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Fri, 6 Mar 2026 11:39:11 -0800 Date: Fri, 6 Mar 2026 11:39:09 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v1 2/2] iommu/arm-smmu-v3: Recover ATC invalidate timeouts Message-ID: References: <20260305153911.GT972761@nvidia.com> <20260305234158.GB1651202@nvidia.com> <20260306013347.GD1651202@nvidia.com> <20260306130202.GG1651202@nvidia.com> <20260306192211.GK1651202@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: <20260306192211.GK1651202@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF000023DA:EE_|LV9PR12MB9757:EE_ X-MS-Office365-Filtering-Correlation-Id: 8157cb26-a924-46bc-b69a-08de7bb818a3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|7416014|376014|36860700016; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: Ebmwti4MccIF0avEtdMzqD7QNbeRQoXj+8JOSU/Wl9dnmioHh8BF/RxXhVxxadfbc0cYHrl5ovKtQ5W+8QBLk/tw9pjywnjbIfkR+K1wtyM0Xh+qvDpSfu/i9gy6WW4QvbFNNojmuf/aRW6Vimo5PpipvsoDAEF6HAoCRkIqblA2yYPha8OtThbx0PpxRtcYF3U84MNpqMLkvIzd90ypHyLtbIeuPYbs3cvbHQXVzyKA3usqDcpANTOaF9CgAWnDMSGQ1Oi/fT2chVDl4tpWfxaqZyewsz1aj8kHCLuYDN9+sbdfgq+YOrpmpmJ1S7dZ1z51Iu/3lsFgJyRhRmYKYOSHNAgjPQTLUtEoyd7sJRVNkf65euH7rmm6TrIueta0rjG+KbWN2yHlB5o2dHb+4YZ+qhVOORWC+vUJKp5qFa0D5R6i2Q26XC9zp8ze8Sz0 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Mar 2026 19:39:34.9441 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 8157cb26-a924-46bc-b69a-08de7bb818a3 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: SJ1PEPF000023DA.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV9PR12MB9757 On Fri, Mar 06, 2026 at 03:22:11PM -0400, Jason Gunthorpe wrote: > On Fri, Mar 06, 2026 at 11:20:35AM -0800, Nicolin Chen wrote: > > > In general, the maximum users count of an INV_TYPE_ATS would be 1. > > So, an unref() would be sufficient to mute it, though it'd require > > the unref() API to support a mismatched users counter, because the > > PCI reset in the WQ would block ATS, which would try to unref the > > removed command once again. > > INV_TYPE_ATS_DISABLED could be made to work too.. Overriding the type.. hmm, that's brilliant. Rechecking the unref API, I realized that even the "users" in the latest version isn't atomic anymore. I recall that we are fine to do READ_ONCE/WRITE_ONCE on an int type because invalidation array is serialized by the asid mutex, which wouldn't work either in an ISR or just in the arm_smmu_master/domain_atc_inv()? Thanks Nicolin