// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Performance monitoring support for Virtual Processor Area(VPA) based counters
 *
 * Copyright (C) 2024 IBM Corporation
 */
#define pr_fmt(fmt) "vpa_pmu: " fmt

#include <linux/module.h>
#include <linux/perf_event.h>
#include <asm/kvm_ppc.h>
#include <asm/kvm_book3s_64.h>

#define MODULE_VERS "1.0"
#define MODULE_NAME "pseries_vpa_pmu"

#define EVENT(_name, _code)     enum{_name = _code}

#define VPA_PMU_EVENT_VAR(_id)  event_attr_##_id
#define VPA_PMU_EVENT_PTR(_id)  (&event_attr_##_id.attr.attr)

static ssize_t vpa_pmu_events_sysfs_show(struct device *dev,
                                         struct device_attribute *attr, char *page)
{
        struct perf_pmu_events_attr *pmu_attr;

        pmu_attr = container_of(attr, struct perf_pmu_events_attr, attr);

        return sprintf(page, "event=0x%02llx\n", pmu_attr->id);
}

#define VPA_PMU_EVENT_ATTR(_name, _id)                          \
        PMU_EVENT_ATTR(_name, VPA_PMU_EVENT_VAR(_id), _id,      \
                        vpa_pmu_events_sysfs_show)

EVENT(L1_TO_L2_CS_LAT,  0x1);
EVENT(L2_TO_L1_CS_LAT,  0x2);
EVENT(L2_RUNTIME_AGG,   0x3);

VPA_PMU_EVENT_ATTR(l1_to_l2_lat,  L1_TO_L2_CS_LAT);
VPA_PMU_EVENT_ATTR(l2_to_l1_lat,  L2_TO_L1_CS_LAT);
VPA_PMU_EVENT_ATTR(l2_runtime_agg, L2_RUNTIME_AGG);

static struct attribute *vpa_pmu_events_attr[] = {
        VPA_PMU_EVENT_PTR(L1_TO_L2_CS_LAT),
        VPA_PMU_EVENT_PTR(L2_TO_L1_CS_LAT),
        VPA_PMU_EVENT_PTR(L2_RUNTIME_AGG),
        NULL
};

static const struct attribute_group vpa_pmu_events_group = {
        .name = "events",
        .attrs = vpa_pmu_events_attr,
};

PMU_FORMAT_ATTR(event, "config:0-31");
static struct attribute *vpa_pmu_format_attr[] = {
        &format_attr_event.attr,
        NULL,
};

static struct attribute_group vpa_pmu_format_group = {
        .name = "format",
        .attrs = vpa_pmu_format_attr,
};

static const struct attribute_group *vpa_pmu_attr_groups[] = {
        &vpa_pmu_events_group,
        &vpa_pmu_format_group,
        NULL
};

static int vpa_pmu_event_init(struct perf_event *event)
{
        if (event->attr.type != event->pmu->type)
                return -ENOENT;

        /* it does not support event sampling mode */
        if (is_sampling_event(event))
                return -EOPNOTSUPP;

        /* no branch sampling */
        if (has_branch_stack(event))
                return -EOPNOTSUPP;

        /* Invalid event code */
        if ((event->attr.config <= 0) || (event->attr.config > 3))
                return -EINVAL;

        return 0;
}

static unsigned long get_counter_data(struct perf_event *event)
{
        unsigned int config = event->attr.config;
        u64 data;

        switch (config) {
        case L1_TO_L2_CS_LAT:
                if (event->attach_state & PERF_ATTACH_TASK)
                        data = kvmhv_get_l1_to_l2_cs_time_vcpu();
                else
                        data = kvmhv_get_l1_to_l2_cs_time();
                break;
        case L2_TO_L1_CS_LAT:
                if (event->attach_state & PERF_ATTACH_TASK)
                        data = kvmhv_get_l2_to_l1_cs_time_vcpu();
                else
                        data = kvmhv_get_l2_to_l1_cs_time();
                break;
        case L2_RUNTIME_AGG:
                if (event->attach_state & PERF_ATTACH_TASK)
                        data = kvmhv_get_l2_runtime_agg_vcpu();
                else
                        data = kvmhv_get_l2_runtime_agg();
                break;
        default:
                data = 0;
                break;
        }

        return data;
}

static int vpa_pmu_add(struct perf_event *event, int flags)
{
        u64 data;

        kvmhv_set_l2_counters_status(smp_processor_id(), true);

        data = get_counter_data(event);
        local64_set(&event->hw.prev_count, data);

        return 0;
}

static void vpa_pmu_read(struct perf_event *event)
{
        u64 prev_data, new_data, final_data;

        prev_data = local64_read(&event->hw.prev_count);
        new_data = get_counter_data(event);
        final_data = new_data - prev_data;

        local64_add(final_data, &event->count);
}

static void vpa_pmu_del(struct perf_event *event, int flags)
{
        vpa_pmu_read(event);

        /*
         * Disable vpa counter accumulation
         */
        kvmhv_set_l2_counters_status(smp_processor_id(), false);
}

static struct pmu vpa_pmu = {
        .module         = THIS_MODULE,
        .task_ctx_nr    = perf_sw_context,
        .name           = "vpa_pmu",
        .event_init     = vpa_pmu_event_init,
        .add            = vpa_pmu_add,
        .del            = vpa_pmu_del,
        .read           = vpa_pmu_read,
        .attr_groups    = vpa_pmu_attr_groups,
        .capabilities   = PERF_PMU_CAP_NO_EXCLUDE | PERF_PMU_CAP_NO_INTERRUPT,
};

static int __init pseries_vpa_pmu_init(void)
{
        /*
         * List of current Linux on Power platforms and
         * this driver is supported only in PowerVM LPAR
         * (L1) platform.
         *
         *      Enabled    Linux on Power Platforms
         *      ----------------------------------------
         *        [X]      PowerVM LPAR (L1)
         *        [ ]      KVM Guest On PowerVM KoP(L2)
         *        [ ]      Baremetal(PowerNV)
         *        [ ]      KVM Guest On PowerNV
         */
        if (!firmware_has_feature(FW_FEATURE_LPAR) || is_kvm_guest())
                return -ENODEV;

        perf_pmu_register(&vpa_pmu, vpa_pmu.name, -1);
        pr_info("Virtual Processor Area PMU registered.\n");

        return 0;
}

static void __exit pseries_vpa_pmu_cleanup(void)
{
        perf_pmu_unregister(&vpa_pmu);
        pr_info("Virtual Processor Area PMU unregistered.\n");
}

module_init(pseries_vpa_pmu_init);
module_exit(pseries_vpa_pmu_cleanup);
MODULE_DESCRIPTION("Perf Driver for pSeries VPA pmu counter");
MODULE_AUTHOR("Kajol Jain <kjain@linux.ibm.com>");
MODULE_AUTHOR("Madhavan Srinivasan <maddy@linux.ibm.com>");
MODULE_LICENSE("GPL");