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References: <20220815124702.3330803-1-chenhuacai@loongson.cn> <53074d4d-b895-0afa-696e-c9358a07e109@xen0n.name>
In-Reply-To: <53074d4d-b895-0afa-696e-c9358a07e109@xen0n.name>
From:   Huacai Chen <chenhuacai@kernel.org>
Date:   Tue, 16 Aug 2022 16:18:17 +0800
Message-ID: <CAAhV-H6WzUWs1944=71aduQ1Whz6kcSAF0XWbPuDin6mx0T5hA@mail.gmail.com>
Subject: Re: [PATCH] LoongArch: Add perf events support
To:     WANG Xuerui <kernel@xen0n.name>
Cc:     Huacai Chen <chenhuacai@loongson.cn>,
        Arnd Bergmann <arnd@arndb.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>, loongarch@lists.linux.dev,
        linux-arch <linux-arch@vger.kernel.org>,
        Xuefeng Li <lixuefeng@loongson.cn>,
        Guo Ren <guoren@kernel.org>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        linux-perf-users@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

 Hi, Xuerui,

On Tue, Aug 16, 2022 at 1:46 PM WANG Xuerui <kernel@xen0n.name> wrote:
>
> On 2022/8/15 20:47, Huacai Chen wrote:
> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > ---
> >   arch/loongarch/Kconfig                      |   2 +
> >   arch/loongarch/include/uapi/asm/perf_regs.h |  40 +
> >   arch/loongarch/kernel/Makefile              |   2 +
> >   arch/loongarch/kernel/perf_event.c          | 909 ++++++++++++++++++++
> >   arch/loongarch/kernel/perf_regs.c           |  50 ++
> >   5 files changed, 1003 insertions(+)
> >   create mode 100644 arch/loongarch/include/uapi/asm/perf_regs.h
> >   create mode 100644 arch/loongarch/kernel/perf_event.c
> >   create mode 100644 arch/loongarch/kernel/perf_regs.c
>
> The code seems mostly ripped from arch/mips/kernel/perf_event_mipsxx.c.
> I reviewed about half of the code then suddenly realized I might be
> looking at MIPS code, given some of the English strings there seemed way
> too "natural"...
>
> But unfortunately, at least for 3A5000 whose micro-architecture is
> largely shared with the MIPS-implementing 3A4000, it seems inevitable to
> involve some of the more MIPS-looking logic. The 1st-generation LA
> privileged architecture is way too much MIPS-like after all, so if we
> want any support for the 3A5000 we'd have to include this.
>
> >
> > diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> > index 24665808cf3d..9478f9646fa5 100644
> > --- a/arch/loongarch/Kconfig
> > +++ b/arch/loongarch/Kconfig
> > @@ -93,6 +93,8 @@ config LOONGARCH
> >       select HAVE_NMI
> >       select HAVE_PCI
> >       select HAVE_PERF_EVENTS
> > +     select HAVE_PERF_REGS
> > +     select HAVE_PERF_USER_STACK_DUMP
> >       select HAVE_REGS_AND_STACK_ACCESS_API
> >       select HAVE_RSEQ
> >       select HAVE_SETUP_PER_CPU_AREA if NUMA
> > diff --git a/arch/loongarch/include/uapi/asm/perf_regs.h b/arch/loongarch/include/uapi/asm/perf_regs.h
> > new file mode 100644
> > index 000000000000..9943d418e01d
> > --- /dev/null
> > +++ b/arch/loongarch/include/uapi/asm/perf_regs.h
> > @@ -0,0 +1,40 @@
> > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > +#ifndef _ASM_LOONGARCH_PERF_REGS_H
> > +#define _ASM_LOONGARCH_PERF_REGS_H
> > +
> > +enum perf_event_loongarch_regs {
> > +     PERF_REG_LOONGARCH_PC,
> > +     PERF_REG_LOONGARCH_R1,
> > +     PERF_REG_LOONGARCH_R2,
> > +     PERF_REG_LOONGARCH_R3,
> > +     PERF_REG_LOONGARCH_R4,
> > +     PERF_REG_LOONGARCH_R5,
> > +     PERF_REG_LOONGARCH_R6,
> > +     PERF_REG_LOONGARCH_R7,
> > +     PERF_REG_LOONGARCH_R8,
> > +     PERF_REG_LOONGARCH_R9,
> > +     PERF_REG_LOONGARCH_R10,
> > +     PERF_REG_LOONGARCH_R11,
> > +     PERF_REG_LOONGARCH_R12,
> > +     PERF_REG_LOONGARCH_R13,
> > +     PERF_REG_LOONGARCH_R14,
> > +     PERF_REG_LOONGARCH_R15,
> > +     PERF_REG_LOONGARCH_R16,
> > +     PERF_REG_LOONGARCH_R17,
> > +     PERF_REG_LOONGARCH_R18,
> > +     PERF_REG_LOONGARCH_R19,
> > +     PERF_REG_LOONGARCH_R20,
> > +     PERF_REG_LOONGARCH_R21,
> > +     PERF_REG_LOONGARCH_R22,
> > +     PERF_REG_LOONGARCH_R23,
> > +     PERF_REG_LOONGARCH_R24,
> > +     PERF_REG_LOONGARCH_R25,
> > +     PERF_REG_LOONGARCH_R26,
> > +     PERF_REG_LOONGARCH_R27,
> > +     PERF_REG_LOONGARCH_R28,
> > +     PERF_REG_LOONGARCH_R29,
> > +     PERF_REG_LOONGARCH_R30,
> > +     PERF_REG_LOONGARCH_R31,
> > +     PERF_REG_LOONGARCH_MAX = PERF_REG_LOONGARCH_R31 + 1,
>
> No need for this "PERF_REG_LOONGARCH_R31 + 1" because it's what happens
> without the assignment anyway?
PERF_REG_LOONGARCH_MAX is used in perf_events.c

>
> > +};
> > +#endif /* _ASM_LOONGARCH_PERF_REGS_H */
> > diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> > index e5be17009fe8..a213e994db68 100644
> > --- a/arch/loongarch/kernel/Makefile
> > +++ b/arch/loongarch/kernel/Makefile
> > @@ -26,4 +26,6 @@ obj-$(CONFIG_NUMA)          += numa.o
> >   obj-$(CONFIG_UNWINDER_GUESS)        += unwind_guess.o
> >   obj-$(CONFIG_UNWINDER_PROLOGUE) += unwind_prologue.o
> >
> > +obj-$(CONFIG_PERF_EVENTS)    += perf_event.o perf_regs.o
> > +
> >   CPPFLAGS_vmlinux.lds                := $(KBUILD_CFLAGS)
> > diff --git a/arch/loongarch/kernel/perf_event.c b/arch/loongarch/kernel/perf_event.c
> > new file mode 100644
> > index 000000000000..00cdbcebaf80
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/perf_event.c
> > @@ -0,0 +1,909 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Linux performance counter support for LoongArch.
>
> Please indicate its MIPS origin and copyright info ;-)
OK, thanks.

>
> > + *
> > + * Copyright (C) 2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#include <linux/cpumask.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/smp.h>
> > +#include <linux/kernel.h>
> > +#include <linux/perf_event.h>
> > +#include <linux/uaccess.h>
> > +#include <linux/sched/task_stack.h>
> > +
> > +#include <asm/irq.h>
> > +#include <asm/irq_regs.h>
> > +#include <asm/stacktrace.h>
> > +#include <asm/unwind.h>
> > +
> > +/*
> > + * Get the return address for a single stackframe and return a pointer to the
> > + * next frame tail.
> > + */
> > +static unsigned long
> > +user_backtrace(struct perf_callchain_entry_ctx *entry, unsigned long fp)
> > +{
> > +     struct stack_frame buftail;
> > +     unsigned long err;
> > +     unsigned long __user *user_frame_tail = (unsigned long *)(fp - sizeof(struct stack_frame));
> > +
> > +     /* Also check accessibility of one struct frame_tail beyond */
> > +     if (!access_ok(user_frame_tail, sizeof(buftail)))
> > +             return 0;
> > +
> > +     pagefault_disable();
> > +     err = __copy_from_user_inatomic(&buftail, user_frame_tail, sizeof(buftail));
> > +     pagefault_enable();
> > +
> > +     if (err || (unsigned long)user_frame_tail >= buftail.fp)
> > +             return 0;
> > +
> > +     perf_callchain_store(entry, buftail.ra);
> > +
> > +     return buftail.fp;
> > +}
> > +
> > +void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
> > +                      struct pt_regs *regs)
> > +{
> > +     unsigned long fp;
> > +
> > +     if (perf_guest_state()) {
> > +             /* We don't support guest os callchain now */
> > +             return;
> > +     }
> > +
> > +     perf_callchain_store(entry, regs->csr_era);
> > +
> > +     fp = regs->regs[22];
> > +
> > +     while (entry->nr < entry->max_stack && fp && !((unsigned long)fp & 0xf))
> > +             fp = user_backtrace(entry, fp);
> > +}
> > +
> > +void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
> > +                        struct pt_regs *regs)
> > +{
> > +     struct unwind_state state;
> > +     unsigned long addr;
> > +
> > +     for (unwind_start(&state, current, regs);
> > +           !unwind_done(&state); unwind_next_frame(&state)) {
> > +             addr = unwind_get_return_address(&state);
> > +             if (!addr || perf_callchain_store(entry, addr))
> > +                     return;
> > +     }
> > +}
> > +
> > +#define LOONGARCH_MAX_HWEVENTS 4
> > +
> > +struct cpu_hw_events {
> > +     /* Array of events on this cpu. */
> > +     struct perf_event       *events[LOONGARCH_MAX_HWEVENTS];
> > +
> > +     /*
> > +      * Set the bit (indexed by the counter number) when the counter
> > +      * is used for an event.
> > +      */
> > +     unsigned long           used_mask[BITS_TO_LONGS(LOONGARCH_MAX_HWEVENTS)];
> > +
> > +     /*
> > +      * Software copy of the control register for each performance counter.
> > +      * LoongArch CPUs vary in performance counters. They use this differently,
> > +      * and even may not use it.
>
> I can't easily make sense of the paragraph. "Software copy" could mean
> "Saved copy", but how do "use differently" and "even may not use it"
> mean? For the latter I can't deduce if it's originally "some even may
> not exist" in someone's head, and for the former I can't imagine what's
> the possible cases and why we would care.
>
> Maybe explain a little bit more?
I think we should remove those useless lines.

>
> > +      */
> > +     unsigned int            saved_ctrl[LOONGARCH_MAX_HWEVENTS];
> > +};
> > +static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events) = {
> > +     .saved_ctrl = {0},
> > +};
> > +
> > +/* The description of LoongArch performance events. */
> > +struct loongarch_perf_event {
> > +     unsigned int event_id;
> > +};
> > +
> > +static struct loongarch_perf_event raw_event;
> > +static DEFINE_MUTEX(raw_event_mutex);
> > +
> > +#define C(x) PERF_COUNT_HW_CACHE_##x
> > +#define HW_OP_UNSUPPORTED            0xffffffff
> > +#define CACHE_OP_UNSUPPORTED         0xffffffff
> > +
> > +#define PERF_MAP_ALL_UNSUPPORTED                                     \
> > +     [0 ... PERF_COUNT_HW_MAX - 1] = {HW_OP_UNSUPPORTED}
> > +
> > +#define PERF_CACHE_MAP_ALL_UNSUPPORTED                                       \
> > +[0 ... C(MAX) - 1] = {                                                       \
> > +     [0 ... C(OP_MAX) - 1] = {                                       \
> > +             [0 ... C(RESULT_MAX) - 1] = {CACHE_OP_UNSUPPORTED},     \
> > +     },                                                              \
> > +}
> > +
> > +struct loongarch_pmu {
> > +     u64             max_period;
> > +     u64             valid_count;
> > +     u64             overflow;
> > +     const char      *name;
> > +     u64             (*read_counter)(unsigned int idx);
> > +     void            (*write_counter)(unsigned int idx, u64 val);
> > +     const struct loongarch_perf_event *(*map_raw_event)(u64 config);
> > +     const struct loongarch_perf_event (*general_event_map)[PERF_COUNT_HW_MAX];
> > +     const struct loongarch_perf_event (*cache_event_map)
> > +                             [PERF_COUNT_HW_CACHE_MAX]
> > +                             [PERF_COUNT_HW_CACHE_OP_MAX]
> > +                             [PERF_COUNT_HW_CACHE_RESULT_MAX];
>
> Apparently general_event_map and cache_event_map are not function
> pointers? So the parens around the field name should be removed.
They are not function pointers, but "array pointers", but we shouldn't
change them to "array to pointers"..

>
> > +     unsigned int    num_counters;
> > +};
> > +
> > +static struct loongarch_pmu loongarch_pmu;
> > +
> > +#define M_PERFCTL_EVENT(event)       (event & CSR_PERFCTRL_EVENT)
> > +
> > +#define M_PERFCTL_COUNT_EVENT_WHENEVER       (CSR_PERFCTRL_PLV0 |    \
> > +                                     CSR_PERFCTRL_PLV1 |     \
> > +                                     CSR_PERFCTRL_PLV2 |     \
> > +                                     CSR_PERFCTRL_PLV3 |     \
> > +                                     CSR_PERFCTRL_IE)
> > +
> > +#define M_PERFCTL_CONFIG_MASK                0x1f0000
> > +
> > +#define CNTR_BIT_MASK(n)     (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
>
> Isn't this just GENMASK(n - 1, 0)?
Yes, you are right.

>
> > +
> > +static void resume_local_counters(void);
> > +static void pause_local_counters(void);
> > +
> > +static u64 loongarch_pmu_read_counter(unsigned int idx)
> > +{
> > +     u64 val = -1;
> > +
> > +     switch (idx) {
> > +     case 0:
> > +             val = read_csr_perfcntr0();
> > +             break;
> > +     case 1:
> > +             val = read_csr_perfcntr1();
> > +             break;
> > +     case 2:
> > +             val = read_csr_perfcntr2();
> > +             break;
> > +     case 3:
> > +             val = read_csr_perfcntr3();
> > +             break;
> > +     default:
> > +             WARN_ONCE(1, "Invalid performance counter number (%d)\n", idx);
> > +             return 0;
> > +     }
> > +
> > +     return val;
> > +}
> > +
> > +static void loongarch_pmu_write_counter(unsigned int idx, u64 val)
> > +{
> > +     switch (idx) {
> > +     case 0:
> > +             write_csr_perfcntr0(val);
> > +             return;
> > +     case 1:
> > +             write_csr_perfcntr1(val);
> > +             return;
> > +     case 2:
> > +             write_csr_perfcntr2(val);
> > +             return;
> > +     case 3:
> > +             write_csr_perfcntr3(val);
> > +             return;
>
> Want a default branch for this function, similar to the read case?
Yes, that is needed.

>
> > +     }
> > +}
> > +
> > +static unsigned int loongarch_pmu_read_control(unsigned int idx)
> > +{
> > +     unsigned int val = -1;
> > +
> > +     switch (idx) {
> > +     case 0:
> > +             val = read_csr_perfctrl0();
> > +             break;
> > +     case 1:
> > +             val = read_csr_perfctrl1();
> > +             break;
> > +     case 2:
> > +             val = read_csr_perfctrl2();
> > +             break;
> > +     case 3:
> > +             val = read_csr_perfctrl3();
> > +             break;
> > +     default:
> > +             WARN_ONCE(1, "Invalid performance counter number (%d)\n", idx);
> > +             return 0;
> > +     }
> > +
> > +     return val;
> > +}
> > +
> > +static void loongarch_pmu_write_control(unsigned int idx, unsigned int val)
> > +{
> > +     switch (idx) {
> > +     case 0:
> > +             write_csr_perfctrl0(val);
> > +             return;
> > +     case 1:
> > +             write_csr_perfctrl1(val);
> > +             return;
> > +     case 2:
> > +             write_csr_perfctrl2(val);
> > +             return;
> > +     case 3:
> > +             write_csr_perfctrl3(val);
> > +             return;
>
> Similarly here.
>
> > +     }
> > +}
> > +
> > +static int loongarch_pmu_alloc_counter(struct cpu_hw_events *cpuc,
> > +                                 struct hw_perf_event *hwc)
> > +{
> > +     int i;
> > +
> > +     for (i = loongarch_pmu.num_counters - 1; i >= 0; i--) {
> > +             if (!test_and_set_bit(i, cpuc->used_mask))
> > +                     return i;
> > +     }
> > +
> > +     return -EAGAIN;
> > +}
> > +
> > +static void loongarch_pmu_enable_event(struct hw_perf_event *evt, int idx)
> > +{
> > +     struct perf_event *event = container_of(evt, struct perf_event, hw);
> > +     struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> > +     unsigned int cpu;
> > +
> > +     WARN_ON(idx < 0 || idx >= loongarch_pmu.num_counters);
> > +
> > +     cpuc->saved_ctrl[idx] = M_PERFCTL_EVENT(evt->event_base & 0xff) |
> > +             (evt->config_base & M_PERFCTL_CONFIG_MASK) |
> > +             /* Make sure interrupt enabled. */
> > +             CSR_PERFCTRL_IE;
> > +
> > +     cpu = (event->cpu >= 0) ? event->cpu : smp_processor_id();
> > +
> > +     pr_debug("Enabling perf counter for CPU%d\n", cpu);
> > +     /*
> > +      * We do not actually let the counter run. Leave it until start().
> > +      */
> > +}
> > +
> > +static void loongarch_pmu_disable_event(int idx)
> > +{
> > +     struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> > +     unsigned long flags;
> > +
> > +     WARN_ON(idx < 0 || idx >= loongarch_pmu.num_counters);
> > +
> > +     local_irq_save(flags);
> > +     cpuc->saved_ctrl[idx] = loongarch_pmu_read_control(idx) &
> > +             ~M_PERFCTL_COUNT_EVENT_WHENEVER;
> > +     loongarch_pmu_write_control(idx, cpuc->saved_ctrl[idx]);
> > +     local_irq_restore(flags);
> > +}
> > +
> > +static int loongarch_pmu_event_set_period(struct perf_event *event,
> > +                                 struct hw_perf_event *hwc,
> > +                                 int idx)
> > +{
> > +     u64 left = local64_read(&hwc->period_left);
> > +     u64 period = hwc->sample_period;
> > +     int ret = 0;
> > +
> > +     if (unlikely((left + period) & (1ULL << 63))) {
> > +             /* left underflowed by more than period. */
> > +             left = period;
> > +             local64_set(&hwc->period_left, left);
> > +             hwc->last_period = period;
> > +             ret = 1;
> > +     } else  if (unlikely((left + period) <= period)) {
> > +             /* left underflowed by less than period. */
> > +             left += period;
> > +             local64_set(&hwc->period_left, left);
> > +             hwc->last_period = period;
> > +             ret = 1;
> > +     }
> > +
> > +     if (left > loongarch_pmu.max_period) {
> > +             left = loongarch_pmu.max_period;
> > +             local64_set(&hwc->period_left, left);
> > +     }
> > +
> > +     local64_set(&hwc->prev_count, loongarch_pmu.overflow - left);
> > +
> > +     loongarch_pmu.write_counter(idx, loongarch_pmu.overflow - left);
> > +
> > +     perf_event_update_userpage(event);
> > +
> > +     return ret;
> > +}
> > +
> > +static void loongarch_pmu_event_update(struct perf_event *event,
> > +                              struct hw_perf_event *hwc,
> > +                              int idx)
> > +{
> > +     u64 delta;
> > +     u64 prev_raw_count, new_raw_count;
> > +
> > +again:
> > +     prev_raw_count = local64_read(&hwc->prev_count);
> > +     new_raw_count = loongarch_pmu.read_counter(idx);
> > +
> > +     if (local64_cmpxchg(&hwc->prev_count, prev_raw_count,
> > +                             new_raw_count) != prev_raw_count)
> > +             goto again;
> > +
> > +     delta = new_raw_count - prev_raw_count;
> > +
> > +     local64_add(delta, &event->count);
> > +     local64_sub(delta, &hwc->period_left);
> > +}
> > +
> > +static void loongarch_pmu_start(struct perf_event *event, int flags)
> > +{
> > +     struct hw_perf_event *hwc = &event->hw;
> > +
> > +     if (flags & PERF_EF_RELOAD)
> > +             WARN_ON_ONCE(!(hwc->state & PERF_HES_UPTODATE));
> > +
> > +     hwc->state = 0;
> > +
> > +     /* Set the period for the event. */
> > +     loongarch_pmu_event_set_period(event, hwc, hwc->idx);
> > +
> > +     /* Enable the event. */
> > +     loongarch_pmu_enable_event(hwc, hwc->idx);
> > +}
> > +
> > +static void loongarch_pmu_stop(struct perf_event *event, int flags)
> > +{
> > +     struct hw_perf_event *hwc = &event->hw;
> > +
> > +     if (!(hwc->state & PERF_HES_STOPPED)) {
> > +             /* We are working on a local event. */
> > +             loongarch_pmu_disable_event(hwc->idx);
> > +             barrier();
> > +             loongarch_pmu_event_update(event, hwc, hwc->idx);
> > +             hwc->state |= PERF_HES_STOPPED | PERF_HES_UPTODATE;
> > +     }
> > +}
> > +
> > +static int loongarch_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;
> > +     int idx;
> > +     int err = 0;
> > +
> > +     perf_pmu_disable(event->pmu);
> > +
> > +     /* To look for a free counter for this event. */
> > +     idx = loongarch_pmu_alloc_counter(cpuc, hwc);
> > +     if (idx < 0) {
> > +             err = idx;
> > +             goto out;
> > +     }
> > +
> > +     /*
> > +      * If there is an event in the counter we are going to use then
> > +      * make sure it is disabled.
> > +      */
> > +     event->hw.idx = idx;
> > +     loongarch_pmu_disable_event(idx);
> > +     cpuc->events[idx] = event;
> > +
> > +     hwc->state = PERF_HES_STOPPED | PERF_HES_UPTODATE;
> > +     if (flags & PERF_EF_START)
> > +             loongarch_pmu_start(event, PERF_EF_RELOAD);
> > +
> > +     /* Propagate our changes to the userspace mapping. */
> > +     perf_event_update_userpage(event);
> > +
> > +out:
> > +     perf_pmu_enable(event->pmu);
> > +     return err;
> > +}
> > +
> > +static void loongarch_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;
> > +     int idx = hwc->idx;
> > +
> > +     WARN_ON(idx < 0 || idx >= loongarch_pmu.num_counters);
> > +
> > +     loongarch_pmu_stop(event, PERF_EF_UPDATE);
> > +     cpuc->events[idx] = NULL;
> > +     clear_bit(idx, cpuc->used_mask);
> > +
> > +     perf_event_update_userpage(event);
> > +}
> > +
> > +static void loongarch_pmu_read(struct perf_event *event)
> > +{
> > +     struct hw_perf_event *hwc = &event->hw;
> > +
> > +     /* Don't read disabled counters! */
> > +     if (hwc->idx < 0)
> > +             return;
> > +
> > +     loongarch_pmu_event_update(event, hwc, hwc->idx);
> > +}
> > +
> > +static void loongarch_pmu_enable(struct pmu *pmu)
> > +{
> > +     resume_local_counters();
> > +}
> > +
> > +static void loongarch_pmu_disable(struct pmu *pmu)
> > +{
> > +     pause_local_counters();
> > +}
> > +
> > +static atomic_t active_events = ATOMIC_INIT(0);
> > +static DEFINE_MUTEX(pmu_reserve_mutex);
> > +
> > +static void reset_counters(void *arg);
> > +static int __hw_perf_event_init(struct perf_event *event);
> > +
> > +static void hw_perf_event_destroy(struct perf_event *event)
> > +{
> > +     if (atomic_dec_and_mutex_lock(&active_events,
> > +                             &pmu_reserve_mutex)) {
> > +             /*
> > +              * We must not call the destroy function with interrupts
> > +              * disabled.
> > +              */
> > +             on_each_cpu(reset_counters,
> > +                     (void *)(long)loongarch_pmu.num_counters, 1);
> > +             mutex_unlock(&pmu_reserve_mutex);
> > +     }
> > +}
> > +
> > +/* This is needed by specific irq handlers in perf_event_*.c */
> > +static void handle_associated_event(struct cpu_hw_events *cpuc,
> > +                                 int idx, struct perf_sample_data *data,
> > +                                 struct pt_regs *regs)
> > +{
> > +     struct perf_event *event = cpuc->events[idx];
> > +     struct hw_perf_event *hwc = &event->hw;
> > +
> > +     loongarch_pmu_event_update(event, hwc, idx);
> > +     data->period = event->hw.last_period;
> > +     if (!loongarch_pmu_event_set_period(event, hwc, idx))
> > +             return;
> > +
> > +     if (perf_event_overflow(event, data, regs))
> > +             loongarch_pmu_disable_event(idx);
> > +}
> > +
> > +static irqreturn_t pmu_handle_irq(int irq, void *dev)
> > +{
> > +     int handled = IRQ_NONE;
> > +     unsigned int counters = loongarch_pmu.num_counters;
> > +     u64 counter;
> > +     struct pt_regs *regs;
> > +     struct perf_sample_data data;
> > +     struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> > +
> > +     /*
> > +      * First we pause the local counters, so that when we are locked
> > +      * here, the counters are all paused. When it gets locked due to
> > +      * perf_disable(), the timer interrupt handler will be delayed.
> > +      *
> > +      * See also loongarch_pmu_start().
> > +      */
> > +     pause_local_counters();
> > +
> > +     regs = get_irq_regs();
> > +
> > +     perf_sample_data_init(&data, 0, 0);
> > +
> > +     switch (counters) {
> > +#define HANDLE_COUNTER(n)                                            \
> > +     case n + 1:                                                     \
> > +             if (test_bit(n, cpuc->used_mask)) {                     \
> > +                     counter = loongarch_pmu.read_counter(n);        \
> > +                     if (counter & loongarch_pmu.overflow) {         \
> > +                             handle_associated_event(cpuc, n, &data, regs); \
> > +                             handled = IRQ_HANDLED;                  \
> > +                     }                                               \
> > +             }
> > +     HANDLE_COUNTER(3)
> > +             fallthrough;
> > +     HANDLE_COUNTER(2)
> > +             fallthrough;
> > +     HANDLE_COUNTER(1)
> > +             fallthrough;
> > +     HANDLE_COUNTER(0)
> > +     }
> > +
> > +     resume_local_counters();
> > +
> > +     /*
> > +      * Do all the work for the pending perf events. We can do this
> > +      * in here because the performance counter interrupt is a regular
> > +      * interrupt, not NMI.
> > +      */
> > +     if (handled == IRQ_HANDLED)
> > +             irq_work_run();
> > +
> > +     return handled;
> > +}
> > +
> > +static int get_pmc_irq(void)
> > +{
> > +     struct irq_domain *d = irq_find_matching_fwnode(cpuintc_handle, DOMAIN_BUS_ANY);
> > +
> > +     if (d)
> > +             return irq_create_mapping(d, EXCCODE_PMC - EXCCODE_INT_START);
> > +
> > +     return -EINVAL;
> > +}
> > +
> > +static int loongarch_pmu_event_init(struct perf_event *event)
> > +{
> > +     int r, irq;
> > +     unsigned long flags;
> > +
> > +     /* does not support taken branch sampling */
> > +     if (has_branch_stack(event))
> > +             return -EOPNOTSUPP;
> > +
> > +     switch (event->attr.type) {
> > +     case PERF_TYPE_RAW:
> > +     case PERF_TYPE_HARDWARE:
> > +     case PERF_TYPE_HW_CACHE:
> > +             break;
> > +
> > +     default:
> > +             /* Init it to avoid false validate_group */
> > +             event->hw.event_base = 0xffffffff;
> > +             return -ENOENT;
> > +     }
> > +
> > +     if (event->cpu >= 0 && !cpu_online(event->cpu))
> > +             return -ENODEV;
> > +
> > +     irq = get_pmc_irq();
> > +     flags = IRQF_PERCPU | IRQF_NOBALANCING | IRQF_NO_THREAD | IRQF_NO_SUSPEND | IRQF_SHARED;
> > +     if (!atomic_inc_not_zero(&active_events)) {
> > +             mutex_lock(&pmu_reserve_mutex);
> > +             if (atomic_read(&active_events) == 0) {
> > +                     r = request_irq(irq, pmu_handle_irq,
> > +                                     flags, "Perf_PMU", &loongarch_pmu);
> > +                     if (r < 0) {
> > +                             pr_warn("PMU IRQ request failed\n");
> > +                             return -ENODEV;
> > +                     }
> > +             }
> > +             atomic_inc(&active_events);
> > +             mutex_unlock(&pmu_reserve_mutex);
> > +     }
> > +
> > +     return __hw_perf_event_init(event);
> > +}
> > +
> > +static struct pmu pmu = {
> > +     .pmu_enable     = loongarch_pmu_enable,
> > +     .pmu_disable    = loongarch_pmu_disable,
> > +     .event_init     = loongarch_pmu_event_init,
> > +     .add            = loongarch_pmu_add,
> > +     .del            = loongarch_pmu_del,
> > +     .start          = loongarch_pmu_start,
> > +     .stop           = loongarch_pmu_stop,
> > +     .read           = loongarch_pmu_read,
> > +};
> > +
> > +static unsigned int loongarch_pmu_perf_event_encode(const struct loongarch_perf_event *pev)
> > +{
> > +     return (pev->event_id & 0xff);
> > +}
> > +
> > +static const struct loongarch_perf_event *loongarch_pmu_map_general_event(int idx)
> > +{
> > +     const struct loongarch_perf_event *pev;
> > +
> > +     pev = &(*loongarch_pmu.general_event_map)[idx];
> > +
> > +     if (pev->event_id == HW_OP_UNSUPPORTED)
> > +             return ERR_PTR(-ENOENT);
> > +
> > +     return pev;
> > +}
> > +
> > +static const struct loongarch_perf_event *loongarch_pmu_map_cache_event(u64 config)
> > +{
> > +     unsigned int cache_type, cache_op, cache_result;
> > +     const struct loongarch_perf_event *pev;
> > +
> > +     cache_type = (config >> 0) & 0xff;
> > +     if (cache_type >= PERF_COUNT_HW_CACHE_MAX)
> > +             return ERR_PTR(-EINVAL);
> > +
> > +     cache_op = (config >> 8) & 0xff;
> > +     if (cache_op >= PERF_COUNT_HW_CACHE_OP_MAX)
> > +             return ERR_PTR(-EINVAL);
> > +
> > +     cache_result = (config >> 16) & 0xff;
> > +     if (cache_result >= PERF_COUNT_HW_CACHE_RESULT_MAX)
> > +             return ERR_PTR(-EINVAL);
> > +
> > +     pev = &((*loongarch_pmu.cache_event_map)
> > +                                     [cache_type]
> > +                                     [cache_op]
> > +                                     [cache_result]);
> > +
> > +     if (pev->event_id == CACHE_OP_UNSUPPORTED)
> > +             return ERR_PTR(-ENOENT);
> > +
> > +     return pev;
> > +}
> > +
> > +static int validate_group(struct perf_event *event)
> > +{
> > +     struct perf_event *sibling, *leader = event->group_leader;
> > +     struct cpu_hw_events fake_cpuc;
> > +
> > +     memset(&fake_cpuc, 0, sizeof(fake_cpuc));
> > +
> > +     if (loongarch_pmu_alloc_counter(&fake_cpuc, &leader->hw) < 0)
> > +             return -EINVAL;
> > +
> > +     for_each_sibling_event(sibling, leader) {
> > +             if (loongarch_pmu_alloc_counter(&fake_cpuc, &sibling->hw) < 0)
> > +                     return -EINVAL;
> > +     }
> > +
> > +     if (loongarch_pmu_alloc_counter(&fake_cpuc, &event->hw) < 0)
> > +             return -EINVAL;
> > +
> > +     return 0;
> > +}
> > +
> > +static void reset_counters(void *arg)
> > +{
> > +     int counters = (int)(long)arg;
> > +
> > +     switch (counters) {
> > +     case 4:
> > +             loongarch_pmu_write_control(3, 0);
> > +             loongarch_pmu.write_counter(3, 0);
> > +             fallthrough;
> > +     case 3:
> > +             loongarch_pmu_write_control(2, 0);
> > +             loongarch_pmu.write_counter(2, 0);
> > +             fallthrough;
> > +     case 2:
> > +             loongarch_pmu_write_control(1, 0);
> > +             loongarch_pmu.write_counter(1, 0);
> > +             fallthrough;
> > +     case 1:
> > +             loongarch_pmu_write_control(0, 0);
> > +             loongarch_pmu.write_counter(0, 0);
> > +     }
> > +}
> > +
> > +static const struct loongarch_perf_event loongson_new_event_map[PERF_COUNT_HW_MAX] = {
> > +     PERF_MAP_ALL_UNSUPPORTED,
> > +     [PERF_COUNT_HW_CPU_CYCLES] = { 0x00 },
> > +     [PERF_COUNT_HW_INSTRUCTIONS] = { 0x01 },
> > +     [PERF_COUNT_HW_CACHE_REFERENCES] = { 0x08 },
> > +     [PERF_COUNT_HW_CACHE_MISSES] = { 0x09 },
> > +     [PERF_COUNT_HW_BRANCH_INSTRUCTIONS] = { 0x02 },
> > +     [PERF_COUNT_HW_BRANCH_MISSES] = { 0x03 },
> > +};
> > +
> > +static const struct loongarch_perf_event loongson_new_cache_map
> > +                             [PERF_COUNT_HW_CACHE_MAX]
> > +                             [PERF_COUNT_HW_CACHE_OP_MAX]
> > +                             [PERF_COUNT_HW_CACHE_RESULT_MAX] = {
> > +PERF_CACHE_MAP_ALL_UNSUPPORTED,
> > +[C(L1D)] = {
> > +     /*
> > +      * Like some other architectures (e.g. ARM), the performance
> > +      * counters don't differentiate between read and write
> > +      * accesses/misses, so this isn't strictly correct, but it's the
> > +      * best we can do. Writes and reads get combined.
> > +      */
> > +     [C(OP_READ)] = {
> > +             [C(RESULT_ACCESS)]      = { 0x8 },
> > +             [C(RESULT_MISS)]        = { 0x9 },
> > +     },
> > +     [C(OP_WRITE)] = {
> > +             [C(RESULT_ACCESS)]      = { 0x8 },
> > +             [C(RESULT_MISS)]        = { 0x9 },
> > +     },
> > +     [C(OP_PREFETCH)] = {
> > +             [C(RESULT_ACCESS)]      = { 0xaa },
> > +             [C(RESULT_MISS)]        = { 0xa9 },
> > +     },
> > +},
> > +[C(L1I)] = {
> > +     [C(OP_READ)] = {
> > +             [C(RESULT_ACCESS)]      = { 0x6 },
> > +             [C(RESULT_MISS)]        = { 0x7 },
> > +     },
> > +},
> > +[C(LL)] = {
> > +     [C(OP_READ)] = {
> > +             [C(RESULT_ACCESS)]      = { 0xc },
> > +             [C(RESULT_MISS)]        = { 0xd },
> > +     },
> > +     [C(OP_WRITE)] = {
> > +             [C(RESULT_ACCESS)]      = { 0xc },
> > +             [C(RESULT_MISS)]        = { 0xd },
> > +     },
> > +},
> > +[C(ITLB)] = {
> > +     [C(OP_READ)] = {
> > +             [C(RESULT_MISS)]    = { 0x3b },
> > +     },
> > +},
> > +[C(DTLB)] = {
> > +     [C(OP_READ)] = {
> > +             [C(RESULT_ACCESS)]      = { 0x4 },
> > +             [C(RESULT_MISS)]        = { 0x3c },
> > +     },
> > +     [C(OP_WRITE)] = {
> > +             [C(RESULT_ACCESS)]      = { 0x4 },
> > +             [C(RESULT_MISS)]        = { 0x3c },
> > +     },
> > +},
> > +[C(BPU)] = {
> > +     /* Using the same code for *HW_BRANCH* */
> > +     [C(OP_READ)] = {
> > +             [C(RESULT_ACCESS)]  = { 0x02 },
> > +             [C(RESULT_MISS)]    = { 0x03 },
> > +     },
> > +},
> > +};
> > +
> > +static int __hw_perf_event_init(struct perf_event *event)
> > +{
> > +     struct perf_event_attr *attr = &event->attr;
> > +     struct hw_perf_event *hwc = &event->hw;
> > +     const struct loongarch_perf_event *pev;
> > +     int err;
> > +
> > +     /* Returning LoongArch event descriptor for generic perf event. */
> > +     if (PERF_TYPE_HARDWARE == event->attr.type) {
> > +             if (event->attr.config >= PERF_COUNT_HW_MAX)
> > +                     return -EINVAL;
> > +             pev = loongarch_pmu_map_general_event(event->attr.config);
> > +     } else if (PERF_TYPE_HW_CACHE == event->attr.type) {
> > +             pev = loongarch_pmu_map_cache_event(event->attr.config);
> > +     } else if (PERF_TYPE_RAW == event->attr.type) {
> > +             /* We are working on the global raw event. */
> > +             mutex_lock(&raw_event_mutex);
> > +             pev = loongarch_pmu.map_raw_event(event->attr.config);
> > +     } else {
> > +             /* The event type is not (yet) supported. */
> > +             return -EOPNOTSUPP;
> > +     }
> > +
> > +     if (IS_ERR(pev)) {
> > +             if (PERF_TYPE_RAW == event->attr.type)
> > +                     mutex_unlock(&raw_event_mutex);
> > +             return PTR_ERR(pev);
> > +     }
> > +
> > +     /*
> > +      * We allow max flexibility on how each individual counter shared
> > +      * by the single CPU operates (the mode exclusion and the range).
> > +      */
> > +     hwc->config_base = CSR_PERFCTRL_IE;
> > +
> > +     hwc->event_base = loongarch_pmu_perf_event_encode(pev);
> > +     if (PERF_TYPE_RAW == event->attr.type)
> > +             mutex_unlock(&raw_event_mutex);
> > +
> > +     if (!attr->exclude_user) {
> > +             hwc->config_base |= CSR_PERFCTRL_PLV3;
> > +             hwc->config_base |= CSR_PERFCTRL_PLV2;
> > +     }
> > +     if (!attr->exclude_kernel) {
> > +             hwc->config_base |= CSR_PERFCTRL_PLV0;
> > +     }
> > +     if (!attr->exclude_hv) {
> > +             hwc->config_base |= CSR_PERFCTRL_PLV1;
> > +     }
> > +
> > +     hwc->config_base &= M_PERFCTL_CONFIG_MASK;
> > +     /*
> > +      * The event can belong to another cpu. We do not assign a local
> > +      * counter for it for now.
> > +      */
> > +     hwc->idx = -1;
> > +     hwc->config = 0;
> > +
> > +     if (!hwc->sample_period) {
> > +             hwc->sample_period  = loongarch_pmu.max_period;
> > +             hwc->last_period    = hwc->sample_period;
> > +             local64_set(&hwc->period_left, hwc->sample_period);
> > +     }
> > +
> > +     err = 0;
> > +     if (event->group_leader != event)
> > +             err = validate_group(event);
> > +
> > +     event->destroy = hw_perf_event_destroy;
> > +
> > +     if (err)
> > +             event->destroy(event);
> > +
> > +     return err;
> > +}
> > +
> > +static void pause_local_counters(void)
> > +{
> > +     struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> > +     int ctr = loongarch_pmu.num_counters;
> > +     unsigned long flags;
> > +
> > +     local_irq_save(flags);
> > +     do {
> > +             ctr--;
> > +             cpuc->saved_ctrl[ctr] = loongarch_pmu_read_control(ctr);
> > +             loongarch_pmu_write_control(ctr, cpuc->saved_ctrl[ctr] &
> > +                                      ~M_PERFCTL_COUNT_EVENT_WHENEVER);
> > +     } while (ctr > 0);
> > +     local_irq_restore(flags);
> > +}
> > +
> > +static void resume_local_counters(void)
> > +{
> > +     struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> > +     int ctr = loongarch_pmu.num_counters;
> > +
> > +     do {
> > +             ctr--;
> > +             loongarch_pmu_write_control(ctr, cpuc->saved_ctrl[ctr]);
> > +     } while (ctr > 0);
> > +}
> > +
> > +static const struct loongarch_perf_event *loongarch_pmu_map_raw_event(u64 config)
> > +{
> > +     raw_event.event_id = config & 0xff;
> > +
> > +     return &raw_event;
> > +}
> > +
> > +static int __init
> > +init_hw_perf_events(void)
> > +{
> > +     int counters = 4;
> > +
> > +     if (!cpu_has_pmp)
> > +             return -ENODEV;
> > +
> > +     pr_info("Performance counters: ");
> > +
> > +     loongarch_pmu.num_counters = counters;
> > +     loongarch_pmu.max_period = (1ULL << 63) - 1;
> > +     loongarch_pmu.valid_count = (1ULL << 63) - 1;
> > +     loongarch_pmu.overflow = 1ULL << 63;
> > +     loongarch_pmu.name = "loongarch/loongson64";
> > +     loongarch_pmu.read_counter = loongarch_pmu_read_counter;
> > +     loongarch_pmu.write_counter = loongarch_pmu_write_counter;
> > +     loongarch_pmu.map_raw_event = loongarch_pmu_map_raw_event;
> > +     loongarch_pmu.general_event_map = &loongson_new_event_map;
> > +     loongarch_pmu.cache_event_map = &loongson_new_cache_map;
> > +
> > +     on_each_cpu(reset_counters, (void *)(long)counters, 1);
> > +
> > +     pr_cont("%s PMU enabled, %d %d-bit counters available to each "
> > +             "CPU.\n", loongarch_pmu.name, counters, 64);
> > +
> > +     perf_pmu_register(&pmu, "cpu", PERF_TYPE_RAW);
> > +
> > +     return 0;
> > +}
> > +early_initcall(init_hw_perf_events);
> > diff --git a/arch/loongarch/kernel/perf_regs.c b/arch/loongarch/kernel/perf_regs.c
> > new file mode 100644
> > index 000000000000..a5e9768e8414
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/perf_regs.c
> > @@ -0,0 +1,50 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (C) 2022 Loongson Technology Corporation Limited
>
> And this file.
OK, thanks.

Huacai
>
> > + */
> > +
> > +#include <linux/perf_event.h>
> > +
> > +#include <asm/ptrace.h>
> > +
> > +#ifdef CONFIG_32BIT
> > +u64 perf_reg_abi(struct task_struct *tsk)
> > +{
> > +     return PERF_SAMPLE_REGS_ABI_32;
> > +}
> > +#else /* Must be CONFIG_64BIT */
> > +u64 perf_reg_abi(struct task_struct *tsk)
> > +{
> > +     if (test_tsk_thread_flag(tsk, TIF_32BIT_REGS))
> > +             return PERF_SAMPLE_REGS_ABI_32;
> > +     else
> > +             return PERF_SAMPLE_REGS_ABI_64;
> > +}
> > +#endif /* CONFIG_32BIT */
> > +
> > +int perf_reg_validate(u64 mask)
> > +{
> > +     if (!mask)
> > +             return -EINVAL;
> > +     if (mask & ~((1ull << PERF_REG_LOONGARCH_MAX) - 1))
> > +             return -EINVAL;
> > +     return 0;
> > +}
> > +
> > +u64 perf_reg_value(struct pt_regs *regs, int idx)
> > +{
> > +     if (WARN_ON_ONCE((u32)idx >= PERF_REG_LOONGARCH_MAX))
> > +             return 0;
> > +
> > +     if ((u32)idx == PERF_REG_LOONGARCH_PC)
> > +             return regs->csr_era;
> > +
> > +     return regs->regs[idx];
> > +}
> > +
> > +void perf_get_regs_user(struct perf_regs *regs_user,
> > +                     struct pt_regs *regs)
> > +{
> > +     regs_user->regs = task_pt_regs(current);
> > +     regs_user->abi = perf_reg_abi(current);
> > +}
>
> --
> WANG "xen0n" Xuerui
>
> Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/
>