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Fri, 10 Apr 2026 15:06:34 -0700 Received: from Asurada-Nvidia (10.127.8.11) by mail.nvidia.com (10.126.190.181) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.20 via Frontend Transport; Fri, 10 Apr 2026 15:06:34 -0700 Date: Fri, 10 Apr 2026 15:06:32 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , , Subject: Re: [PATCH v4 09/10] iommu/arm-smmu-v3: Remove ASID/VMID from arm_smmu_domain Message-ID: References: <20260410002734.GC3357077@nvidia.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: <20260410002734.GC3357077@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CY4PEPF0000FCC0:EE_|PH8PR12MB7280:EE_ X-MS-Office365-Filtering-Correlation-Id: 60835ea3-1edc-41d5-f815-08de974d75ea X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|36860700016|376014|7416014|56012099003|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: zK59KaLunRjGuVaSq91smkR+2mGYCJOGAgKqZL6lEmYRVnIYnWTDA8WBP44QGXJZvxLvdAEXKqx3amQOtHadGc6Wu4Mk2oJ+fvnOA4q/eSc9gk+lunqzHYvsgvnO/kZ8zIBkft+UGzezu64ZgH5uqWVzBoX0WQdtxal2HaCR92SwBc+ILjCjEghyYEFCrWKaHJr54d8UWJkQ2ZsbnaWV9nQqFELeVCj9oZwhjpbCGDLfmGneUdDZe5uTDC8cvIhwoUe4iLOVs1zJGxT6ijrjLWIuCbvbB/PaSy1Cff8vxvOq1rRVk3OLgUwfwXddj6/n1E4SFlk23hMpDcdprFJKziXJtEX6q6JtR9oDJCsjmGka6pz/azFfjRi2JeqC/sQ1BoNAtoPxZl/67fyyZ+qjCjrF5ypxKaAakE8U0yz+qZl3bE3KCTOnjojSJIUhjwyx X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Apr 2026 22:06:47.7205 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 60835ea3-1edc-41d5-f815-08de974d75ea 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: CY4PEPF0000FCC0.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH8PR12MB7280 On Thu, Apr 09, 2026 at 09:27:34PM -0300, Jason Gunthorpe wrote: > On Thu, Mar 19, 2026 at 12:51:55PM -0700, Nicolin Chen wrote: > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c > > index 846a278fa5469..0e48264ccd01b 100644 > > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c > > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c > > @@ -300,14 +300,6 @@ static void arm_smmu_sva_domain_free(struct iommu_domain *domain) > > */ > > arm_smmu_domain_inv(smmu_domain); > > > > - /* > > - * Notice that the arm_smmu_mm_arch_invalidate_secondary_tlbs op can > > - * still be called/running at this point. We allow the ASID to be > > - * reused, and if there is a race then it just suffers harmless > > - * unnecessary invalidation. > > - */ > > - xa_erase(&arm_smmu_asid_xa, smmu_domain->cd.asid); > > - > > I don't think this artifact has disappeared so the comment should > probably remain too. It has become slightly different because it is > now running under RCU protections so it will clear alot faster. By taking a closer look, I think either the arm_smmu_domain_inv call above or any concurrent arm_smmu_mm_arch_invalidate_secondary_tlbs call is a NOP now? We reworked the ASID lifecycle, which now ends when the last device detaches. So, ASID was free-ed in arm_smmu_iotlb_tag_free() that did a per-ASID flush also. So, when freeing the SVA domain here, the domain should have an empty invalidation array and the HW cache is flushed as well, right? Nicolin