linux-kernel - Re: [PATCH 2/9] perf/x86: core_misc PMU disable and enable support

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Message-ID: <20150717135106.GC18673@twins.programming.kicks-ass.net>
Date:	Fri, 17 Jul 2015 15:51:06 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mark Rutland <mark.rutland@....com>
Cc:	"kan.liang@...el.com" <kan.liang@...el.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"acme@...nel.org" <acme@...nel.org>,
	"eranian@...gle.com" <eranian@...gle.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"adrian.hunter@...el.com" <adrian.hunter@...el.com>,
	"dsahern@...il.com" <dsahern@...il.com>,
	"jolsa@...nel.org" <jolsa@...nel.org>,
	"namhyung@...nel.org" <namhyung@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	luto@...nel.org
Subject: Re: [PATCH 2/9] perf/x86: core_misc PMU disable and enable support

On Fri, Jul 17, 2015 at 03:46:29PM +0200, Peter Zijlstra wrote:
> On Fri, Jul 17, 2015 at 01:11:41PM +0100, Mark Rutland wrote:
> > > diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
> > > index b9826a9..651a86d 100644
> > > --- a/arch/x86/kernel/cpu/perf_event_intel.c
> > > +++ b/arch/x86/kernel/cpu/perf_event_intel.c
> > > @@ -1586,6 +1586,8 @@ static int intel_pmu_handle_irq(struct pt_regs *regs)
> > >  	if (!x86_pmu.late_ack)
> > >  		apic_write(APIC_LVTPC, APIC_DM_NMI);
> > >  	__intel_pmu_disable_all();
> > > +	if (cpuc->core_misc_active_mask)
> > > +		intel_core_misc_pmu_disable();
> > 
> > Huh? Free running counters have nothing to do with the PMU interrupt;
> > there's nothing they can do to trigger it. This feels very hacky.
> > 
> > If this is necessary, surely it should live in __intel_pmu_disable_all?
> > 
> > [...]
> 
> Yeah this is crazy. It should not live in the regular PMU at all, not be
> Intel specific.

lkml.kernel.org/r/2c37309d20afadf88ad4a82cf0ce02b9152801e2.1430256154.git.luto@...nel.org

That does the right thing for free running MSRs.

Take it and expand.
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