/*
 * Machine check exception handling.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright 2013 IBM Corporation
 * Author: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
 */

#undef DEBUG
#define pr_fmt(fmt) "mce: " fmt

#include <linux/hardirq.h>
#include <linux/types.h>
#include <linux/ptrace.h>
#include <linux/percpu.h>
#include <linux/export.h>
#include <linux/irq_work.h>

#include <asm/machdep.h>
#include <asm/mce.h>

static DEFINE_PER_CPU(int, mce_nest_count);
static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT], mce_event);

/* Queue for delayed MCE events. */
static DEFINE_PER_CPU(int, mce_queue_count);
static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT], mce_event_queue);

/* Queue for delayed MCE UE events. */
static DEFINE_PER_CPU(int, mce_ue_count);
static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT],
                                        mce_ue_event_queue);

static void machine_check_process_queued_event(struct irq_work *work);
void machine_check_ue_event(struct machine_check_event *evt);
static void machine_process_ue_event(struct work_struct *work);

static struct irq_work mce_event_process_work = {
        .func = machine_check_process_queued_event,
};

DECLARE_WORK(mce_ue_event_work, machine_process_ue_event);

static void mce_set_error_info(struct machine_check_event *mce,
                               struct mce_error_info *mce_err)
{
        mce->error_type = mce_err->error_type;
        switch (mce_err->error_type) {
        case MCE_ERROR_TYPE_UE:
                mce->u.ue_error.ue_error_type = mce_err->u.ue_error_type;
                break;
        case MCE_ERROR_TYPE_SLB:
                mce->u.slb_error.slb_error_type = mce_err->u.slb_error_type;
                break;
        case MCE_ERROR_TYPE_ERAT:
                mce->u.erat_error.erat_error_type = mce_err->u.erat_error_type;
                break;
        case MCE_ERROR_TYPE_TLB:
                mce->u.tlb_error.tlb_error_type = mce_err->u.tlb_error_type;
                break;
        case MCE_ERROR_TYPE_USER:
                mce->u.user_error.user_error_type = mce_err->u.user_error_type;
                break;
        case MCE_ERROR_TYPE_RA:
                mce->u.ra_error.ra_error_type = mce_err->u.ra_error_type;
                break;
        case MCE_ERROR_TYPE_LINK:
                mce->u.link_error.link_error_type = mce_err->u.link_error_type;
                break;
        case MCE_ERROR_TYPE_UNKNOWN:
        default:
                break;
        }
}

/*
 * Decode and save high level MCE information into per cpu buffer which
 * is an array of machine_check_event structure.
 */
void save_mce_event(struct pt_regs *regs, long handled,
                    struct mce_error_info *mce_err,
                    uint64_t nip, uint64_t addr, uint64_t phys_addr)
{
        int index = __this_cpu_inc_return(mce_nest_count) - 1;
        struct machine_check_event *mce = this_cpu_ptr(&mce_event[index]);

        /*
         * Return if we don't have enough space to log mce event.
         * mce_nest_count may go beyond MAX_MC_EVT but that's ok,
         * the check below will stop buffer overrun.
         */
        if (index >= MAX_MC_EVT)
                return;

        /* Populate generic machine check info */
        mce->version = MCE_V1;
        mce->srr0 = nip;
        mce->srr1 = regs->msr;
        mce->gpr3 = regs->gpr[3];
        mce->in_use = 1;

        /* Mark it recovered if we have handled it and MSR(RI=1). */
        if (handled && (regs->msr & MSR_RI))
                mce->disposition = MCE_DISPOSITION_RECOVERED;
        else
                mce->disposition = MCE_DISPOSITION_NOT_RECOVERED;

        mce->initiator = mce_err->initiator;
        mce->severity = mce_err->severity;

        /*
         * Populate the mce error_type and type-specific error_type.
         */
        mce_set_error_info(mce, mce_err);

        if (!addr)
                return;

        if (mce->error_type == MCE_ERROR_TYPE_TLB) {
                mce->u.tlb_error.effective_address_provided = true;
                mce->u.tlb_error.effective_address = addr;
        } else if (mce->error_type == MCE_ERROR_TYPE_SLB) {
                mce->u.slb_error.effective_address_provided = true;
                mce->u.slb_error.effective_address = addr;
        } else if (mce->error_type == MCE_ERROR_TYPE_ERAT) {
                mce->u.erat_error.effective_address_provided = true;
                mce->u.erat_error.effective_address = addr;
        } else if (mce->error_type == MCE_ERROR_TYPE_USER) {
                mce->u.user_error.effective_address_provided = true;
                mce->u.user_error.effective_address = addr;
        } else if (mce->error_type == MCE_ERROR_TYPE_RA) {
                mce->u.ra_error.effective_address_provided = true;
                mce->u.ra_error.effective_address = addr;
        } else if (mce->error_type == MCE_ERROR_TYPE_LINK) {
                mce->u.link_error.effective_address_provided = true;
                mce->u.link_error.effective_address = addr;
        } else if (mce->error_type == MCE_ERROR_TYPE_UE) {
                mce->u.ue_error.effective_address_provided = true;
                mce->u.ue_error.effective_address = addr;
                if (phys_addr != ULONG_MAX) {
                        mce->u.ue_error.physical_address_provided = true;
                        mce->u.ue_error.physical_address = phys_addr;
                        machine_check_ue_event(mce);
                }
        }
        return;
}

/*
 * get_mce_event:
 *      mce     Pointer to machine_check_event structure to be filled.
 *      release Flag to indicate whether to free the event slot or not.
 *              0 <= do not release the mce event. Caller will invoke
 *                   release_mce_event() once event has been consumed.
 *              1 <= release the slot.
 *
 *      return  1 = success
 *              0 = failure
 *
 * get_mce_event() will be called by platform specific machine check
 * handle routine and in KVM.
 * When we call get_mce_event(), we are still in interrupt context and
 * preemption will not be scheduled until ret_from_expect() routine
 * is called.
 */
int get_mce_event(struct machine_check_event *mce, bool release)
{
        int index = __this_cpu_read(mce_nest_count) - 1;
        struct machine_check_event *mc_evt;
        int ret = 0;

        /* Sanity check */
        if (index < 0)
                return ret;

        /* Check if we have MCE info to process. */
        if (index < MAX_MC_EVT) {
                mc_evt = this_cpu_ptr(&mce_event[index]);
                /* Copy the event structure and release the original */
                if (mce)
                        *mce = *mc_evt;
                if (release)
                        mc_evt->in_use = 0;
                ret = 1;
        }
        /* Decrement the count to free the slot. */
        if (release)
                __this_cpu_dec(mce_nest_count);

        return ret;
}

void release_mce_event(void)
{
        get_mce_event(NULL, true);
}


/*
 * Queue up the MCE event which then can be handled later.
 */
void machine_check_ue_event(struct machine_check_event *evt)
{
        int index;

        index = __this_cpu_inc_return(mce_ue_count) - 1;
        /* If queue is full, just return for now. */
        if (index >= MAX_MC_EVT) {
                __this_cpu_dec(mce_ue_count);
                return;
        }
        memcpy(this_cpu_ptr(&mce_ue_event_queue[index]), evt, sizeof(*evt));

        /* Queue work to process this event later. */
        schedule_work(&mce_ue_event_work);
}

/*
 * Queue up the MCE event which then can be handled later.
 */
void machine_check_queue_event(void)
{
        int index;
        struct machine_check_event evt;

        if (!get_mce_event(&evt, MCE_EVENT_RELEASE))
                return;

        index = __this_cpu_inc_return(mce_queue_count) - 1;
        /* If queue is full, just return for now. */
        if (index >= MAX_MC_EVT) {
                __this_cpu_dec(mce_queue_count);
                return;
        }
        memcpy(this_cpu_ptr(&mce_event_queue[index]), &evt, sizeof(evt));

        /* Queue irq work to process this event later. */
        irq_work_queue(&mce_event_process_work);
}
/*
 * process pending MCE event from the mce event queue. This function will be
 * called during syscall exit.
 */
static void machine_process_ue_event(struct work_struct *work)
{
        int index;
        struct machine_check_event *evt;

        while (__this_cpu_read(mce_ue_count) > 0) {
                index = __this_cpu_read(mce_ue_count) - 1;
                evt = this_cpu_ptr(&mce_ue_event_queue[index]);
#ifdef CONFIG_MEMORY_FAILURE
                /*
                 * This should probably queued elsewhere, but
                 * oh! well
                 */
                if (evt->error_type == MCE_ERROR_TYPE_UE) {
                        if (evt->u.ue_error.physical_address_provided) {
                                unsigned long pfn;

                                pfn = evt->u.ue_error.physical_address >>
                                        PAGE_SHIFT;
                                memory_failure(pfn, 0);
                        } else
                                pr_warn("Failed to identify bad address from "
                                        "where the uncorrectable error (UE) "
                                        "was generated\n");
                }
#endif
                __this_cpu_dec(mce_ue_count);
        }
}
/*
 * process pending MCE event from the mce event queue. This function will be
 * called during syscall exit.
 */
static void machine_check_process_queued_event(struct irq_work *work)
{
        int index;
        struct machine_check_event *evt;

        add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);

        /*
         * For now just print it to console.
         * TODO: log this error event to FSP or nvram.
         */
        while (__this_cpu_read(mce_queue_count) > 0) {
                index = __this_cpu_read(mce_queue_count) - 1;
                evt = this_cpu_ptr(&mce_event_queue[index]);
                machine_check_print_event_info(evt, false);
                __this_cpu_dec(mce_queue_count);
        }
}

void machine_check_print_event_info(struct machine_check_event *evt,
                                    bool user_mode)
{
        const char *level, *sevstr, *subtype;
        static const char *mc_ue_types[] = {
                "Indeterminate",
                "Instruction fetch",
                "Page table walk ifetch",
                "Load/Store",
                "Page table walk Load/Store",
        };
        static const char *mc_slb_types[] = {
                "Indeterminate",
                "Parity",
                "Multihit",
        };
        static const char *mc_erat_types[] = {
                "Indeterminate",
                "Parity",
                "Multihit",
        };
        static const char *mc_tlb_types[] = {
                "Indeterminate",
                "Parity",
                "Multihit",
        };
        static const char *mc_user_types[] = {
                "Indeterminate",
                "tlbie(l) invalid",
        };
        static const char *mc_ra_types[] = {
                "Indeterminate",
                "Instruction fetch (bad)",
                "Instruction fetch (foreign)",
                "Page table walk ifetch (bad)",
                "Page table walk ifetch (foreign)",
                "Load (bad)",
                "Store (bad)",
                "Page table walk Load/Store (bad)",
                "Page table walk Load/Store (foreign)",
                "Load/Store (foreign)",
        };
        static const char *mc_link_types[] = {
                "Indeterminate",
                "Instruction fetch (timeout)",
                "Page table walk ifetch (timeout)",
                "Load (timeout)",
                "Store (timeout)",
                "Page table walk Load/Store (timeout)",
        };

        /* Print things out */
        if (evt->version != MCE_V1) {
                pr_err("Machine Check Exception, Unknown event version %d !\n",
                       evt->version);
                return;
        }
        switch (evt->severity) {
        case MCE_SEV_NO_ERROR:
                level = KERN_INFO;
                sevstr = "Harmless";
                break;
        case MCE_SEV_WARNING:
                level = KERN_WARNING;
                sevstr = "";
                break;
        case MCE_SEV_ERROR_SYNC:
                level = KERN_ERR;
                sevstr = "Severe";
                break;
        case MCE_SEV_FATAL:
        default:
                level = KERN_ERR;
                sevstr = "Fatal";
                break;
        }

        printk("%s%s Machine check interrupt [%s]\n", level, sevstr,
               evt->disposition == MCE_DISPOSITION_RECOVERED ?
               "Recovered" : "Not recovered");

        if (user_mode) {
                printk("%s  NIP: [%016llx] PID: %d Comm: %s\n", level,
                        evt->srr0, current->pid, current->comm);
        } else {
                printk("%s  NIP [%016llx]: %pS\n", level, evt->srr0,
                       (void *)evt->srr0);
        }

        printk("%s  Initiator: %s\n", level,
               evt->initiator == MCE_INITIATOR_CPU ? "CPU" : "Unknown");
        switch (evt->error_type) {
        case MCE_ERROR_TYPE_UE:
                subtype = evt->u.ue_error.ue_error_type <
                        ARRAY_SIZE(mc_ue_types) ?
                        mc_ue_types[evt->u.ue_error.ue_error_type]
                        : "Unknown";
                printk("%s  Error type: UE [%s]\n", level, subtype);
                if (evt->u.ue_error.effective_address_provided)
                        printk("%s    Effective address: %016llx\n",
                               level, evt->u.ue_error.effective_address);
                if (evt->u.ue_error.physical_address_provided)
                        printk("%s    Physical address:  %016llx\n",
                               level, evt->u.ue_error.physical_address);
                break;
        case MCE_ERROR_TYPE_SLB:
                subtype = evt->u.slb_error.slb_error_type <
                        ARRAY_SIZE(mc_slb_types) ?
                        mc_slb_types[evt->u.slb_error.slb_error_type]
                        : "Unknown";
                printk("%s  Error type: SLB [%s]\n", level, subtype);
                if (evt->u.slb_error.effective_address_provided)
                        printk("%s    Effective address: %016llx\n",
                               level, evt->u.slb_error.effective_address);
                break;
        case MCE_ERROR_TYPE_ERAT:
                subtype = evt->u.erat_error.erat_error_type <
                        ARRAY_SIZE(mc_erat_types) ?
                        mc_erat_types[evt->u.erat_error.erat_error_type]
                        : "Unknown";
                printk("%s  Error type: ERAT [%s]\n", level, subtype);
                if (evt->u.erat_error.effective_address_provided)
                        printk("%s    Effective address: %016llx\n",
                               level, evt->u.erat_error.effective_address);
                break;
        case MCE_ERROR_TYPE_TLB:
                subtype = evt->u.tlb_error.tlb_error_type <
                        ARRAY_SIZE(mc_tlb_types) ?
                        mc_tlb_types[evt->u.tlb_error.tlb_error_type]
                        : "Unknown";
                printk("%s  Error type: TLB [%s]\n", level, subtype);
                if (evt->u.tlb_error.effective_address_provided)
                        printk("%s    Effective address: %016llx\n",
                               level, evt->u.tlb_error.effective_address);
                break;
        case MCE_ERROR_TYPE_USER:
                subtype = evt->u.user_error.user_error_type <
                        ARRAY_SIZE(mc_user_types) ?
                        mc_user_types[evt->u.user_error.user_error_type]
                        : "Unknown";
                printk("%s  Error type: User [%s]\n", level, subtype);
                if (evt->u.user_error.effective_address_provided)
                        printk("%s    Effective address: %016llx\n",
                               level, evt->u.user_error.effective_address);
                break;
        case MCE_ERROR_TYPE_RA:
                subtype = evt->u.ra_error.ra_error_type <
                        ARRAY_SIZE(mc_ra_types) ?
                        mc_ra_types[evt->u.ra_error.ra_error_type]
                        : "Unknown";
                printk("%s  Error type: Real address [%s]\n", level, subtype);
                if (evt->u.ra_error.effective_address_provided)
                        printk("%s    Effective address: %016llx\n",
                               level, evt->u.ra_error.effective_address);
                break;
        case MCE_ERROR_TYPE_LINK:
                subtype = evt->u.link_error.link_error_type <
                        ARRAY_SIZE(mc_link_types) ?
                        mc_link_types[evt->u.link_error.link_error_type]
                        : "Unknown";
                printk("%s  Error type: Link [%s]\n", level, subtype);
                if (evt->u.link_error.effective_address_provided)
                        printk("%s    Effective address: %016llx\n",
                               level, evt->u.link_error.effective_address);
                break;
        default:
        case MCE_ERROR_TYPE_UNKNOWN:
                printk("%s  Error type: Unknown\n", level);
                break;
        }
}
EXPORT_SYMBOL_GPL(machine_check_print_event_info);

/*
 * This function is called in real mode. Strictly no printk's please.
 *
 * regs->nip and regs->msr contains srr0 and ssr1.
 */
long machine_check_early(struct pt_regs *regs)
{
        long handled = 0;

        __this_cpu_inc(irq_stat.mce_exceptions);

        if (cur_cpu_spec && cur_cpu_spec->machine_check_early)
                handled = cur_cpu_spec->machine_check_early(regs);
        return handled;
}

/* Possible meanings for HMER_DEBUG_TRIG bit being set on POWER9 */
static enum {
        DTRIG_UNKNOWN,
        DTRIG_VECTOR_CI,        /* need to emulate vector CI load instr */
        DTRIG_SUSPEND_ESCAPE,   /* need to escape from TM suspend mode */
} hmer_debug_trig_function;

static int init_debug_trig_function(void)
{
        int pvr;
        struct device_node *cpun;
        struct property *prop = NULL;
        const char *str;

        /* First look in the device tree */
        preempt_disable();
        cpun = of_get_cpu_node(smp_processor_id(), NULL);
        if (cpun) {
                of_property_for_each_string(cpun, "ibm,hmi-special-triggers",
                                            prop, str) {
                        if (strcmp(str, "bit17-vector-ci-load") == 0)
                                hmer_debug_trig_function = DTRIG_VECTOR_CI;
                        else if (strcmp(str, "bit17-tm-suspend-escape") == 0)
                                hmer_debug_trig_function = DTRIG_SUSPEND_ESCAPE;
                }
                of_node_put(cpun);
        }
        preempt_enable();

        /* If we found the property, don't look at PVR */
        if (prop)
                goto out;

        pvr = mfspr(SPRN_PVR);
        /* Check for POWER9 Nimbus (scale-out) */
        if ((PVR_VER(pvr) == PVR_POWER9) && (pvr & 0xe000) == 0) {
                /* DD2.2 and later */
                if ((pvr & 0xfff) >= 0x202)
                        hmer_debug_trig_function = DTRIG_SUSPEND_ESCAPE;
                /* DD2.0 and DD2.1 - used for vector CI load emulation */
                else if ((pvr & 0xfff) >= 0x200)
                        hmer_debug_trig_function = DTRIG_VECTOR_CI;
        }

 out:
        switch (hmer_debug_trig_function) {
        case DTRIG_VECTOR_CI:
                pr_debug("HMI debug trigger used for vector CI load\n");
                break;
        case DTRIG_SUSPEND_ESCAPE:
                pr_debug("HMI debug trigger used for TM suspend escape\n");
                break;
        default:
                break;
        }
        return 0;
}
__initcall(init_debug_trig_function);

/*
 * Handle HMIs that occur as a result of a debug trigger.
 * Return values:
 * -1 means this is not a HMI cause that we know about
 *  0 means no further handling is required
 *  1 means further handling is required
 */
long hmi_handle_debugtrig(struct pt_regs *regs)
{
        unsigned long hmer = mfspr(SPRN_HMER);
        long ret = 0;

        /* HMER_DEBUG_TRIG bit is used for various workarounds on P9 */
        if (!((hmer & HMER_DEBUG_TRIG)
              && hmer_debug_trig_function != DTRIG_UNKNOWN))
                return -1;
                
        hmer &= ~HMER_DEBUG_TRIG;
        /* HMER is a write-AND register */
        mtspr(SPRN_HMER, ~HMER_DEBUG_TRIG);

        switch (hmer_debug_trig_function) {
        case DTRIG_VECTOR_CI:
                /*
                 * Now to avoid problems with soft-disable we
                 * only do the emulation if we are coming from
                 * host user space
                 */
                if (regs && user_mode(regs))
                        ret = local_paca->hmi_p9_special_emu = 1;

                break;

        default:
                break;
        }

        /*
         * See if any other HMI causes remain to be handled
         */
        if (hmer & mfspr(SPRN_HMEER))
                return -1;

        return ret;
}

/*
 * Return values:
 */
long hmi_exception_realmode(struct pt_regs *regs)
{       
        int ret;

        __this_cpu_inc(irq_stat.hmi_exceptions);

        ret = hmi_handle_debugtrig(regs);
        if (ret >= 0)
                return ret;

        wait_for_subcore_guest_exit();

        if (ppc_md.hmi_exception_early)
                ppc_md.hmi_exception_early(regs);

        wait_for_tb_resync();

        return 1;
}