linux-kernel - Re: [PATCH v5 12/20] x86: perf: intel

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Date:	Fri, 24 Oct 2014 10:49:33 +0300
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Robert Richter <rric@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>, kan.liang@...el.com,
	adrian.hunter@...el.com, acme@...radead.org
Subject: Re: [PATCH v5 12/20] x86: perf: intel_pt: Intel PT PMU driver

Peter Zijlstra <peterz@...radead.org> writes:

> On Mon, Oct 13, 2014 at 04:45:40PM +0300, Alexander Shishkin wrote:
>> +++ b/arch/x86/kernel/cpu/perf_event_intel.c
>> @@ -1528,6 +1528,14 @@ again:
>>  	}
>>  
>>  	/*
>> +	 * Intel PT
>> +	 */
>> +	if (__test_and_clear_bit(55, (unsigned long *)&status)) {
>> +		handled++;
>> +		intel_pt_interrupt();
>> +	}
>> +
>
> How does the PT interrupt interact with the regular PMI? In particular
> does it respect stuff like FREEZE_ON_PMI etc?

It ignores the FREEZE_ON_PMI bit. I stop it by hand inside the PMI
handler, so you can see parts of the handler in the trace if you're
tracing the kernel.

Regards,
--
Alex
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