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Subject[v6 1/9] RISC-V: Remove the current perf implementation
Date
From: Atish Patra <atish.patra@wdc.com>

The current perf implementation in RISC-V is not very useful as it can not
count any events other than cycle/instructions. Moreover, perf record
can not be used or the events can not be started or stopped.

Remove the implementation now for a better platform driver in future
that will implement most of the missing functionality.

Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
---
arch/riscv/Kconfig | 13 -
arch/riscv/include/asm/perf_event.h | 72 -----
arch/riscv/kernel/Makefile | 1 -
arch/riscv/kernel/perf_event.c | 485 ----------------------------
4 files changed, 571 deletions(-)
delete mode 100644 arch/riscv/kernel/perf_event.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 5adcbd9b5e88..00cc3d4c77d1 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -333,19 +333,6 @@ config RISCV_ISA_C

If you don't know what to do here, say Y.

-menu "supported 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. It can run on any RISC-V machines so serves as the
- fallback, but this option can also be disable to reduce kernel size.
-
-endmenu
-
config FPU
bool "FPU support"
default y
diff --git a/arch/riscv/include/asm/perf_event.h b/arch/riscv/include/asm/perf_event.h
index 062efd3a1d5d..d42c901f9a97 100644
--- a/arch/riscv/include/asm/perf_event.h
+++ b/arch/riscv/include/asm/perf_event.h
@@ -9,77 +9,5 @@
#define _ASM_RISCV_PERF_EVENT_H

#include <linux/perf_event.h>
-#include <linux/ptrace.h>
-#include <linux/interrupt.h>
-
-#ifdef CONFIG_RISCV_BASE_PMU
-#define RISCV_BASE_COUNTERS 2
-
-/*
- * The RISCV_MAX_COUNTERS parameter should be specified.
- */
-
-#define RISCV_MAX_COUNTERS 2
-
-/*
- * 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;
-
- irqreturn_t (*handle_irq)(int irq_num, void *dev);
- int irq;
-};
-
-#endif
-#ifdef CONFIG_PERF_EVENTS
#define perf_arch_bpf_user_pt_regs(regs) (struct user_regs_struct *)regs
-#endif
-
#endif /* _ASM_RISCV_PERF_EVENT_H */
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 612556faa527..fb63b462ff85 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -51,7 +51,6 @@ obj-$(CONFIG_MODULE_SECTIONS) += module-sections.o
obj-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace.o
obj-$(CONFIG_DYNAMIC_FTRACE) += mcount-dyn.o

-obj-$(CONFIG_RISCV_BASE_PMU) += perf_event.o
obj-$(CONFIG_PERF_EVENTS) += perf_callchain.o
obj-$(CONFIG_HAVE_PERF_REGS) += perf_regs.o
obj-$(CONFIG_RISCV_SBI) += sbi.o
diff --git a/arch/riscv/kernel/perf_event.c b/arch/riscv/kernel/perf_event.c
deleted file mode 100644
index c835f0362d94..000000000000
--- a/arch/riscv/kernel/perf_event.c
+++ /dev/null
@@ -1,485 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
- * 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@intel.com>
- * 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/perf_event.h>
-#include <linux/atomic.h>
-#include <linux/of.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];
-}
-
-static 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(CSR_CYCLE);
- break;
- case RISCV_PMU_INSTRET:
- val = csr_read(CSR_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 */
- WARN_ON_ONCE(1);
-}
-
-/*
- * 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->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->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->pmu->stop(event, PERF_EF_UPDATE);
- perf_event_update_userpage(event);
-}
-
-/*
- * Interrupt: a skeletion for reference.
- */
-
-static DEFINE_MUTEX(pmc_reserve_mutex);
-
-static irqreturn_t riscv_base_pmu_handle_irq(int irq_num, void *dev)
-{
- return IRQ_NONE;
-}
-
-static int reserve_pmc_hardware(void)
-{
- int err = 0;
-
- mutex_lock(&pmc_reserve_mutex);
- if (riscv_pmu->irq >= 0 && riscv_pmu->handle_irq) {
- err = request_irq(riscv_pmu->irq, riscv_pmu->handle_irq,
- IRQF_PERCPU, "riscv-base-perf", NULL);
- }
- mutex_unlock(&pmc_reserve_mutex);
-
- return err;
-}
-
-static void release_pmc_hardware(void)
-{
- mutex_lock(&pmc_reserve_mutex);
- if (riscv_pmu->irq >= 0)
- free_irq(riscv_pmu->irq, NULL);
- mutex_unlock(&pmc_reserve_mutex);
-}
-
-/*
- * Event Initialization/Finalization
- */
-
-static atomic_t riscv_active_events = ATOMIC_INIT(0);
-
-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;
- int err;
- int code;
-
- if (atomic_inc_return(&riscv_active_events) == 1) {
- err = reserve_pmc_hardware();
-
- if (err) {
- pr_warn("PMC hardware not available\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,
- .handle_irq = &riscv_base_pmu_handle_irq,
-
- /* This means this PMU has no IRQ. */
- .irq = -1,
-};
-
-static const struct of_device_id riscv_pmu_of_ids[] = {
- {.compatible = "riscv,base-pmu", .data = &riscv_base_pmu},
- { /* sentinel value */ }
-};
-
-static int __init init_hw_perf_events(void)
-{
- struct device_node *node = of_find_node_by_type(NULL, "pmu");
- const struct of_device_id *of_id;
-
- riscv_pmu = &riscv_base_pmu;
-
- if (node) {
- of_id = of_match_node(riscv_pmu_of_ids, node);
-
- if (of_id)
- riscv_pmu = of_id->data;
- of_node_put(node);
- }
-
- perf_pmu_register(riscv_pmu->pmu, "cpu", PERF_TYPE_RAW);
- return 0;
-}
-arch_initcall(init_hw_perf_events);
--
2.30.2
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