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Fri, 10 Jan 2025 10:38:44 -0800 Date: Fri, 10 Jan 2025 10:38:42 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v5 08/14] iommufd/viommu: Add iommufd_viommu_report_event helper Message-ID: References: <20250110174132.GH396083@nvidia.com> Precedence: bulk X-Mailing-List: linux-doc@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: <20250110174132.GH396083@nvidia.com> X-NV-OnPremToCloud: AnonymousSubmission X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF00002312:EE_|DM6PR12MB4106:EE_ X-MS-Office365-Filtering-Correlation-Id: b9bf17dd-3fd4-4f96-f598-08dd31a60671 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|1800799024|36860700013|82310400026|7416014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?PTg0QetQcSysdb80Wq+OtRA1Y2qYAccNRMMf6kzqXTvHTgZr9N8jcUGFxxSH?= =?us-ascii?Q?DW6NbaGzpwDVBXNFSKuWFQX7NG8aNvgCernyHtxyaQ55iT7UXNpMeBsd7QfA?= =?us-ascii?Q?vSxXLZx9EYL+tcHahtvmAlQCEarrFHTBERla5tqv/Ayi8pcQqrROK3X2bCmr?= =?us-ascii?Q?cfITHsSAxiAk+QZH8zGw4hBSL6AMcejRIQVFSnVpw7O4CX/pyKEDlZrTPjEt?= =?us-ascii?Q?hikfsMF3JYmwHVu9qyAZK3Z6K7PYLp4g602X/ArJ1ty2yYNZdKpkJ92rYU3X?= =?us-ascii?Q?4KiVEerLfmnpIQO/gbE0JoXMFYcvobfyEn2CCJhynRL1WQcsy844Pjbd0+Fh?= =?us-ascii?Q?99pr2WKbMyUSbMzKRa7Ur4zSwjlk6KAQhgtm7CP2mJeFMdQzspcWcDgj4Zpa?= =?us-ascii?Q?1v8A19t8R1796XG8LkYpEA1ATqZXe21EHR+CXAoTo1bI2FZL0RXIwJlJ0A+1?= =?us-ascii?Q?YeJPJ8Bc3iFUx6eKiVcyWZVo2zUcRcGQpOq70PzhSUA5GiPB9C/iwIb287E3?= =?us-ascii?Q?5t4ZEueqJmh8fniC5CbmJ9VPe7BxkJxDS5szu0iTCGrZLv0rmkNqwrX0c2eQ?= =?us-ascii?Q?X5bExICjnHZ3mVeif6Oz/pwvuzSfcUH1GcQ+2F7O69ovWsz8m0gCjU6bzq5P?= =?us-ascii?Q?VBlwElev+dV3rVABQXN52ogGBy4NU9VFI5hjcg6kjAJTmUrjIfdiKGeX8cuS?= =?us-ascii?Q?/vBlVBHtXasEa8xMVIGYKM+J0D+HKr9+LhY6cj+miZnXDPeq8ZzcSvA4hoZ0?= =?us-ascii?Q?7ra7qmMldsNybLly+X/1tGpAlA6xAzkkWgXrXLjCa3yINMZ3YGHsPYCRqirN?= =?us-ascii?Q?DNAAYgpfBUb+px+3d7+FNdJignNKC1hQ/evJtqycPnPLeJ20iqlnHQIRFSFK?= =?us-ascii?Q?GihF+G7OeoC62vwOs236j7VfI409Zv2DHKCQShKoeKj2SiWfiuRs0C1eeKxD?= =?us-ascii?Q?ie4KrGzRJ/mgVOcuN9JImrZtreLz1hVUVG+uSqunUlS2UGuGi++aoJ70pu2N?= =?us-ascii?Q?ziyoBypUpQNAwmijKtXYrqUkU/Ny1qMzrNyEDxUp3vHelxWcojbqr8INe5/y?= =?us-ascii?Q?fAIWQ7Dza4paZmmQ9htAgVnq1WnhI8fnVrZYSthEnEZIkGxvpG5lZ1yBJGmS?= =?us-ascii?Q?HkWp/+6UaBcXDchRZkkiysTLlt4JnjmPkdjYVh5DyQAESZupQslDDunNDCDu?= =?us-ascii?Q?l2PFCfTocDXx84jJoBOlFymn6tm0grbjEITtIE8lBTqvCsUVefhPmjTeQZYG?= =?us-ascii?Q?RYHcVqsbj6CnWkQPWEwTbRNl4OFt2wD7ntE6qU3+tRR4JiY27DqBNKMpjCnF?= =?us-ascii?Q?/ZLpE+YcwVcEpCHVp2ZVt4YysPF8hQfBfLIelYNDLYQGzhXaapNA8nJpIZXI?= =?us-ascii?Q?iL0vsAkbgAXlRWZFbwWraNVmq/I4lwxCIllYFkOQpAXSw9fDKt6Byvhptzex?= =?us-ascii?Q?/+xqgDxAVkCmr49yV/3tTwrxAONxenArruOmfQxg01O80KFD11Pc2w8xSnGf?= =?us-ascii?Q?joI4VMSVl8Ny9UE=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)(376014)(1800799024)(36860700013)(82310400026)(7416014);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Jan 2025 18:38:49.8629 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b9bf17dd-3fd4-4f96-f598-08dd31a60671 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: SJ1PEPF00002312.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4106 On Fri, Jan 10, 2025 at 01:41:32PM -0400, Jason Gunthorpe wrote: > On Tue, Jan 07, 2025 at 09:10:11AM -0800, Nicolin Chen wrote: > > +/* > > + * Typically called in driver's threaded IRQ handler. > > + * The @type and @event_data must be defined in include/uapi/linux/iommufd.h > > + */ > > +int iommufd_viommu_report_event(struct iommufd_viommu *viommu, > > + enum iommu_veventq_type type, void *event_data, > > + size_t data_len) > > +{ > > + struct iommufd_veventq *veventq; > > + struct iommufd_vevent *vevent; > > + int rc = 0; > > + > > + if (!viommu) > > + return -ENODEV; > > + if (WARN_ON_ONCE(!viommu->ops || !viommu->ops->supports_veventq || > > + !viommu->ops->supports_veventq(type))) > > + return -EOPNOTSUPP; > > + if (WARN_ON_ONCE(!data_len || !event_data)) > > + return -EINVAL; > > + > > + down_read(&viommu->veventqs_rwsem); > > + > > + veventq = iommufd_viommu_find_veventq(viommu, type); > > + if (!veventq) { > > + rc = -EOPNOTSUPP; > > + goto out_unlock_veventqs; > > + } > > + > > + vevent = kmalloc(struct_size(vevent, event_data, data_len), GFP_KERNEL); > > + if (!vevent) { > > + rc = -ENOMEM; > > + goto out_unlock_veventqs; > > + } > > + memcpy(vevent->event_data, event_data, data_len); > > The page fault path is self limited because end point devices are only > able to issue a certain number of PRI's before they have to stop. > > But the async events generated by something like the SMMU are not self > limiting and we can have a huge barrage of them. I think you need to > add some kind of limiting here otherwise we will OOM the kernel and > crash, eg if the VM spams protection errors. Ack. I think we can just use an atomic counter in the producer and consumer functions. > The virtual event queue should behave the same as if the physical > event queue overflows, and that logic should be in the smmu driver - > this should return some Exxx to indicate the queue is filled. Hmm, the driver only screams... static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev) { [...] /* * Not much we can do on overflow, so scream and pretend we're * trying harder. */ if (queue_sync_prod_in(q) == -EOVERFLOW) dev_err(smmu->dev, "EVTQ overflow detected -- events lost\n"); > I supposed we will need a way to indicate lost events to userspace on > top of this? Perhaps another u32 flag in the arm_smmuv3_vevent struct to report an overflow. That said, what userspace/VMM will need to do with it? > Presumably userspace should specify the max queue size. Yes. Similarly, vCMDQ has a vcmdq_log2size in the driver structure for that. For veventq, this piece is core managed, so we will need a veventq_size or so in the common iommufd_veventq_alloc structure. Thanks! Nicolin