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Wed, 19 Feb 2025 23:12:51 -0800 Date: Wed, 19 Feb 2025 23:12:50 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: Pranjal Shrivastava , "Tian, Kevin" , "corbet@lwn.net" , "will@kernel.org" , "joro@8bytes.org" , "suravee.suthikulpanit@amd.com" , "robin.murphy@arm.com" , "dwmw2@infradead.org" , "baolu.lu@linux.intel.com" , "shuah@kernel.org" , "linux-kernel@vger.kernel.org" , "iommu@lists.linux.dev" , "linux-arm-kernel@lists.infradead.org" , "linux-kselftest@vger.kernel.org" , "linux-doc@vger.kernel.org" , "eric.auger@redhat.com" , "jean-philippe@linaro.org" , "mdf@kernel.org" , "mshavit@google.com" , "shameerali.kolothum.thodi@huawei.com" , "smostafa@google.com" , "ddutile@redhat.com" , "Liu, Yi L" , "patches@lists.linux.dev" Subject: Re: [PATCH v6 14/14] iommu/arm-smmu-v3: Set MEV bit in nested STE for DoS mitigations Message-ID: References: <436ac2021bb3d75114ca0e45f25a6a8257489d3b.1737754129.git.nicolinc@nvidia.com> <20250218185229.GL4099685@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Feb 2025 07:13:09.2182 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d04b840c-62e6-42f8-3303-08dd517e07b6 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: MWH0EPF000A6731.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB6537 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250219_231324_928342_2EB3A114 X-CRM114-Status: GOOD ( 14.74 ) 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 Tue, Feb 18, 2025 at 02:52:29PM -0400, Jason Gunthorpe wrote: > On Tue, Feb 18, 2025 at 06:17:15PM +0000, Pranjal Shrivastava wrote: > > > > Is MEV available only in nested mode? Otherwise it perhaps makes > > > sense to turn it on in all configurations in IOMMUFD paths... > > > > I think the arm-smmu-v3's iommufd implementation only supports nested > > which could be the reason. > > I think starting with MEV in this limited case is reasonable. > > I agree it makes sense to always turn it on from a production > perspective.. Then, I will just add a line to the commit log: "In the future, we might want to enable the MEV for non-nested cases too such as domain->type == IOMMU_DOMAIN_UNMANAGED or even IOMMU_DOMAIN_DMA." Thanks Nicolin