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Fri, 7 Nov 2025 12:23:57 -0800 Date: Fri, 7 Nov 2025 12:23:56 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , , , Subject: Re: [PATCH v4 3/7] iommu/arm-smmu-v3: Introduce a per-domain arm_smmu_invs array Message-ID: References: <20251107194158.GB1932966@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20251107194158.GB1932966@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ5PEPF000001EA:EE_|IA1PR12MB7592:EE_ X-MS-Office365-Filtering-Correlation-Id: 2602c787-a3de-49c1-a4e6-08de1e3ba369 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|36860700013|1800799024|82310400026; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?UXJ+2SEmaAj9fdJDRmzaeJdJfMY0OX7S6PpZ+/cyhLScThua/LNz0VZWqRRZ?= =?us-ascii?Q?IBq5BRb466AxV7hPx0C/rukznq81/kI2P7RHGjGVdb11RU1KEtTAdT6VSCgZ?= =?us-ascii?Q?mjzi880bl2utS+TiR71Zyahsj3m6f1RQ7jQdmwCXD+mVcv6hY90f6huoWecc?= =?us-ascii?Q?+KvZVSuciHDU7W0KqfuknAr3dLOjTSAEI94SzsgzRYdd3397y/9HxZmSOAOq?= =?us-ascii?Q?Fs7d1r/69CARo6YsBgLTElkeN96PUc0gwBWNm5aD4JG87D+NLSPIZisYLHvQ?= =?us-ascii?Q?aexzClVQpJ/a+1Kdjvf7IRAc69Z58hexSgHsFRYGXUNSlfgsR0Qq8VZuIpa9?= =?us-ascii?Q?cBqMs19Ku9HBUJGoycEvm80T0101eO7dUa4uYImSM7apVloPEhN15B3I6kzF?= =?us-ascii?Q?vj4MkjlwWOkBIrDNFYsGmzT3rTpHUA4sKtaWJ2y9062tzQ6BUdWEL97mn7eO?= =?us-ascii?Q?1HGqw4ghPVDQvfV2A6Ml665a0qMjIjzJ0VVzIZOI/0Fhcu62HiQQtu2n4geY?= =?us-ascii?Q?XYYtuYjalP0UQbJKwEmutyyvftbp5a7RDkUqS/qgEmV5RG7gidoPF499ZjZA?= =?us-ascii?Q?3YugFqR+OcNiUGxaeOdMjJYx1Y2IUg5hHm6ZqVkgQG8yD1IoNEK+ahxJsBcD?= =?us-ascii?Q?sGQYS0T6aOEhu6QAYkg/HvRW5fySm1w/HZBUpNItqLcFPydDxyHBclpWTenH?= =?us-ascii?Q?NSgq9jd5NVrZwWtm7Mq6eKAxilvzSySPulr5+Rs2REsG2byB1+M8FdcasrtE?= =?us-ascii?Q?UMvarIUJNT5iTNh8VY9utZDQfauJyD92IZdpk0N/0SFiF/XTWe1agb251lsM?= =?us-ascii?Q?g59ZPLtkreKTLwfc2a8fdZWCasjB55FULS6YKNcZOjsCoaLQeOopWUPIujU/?= =?us-ascii?Q?qRlEG5bu5no7UUAIaBVYtMI7ub0NrfF5NJfElRbkeJ6iUaaGdIp1ncEk/Nzb?= =?us-ascii?Q?nmTQcQt9YKSjulftb9pE9T7ccftVH54hs7fhpwr8cOKOLj/qUQz1ynE59ypm?= =?us-ascii?Q?7YLU3lrp8T7fu6NorTyRe3ijITO2hwm+H8Vs8BO7wkdRlulZvoijbjtHQ3aQ?= =?us-ascii?Q?keInzSG9DQN+GBrdVExYGGHUpH/mcOtuottjJZKBfXm+RhcVdLH/oNOiL67e?= =?us-ascii?Q?BmjA91r1nseBG6tMGLBehlSB8Eyfy3ygCuBnZUCTegdMoHs+3dO2c1WtuR5t?= =?us-ascii?Q?gede8s5cXF3RbQv9Ah4J1QYJ9Yg3n+YnmP1DClmfHxistVf+klSTPa8fHMmE?= =?us-ascii?Q?LXwvar+kk5pIJOTFM4jZK33GAd/xt2EjUWgmljGzUhi6bI3zPWFVHrws7vGB?= =?us-ascii?Q?MImbGWTGGS0gL9J2a1YeBuj/j58QP2G3paizbBrIKfndPoW2vOUwxLStmy4P?= =?us-ascii?Q?AlKAXaWNsn0T4Y4m1Z/uhRbR7oPccSgKIFgvdzoiQuD5HzNcB3YBTbKxRaXU?= =?us-ascii?Q?b/Q3Xz1d2GXDRayLk2eMo5EiOxx9AaGxA61BiYHR5OMWDYDW0G+DyCthTerv?= =?us-ascii?Q?9CEzVhJsQHqhxDUinb9vw9ZEmRe5fQUSL2EjEQyQyRG6tu85ThpgowSV6W+L?= =?us-ascii?Q?+/vHXyR1uOQpuf0Icn0=3D?= 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)(7416014)(36860700013)(1800799024)(82310400026);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Nov 2025 20:24:22.4883 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2602c787-a3de-49c1-a4e6-08de1e3ba369 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: SJ5PEPF000001EA.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB7592 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251107_122428_177001_1F59FEB0 X-CRM114-Status: GOOD ( 16.96 ) 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, Nov 07, 2025 at 03:41:58PM -0400, Jason Gunthorpe wrote: > On Mon, Oct 27, 2025 at 11:54:17AM -0700, Nicolin Chen wrote: > > +struct arm_smmu_invs *arm_smmu_invs_merge(struct arm_smmu_invs *invs, > > + struct arm_smmu_invs *to_merge) > > +{ > > + struct arm_smmu_invs *new_invs; > > + struct arm_smmu_inv *new; > > + size_t num_trashes = 0; > > + size_t num_adds = 0; > > + size_t i, j; > > + > > + for (i = j = 0; i != invs->num_invs || j != to_merge->num_invs;) { > > + int cmp = arm_smmu_invs_cmp(invs, i, to_merge, j); > > + > > + /* Skip any unwanted trash entry */ > > + if (cmp < 0 && !refcount_read(&invs->inv[i].users)) { > > Do we need cmp < 0 here and in all these other similar ifs? Can't we > just fully ignore trash entries no matter how they cmopare to the > other list? The index "i" might overflow in case of cmp > 1. So, if we don't check cmp, we'd need to check "i != invs->num_invs" instead. > If cmp ==0 and we do num_trash++ then the next iteration will see j > ass cmp > 1 so it will do num_adds++ and the two will cancel out. Yea, cmp == 0 should work with an additional iteration. Perhaps we can do this: + int cmp; + + /* Skip any trash entry */ + if (i != invs->num_invs && !refcount_read(&invs->inv[i].users)) { + num_trashes++; + i++; + continue; + } + + cmp = arm_smmu_invs_cmp(invs, i, to_merge, j); And I will fix the other two places too. Thanks Nicolin