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![Alexandre Ghiti](/assets/img/avatar_default.png)
The following panic can happen when mmap is called before the pmu add
callback which sets the hardware counter index: this happens for example
with the following command `perf record --no-bpf-event -n kill`.
[ 99.461486] CPU: 1 PID: 1259 Comm: perf Tainted: G E 6.6.0-rc4ubuntu-defconfig #2
[ 99.461669] Hardware name: riscv-virtio,qemu (DT)
[ 99.461748] epc : pmu_sbi_set_scounteren+0x42/0x44
[ 99.462337] ra : smp_call_function_many_cond+0x126/0x5b0
[ 99.462369] epc : ffffffff809f9d24 ra : ffffffff800f93e0 sp : ff60000082153aa0
[ 99.462407] gp : ffffffff82395c98 tp : ff6000009a218040 t0 : ff6000009ab3a4f0
[ 99.462425] t1 : 0000000000000004 t2 : 0000000000000100 s0 : ff60000082153ab0
[ 99.462459] s1 : 0000000000000000 a0 : ff60000098869528 a1 : 0000000000000000
[ 99.462473] a2 : 000000000000001f a3 : 0000000000f00000 a4 : fffffffffffffff8
[ 99.462488] a5 : 00000000000000cc a6 : 0000000000000000 a7 : 0000000000735049
[ 99.462502] s2 : 0000000000000001 s3 : ffffffff809f9ce2 s4 : ff60000098869528
[ 99.462516] s5 : 0000000000000002 s6 : 0000000000000004 s7 : 0000000000000001
[ 99.462530] s8 : ff600003fec98bc0 s9 : ffffffff826c5890 s10: ff600003fecfcde0
[ 99.462544] s11: ff600003fec98bc0 t3 : ffffffff819e2558 t4 : ff1c000004623840
[ 99.462557] t5 : 0000000000000901 t6 : ff6000008feeb890
[ 99.462570] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003
[ 99.462658] [<ffffffff809f9d24>] pmu_sbi_set_scounteren+0x42/0x44
[ 99.462979] Code: 1060 4785 97bb 00d7 8fd9 9073 1067 6422 0141 8082 (9002) 0013
[ 99.463335] Kernel BUG [#2]
To circumvent this, try to enable userspace access to the hardware counter
when it is selected in addition to when the event is mapped. And vice-versa
when the event is stopped/unmapped.
Fixes: cc4c07c89a
("drivers: perf: Implement perf event mmap support in the SBI backend")
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20231006082010.11963-1-alexghiti@rivosinc.com
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
434 lines
11 KiB
C
434 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* RISC-V performance counter support.
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*
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* Copyright (C) 2021 Western Digital Corporation or its affiliates.
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*
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* This implementation is based on old RISC-V perf and ARM perf event code
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* which are in turn based on sparc64 and x86 code.
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*/
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#include <linux/cpumask.h>
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#include <linux/irq.h>
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#include <linux/irqdesc.h>
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#include <linux/perf/riscv_pmu.h>
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#include <linux/printk.h>
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#include <linux/smp.h>
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#include <linux/sched_clock.h>
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#include <asm/sbi.h>
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static bool riscv_perf_user_access(struct perf_event *event)
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{
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return ((event->attr.type == PERF_TYPE_HARDWARE) ||
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(event->attr.type == PERF_TYPE_HW_CACHE) ||
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(event->attr.type == PERF_TYPE_RAW)) &&
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!!(event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT) &&
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(event->hw.idx != -1);
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}
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void arch_perf_update_userpage(struct perf_event *event,
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struct perf_event_mmap_page *userpg, u64 now)
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{
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struct clock_read_data *rd;
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unsigned int seq;
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u64 ns;
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userpg->cap_user_time = 0;
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userpg->cap_user_time_zero = 0;
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userpg->cap_user_time_short = 0;
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userpg->cap_user_rdpmc = riscv_perf_user_access(event);
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#ifdef CONFIG_RISCV_PMU
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/*
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* The counters are 64-bit but the priv spec doesn't mandate all the
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* bits to be implemented: that's why, counter width can vary based on
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* the cpu vendor.
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*/
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if (userpg->cap_user_rdpmc)
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userpg->pmc_width = to_riscv_pmu(event->pmu)->ctr_get_width(event->hw.idx) + 1;
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#endif
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do {
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rd = sched_clock_read_begin(&seq);
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userpg->time_mult = rd->mult;
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userpg->time_shift = rd->shift;
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userpg->time_zero = rd->epoch_ns;
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userpg->time_cycles = rd->epoch_cyc;
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userpg->time_mask = rd->sched_clock_mask;
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/*
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* Subtract the cycle base, such that software that
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* doesn't know about cap_user_time_short still 'works'
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* assuming no wraps.
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*/
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ns = mul_u64_u32_shr(rd->epoch_cyc, rd->mult, rd->shift);
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userpg->time_zero -= ns;
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} while (sched_clock_read_retry(seq));
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userpg->time_offset = userpg->time_zero - now;
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/*
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* time_shift is not expected to be greater than 31 due to
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* the original published conversion algorithm shifting a
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* 32-bit value (now specifies a 64-bit value) - refer
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* perf_event_mmap_page documentation in perf_event.h.
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*/
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if (userpg->time_shift == 32) {
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userpg->time_shift = 31;
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userpg->time_mult >>= 1;
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}
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/*
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* Internal timekeeping for enabled/running/stopped times
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* is always computed with the sched_clock.
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*/
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userpg->cap_user_time = 1;
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userpg->cap_user_time_zero = 1;
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userpg->cap_user_time_short = 1;
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}
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static unsigned long csr_read_num(int csr_num)
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{
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#define switchcase_csr_read(__csr_num, __val) {\
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case __csr_num: \
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__val = csr_read(__csr_num); \
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break; }
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#define switchcase_csr_read_2(__csr_num, __val) {\
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switchcase_csr_read(__csr_num + 0, __val) \
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switchcase_csr_read(__csr_num + 1, __val)}
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#define switchcase_csr_read_4(__csr_num, __val) {\
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switchcase_csr_read_2(__csr_num + 0, __val) \
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switchcase_csr_read_2(__csr_num + 2, __val)}
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#define switchcase_csr_read_8(__csr_num, __val) {\
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switchcase_csr_read_4(__csr_num + 0, __val) \
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switchcase_csr_read_4(__csr_num + 4, __val)}
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#define switchcase_csr_read_16(__csr_num, __val) {\
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switchcase_csr_read_8(__csr_num + 0, __val) \
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switchcase_csr_read_8(__csr_num + 8, __val)}
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#define switchcase_csr_read_32(__csr_num, __val) {\
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switchcase_csr_read_16(__csr_num + 0, __val) \
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switchcase_csr_read_16(__csr_num + 16, __val)}
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unsigned long ret = 0;
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switch (csr_num) {
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switchcase_csr_read_32(CSR_CYCLE, ret)
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switchcase_csr_read_32(CSR_CYCLEH, ret)
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default :
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break;
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}
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return ret;
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#undef switchcase_csr_read_32
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#undef switchcase_csr_read_16
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#undef switchcase_csr_read_8
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#undef switchcase_csr_read_4
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#undef switchcase_csr_read_2
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#undef switchcase_csr_read
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}
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/*
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* Read the CSR of a corresponding counter.
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*/
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unsigned long riscv_pmu_ctr_read_csr(unsigned long csr)
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{
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if (csr < CSR_CYCLE || csr > CSR_HPMCOUNTER31H ||
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(csr > CSR_HPMCOUNTER31 && csr < CSR_CYCLEH)) {
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pr_err("Invalid performance counter csr %lx\n", csr);
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return -EINVAL;
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}
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return csr_read_num(csr);
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}
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u64 riscv_pmu_ctr_get_width_mask(struct perf_event *event)
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{
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int cwidth;
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struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
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struct hw_perf_event *hwc = &event->hw;
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if (!rvpmu->ctr_get_width)
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/**
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* If the pmu driver doesn't support counter width, set it to default
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* maximum allowed by the specification.
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*/
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cwidth = 63;
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else {
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if (hwc->idx == -1)
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/* Handle init case where idx is not initialized yet */
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cwidth = rvpmu->ctr_get_width(0);
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else
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cwidth = rvpmu->ctr_get_width(hwc->idx);
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}
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return GENMASK_ULL(cwidth, 0);
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}
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u64 riscv_pmu_event_update(struct perf_event *event)
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{
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struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
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struct hw_perf_event *hwc = &event->hw;
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u64 prev_raw_count, new_raw_count;
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unsigned long cmask;
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u64 oldval, delta;
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if (!rvpmu->ctr_read)
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return 0;
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cmask = riscv_pmu_ctr_get_width_mask(event);
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do {
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prev_raw_count = local64_read(&hwc->prev_count);
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new_raw_count = rvpmu->ctr_read(event);
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oldval = local64_cmpxchg(&hwc->prev_count, prev_raw_count,
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new_raw_count);
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} while (oldval != prev_raw_count);
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delta = (new_raw_count - prev_raw_count) & cmask;
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local64_add(delta, &event->count);
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local64_sub(delta, &hwc->period_left);
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return delta;
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}
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void riscv_pmu_stop(struct perf_event *event, int flags)
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{
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struct hw_perf_event *hwc = &event->hw;
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struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
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WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
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if (!(hwc->state & PERF_HES_STOPPED)) {
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if (rvpmu->ctr_stop) {
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rvpmu->ctr_stop(event, 0);
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hwc->state |= PERF_HES_STOPPED;
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}
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riscv_pmu_event_update(event);
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hwc->state |= PERF_HES_UPTODATE;
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}
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}
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int riscv_pmu_event_set_period(struct perf_event *event)
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{
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struct hw_perf_event *hwc = &event->hw;
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s64 left = local64_read(&hwc->period_left);
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s64 period = hwc->sample_period;
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int overflow = 0;
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uint64_t max_period = riscv_pmu_ctr_get_width_mask(event);
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if (unlikely(left <= -period)) {
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left = period;
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local64_set(&hwc->period_left, left);
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hwc->last_period = period;
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overflow = 1;
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}
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if (unlikely(left <= 0)) {
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left += period;
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local64_set(&hwc->period_left, left);
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hwc->last_period = period;
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overflow = 1;
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}
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/*
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* Limit the maximum period to prevent the counter value
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* from overtaking the one we are about to program. In
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* effect we are reducing max_period to account for
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* interrupt latency (and we are being very conservative).
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*/
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if (left > (max_period >> 1))
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left = (max_period >> 1);
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local64_set(&hwc->prev_count, (u64)-left);
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perf_event_update_userpage(event);
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return overflow;
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}
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void riscv_pmu_start(struct perf_event *event, int flags)
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{
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struct hw_perf_event *hwc = &event->hw;
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struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
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uint64_t max_period = riscv_pmu_ctr_get_width_mask(event);
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u64 init_val;
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if (flags & PERF_EF_RELOAD)
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WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));
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hwc->state = 0;
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riscv_pmu_event_set_period(event);
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init_val = local64_read(&hwc->prev_count) & max_period;
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rvpmu->ctr_start(event, init_val);
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perf_event_update_userpage(event);
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}
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static int riscv_pmu_add(struct perf_event *event, int flags)
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{
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struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
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struct cpu_hw_events *cpuc = this_cpu_ptr(rvpmu->hw_events);
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struct hw_perf_event *hwc = &event->hw;
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int idx;
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idx = rvpmu->ctr_get_idx(event);
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if (idx < 0)
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return idx;
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hwc->idx = idx;
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cpuc->events[idx] = event;
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cpuc->n_events++;
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hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
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if (flags & PERF_EF_START)
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riscv_pmu_start(event, PERF_EF_RELOAD);
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/* Propagate our changes to the userspace mapping. */
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perf_event_update_userpage(event);
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return 0;
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}
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static void riscv_pmu_del(struct perf_event *event, int flags)
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{
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struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
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struct cpu_hw_events *cpuc = this_cpu_ptr(rvpmu->hw_events);
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struct hw_perf_event *hwc = &event->hw;
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riscv_pmu_stop(event, PERF_EF_UPDATE);
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cpuc->events[hwc->idx] = NULL;
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/* The firmware need to reset the counter mapping */
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if (rvpmu->ctr_stop)
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rvpmu->ctr_stop(event, RISCV_PMU_STOP_FLAG_RESET);
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cpuc->n_events--;
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if (rvpmu->ctr_clear_idx)
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rvpmu->ctr_clear_idx(event);
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perf_event_update_userpage(event);
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hwc->idx = -1;
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}
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static void riscv_pmu_read(struct perf_event *event)
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{
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riscv_pmu_event_update(event);
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}
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static int riscv_pmu_event_init(struct perf_event *event)
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{
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struct hw_perf_event *hwc = &event->hw;
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struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
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int mapped_event;
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u64 event_config = 0;
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uint64_t cmask;
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hwc->flags = 0;
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mapped_event = rvpmu->event_map(event, &event_config);
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if (mapped_event < 0) {
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pr_debug("event %x:%llx not supported\n", event->attr.type,
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event->attr.config);
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return mapped_event;
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}
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/*
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* idx is set to -1 because the index of a general event should not be
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* decided until binding to some counter in pmu->add().
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* config will contain the information about counter CSR
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* the idx will contain the counter index
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*/
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hwc->config = event_config;
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hwc->idx = -1;
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hwc->event_base = mapped_event;
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if (rvpmu->event_init)
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rvpmu->event_init(event);
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if (!is_sampling_event(event)) {
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/*
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* For non-sampling runs, limit the sample_period to half
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* of the counter width. That way, the new counter value
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* is far less likely to overtake the previous one unless
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* you have some serious IRQ latency issues.
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*/
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cmask = riscv_pmu_ctr_get_width_mask(event);
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hwc->sample_period = cmask >> 1;
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hwc->last_period = hwc->sample_period;
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local64_set(&hwc->period_left, hwc->sample_period);
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}
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return 0;
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}
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static int riscv_pmu_event_idx(struct perf_event *event)
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{
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struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
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if (!(event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT))
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return 0;
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if (rvpmu->csr_index)
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return rvpmu->csr_index(event) + 1;
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return 0;
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}
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static void riscv_pmu_event_mapped(struct perf_event *event, struct mm_struct *mm)
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{
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struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
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if (rvpmu->event_mapped) {
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rvpmu->event_mapped(event, mm);
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perf_event_update_userpage(event);
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}
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}
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static void riscv_pmu_event_unmapped(struct perf_event *event, struct mm_struct *mm)
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{
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struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
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if (rvpmu->event_unmapped) {
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rvpmu->event_unmapped(event, mm);
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perf_event_update_userpage(event);
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}
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}
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struct riscv_pmu *riscv_pmu_alloc(void)
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{
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struct riscv_pmu *pmu;
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int cpuid, i;
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struct cpu_hw_events *cpuc;
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pmu = kzalloc(sizeof(*pmu), GFP_KERNEL);
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if (!pmu)
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goto out;
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pmu->hw_events = alloc_percpu_gfp(struct cpu_hw_events, GFP_KERNEL);
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if (!pmu->hw_events) {
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pr_info("failed to allocate per-cpu PMU data.\n");
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goto out_free_pmu;
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}
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for_each_possible_cpu(cpuid) {
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cpuc = per_cpu_ptr(pmu->hw_events, cpuid);
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cpuc->n_events = 0;
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for (i = 0; i < RISCV_MAX_COUNTERS; i++)
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cpuc->events[i] = NULL;
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}
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pmu->pmu = (struct pmu) {
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.event_init = riscv_pmu_event_init,
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.event_mapped = riscv_pmu_event_mapped,
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.event_unmapped = riscv_pmu_event_unmapped,
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.event_idx = riscv_pmu_event_idx,
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.add = riscv_pmu_add,
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.del = riscv_pmu_del,
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.start = riscv_pmu_start,
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.stop = riscv_pmu_stop,
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.read = riscv_pmu_read,
|
|
};
|
|
|
|
return pmu;
|
|
|
|
out_free_pmu:
|
|
kfree(pmu);
|
|
out:
|
|
return NULL;
|
|
}
|