linux-kernel - Re: [PATCH V2 1/25] x86/cpufeatures: Enumerate Intel Hybrid Technology feature bit

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Date:   Wed, 10 Mar 2021 21:01:47 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     kan.liang@...ux.intel.com, 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,
        "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 1/25] x86/cpufeatures: Enumerate Intel Hybrid
 Technology feature bit

On Wed, Mar 10, 2021 at 11:46:44AM -0800, Ricardo Neri wrote:
> But this series provides the use case, right? Kan's patches handle PMU counters
> that may differ cross types of CPUs. In patch 2, get_hybrid_params()
> needs to check first if X86_FEATURE_HYBRID_CPU is enabled before
> querying the hybrid parameters. Otherwise, we would need to rely on the
> maximum level of CPUID, which may not be reliable.

On Wed, Mar 10, 2021 at 11:33:54AM -0800, Srinivas Pandruvada wrote:
> We are working on changes to P-State driver for hybrid CPUs using this
> define. They are still work in progress.
> But this patch can be submitted later with our set of changes.

Answering to both with a single mail:

I don't have a problem with X86_FEATURE_HYBRID_CPU - I simply don't want
to show "hybrid_cpu" in /proc/cpuinfo unless there's a valid use case
for userspace to know that it is running on a hybrid CPU.

-- 
Regards/Gruss,
    Boris.

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