linux-kernel - Re: [PATCH 02/49] x86/cpu: Describe hybrid CPUs in cpuinfo

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Date:   Mon, 8 Feb 2021 11:10:18 -0800
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     Borislav Petkov <bp@...en8.de>, peterz@...radead.org,
        acme@...nel.org, mingo@...nel.org, linux-kernel@...r.kernel.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>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 02/49] x86/cpu: Describe hybrid CPUs in cpuinfo_x86

On Mon, Feb 08, 2021 at 02:04:24PM -0500, Liang, Kan wrote:
> On 2/8/2021 12:56 PM, Borislav Petkov wrote:
> 
> I think it's good enough for perf, but I'm not sure whether other codes need
> the CPU type information.
> 
> Ricardo, do you know?
> 
> Maybe we should implement a generic function as below for this?
> (Not test. Just use as an example.)
> 
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index a66c1fd..679f5fe 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -2056,3 +2056,11 @@ void arch_smt_update(void)
>  	/* Check whether IPI broadcasting can be enabled */
>  	apic_smt_update();
>  }
> +
> +u32 x86_read_hybrid_type(void)
> +{
> +	if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU))
> +		return cpuid_eax(0x0000001a);
> +
> +	return 0;
> +}

Machine check logging will want to include this in "struct mce".

But ok to pick it up with a function like you describe above.

-Tony