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Fri, 5 Jun 2026 18:43:21 +0000 Message-ID: <03e7cff2-bbfb-4c26-aa2c-a70127683a24@intel.com> Date: Fri, 5 Jun 2026 11:43:19 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/3] arm_mpam: resctrl: Add pass-through resctrl_arch_preconvert_bw() To: Ben Horgan CC: , , , , , , , , , , , , References: <20260515140612.1205251-1-ben.horgan@arm.com> <20260515140612.1205251-3-ben.horgan@arm.com> Content-Language: en-US From: Reinette Chatre In-Reply-To: <20260515140612.1205251-3-ben.horgan@arm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MW4PR04CA0152.namprd04.prod.outlook.com (2603:10b6:303:85::7) To SJ2PR11MB8370.namprd11.prod.outlook.com (2603:10b6:a03:540::20) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ2PR11MB8370:EE_|BY1PR11MB7981:EE_ X-MS-Office365-Filtering-Correlation-Id: 1260062e-3278-4434-6d99-08dec3325185 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|7416014|1800799024|22082099003|18002099003|4143699003|11063799006|56012099006|3023799007; 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As > MPAM uses a binary fixed point fraction format for MBA rather than a > decimal percentage, this introduces rounding errors. > > Without this additional rounding, if the user reads the value in an MB > schema and then writes it back to the schema, the value in hardware won't > change. However, with this additional rounding, this guarantee is broken > for systems with mbw_wd < 7. > > resctrl is introducing resctrl_arch_preconvert_bw() to allow the arch code > to specify the conversion resctrl does to the user-provided bandwidth > value. Add the MPAM version of resctrl_arch_preconvert_bw(). This does no > conversion. > > Signed-off-by: Ben Horgan > --- If rebased on patch #1 proposed changes: | Reviewed-by: Reinette Chatre Reinette