perf_events: Update Intel extra regs shared constraints management

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / arch / x86 / kernel / cpu / perf_event.c

/*
 * Performance events x86 architecture code
 *
 *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
 *  Copyright (C) 2008-2009 Red Hat, Inc., Ingo Molnar
 *  Copyright (C) 2009 Jaswinder Singh Rajput
 *  Copyright (C) 2009 Advanced Micro Devices, Inc., Robert Richter
 *  Copyright (C) 2008-2009 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
 *  Copyright (C) 2009 Intel Corporation, <markus.t.metzger@intel.com>
 *  Copyright (C) 2009 Google, Inc., Stephane Eranian
 *
 *  For licencing details see kernel-base/COPYING
 */

#include <linux/perf_event.h>
#include <linux/capability.h>
#include <linux/notifier.h>
#include <linux/hardirq.h>
#include <linux/kprobes.h>
#include <linux/module.h>
#include <linux/kdebug.h>
#include <linux/sched.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/cpu.h>
#include <linux/bitops.h>

#include <asm/apic.h>
#include <asm/stacktrace.h>
#include <asm/nmi.h>
#include <asm/compat.h>
#include <asm/smp.h>
#include <asm/alternative.h>

#if 0
#undef wrmsrl
#define wrmsrl(msr, val)                                        \
do {                                                            \
        trace_printk("wrmsrl(%lx, %lx)\n", (unsigned long)(msr),\
                        (unsigned long)(val));                  \
        native_write_msr((msr), (u32)((u64)(val)),              \
                        (u32)((u64)(val) >> 32));               \
} while (0)
#endif

/*
 *          |   NHM/WSM    |      SNB     |
 * register -------------------------------
 *          |  HT  | no HT |  HT  | no HT |
 *-----------------------------------------
 * offcore  | core | core  | cpu  | core  |
 * lbr_sel  | core | core  | cpu  | core  |
 * ld_lat   | cpu  | core  | cpu  | core  |
 *-----------------------------------------
 *
 * Given that there is a small number of shared regs,
 * we can pre-allocate their slot in the per-cpu
 * per-core reg tables.
 */
enum extra_reg_type {
        EXTRA_REG_NONE  = -1,   /* not used */

        EXTRA_REG_RSP_0 = 0,    /* offcore_response_0 */
        EXTRA_REG_RSP_1 = 1,    /* offcore_response_1 */

        EXTRA_REG_MAX           /* number of entries needed */
};

/*
 * best effort, GUP based copy_from_user() that assumes IRQ or NMI context
 */
static unsigned long
copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
{
        unsigned long offset, addr = (unsigned long)from;
        unsigned long size, len = 0;
        struct page *page;
        void *map;
        int ret;

        do {
                ret = __get_user_pages_fast(addr, 1, 0, &page);
                if (!ret)
                        break;

                offset = addr & (PAGE_SIZE - 1);
                size = min(PAGE_SIZE - offset, n - len);

                map = kmap_atomic(page);
                memcpy(to, map+offset, size);
                kunmap_atomic(map);
                put_page(page);

                len  += size;
                to   += size;
                addr += size;

        } while (len < n);

        return len;
}

struct event_constraint {
        union {
                unsigned long   idxmsk[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
                u64             idxmsk64;
        };
        u64     code;
        u64     cmask;
        int     weight;
};

struct amd_nb {
        int nb_id;  /* NorthBridge id */
        int refcnt; /* reference count */
        struct perf_event *owners[X86_PMC_IDX_MAX];
        struct event_constraint event_constraints[X86_PMC_IDX_MAX];
};

struct intel_percore;

#define MAX_LBR_ENTRIES         16

struct cpu_hw_events {
        /*
         * Generic x86 PMC bits
         */
        struct perf_event       *events[X86_PMC_IDX_MAX]; /* in counter order */
        unsigned long           active_mask[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
        unsigned long           running[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
        int                     enabled;

        int                     n_events;
        int                     n_added;
        int                     n_txn;
        int                     assign[X86_PMC_IDX_MAX]; /* event to counter assignment */
        u64                     tags[X86_PMC_IDX_MAX];
        struct perf_event       *event_list[X86_PMC_IDX_MAX]; /* in enabled order */

        unsigned int            group_flag;

        /*
         * Intel DebugStore bits
         */
        struct debug_store      *ds;
        u64                     pebs_enabled;

        /*
         * Intel LBR bits
         */
        int                             lbr_users;
        void                            *lbr_context;
        struct perf_branch_stack        lbr_stack;
        struct perf_branch_entry        lbr_entries[MAX_LBR_ENTRIES];

        /*
         * manage shared (per-core, per-cpu) registers
         * used on Intel NHM/WSM/SNB
         */
        struct intel_shared_regs        *shared_regs;

        /*
         * AMD specific bits
         */
        struct amd_nb           *amd_nb;
};

#define __EVENT_CONSTRAINT(c, n, m, w) {\
        { .idxmsk64 = (n) },            \
        .code = (c),                    \
        .cmask = (m),                   \
        .weight = (w),                  \
}

#define EVENT_CONSTRAINT(c, n, m)       \
        __EVENT_CONSTRAINT(c, n, m, HWEIGHT(n))

/*
 * Constraint on the Event code.
 */
#define INTEL_EVENT_CONSTRAINT(c, n)    \
        EVENT_CONSTRAINT(c, n, ARCH_PERFMON_EVENTSEL_EVENT)

/*
 * Constraint on the Event code + UMask + fixed-mask
 *
 * filter mask to validate fixed counter events.
 * the following filters disqualify for fixed counters:
 *  - inv
 *  - edge
 *  - cnt-mask
 *  The other filters are supported by fixed counters.
 *  The any-thread option is supported starting with v3.
 */
#define FIXED_EVENT_CONSTRAINT(c, n)    \
        EVENT_CONSTRAINT(c, (1ULL << (32+n)), X86_RAW_EVENT_MASK)

/*
 * Constraint on the Event code + UMask
 */
#define INTEL_UEVENT_CONSTRAINT(c, n)   \
        EVENT_CONSTRAINT(c, n, INTEL_ARCH_EVENT_MASK)

#define EVENT_CONSTRAINT_END            \
        EVENT_CONSTRAINT(0, 0, 0)

#define for_each_event_constraint(e, c) \
        for ((e) = (c); (e)->weight; (e)++)

/*
 * Per register state.
 */
struct er_account {
        raw_spinlock_t          lock;   /* per-core: protect structure */
        u64                     config; /* extra MSR config */
        u64                     reg;    /* extra MSR number */
        atomic_t                ref;    /* reference count */
};

/*
 * Extra registers for specific events.
 *
 * Some events need large masks and require external MSRs.
 * Those extra MSRs end up being shared for all events on
 * a PMU and sometimes between PMU of sibling HT threads.
 * In either case, the kernel needs to handle conflicting
 * accesses to those extra, shared, regs. The data structure
 * to manage those registers is stored in cpu_hw_event.
 */
struct extra_reg {
        unsigned int            event;
        unsigned int            msr;
        u64                     config_mask;
        u64                     valid_mask;
        int                     idx;  /* per_xxx->regs[] reg index */
};

#define EVENT_EXTRA_REG(e, ms, m, vm, i) {      \
        .event = (e),           \
        .msr = (ms),            \
        .config_mask = (m),     \
        .valid_mask = (vm),     \
        .idx = EXTRA_REG_##i    \
        }

#define INTEL_EVENT_EXTRA_REG(event, msr, vm, idx)      \
        EVENT_EXTRA_REG(event, msr, ARCH_PERFMON_EVENTSEL_EVENT, vm, idx)

#define EVENT_EXTRA_END EVENT_EXTRA_REG(0, 0, 0, 0, RSP_0)

union perf_capabilities {
        struct {
                u64     lbr_format    : 6;
                u64     pebs_trap     : 1;
                u64     pebs_arch_reg : 1;
                u64     pebs_format   : 4;
                u64     smm_freeze    : 1;
        };
        u64     capabilities;
};

/*
 * struct x86_pmu - generic x86 pmu
 */
struct x86_pmu {
        /*
         * Generic x86 PMC bits
         */
        const char      *name;
        int             version;
        int             (*handle_irq)(struct pt_regs *);
        void            (*disable_all)(void);
        void            (*enable_all)(int added);
        void            (*enable)(struct perf_event *);
        void            (*disable)(struct perf_event *);
        void            (*hw_watchdog_set_attr)(struct perf_event_attr *attr);
        int             (*hw_config)(struct perf_event *event);
        int             (*schedule_events)(struct cpu_hw_events *cpuc, int n, int *assign);
        unsigned        eventsel;
        unsigned        perfctr;
        u64             (*event_map)(int);
        int             max_events;
        int             num_counters;
        int             num_counters_fixed;
        int             cntval_bits;
        u64             cntval_mask;
        int             apic;
        u64             max_period;
        struct event_constraint *
                        (*get_event_constraints)(struct cpu_hw_events *cpuc,
                                                 struct perf_event *event);

        void            (*put_event_constraints)(struct cpu_hw_events *cpuc,
                                                 struct perf_event *event);
        struct event_constraint *event_constraints;
        void            (*quirks)(void);
        int             perfctr_second_write;

        int             (*cpu_prepare)(int cpu);
        void            (*cpu_starting)(int cpu);
        void            (*cpu_dying)(int cpu);
        void            (*cpu_dead)(int cpu);

        /*
         * Intel Arch Perfmon v2+
         */
        u64                     intel_ctrl;
        union perf_capabilities intel_cap;

        /*
         * Intel DebugStore bits
         */
        int             bts, pebs;
        int             bts_active, pebs_active;
        int             pebs_record_size;
        void            (*drain_pebs)(struct pt_regs *regs);
        struct event_constraint *pebs_constraints;

        /*
         * Intel LBR
         */
        unsigned long   lbr_tos, lbr_from, lbr_to; /* MSR base regs       */
        int             lbr_nr;                    /* hardware stack size */

        /*
         * Extra registers for events
         */
        struct extra_reg *extra_regs;
};

static struct x86_pmu x86_pmu __read_mostly;

static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events) = {
        .enabled = 1,
};

static int x86_perf_event_set_period(struct perf_event *event);

/*
 * Generalized hw caching related hw_event table, filled
 * in on a per model basis. A value of 0 means
 * 'not supported', -1 means 'hw_event makes no sense on
 * this CPU', any other value means the raw hw_event
 * ID.
 */

#define C(x) PERF_COUNT_HW_CACHE_##x

static u64 __read_mostly hw_cache_event_ids
                                [PERF_COUNT_HW_CACHE_MAX]
                                [PERF_COUNT_HW_CACHE_OP_MAX]
                                [PERF_COUNT_HW_CACHE_RESULT_MAX];
static u64 __read_mostly hw_cache_extra_regs
                                [PERF_COUNT_HW_CACHE_MAX]
                                [PERF_COUNT_HW_CACHE_OP_MAX]
                                [PERF_COUNT_HW_CACHE_RESULT_MAX];

void hw_nmi_watchdog_set_attr(struct perf_event_attr *wd_attr)
{
        if (x86_pmu.hw_watchdog_set_attr)
                x86_pmu.hw_watchdog_set_attr(wd_attr);
}

/*
 * Propagate event elapsed time into the generic event.
 * Can only be executed on the CPU where the event is active.
 * Returns the delta events processed.
 */
static u64
x86_perf_event_update(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;
        int shift = 64 - x86_pmu.cntval_bits;
        u64 prev_raw_count, new_raw_count;
        int idx = hwc->idx;
        s64 delta;

        if (idx == X86_PMC_IDX_FIXED_BTS)
                return 0;

        /*
         * Careful: an NMI might modify the previous event value.
         *
         * Our tactic to handle this is to first atomically read and
         * exchange a new raw count - then add that new-prev delta
         * count to the generic event atomically:
         */
again:
        prev_raw_count = local64_read(&hwc->prev_count);
        rdmsrl(hwc->event_base, new_raw_count);

        if (local64_cmpxchg(&hwc->prev_count, prev_raw_count,
                                        new_raw_count) != prev_raw_count)
                goto again;

        /*
         * Now we have the new raw value and have updated the prev
         * timestamp already. We can now calculate the elapsed delta
         * (event-)time and add that to the generic event.
         *
         * Careful, not all hw sign-extends above the physical width
         * of the count.
         */
        delta = (new_raw_count << shift) - (prev_raw_count << shift);
        delta >>= shift;

        local64_add(delta, &event->count);
        local64_sub(delta, &hwc->period_left);

        return new_raw_count;
}

static inline int x86_pmu_addr_offset(int index)
{
        int offset;

        /* offset = X86_FEATURE_PERFCTR_CORE ? index << 1 : index */
        alternative_io(ASM_NOP2,
                       "shll $1, %%eax",
                       X86_FEATURE_PERFCTR_CORE,
                       "=a" (offset),
                       "a"  (index));

        return offset;
}

static inline unsigned int x86_pmu_config_addr(int index)
{
        return x86_pmu.eventsel + x86_pmu_addr_offset(index);
}

static inline unsigned int x86_pmu_event_addr(int index)
{
        return x86_pmu.perfctr + x86_pmu_addr_offset(index);
}

/*
 * Find and validate any extra registers to set up.
 */
static int x86_pmu_extra_regs(u64 config, struct perf_event *event)
{
        struct hw_perf_event_extra *reg;
        struct extra_reg *er;

        reg = &event->hw.extra_reg;

        if (!x86_pmu.extra_regs)
                return 0;

        for (er = x86_pmu.extra_regs; er->msr; er++) {
                if (er->event != (config & er->config_mask))
                        continue;
                if (event->attr.config1 & ~er->valid_mask)
                        return -EINVAL;

                reg->idx = er->idx;
                reg->config = event->attr.config1;
                reg->reg = er->msr;
                break;
        }
        return 0;
}

static atomic_t active_events;
static DEFINE_MUTEX(pmc_reserve_mutex);

#ifdef CONFIG_X86_LOCAL_APIC

static bool reserve_pmc_hardware(void)
{
        int i;

        for (i = 0; i < x86_pmu.num_counters; i++) {
                if (!reserve_perfctr_nmi(x86_pmu_event_addr(i)))
                        goto perfctr_fail;
        }

        for (i = 0; i < x86_pmu.num_counters; i++) {
                if (!reserve_evntsel_nmi(x86_pmu_config_addr(i)))
                        goto eventsel_fail;
        }

        return true;

eventsel_fail:
        for (i--; i >= 0; i--)
                release_evntsel_nmi(x86_pmu_config_addr(i));

        i = x86_pmu.num_counters;

perfctr_fail:
        for (i--; i >= 0; i--)
                release_perfctr_nmi(x86_pmu_event_addr(i));

        return false;
}

static void release_pmc_hardware(void)
{
        int i;

        for (i = 0; i < x86_pmu.num_counters; i++) {
                release_perfctr_nmi(x86_pmu_event_addr(i));
                release_evntsel_nmi(x86_pmu_config_addr(i));
        }
}

#else

static bool reserve_pmc_hardware(void) { return true; }
static void release_pmc_hardware(void) {}

#endif

static bool check_hw_exists(void)
{
        u64 val, val_new = 0;
        int i, reg, ret = 0;

        /*
         * Check to see if the BIOS enabled any of the counters, if so
         * complain and bail.
         */
        for (i = 0; i < x86_pmu.num_counters; i++) {
                reg = x86_pmu_config_addr(i);
                ret = rdmsrl_safe(reg, &val);
                if (ret)
                        goto msr_fail;
                if (val & ARCH_PERFMON_EVENTSEL_ENABLE)
                        goto bios_fail;
        }

        if (x86_pmu.num_counters_fixed) {
                reg = MSR_ARCH_PERFMON_FIXED_CTR_CTRL;
                ret = rdmsrl_safe(reg, &val);
                if (ret)
                        goto msr_fail;
                for (i = 0; i < x86_pmu.num_counters_fixed; i++) {
                        if (val & (0x03 << i*4))
                                goto bios_fail;
                }
        }

        /*
         * Now write a value and read it back to see if it matches,
         * this is needed to detect certain hardware emulators (qemu/kvm)
         * that don't trap on the MSR access and always return 0s.
         */
        val = 0xabcdUL;
        ret = checking_wrmsrl(x86_pmu_event_addr(0), val);
        ret |= rdmsrl_safe(x86_pmu_event_addr(0), &val_new);
        if (ret || val != val_new)
                goto msr_fail;

        return true;

bios_fail:
        /*
         * We still allow the PMU driver to operate:
         */
        printk(KERN_CONT "Broken BIOS detected, complain to your hardware vendor.\n");
        printk(KERN_ERR FW_BUG "the BIOS has corrupted hw-PMU resources (MSR %x is %Lx)\n", reg, val);

        return true;

msr_fail:
        printk(KERN_CONT "Broken PMU hardware detected, using software events only.\n");

        return false;
}

static void reserve_ds_buffers(void);
static void release_ds_buffers(void);

static void hw_perf_event_destroy(struct perf_event *event)
{
        if (atomic_dec_and_mutex_lock(&active_events, &pmc_reserve_mutex)) {
                release_pmc_hardware();
                release_ds_buffers();
                mutex_unlock(&pmc_reserve_mutex);
        }
}

static inline int x86_pmu_initialized(void)
{
        return x86_pmu.handle_irq != NULL;
}

static inline int
set_ext_hw_attr(struct hw_perf_event *hwc, struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        unsigned int cache_type, cache_op, cache_result;
        u64 config, val;

        config = attr->config;

        cache_type = (config >>  0) & 0xff;
        if (cache_type >= PERF_COUNT_HW_CACHE_MAX)
                return -EINVAL;

        cache_op = (config >>  8) & 0xff;
        if (cache_op >= PERF_COUNT_HW_CACHE_OP_MAX)
                return -EINVAL;

        cache_result = (config >> 16) & 0xff;
        if (cache_result >= PERF_COUNT_HW_CACHE_RESULT_MAX)
                return -EINVAL;

        val = hw_cache_event_ids[cache_type][cache_op][cache_result];

        if (val == 0)
                return -ENOENT;

        if (val == -1)
                return -EINVAL;

        hwc->config |= val;
        attr->config1 = hw_cache_extra_regs[cache_type][cache_op][cache_result];
        return x86_pmu_extra_regs(val, event);
}

static int x86_setup_perfctr(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        struct hw_perf_event *hwc = &event->hw;
        u64 config;

        if (!is_sampling_event(event)) {
                hwc->sample_period = x86_pmu.max_period;
                hwc->last_period = hwc->sample_period;
                local64_set(&hwc->period_left, hwc->sample_period);
        } else {
                /*
                 * If we have a PMU initialized but no APIC
                 * interrupts, we cannot sample hardware
                 * events (user-space has to fall back and
                 * sample via a hrtimer based software event):
                 */
                if (!x86_pmu.apic)
                        return -EOPNOTSUPP;
        }

        /*
         * Do not allow config1 (extended registers) to propagate,
         * there's no sane user-space generalization yet:
         */
        if (attr->type == PERF_TYPE_RAW)
                return 0;

        if (attr->type == PERF_TYPE_HW_CACHE)
                return set_ext_hw_attr(hwc, event);

        if (attr->config >= x86_pmu.max_events)
                return -EINVAL;

        /*
         * The generic map:
         */
        config = x86_pmu.event_map(attr->config);

        if (config == 0)
                return -ENOENT;

        if (config == -1LL)
                return -EINVAL;

        /*
         * Branch tracing:
         */
        if (attr->config == PERF_COUNT_HW_BRANCH_INSTRUCTIONS &&
            !attr->freq && hwc->sample_period == 1) {
                /* BTS is not supported by this architecture. */
                if (!x86_pmu.bts_active)
                        return -EOPNOTSUPP;

                /* BTS is currently only allowed for user-mode. */
                if (!attr->exclude_kernel)
                        return -EOPNOTSUPP;
        }

        hwc->config |= config;

        return 0;
}

static int x86_pmu_hw_config(struct perf_event *event)
{
        if (event->attr.precise_ip) {
                int precise = 0;

                /* Support for constant skid */
                if (x86_pmu.pebs_active) {
                        precise++;

                        /* Support for IP fixup */
                        if (x86_pmu.lbr_nr)
                                precise++;
                }

                if (event->attr.precise_ip > precise)
                        return -EOPNOTSUPP;
        }

        /*
         * Generate PMC IRQs:
         * (keep 'enabled' bit clear for now)
         */
        event->hw.config = ARCH_PERFMON_EVENTSEL_INT;

        /*
         * Count user and OS events unless requested not to
         */
        if (!event->attr.exclude_user)
                event->hw.config |= ARCH_PERFMON_EVENTSEL_USR;
        if (!event->attr.exclude_kernel)
                event->hw.config |= ARCH_PERFMON_EVENTSEL_OS;

        if (event->attr.type == PERF_TYPE_RAW)
                event->hw.config |= event->attr.config & X86_RAW_EVENT_MASK;

        return x86_setup_perfctr(event);
}

/*
 * Setup the hardware configuration for a given attr_type
 */
static int __x86_pmu_event_init(struct perf_event *event)
{
        int err;

        if (!x86_pmu_initialized())
                return -ENODEV;

        err = 0;
        if (!atomic_inc_not_zero(&active_events)) {
                mutex_lock(&pmc_reserve_mutex);
                if (atomic_read(&active_events) == 0) {
                        if (!reserve_pmc_hardware())
                                err = -EBUSY;
                        else
                                reserve_ds_buffers();
                }
                if (!err)
                        atomic_inc(&active_events);
                mutex_unlock(&pmc_reserve_mutex);
        }
        if (err)
                return err;

        event->destroy = hw_perf_event_destroy;

        event->hw.idx = -1;
        event->hw.last_cpu = -1;
        event->hw.last_tag = ~0ULL;

        /* mark unused */
        event->hw.extra_reg.idx = EXTRA_REG_NONE;

        return x86_pmu.hw_config(event);
}

static void x86_pmu_disable_all(void)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        int idx;

        for (idx = 0; idx < x86_pmu.num_counters; idx++) {
                u64 val;

                if (!test_bit(idx, cpuc->active_mask))
                        continue;
                rdmsrl(x86_pmu_config_addr(idx), val);
                if (!(val & ARCH_PERFMON_EVENTSEL_ENABLE))
                        continue;
                val &= ~ARCH_PERFMON_EVENTSEL_ENABLE;
                wrmsrl(x86_pmu_config_addr(idx), val);
        }
}

static void x86_pmu_disable(struct pmu *pmu)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);

        if (!x86_pmu_initialized())
                return;

        if (!cpuc->enabled)
                return;

        cpuc->n_added = 0;
        cpuc->enabled = 0;
        barrier();

        x86_pmu.disable_all();
}

static inline void __x86_pmu_enable_event(struct hw_perf_event *hwc,
                                          u64 enable_mask)
{
        if (hwc->extra_reg.reg)
                wrmsrl(hwc->extra_reg.reg, hwc->extra_reg.config);
        wrmsrl(hwc->config_base, hwc->config | enable_mask);
}

static void x86_pmu_enable_all(int added)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        int idx;

        for (idx = 0; idx < x86_pmu.num_counters; idx++) {
                struct hw_perf_event *hwc = &cpuc->events[idx]->hw;

                if (!test_bit(idx, cpuc->active_mask))
                        continue;

                __x86_pmu_enable_event(hwc, ARCH_PERFMON_EVENTSEL_ENABLE);
        }
}

static struct pmu pmu;

static inline int is_x86_event(struct perf_event *event)
{
        return event->pmu == &pmu;
}

static int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign)
{
        struct event_constraint *c, *constraints[X86_PMC_IDX_MAX];
        unsigned long used_mask[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
        int i, j, w, wmax, num = 0;
        struct hw_perf_event *hwc;

        bitmap_zero(used_mask, X86_PMC_IDX_MAX);

        for (i = 0; i < n; i++) {
                c = x86_pmu.get_event_constraints(cpuc, cpuc->event_list[i]);
                constraints[i] = c;
        }

        /*
         * fastpath, try to reuse previous register
         */
        for (i = 0; i < n; i++) {
                hwc = &cpuc->event_list[i]->hw;
                c = constraints[i];

                /* never assigned */
                if (hwc->idx == -1)
                        break;

                /* constraint still honored */
                if (!test_bit(hwc->idx, c->idxmsk))
                        break;

                /* not already used */
                if (test_bit(hwc->idx, used_mask))
                        break;

                __set_bit(hwc->idx, used_mask);
                if (assign)
                        assign[i] = hwc->idx;
        }
        if (i == n)
                goto done;

        /*
         * begin slow path
         */

        bitmap_zero(used_mask, X86_PMC_IDX_MAX);

        /*
         * weight = number of possible counters
         *
         * 1    = most constrained, only works on one counter
         * wmax = least constrained, works on any counter
         *
         * assign events to counters starting with most
         * constrained events.
         */
        wmax = x86_pmu.num_counters;

        /*
         * when fixed event counters are present,
         * wmax is incremented by 1 to account
         * for one more choice
         */
        if (x86_pmu.num_counters_fixed)
                wmax++;

        for (w = 1, num = n; num && w <= wmax; w++) {
                /* for each event */
                for (i = 0; num && i < n; i++) {
                        c = constraints[i];
                        hwc = &cpuc->event_list[i]->hw;

                        if (c->weight != w)
                                continue;

                        for_each_set_bit(j, c->idxmsk, X86_PMC_IDX_MAX) {
                                if (!test_bit(j, used_mask))
                                        break;
                        }

                        if (j == X86_PMC_IDX_MAX)
                                break;

                        __set_bit(j, used_mask);

                        if (assign)
                                assign[i] = j;
                        num--;
                }
        }
done:
        /*
         * scheduling failed or is just a simulation,
         * free resources if necessary
         */
        if (!assign || num) {
                for (i = 0; i < n; i++) {
                        if (x86_pmu.put_event_constraints)
                                x86_pmu.put_event_constraints(cpuc, cpuc->event_list[i]);
                }
        }
        return num ? -ENOSPC : 0;
}

/*
 * dogrp: true if must collect siblings events (group)
 * returns total number of events and error code
 */
static int collect_events(struct cpu_hw_events *cpuc, struct perf_event *leader, bool dogrp)
{
        struct perf_event *event;
        int n, max_count;

        max_count = x86_pmu.num_counters + x86_pmu.num_counters_fixed;

        /* current number of events already accepted */
        n = cpuc->n_events;

        if (is_x86_event(leader)) {
                if (n >= max_count)
                        return -ENOSPC;
                cpuc->event_list[n] = leader;
                n++;
        }
        if (!dogrp)
                return n;

        list_for_each_entry(event, &leader->sibling_list, group_entry) {
                if (!is_x86_event(event) ||
                    event->state <= PERF_EVENT_STATE_OFF)
                        continue;

                if (n >= max_count)
                        return -ENOSPC;

                cpuc->event_list[n] = event;
                n++;
        }
        return n;
}

static inline void x86_assign_hw_event(struct perf_event *event,
                                struct cpu_hw_events *cpuc, int i)
{
        struct hw_perf_event *hwc = &event->hw;

        hwc->idx = cpuc->assign[i];
        hwc->last_cpu = smp_processor_id();
        hwc->last_tag = ++cpuc->tags[i];

        if (hwc->idx == X86_PMC_IDX_FIXED_BTS) {
                hwc->config_base = 0;
                hwc->event_base = 0;
        } else if (hwc->idx >= X86_PMC_IDX_FIXED) {
                hwc->config_base = MSR_ARCH_PERFMON_FIXED_CTR_CTRL;
                hwc->event_base = MSR_ARCH_PERFMON_FIXED_CTR0 + (hwc->idx - X86_PMC_IDX_FIXED);
        } else {
                hwc->config_base = x86_pmu_config_addr(hwc->idx);
                hwc->event_base  = x86_pmu_event_addr(hwc->idx);
        }
}

static inline int match_prev_assignment(struct hw_perf_event *hwc,
                                        struct cpu_hw_events *cpuc,
                                        int i)
{
        return hwc->idx == cpuc->assign[i] &&
                hwc->last_cpu == smp_processor_id() &&
                hwc->last_tag == cpuc->tags[i];
}

static void x86_pmu_start(struct perf_event *event, int flags);
static void x86_pmu_stop(struct perf_event *event, int flags);

static void x86_pmu_enable(struct pmu *pmu)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        struct perf_event *event;
        struct hw_perf_event *hwc;
        int i, added = cpuc->n_added;

        if (!x86_pmu_initialized())
                return;

        if (cpuc->enabled)
                return;

        if (cpuc->n_added) {
                int n_running = cpuc->n_events - cpuc->n_added;
                /*
                 * apply assignment obtained either from
                 * hw_perf_group_sched_in() or x86_pmu_enable()
                 *
                 * step1: save events moving to new counters
                 * step2: reprogram moved events into new counters
                 */
                for (i = 0; i < n_running; i++) {
                        event = cpuc->event_list[i];
                        hwc = &event->hw;

                        /*
                         * we can avoid reprogramming counter if:
                         * - assigned same counter as last time
                         * - running on same CPU as last time
                         * - no other event has used the counter since
                         */
                        if (hwc->idx == -1 ||
                            match_prev_assignment(hwc, cpuc, i))
                                continue;

                        /*
                         * Ensure we don't accidentally enable a stopped
                         * counter simply because we rescheduled.
                         */
                        if (hwc->state & PERF_HES_STOPPED)
                                hwc->state |= PERF_HES_ARCH;

                        x86_pmu_stop(event, PERF_EF_UPDATE);
                }

                for (i = 0; i < cpuc->n_events; i++) {
                        event = cpuc->event_list[i];
                        hwc = &event->hw;

                        if (!match_prev_assignment(hwc, cpuc, i))
                                x86_assign_hw_event(event, cpuc, i);
                        else if (i < n_running)
                                continue;

                        if (hwc->state & PERF_HES_ARCH)
                                continue;

                        x86_pmu_start(event, PERF_EF_RELOAD);
                }
                cpuc->n_added = 0;
                perf_events_lapic_init();
        }

        cpuc->enabled = 1;
        barrier();

        x86_pmu.enable_all(added);
}

static inline void x86_pmu_disable_event(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;

        wrmsrl(hwc->config_base, hwc->config);
}

static DEFINE_PER_CPU(u64 [X86_PMC_IDX_MAX], pmc_prev_left);

/*
 * Set the next IRQ period, based on the hwc->period_left value.
 * To be called with the event disabled in hw:
 */
static int
x86_perf_event_set_period(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;
        s64 left = local64_read(&hwc->period_left);
        s64 period = hwc->sample_period;
        int ret = 0, idx = hwc->idx;

        if (idx == X86_PMC_IDX_FIXED_BTS)
                return 0;

        /*
         * If we are way outside a reasonable range then just skip forward:
         */
        if (unlikely(left <= -period)) {
                left = period;
                local64_set(&hwc->period_left, left);
                hwc->last_period = period;
                ret = 1;
        }

        if (unlikely(left <= 0)) {
                left += period;
                local64_set(&hwc->period_left, left);
                hwc->last_period = period;
                ret = 1;
        }
        /*
         * Quirk: certain CPUs dont like it if just 1 hw_event is left:
         */
        if (unlikely(left < 2))
                left = 2;

        if (left > x86_pmu.max_period)
                left = x86_pmu.max_period;

        per_cpu(pmc_prev_left[idx], smp_processor_id()) = left;

        /*
         * The hw event starts counting from this event offset,
         * mark it to be able to extra future deltas:
         */
        local64_set(&hwc->prev_count, (u64)-left);

        wrmsrl(hwc->event_base, (u64)(-left) & x86_pmu.cntval_mask);

        /*
         * Due to erratum on certan cpu we need
         * a second write to be sure the register
         * is updated properly
         */
        if (x86_pmu.perfctr_second_write) {
                wrmsrl(hwc->event_base,
                        (u64)(-left) & x86_pmu.cntval_mask);
        }

        perf_event_update_userpage(event);

        return ret;
}

static void x86_pmu_enable_event(struct perf_event *event)
{
        if (__this_cpu_read(cpu_hw_events.enabled))
                __x86_pmu_enable_event(&event->hw,
                                       ARCH_PERFMON_EVENTSEL_ENABLE);
}

/*
 * Add a single event to the PMU.
 *
 * The event is added to the group of enabled events
 * but only if it can be scehduled with existing events.
 */
static int x86_pmu_add(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        struct hw_perf_event *hwc;
        int assign[X86_PMC_IDX_MAX];
        int n, n0, ret;

        hwc = &event->hw;

        perf_pmu_disable(event->pmu);
        n0 = cpuc->n_events;
        ret = n = collect_events(cpuc, event, false);
        if (ret < 0)
                goto out;

        hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
        if (!(flags & PERF_EF_START))
                hwc->state |= PERF_HES_ARCH;

        /*
         * If group events scheduling transaction was started,
         * skip the schedulability test here, it will be performed
         * at commit time (->commit_txn) as a whole
         */
        if (cpuc->group_flag & PERF_EVENT_TXN)
                goto done_collect;

        ret = x86_pmu.schedule_events(cpuc, n, assign);
        if (ret)
                goto out;
        /*
         * copy new assignment, now we know it is possible
         * will be used by hw_perf_enable()
         */
        memcpy(cpuc->assign, assign, n*sizeof(int));

done_collect:
        cpuc->n_events = n;
        cpuc->n_added += n - n0;
        cpuc->n_txn += n - n0;

        ret = 0;
out:
        perf_pmu_enable(event->pmu);
        return ret;
}

static void x86_pmu_start(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        int idx = event->hw.idx;

        if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
                return;

        if (WARN_ON_ONCE(idx == -1))
                return;

        if (flags & PERF_EF_RELOAD) {
                WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));
                x86_perf_event_set_period(event);
        }

        event->hw.state = 0;

        cpuc->events[idx] = event;
        __set_bit(idx, cpuc->active_mask);
        __set_bit(idx, cpuc->running);
        x86_pmu.enable(event);
        perf_event_update_userpage(event);
}

void perf_event_print_debug(void)
{
        u64 ctrl, status, overflow, pmc_ctrl, pmc_count, prev_left, fixed;
        u64 pebs;
        struct cpu_hw_events *cpuc;
        unsigned long flags;
        int cpu, idx;

        if (!x86_pmu.num_counters)
                return;

        local_irq_save(flags);

        cpu = smp_processor_id();
        cpuc = &per_cpu(cpu_hw_events, cpu);

        if (x86_pmu.version >= 2) {
                rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, ctrl);
                rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, status);
                rdmsrl(MSR_CORE_PERF_GLOBAL_OVF_CTRL, overflow);
                rdmsrl(MSR_ARCH_PERFMON_FIXED_CTR_CTRL, fixed);
                rdmsrl(MSR_IA32_PEBS_ENABLE, pebs);

                pr_info("\n");
                pr_info("CPU#%d: ctrl:       %016llx\n", cpu, ctrl);
                pr_info("CPU#%d: status:     %016llx\n", cpu, status);
                pr_info("CPU#%d: overflow:   %016llx\n", cpu, overflow);
                pr_info("CPU#%d: fixed:      %016llx\n", cpu, fixed);
                pr_info("CPU#%d: pebs:       %016llx\n", cpu, pebs);
        }
        pr_info("CPU#%d: active:     %016llx\n", cpu, *(u64 *)cpuc->active_mask);

        for (idx = 0; idx < x86_pmu.num_counters; idx++) {
                rdmsrl(x86_pmu_config_addr(idx), pmc_ctrl);
                rdmsrl(x86_pmu_event_addr(idx), pmc_count);

                prev_left = per_cpu(pmc_prev_left[idx], cpu);

                pr_info("CPU#%d:   gen-PMC%d ctrl:  %016llx\n",
                        cpu, idx, pmc_ctrl);
                pr_info("CPU#%d:   gen-PMC%d count: %016llx\n",
                        cpu, idx, pmc_count);
                pr_info("CPU#%d:   gen-PMC%d left:  %016llx\n",
                        cpu, idx, prev_left);
        }
        for (idx = 0; idx < x86_pmu.num_counters_fixed; idx++) {
                rdmsrl(MSR_ARCH_PERFMON_FIXED_CTR0 + idx, pmc_count);

                pr_info("CPU#%d: fixed-PMC%d count: %016llx\n",
                        cpu, idx, pmc_count);
        }
        local_irq_restore(flags);
}

static void x86_pmu_stop(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        struct hw_perf_event *hwc = &event->hw;

        if (__test_and_clear_bit(hwc->idx, cpuc->active_mask)) {
                x86_pmu.disable(event);
                cpuc->events[hwc->idx] = NULL;
                WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
                hwc->state |= PERF_HES_STOPPED;
        }

        if ((flags & PERF_EF_UPDATE) && !(hwc->state & PERF_HES_UPTODATE)) {
                /*
                 * Drain the remaining delta count out of a event
                 * that we are disabling:
                 */
                x86_perf_event_update(event);
                hwc->state |= PERF_HES_UPTODATE;
        }
}

static void x86_pmu_del(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        int i;

        /*
         * If we're called during a txn, we don't need to do anything.
         * The events never got scheduled and ->cancel_txn will truncate
         * the event_list.
         */
        if (cpuc->group_flag & PERF_EVENT_TXN)
                return;

        x86_pmu_stop(event, PERF_EF_UPDATE);

        for (i = 0; i < cpuc->n_events; i++) {
                if (event == cpuc->event_list[i]) {

                        if (x86_pmu.put_event_constraints)
                                x86_pmu.put_event_constraints(cpuc, event);

                        while (++i < cpuc->n_events)
                                cpuc->event_list[i-1] = cpuc->event_list[i];

                        --cpuc->n_events;
                        break;
                }
        }
        perf_event_update_userpage(event);
}

static int x86_pmu_handle_irq(struct pt_regs *regs)
{
        struct perf_sample_data data;
        struct cpu_hw_events *cpuc;
        struct perf_event *event;
        int idx, handled = 0;
        u64 val;

        perf_sample_data_init(&data, 0);

        cpuc = &__get_cpu_var(cpu_hw_events);

        /*
         * Some chipsets need to unmask the LVTPC in a particular spot
         * inside the nmi handler.  As a result, the unmasking was pushed
         * into all the nmi handlers.
         *
         * This generic handler doesn't seem to have any issues where the
         * unmasking occurs so it was left at the top.
         */
        apic_write(APIC_LVTPC, APIC_DM_NMI);

        for (idx = 0; idx < x86_pmu.num_counters; idx++) {
                if (!test_bit(idx, cpuc->active_mask)) {
                        /*
                         * Though we deactivated the counter some cpus
                         * might still deliver spurious interrupts still
                         * in flight. Catch them:
                         */
                        if (__test_and_clear_bit(idx, cpuc->running))
                                handled++;
                        continue;
                }

                event = cpuc->events[idx];

                val = x86_perf_event_update(event);
                if (val & (1ULL << (x86_pmu.cntval_bits - 1)))
                        continue;

                /*
                 * event overflow
                 */
                handled++;
                data.period     = event->hw.last_period;

                if (!x86_perf_event_set_period(event))
                        continue;

                if (perf_event_overflow(event, &data, regs))
                        x86_pmu_stop(event, 0);
        }

        if (handled)
                inc_irq_stat(apic_perf_irqs);

        return handled;
}

void perf_events_lapic_init(void)
{
        if (!x86_pmu.apic || !x86_pmu_initialized())
                return;

        /*
         * Always use NMI for PMU
         */
        apic_write(APIC_LVTPC, APIC_DM_NMI);
}

struct pmu_nmi_state {
        unsigned int    marked;
        int             handled;
};

static DEFINE_PER_CPU(struct pmu_nmi_state, pmu_nmi);

static int __kprobes
perf_event_nmi_handler(struct notifier_block *self,
                         unsigned long cmd, void *__args)
{
        struct die_args *args = __args;
        unsigned int this_nmi;
        int handled;

        if (!atomic_read(&active_events))
                return NOTIFY_DONE;

        switch (cmd) {
        case DIE_NMI:
                break;
        case DIE_NMIUNKNOWN:
                this_nmi = percpu_read(irq_stat.__nmi_count);
                if (this_nmi != __this_cpu_read(pmu_nmi.marked))
                        /* let the kernel handle the unknown nmi */
                        return NOTIFY_DONE;
                /*
                 * This one is a PMU back-to-back nmi. Two events
                 * trigger 'simultaneously' raising two back-to-back
                 * NMIs. If the first NMI handles both, the latter
                 * will be empty and daze the CPU. So, we drop it to
                 * avoid false-positive 'unknown nmi' messages.
                 */
                return NOTIFY_STOP;
        default:
                return NOTIFY_DONE;
        }

        handled = x86_pmu.handle_irq(args->regs);
        if (!handled)
                return NOTIFY_DONE;

        this_nmi = percpu_read(irq_stat.__nmi_count);
        if ((handled > 1) ||
                /* the next nmi could be a back-to-back nmi */
            ((__this_cpu_read(pmu_nmi.marked) == this_nmi) &&
             (__this_cpu_read(pmu_nmi.handled) > 1))) {
                /*
                 * We could have two subsequent back-to-back nmis: The
                 * first handles more than one counter, the 2nd
                 * handles only one counter and the 3rd handles no
                 * counter.
                 *
                 * This is the 2nd nmi because the previous was
                 * handling more than one counter. We will mark the
                 * next (3rd) and then drop it if unhandled.
                 */
                __this_cpu_write(pmu_nmi.marked, this_nmi + 1);
                __this_cpu_write(pmu_nmi.handled, handled);
        }

        return NOTIFY_STOP;
}

static __read_mostly struct notifier_block perf_event_nmi_notifier = {
        .notifier_call          = perf_event_nmi_handler,
        .next                   = NULL,
        .priority               = NMI_LOCAL_LOW_PRIOR,
};

static struct event_constraint unconstrained;
static struct event_constraint emptyconstraint;

static struct event_constraint *
x86_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
{
        struct event_constraint *c;

        if (x86_pmu.event_constraints) {
                for_each_event_constraint(c, x86_pmu.event_constraints) {
                        if ((event->hw.config & c->cmask) == c->code)
                                return c;
                }
        }

        return &unconstrained;
}

#include "perf_event_amd.c"
#include "perf_event_p6.c"
#include "perf_event_p4.c"
#include "perf_event_intel_lbr.c"
#include "perf_event_intel_ds.c"
#include "perf_event_intel.c"

static int __cpuinit
x86_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu)
{
        unsigned int cpu = (long)hcpu;
        int ret = NOTIFY_OK;

        switch (action & ~CPU_TASKS_FROZEN) {
        case CPU_UP_PREPARE:
                if (x86_pmu.cpu_prepare)
                        ret = x86_pmu.cpu_prepare(cpu);
                break;

        case CPU_STARTING:
                if (x86_pmu.cpu_starting)
                        x86_pmu.cpu_starting(cpu);
                break;

        case CPU_DYING:
                if (x86_pmu.cpu_dying)
                        x86_pmu.cpu_dying(cpu);
                break;

        case CPU_UP_CANCELED:
        case CPU_DEAD:
                if (x86_pmu.cpu_dead)
                        x86_pmu.cpu_dead(cpu);
                break;

        default:
                break;
        }

        return ret;
}

static void __init pmu_check_apic(void)
{
        if (cpu_has_apic)
                return;

        x86_pmu.apic = 0;
        pr_info("no APIC, boot with the \"lapic\" boot parameter to force-enable it.\n");
        pr_info("no hardware sampling interrupt available.\n");
}

static int __init init_hw_perf_events(void)
{
        struct event_constraint *c;
        int err;

        pr_info("Performance Events: ");

        switch (boot_cpu_data.x86_vendor) {
        case X86_VENDOR_INTEL:
                err = intel_pmu_init();
                break;
        case X86_VENDOR_AMD:
                err = amd_pmu_init();
                break;
        default:
                return 0;
        }
        if (err != 0) {
                pr_cont("no PMU driver, software events only.\n");
                return 0;
        }

        pmu_check_apic();

        /* sanity check that the hardware exists or is emulated */
        if (!check_hw_exists())
                return 0;

        pr_cont("%s PMU driver.\n", x86_pmu.name);

        if (x86_pmu.quirks)
                x86_pmu.quirks();

        if (x86_pmu.num_counters > X86_PMC_MAX_GENERIC) {
                WARN(1, KERN_ERR "hw perf events %d > max(%d), clipping!",
                     x86_pmu.num_counters, X86_PMC_MAX_GENERIC);
                x86_pmu.num_counters = X86_PMC_MAX_GENERIC;
        }
        x86_pmu.intel_ctrl = (1 << x86_pmu.num_counters) - 1;

        if (x86_pmu.num_counters_fixed > X86_PMC_MAX_FIXED) {
                WARN(1, KERN_ERR "hw perf events fixed %d > max(%d), clipping!",
                     x86_pmu.num_counters_fixed, X86_PMC_MAX_FIXED);
                x86_pmu.num_counters_fixed = X86_PMC_MAX_FIXED;
        }

        x86_pmu.intel_ctrl |=
                ((1LL << x86_pmu.num_counters_fixed)-1) << X86_PMC_IDX_FIXED;

        perf_events_lapic_init();
        register_die_notifier(&perf_event_nmi_notifier);

        unconstrained = (struct event_constraint)
                __EVENT_CONSTRAINT(0, (1ULL << x86_pmu.num_counters) - 1,
                                   0, x86_pmu.num_counters);

        if (x86_pmu.event_constraints) {
                for_each_event_constraint(c, x86_pmu.event_constraints) {
                        if (c->cmask != X86_RAW_EVENT_MASK)
                                continue;

                        c->idxmsk64 |= (1ULL << x86_pmu.num_counters) - 1;
                        c->weight += x86_pmu.num_counters;
                }
        }

        pr_info("... version:                %d\n",     x86_pmu.version);
        pr_info("... bit width:              %d\n",     x86_pmu.cntval_bits);
        pr_info("... generic registers:      %d\n",     x86_pmu.num_counters);
        pr_info("... value mask:             %016Lx\n", x86_pmu.cntval_mask);
        pr_info("... max period:             %016Lx\n", x86_pmu.max_period);
        pr_info("... fixed-purpose events:   %d\n",     x86_pmu.num_counters_fixed);
        pr_info("... event mask:             %016Lx\n", x86_pmu.intel_ctrl);

        perf_pmu_register(&pmu, "cpu", PERF_TYPE_RAW);
        perf_cpu_notifier(x86_pmu_notifier);

        return 0;
}
early_initcall(init_hw_perf_events);

static inline void x86_pmu_read(struct perf_event *event)
{
        x86_perf_event_update(event);
}

/*
 * Start group events scheduling transaction
 * Set the flag to make pmu::enable() not perform the
 * schedulability test, it will be performed at commit time
 */
static void x86_pmu_start_txn(struct pmu *pmu)
{
        perf_pmu_disable(pmu);
        __this_cpu_or(cpu_hw_events.group_flag, PERF_EVENT_TXN);
        __this_cpu_write(cpu_hw_events.n_txn, 0);
}

/*
 * Stop group events scheduling transaction
 * Clear the flag and pmu::enable() will perform the
 * schedulability test.
 */
static void x86_pmu_cancel_txn(struct pmu *pmu)
{
        __this_cpu_and(cpu_hw_events.group_flag, ~PERF_EVENT_TXN);
        /*
         * Truncate the collected events.
         */
        __this_cpu_sub(cpu_hw_events.n_added, __this_cpu_read(cpu_hw_events.n_txn));
        __this_cpu_sub(cpu_hw_events.n_events, __this_cpu_read(cpu_hw_events.n_txn));
        perf_pmu_enable(pmu);
}

/*
 * Commit group events scheduling transaction
 * Perform the group schedulability test as a whole
 * Return 0 if success
 */
static int x86_pmu_commit_txn(struct pmu *pmu)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        int assign[X86_PMC_IDX_MAX];
        int n, ret;

        n = cpuc->n_events;

        if (!x86_pmu_initialized())
                return -EAGAIN;

        ret = x86_pmu.schedule_events(cpuc, n, assign);
        if (ret)
                return ret;

        /*
         * copy new assignment, now we know it is possible
         * will be used by hw_perf_enable()
         */
        memcpy(cpuc->assign, assign, n*sizeof(int));

        cpuc->group_flag &= ~PERF_EVENT_TXN;
        perf_pmu_enable(pmu);
        return 0;
}

/*
 * validate that we can schedule this event
 */
static int validate_event(struct perf_event *event)
{
        struct cpu_hw_events *fake_cpuc;
        struct event_constraint *c;
        int ret = 0;

        fake_cpuc = kmalloc(sizeof(*fake_cpuc), GFP_KERNEL | __GFP_ZERO);
        if (!fake_cpuc)
                return -ENOMEM;

        c = x86_pmu.get_event_constraints(fake_cpuc, event);

        if (!c || !c->weight)
                ret = -ENOSPC;

        if (x86_pmu.put_event_constraints)
                x86_pmu.put_event_constraints(fake_cpuc, event);

        kfree(fake_cpuc);

        return ret;
}

/*
 * validate a single event group
 *
 * validation include:
 *      - check events are compatible which each other
 *      - events do not compete for the same counter
 *      - number of events <= number of counters
 *
 * validation ensures the group can be loaded onto the
 * PMU if it was the only group available.
 */
static int validate_group(struct perf_event *event)
{
        struct perf_event *leader = event->group_leader;
        struct cpu_hw_events *fake_cpuc;
        int ret, n;

        ret = -ENOMEM;
        fake_cpuc = kmalloc(sizeof(*fake_cpuc), GFP_KERNEL | __GFP_ZERO);
        if (!fake_cpuc)
                goto out;
        /*
         * the event is not yet connected with its
         * siblings therefore we must first collect
         * existing siblings, then add the new event
         * before we can simulate the scheduling
         */
        ret = -ENOSPC;
        n = collect_events(fake_cpuc, leader, true);
        if (n < 0)
                goto out_free;

        fake_cpuc->n_events = n;
        n = collect_events(fake_cpuc, event, false);
        if (n < 0)
                goto out_free;

        fake_cpuc->n_events = n;

        ret = x86_pmu.schedule_events(fake_cpuc, n, NULL);

out_free:
        kfree(fake_cpuc);
out:
        return ret;
}

static int x86_pmu_event_init(struct perf_event *event)
{
        struct pmu *tmp;
        int err;

        switch (event->attr.type) {
        case PERF_TYPE_RAW:
        case PERF_TYPE_HARDWARE:
        case PERF_TYPE_HW_CACHE:
                break;

        default:
                return -ENOENT;
        }

        err = __x86_pmu_event_init(event);
        if (!err) {
                /*
                 * we temporarily connect event to its pmu
                 * such that validate_group() can classify
                 * it as an x86 event using is_x86_event()
                 */
                tmp = event->pmu;
                event->pmu = &pmu;

                if (event->group_leader != event)
                        err = validate_group(event);
                else
                        err = validate_event(event);

                event->pmu = tmp;
        }
        if (err) {
                if (event->destroy)
                        event->destroy(event);
        }

        return err;
}

static struct pmu pmu = {
        .pmu_enable     = x86_pmu_enable,
        .pmu_disable    = x86_pmu_disable,

        .event_init     = x86_pmu_event_init,

        .add            = x86_pmu_add,
        .del            = x86_pmu_del,
        .start          = x86_pmu_start,
        .stop           = x86_pmu_stop,
        .read           = x86_pmu_read,

        .start_txn      = x86_pmu_start_txn,
        .cancel_txn     = x86_pmu_cancel_txn,
        .commit_txn     = x86_pmu_commit_txn,
};

/*
 * callchain support
 */

static int backtrace_stack(void *data, char *name)
{
        return 0;
}

static void backtrace_address(void *data, unsigned long addr, int reliable)
{
        struct perf_callchain_entry *entry = data;

        perf_callchain_store(entry, addr);
}

static const struct stacktrace_ops backtrace_ops = {
        .stack                  = backtrace_stack,
        .address                = backtrace_address,
        .walk_stack             = print_context_stack_bp,
};

void
perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
{
        if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
                /* TODO: We don't support guest os callchain now */
                return;
        }

        perf_callchain_store(entry, regs->ip);

        dump_trace(NULL, regs, NULL, 0, &backtrace_ops, entry);
}

#ifdef CONFIG_COMPAT
static inline int
perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
{
        /* 32-bit process in 64-bit kernel. */
        struct stack_frame_ia32 frame;
        const void __user *fp;

        if (!test_thread_flag(TIF_IA32))
                return 0;

        fp = compat_ptr(regs->bp);
        while (entry->nr < PERF_MAX_STACK_DEPTH) {
                unsigned long bytes;
                frame.next_frame     = 0;
                frame.return_address = 0;

                bytes = copy_from_user_nmi(&frame, fp, sizeof(frame));
                if (bytes != sizeof(frame))
                        break;

                if (fp < compat_ptr(regs->sp))
                        break;

                perf_callchain_store(entry, frame.return_address);
                fp = compat_ptr(frame.next_frame);
        }
        return 1;
}
#else
static inline int
perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
{
    return 0;
}
#endif

void
perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
{
        struct stack_frame frame;
        const void __user *fp;

        if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
                /* TODO: We don't support guest os callchain now */
                return;
        }

        fp = (void __user *)regs->bp;

        perf_callchain_store(entry, regs->ip);

        if (perf_callchain_user32(regs, entry))
                return;

        while (entry->nr < PERF_MAX_STACK_DEPTH) {
                unsigned long bytes;
                frame.next_frame             = NULL;
                frame.return_address = 0;

                bytes = copy_from_user_nmi(&frame, fp, sizeof(frame));
                if (bytes != sizeof(frame))
                        break;

                if ((unsigned long)fp < regs->sp)
                        break;

                perf_callchain_store(entry, frame.return_address);
                fp = frame.next_frame;
        }
}

unsigned long perf_instruction_pointer(struct pt_regs *regs)
{
        unsigned long ip;

        if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
                ip = perf_guest_cbs->get_guest_ip();
        else
                ip = instruction_pointer(regs);

        return ip;
}

unsigned long perf_misc_flags(struct pt_regs *regs)
{
        int misc = 0;

        if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
                if (perf_guest_cbs->is_user_mode())
                        misc |= PERF_RECORD_MISC_GUEST_USER;
                else
                        misc |= PERF_RECORD_MISC_GUEST_KERNEL;
        } else {
                if (user_mode(regs))
                        misc |= PERF_RECORD_MISC_USER;
                else
                        misc |= PERF_RECORD_MISC_KERNEL;
        }

        if (regs->flags & PERF_EFLAGS_EXACT)
                misc |= PERF_RECORD_MISC_EXACT_IP;

        return misc;
}