linux-kernel - Re: [PATCH V2 2/25] x86/cpu: Add helper functions to get parameters of hybrid CPUs

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Message-ID: <20210311114814.GA5829@zn.tnic>
Date:   Thu, 11 Mar 2021 12:48:14 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     kan.liang@...ux.intel.com
Cc:     peterz@...radead.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, acme@...nel.org, tglx@...utronix.de,
        namhyung@...nel.org, jolsa@...hat.com, ak@...ux.intel.com,
        yao.jin@...ux.intel.com, alexander.shishkin@...ux.intel.com,
        adrian.hunter@...el.com,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH V2 2/25] x86/cpu: Add helper functions to get parameters
 of hybrid CPUs

On Wed, Mar 10, 2021 at 08:37:38AM -0800, kan.liang@...ux.intel.com wrote:
> From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> 
> On processors with Intel Hybrid Technology (i.e., one having more than one
> type of CPU in the same package), all CPUs support the same instruction
> set and enumerate the same features on CPUID. Thus, all software can run
> on any CPU without restrictions. However, there may be model-specific
> differences among types of CPUs. For instance, each type of CPU may support
> a different number of performance counters. Also, machine check error banks
> may be wired differently. Even though most software will not care about
> these differences, kernel subsystems dealing with these differences must
> know. Add a new member to cpuinfo_x86 that subsystems can query to know
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

That is not the case anymore.

And it looks like the IPIing is going away too, which is good.

Thx.

-- 
Regards/Gruss,
    Boris.

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