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

[Liang, Kan]

On 11/15/2018 8:53 AM, Jiri Olsa wrote:
> On Wed, Nov 14, 2018 at 01:24:15PM -0800, kan.liang@xxxxxxxxxxxxxxx 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?

User may set cpuid by environment string "PERF_CPUID", which may not be 
full format.

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

Sure.

> > +
> > +	/*
> > +	 * 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?

It's from previous common code. As my understanding, it just double 
check the matched strings. There is no harmful. So I keep it.

Thanks,
Kan