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Tue, 4 Aug 2026 09:45:02 -0700 Date: Tue, 4 Aug 2026 09:45:01 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: Will Deacon , Kiryl Shutsemau , "Robin Murphy" , Joerg Roedel , "Pranjal Shrivastava" , Breno Leitao , "Kyle McMartin" , Usama Arif , , , Subject: Re: [PATCH v3] iommu/arm-smmu-v3: Shrink command/event/PRI queues in kdump kernel Message-ID: References: <20260706084708.8072-1-kas@kernel.org> <20260804141704.GB27883@nvidia.com> <20260804161918.GG27883@nvidia.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260804161918.GG27883@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN1PEPF0002BA50:EE_|CH3PR12MB9313:EE_ X-MS-Office365-Filtering-Correlation-Id: 17ca485a-60bf-4d6b-8c3e-08def247c733 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|82310400026|1800799024|36860700016|23010399003|22082099003|18002099003|4143699003|11063799006|56012099006|6133799003|10067099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: KGzOfcqXM3EPTx1Wf0+60BpWFpdUhE5mHBvRcCatEKqH6UCBsivUzitWF55Ji5/gGjZO14l3rACsXU9lLK56edUW69t+gLeXAeJ4h1kHQnSe/nJMU9BrQeEWYKzprlZXr1nb9OBw51xYwW1qdpC5tbg6yLk1Lf+/NpQ375L9qlmma3g1LE7U/IIuFlmTS8MBze4g+8i9RUvgO7VA9womP4/G1y8KAHHEuMdPhhl3WwZvUZVm5UYA9DK7KnnXVQhoSSRYh+Aspmw/fRzkMd+Yo5fZtQkZRTfTsBAacQfqRyQED/IZ40lmIaCiJ53F30U+ShVP9tLz/ROwpg16XFsVF3GO0Q4gDoehCySKkZZclsqC819L4ir8S7X+e1DSxGuHSmWPFYXFmKb5OIZOmo301CQzTIhxae6/jBef7TcqUp4EjhDm+SiHbDwGFgZ5nJTj X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Aug 2026 16:45:23.0145 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 17ca485a-60bf-4d6b-8c3e-08def247c733 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: SN1PEPF0002BA50.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB9313 On Tue, Aug 04, 2026 at 01:19:18PM -0300, Jason Gunthorpe wrote: > On Tue, Aug 04, 2026 at 09:04:32AM -0700, Nicolin Chen wrote: > > On Tue, Aug 04, 2026 at 11:17:04AM -0300, Jason Gunthorpe wrote: > > > On Tue, Aug 04, 2026 at 03:02:46PM +0100, Will Deacon wrote: > > > > > Would skipping their allocation when is_kdump_kernel() be acceptable on > > > > > its own, or would you rather see it done differently? > > > > > > > > With Nicolin's patch, we can just avoid allocating the priq and the evtq > > > > entirely in the kdump case. We can then add a cmdline option to control > > > > the maximum size of the cmdq, which is useful regardless of kdump. > > > > > > I would still prefer kdump do this re-sizing automatically, even if we > > > do add a commandline. It makes it easire to deploy than having to know > > > secret command lines :\ > > > > > > So functionally I still think this patch is fine, though yes it points > > > out more things in Nicolin's work too. > > > > I will send a v10 of mine, to skip the EVTQ/PRIQ allocations. > > I think Robin's point is to structure the v10 so you introduce a bunch > of tunables, including something like 0 size to disable a feature. > > Then have kdump default those tunables to the right thing But in kdump, EVTQ/PRIQ are disabled, so my series should have skipped their allocations regardless of the tunables. So, I think the tunables can be done in a separate series. And its use case might not be confined to kdump? Nicolin