linux-kernel - Re: [PATCH V0 2/3] perf/x86/intel/bm.c: Add Intel Branch Monitoring support

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Date:   Sat, 4 Nov 2017 14:26:11 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Megha Dey <megha.dey@...ux.intel.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, andriy.shevchenko@...ux.intel.com,
        kstewart@...uxfoundation.org, yu-cheng.yu@...el.com,
        len.brown@...el.com, gregkh@...uxfoundation.org,
        peterz@...radead.org, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, namhyung@...nel.org,
        vikas.shivappa@...ux.intel.com, pombredanne@...b.com,
        me@...ehuey.com, bp@...e.de, grzegorz.andrejczuk@...el.com,
        tony.luck@...el.com, corbet@....net, ravi.v.shankar@...el.com,
        megha.dey@...el.com
Subject: Re: [PATCH V0 2/3] perf/x86/intel/bm.c: Add Intel Branch Monitoring
 support

On Fri, Nov 03, 2017 at 11:00:05AM -0700, Megha Dey wrote:

SNIP

> +
> +static void intel_bm_event_update(struct perf_event *event)
> +{
> +	union bm_detect_status cur_stat;
> +
> +	rdmsrl(BR_DETECT_STATUS_MSR, cur_stat.raw);
> +	local64_set(&event->hw.prev_count, (uint64_t)cur_stat.raw);
> +}
> +
> +static void intel_bm_event_stop(struct perf_event *event, int mode)
> +{
> +	wrmsrl(BR_DETECT_COUNTER_CONFIG_BASE + event->id,
> +	       (event->hw.bm_counter_conf & ~1));
> +
> +	intel_bm_event_update(event);
> +}
> +
> +static void intel_bm_event_del(struct perf_event *event, int flags)
> +{
> +	intel_bm_event_stop(event, flags);
> +}
> +
> +static void intel_bm_event_read(struct perf_event *event)
> +{
> +}

should you call intel_bm_event_update in here? so the read syscall
gets updated data in case the case the event is active

jirka