linux-kernel - Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC

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Date:	Fri, 19 Oct 2012 18:27:57 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, ak@...ux.intel.com,
	acme@...hat.com, jolsa@...hat.com
Subject: Re: [PATCH 2/2] perf: SNB exclusive PMU access for
 INST_RETIRED:PREC_DIST

On Fri, 2012-10-19 at 16:52 +0200, Stephane Eranian wrote:
> +static int intel_pebs_aliases_snb(struct perf_event *event)
> +{
> +       u64 cfg = event->hw.config;
> +       /*
> +        * for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
> +        * be measured alone on SNB (exclusive PMU access) as per Intel SDM.
> +        */
> +       if ((cfg & INTEL_ARCH_EVENT_MASK) == 0x01c0 && !event->attr.exclusive) {
> +               pr_info("perf: INST_RETIRED.PREC_DIST only works in exclusive mode\n");
> +               return -EINVAL;

This isn't limited to admin, right? So the above turns into a DoS on the
console.

> +       }
> +
> +       return intel_pebs_aliases_ivb(event);
>  } 
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