[PATCH v9 15/20] RISC-V: perf: Skip PMU SBI extension when not implemented

[Anup Patel]

On Fri, Aug 7, 2026 at 1:40 PM Atish Patra <atish.patra at linux.dev> wrote:
>
> From: Charlie Jenkins <charlie at rivosinc.com>
>
> When the PMU SBI extension is not implemented, sbi_v2_available should
> not be set to true. The SBI implementation for counter config matching
> and firmware counter read  should also be skipped when the SBI extension
> is not implemented.
>
> Signed-off-by: Atish Patra <atishp at meta.com>
> Signed-off-by: Charlie Jenkins <charlie at rivosinc.com>

LGTM.

Reviewed-by: Anup Patel <anup at brainfault.org>

Regards,
Anup


> ---
>  drivers/perf/riscv_pmu_sbi.c | 55 ++++++++++++++++++++++++++------------------
>  1 file changed, 32 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
> index fd4bf8804c9a..f0b8b6eff2ea 100644
> --- a/drivers/perf/riscv_pmu_sbi.c
> +++ b/drivers/perf/riscv_pmu_sbi.c
> @@ -493,27 +493,32 @@ static void rvpmu_sbi_check_event(struct sbi_pmu_event_data *edata)
>         }
>  }
>
> -static void rvpmu_sbi_check_std_events(struct work_struct *work)
> +static void rvpmu_check_std_events(struct work_struct *work)
>  {
>         int ret;
>
> -       if (sbi_v3_available) {
> -               ret = pmu_sbi_check_event_info();
> -               if (ret)
> -                       pr_err("pmu_sbi_check_event_info failed with error %d\n", ret);
> -               return;
> -       }
> +       if (riscv_pmu_sbi_available()) {
> +               if (sbi_v3_available) {
> +                       ret = pmu_sbi_check_event_info();
> +                       if (ret)
> +                               pr_err("pmu_sbi_check_event_info failed with error %d\n", ret);
> +                       return;
> +               }
>
> -       for (int i = 0; i < ARRAY_SIZE(pmu_hw_event_sbi_map); i++)
> -               rvpmu_sbi_check_event(&pmu_hw_event_sbi_map[i]);
> +               for (int i = 0; i < ARRAY_SIZE(pmu_hw_event_sbi_map); i++)
> +                       rvpmu_sbi_check_event(&pmu_hw_event_sbi_map[i]);
>
> -       for (int i = 0; i < ARRAY_SIZE(pmu_cache_event_sbi_map); i++)
> -               for (int j = 0; j < ARRAY_SIZE(pmu_cache_event_sbi_map[i]); j++)
> -                       for (int k = 0; k < ARRAY_SIZE(pmu_cache_event_sbi_map[i][j]); k++)
> -                               rvpmu_sbi_check_event(&pmu_cache_event_sbi_map[i][j][k]);
> +               for (int i = 0; i < ARRAY_SIZE(pmu_cache_event_sbi_map); i++)
> +                       for (int j = 0; j < ARRAY_SIZE(pmu_cache_event_sbi_map[i]); j++)
> +                               for (int k = 0; k < ARRAY_SIZE(pmu_cache_event_sbi_map[i][j]); k++)
> +                                       rvpmu_sbi_check_event(&pmu_cache_event_sbi_map[i][j][k]);
> +       } else {
> +               DO_ONCE_LITE_IF(1, pr_info,
> +                               "Boot time config matching not required for smcdeleg\n");
> +       }
>  }
>
> -static DECLARE_WORK(check_std_events_work, rvpmu_sbi_check_std_events);
> +static DECLARE_WORK(check_std_events_work, rvpmu_check_std_events);
>
>  static ssize_t rvpmu_format_show(struct device *dev,
>                                  struct device_attribute *attr, char *buf)
> @@ -712,6 +717,9 @@ static int rvpmu_sbi_ctr_get_idx(struct perf_event *event)
>
>         cflags = rvpmu_sbi_get_filter_flags(event);
>
> +       if (!riscv_pmu_sbi_available())
> +               return -ENOENT;
> +
>         /*
>          * In legacy mode, we have to force the fixed counters for those events
>          * but not in the user access mode as we want to use the other counters
> @@ -999,7 +1007,7 @@ static u64 rvpmu_ctr_read(struct perf_event *event)
>                 return val;
>         }
>
> -       if (pmu_sbi_is_fw_event(event)) {
> +       if (pmu_sbi_is_fw_event(event) && riscv_pmu_sbi_available()) {
>                 ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_FW_READ,
>                                 hwc->idx, 0, 0, 0, 0, 0);
>                 if (ret.error)
> @@ -2132,12 +2140,16 @@ static int __init rvpmu_devinit(void)
>         int ret;
>         struct platform_device *pdev;
>
> -       if (sbi_spec_version >= sbi_mk_version(0, 3) &&
> -           sbi_probe_extension(SBI_EXT_PMU))
> -               static_branch_enable(&riscv_pmu_sbi_available);
> +       if (sbi_probe_extension(SBI_EXT_PMU)) {
> +               if (sbi_spec_version >= sbi_mk_version(0, 3)) {
> +                       static_branch_enable(&riscv_pmu_sbi_available);
> +                       if (sbi_spec_version >= sbi_mk_version(2, 0))
> +                               sbi_v2_available = true;
> +                       if (sbi_spec_version >= sbi_mk_version(3, 0))
> +                               sbi_v3_available = true;
> +               }
> +       }
>
> -       if (sbi_spec_version >= sbi_mk_version(2, 0))
> -               sbi_v2_available = true;
>         /*
>          * We need all three extensions to be present to access the counters
>          * in S-mode via Supervisor Counter delegation.
> @@ -2152,9 +2164,6 @@ static int __init rvpmu_devinit(void)
>         if (!(riscv_pmu_sbi_available_boot() || riscv_pmu_cdeleg_available_boot()))
>                 return 0;
>
> -       if (sbi_spec_version >= sbi_mk_version(3, 0))
> -               sbi_v3_available = true;
> -
>         ret = cpuhp_setup_state_multi(CPUHP_AP_PERF_RISCV_STARTING,
>                                       "perf/riscv/pmu:starting",
>                                       rvpmu_starting_cpu, rvpmu_dying_cpu);
>
> --
> 2.53.0-Meta
>