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Mon, 26 Jan 2026 09:50:29 -0800 Received: from Asurada-Nvidia (10.127.8.14) by mail.nvidia.com (10.126.190.180) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.20 via Frontend Transport; Mon, 26 Jan 2026 09:50:29 -0800 Date: Mon, 26 Jan 2026 09:50:27 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: Will Deacon , , , , , , , , , , , Subject: Re: [PATCH v9 6/7] iommu/arm-smmu-v3: Add arm_smmu_invs based arm_smmu_domain_inv_range() Message-ID: References: <06999367d001283744fd98eb7c1823afd516ce84.1766174731.git.nicolinc@nvidia.com> <20260123200327.GF1134360@nvidia.com> <20260126152019.GK1134360@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260126152019.GK1134360@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PEPF000044F6:EE_|DM6PR12MB4122:EE_ X-MS-Office365-Filtering-Correlation-Id: 42c0ca70-cb8f-44c1-c677-08de5d037264 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|1800799024|7416014|376014|82310400026|3613699012; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Jan 2026 17:50:51.7650 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 42c0ca70-cb8f-44c1-c677-08de5d037264 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: CO1PEPF000044F6.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4122 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260126_095105_802438_717C6ACB X-CRM114-Status: GOOD ( 22.43 ) 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, Jan 26, 2026 at 11:20:19AM -0400, Jason Gunthorpe wrote: > On Mon, Jan 26, 2026 at 01:01:16PM +0000, Will Deacon wrote: > > If we've written a new (i.e. previously invalid) valid PTE to a > > page-table and then we install that page-table into an STE hitlessly > > (let's say we write the S2TTB field) then isn't there a window before we > > do the STE invalidation where the page-table might be accessible to the > > SMMU but the new PTE is still sitting in the CPU? > > Hmm! Yes seems like it. > > However, that's seems like a general bug, if we allocate an > iommu_domain and immediately hitlessly install it, then there would be > no dma_wmb() for the page table memory prior to the earliest point the > HW is able to read the STE. > > What I wrote is is how things are intended to work, so lets fix it > with this? > > @@ -1173,6 +1173,13 @@ void arm_smmu_write_entry(struct arm_smmu_entry_writer *writer, __le64 *entry, > __le64 unused_update[NUM_ENTRY_QWORDS]; > u8 used_qword_diff; > > + /* > + * Many of the entry structures have pointers to other structures that > + * need to have their updates be visible before any writes of the entry > + * happen. > + */ > + dma_wmb(); > + > used_qword_diff = > arm_smmu_entry_qword_diff(writer, entry, target, unused_update); > if (hweight8(used_qword_diff) == 1) { I will attach this patch as PATCH-1 in v10. Thanks Nicolin