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Tue, 13 Jan 2026 12:29:12 -0800 Date: Tue, 13 Jan 2026 12:29:11 -0800 From: Nicolin Chen To: Will Deacon , Jason Gunthorpe CC: , , , , , , , , Subject: Re: [PATCH rc v5 1/4] iommu/arm-smmu-v3: Add update_safe bits to fix STE update sequence Message-ID: References: <58f5af553fa7c3b5fd16f1eb13a81ae428f85678.1766093909.git.nicolinc@nvidia.com> <20260108003646.GA537728@nvidia.com> <20260112161010.GC812923@nvidia.com> <20260113161253.GG812923@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260113161253.GG812923@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF00001CDC:EE_|IA1PR12MB6435:EE_ X-MS-Office365-Filtering-Correlation-Id: 5306d447-d491-4df8-07e7-08de52e2792e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700013|376014|82310400026; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?QFctNBq0dj6UJbNajpdRezXL0+wJKE6Pe+G0zMAYjhBke0ExQ/52BIX+nS5z?= =?us-ascii?Q?T0zzaAoqRJ9UKP/EffXXuWi2+s3uEV8ZdG0i2pYU96FXSswVuTKSSN2dz2c2?= =?us-ascii?Q?i6nFUisUQk2P9vxj+D9Qe0OxEXEZIdFlKjswZeIMSSzj7O8u2JeHjVZIOWo0?= =?us-ascii?Q?y7b5VIL+qqvfcKLzwUyE1fXzTPxPCmhAJ+YG9S9I3b2T+1j0WUhESLLlEk+1?= =?us-ascii?Q?7HDHwczS3cbV2dTVvrL5hOEnmGw27nZYcw2B0s9q62bl4yGGyxJAomW9DuqO?= =?us-ascii?Q?Gc2+6cfhVX2O6DkwgU2GgvsHnGVgy3Ax+KVLMwdX3dNHOcR/Bx4XxiJxYOCh?= =?us-ascii?Q?RHpz/6V+/AcrijnvEHbdqGT8Cmd6n3SfNF7uYpxCWEvPnslKD3acKHQBpwoF?= =?us-ascii?Q?FIaBMobXZodc6rMnVX/Eoy/SApWIsmX0WskvrGzr/8DW47gPBYXubXpY9/Hf?= =?us-ascii?Q?Bf7tiSA1Yi0Iq5HdcObplRBSOHjyrE2HhlW9N0GwzGQ73VF1mGSnb8tpUkcQ?= =?us-ascii?Q?3ODsruUTCQSEij6St5bbGEi9CJXs/aLjWSX+i6pkvWWz09ZSeoAAxsOaUoTG?= =?us-ascii?Q?1o8IT7pmDmgFh8sEmLlDkZY28WeoHm0K2J+xs95MLG6nRxpVky0YvgMVF9jb?= =?us-ascii?Q?6Ej3jKuHK/5w02j+iV+bTnPTgxRGnAMPSN74LDwzY1yMS2kt8NdIYVribhZy?= =?us-ascii?Q?xQW+43IFC57XLJ3WtLqF+9a5YxWN5XjMRKFUFTc7rJXKNn7TBzzpBqIO37Qu?= =?us-ascii?Q?6qeS97GVzmxoCqhKXQ9/FmE8/xGMf0QshIqO/4DNkEY0pG0TtQIGwB4LVfGu?= =?us-ascii?Q?1IxYI8EZdjHzWv2kQvBPBv84EFczYwSis0g5cCeCdA14ZfwatRs3n3kUa2if?= =?us-ascii?Q?IiRk9Ppaol1i59f1diM3EaB4M0rZvLZzI9nwtJUq/Pu9QYjbY5TudbC0tyVT?= =?us-ascii?Q?sIuyOztw99xyVJhsMb0mnj9dTr/4143ei6fJpKEyrKzZxPzrU+PNH6BjgL+E?= =?us-ascii?Q?zsFrMCUicXqjul4Bj1SGDAHOH07EPBzXUYqfDY0TYxdOH+7qx6ezlR6K+/q+?= =?us-ascii?Q?ak/HLhtAs81NnIXjGm6Oao5Hn9GM9CvmjJDFkS0ex5aeKeVYAIEO9lhtWedi?= =?us-ascii?Q?pT6k/+x1UIUGOWdLUTLhq9loSt6FDyJ5cnnc3GutwPb9oZ4hwkXs89E+yElx?= =?us-ascii?Q?2Jgw1xGjrJ3jHXtaz7YjDSHU6O2kjkcMIkw0c2W7AFBCC/RoRKs9QadjHiaN?= =?us-ascii?Q?o2bKUYv4wizEcXg1v6mmil85L8LS7S7nbZbMPV7nfNsS4MlCiLde4jiUNYkc?= =?us-ascii?Q?FoPrPCbgo6PvVVf/pRYPHGqmV8+7NMqx0hH55SoCib7aYlq9LdhE93R75F/i?= =?us-ascii?Q?KJhj+muZBl155byFH9xHu9/T7F1I/NLWMoTRIUJnmb78QrXo+bPzVq8azHA/?= =?us-ascii?Q?lqst6yNBiSyU+C0lHA2Dizfbw3OPQo46WcyHec9J+ZHoEIady2ueyJEJsetw?= =?us-ascii?Q?sUfIBeNEw00GUPGXJeVb5jKdWx0W6v6hV+m+audJ/VpP4zGWS33/0Nw5uYBT?= =?us-ascii?Q?M7ndA7enZoFyzwTEu6A=3D?= X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230040)(1800799024)(36860700013)(376014)(82310400026);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Jan 2026 20:29:38.1073 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 5306d447-d491-4df8-07e7-08de52e2792e 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: SJ1PEPF00001CDC.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB6435 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260113_122946_749664_77289508 X-CRM114-Status: GOOD ( 21.50 ) 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 13, 2026 at 12:12:53PM -0400, Jason Gunthorpe wrote: > On Tue, Jan 13, 2026 at 03:05:52PM +0000, Will Deacon wrote: > > I suppose we shouldn't ever see the case that they both have S2S, but > > that's fine. > > If they both have S2S then it works correctly? Any S2S forces EATS to > follow the normal rules. > > > The spec also suggests that there's an additional illegal STE case w/ > > split-stage ATS (EATS_S1CHK) if Config != S1+S2. > > The driver doesn't support that either.. > > It is fixed by checking if new EATS is valid under old config and old > EATS valid under new config. > > Also to support S1CHK someday we cannot allow the hypervisor to leave > S1_S2 and go to S2, since the HW can't deal with that... Perhaps the safe bits should only have EATS_TRANS, excluding S1CHK: -------------------------------------------------------------------------- + * When an STE changes EATS_TRANS, the sequencing code in the attach + * logic already will have the PCI cap for ATS disabled. Thus at this + * moment we can expect that the device will not generate ATS queries + * and so we don't care about the sequencing of EATS. The purpose of + * EATS_TRANS is to protect the system from hostile untrusted devices + * that issue ATS when the PCI config space is disabled. However, if + * EATS_TRANS is being changed, then we must have already trusted the + * device as the EATS_TRANS security block is being disabled. + * + * Note: now the EATS_TRANS update is moved to the first entry_set(). + * Changing S2S and EATS might transiently result in S2S=1 and EATS=1 + * which is a bad STE (see "5.2 Stream Table Entry"). In such a case, + * we can't do a hitless update. Also, STRTAB_STE_1_EATS_S1CHK should + * not be added to the safe bits because it relies on CFG[2:0]=0b111, + * to prevent another bad STE. */ - safe_bits[1] |= cpu_to_le64(STRTAB_STE_1_EATS); + if (!((cur[2] | target[2]) & cpu_to_le64(STRTAB_STE_2_S2S))) + safe_bits[1] |= cpu_to_le64( + FIELD_PREP(STRTAB_STE_1_EATS, STRTAB_STE_1_EATS_TRANS)); -------------------------------------------------------------------------- @will, does this look good to you? I can send a v7 with this. Thanks Nicolin