diff options
author | Kan Liang <kan.liang@linux.intel.com> | 2023-03-29 15:47:21 +0200 |
---|---|---|
committer | Joerg Roedel <jroedel@suse.de> | 2023-03-31 10:06:16 +0200 |
commit | 16812c96550c30a8d5743167ef4e462d6fbe7472 (patch) | |
tree | 9549951ca600c4ca6a58b0710e70ce4fe732f6b0 | |
parent | iommu/vt-d: Allow zero SAGAW if second-stage not supported (diff) | |
download | linux-16812c96550c30a8d5743167ef4e462d6fbe7472.tar.xz linux-16812c96550c30a8d5743167ef4e462d6fbe7472.zip |
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>
-rw-r--r-- | drivers/iommu/intel/iommu.h | 2 | ||||
-rw-r--r-- | drivers/iommu/intel/perfmon.c | 68 | ||||
-rw-r--r-- | include/linux/cpuhotplug.h | 1 |
3 files changed, 46 insertions, 25 deletions
diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h index d6df3b865812..694ab9b7d3e9 100644 --- a/drivers/iommu/intel/iommu.h +++ b/drivers/iommu/intel/iommu.h @@ -641,6 +641,8 @@ struct iommu_pmu { DECLARE_BITMAP(used_mask, IOMMU_PMU_IDX_MAX); struct perf_event *event_list[IOMMU_PMU_IDX_MAX]; unsigned char irq_name[16]; + struct hlist_node cpuhp_node; + int cpu; }; #define IOMMU_IRQ_ID_OFFSET_PRQ (DMAR_UNITS_SUPPORTED) diff --git a/drivers/iommu/intel/perfmon.c b/drivers/iommu/intel/perfmon.c index e17d9743a0d8..cf43e798eca4 100644 --- a/drivers/iommu/intel/perfmon.c +++ b/drivers/iommu/intel/perfmon.c @@ -773,19 +773,34 @@ static void iommu_pmu_unset_interrupt(struct intel_iommu *iommu) iommu->perf_irq = 0; } -static int iommu_pmu_cpu_online(unsigned int cpu) +static int iommu_pmu_cpu_online(unsigned int cpu, struct hlist_node *node) { + struct iommu_pmu *iommu_pmu = hlist_entry_safe(node, typeof(*iommu_pmu), cpuhp_node); + if (cpumask_empty(&iommu_pmu_cpu_mask)) cpumask_set_cpu(cpu, &iommu_pmu_cpu_mask); + if (cpumask_test_cpu(cpu, &iommu_pmu_cpu_mask)) + iommu_pmu->cpu = cpu; + return 0; } -static int iommu_pmu_cpu_offline(unsigned int cpu) +static int iommu_pmu_cpu_offline(unsigned int cpu, struct hlist_node *node) { - struct dmar_drhd_unit *drhd; - struct intel_iommu *iommu; - int target; + struct iommu_pmu *iommu_pmu = hlist_entry_safe(node, typeof(*iommu_pmu), cpuhp_node); + int target = cpumask_first(&iommu_pmu_cpu_mask); + + /* + * The iommu_pmu_cpu_mask has been updated when offline the CPU + * for the first iommu_pmu. Migrate the other iommu_pmu to the + * new target. + */ + if (target < nr_cpu_ids && target != iommu_pmu->cpu) { + perf_pmu_migrate_context(&iommu_pmu->pmu, cpu, target); + iommu_pmu->cpu = target; + return 0; + } if (!cpumask_test_and_clear_cpu(cpu, &iommu_pmu_cpu_mask)) return 0; @@ -795,45 +810,50 @@ static int iommu_pmu_cpu_offline(unsigned int cpu) if (target < nr_cpu_ids) cpumask_set_cpu(target, &iommu_pmu_cpu_mask); else - target = -1; + return 0; - rcu_read_lock(); - - for_each_iommu(iommu, drhd) { - if (!iommu->pmu) - continue; - perf_pmu_migrate_context(&iommu->pmu->pmu, cpu, target); - } - rcu_read_unlock(); + perf_pmu_migrate_context(&iommu_pmu->pmu, cpu, target); + iommu_pmu->cpu = target; return 0; } static int nr_iommu_pmu; +static enum cpuhp_state iommu_cpuhp_slot; static int iommu_pmu_cpuhp_setup(struct iommu_pmu *iommu_pmu) { int ret; - if (nr_iommu_pmu++) - return 0; + if (!nr_iommu_pmu) { + ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, + "driver/iommu/intel/perfmon:online", + iommu_pmu_cpu_online, + iommu_pmu_cpu_offline); + if (ret < 0) + return ret; + iommu_cpuhp_slot = ret; + } - ret = cpuhp_setup_state(CPUHP_AP_PERF_X86_IOMMU_PERF_ONLINE, - "driver/iommu/intel/perfmon:online", - iommu_pmu_cpu_online, - iommu_pmu_cpu_offline); - if (ret) - nr_iommu_pmu = 0; + ret = cpuhp_state_add_instance(iommu_cpuhp_slot, &iommu_pmu->cpuhp_node); + if (ret) { + if (!nr_iommu_pmu) + cpuhp_remove_multi_state(iommu_cpuhp_slot); + return ret; + } + nr_iommu_pmu++; - return ret; + return 0; } static void iommu_pmu_cpuhp_free(struct iommu_pmu *iommu_pmu) { + cpuhp_state_remove_instance(iommu_cpuhp_slot, &iommu_pmu->cpuhp_node); + if (--nr_iommu_pmu) return; - cpuhp_remove_state(CPUHP_AP_PERF_X86_IOMMU_PERF_ONLINE); + cpuhp_remove_multi_state(iommu_cpuhp_slot); } void iommu_pmu_register(struct intel_iommu *iommu) 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, |