From:   James Clark <james.clark@arm.com>
To:     mathieu.poirier@linaro.org, coresight@lists.linaro.org
Cc:     suzuki.poulose@arm.com, James Clark <james.clark@arm.com>,
        Mike Leach <mike.leach@linaro.org>,
        Leo Yan <leo.yan@linaro.org>,
        John Garry <john.garry@huawei.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        linux-arm-kernel@lists.infradead.org,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] perf cs-etm: Remove duplicate and incorrect aux size checks
Date:   Wed,  8 Dec 2021 11:54:35 +0000
Message-Id: <20211208115435.610101-1-james.clark@arm.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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@arm.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