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Fri, 16 Jan 2026 08:58:04 -0800 Date: Fri, 16 Jan 2026 08:58:02 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , Subject: Re: [PATCH v1 2/9] iommu/arm-smmu-v3: Add alloc_id/free_id functions to arm_smmu_invs Message-ID: References: <1541ea4a9e9c935c2f907c0c5f13a4af2bdc2114.1766088962.git.nicolinc@nvidia.com> <20251219170551.GF254720@nvidia.com> <20260102155715.GC125162@nvidia.com> <20260116144120.GM961588@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260116144120.GM961588@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SA2PEPF0000150B:EE_|LV2PR12MB999074:EE_ X-MS-Office365-Filtering-Correlation-Id: 1ba05f26-d5e0-4e81-4b84-08de5520714a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|82310400026|36860700013|1800799024|376014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?NJaeOjYI+uuaj6h5f7AQPxc/Mh/72c7lLwMbaM1azyJrLA0FQ5b3YdZ7bMod?= =?us-ascii?Q?jPF0h8SuvtADu4elsEaiq85pI46njF0eD8FBfLog0S4rjEkgSC9cdVY+V7hy?= =?us-ascii?Q?SW6U0NunLADCsC+LmzFKgEiwlopxmY5AmDA+c1QrDTsnJUmKEjK3dlmT+/ok?= =?us-ascii?Q?MmKpl37xt1FRZWf7fVpDmcbL+fWhBQu8pyD+t3eFcJ0EJUnvkSbR1c/CYoIL?= =?us-ascii?Q?w4gqhnJH/ut0Gj5urW7+yTEtOGVt+jqZe04IASRjKZ3Y5/Rb38AM1/V3NuUl?= =?us-ascii?Q?Hrr9Le4Wivu2B8DZ3Xq/k+28uaoTlDniHBRQq7a3p46t77jvZuPnKjwQjRii?= =?us-ascii?Q?FS1XAPfmFvzO4yr//bPoTvzhF6qvQN2ziCxvv7cHecFJdiHv7fiUdoOnqJ+4?= =?us-ascii?Q?9uScrLIGyeNkFPVPH2eUBdX+KdqABdzo6mqS2ldld/fwgbO32gWI3tUCtwH0?= =?us-ascii?Q?5/C8EVmTKU6RU5UIgBBGPgzIbbLc1S92SOFfIRWy+oeP2vStz6PgmpN82Cr9?= =?us-ascii?Q?Z9M5IqS1o5f/ia0pdeswuqjINRvctg3GXIkV9YBapHDwPyOKZGlakf7RIWqt?= =?us-ascii?Q?HAmOcC/5Sqp1MnhnknOZBu16u65rumCAyvCVpgF08VRw8CRcPOgwS9ysSj2U?= =?us-ascii?Q?/nnIgzxUHNpAno80NaUhuk4LDWXg8TTKwhl2iwYGMRR6vRYL+/EtTafU/RpW?= =?us-ascii?Q?3pgm3P5/Yo11LOQSlFTf9K8XLr3ngYj9pODUeO6W6BEzGRhgsvDgyrQPpE6U?= =?us-ascii?Q?Jdv7n7EC7Ed9tWecV2/SppiHNzudbwEjZITLUCh6iO1IBj9GuPsCzt5vnFoF?= =?us-ascii?Q?TUjePcyBI7KsrlZgh+DDCtiBieabmGrm+h31Q6PGlhH5U/fmCGUL3TRWvwKJ?= =?us-ascii?Q?RAIkjewkxM51USb9zfF2dXC3PNHEAb3i+FC9T0WLgd5DdmPCOsmLKUr1A4rD?= =?us-ascii?Q?Njwzd7Ahw3g8C1B+7OlKZKmYedgoRn0vMf+rCK9IXsqLVPCZw8P+fK34O5Dy?= =?us-ascii?Q?LRYfAHcIqbTAd1Em2NGxfOJV6XWpxVM8YMKS5BPLSYyxbO3wLAeZsgQrWwm2?= =?us-ascii?Q?PxK+b/UgMr536xerLbi7xauglVYNa3CHazeSAdxiKXletauYeb28E3c8M4xh?= =?us-ascii?Q?aKbIQDBTcrDNTaGo6cwxWv7yj/GL6SU6MF6X6Ej26UngN9fzmgRjTab3tb+H?= =?us-ascii?Q?Rb3+/Z/UbM5booPmeAfIdtP4GgNy/HfYpoFqtaOCA7JculbQijZnJxos3IfE?= =?us-ascii?Q?PwBGYbL5PtycxDrjT5MQrbremekxYu90lvpl1OR84kspNA9hKryaZaypWXAH?= =?us-ascii?Q?t+m73nOsevYx+yFoLUocIgUpawCWjQZjTak9e5myeEQ2v/HB3+RlxzM2w7PD?= =?us-ascii?Q?y4fQu+Yw6QLj6SJOAzDiHH+1D2MLnjh8TTsgtGprroNiwaYEeN0Cs7rTSFWM?= =?us-ascii?Q?HA6jAqw8HD8AgiH85ScobMs1hUEWvM7rj8U6ouaabVGiVFhCSW/PFwLPXVhM?= =?us-ascii?Q?BDHHkc2kjcpW8lQhImn9zDORTUQFjSZ0Xg1OdRYvh+VMAvHGJBf9y/5ofwDA?= =?us-ascii?Q?luRsnaXBuLgupVYPwBJkxC9MUC4XpXVGn4lEsNRTQ4C6NYABoDDn61T/k2AG?= =?us-ascii?Q?G+96HLhegfNSiGdY+yi3CyTeJ/js2czu7OGVrEDEdCXLTPLbU7fO29KuGhte?= =?us-ascii?Q?hvLaAg=3D=3D?= X-Forefront-Antispam-Report: CIP:216.228.118.233;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge2.nvidia.com;CAT:NONE;SFS:(13230040)(7416014)(82310400026)(36860700013)(1800799024)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Jan 2026 16:58:15.9961 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 1ba05f26-d5e0-4e81-4b84-08de5520714a 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: SA2PEPF0000150B.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV2PR12MB999074 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260116_085821_405677_723C06AE X-CRM114-Status: GOOD ( 27.39 ) 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 Fri, Jan 16, 2026 at 10:41:20AM -0400, Jason Gunthorpe wrote: > On Thu, Jan 15, 2026 at 09:13:00PM -0800, Nicolin Chen wrote: > > On Fri, Jan 02, 2026 at 11:57:15AM -0400, Jason Gunthorpe wrote: > > > On Tue, Dec 30, 2025 at 10:52:53AM -0800, Nicolin Chen wrote: > > > > Hi Jason, > > > > > > > > On Fri, Dec 19, 2025 at 01:05:51PM -0400, Jason Gunthorpe wrote: > > > > > +static int arm_smmu_get_tag(struct arm_smmu_domain *smmu_domain, > > > > > + struct arm_smmu_master *master, > > > > > + struct arm_vsmmu *vsmmu, > > > > > + struct arm_smmu_iotlb_tag *tag, bool no_alloc) > > > > [...] > > > > > + case ARM_SMMU_DOMAIN_S2: > > > > > + if (smmu_domain->nest_parent) { > > > > > + /* FIXME we can support attaching a nest_parent without > > > > > + * a vsmmu, but to do that we need to fix > > > > > + * arm_smmu_get_id_from_invs() to never return the vmid > > > > > + * of a vsmmu. Probably by making a > > > > > + * INV_TYPE_S2_VMID_VSMMU */ > > > > > + id = vsmmu->vmid; > > > > > + return 0; > > > > > + } > > > > > > > > Would you mind elaborating why arm_smmu_get_id_from_invs() can't > > > > return vsmmu->vmid to share with a naked S2 STE? > > > > > > A "naked" S2 domain doesn't have a pointer to the vsmmu, so it is > > > impossible to get vsmmu->vmid. > > > > An S2 parent domain should be per VM. And a vSMMU on top of an S2 > > should be per SMMU. So, it could have stored a list of vSMMUs and > > device attaching to a naked S2 could match its master->smmu with > > vSMMU->smmu in the list? > > That would cause lifecycle problems if the vSMMU is destroyed > while the nake S2 is still attached and trying to use the vSMMU's > VMID. Well, if vSMMU code does the same get-build-merge in vsmmu_init() and build-unref in vsmmu_destroy(), VMID is basically managed by the invalidation array. Yes, a naked S2 attachment would still use the shared VMID, but I think that's fine for a nesting parent? That being said, the implementation isn't going to be as clean as your approach. Nicolin