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Tue, 4 Aug 2026 10:39:15 -0700 Date: Tue, 4 Aug 2026 10:39:13 -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> <20260804165905.GH27883@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: <20260804165905.GH27883@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SA2PEPF000015CC:EE_|IA0PR12MB8745:EE_ X-MS-Office365-Filtering-Correlation-Id: aa008f33-239c-46a1-b054-08def24f5b37 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|36860700016|1800799024|23010399003|82310400026|376014|6133799003|56012099006|11063799006|10067099003|4143699003|3023799007|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: wI3J8hUZJ9MdIIKpHABMcHaA8kVx7PHuoHm0HYjbxYCkMwo2rw2LpstcKJn5Rs6AndVfBbDV0zQx1QydzFVMpmHfWTQ76jJJgczJO657a3WCOzBfhU3LOjv88CG2OvchO5+rSV0RAwA5uNJ/COzinXDNt6Glklvvyq+x1ZYYNpgVFGO8ihm9+5Q90lp81wHJtsnwNUOXGij+TorD2HjfrOiVz1LoVYCkghAh0MVQ//3IYlr1dErNcu7I073gB+sCAFmtSGWMtHQEdqNT7Auu70LHBFqeU8v8klkMajsELyVeu4a63z5w5krnm22cTqYdI1RujHWDuDMwlaYRmtHhnicVQAUyBNgECpa8cEuWdceAYdh9G5cFDjwfFaAMu/LdHCkZCnH9q3YnZgoekht7rsnHgc6gNB/yxo0H1zpESlM7aV+FtoH5wQMKjRCJW5RH X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Aug 2026 17:39:37.8848 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: aa008f33-239c-46a1-b054-08def24f5b37 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: SA2PEPF000015CC.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB8745 On Tue, Aug 04, 2026 at 01:59:05PM -0300, Jason Gunthorpe wrote: > On Tue, Aug 04, 2026 at 09:45:01AM -0700, Nicolin Chen wrote: > > 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? > > I think the ask is to do the tunables first and change your series to > default the tunables instead of doing direct kdump overrides. You mean the driver can override the tunables to 0 in kdump mode, right? Well, we are skipping a lot of things in kdump mode already; it's a very small change to skip EVTQ/PRIQ even without the tunables. If Will prefers this merging sequence, I wouldn't mind changing my series to overriding the tunables. Thanks Nicolin