linux-kernel - Re: [PATCH 2/7] perf tools: apply evsel__set_config_if

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Message-ID: <20251202111403.GS724103@e132581.arm.com>
Date: Tue, 2 Dec 2025 11:14:03 +0000
From: Leo Yan <leo.yan@....com>
To: James Clark <james.clark@...aro.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Mike Leach <mike.leach@...aro.org>,
	John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>,
	Leo Yan <leo.yan@...ux.dev>, linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org, coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/7] perf tools: apply evsel__set_config_if_unset() to
 all config fields

On Mon, Dec 01, 2025 at 04:41:05PM +0000, Coresight ML wrote:

[...]

>  void evsel__set_config_if_unset(struct perf_pmu *pmu, struct evsel *evsel,
>  				const char *config_name, u64 val)
>  {
>  	u64 user_bits = 0, bits;
> -	struct evsel_config_term *term = evsel__get_config_term(evsel, USR_CHG_CONFIG);
> +	struct evsel_config_term *term;
> +	struct perf_pmu_format *format = pmu_find_format(&pmu->format, config_name);
> +	__u64 *vp;

Should check (format == NULL) here and bail out for a unknown config name?

> +
> +	switch (format->value) {
> +	case PERF_PMU_FORMAT_VALUE_CONFIG:
> +		term = evsel__get_config_term(evsel, USR_CHG_CONFIG);
> +		vp = &evsel->core.attr.config;
> +		break;
> +	case PERF_PMU_FORMAT_VALUE_CONFIG1:
> +		term = evsel__get_config_term(evsel, USR_CHG_CONFIG1);
> +		vp = &evsel->core.attr.config1;
> +		break;
> +	case PERF_PMU_FORMAT_VALUE_CONFIG2:
> +		term = evsel__get_config_term(evsel, USR_CHG_CONFIG2);
> +		vp = &evsel->core.attr.config2;
> +		break;
> +	case PERF_PMU_FORMAT_VALUE_CONFIG3:
> +		term = evsel__get_config_term(evsel, USR_CHG_CONFIG3);
> +		vp = &evsel->core.attr.config3;
> +		break;
> +	case PERF_PMU_FORMAT_VALUE_CONFIG4:
> +		term = evsel__get_config_term(evsel, USR_CHG_CONFIG4);
> +		vp = &evsel->core.attr.config4;
> +		break;
> +	default:
> +		pr_err("Unknown format value: %d\n", format->value);
> +		return;
> +	}
>  
>  	if (term)
>  		user_bits = term->val.cfg_chg;
> @@ -1396,20 +1436,8 @@ void evsel__set_config_if_unset(struct perf_pmu *pmu, struct evsel *evsel,
>  		return;
>  
>  	/* Otherwise replace it */
> -	evsel->core.attr.config &= ~bits;
> -	evsel->core.attr.config |= field_prep(bits, val);
> -}
> -
> -static struct perf_pmu_format *
> -pmu_find_format(const struct list_head *formats, const char *name)
> -{
> -	struct perf_pmu_format *format;
> -
> -	list_for_each_entry(format, formats, list)
> -		if (!strcmp(format->name, name))
> -			return format;
> -
> -	return NULL;
> +	*vp &= ~bits;
> +	*vp |= FIELD_PREP(bits, val);
>  }