Messages in this thread | | | Date | Wed, 29 Mar 2023 21:54:19 +0800 | Subject | Re: [PATCH V2] iommu/vt-d: Fix a IOMMU perfmon warning when CPU hotplug | From | Baolu Lu <> |
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On 2023/3/29 21:12, Liang, Kan wrote: > > On 2023-03-28 2:20 p.m.,kan.liang@linux.intel.com wrote: >> From: Kan Liang<kan.liang@linux.intel.com> >> >> A warning can be triggered when hotplug CPU 0. >> $ echo 0 > /sys/devices/system/cpu/cpu0/online >> >> [11958.737635] ------------[ cut here ]------------ >> [11958.742882] Voluntary context switch within RCU read-side critical >> section! >> [11958.742891] WARNING: CPU: 0 PID: 19 at kernel/rcu/tree_plugin.h:318 >> rcu_note_context_switch+0x4f4/0x580 >> [11958.860095] RIP: 0010:rcu_note_context_switch+0x4f4/0x580 >> [11958.960360] Call Trace: >> [11958.963161] <TASK> >> [11958.965565] ? perf_event_update_userpage+0x104/0x150 >> [11958.971293] __schedule+0x8d/0x960 >> [11958.975165] ? perf_event_set_state.part.82+0x11/0x50 >> [11958.980891] schedule+0x44/0xb0 >> [11958.984464] schedule_timeout+0x226/0x310 >> [11958.989017] ? __perf_event_disable+0x64/0x1a0 >> [11958.994054] ? _raw_spin_unlock+0x14/0x30 >> [11958.998605] wait_for_completion+0x94/0x130 >> [11959.003352] __wait_rcu_gp+0x108/0x130 >> [11959.007616] synchronize_rcu+0x67/0x70 >> [11959.011876] ? invoke_rcu_core+0xb0/0xb0 >> [11959.016333] ? __bpf_trace_rcu_stall_warning+0x10/0x10 >> [11959.022147] perf_pmu_migrate_context+0x121/0x370 >> [11959.027478] iommu_pmu_cpu_offline+0x6a/0xa0 >> [11959.032325] ? iommu_pmu_del+0x1e0/0x1e0 >> [11959.036782] cpuhp_invoke_callback+0x129/0x510 >> [11959.041825] cpuhp_thread_fun+0x94/0x150 >> [11959.046283] smpboot_thread_fn+0x183/0x220 >> [11959.050933] ? sort_range+0x20/0x20 >> [11959.054902] kthread+0xe6/0x110 >> [11959.058479] ? kthread_complete_and_exit+0x20/0x20 >> [11959.063911] ret_from_fork+0x1f/0x30 >> [11959.067982] </TASK> >> [11959.070489] ---[ end trace 0000000000000000 ]--- >> >> The synchronize_rcu() will be invoked in the perf_pmu_migrate_context(), >> when migrating a PMU to a new CPU. However, the current for_each_iommu() >> is within RCU read-side critical section. >> >> Two methods were considered to fix the issue. >> - Use the dmar_global_lock to replace the RCU read lock when going >> through the drhd list. But it triggers a lockdep warning. >> - Use the cpuhp_setup_state_multi() to set up a dedicated state for each >> IOMMU PMU. The lock can be avoided. >> >> The latter method is implemented in this patch. Since each IOMMU PMU has >> a dedicated state, add cpuhp_node and cpu in struct iommu_pmu to track >> the state. The state can be dynamically allocated now. Remove the >> CPUHP_AP_PERF_X86_IOMMU_PERF_ONLINE. >> >> Fixes: 46284c6ceb5e ("iommu/vt-d: Support cpumask for IOMMU perfmon") > Forgot to add a tag. If the patch looks good, please add the below tag > when you pull the patch. > > Reported-by: Ammy Yi<ammy.yi@intel.com>
Sure. Patch has been queued after my test.
https://lore.kernel.org/linux-iommu/20230329134721.469447-1-baolu.lu@linux.intel.com/
Best regards, baolu
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