From: "Liang, Kan" <kan.liang@linux.intel.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: acme@kernel.org, mingo@redhat.com, peterz@infradead.org,
linux-kernel@vger.kernel.org, namhyung@kernel.org,
ak@linux.intel.com
Subject: Re: [PATCH 1/2] perf vendor events: Add stepping in CPUID string for x86
Date: Thu, 15 Nov 2018 10:53:42 -0500 [thread overview]
Message-ID: <13ef65c9-1622-2bb7-3d61-65f469fe1a10@linux.intel.com> (raw)
In-Reply-To: <20181115152534.GL9600@krava>
>>>> + /*
>>>> + * 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.
>
> right.. did you consider using the wildcard in the map file
> so it'd cover the stepping, having entries like:
>
> GenuineIntel-6-1F-*,v2,nehalemep,core
>
> I haven't thought this one through, but seems we could bypass
> those '-stepping' checks.. but probably other changes would be
> necessary for the wildcard
>
If using wildcard, the full cpuid format is required for all platforms.
The script which using environment string "PERF_CPUID" will definitely
be broken on all platforms.
This patch (non-wildcard) only breaks the script on Skylake server and
Cascadelake server.
I think that's the only drawback of using wildcard.
Thanks,
Kan
next prev parent reply other threads:[~2018-11-15 15:53 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-14 21:24 [PATCH 1/2] perf vendor events: Add stepping in CPUID string for x86 kan.liang
[not found] ` <20181114212416.15665-2-kan.liang@linux.intel.com>
2018-11-15 13:21 ` [PATCH 2/2] perf vendor events: Add JSON metrics for Cascadelake server Jiri Olsa
[not found] ` <3ab97c73-c197-8555-1a35-b54636e667e6@linux.intel.com>
2018-11-15 15:14 ` Jiri Olsa
2018-11-21 12:51 ` Arnaldo Carvalho de Melo
2018-11-21 12:54 ` Arnaldo Carvalho de Melo
2018-11-21 13:02 ` Jiri Olsa
2018-11-21 13:10 ` Arnaldo Carvalho de Melo
2018-11-15 13:53 ` [PATCH 1/2] perf vendor events: Add stepping in CPUID string for x86 Jiri Olsa
2018-11-15 14:26 ` Liang, Kan
2018-11-15 15:18 ` Liang, Kan
2018-11-15 15:33 ` Jiri Olsa
2018-11-15 15:25 ` Jiri Olsa
2018-11-15 15:53 ` Liang, Kan [this message]
2018-11-15 20:02 ` Jiri Olsa
2018-11-15 20:44 ` Jiri Olsa
2018-11-15 21:01 ` Liang, Kan
2018-11-16 2:14 ` Arnaldo Carvalho de Melo
2018-11-20 13:55 ` Liang, Kan
2018-11-21 12:22 ` Arnaldo Carvalho de Melo
2018-11-22 7:14 ` [tip:perf/core] " tip-bot for Kan Liang
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