Re: [PATCH v2 1/2] perf: riscv: preliminary RISC-V support

[Alex Solomatnikov]

This works for cycle and instruction counts.

Alex

On Mon, Apr 2, 2018 at 5:31 AM, Alan Kao <alankao@xxxxxxxxxxxxx> wrote:
>
> This patch provide a basic PMU, riscv_base_pmu, which supports two
> general hardware event, instructions and cycles.  Furthermore, this
> PMU serves as a reference implementation to ease the portings in
> the future.
>
> riscv_base_pmu should be able to run on any RISC-V machine that
> conforms to the Priv-Spec.  Note that the latest qemu model hasn't
> fully support a proper behavior of Priv-Spec 1.10 yet, but work
> around should be easy with very small fixes.  Please check
> https://github.com/riscv/riscv-qemu/pull/115 for future updates.
>
> Cc: Nick Hu <nickhu@xxxxxxxxxxxxx>
> Cc: Greentime Hu <greentime@xxxxxxxxxxxxx>
> Signed-off-by: Alan Kao <alankao@xxxxxxxxxxxxx>
> ---
>  arch/riscv/Kconfig                  |  12 +
>  arch/riscv/include/asm/perf_event.h |  76 +++++-
>  arch/riscv/kernel/Makefile          |   1 +
>  arch/riscv/kernel/perf_event.c      | 468 ++++++++++++++++++++++++++++++++++++
>  4 files changed, 553 insertions(+), 4 deletions(-)
>  create mode 100644 arch/riscv/kernel/perf_event.c
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index c22ebe08e902..3fbf19456c9a 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -203,6 +203,18 @@ config RISCV_ISA_C
>  config RISCV_ISA_A
>         def_bool y
>
> +menu "PMU type"
> +       depends on PERF_EVENTS
> +
> +config RISCV_BASE_PMU
> +       bool "Base Performance Monitoring Unit"
> +       def_bool y
> +       help
> +         A base PMU that serves as a reference implementation and has limited
> +         feature of perf.
> +
> +endmenu
> +
>  endmenu
>
>  menu "Kernel type"
> diff --git a/arch/riscv/include/asm/perf_event.h b/arch/riscv/include/asm/perf_event.h
> index e13d2ff29e83..98e2efb02d25 100644
> --- a/arch/riscv/include/asm/perf_event.h
> +++ b/arch/riscv/include/asm/perf_event.h
> @@ -1,13 +1,81 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
>  /*
>   * Copyright (C) 2018 SiFive
> + * Copyright (C) 2018 Andes Technology Corporation
>   *
> - * This program is free software; you can redistribute it and/or
> - * modify it under the terms of the GNU General Public Licence
> - * as published by the Free Software Foundation; either version
> - * 2 of the Licence, or (at your option) any later version.
>   */
>
>  #ifndef _ASM_RISCV_PERF_EVENT_H
>  #define _ASM_RISCV_PERF_EVENT_H
>
> +#include <linux/perf_event.h>
> +#include <linux/ptrace.h>
> +
> +#define RISCV_BASE_COUNTERS    2
> +
> +/*
> + * The RISCV_MAX_COUNTERS parameter should be specified.
> + */
> +
> +#ifdef CONFIG_RISCV_BASE_PMU
> +#define RISCV_MAX_COUNTERS     2
> +#endif
> +
> +#ifndef RISCV_MAX_COUNTERS
> +#error "Please provide a valid RISCV_MAX_COUNTERS for the PMU."
> +#endif
> +
> +/*
> + * These are the indexes of bits in counteren register *minus* 1,
> + * except for cycle.  It would be coherent if it can directly mapped
> + * to counteren bit definition, but there is a *time* register at
> + * counteren[1].  Per-cpu structure is scarce resource here.
> + *
> + * According to the spec, an implementation can support counter up to
> + * mhpmcounter31, but many high-end processors has at most 6 general
> + * PMCs, we give the definition to MHPMCOUNTER8 here.
> + */
> +#define RISCV_PMU_CYCLE                0
> +#define RISCV_PMU_INSTRET      1
> +#define RISCV_PMU_MHPMCOUNTER3 2
> +#define RISCV_PMU_MHPMCOUNTER4 3
> +#define RISCV_PMU_MHPMCOUNTER5 4
> +#define RISCV_PMU_MHPMCOUNTER6 5
> +#define RISCV_PMU_MHPMCOUNTER7 6
> +#define RISCV_PMU_MHPMCOUNTER8 7
> +
> +#define RISCV_OP_UNSUPP                (-EOPNOTSUPP)
> +
> +struct cpu_hw_events {
> +       /* # currently enabled events*/
> +       int                     n_events;
> +       /* currently enabled events */
> +       struct perf_event       *events[RISCV_MAX_COUNTERS];
> +       /* vendor-defined PMU data */
> +       void                    *platform;
> +};
> +
> +struct riscv_pmu {
> +       struct pmu      *pmu;
> +
> +       /* generic hw/cache events table */
> +       const int       *hw_events;
> +       const int       (*cache_events)[PERF_COUNT_HW_CACHE_MAX]
> +                                      [PERF_COUNT_HW_CACHE_OP_MAX]
> +                                      [PERF_COUNT_HW_CACHE_RESULT_MAX];
> +       /* method used to map hw/cache events */
> +       int             (*map_hw_event)(u64 config);
> +       int             (*map_cache_event)(u64 config);
> +
> +       /* max generic hw events in map */
> +       int             max_events;
> +       /* number total counters, 2(base) + x(general) */
> +       int             num_counters;
> +       /* the width of the counter */
> +       int             counter_width;
> +
> +       /* vendor-defined PMU features */
> +       void            *platform;
> +};
> +
>  #endif /* _ASM_RISCV_PERF_EVENT_H */
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index ffa439d4a364..f50d19816757 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -39,5 +39,6 @@ obj-$(CONFIG_MODULE_SECTIONS) += module-sections.o
>  obj-$(CONFIG_FUNCTION_TRACER)  += mcount.o
>  obj-$(CONFIG_DYNAMIC_FTRACE)   += mcount-dyn.o
>  obj-$(CONFIG_FUNCTION_GRAPH_TRACER)    += ftrace.o
> +obj-$(CONFIG_PERF_EVENTS)      += perf_event.o
>
>  clean:
> diff --git a/arch/riscv/kernel/perf_event.c b/arch/riscv/kernel/perf_event.c
> new file mode 100644
> index 000000000000..cac4abd0a884
> --- /dev/null
> +++ b/arch/riscv/kernel/perf_event.c
> @@ -0,0 +1,468 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2008 Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> + * 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
> + * Copyright (C) 2009 Intel Corporation, <markus.t.metzger@xxxxxxxxx>
> + * Copyright (C) 2009 Google, Inc., Stephane Eranian
> + * Copyright 2014 Tilera Corporation. All Rights Reserved.
> + * Copyright (C) 2018 Andes Technology Corporation
> + *
> + * Perf_events support for RISC-V platforms.
> + *
> + * Since the spec. (as of now, Priv-Spec 1.10) does not provide enough
> + * functionality for perf event to fully work, this file provides
> + * the very basic framework only.
> + *
> + * For platform portings, please check Documentations/riscv/pmu.txt.
> + *
> + * The Copyright line includes x86 and tile ones.
> + */
> +
> +#include <linux/kprobes.h>
> +#include <linux/kernel.h>
> +#include <linux/kdebug.h>
> +#include <linux/mutex.h>
> +#include <linux/bitmap.h>
> +#include <linux/irq.h>
> +#include <linux/interrupt.h>
> +#include <linux/perf_event.h>
> +#include <linux/atomic.h>
> +#include <asm/perf_event.h>
> +
> +static const struct riscv_pmu *riscv_pmu __read_mostly;
> +static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events);
> +
> +/*
> + * Hardware & cache maps and their methods
> + */
> +
> +static const int riscv_hw_event_map[] = {
> +       [PERF_COUNT_HW_CPU_CYCLES]              = RISCV_PMU_CYCLE,
> +       [PERF_COUNT_HW_INSTRUCTIONS]            = RISCV_PMU_INSTRET,
> +       [PERF_COUNT_HW_CACHE_REFERENCES]        = RISCV_OP_UNSUPP,
> +       [PERF_COUNT_HW_CACHE_MISSES]            = RISCV_OP_UNSUPP,
> +       [PERF_COUNT_HW_BRANCH_INSTRUCTIONS]     = RISCV_OP_UNSUPP,
> +       [PERF_COUNT_HW_BRANCH_MISSES]           = RISCV_OP_UNSUPP,
> +       [PERF_COUNT_HW_BUS_CYCLES]              = RISCV_OP_UNSUPP,
> +};
> +
> +#define C(x) PERF_COUNT_HW_CACHE_##x
> +static const int riscv_cache_event_map[PERF_COUNT_HW_CACHE_MAX]
> +[PERF_COUNT_HW_CACHE_OP_MAX]
> +[PERF_COUNT_HW_CACHE_RESULT_MAX] = {
> +       [C(L1D)] = {
> +               [C(OP_READ)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_WRITE)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_PREFETCH)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +       },
> +       [C(L1I)] = {
> +               [C(OP_READ)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_WRITE)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_PREFETCH)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +       },
> +       [C(LL)] = {
> +               [C(OP_READ)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_WRITE)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_PREFETCH)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +       },
> +       [C(DTLB)] = {
> +               [C(OP_READ)] = {
> +                       [C(RESULT_ACCESS)] =  RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] =  RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_WRITE)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_PREFETCH)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +       },
> +       [C(ITLB)] = {
> +               [C(OP_READ)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_WRITE)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_PREFETCH)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +       },
> +       [C(BPU)] = {
> +               [C(OP_READ)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_WRITE)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +               [C(OP_PREFETCH)] = {
> +                       [C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +                       [C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +               },
> +       },
> +};
> +
> +static int riscv_map_hw_event(u64 config)
> +{
> +       if (config >= riscv_pmu->max_events)
> +               return -EINVAL;
> +
> +       return riscv_pmu->hw_events[config];
> +}
> +
> +int riscv_map_cache_decode(u64 config, unsigned int *type,
> +                          unsigned int *op, unsigned int *result)
> +{
> +       return -ENOENT;
> +}
> +
> +static int riscv_map_cache_event(u64 config)
> +{
> +       unsigned int type, op, result;
> +       int err = -ENOENT;
> +               int code;
> +
> +       err = riscv_map_cache_decode(config, &type, &op, &result);
> +       if (!riscv_pmu->cache_events || err)
> +               return err;
> +
> +       if (type >= PERF_COUNT_HW_CACHE_MAX ||
> +           op >= PERF_COUNT_HW_CACHE_OP_MAX ||
> +           result >= PERF_COUNT_HW_CACHE_RESULT_MAX)
> +               return -EINVAL;
> +
> +       code = (*riscv_pmu->cache_events)[type][op][result];
> +       if (code == RISCV_OP_UNSUPP)
> +               return -EINVAL;
> +
> +       return code;
> +}
> +
> +/*
> + * Low-level functions: reading/writing counters
> + */
> +
> +static inline u64 read_counter(int idx)
> +{
> +       u64 val = 0;
> +
> +       switch (idx) {
> +       case RISCV_PMU_CYCLE:
> +               val = csr_read(cycle);
> +               break;
> +       case RISCV_PMU_INSTRET:
> +               val = csr_read(instret);
> +               break;
> +       default:
> +               WARN_ON_ONCE(idx < 0 || idx > RISCV_MAX_COUNTERS);
> +               return -EINVAL;
> +       }
> +
> +       return val;
> +}
> +
> +static inline void write_counter(int idx, u64 value)
> +{
> +       /* currently not supported */
> +}
> +
> +/*
> + * pmu->read: read and update the counter
> + *
> + * Other architectures' implementation often have a xxx_perf_event_update
> + * routine, which can return counter values when called in the IRQ, but
> + * return void when being called by the pmu->read method.
> + */
> +static void riscv_pmu_read(struct perf_event *event)
> +{
> +       struct hw_perf_event *hwc = &event->hw;
> +       u64 prev_raw_count, new_raw_count;
> +       u64 oldval;
> +       int idx = hwc->idx;
> +       u64 delta;
> +
> +       do {
> +               prev_raw_count = local64_read(&hwc->prev_count);
> +               new_raw_count = read_counter(idx);
> +
> +               oldval = local64_cmpxchg(&hwc->prev_count, prev_raw_count,
> +                                        new_raw_count);
> +       } while (oldval != prev_raw_count);
> +
> +       /*
> +        * delta is the value to update the counter we maintain in the kernel.
> +        */
> +       delta = (new_raw_count - prev_raw_count) &
> +               ((1ULL << riscv_pmu->counter_width) - 1);
> +       local64_add(delta, &event->count);
> +       /*
> +        * Something like local64_sub(delta, &hwc->period_left) here is
> +        * needed if there is an interrupt for perf.
> +        */
> +}
> +
> +/*
> + * State transition functions:
> + *
> + * stop()/start() & add()/del()
> + */
> +
> +/*
> + * pmu->stop: stop the counter
> + */
> +static void riscv_pmu_stop(struct perf_event *event, int flags)
> +{
> +       struct hw_perf_event *hwc = &event->hw;
> +
> +       WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
> +       hwc->state |= PERF_HES_STOPPED;
> +
> +       if ((flags & PERF_EF_UPDATE) && !(hwc->state & PERF_HES_UPTODATE)) {
> +               riscv_pmu_read(event);
> +               hwc->state |= PERF_HES_UPTODATE;
> +       }
> +}
> +
> +/*
> + * pmu->start: start the event.
> + */
> +static void riscv_pmu_start(struct perf_event *event, int flags)
> +{
> +       struct hw_perf_event *hwc = &event->hw;
> +
> +       if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
> +               return;
> +
> +       if (flags & PERF_EF_RELOAD) {
> +               WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));
> +
> +               /*
> +                * Set the counter to the period to the next interrupt here,
> +                * if you have any.
> +                */
> +       }
> +
> +       hwc->state = 0;
> +       perf_event_update_userpage(event);
> +
> +       /*
> +        * Since we cannot write to counters, this serves as an initialization
> +        * to the delta-mechanism in pmu->read(); otherwise, the delta would be
> +        * wrong when pmu->read is called for the first time.
> +        */
> +       local64_set(&hwc->prev_count, read_counter(hwc->idx));
> +}
> +
> +/*
> + * pmu->add: add the event to PMU.
> + */
> +static int riscv_pmu_add(struct perf_event *event, int flags)
> +{
> +       struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> +       struct hw_perf_event *hwc = &event->hw;
> +
> +       if (cpuc->n_events == riscv_pmu->num_counters)
> +               return -ENOSPC;
> +
> +       /*
> +        * We don't have general conunters, so no binding-event-to-counter
> +        * process here.
> +        *
> +        * Indexing using hwc->config generally not works, since config may
> +        * contain extra information, but here the only info we have in
> +        * hwc->config is the event index.
> +        */
> +       hwc->idx = hwc->config;
> +       cpuc->events[hwc->idx] = event;
> +       cpuc->n_events++;
> +
> +       hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
> +
> +       if (flags & PERF_EF_START)
> +               riscv_pmu_start(event, PERF_EF_RELOAD);
> +
> +       return 0;
> +}
> +
> +/*
> + * pmu->del: delete the event from PMU.
> + */
> +static void riscv_pmu_del(struct perf_event *event, int flags)
> +{
> +       struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> +       struct hw_perf_event *hwc = &event->hw;
> +
> +       cpuc->events[hwc->idx] = NULL;
> +       cpuc->n_events--;
> +       riscv_pmu_stop(event, PERF_EF_UPDATE);
> +       perf_event_update_userpage(event);
> +}
> +
> +/*
> + * Interrupt
> + */
> +
> +static DEFINE_MUTEX(pmc_reserve_mutex);
> +typedef void (*perf_irq_t)(void *riscv_perf_irq);
> +perf_irq_t perf_irq;
> +
> +void riscv_pmu_handle_irq(void *riscv_perf_irq)
> +{
> +}
> +
> +static perf_irq_t reserve_pmc_hardware(void)
> +{
> +       perf_irq_t old;
> +
> +       mutex_lock(&pmc_reserve_mutex);
> +       old = perf_irq;
> +       perf_irq = &riscv_pmu_handle_irq;
> +       mutex_unlock(&pmc_reserve_mutex);
> +
> +       return old;
> +}
> +
> +void release_pmc_hardware(void)
> +{
> +       mutex_lock(&pmc_reserve_mutex);
> +       perf_irq = NULL;
> +       mutex_unlock(&pmc_reserve_mutex);
> +}
> +
> +/*
> + * Event Initialization
> + */
> +
> +static atomic_t riscv_active_events;
> +
> +static void riscv_event_destroy(struct perf_event *event)
> +{
> +       if (atomic_dec_return(&riscv_active_events) == 0)
> +               release_pmc_hardware();
> +}
> +
> +static int riscv_event_init(struct perf_event *event)
> +{
> +       struct perf_event_attr *attr = &event->attr;
> +       struct hw_perf_event *hwc = &event->hw;
> +       perf_irq_t old_irq_handler = NULL;
> +       int code;
> +
> +       if (atomic_inc_return(&riscv_active_events) == 1)
> +               old_irq_handler = reserve_pmc_hardware();
> +
> +       if (old_irq_handler) {
> +               pr_warn("PMC hardware busy (reserved by oprofile)\n");
> +               atomic_dec(&riscv_active_events);
> +               return -EBUSY;
> +       }
> +
> +       switch (event->attr.type) {
> +       case PERF_TYPE_HARDWARE:
> +               code = riscv_pmu->map_hw_event(attr->config);
> +               break;
> +       case PERF_TYPE_HW_CACHE:
> +               code = riscv_pmu->map_cache_event(attr->config);
> +               break;
> +       case PERF_TYPE_RAW:
> +               return -EOPNOTSUPP;
> +       default:
> +               return -ENOENT;
> +       }
> +
> +       event->destroy = riscv_event_destroy;
> +       if (code < 0) {
> +               event->destroy(event);
> +               return code;
> +       }
> +
> +       /*
> +        * idx is set to -1 because the index of a general event should not be
> +        * decided until binding to some counter in pmu->add().
> +        *
> +        * But since we don't have such support, later in pmu->add(), we just
> +        * use hwc->config as the index instead.
> +        */
> +       hwc->config = code;
> +       hwc->idx = -1;
> +
> +       return 0;
> +}
> +
> +/*
> + * Initialization
> + */
> +
> +static struct pmu min_pmu = {
> +       .name           = "riscv-base",
> +       .event_init     = riscv_event_init,
> +       .add            = riscv_pmu_add,
> +       .del            = riscv_pmu_del,
> +       .start          = riscv_pmu_start,
> +       .stop           = riscv_pmu_stop,
> +       .read           = riscv_pmu_read,
> +};
> +
> +static const struct riscv_pmu riscv_base_pmu = {
> +       .pmu = &min_pmu,
> +       .max_events = ARRAY_SIZE(riscv_hw_event_map),
> +       .map_hw_event = riscv_map_hw_event,
> +       .hw_events = riscv_hw_event_map,
> +       .map_cache_event = riscv_map_cache_event,
> +       .cache_events = &riscv_cache_event_map,
> +       .counter_width = 63,
> +       .num_counters = RISCV_BASE_COUNTERS + 0,
> +};
> +
> +struct pmu * __weak __init riscv_init_platform_pmu(void)
> +{
> +       riscv_pmu = &riscv_base_pmu;
> +       return riscv_pmu->pmu;
> +}
> +
> +int __init init_hw_perf_events(void)
> +{
> +       struct pmu *pmu = riscv_init_platform_pmu();
> +
> +       perf_irq = NULL;
> +       perf_pmu_register(pmu, "cpu", PERF_TYPE_RAW);
> +       return 0;
> +}
> +arch_initcall(init_hw_perf_events);
> --
> 2.16.2
>