/*
 * 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/types.h>
#include <linux/ptrace.h>
#include <linux/percpu.h>
#include <linux/export.h>
#include <linux/irq_work.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);

static void machine_check_process_queued_event(struct irq_work *work);
static struct irq_work mce_event_process_work = {
        .func = machine_check_process_queued_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_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 srr1;
        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;

        mce->initiator = MCE_INITIATOR_CPU;
        /* 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->severity = MCE_SEV_ERROR_SYNC;

        srr1 = regs->msr;

        /*
         * 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_UE) {
                mce->u.ue_error.effective_address_provided = true;
                mce->u.ue_error.effective_address = addr;
        }
        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_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_check_process_queued_event(struct irq_work *work)
{
        int index;

        /*
         * 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;
                machine_check_print_event_info(
                                this_cpu_ptr(&mce_event_queue[index]));
                __this_cpu_dec(mce_queue_count);
        }
}

void machine_check_print_event_info(struct machine_check_event *evt)
{
        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",
        };

        /* 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");
        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;
        default:
        case MCE_ERROR_TYPE_UNKNOWN:
                printk("%s  Error type: Unknown\n", level);
                break;
        }
}

uint64_t get_mce_fault_addr(struct machine_check_event *evt)
{
        switch (evt->error_type) {
        case MCE_ERROR_TYPE_UE:
                if (evt->u.ue_error.effective_address_provided)
                        return evt->u.ue_error.effective_address;
                break;
        case MCE_ERROR_TYPE_SLB:
                if (evt->u.slb_error.effective_address_provided)
                        return evt->u.slb_error.effective_address;
                break;
        case MCE_ERROR_TYPE_ERAT:
                if (evt->u.erat_error.effective_address_provided)
                        return evt->u.erat_error.effective_address;
                break;
        case MCE_ERROR_TYPE_TLB:
                if (evt->u.tlb_error.effective_address_provided)
                        return evt->u.tlb_error.effective_address;
                break;
        default:
        case MCE_ERROR_TYPE_UNKNOWN:
                break;
        }
        return 0;
}
EXPORT_SYMBOL(get_mce_fault_addr);