linux-kernel - [PATCH] perf cs-etm: Remove duplicate and incorrect aux size checks

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Message-Id: <20211208115435.610101-1-james.clark@arm.com>
Date:   Wed,  8 Dec 2021 11:54:35 +0000
From:   James Clark <james.clark@....com>
To:     mathieu.poirier@...aro.org, coresight@...ts.linaro.org
Cc:     suzuki.poulose@....com, James Clark <james.clark@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] perf cs-etm: Remove duplicate and incorrect aux size checks

There are two checks, one is for size when running without admin, but
this one is covered by the driver and reported on in more detail here
(builtin-record.c):

  pr_err("Permission error mapping pages.\n"
         "Consider increasing "
         "/proc/sys/kernel/perf_event_mlock_kb,\n"
         "or try again with a smaller value of -m/--mmap_pages.\n"
         "(current value: %u,%u)\n",

This had the effect of artificially limiting the aux buffer size to a
value smaller than what was allowed because perf_event_mlock_kb wasn't
taken into account.

The second is to check for a power of two, but this is covered here
(evlist.c):

  pr_info("rounding mmap pages size to %s (%lu pages)\n",
          buf, pages);

Signed-off-by: James Clark <james.clark@....com>
---
 tools/perf/arch/arm/util/cs-etm.c | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
index 293a23bf8be3..8a3d54a86c9c 100644
--- a/tools/perf/arch/arm/util/cs-etm.c
+++ b/tools/perf/arch/arm/util/cs-etm.c
@@ -407,25 +407,6 @@ static int cs_etm_recording_options(struct auxtrace_record *itr,
 
 	}
 
-	/* Validate auxtrace_mmap_pages provided by user */
-	if (opts->auxtrace_mmap_pages) {
-		unsigned int max_page = (KiB(128) / page_size);
-		size_t sz = opts->auxtrace_mmap_pages * (size_t)page_size;
-
-		if (!privileged &&
-		    opts->auxtrace_mmap_pages > max_page) {
-			opts->auxtrace_mmap_pages = max_page;
-			pr_err("auxtrace too big, truncating to %d\n",
-			       max_page);
-		}
-
-		if (!is_power_of_2(sz)) {
-			pr_err("Invalid mmap size for %s: must be a power of 2\n",
-			       CORESIGHT_ETM_PMU_NAME);
-			return -EINVAL;
-		}
-	}
-
 	if (opts->auxtrace_snapshot_mode)
 		pr_debug2("%s snapshot size: %zu\n", CORESIGHT_ETM_PMU_NAME,
 			  opts->auxtrace_snapshot_size);
-- 
2.28.0