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Mon, 24 Nov 2025 15:31:16 -0800 Date: Mon, 24 Nov 2025 15:31:15 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: Will Deacon , , , , , , , , , , , Subject: Re: [PATCH v5 4/7] iommu/arm-smmu-v3: Pre-allocate a per-master invalidation array Message-ID: References: <20251124230845.GN153257@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20251124230845.GN153257@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ5PEPF000001E9:EE_|PH7PR12MB6537:EE_ X-MS-Office365-Filtering-Correlation-Id: 2c4140a1-0e4e-463a-abae-08de2bb19a47 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|376014|7416014|1800799024|36860700013; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?NcupdWouvS0BTT8ms1PbzxebPowmQPc1w0sMSiKbQssM8urru9JL7C9AlKRe?= =?us-ascii?Q?CUT5FYxa4AyRfvwecTBSbC4OkByU7hPcntBZvbgFm1XnQLLAOdGIYf6aRm4M?= =?us-ascii?Q?c6VH1JFaFVITKpcOTUusHv8Y04tFJM9/hH+jNWYGvjcgr7SIHWJ/fE8+NtOG?= =?us-ascii?Q?rksYKxLrJ6w3xaJRWCNniATsXsNXtjliknHd5kw5ZsHbojuOxjijGYj5uJxa?= =?us-ascii?Q?cGcRBwzVLCNsrnqIa87Zi3LO2kDifGbmBHBYUcbAuzWoaGrRGT1N8HRuHDUT?= =?us-ascii?Q?JvgA87aVFqoJ8v76mJPn05cczRy92g3WCpcxts4w5zdqH4DT1vrduheN/rla?= =?us-ascii?Q?d7AJilRzn29XasHS/wZLKJwoyhPa+PTYo75QTH9AFhbr2jqqcF5xVpfQxRH7?= =?us-ascii?Q?4gYA78ZxwF0C1zLYfmr0+v2XTfr9JOANwqp6DptqgD8a/Oxg2abdbUum3TdM?= =?us-ascii?Q?wtU4/ZmpmHmnNERoW0spWbtgxWBYib7lfLjQeiFaa+SagIKXOscC8tBJ/VGa?= =?us-ascii?Q?6EBpXrSpHqcETdalhNxpEL+lmtBIY14insEF6gjD0XKmUqYyvzrkU+txaiGy?= =?us-ascii?Q?udbEHIEBDOjqRDARnzvacX95AevaNs+dfYRVHsjgVmzmdjuFuKRmfJjJprlw?= =?us-ascii?Q?Zd8IOwrJp718WGdVmMzNQKPPiBv9JcIiovaMlk9IFLKH2A1CLtahWL4rSqCy?= =?us-ascii?Q?jegKvg89jaFuQDeLo2MxKGOYkByN2aFecFvFmdPV/+WIGp+jMMLelUZ3BNdw?= =?us-ascii?Q?sSF/q/XWvt73t6IeosZGmk8vuZXRHrdG9doa1eFGOZB6oO1XZeJop1nEu5t3?= =?us-ascii?Q?Zjh8jnjvkdyc6xSNKp/X1hht+QM7TyA2WNV8SPdN2CJ7P187U8X/cAiRFLZr?= =?us-ascii?Q?WPu4w6lQ9yGVbLPdCP6vZ7A7UwA5VJ8IlKPDZms1Pil1Moy27h9aLdIVF2WD?= =?us-ascii?Q?K2leAiimPE6iTjCFPwJ1fpzJ65ESds35MK/eRpbG5TYHk3ldHBVX7bhzISsf?= =?us-ascii?Q?vfR9j/8V2Pu1fKLpQCAY+GnyuB1uC8LlLJHuuRkwlY0M/lgMsU1tJMBEcITt?= =?us-ascii?Q?fJ4E0hSletXh1HDP/hyrVzNLlAq1Yx/dMJ561PGeG8atUEatup0N214ZgbeF?= =?us-ascii?Q?npDfX9vU7c4asWF451oB7atNyIEkXI7j/rjXkhpMZ45jqALloVZWo/9iPjGj?= =?us-ascii?Q?kvbaDGGjwpQ/HUNoxwdnAlt7x1RgZzlGACyBIfio3pEz/ZDUVnEeLTVDBA09?= =?us-ascii?Q?SDS9fduZIR+jlIwmwptK9NHDEs+BwmAXCcML0XgN+CXfsP0rxIrwCu3PUyIH?= =?us-ascii?Q?AcQxb6ELUxbYb+GZLSV8+wDtLfUz1RfREff5t2lvSotvILaYfjBBXooYC8zG?= =?us-ascii?Q?NsG3kUGLbfxGtwSKD98ITXxZbeNzytuNT4rrkQl4WwhcAv7IF5pJ5Znt6CRs?= =?us-ascii?Q?dw0wgXiH4DQdaOIdtXgqSpCLQuNCvaGtTp2ryN9YpiU9fefkaHDHVmDm/zuT?= =?us-ascii?Q?Vq28AbwykqCHMWrtEz1mxW7KwVASuQARCj3hBprvy4DNAMaDjTHluH/uIfBy?= =?us-ascii?Q?szxIo2xenhwAylkYn9E=3D?= X-Forefront-Antispam-Report: CIP:216.228.117.160;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge1.nvidia.com;CAT:NONE;SFS:(13230040)(82310400026)(376014)(7416014)(1800799024)(36860700013);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Nov 2025 23:31:32.9464 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2c4140a1-0e4e-463a-abae-08de2bb19a47 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: SJ5PEPF000001E9.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB6537 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251124_153148_801521_5677C5D0 X-CRM114-Status: GOOD ( 22.98 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Nov 24, 2025 at 07:08:45PM -0400, Jason Gunthorpe wrote: > On Mon, Nov 24, 2025 at 02:43:58PM -0800, Nicolin Chen wrote: > > On Mon, Nov 24, 2025 at 09:42:55PM +0000, Will Deacon wrote: > > > On Sat, Nov 08, 2025 at 12:08:05AM -0800, Nicolin Chen wrote: > > > > + /* Put the ids into order for sorted to_merge/to_unref arrays */ > > > > + sort_nonatomic(fwspec->ids, fwspec->num_ids, > > > > + sizeof(fwspec->ids[0]), arm_smmu_ids_cmp, NULL); > > > > + /* ATS case adds num_ids of entries, on top of the base case */ > > > > + master->build_invs = arm_smmu_invs_alloc(2 + fwspec->num_ids); > > > > > > Although I can't point at a specific issue here, I'm nervous about mutating > > > the 'fwspec->ids' array from within the driver, The array isn't allocated > > > or populated directly by the driver and so I don't think we really have any > > > business sorting it. Could we hack iommu_fwspec_add_ids() to keep the array > > > ordered instead? > > > > Yea, I think it makes sense to do it in the core, once we have the > > data structure provided by the core as well. > > I would be more worried about sorting it everywhere for every > driver. I feel confident SMMUv3 doesn't use it, but something really > old and embedded focused like tegra or omap, IDK. > > So I wouldn't propose to change iommu_fwspec_add_ids(). Perhaps a different helper iommu_fwspec_add_ids_sorted()? Drivers can choose to use the sorted version, when they want to implement the invalidation array. And SMMU can be the first only caller. > If you want to be conservative then the thing to do is sort the > master->streams that arm_smmu_insert_master() copies the fwspec > into. It just has to be sorted prior to feeding it into the rbtree. > > Then consistently use master->streams as the sorted list. How about kmemdup() an local id array to bridge betwen fwspec->ids and rbtree? Thanks Nicolin