netdev - Re: [PATCH 2/3] perf: arm-spe: Fix SPE events with phys addresses

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Date:   Sun, 24 Apr 2022 20:59:51 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Timothy Hayes <timothy.hayes@....com>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        acme@...nel.org, John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH 2/3] perf: arm-spe: Fix SPE events with phys addresses

Hi Timothy,

On Thu, Apr 21, 2022 at 05:52:04PM +0100, Timothy Hayes wrote:
> This patch corrects a bug whereby SPE collection is invoked with
> pa_enable=1 but synthesized events fail to show physical addresses.
> 
> Signed-off-by: Timothy Hayes <timothy.hayes@....com>
> ---
>  tools/perf/arch/arm64/util/arm-spe.c | 10 ++++++++++
>  tools/perf/util/arm-spe.c            |  3 ++-
>  2 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/arch/arm64/util/arm-spe.c b/tools/perf/arch/arm64/util/arm-spe.c
> index af4d63af8072..e8b577d33e53 100644
> --- a/tools/perf/arch/arm64/util/arm-spe.c
> +++ b/tools/perf/arch/arm64/util/arm-spe.c
> @@ -148,6 +148,7 @@ static int arm_spe_recording_options(struct auxtrace_record *itr,
>  	bool privileged = perf_event_paranoid_check(-1);
>  	struct evsel *tracking_evsel;
>  	int err;
> +	u64 bit;
>  
>  	sper->evlist = evlist;
>  
> @@ -245,6 +246,15 @@ static int arm_spe_recording_options(struct auxtrace_record *itr,
>  	 */
>  	evsel__set_sample_bit(arm_spe_evsel, DATA_SRC);
>  
> +	/*
> +	 * The PHYS_ADDR flag does not affect the driver behaviour, it is used to
> +	 * inform that the resulting output's SPE samples contain physical addresses
> +	 * where applicable.
> +	 */
> +	bit = perf_pmu__format_bits(&arm_spe_pmu->format, "pa_enable");
> +	if (arm_spe_evsel->core.attr.config & bit)
> +		evsel__set_sample_bit(arm_spe_evsel, PHYS_ADDR);
> +
>  	/* Add dummy event to keep tracking */
>  	err = parse_events(evlist, "dummy:u", NULL);
>  	if (err)
> diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c
> index 151cc38a171c..1a80151baed9 100644
> --- a/tools/perf/util/arm-spe.c
> +++ b/tools/perf/util/arm-spe.c
> @@ -1033,7 +1033,8 @@ arm_spe_synth_events(struct arm_spe *spe, struct perf_session *session)
>  	memset(&attr, 0, sizeof(struct perf_event_attr));
>  	attr.size = sizeof(struct perf_event_attr);
>  	attr.type = PERF_TYPE_HARDWARE;
> -	attr.sample_type = evsel->core.attr.sample_type & PERF_SAMPLE_MASK;
> +	attr.sample_type = evsel->core.attr.sample_type &
> +				(PERF_SAMPLE_MASK | PERF_SAMPLE_PHYS_ADDR);

I verified this patch and I can confirm the physical address can be
dumped successfully.

I have a more general question, seems to me, we need to change the
macro PERF_SAMPLE_MASK in the file util/event.h as below, so
here doesn't need to 'or' the flag PERF_SAMPLE_PHYS_ADDR anymore.

@Arnaldo, @Jiri, could you confirm if this is the right way to move
forward?  I am not sure why PERF_SAMPLE_MASK doesn't contain the bit
PERF_SAMPLE_PHYS_ADDR in current code.

diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index cdd72e05fd28..c905ac32ebad 100644
--- a/tools/perf/util/event.h
+++ b/tools/perf/util/event.h
@@ -39,7 +39,7 @@ struct perf_event_attr;
         PERF_SAMPLE_TIME | PERF_SAMPLE_ADDR |          \
        PERF_SAMPLE_ID | PERF_SAMPLE_STREAM_ID |        \
         PERF_SAMPLE_CPU | PERF_SAMPLE_PERIOD |         \
-        PERF_SAMPLE_IDENTIFIER)
+        PERF_SAMPLE_IDENTIFIER | PERF_SAMPLE_PHYS_ADDR)

Thanks,
Leo

>  	attr.sample_type |= PERF_SAMPLE_IP | PERF_SAMPLE_TID |
>  			    PERF_SAMPLE_PERIOD | PERF_SAMPLE_DATA_SRC |
>  			    PERF_SAMPLE_WEIGHT | PERF_SAMPLE_ADDR;
> -- 
> 2.25.1
>