linux-kernel - Re: [PATCH v2 06/17] cpufreq: Fix the efficient idle check for Intel extended Families

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <3123acc7-cc9d-4224-8fe4-7def3c02637b@intel.com>
Date: Thu, 13 Feb 2025 10:49:40 -0800
From: Sohil Mehta <sohil.mehta@...el.com>
To: "Zhang, Rui" <rui.zhang@...el.com>, "Luck, Tony" <tony.luck@...el.com>,
	"x86@...nel.org" <x86@...nel.org>, "dave.hansen@...ux.intel.com"
	<dave.hansen@...ux.intel.com>
CC: "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
	"andrew.cooper3@...rix.com" <andrew.cooper3@...rix.com>,
	"alexander.shishkin@...ux.intel.com" <alexander.shishkin@...ux.intel.com>,
	"luto@...nel.org" <luto@...nel.org>, "david.laight.linux@...il.com"
	<david.laight.linux@...il.com>, "linux-hwmon@...r.kernel.org"
	<linux-hwmon@...r.kernel.org>, "linux-perf-users@...r.kernel.org"
	<linux-perf-users@...r.kernel.org>, "Hunter, Adrian"
	<adrian.hunter@...el.com>, "jdelvare@...e.com" <jdelvare@...e.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...hat.com" <mingo@...hat.com>, "irogers@...gle.com"
	<irogers@...gle.com>, "tglx@...utronix.de" <tglx@...utronix.de>,
	"fenghua.yu@...el.com" <fenghua.yu@...el.com>, "lenb@...nel.org"
	<lenb@...nel.org>, "kan.liang@...ux.intel.com" <kan.liang@...ux.intel.com>,
	"linux@...ck-us.net" <linux@...ck-us.net>, "hpa@...or.com" <hpa@...or.com>,
	"peterz@...radead.org" <peterz@...radead.org>, "mark.rutland@....com"
	<mark.rutland@....com>, "bp@...en8.de" <bp@...en8.de>, "acme@...nel.org"
	<acme@...nel.org>, "rafael@...nel.org" <rafael@...nel.org>,
	"jolsa@...nel.org" <jolsa@...nel.org>, "linux-acpi@...r.kernel.org"
	<linux-acpi@...r.kernel.org>, "namhyung@...nel.org" <namhyung@...nel.org>
Subject: Re: [PATCH v2 06/17] cpufreq: Fix the efficient idle check for Intel
 extended Families

On 2/11/2025 9:35 PM, Zhang, Rui wrote:
>>  static int should_io_be_busy(void)
>>  {
>>  #if defined(CONFIG_X86)
>>  	/*
>> -	 * For Intel, Core 2 (model 15) and later have an efficient
>> idle.
>> +	 * Starting with Family 6 consider all Intel CPUs to have an
>> +	 * efficient idle.
>>  	 */
>>  	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
>> -			boot_cpu_data.x86 == 6 &&
>> -			boot_cpu_data.x86_model >= 15)
>> +	    boot_cpu_data.x86_vfm >= INTEL_PENTIUM_PRO)
> 
> This is "Starting from P4" rather than "Starting from Family 6", right?
> 

As described in the commit message, we are extending this to all
relevant Intel processors. That would include Family 6, Family 15 and
the upcoming Family > 15 processors as well.

A VFM check starting at INTEL_PENTIUM_PRO (Family 6, Model 1) is just a
way to simplify that.