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Fri, 26 Jun 2026 17:43:53 -0700 Received: from nvidia.com (10.127.8.13) by mail.nvidia.com (10.129.68.7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.20 via Frontend Transport; Fri, 26 Jun 2026 17:43:51 -0700 Date: Fri, 26 Jun 2026 17:43:49 -0700 From: Nicolin Chen To: CC: , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v2 00/11] iommu/arm-smmu-v3: Add PRI support Message-ID: References: <2a52ecb1-be8a-4522-aa23-f3277f0555fa@oss.qualcomm.com> 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="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2a52ecb1-be8a-4522-aa23-f3277f0555fa@oss.qualcomm.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS3PEPF0000C37F:EE_|PH8PR12MB6673:EE_ X-MS-Office365-Filtering-Correlation-Id: 9a4498fd-eea9-4242-101b-08ded3e52e89 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|23010399003|376014|7416014|82310400026|1800799024|11063799006|4143699003|56012099006|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 8nLKyoPBnQ9IS6Lo1Ql+tFn8b0jkxXDFITCyz2aI0BLbaiphrpsEiNKCq3IN/cKchDJuLR+D67uhrm7GMhPLpNjvBQw+TrGXBbOCOxufeSL7VrYQCyf6n6CMye3RMOX6c/XJ7Ga6qxKTEWJnZ7snlAdwNbITJ8WJASRRW+uaoyGXlrbBbmNwVGpigVF201OBsbDNcCNDDzmynFnSlOcL4mgEeBeGU9laqtEr7UnCJ4B3ecLkr96y3UdLLe/ICClnD8NlSCof642wOfu2m8cPpq1V0a6voW5ACSCeBFcgE3Lpkdobvy2XYEy+FeKN8n13ds4ObLVxcL2sSMl5Yc6in9IcPxhr7KnRV1rHDHE+mX70gLpoNnVMbkqclVB6Hg3u9br94W+Ql84mUr+iiy5UjyHc9q71D7uL9gITTiEl5f44Q1PJdWoln/sh2thRA4iM X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Jun 2026 00:44:01.3749 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 9a4498fd-eea9-4242-101b-08ded3e52e89 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: DS3PEPF0000C37F.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH8PR12MB6673 On Fri, Jun 26, 2026 at 08:24:31PM +0530, harsha.v@oss.qualcomm.com wrote: > One thing I noticed while reviewing: when arm_smmu_priq_thread() detects > PRIQ overflow, partial faults (non-LAST pages stored via > report_partial_fault()) whose LAST page was lost in the overflow remain > permanently in iopf_param->partial. This is a monotonic memory leak — > it grows with each overflow event. > > Intel VT-d handles this in prq_event_thread() (drivers/iommu/intel/prq.c): > if (head == tail) { > iopf_queue_discard_partial(iommu->iopf_queue); > writel(DMA_PRS_PRO, iommu->reg + DMAR_PRS_REG); > } > > iopf_queue_discard_partial() was written for exactly this scenario. > Could we add the same here arm_smmu_priq_thread() > (drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c) ? > > if (queue_sync_prod_in(q) == -EOVERFLOW) { > dev_err(smmu->dev, "PRIQ overflow detected -- requests lost\n"); > + iopf_queue_discard_partial(smmu->evtq.iopf); > } > > At this point all surviving entries have already been consumed by the > loop above, so discarding unconditionally is safe — implicitly matching > Intel's "head == tail" guard. I will fold it in. Thanks! Nicolin