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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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250110_183902_029980_0A5A4586 X-CRM114-Status: GOOD ( 25.55 ) 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, 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