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Sat, 22 Aug 2026 11:22:00 -0700 Date: Sat, 22 Aug 2026 11:22:00 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , Subject: Re: [PATCH v9 02/12] iommu/arm-smmu-v3: Skip EVTQ/PRIQ setup in kdump kernel Message-ID: References: <178735412597.18212.17006591038244815148.b4-review@b4> 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: <178735412597.18212.17006591038244815148.b4-review@b4> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN2PEPF000055DC:EE_|BN7PPFB3F5C406F:EE_ X-MS-Office365-Filtering-Correlation-Id: 1485a9af-ab8f-446c-7f2d-08df007a4c6d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|23010399003|376014|36860700016|82310400026|22082099003|18002099003|4143699003|6133799003|10067099003|11063799006|56012099006; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: jfrFjiXkAFEPQQxN0ZYBxlZ85AAs53sidKZ1siwTYzuJznmxvlfXdYf+4FmwpHr+YwmsPrI5f/4/o6tc8KkSXtIBuwzSiUK2k0KddtUasQ2i/HClslbasn3owJ4WaZcc36Gm0tbMp7Pjvhj8RlmsV2xHPYbnfMzzdEOiX9kW8lIEsh1YrnhVbVBAa9MaJ0o7y4k5rK0qZz0Jn3Vo+meJdbYpw/jrSHg4vGClT3WSSh59keRo5q0sr/1u2TKP45bqG+eIs9GzKIhYHuSub7KeWtA47xoYgnordogrd/KjZhB6ULfOHvJepJYUEPZ0lUeqhRGsjJ1UAXxW50gVdEhI6oiRb7brEoDXw41byVjUMaNiCrKZQGTRUAr4aZJAkY3bWEGFDMHc/BVTopwEAcGxfS3uMPaBtkBhCqG4gNDyu4M/fM4pGoqWDo2TYHg4Y22V X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Aug 2026 18:22:17.6333 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 1485a9af-ab8f-446c-7f2d-08df007a4c6d X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.233];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF000055DC.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN7PPFB3F5C406F On Fri, Aug 21, 2026 at 08:15:25PM -0300, Jason Gunthorpe wrote: > > @@ -4821,21 +4821,36 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu) > > - /* PRI queue */ > > - if (smmu->features & ARM_SMMU_FEAT_PRI) { > > + /* > > + * PRI queue > > + * > > + * Do not enable in a kdump case, as we cannot serve page requests. > > + */ > > + if (!is_kdump_kernel() && (smmu->features & ARM_SMMU_FEAT_PRI)) { > > writeq_relaxed(smmu->priq.q.q_base, > > I'm reading this again and wondering why not drop FEAT_PRI much earlier so we > don't need this is_kdump_kernel() here? Yes. I added this: @@ -5371,6 +5351,15 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu) if (arm_smmu_sva_supported(smmu)) smmu->features |= ARM_SMMU_FEAT_SVA; + /* + * A kdump kernel wants neither queue: the crashed kernel's CDs and page + * tables might be corrupted, spamming events, and page requests cannot + * be served. A disabled queue discards new records without raising any + * global error. + */ + if (is_kdump_kernel()) + smmu->features &= ~(ARM_SMMU_FEAT_EVTQ | ARM_SMMU_FEAT_PRI); + dev_info(smmu->dev, "oas %lu-bit (features 0x%08x)\n", smmu->oas, smmu->features); Thanks Nicolin