/*
 * Intel specific MCE features.
 * Copyright 2004 Zwane Mwaikambo <zwane@linuxpower.ca>
 * Copyright (C) 2008, 2009 Intel Corporation
 * Author: Andi Kleen
 */

#include <linux/gfp.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/sched.h>
#include <linux/cpumask.h>
#include <asm/apic.h>
#include <asm/processor.h>
#include <asm/msr.h>
#include <asm/mce.h>

#include "mce-internal.h"

/*
 * Support for Intel Correct Machine Check Interrupts. This allows
 * the CPU to raise an interrupt when a corrected machine check happened.
 * Normally we pick those up using a regular polling timer.
 * Also supports reliable discovery of shared banks.
 */

/*
 * CMCI can be delivered to multiple cpus that share a machine check bank
 * so we need to designate a single cpu to process errors logged in each bank
 * in the interrupt handler (otherwise we would have many races and potential
 * double reporting of the same error).
 * Note that this can change when a cpu is offlined or brought online since
 * some MCA banks are shared across cpus. When a cpu is offlined, cmci_clear()
 * disables CMCI on all banks owned by the cpu and clears this bitfield. At
 * this point, cmci_rediscover() kicks in and a different cpu may end up
 * taking ownership of some of the shared MCA banks that were previously
 * owned by the offlined cpu.
 */
static DEFINE_PER_CPU(mce_banks_t, mce_banks_owned);

/*
 * CMCI storm detection backoff counter
 *
 * During storm, we reset this counter to INITIAL_CHECK_INTERVAL in case we've
 * encountered an error. If not, we decrement it by one. We signal the end of
 * the CMCI storm when it reaches 0.
 */
static DEFINE_PER_CPU(int, cmci_backoff_cnt);

/*
 * cmci_discover_lock protects against parallel discovery attempts
 * which could race against each other.
 */
static DEFINE_RAW_SPINLOCK(cmci_discover_lock);

#define CMCI_THRESHOLD          1
#define CMCI_POLL_INTERVAL      (30 * HZ)
#define CMCI_STORM_INTERVAL     (HZ)
#define CMCI_STORM_THRESHOLD    15

static DEFINE_PER_CPU(unsigned long, cmci_time_stamp);
static DEFINE_PER_CPU(unsigned int, cmci_storm_cnt);
static DEFINE_PER_CPU(unsigned int, cmci_storm_state);

enum {
        CMCI_STORM_NONE,
        CMCI_STORM_ACTIVE,
        CMCI_STORM_SUBSIDED,
};

static atomic_t cmci_storm_on_cpus;

static int cmci_supported(int *banks)
{
        u64 cap;

        if (mca_cfg.cmci_disabled || mca_cfg.ignore_ce)
                return 0;

        /*
         * Vendor check is not strictly needed, but the initial
         * initialization is vendor keyed and this
         * makes sure none of the backdoors are entered otherwise.
         */
        if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
                return 0;
        if (!boot_cpu_has(X86_FEATURE_APIC) || lapic_get_maxlvt() < 6)
                return 0;
        rdmsrl(MSR_IA32_MCG_CAP, cap);
        *banks = min_t(unsigned, MAX_NR_BANKS, cap & 0xff);
        return !!(cap & MCG_CMCI_P);
}

static bool lmce_supported(void)
{
        u64 tmp;

        if (mca_cfg.lmce_disabled)
                return false;

        rdmsrl(MSR_IA32_MCG_CAP, tmp);

        /*
         * LMCE depends on recovery support in the processor. Hence both
         * MCG_SER_P and MCG_LMCE_P should be present in MCG_CAP.
         */
        if ((tmp & (MCG_SER_P | MCG_LMCE_P)) !=
                   (MCG_SER_P | MCG_LMCE_P))
                return false;

        /*
         * BIOS should indicate support for LMCE by setting bit 20 in
         * IA32_FEATURE_CONTROL without which touching MCG_EXT_CTL will
         * generate a #GP fault.
         */
        rdmsrl(MSR_IA32_FEATURE_CONTROL, tmp);
        if ((tmp & (FEATURE_CONTROL_LOCKED | FEATURE_CONTROL_LMCE)) ==
                   (FEATURE_CONTROL_LOCKED | FEATURE_CONTROL_LMCE))
                return true;

        return false;
}

bool mce_intel_cmci_poll(void)
{
        if (__this_cpu_read(cmci_storm_state) == CMCI_STORM_NONE)
                return false;

        /*
         * Reset the counter if we've logged an error in the last poll
         * during the storm.
         */
        if (machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned)))
                this_cpu_write(cmci_backoff_cnt, INITIAL_CHECK_INTERVAL);
        else
                this_cpu_dec(cmci_backoff_cnt);

        return true;
}

void mce_intel_hcpu_update(unsigned long cpu)
{
        if (per_cpu(cmci_storm_state, cpu) == CMCI_STORM_ACTIVE)
                atomic_dec(&cmci_storm_on_cpus);

        per_cpu(cmci_storm_state, cpu) = CMCI_STORM_NONE;
}

static void cmci_toggle_interrupt_mode(bool on)
{
        unsigned long flags, *owned;
        int bank;
        u64 val;

        raw_spin_lock_irqsave(&cmci_discover_lock, flags);
        owned = this_cpu_ptr(mce_banks_owned);
        for_each_set_bit(bank, owned, MAX_NR_BANKS) {
                rdmsrl(MSR_IA32_MCx_CTL2(bank), val);

                if (on)
                        val |= MCI_CTL2_CMCI_EN;
                else
                        val &= ~MCI_CTL2_CMCI_EN;

                wrmsrl(MSR_IA32_MCx_CTL2(bank), val);
        }
        raw_spin_unlock_irqrestore(&cmci_discover_lock, flags);
}

unsigned long cmci_intel_adjust_timer(unsigned long interval)
{
        if ((this_cpu_read(cmci_backoff_cnt) > 0) &&
            (__this_cpu_read(cmci_storm_state) == CMCI_STORM_ACTIVE)) {
                mce_notify_irq();
                return CMCI_STORM_INTERVAL;
        }

        switch (__this_cpu_read(cmci_storm_state)) {
        case CMCI_STORM_ACTIVE:

                /*
                 * We switch back to interrupt mode once the poll timer has
                 * silenced itself. That means no events recorded and the timer
                 * interval is back to our poll interval.
                 */
                __this_cpu_write(cmci_storm_state, CMCI_STORM_SUBSIDED);
                if (!atomic_sub_return(1, &cmci_storm_on_cpus))
                        pr_notice("CMCI storm subsided: switching to interrupt mode\n");

                /* FALLTHROUGH */

        case CMCI_STORM_SUBSIDED:
                /*
                 * We wait for all CPUs to go back to SUBSIDED state. When that
                 * happens we switch back to interrupt mode.
                 */
                if (!atomic_read(&cmci_storm_on_cpus)) {
                        __this_cpu_write(cmci_storm_state, CMCI_STORM_NONE);
                        cmci_toggle_interrupt_mode(true);
                        cmci_recheck();
                }
                return CMCI_POLL_INTERVAL;
        default:

                /* We have shiny weather. Let the poll do whatever it thinks. */
                return interval;
        }
}

static bool cmci_storm_detect(void)
{
        unsigned int cnt = __this_cpu_read(cmci_storm_cnt);
        unsigned long ts = __this_cpu_read(cmci_time_stamp);
        unsigned long now = jiffies;
        int r;

        if (__this_cpu_read(cmci_storm_state) != CMCI_STORM_NONE)
                return true;

        if (time_before_eq(now, ts + CMCI_STORM_INTERVAL)) {
                cnt++;
        } else {
                cnt = 1;
                __this_cpu_write(cmci_time_stamp, now);
        }
        __this_cpu_write(cmci_storm_cnt, cnt);

        if (cnt <= CMCI_STORM_THRESHOLD)
                return false;

        cmci_toggle_interrupt_mode(false);
        __this_cpu_write(cmci_storm_state, CMCI_STORM_ACTIVE);
        r = atomic_add_return(1, &cmci_storm_on_cpus);
        mce_timer_kick(CMCI_STORM_INTERVAL);
        this_cpu_write(cmci_backoff_cnt, INITIAL_CHECK_INTERVAL);

        if (r == 1)
                pr_notice("CMCI storm detected: switching to poll mode\n");
        return true;
}

/*
 * The interrupt handler. This is called on every event.
 * Just call the poller directly to log any events.
 * This could in theory increase the threshold under high load,
 * but doesn't for now.
 */
static void intel_threshold_interrupt(void)
{
        if (cmci_storm_detect())
                return;

        machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned));
}

/*
 * Enable CMCI (Corrected Machine Check Interrupt) for available MCE banks
 * on this CPU. Use the algorithm recommended in the SDM to discover shared
 * banks.
 */
static void cmci_discover(int banks)
{
        unsigned long *owned = (void *)this_cpu_ptr(&mce_banks_owned);
        unsigned long flags;
        int i;
        int bios_wrong_thresh = 0;

        raw_spin_lock_irqsave(&cmci_discover_lock, flags);
        for (i = 0; i < banks; i++) {
                u64 val;
                int bios_zero_thresh = 0;

                if (test_bit(i, owned))
                        continue;

                /* Skip banks in firmware first mode */
                if (test_bit(i, mce_banks_ce_disabled))
                        continue;

                rdmsrl(MSR_IA32_MCx_CTL2(i), val);

                /* Already owned by someone else? */
                if (val & MCI_CTL2_CMCI_EN) {
                        clear_bit(i, owned);
                        __clear_bit(i, this_cpu_ptr(mce_poll_banks));
                        continue;
                }

                if (!mca_cfg.bios_cmci_threshold) {
                        val &= ~MCI_CTL2_CMCI_THRESHOLD_MASK;
                        val |= CMCI_THRESHOLD;
                } else if (!(val & MCI_CTL2_CMCI_THRESHOLD_MASK)) {
                        /*
                         * If bios_cmci_threshold boot option was specified
                         * but the threshold is zero, we'll try to initialize
                         * it to 1.
                         */
                        bios_zero_thresh = 1;
                        val |= CMCI_THRESHOLD;
                }

                val |= MCI_CTL2_CMCI_EN;
                wrmsrl(MSR_IA32_MCx_CTL2(i), val);
                rdmsrl(MSR_IA32_MCx_CTL2(i), val);

                /* Did the enable bit stick? -- the bank supports CMCI */
                if (val & MCI_CTL2_CMCI_EN) {
                        set_bit(i, owned);
                        __clear_bit(i, this_cpu_ptr(mce_poll_banks));
                        /*
                         * We are able to set thresholds for some banks that
                         * had a threshold of 0. This means the BIOS has not
                         * set the thresholds properly or does not work with
                         * this boot option. Note down now and report later.
                         */
                        if (mca_cfg.bios_cmci_threshold && bios_zero_thresh &&
                                        (val & MCI_CTL2_CMCI_THRESHOLD_MASK))
                                bios_wrong_thresh = 1;
                } else {
                        WARN_ON(!test_bit(i, this_cpu_ptr(mce_poll_banks)));
                }
        }
        raw_spin_unlock_irqrestore(&cmci_discover_lock, flags);
        if (mca_cfg.bios_cmci_threshold && bios_wrong_thresh) {
                pr_info_once(
                        "bios_cmci_threshold: Some banks do not have valid thresholds set\n");
                pr_info_once(
                        "bios_cmci_threshold: Make sure your BIOS supports this boot option\n");
        }
}

/*
 * Just in case we missed an event during initialization check
 * all the CMCI owned banks.
 */
void cmci_recheck(void)
{
        unsigned long flags;
        int banks;

        if (!mce_available(raw_cpu_ptr(&cpu_info)) || !cmci_supported(&banks))
                return;

        local_irq_save(flags);
        machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned));
        local_irq_restore(flags);
}

/* Caller must hold the lock on cmci_discover_lock */
static void __cmci_disable_bank(int bank)
{
        u64 val;

        if (!test_bit(bank, this_cpu_ptr(mce_banks_owned)))
                return;
        rdmsrl(MSR_IA32_MCx_CTL2(bank), val);
        val &= ~MCI_CTL2_CMCI_EN;
        wrmsrl(MSR_IA32_MCx_CTL2(bank), val);
        __clear_bit(bank, this_cpu_ptr(mce_banks_owned));
}

/*
 * Disable CMCI on this CPU for all banks it owns when it goes down.
 * This allows other CPUs to claim the banks on rediscovery.
 */
void cmci_clear(void)
{
        unsigned long flags;
        int i;
        int banks;

        if (!cmci_supported(&banks))
                return;
        raw_spin_lock_irqsave(&cmci_discover_lock, flags);
        for (i = 0; i < banks; i++)
                __cmci_disable_bank(i);
        raw_spin_unlock_irqrestore(&cmci_discover_lock, flags);
}

static void cmci_rediscover_work_func(void *arg)
{
        int banks;

        /* Recheck banks in case CPUs don't all have the same */
        if (cmci_supported(&banks))
                cmci_discover(banks);
}

/* After a CPU went down cycle through all the others and rediscover */
void cmci_rediscover(void)
{
        int banks;

        if (!cmci_supported(&banks))
                return;

        on_each_cpu(cmci_rediscover_work_func, NULL, 1);
}

/*
 * Reenable CMCI on this CPU in case a CPU down failed.
 */
void cmci_reenable(void)
{
        int banks;
        if (cmci_supported(&banks))
                cmci_discover(banks);
}

void cmci_disable_bank(int bank)
{
        int banks;
        unsigned long flags;

        if (!cmci_supported(&banks))
                return;

        raw_spin_lock_irqsave(&cmci_discover_lock, flags);
        __cmci_disable_bank(bank);
        raw_spin_unlock_irqrestore(&cmci_discover_lock, flags);
}

static void intel_init_cmci(void)
{
        int banks;

        if (!cmci_supported(&banks))
                return;

        mce_threshold_vector = intel_threshold_interrupt;
        cmci_discover(banks);
        /*
         * For CPU #0 this runs with still disabled APIC, but that's
         * ok because only the vector is set up. We still do another
         * check for the banks later for CPU #0 just to make sure
         * to not miss any events.
         */
        apic_write(APIC_LVTCMCI, THRESHOLD_APIC_VECTOR|APIC_DM_FIXED);
        cmci_recheck();
}

static void intel_init_lmce(void)
{
        u64 val;

        if (!lmce_supported())
                return;

        rdmsrl(MSR_IA32_MCG_EXT_CTL, val);

        if (!(val & MCG_EXT_CTL_LMCE_EN))
                wrmsrl(MSR_IA32_MCG_EXT_CTL, val | MCG_EXT_CTL_LMCE_EN);
}

static void intel_clear_lmce(void)
{
        u64 val;

        if (!lmce_supported())
                return;

        rdmsrl(MSR_IA32_MCG_EXT_CTL, val);
        val &= ~MCG_EXT_CTL_LMCE_EN;
        wrmsrl(MSR_IA32_MCG_EXT_CTL, val);
}

void mce_intel_feature_init(struct cpuinfo_x86 *c)
{
        intel_init_thermal(c);
        intel_init_cmci();
        intel_init_lmce();
}

void mce_intel_feature_clear(struct cpuinfo_x86 *c)
{
        intel_clear_lmce();
}