diff options
| author | Kan Liang <kan.liang@linux.intel.com> | 2023-03-29 21:47:21 +0800 |
|---|---|---|
| committer | Joerg Roedel <jroedel@suse.de> | 2023-03-31 10:06:16 +0200 |
| commit | 16812c96550c30a8d5743167ef4e462d6fbe7472 (patch) | |
| tree | 9549951ca600c4ca6a58b0710e70ce4fe732f6b0 /include | |
| parent | bfd3c6b9fa4a1dc78139dd1621d5bea321ffa69d (diff) | |
iommu/vt-d: Fix an IOMMU perfmon warning when CPU hotplug
A warning can be triggered when hotplug CPU 0.
$ echo 0 > /sys/devices/system/cpu/cpu0/online
------------[ cut here ]------------
Voluntary context switch within RCU read-side critical section!
WARNING: CPU: 0 PID: 19 at kernel/rcu/tree_plugin.h:318
rcu_note_context_switch+0x4f4/0x580
RIP: 0010:rcu_note_context_switch+0x4f4/0x580
Call Trace:
<TASK>
? perf_event_update_userpage+0x104/0x150
__schedule+0x8d/0x960
? perf_event_set_state.part.82+0x11/0x50
schedule+0x44/0xb0
schedule_timeout+0x226/0x310
? __perf_event_disable+0x64/0x1a0
? _raw_spin_unlock+0x14/0x30
wait_for_completion+0x94/0x130
__wait_rcu_gp+0x108/0x130
synchronize_rcu+0x67/0x70
? invoke_rcu_core+0xb0/0xb0
? __bpf_trace_rcu_stall_warning+0x10/0x10
perf_pmu_migrate_context+0x121/0x370
iommu_pmu_cpu_offline+0x6a/0xa0
? iommu_pmu_del+0x1e0/0x1e0
cpuhp_invoke_callback+0x129/0x510
cpuhp_thread_fun+0x94/0x150
smpboot_thread_fn+0x183/0x220
? sort_range+0x20/0x20
kthread+0xe6/0x110
? kthread_complete_and_exit+0x20/0x20
ret_from_fork+0x1f/0x30
</TASK>
---[ 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")
Reported-by: Ammy Yi <ammy.yi@intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Link: https://lore.kernel.org/r/20230328182028.1366416-1-kan.liang@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20230329134721.469447-4-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/cpuhotplug.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index c6fab004104a..5b2f8147d1ae 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -218,7 +218,6 @@ enum cpuhp_state { CPUHP_AP_PERF_X86_CQM_ONLINE, CPUHP_AP_PERF_X86_CSTATE_ONLINE, CPUHP_AP_PERF_X86_IDXD_ONLINE, - CPUHP_AP_PERF_X86_IOMMU_PERF_ONLINE, CPUHP_AP_PERF_S390_CF_ONLINE, CPUHP_AP_PERF_S390_SF_ONLINE, CPUHP_AP_PERF_ARM_CCI_ONLINE, |