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Tue, 28 Jul 2026 22:26:19 -0700 Date: Tue, 28 Jul 2026 22:26:19 -0700 From: Nicolin Chen To: Pranjal Shrivastava CC: , , , , , , , , , , , , , , , , Subject: Re: [PATCH v2 03/11] iommu/arm-smmu-v3: Add arm_smmu_drain_queue_for_iopf() helper Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CY4PEPF0000FCC4:EE_|MW6PR12MB7070:EE_ X-MS-Office365-Filtering-Correlation-Id: 78670cca-19fb-43b9-a4a9-08deed31f6d1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|7416014|1800799024|36860700016|376014|23010399003|56012099006|4143699003|11063799006|10067099003|18002099003|22082099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230040)(82310400026)(7416014)(1800799024)(36860700016)(376014)(23010399003)(56012099006)(4143699003)(11063799006)(10067099003)(18002099003)(22082099003);DIR:OUT;SFP:1101; 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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 Wed, Jul 29, 2026 at 05:15:43AM +0000, Pranjal Shrivastava wrote: > For PRIQ/EVTQ, my only worry was the HW producing more events, > say Device A is detached (we call drain from attach_release) but Device B > (still attached) starts an agressive DMA with multiple PRI requests/evts. > > Maybe we should go back to snapshot based polling for that? If you look closely, "pending" is the snapshot, regardless of the growing prod. * With @until_empty == false (for EVTQ/PRIQ), exit once "drained" reaches its * target: "pending" (i.e. prod0 - cons0, frozen at the entry time): * * cons0 cons prod0 (prod) * |<---- drained ---->| | | * ---+###################+=====================+=============+---> * |<--------------- pending --------------->| Nicolin