linux-kernel - Re: [RFC PATCH v2] perf: honouring the cpuid for number of fixed counters in hypervisors

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Message-ID: <20161024165000.GF1075@tassilo.jf.intel.com>
Date:   Mon, 24 Oct 2016 09:50:00 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Imre Palik <imrep.amz@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Stephane Eranian <eranian@...gle.com>,
        Kan Liang <kan.liang@...el.com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        linux-kernel@...r.kernel.org,
        Alexander Kozyrev <alexander.kozyrev@...el.com>,
        Artyom Kuanbekov <artyom.kuanbekov@...el.com>,
        Imre Palik <imrep@...zon.de>, Matt Wilson <msw@...zon.com>,
        David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [RFC PATCH v2] perf: honouring the cpuid for number of fixed
 counters in hypervisors

On Fri, Oct 21, 2016 at 01:18:59AM -0700, Imre Palik wrote:
> From: Imre Palik <imrep@...zon.de>
> 
> perf doesn't seem to honour the number of fixed counters specified by cpuid
> leaf 0xa.  It always assume that Intel CPUs have at least 3 fixed counters.
> 
> So if some of the fixed counters are masked out by the hypervisor, it still
> tries to check/set them.
> 
> This patch makes perf behave nicer when the kernel is running under a
> hypervisor that doesn't expose all the counters.
> 
> This patch contains some ideas from Matt Wilson.

Patch looks good to me.

Reviewed-by: Andi Kleen <ak@...ux.intel.com>

-Andi