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Mon, 8 Sep 2025 11:45:57 -0700 Date: Mon, 8 Sep 2025 11:45:54 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , , , , , , Subject: Re: [PATCH rfcv1 7/8] iommu/arm-smmu-v3: Add arm_smmu_invs based arm_smmu_domain_inv_range() Message-ID: References: <8c4c5aec144f65cfd1fcef2eafb395876dac97ec.1755131672.git.nicolinc@nvidia.com> <20250827184923.GC2206304@nvidia.com> <20250908153911.GC789684@nvidia.com> <20250908182404.GH789684@nvidia.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="us-ascii" Content-Disposition: inline In-Reply-To: <20250908182404.GH789684@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN3PEPF0000B06E:EE_|DM6PR12MB4058:EE_ X-MS-Office365-Filtering-Correlation-Id: 0823ee2d-3ba6-4a9a-5451-08ddef07fe66 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|82310400026|1800799024|36860700013|3613699012; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Sep 2025 18:46:16.6653 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0823ee2d-3ba6-4a9a-5451-08ddef07fe66 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: BN3PEPF0000B06E.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4058 On Mon, Sep 08, 2025 at 03:24:04PM -0300, Jason Gunthorpe wrote: > On Mon, Sep 08, 2025 at 11:19:40AM -0700, Nicolin Chen wrote: > > So, would it be better to just always take the read lock, while > > applying the ATS condition to the writer side: > > No, the whole optimization is to avoid read side locking on the fairly > common no-ATS case. > > Always taking the lock destroys that. OK. I skimmed through the lock_acquire(). It seems to be a bit heavier than I expected. Perhaps this is the part we wanted to avoid. Thanks Nicolin