linux-kernel - Re: [PATCH 1/2] perf vendor events: Add stepping in CPUID string for x86

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Date:   Thu, 15 Nov 2018 14:53:47 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     kan.liang@...ux.intel.com
Cc:     acme@...nel.org, mingo@...hat.com, peterz@...radead.org,
        linux-kernel@...r.kernel.org, namhyung@...nel.org,
        ak@...ux.intel.com
Subject: Re: [PATCH 1/2] perf vendor events: Add stepping in CPUID string for
 x86

On Wed, Nov 14, 2018 at 01:24:15PM -0800, kan.liang@...ux.intel.com wrote:

SNIP

> diff --git a/tools/perf/arch/x86/util/header.c b/tools/perf/arch/x86/util/header.c
> index fb0d71afee8b..b428a4b00bf7 100644
> --- a/tools/perf/arch/x86/util/header.c
> +++ b/tools/perf/arch/x86/util/header.c
> @@ -4,6 +4,7 @@
>  #include <stdio.h>
>  #include <stdlib.h>
>  #include <string.h>
> +#include <regex.h>
>  
>  #include "../../util/header.h"
>  
> @@ -70,9 +71,73 @@ get_cpuid_str(struct perf_pmu *pmu __maybe_unused)
>  {
>  	char *buf = malloc(128);
>  
> -	if (buf && __get_cpuid(buf, 128, "%s-%u-%X$") < 0) {
> +	if (buf && __get_cpuid(buf, 128, "%s-%u-%X-%X$") < 0) {
>  		free(buf);
>  		return NULL;
>  	}
>  	return buf;
>  }
> +
> +/* Full CPUID format for x86 is vendor-family-model-stepping */
> +static bool is_full_cpuid(const char *cpuid)
> +{
> +	const char *tmp = cpuid;
> +	int count = 0;
> +
> +	while ((tmp = strchr(tmp, '-')) != NULL) {
> +		count++;
> +		tmp++;
> +	}
> +
> +	if (count == 3)
> +		return true;
> +
> +	return false;
> +}
> +
> +int strcmp_cpuid_str(const char *mapcpuid, const char *cpuid)
> +{
> +	regex_t re;
> +	regmatch_t pmatch[1];
> +	int match;
> +	bool full_mapcpuid = is_full_cpuid(mapcpuid);
> +	bool full_cpuid = is_full_cpuid(cpuid);

cpuid will be always full from now right? why do we need to check it?

also please move this to arch/x86/util/pmu.c
so it matches the weak function object

> +
> +	/*
> +	 * Full CPUID format is required to identify a platform.
> +	 * Error out if the cpuid string is incomplete.
> +	 */
> +	if (full_mapcpuid && !full_cpuid) {
> +		pr_info("Invalid CPUID %s. Full CPUID is required, "
> +			"vendor-family-model-stepping\n", cpuid);
> +		return 1;
> +	}
> +
> +	if (regcomp(&re, mapcpuid, REG_EXTENDED) != 0) {
> +		/* Warn unable to generate match particular string. */
> +		pr_info("Invalid regular expression %s\n", mapcpuid);
> +		return 1;
> +	}
> +
> +	match = !regexec(&re, cpuid, 1, pmatch, 0);
> +	regfree(&re);
> +	if (match) {
> +		size_t match_len = (pmatch[0].rm_eo - pmatch[0].rm_so);
> +		size_t cpuid_len;
> +
> +		/* If the full CPUID format isn't required,
> +		 * ignoring the stepping.
> +		 */
> +		if (!full_mapcpuid && full_cpuid)
> +			cpuid_len = strrchr(cpuid, '-') - cpuid;
> +		else
> +			cpuid_len = strlen(cpuid);
> +
> +
> +		/* Verify the entire string matched. */
> +		if (match_len == cpuid_len)
> +			return 0;

why is this necessary?

thanks,
jirka