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Mon, 23 Mar 2026 18:21:51 -0700 Date: Mon, 23 Mar 2026 18:21:49 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: Samiullah Khawaja , , , , , , , , , , , , , , , , Subject: Re: [PATCH v2 4/7] iommu/arm-smmu-v3: Mark ATC invalidate timeouts via lockless bitmap Message-ID: References: <0c5525367cc67ccc84a675544d1d9f8462704065.1773774441.git.nicolinc@nvidia.com> <20260323235756.GW7340@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260323235756.GW7340@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL02EPF0001A0FD:EE_|SN7PR12MB7884:EE_ X-MS-Office365-Filtering-Correlation-Id: d32e9768-a953-4428-3dba-08de8943c0ea X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|376014|36860700016|7416014|1800799024|56012099003|22082099003|18002099003; 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)(376014)(36860700016)(7416014)(1800799024)(56012099003)(22082099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: RlYBIietkzF4TruvkgxrJrUa7wksAzu8CW7L2wBlaNiEMOmezU1+oc8uLs76bHcP+lphzOongBO3AzTlnwO2Y0TzItjNgnwhXnPlHxNAlbLAtnhFBL+Nb5Lj6p7CtIBYVCvagfrNRYZlW8of6WIprMkDxvOfl2oZ57AdJ7K9ZY4ptg0rUbvufkHTVogKg6KXz/DAPGkjC/Zvau/ToB16mGUTKcc24P/52/X6IDNsnm0OvcVt/xxeVRcd2I/6t7dQU9oF+4HWtRkKx83pTJTukJjNRm05eUfRKFh8WOaqtAfbwQnw6hwpNHnhFJlv1QXYc7FEw9y/5HvMHDkqwEZZgCwa/RP/Pz+VqMopf7uhiGYUVyL/Gfb1W6EoCo/ELTQscuS2wSvuylqROOmSXQ1hsNlogmNwJ5L6G0fARNfA6eajOLC9Wg7UCKBCW6+9KzXz X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Mar 2026 01:22:02.3755 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d32e9768-a953-4428-3dba-08de8943c0ea X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BL02EPF0001A0FD.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB7884 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260323_182209_413862_8CD520AA X-CRM114-Status: GOOD ( 19.56 ) 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 Mon, Mar 23, 2026 at 08:57:56PM -0300, Jason Gunthorpe wrote: > On Wed, Mar 18, 2026 at 04:23:53PM -0700, Nicolin Chen wrote: > > > If the software times out first at 1s, it means the CMDQ is still > > pending on wait for the completion of ATC invalidation. Then, the > > caller sees -ETIMEOUT and tries to bisect the ATC batch or update > > the STE directly, either of which involves CMDQ. But CMDQ has not > > recovered yet. > > Yeah, I don't know if the SW timeout flow is really all that RASy here > right now. Without somehow recovering the CMDQ it is pointless to try > to continue after a timeout. > > And we are really in trouble if things like normal IOTLB invalidation > start to fail. > > I think the right thing is to somehow try to recover the cmdq and then > restart it on the commands that haven't been SYNC'd yet and just keep > trying, maybe with progressively longer timeouts. > > Just ignoring the error and continuing doesn't seem safe. > > But that's something else again, as long as ATC invalidation reliably > hits the HW timeout first we should be OK to ignore it in this > series.. Yea. I will leave a FIXME inline for now. Nicolin