	local_irq_save(flags);

#ifdef CONFIG_X86_64
	if (x2apic)
		enable_x2apic();
	else
#endif
	{
		/*
		 * Make sure the APICBASE points to the right address
		 *
		 * FIXME! This will be wrong if we ever support suspend on
		 * SMP! We'll need to do this as part of the CPU restore!
		 */
		rdmsr(MSR_IA32_APICBASE, l, h);
		l &= ~MSR_IA32_APICBASE_BASE;
		l |= MSR_IA32_APICBASE_ENABLE | mp_lapic_addr;
		wrmsr(MSR_IA32_APICBASE, l, h);
	}

	apic_write(APIC_LVTERR, ERROR_APIC_VECTOR | APIC_LVT_MASKED);
	apic_write(APIC_ID, apic_pm_state.apic_id);
	apic_write(APIC_DFR, apic_pm_state.apic_dfr);
	apic_write(APIC_LDR, apic_pm_state.apic_ldr);
	apic_write(APIC_TASKPRI, apic_pm_state.apic_taskpri);
	apic_write(APIC_SPIV, apic_pm_state.apic_spiv);
	apic_write(APIC_LVT0, apic_pm_state.apic_lvt0);
	apic_write(APIC_LVT1, apic_pm_state.apic_lvt1);
#if defined(CONFIG_X86_MCE_P4THERMAL) || defined(CONFIG_X86_MCE_INTEL)
	if (maxlvt >= 5)
		apic_write(APIC_LVTTHMR, apic_pm_state.apic_thmr);
#endif
	if (maxlvt >= 4)
		apic_write(APIC_LVTPC, apic_pm_state.apic_lvtpc);
	apic_write(APIC_LVTT, apic_pm_state.apic_lvtt);
	apic_write(APIC_TDCR, apic_pm_state.apic_tdcr);
	apic_write(APIC_TMICT, apic_pm_state.apic_tmict);
	apic_write(APIC_ESR, 0);
	apic_read(APIC_ESR);
	apic_write(APIC_LVTERR, apic_pm_state.apic_lvterr);
	apic_write(APIC_ESR, 0);
	apic_read(APIC_ESR);

	local_irq_restore(flags);

	return 0;
}

/*
 * This device has no shutdown method - fully functioning local APICs
 * are needed on every CPU up until machine_halt/restart/poweroff.
 */

static struct sysdev_class lapic_sysclass = {
	.name		= "lapic",
	.resume		= lapic_resume,
	.suspend	= lapic_suspend,
};

static struct sys_device device_lapic = {
	.id	= 0,
	.cls	= &lapic_sysclass,
};

static void __cpuinit apic_pm_activate(void)
{
	apic_pm_state.active = 1;
}

static int __init init_lapic_sysfs(void)
{
	int error;

	if (!cpu_has_apic)
		return 0;
	/* XXX: remove suspend/resume procs if !apic_pm_state.active? */

	error = sysdev_class_register(&lapic_sysclass);
	if (!error)
		error = sysdev_register(&device_lapic);
	return error;
}
device_initcall(init_lapic_sysfs);

#else	/* CONFIG_PM */

static void apic_pm_activate(void) { }

#endif	/* CONFIG_PM */

/*
 * apic_is_clustered_box() -- Check if we can expect good TSC
 *
 * Thus far, the major user of this is IBM's Summit2 series:
 *
 * Clustered boxes may have unsynced TSC problems if they are
 * multi-chassis. Use available data to take a good guess.
 * If in doubt, go HPET.
 */
__cpuinit int apic_is_clustered_box(void)
{
	int i, clusters, zeros;
	unsigned id;
	u16 *bios_cpu_apicid;
	DECLARE_BITMAP(clustermap, NUM_APIC_CLUSTERS);

	/*
	 * there is not this kind of box with AMD CPU yet.
	 * Some AMD box with quadcore cpu and 8 sockets apicid
	 * will be [4, 0x23] or [8, 0x27] could be thought to
	 * vsmp box still need checking...
	 */
	if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && !is_vsmp_box())
		return 0;

	bios_cpu_apicid = early_per_cpu_ptr(x86_bios_cpu_apicid);
	bitmap_zero(clustermap, NUM_APIC_CLUSTERS);

	for (i = 0; i < NR_CPUS; i++) {
		/* are we being called early in kernel startup? */
		if (bios_cpu_apicid) {
			id = bios_cpu_apicid[i];
		}
		else if (i < nr_cpu_ids) {
			if (cpu_present(i))
				id = per_cpu(x86_bios_cpu_apicid, i);
			else
				continue;
		}
		else
			break;

		if (id != BAD_APICID)
			__set_bit(APIC_CLUSTERID(id), clustermap);
	}

	/* Problem:  Partially populated chassis may not have CPUs in some of
	 * the APIC clusters they have been allocated.  Only present CPUs have
	 * x86_bios_cpu_apicid entries, thus causing zeroes in the bitmap.
	 * Since clusters are allocated sequentially, count zeros only if
	 * they are bounded by ones.
	 */
	clusters = 0;
	zeros = 0;
	for (i = 0; i < NUM_APIC_CLUSTERS; i++) {
		if (test_bit(i, clustermap)) {
			clusters += 1 + zeros;
			zeros = 0;
		} else
			++zeros;
	}

	/* ScaleMP vSMPowered boxes have one cluster per board and TSCs are
	 * not guaranteed to be synced between boards
	 */
	if (is_vsmp_box() && clusters > 1)
		return 1;

	/*
	 * If clusters > 2, then should be multi-chassis.
	 * May have to revisit this when multi-core + hyperthreaded CPUs come
	 * out, but AFAIK this will work even for them.
	 */
	return (clusters > 2);
}

static __init int setup_nox2apic(char *str)
{
	disable_x2apic = 1;
	clear_cpu_cap(&boot_cpu_data, X86_FEATURE_X2APIC);
	return 0;
}
early_param("nox2apic", setup_nox2apic);


/*
 * APIC command line parameters
 */
static int __init apic_set_verbosity(char *str)
{
	if (str == NULL)  {
		skip_ioapic_setup = 0;
		ioapic_force = 1;
		return 0;
	}
	if (strcmp("debug", str) == 0)
		apic_verbosity = APIC_DEBUG;
	else if (strcmp("verbose", str) == 0)
		apic_verbosity = APIC_VERBOSE;
	else {
		printk(KERN_WARNING "APIC Verbosity level %s not recognised"
				" use apic=verbose or apic=debug\n", str);
		return -EINVAL;
	}

	return 0;
}
early_param("apic", apic_set_verbosity);

static __init int setup_disableapic(char *str)
{
	disable_apic = 1;
	setup_clear_cpu_cap(X86_FEATURE_APIC);
	return 0;
}
early_param("disableapic", setup_disableapic);

/* same as disableapic, for compatibility */
static __init int setup_nolapic(char *str)
{
	return setup_disableapic(str);
}
early_param("nolapic", setup_nolapic);

static int __init parse_lapic_timer_c2_ok(char *arg)
{
	local_apic_timer_c2_ok = 1;
	return 0;
}
early_param("lapic_timer_c2_ok", parse_lapic_timer_c2_ok);

static int __init parse_disable_apic_timer(char *arg)
{
	disable_apic_timer = 1;
	return 0;
}
early_param("noapictimer", parse_disable_apic_timer);

static int __init parse_nolapic_timer(char *arg)
{
	disable_apic_timer = 1;
	return 0;
}
early_param("nolapic_timer", parse_nolapic_timer);

static __init int setup_apicpmtimer(char *s)
{
	apic_calibrate_pmtmr = 1;
	notsc_setup(NULL);
	return 0;
}
__setup("apicpmtimer", setup_apicpmtimer);

static int __init lapic_insert_resource(void)
{
	if (!apic_phys)
		return -1;

	/* Put local APIC into the resource map. */
	lapic_resource.start = apic_phys;
	lapic_resource.end = lapic_resource.start + PAGE_SIZE - 1;
	insert_resource(&iomem_resource, &lapic_resource);

	return 0;
}

/*
 * need call insert after e820_reserve_resources()
 * that is using request_resource
 */
late_initcall(lapic_insert_resource);