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Fri, 28 Aug 2026 09:03:35 -0700 Date: Fri, 28 Aug 2026 09:03:33 -0700 From: Nicolin Chen To: Mostafa Saleh CC: , , , , , , , Subject: Re: [PATCH 1/7] iommu/arm-smmu-v3: Ensure L2 tables are visible before L1 ptrs Message-ID: References: <20260828125409.1921538-1-smostafa@google.com> <20260828125409.1921538-2-smostafa@google.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: <20260828125409.1921538-2-smostafa@google.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN2PEPF0000A893:EE_|PH0PR12MB7930:EE_ X-MS-Office365-Filtering-Correlation-Id: a2e2075a-35fe-4c05-28f1-08df051dfece X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|82310400026|36860700016|1800799024|376014|22082099003|18002099003|4143699003|11063799006|56012099006|10067099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 4fs30RlCE06oZCtKfopkPJ4/C+O7Db9TR9C1j+lUhyUG56hCkm+6QjUO+KJGYnKLH4F0Sn2J/aLLlBgorVgdBcBntO6jXH06iM0/2vYjuVcQinBP97Upy6a+SGTxQIAZPmOEmViDSayqI2cm7fQ5AmRdTDpnsC97HFlZmAao3Zsi2/H5ZJknXQMymD4bOdFriOwo4jZKSP2PxhplLUKtKz1DWmOJ+pL/YDC1WAXaHSnO1wRJAHR7n88RILYWCXGkEUC+QMZBAYwK1m2AbBHApwMO8fYIZsvXCWTaFwOL6Sfhk8BZWjEZpSvDCJ15Waaz8HeG2O/pTfRBKoZqWPDlit431KzvIS6/UD3sGLV1dn0mHzulAl1kU6qjkwH6Z8a7L55axmVYOcFWpnuKuPrPdmyaTU3hhMEW9U6sUAvqhaow96fSjUzEylUqGFNIsoUE X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Aug 2026 16:04:09.3832 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a2e2075a-35fe-4c05-28f1-08df051dfece 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: BN2PEPF0000A893.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR12MB7930 On Fri, Aug 28, 2026 at 12:53:36PM +0000, Mostafa Saleh wrote: > Commit 6fabce53f6b9 ("iommu/arm-smmu-v3: Add a missing dma_wmb() for hitless STE update") > adds a dma_wmb() to arm_smmu_write_entry() to make sure stream tables > and context descriptors are observed first. > > However, STE L1 table descriptors are configured directly > via WRITE_ONCE(), where before that they were zeroed with memset() > inside dma_direct_alloc() then written to abort in via memset() also > in arm_smmu_init_initial_stes() without a barrier in both cases which > means that the SMMUv3 can observe the allocated table before the > written descriptors causing it to fetch random data. > > Similarly in arm_smmu_write_cd_l1_desc() where the L1 CD is written > after dma_alloc_coherent() with no barriers. > > Add dma_wmb() in both cases. > > Fixes: 48ec83bcbcf5 ("iommu/arm-smmu: Add initial driver support for ARM SMMUv3 devices") > Reported-by: Sashiko <> > Signed-off-by: Mostafa Saleh Reviewed-by: Nicolin Chen