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Mon, 7 Sep 2026 14:56:27 -0700 Date: Mon, 7 Sep 2026 14:56:26 -0700 From: Nicolin Chen To: "Kiryl Shutsemau (Meta)" CC: Will Deacon , Robin Murphy , "Joerg Roedel" , Jason Gunthorpe , "Pranjal Shrivastava" , Mostafa Saleh , "Thierry Reding" , Krishna Reddy , Jonathan Hunter , Breno Leitao , Kyle McMartin , Usama Arif , , , , , Subject: Re: [PATCH v5 1/2] iommu/arm-smmu-v3: Add a cmdq_max_entries module parameter Message-ID: References: <20260907095835.1233352-1-kas@kernel.org> <20260907095835.1233352-2-kas@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260907095835.1233352-2-kas@kernel.org> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BY1PEPF0001AE1C:EE_|MN0PR12MB6152:EE_ X-MS-Office365-Filtering-Correlation-Id: db40b927-3502-4567-c0eb-08df0d2ae648 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|82310400026|1800799024|376014|7416014|36860700016|10067099003|6133799003|56012099006|4143699003|11063799006|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: QoKLLn70cqciB5M3IUPp7//9ejYjN34UKhBGDhgG/EzaHwW/DQWTBXitn/T/bFfM+3TxXdEqiysU0Fp/DfmN/OPvns98JGoTI9kP1oZmnbxmRDUpBEmK4gzvdzzEtLdAj0+1ZTTi0s2YqpNrh41ARbmXmYq5f+ZyGOAR6vwts7F0PDNzRuwe52TYLik41HqEwZrG9GVS8No4K9RMGt/I5w7OBq3uGVOxHng1f7Km+node7QogscaLc7Cz1LyoYaDwyRMNbHuEgn92rwkqV2icmA8gnv5YmBZj1D1LV18a4OPfUJnwvy1+GzzCbJBpAvEIYc81tO/kPZE1MyUbWinrEU3R8EO+S2Y58DXafAt+8VO0gNXTCr92cA32pj4l/WcGT+Gqa1jDOW6mGOF6gd/QKd4mqp9B3M1x3MXRW/4nhYutDUrnXMcq0TJ0LMQ+sgL X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Sep 2026 21:56:41.2961 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: db40b927-3502-4567-c0eb-08df0d2ae648 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BY1PEPF0001AE1C.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB6152 On Mon, Sep 07, 2026 at 10:58:34AM +0100, Kiryl Shutsemau (Meta) wrote: I still think that cmdq_max_n_shift can slightly tidy things here. > +static u32 arm_smmu_queue_max_n_shift(u32 ceiling, u32 ent_sz_shift, > + u32 entries) Here, all three inputs would have been "shifts", instead of two "shifts" and one "number of entries". > +{ > + u32 floor = PAGE_SHIFT - ent_sz_shift; > + > + if (!entries) > + return ceiling; > + > + return min(ceiling, max(ilog2(entries), floor)); And I see Sashiko keeps complaining against the ilog2 here: " Does this trigger a build failure due to strict type checking? The ilog2(entries) expression returns a signed int when entries is derived from a runtime value like the module parameter, while floor is explicitly declared as an unsigned u32. Since the kernel's max() macro enforces strict type compatibility, this mismatch evaluates to 0 in the type checking logic, triggering a signedness error during compilation. Should this use max_t(u32, ilog2(entries), floor) instead? " Though Sashiko complained about the min_t() in v4 as well.. With cmdq_max_n_shift, there is no ilog2 and no type mismatch. If you can address or justify the Sashiko finding, I am fine with the cmdq_max_entries though.. So, in either way, the patch looks good to me, Reviewed-by: Nicolin Chen Tested-by: Nicolin Chen