linux-kernel - Re: [PATCH] perf: riscv: Fix selecting counters in legacy mode

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Message-ID: <0fa3cf3d-48f6-405b-8b66-8935a629089e@sifive.com>
Date: Wed, 31 Jul 2024 02:37:40 -0500
From: Samuel Holland <samuel.holland@...ive.com>
To: Shifrin Dmitry <dmitry.shifrin@...tacore.com>,
 linux-riscv@...ts.infradead.org
Cc: atishp@...shpatra.org, anup@...infault.org, will@...nel.org,
 mark.rutland@....com, paul.walmsley@...ive.com, palmer@...belt.com,
 aou@...s.berkeley.edu, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, alexghiti@...osinc.com
Subject: Re: [PATCH] perf: riscv: Fix selecting counters in legacy mode

Hi Dmitry,

On 2024-07-29 7:58 AM, Shifrin Dmitry wrote:
> It is required to check event type before checking event config.
> Events with the different types can have the same config.
> This check is missed for legacy mode code
> 
> For such perf usage:
>     sysctl -w kernel.perf_user_access=2
>     perf stat -e cycles,L1-dcache-loads --
> driver will try to force both events to CYCLE counter.
> 
> This commit implements event type check before forcing
> events on the special counters.

It looks like pmu_sbi_event_mapped() and pmu_sbi_event_mapped() have a similar
bug where they do not check event->attr.type.

Regards,
Samuel

> 
> Signed-off-by: Shifrin Dmitry <dmitry.shifrin@...tacore.com>
> ---
>  drivers/perf/riscv_pmu_sbi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
> index 36d128ff166f..bf14ab282e11 100644
> --- a/drivers/perf/riscv_pmu_sbi.c
> +++ b/drivers/perf/riscv_pmu_sbi.c
> @@ -416,7 +416,7 @@ static int pmu_sbi_ctr_get_idx(struct perf_event *event)
>  	 * but not in the user access mode as we want to use the other counters
>  	 * that support sampling/filtering.
>  	 */
> -	if (hwc->flags & PERF_EVENT_FLAG_LEGACY) {
> +	if ((hwc->flags & PERF_EVENT_FLAG_LEGACY) && (event->attr.type == PERF_TYPE_HARDWARE)) {
>  		if (event->attr.config == PERF_COUNT_HW_CPU_CYCLES) {
>  			cflags |= SBI_PMU_CFG_FLAG_SKIP_MATCH;
>  			cmask = 1;