linux-kernel - Re: [PATCH v2 5/9] libperf: Add support for user space counter access

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Message-ID: <20200831091134.GC406859@krava>
Date:   Mon, 31 Aug 2020 11:11:34 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Raphael Gault <raphael.gault@....com>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Ian Rogers <irogers@...gle.com>, honnappa.nagarahalli@....com
Subject: Re: [PATCH v2 5/9] libperf: Add support for user space counter access

On Fri, Aug 28, 2020 at 02:56:10PM -0600, Rob Herring wrote:

SNIP

>  
> +void *perf_evsel__mmap(struct perf_evsel *evsel)
> +{
> +	int ret;
> +	struct perf_mmap *map;
> +	struct perf_mmap_param mp = {
> +		.mask = -1,
> +		.prot = PROT_READ | PROT_WRITE,
> +	};
> +
> +	if (FD(evsel, 0, 0) < 0)
> +		return NULL;
> +
> +	map = zalloc(sizeof(*map));
> +	if (!map)
> +		return NULL;
> +
> +	perf_mmap__init(map, NULL, false, NULL);
> +
> +	ret = perf_mmap__mmap(map, &mp, FD(evsel, 0, 0), 0);
> +	if (ret) {
> +		free(map);
> +		return NULL;
> +	}
> +
> +	evsel->mmap = map;
> +	return map->base;
> +}

so this only maps first page, I think we should use different
name and keep perf_evsel__mmap for some generic map with size

perf_evsel__mmap_user
perf_evsel__mmap_zero
...?

not sure.. or we could add size argument

jirka