linux-kernel - Re: [PATCH] x86: Prefer MWAIT over HALT on AMD processors

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Date:   Thu, 7 Apr 2022 02:19:28 +0000
From:   Wen Pu <puwen@...on.cn>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     Wyes Karny <wyes.karny@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Lewis.Carroll@....com" <Lewis.Carroll@....com>,
        "Mario.Limonciello@....com" <Mario.Limonciello@....com>,
        "gautham.shenoy@....com" <gautham.shenoy@....com>,
        "Ananth.Narayan@....com" <Ananth.Narayan@....com>,
        "bharata@....com" <bharata@....com>,
        "len.brown@...el.com" <len.brown@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "chang.seok.bae@...el.com" <chang.seok.bae@...el.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "metze@...ba.org" <metze@...ba.org>,
        "zhengqi.arch@...edance.com" <zhengqi.arch@...edance.com>,
        "mark.rutland@....com" <mark.rutland@....com>
Subject: Re: [PATCH] x86: Prefer MWAIT over HALT on AMD processors


On 2022/4/5 22:07, Peter Zijlstra wrote:
> On Tue, Apr 05, 2022 at 06:30:21PM +0530, Wyes Karny wrote:
>> +static inline bool early_mwait_supported(const struct cpuinfo_x86 *c)
>> +{
>> +	if (c->x86_vendor == X86_VENDOR_INTEL)
>> +		return true;
>> +
>> +	if (c->x86_vendor == X86_VENDOR_AMD && cpu_has(c, X86_FEATURE_ZEN))
> 
> What about Hygon? For some reason you guys don't co-ordinate and we end
> up getting endless 'make-same' patches, sometimes separated by years :/


Hygon CPU supports MWAIT, so this patch also make sense for Hygon :)
As Dave Hansen and Lewis Caroll mentioned in the following threads,
Hygon has already set the X86_FEATURE_ZEN flag, so it's better to
use X86_FEATURE_ZEN for all Zen uarch CPUs.

>> +		return true;
>> +
>> +	return false;
>> +}

-- 
Regards,
Pu Wen