Re: [PATCH v2 4/9] selftests/resctrl: Support multiple events associated with iMC

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

On Tue, 3 Mar 2026, Reinette Chatre wrote:

> The resctrl selftests discover needed parameters to perf_event_open() via
> sysfs. The PMU associated with every memory controller (iMC) is discovered
> via the /sys/bus/event_source/devices/uncore_imc_N/type file while
> the read memory bandwidth event type and umask is discovered via
> /sys/bus/event_source/devices/uncore_imc_N/events/cas_count_read.
> 
> Newer systems may have multiple events that expose read memory bandwidth.
> For example,
>  /sys/bus/event_source/devices/uncore_imc_N/events/cas_count_read_sch0
>  /sys/bus/event_source/devices/uncore_imc_N/events/cas_count_read_sch1
> 
> Support parsing of iMC PMU properties when the PMU may have multiple events
> to measure read memory bandwidth. The PMU only needs to be discovered once.
> Split the parsing of event details from actual PMU discovery in order to
> loop over all events associated with the PMU. Match all events with the
> cas_count_read prefix instead of requiring there to be one file with that
> name.
> 
> Make the parsing code more robust. With strings passed around to create
> needed paths, use snprintf() instead of sprintf() to ensure there is
> always enough space to create the path. Ensure there is enough room in
> imc_counters_config[] before attempting to add an entry.
> 
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
> Reviewed-by: Zide Chen <zide.chen@intel.com>
> ---
> Changes since v1:
> - Add Zide Chen's RB tag.
> ---
>  tools/testing/selftests/resctrl/resctrl_val.c | 112 ++++++++++++++----
>  1 file changed, 90 insertions(+), 22 deletions(-)
> 
> diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
> index 25c8101631e0..7aae0cc5aee9 100644
> --- a/tools/testing/selftests/resctrl/resctrl_val.c
> +++ b/tools/testing/selftests/resctrl/resctrl_val.c
> @@ -11,10 +11,10 @@
>  #include "resctrl.h"
>  
>  #define UNCORE_IMC		"uncore_imc"
> -#define READ_FILE_NAME		"events/cas_count_read"
> +#define READ_FILE_NAME		"cas_count_read"
>  #define DYN_PMU_PATH		"/sys/bus/event_source/devices"
>  #define SCALE			0.00006103515625
> -#define MAX_IMCS		20
> +#define MAX_IMCS		40
>  #define MAX_TOKENS		5
>  
>  #define CON_MBM_LOCAL_BYTES_PATH		\
> @@ -109,21 +109,102 @@ static int open_perf_read_event(int i, int cpu_no)
>  	return 0;
>  }
>  
> +static int parse_imc_read_bw_events(char *imc_dir, unsigned int type,
> +				    unsigned int *count)
> +{
> +	char imc_events[1024], imc_counter_cfg[1024], cas_count_cfg[1024];

The first two are paths, right? PATH_MAX should be used instead of the 
literals.

> +	unsigned int org_count = *count;

orig_count is less ambiguous name.

> +	struct dirent *ep;
> +	int path_len;
> +	int ret = -1;
> +	FILE *fp;
> +	DIR *dp;
> +
> +	path_len = snprintf(imc_events, sizeof(imc_events), "%sevents", imc_dir);
> +	if (path_len >= sizeof(imc_events)) {
> +		ksft_print_msg("Unable to create path to %sevents\n", imc_dir);
> +		return -1;
> +	}
> +	dp = opendir(imc_events);
> +	if (dp) {
> +		while ((ep = readdir(dp))) {
> +			/*
> +			 * Parse all event files with READ_FILE_NAME
> +			 * prefix that contain the event number and umask.
> +			 * Skip files containing "." that contain unused
> +			 * properties of event.
> +			 */
> +			if (!strstr(ep->d_name, READ_FILE_NAME) ||
> +			    strchr(ep->d_name, '.'))
> +				continue;
> +
> +			path_len = snprintf(imc_counter_cfg, sizeof(imc_counter_cfg),
> +					    "%s/%s", imc_events, ep->d_name);
> +			if (path_len >= sizeof(imc_counter_cfg)) {
> +				ksft_print_msg("Unable to create path to %s/%s\n",
> +					       imc_events, ep->d_name);
> +				goto out_close;
> +			}
> +			fp = fopen(imc_counter_cfg, "r");
> +			if (!fp) {
> +				ksft_perror("Failed to open iMC config file");
> +				goto out_close;
> +			}
> +			if (fscanf(fp, "%1023s", cas_count_cfg) <= 0) {
> +				ksft_perror("Could not get iMC cas count read");
> +				fclose(fp);
> +				goto out_close;
> +			}
> +			fclose(fp);

I'd prefer:

	xx = fscanf(...);
	fclose(fp);
	if (xx) {
		...

...But it is up to you ("ret" cannot be used as xx as is).

> +			if (*count >= MAX_IMCS) {
> +				ksft_print_msg("Maximum iMC count exceeded\n");
> +				goto out_close;
> +			}
> +
> +			imc_counters_config[*count].type = type;
> +			get_read_event_and_umask(cas_count_cfg, *count);
> +			/* Do not fail after incrementing *count. */
> +			*count += 1;
> +		}
> +		if (*count == org_count) {
> +			ksft_print_msg("Unable to find events in %s\n", imc_events);
> +			goto out_close;
> +		}
> +	} else {
> +		ksft_perror("Unable to open PMU events directory");
> +		goto out;

Reverse the logic (handle error first), it reduces the indentation level 
of the loop.

> +	}
> +	ret = 0;
> +out_close:
> +	closedir(dp);
> +out:
> +	return ret;
> +}
> +
>  /* Get type and config of an iMC counter's read event. */
>  static int read_from_imc_dir(char *imc_dir, unsigned int *count)
>  {
> -	char cas_count_cfg[1024], imc_counter_cfg[1024], imc_counter_type[1024];
> +	char imc_counter_type[1024];
> +	unsigned int type;
> +	int path_len;
>  	FILE *fp;
> +	int ret;
>  
>  	/* Get type of iMC counter */
> -	sprintf(imc_counter_type, "%s%s", imc_dir, "type");
> +	path_len = snprintf(imc_counter_type, sizeof(imc_counter_type),
> +			    "%s%s", imc_dir, "type");
> +	if (path_len >= sizeof(imc_counter_type)) {
> +		ksft_print_msg("Unable to create path to %s%s\n",
> +			       imc_dir, "type");
> +		return -1;
> +	}
>  	fp = fopen(imc_counter_type, "r");
>  	if (!fp) {
>  		ksft_perror("Failed to open iMC counter type file");
>  
>  		return -1;
>  	}
> -	if (fscanf(fp, "%u", &imc_counters_config[*count].type) <= 0) {
> +	if (fscanf(fp, "%u", &type) <= 0) {
>  		ksft_perror("Could not get iMC type");
>  		fclose(fp);
>  
> @@ -131,24 +212,11 @@ static int read_from_imc_dir(char *imc_dir, unsigned int *count)
>  	}
>  	fclose(fp);
>  
> -	/* Get read config */
> -	sprintf(imc_counter_cfg, "%s%s", imc_dir, READ_FILE_NAME);
> -	fp = fopen(imc_counter_cfg, "r");
> -	if (!fp) {
> -		ksft_perror("Failed to open iMC config file");
> -
> -		return -1;
> -	}
> -	if (fscanf(fp, "%1023s", cas_count_cfg) <= 0) {
> -		ksft_perror("Could not get iMC cas count read");
> -		fclose(fp);
> -
> -		return -1;
> +	ret = parse_imc_read_bw_events(imc_dir, type, count);
> +	if (ret) {
> +		ksft_print_msg("Unable to parse bandwidth event and umask\n");
> +		return ret;
>  	}
> -	fclose(fp);
> -
> -	get_read_event_and_umask(cas_count_cfg, *count);
> -	*count += 1;
>  
>  	return 0;
>  }
> 

-- 
 i.