linux-kernel - Re: [PATCH] x86/perf/zhaoxin: Add stepping check for ZX-C

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Message-ID: <Y+KYx5XcE1IAPPoQ@zn.tnic>
Date:   Tue, 7 Feb 2023 19:30:31 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     silviazhaooc <silviazhao-oc@...oxin.com>
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org, tglx@...utronix.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        cobechen@...oxin.com, louisqi@...oxin.com, silviazhao@...oxin.com,
        tonywwang@...oxin.com, kevinbrace@....com,
        8vvbbqzo567a@...pam.xutrox.com
Subject: Re: [PATCH] x86/perf/zhaoxin: Add stepping check for ZX-C

On Tue, Feb 07, 2023 at 04:42:26PM +0800, silviazhaooc wrote:
> Sorry, I'm a newbie in Linux. Thanks for your reminding.

No worries. :)

> I have carefully checked our product manual for Nano and ZXC FMS.
> 
> For ZXC, there are 2 kinds of FMS：
> 
> 1. Family=6, Model=0x19, Stepping=0-3
> 
> 2. Family=6, Model=F, Stepping=E-F
> 
> For Nano, there is only one kind of FMS:
> 
> Family=6, Model=F, Stepping=[0-A]/[C-D]
> 
> So model = 0xf, steppings >= 0xe or model = 0x19 belong solely to ZXC.
> Nano is an old CPU series which has been stopped production several years
> ago.

Good, which sounds like there won't be any more Nano steppings.

> It will not use the steppings which belong to ZXC.This is an
> unambiguous way to differentiate between ZXC and Nano CPUs.
> 
> Do I need to add the statements in the source code and re-commit the patch?

Yes please. That would explain in a clear way why it is ok to test those
models/steppings. If it turns out that we need this Nano - ZXC
distinction more often, we can do something more involved later.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette