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Fri, 26 Jun 2026 03:25:24 +0000 Message-ID: <5d76e776-82d3-4f02-8384-a890349ae96c@intel.com> Date: Thu, 25 Jun 2026 20:25:22 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/3] selftests/resctrl: Skip L3_CAT when no exclusive cache portion exists To: Richard Cheng , , CC: , , , , , , , , , , , =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= References: <20260529022352.8308-1-icheng@nvidia.com> <20260529022352.8308-2-icheng@nvidia.com> From: Reinette Chatre Content-Language: en-US In-Reply-To: <20260529022352.8308-2-icheng@nvidia.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: MW4PR04CA0119.namprd04.prod.outlook.com (2603:10b6:303:83::34) To SJ2PR11MB8370.namprd11.prod.outlook.com (2603:10b6:a03:540::20) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ2PR11MB8370:EE_|LV4PR11MB9489:EE_ X-MS-Office365-Filtering-Correlation-Id: 7fdd66bd-1b6d-4171-d4ff-08ded3328fc9 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|23010399003|376014|7416014|1800799024|18002099003|22082099003|11063799006|5023799004|4143699003|56012099006|6133799003; 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On MPAM, shareable_bits == cbm_mask is a legitimate > state, so there are situations in which no bit can be reported as > exclusive. To make problem clear, please append "... causing the L3_CAT test to fail." > > Previously get_mask_no_shareable() was invoked inside cat_run_test() Written in past tense is confusing since it describes current behavior. > and silently returned -1, which surfaced as a test failure on arm64 > MPAM systems. > > Implement cat_feature_check() to perform the same check at feature-check > time. It prints a diagnostic and returns false so the test case is > skipped instead of failing. The second and third paragraph describes a lot of detail that is clear from the patch. I think these two paragraphs can just be replaced with something brief like: Skip, don't fail, the L3_CAT test when the platform does not have any cache portions that the test can use. > > Tested-by: Chen Yu > Signed-off-by: Richard Cheng > Reviewed-by: Ilpo Järvinen > --- > tools/testing/selftests/resctrl/cat_test.c | 23 +++++++++++++++++++++- > 1 file changed, 22 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c > index f00b622c1460..dc414e55ae94 100644 > --- a/tools/testing/selftests/resctrl/cat_test.c > +++ b/tools/testing/selftests/resctrl/cat_test.c > @@ -378,11 +378,32 @@ static bool noncont_cat_feature_check(const struct resctrl_test *test) > return resource_info_file_exists(test->resource, "sparse_masks"); > } > > +static bool cat_feature_check(const struct resctrl_test *test) > +{ > + unsigned long mask; > + > + if (!test_resource_feature_check(test)) > + return false; > + > + /* > + * The CAT isolation measurement needs a cache portion that no > + * other agent shares. On MPAM the kernel may legitimately report This does not seem to be unique to MPAM (https://lore.kernel.org/lkml/c9bee1ad-10f8-4e69-8d90-609cdd72580e@intel.com/) Perhaps "On MPAM the kernel may" -> "Some platforms may"? > + * all bits as shareable; skip the test if that is the case. > + */ > + if (get_mask_no_shareable(test->resource, &mask)) { > + ksft_print_msg("All %s bits are shareable; cannot measure CAT isolation\n", > + test->resource); > + return false; > + } > + > + return true; > +} > + > struct resctrl_test l3_cat_test = { > .name = "L3_CAT", > .group = "CAT", > .resource = "L3", > - .feature_check = test_resource_feature_check, > + .feature_check = cat_feature_check, > .run_test = cat_run_test, > .cleanup = cat_test_cleanup, > }; Patch looks good to me, thank you. Reinette