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Date:   Sat, 16 Jan 2021 13:48:27 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     "Zhang, Rui" <rui.zhang@intel.com>
Cc:     "mingo@redhat.com" <mingo@redhat.com>,
        "acme@kernel.org" <acme@kernel.org>,
        "mark.rutland@arm.com" <mark.rutland@arm.com>,
        "alexander.shishkin@linux.intel.com" 
        <alexander.shishkin@linux.intel.com>,
        "jolsa@redhat.com" <jolsa@redhat.com>,
        "namhyung@kernel.org" <namhyung@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
        "kan.liang@linux.intel.com" <kan.liang@linux.intel.com>,
        "ak@linux.intel.com" <ak@linux.intel.com>
Subject: Re: [PATCH 2/3] perf/x86/rapl: Fix energy counter detection
Message-ID: <YALgm2b0YNkO7Qtd@hirez.programming.kicks-ass.net>
References: <20210115092208.20866-1-rui.zhang@intel.com>
 <20210115092208.20866-2-rui.zhang@intel.com>
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On Sat, Jan 16, 2021 at 08:19:35AM +0000, Zhang, Rui wrote:
> 
> 
> > -----Original Message-----
> > From: Peter Zijlstra <peterz@infradead.org>
> > Sent: Saturday, January 16, 2021 4:03 AM
> > To: Zhang, Rui <rui.zhang@intel.com>
> > Cc: mingo@redhat.com; acme@kernel.org; mark.rutland@arm.com;
> > alexander.shishkin@linux.intel.com; jolsa@redhat.com;
> > namhyung@kernel.org; linux-kernel@vger.kernel.org; x86@kernel.org;
> > kan.liang@linux.intel.com; ak@linux.intel.com
> > Subject: Re: [PATCH 2/3] perf/x86/rapl: Fix energy counter detection
> > Importance: High
> > 
> > On Fri, Jan 15, 2021 at 05:22:07PM +0800, Zhang Rui wrote:
> > > In the RAPL ENERGY_COUNTER MSR, only the lower 32bits represent the
> > > energy counter, and the higher 32bits are reserved.
> > >
> > > Add the MSR mask for these MSRs to fix a problem that the RAPL PMU
> > > events are added erroneously when higher 32bits contain non-zero value.
> > 
> > Why would these high bits be non-zero?
> 
> On SPR platform, the high bits of Psys energy counter are reused for other purpose.
> High bits for other RAPL domains energy counters still return 0.
> 
> I didn't mention this because I thought this patch should be okay as a generic fix.

But it doesn't fix anything.. there's not anything broken, except on
that daft SPR thing.