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Tue, 2 Jun 2026 13:32:00 -0700 Date: Tue, 2 Jun 2026 13:31:58 -0700 From: Nicolin Chen To: Will Deacon CC: Ashish Mhetre , , , , , , , Subject: Re: [PATCH v3 2/3] iommu/arm-smmu-v3: Detect Tegra264 erratum Message-ID: References: <20260601104845.995005-1-amhetre@nvidia.com> <20260601104845.995005-3-amhetre@nvidia.com> Precedence: bulk X-Mailing-List: linux-tegra@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: X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PEPF0000000F:EE_|LV2PR12MB5776:EE_ X-MS-Office365-Filtering-Correlation-Id: 8f6fb7b7-e389-40df-6d4d-08dec0e60e2c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|36860700016|82310400026|1800799024|3023799007|22082099003|18002099003|56012099006|4143699003|11063799006; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.117.160;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge1.nvidia.com;CAT:NONE;SFS:(13230040)(376014)(36860700016)(82310400026)(1800799024)(3023799007)(22082099003)(18002099003)(56012099006)(4143699003)(11063799006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: G80tG+C9w+1WhDES+CEtTi1XYt5AJd7PEolxzQKnw4HxWaC32YwNpH8ui61Jj+YdkhosW4KI9KiZbTF2emxGDjZvdI5U9aG/2D34MteuwjkCv4oSYL9hs2LK9lD9yOpeDDeXDWQ3tOecc0YYKBTS5LskB097ITw7kgMKMT5UhbxritS7TMg+46zSzANgH30lCUUxgkwcEp9iP1zATJl9OVKgWmybll+FcVfsUKYEH4SShHQtNe6W87uNMpqPUlmoUmblYNH6x+t2TraUL8/S6MFP5m456j7Hf9DQCWt4cB241dK7taROqclZ5+FQsND/4ntIq5srmsvPNl3py9P42x6Nn/mkfwOMd7roQCli8fTZtN+IXR1vFnxC94XG3qDPgAkTcGUCuwceVprsrevviqc7sBRY3whIGlQZRNJDwffBVjf5DZRbLRkTvqxsm9Th X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Jun 2026 20:32:24.4414 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 8f6fb7b7-e389-40df-6d4d-08dec0e60e2c 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: CH3PEPF0000000F.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV2PR12MB5776 On Tue, Jun 02, 2026 at 09:13:39PM +0100, Will Deacon wrote: > On Mon, Jun 01, 2026 at 10:48:44AM +0000, Ashish Mhetre wrote: > > Tegra264 SMMU is affected by erratum where a TLB entry can survive an > > invalidation that races with concurrent traffic targeting the same > > entry. The hardware-recommended software workaround is to issue every > > CFGI/TLBI command (each followed by CMD_SYNC) twice. The second issue > > is guaranteed to evict the entry. ATC_INV is not affected and must not > > be doubled. > > > > The erratum is not flagged by any SMMUv3 IDR/IIDR register, so it > > cannot be detected from hardware ID. Tegra264 boots from device tree > > only and has no ACPI/IORT support, so detection is through device > > tree only. > > That seems odd to me -- whether the hardware has the erratum is > completely unrelated to whether it probes using DT or ACPI, so I find it > really weird to have the workaround enabled when booting with DT and not > when booting with ACPI. We should have consistent behaviour between the > two. That's a good point. Yet, for ACPI to detect the erratum, we would need a new IORT model or flag, right? That would need to go through the entire ACPI protocol to update SMMU's IORT spec and the header accordingly, which we don't have a use case to do so or to test it. What would you like us to do here for the consistency? Thanks Nicolin