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Tue, 27 Jan 2026 10:37:45 -0800 Date: Tue, 27 Jan 2026 10:37:44 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: Pranjal Shrivastava , , , , , , , , , , , 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> <20260127170837.GM1134360@nvidia.com> <20260127182348.GP1134360@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260127182348.GP1134360@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN1PEPF00005FFD:EE_|CH2PR12MB9459:EE_ X-MS-Office365-Filtering-Correlation-Id: 8b2439e2-8b27-4890-dd32-08de5dd339fc X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|7416014|376014|36860700013|3613699012; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?iHaK54AGD2cABX2yuSuY/9gw6U78ZCUweZvzMXlQSlghJuDcg6ihfsXHAtG5?= =?us-ascii?Q?VfN5t2S7xhM2roWozzR+MBKLu8r1oeTot8b14Jqsp3lvRM7EEpwk01aYUCDD?= =?us-ascii?Q?KlSJa7xw8w/JM9hUyTeTjUp5GhluPx6ub5eboFmls5tL7Wla6jE6CVQsbNJ1?= =?us-ascii?Q?co69fKUpOf56IbJseVJHLVhq3pykk96oOfPVvo8TMDeEMVPrHMoVBtfm/7AL?= =?us-ascii?Q?J0L5Dim1tq9AxLpdl7wwOFWYT7cvR67Ux674TgYYWw0jRculQVjdpREcOLuQ?= =?us-ascii?Q?qdG5q4uItJ1pJl+kyQJvcwM92Oe1t0sUcyUYScyRJeVTwv3Es99vqkyvbd/x?= =?us-ascii?Q?bLWP0+84ifW6Ml67bVGFidrRbBsu7Fblz/ZiuXca7DZQZF79FQmeGlCDOzDQ?= =?us-ascii?Q?0Pnz345sa2jKHAwY73EXCSlUA7ofafYEbm8VWC4CYssbmGgAAke0qKvFTcdu?= =?us-ascii?Q?W3H3d3vvwBH/8KcPOafnqhejQXBV/Cg6KCCSRfjdx8YORtrZ+luMT92cFzqs?= =?us-ascii?Q?s/0RyM9eGLSKoksUECgcNDFA0Bjn92dC/px1VhgSYujHd66n/lk0aRVfw7jW?= =?us-ascii?Q?RO8qVFLBK5L3owAeip9XL23cgskyiBWVKigjxABVDhhynZyeLywojBS4abWw?= =?us-ascii?Q?3Ij/kFVYkw36HZJ7o0ax3zSM6rOp0W5gaSCri1QX2dzmr/LQgnNS6RSweASY?= =?us-ascii?Q?1FJa+zbuZblSm65ikNCRD8AA3IMlBDXWrVw5Kx9kKH0YlXMd0IVx7aoQU4N8?= =?us-ascii?Q?xTrID4nfQOmAfmd3IC1VfmUSTwavT3Ntkt0U8eo6RNts4R4pXr01235SDS6S?= =?us-ascii?Q?Xxc1RH93YSp2EHvywW6o+0nz2Nvm1n7OpE1/kzHLfAxI+KnirvwClR7VFjNY?= =?us-ascii?Q?HeENaJhsUMd/KmrVATG5naO5WBPiczfxc5POoSGG7aQyriylsClrr+X3IHh1?= =?us-ascii?Q?nlUY4hOl9bhmBXK8FzeGeFGfpBxrxxYppPFE1QHR2m9QMjqajAm3bduhKj0t?= =?us-ascii?Q?sgh/TihRg1bol2IcV3NnQ0Y5cZTj1FB822mTEX8m99uqfVVVzAiqpkLHZ46D?= =?us-ascii?Q?buvIbrZmkYS0Zb8VeyXaxZlPCsxnMKjnjdo5EmoIorxj83jSgmERmngsr+xX?= =?us-ascii?Q?TLrbvqK4xk5r6rKu1VBlj6kTitkpeLVFeUWTvePzvOLXEqf2zWjwzBtXayyC?= =?us-ascii?Q?QhuiYUgA9UT7MxsJhxeqkuYgchq4o2Y5pD5ZHsnM/6RFZiEqbXKFL7a2rty7?= =?us-ascii?Q?OKj6Sq+nxHQq2XZ5buqt6pnM6U1H3URQCFMMgSKqQPeXKgDcqeKQ1ZiPmz6j?= =?us-ascii?Q?OuxRkXjx0nPjAYvY9FoGZTufKZDKKcg2Ty6KOL5xb96CCxZy7NAuEd8lq7Rs?= =?us-ascii?Q?GkfrwK0dIo5GMmD4Cq4pDa5Xokk+sYLOIeAyzWUKGkLeWq482dDatEg/i0ie?= =?us-ascii?Q?R1zYGZFkIHSCUeSvXtR5uBH9JXFWDq9ix5KUX8q8A9OUwdAXjYfQUYhh4IwU?= =?us-ascii?Q?ZiD8WyHa+zpRKbARar1JeiNsW3ybqCO659XR2q+XNCWXHwsPh3PvDHH+8qEP?= =?us-ascii?Q?UMuutBwpk44eKZ7zFHoIXCWk0r4xLHABqKyY4MUF1JM8FHrluKV1Ydri+IRt?= =?us-ascii?Q?KGhX4f9MJUwtiIWiQXjaH98+FucAxqdJ09ZkLvr4H6Fmbzb2p5xf0dHMoflP?= =?us-ascii?Q?DP52Qch/tNW3HSEiMdDSnta9zAY=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)(82310400026)(1800799024)(7416014)(376014)(36860700013)(3613699012);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Jan 2026 18:38:12.3709 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 8b2439e2-8b27-4890-dd32-08de5dd339fc 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: BN1PEPF00005FFD.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH2PR12MB9459 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260127_103823_489973_6824B428 X-CRM114-Status: GOOD ( 19.80 ) 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, Jan 27, 2026 at 02:23:48PM -0400, Jason Gunthorpe wrote: > On Tue, Jan 27, 2026 at 10:07:09AM -0800, Nicolin Chen wrote: > > > My understanding has been that this invalidation can run from an IRQ > > > context - we permit the use of the DMA API from an interrupt handler? > > > > > > I though that for rwsem the read side does not require the _irqsave, > > > even if it is in an irq context, unless the write side runs from an > > > IRQ. > > > > Hmm, is "rwsem" a typo? Because it's rwlock_t, which is spinlock :-/ > > Yeah, sorry > > > > Here the write side always runs from a process context. > > > > > > So the write side will block the IRQ which ensures we don't spin > > > during read in an IRQ. > > > > And, does write_lock_irqsave() disable global IRQ or local IRQ only? > > > > Documentation/locking/locktypes.rst mentions "local_irq_disable()".. > > It will only disable the local IRQ, since it is a spin type lock an IRQ on > another CPU can spin until it is unlocked. > > The main issue is if this CPU takes an IRQ while the write side is > locked and spins, then it will never unlock. Yea, that sounds unsafe. I'll send a v11 with read_lock_irqsave(). We can also pass in iommu_domain to arm_smmu_attach_prepare_invs() that you pointed out in the followup series. Thanks! Nicolin