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Tue, 25 Aug 2026 11:55:27 +0000 Message-ID: <684784cc-00fd-4c91-81a7-99bc4ef55f0d@intel.com> Date: Tue, 25 Aug 2026 19:55:17 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 8/9] x86/resctrl: Introduce erdt_cpu_has() and erdt_support() To: Reinette Chatre CC: , , , , , , , , , , References: <72f90c77f17acf481f6a5cbcd46d8a1e5ee132f0.1784968626.git.yu.c.chen@intel.com> Content-Language: en-US From: "Chen, Yu C" In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: KU2P306CA0066.MYSP306.PROD.OUTLOOK.COM (2603:1096:d10:39::17) To DM4PR11MB6020.namprd11.prod.outlook.com (2603:10b6:8:61::19) 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: DM4PR11MB6020:EE_|DM6PR11MB4612:EE_ X-MS-Office365-Filtering-Correlation-Id: bebed157-3f81-49aa-a85a-08df029fc12b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|1800799024|366016|376014|7416014|10067099003|56012099006|3023799007|18002099003|22082099003|11063799006|4143699003; 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A >> feature may only be reported as ERDT backed once the low level accessors >> that read its monitoring data via MMIO exist, otherwise callers would > > Are these helpers limited to monitoring ERDT features? First paragraph mentions > "support for an event" and above mentions "read its monitoring data" that > imply these helpers are limited to monitoring features but I do not think this is > the case? > They are not only for monitoring features, but for monitor/allocation features. Let me adjust the description. >> take the ERDT path and find no implementation behind it. Features are >> added to erdt_support() as their MMIO implementations are introduced. > > nit: "are added" -> "should be added" > OK. >> >> Signed-off-by: Chen Yu >> Tested-by: Hongyu Ning >> --- >> v5->v6: >> New patch. Split out of the v5 "x86/resctrl: Introduce helpers to >> read L3 occupancy via MMIO" patch, which carried two logical >> changes. (Reinette Chatre) >> Rename erdt_support_features() to erdt_support(). (Reinette Chatre) >> Reword "expects x86 feature flag as parameters" to "expects an x86 >> feature flag as parameter". (Reinette Chatre) >> Explain in the changelog why erdt_support() returns false here: a >> feature is only reported as ERDT backed once the MMIO accessors that >> read its monitoring data exist. (Reinette Chatre) >> Drop the unused asm/cpufeatures.h include. (Reinette Chatre) >> --- >> arch/x86/include/asm/resctrl.h | 1 + >> arch/x86/kernel/cpu/resctrl/core.c | 23 +++++++++++++++++++++++ >> arch/x86/kernel/cpu/resctrl/erdt.c | 5 +++++ >> arch/x86/kernel/cpu/resctrl/internal.h | 2 ++ >> 4 files changed, 31 insertions(+) >> >> diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h >> index e60c2aea7ebd..5491853113dd 100644 >> --- a/arch/x86/include/asm/resctrl.h >> +++ b/arch/x86/include/asm/resctrl.h >> @@ -49,6 +49,7 @@ DECLARE_STATIC_KEY_FALSE(rdt_enable_key); >> DECLARE_STATIC_KEY_FALSE(rdt_alloc_enable_key); >> DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key); >> >> +bool erdt_cpu_has(int flag); >> int erdt_get_scale(void); >> > > Can this declaration be dropped? Below there is a duplicate declaration > added to arch/x86/kernel/cpu/resctrl/internal.h that should be sufficient? > This declaration is needed by [PATCH 9/9] in resctrl_arch_round_mon_val(), which uses erdt_cpu_has(). Maybe we can drop erdt_cpu_has() from internal.h, although I thought exposing both erdt_cpu_has() and erdt_support() might be useful too. thanks, Chenyu