linux-kernel - Re: [PATCH v4 2/6] perf/x86: add support for sampling PEBS machine state registers

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Message-ID: <20140905103501.GA30329@gmail.com>
Date:	Fri, 5 Sep 2014 12:35:01 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu,
	acme@...hat.com, jolsa@...hat.com, namhyung@...nel.org,
	dsahern@...il.com
Subject: Re: [PATCH v4 2/6] perf/x86: add support for sampling PEBS machine
 state registers


* Stephane Eranian <eranian@...gle.com> wrote:

> PEBS can capture machine state regs at retiremnt of the sampled
> instructions. When precise sampling is enabled on an event, PEBS
> is used, so substitute the interrupted state with the PEBS state.
> Note that not all registers are captured by PEBS. Those missing
> are replaced by the interrupt state counter-parts.
> 
> Signed-off-by: Stephane Eranian <eranian@...gle.com>
> ---
>  arch/x86/kernel/cpu/perf_event_intel_ds.c |   17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
> index 9dc4199..139a8a5 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
> +++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
> @@ -886,6 +886,23 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
>  	regs.bp = pebs->bp;
>  	regs.sp = pebs->sp;
>  
> +	if (sample_type & PERF_SAMPLE_REGS_INTR) {
> +		regs.ax = pebs->ax;
> +		regs.bx = pebs->bx;
> +		regs.cx = pebs->cx;
> +		regs.si = pebs->si;
> +		regs.di = pebs->di;
> +
> +		regs.r8 = pebs->r8;
> +		regs.r9 = pebs->r9;
> +		regs.r10 = pebs->r10;
> +		regs.r11 = pebs->r11;
> +		regs.r12 = pebs->r12;
> +		regs.r13 = pebs->r13;
> +		regs.r14 = pebs->r14;
> +		regs.r14 = pebs->r15;

Beyond regs.r15, is pebs->dx left out on purpose? It's part of 
pebs_record_hsw so presumably the hardware fills it in.

Thanks,

	Ingo
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