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Date: Wed, 26 Oct 2016 11:16:44 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Imre Palik <imrep.amz@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Andi Kleen <ak@linux.intel.com>, Stephane Eranian <eranian@google.com>,
        Kan Liang <kan.liang@intel.com>,
        David Carrillo-Cisneros <davidcc@google.com>,
        linux-kernel@vger.kernel.org,
        Alexander Kozyrev <alexander.kozyrev@intel.com>,
        Artyom Kuanbekov <artyom.kuanbekov@intel.com>,
        Imre Palik <imrep@amazon.de>, Matt Wilson <msw@amazon.com>,
        David Woodhouse <dwmw@amazon.co.uk>
Subject: Re: [RFC PATCH v2] perf: honouring the cpuid for number of fixed
 counters in hypervisors
Message-ID: <20161026091644.GB3102@twins.programming.kicks-ass.net>
References: <1477037939-15605-1-git-send-email-imrep.amz@gmail.com>
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On Fri, Oct 21, 2016 at 01:18:59AM -0700, Imre Palik wrote:
> +++ b/arch/x86/events/intel/core.c
> @@ -3607,10 +3607,14 @@ __init int intel_pmu_init(void)
>  
>  	/*
>  	 * Quirk: v2 perfmon does not report fixed-purpose events, so
> +	 * assume at least 3 events, when not running in a hypervisor:
>  	 */
> +	if (version > 1) {
> +		if (static_cpu_has(X86_FEATURE_HYPERVISOR))
> +			x86_pmu.num_counters_fixed = edx.split.num_counters_fixed;
> +		else
> +			x86_pmu.num_counters_fixed = max((int)edx.split.num_counters_fixed, 3);
> +	}


I made that:

 	/*
 	 * Quirk: v2 perfmon does not report fixed-purpose events, so
+	 * assume at least 3 events, when not running in a hypervisor:
 	 */
+	if (version > 1) {
+		int assume = 3 * !boot_cpu_has(X86_FEATURE_HYPERVISOR);
+
+		x86_pmu.num_counters_fixed =
+			max((int)edx.split.num_counters_fixed, assume);
+	}
 

Thanks!