linux-kernel - Re: [PATCH v4 3/7] perf/x86/amd/core: Detect PerfMonV2 support

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Message-ID: <78e001bd-42bd-5481-5a19-1a0bcca9a63c@gmail.com>
Date:   Mon, 9 May 2022 21:01:33 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Sandipan Das <sandipan.das@....com>
Cc:     peterz@...radead.org, bp@...en8.de, dave.hansen@...ux.intel.com,
        acme@...nel.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, namhyung@...nel.org,
        jolsa@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        pbonzini@...hat.com, jmattson@...gle.com, eranian@...gle.com,
        puwen@...on.cn, ananth.narayan@....com, ravi.bangoria@....com,
        santosh.shukla@....com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v4 3/7] perf/x86/amd/core: Detect PerfMonV2 support

On 27/4/2022 7:31 pm, Sandipan Das wrote:

>   	x86_pmu.num_counters	= AMD64_NUM_COUNTERS_CORE;

Thus boot_cpu_has(X86_FEATURE_PERFCTR_CORE) is true.

> +
> +	/* Check for Performance Monitoring v2 support */
> +	if (boot_cpu_has(X86_FEATURE_PERFMON_V2)) {
> +		/* Update PMU version for later usage */
> +		x86_pmu.version = 2;

Is it safe to assume that once AMD CPU has the PERFMON_V2 (or further) bit,

it must also have the PERFCTR_CORE bit set ?