[tip: perf/core] perf/x86/intel/uncore: Introduce PMU flags and broken state
From: tip-bot2 for Zide Chen
Date: Tue Jun 30 2026 - 05:16:48 EST
The following commit has been merged into the perf/core branch of tip:
Commit-ID: 30c0a1095652275768a5de67188ff888d1f5d190
Gitweb: https://git.kernel.org/tip/30c0a1095652275768a5de67188ff888d1f5d190
Author: Zide Chen <zide.chen@xxxxxxxxx>
AuthorDate: Thu, 11 Jun 2026 09:00:31 -07:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 30 Jun 2026 10:57:04 +02:00
perf/x86/intel/uncore: Introduce PMU flags and broken state
Replace the boolean 'registered' field in intel_uncore_pmu with an
unsigned long 'flags' field, and add a PMU_BROKEN flag to track box
setup failures. The broken flag is sticky, meaning it is cleared only
by a module reload or system reboot.
Broken PMUs are skipped in the CPU hotplug and box allocation paths.
When any box fails to initialize, the PMU is marked broken. Broken
PMUs reject new event assignments and skip future box setup attempts.
If the PMU was already registered, it remains so to avoid disrupting
in-flight events on other boxes.
Signed-off-by: Zide Chen <zide.chen@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
Link: https://patch.msgid.link/20260611160033.66760-7-zide.chen@xxxxxxxxx
---
arch/x86/events/intel/uncore.c | 44 +++++++++++++++++++++--------
arch/x86/events/intel/uncore.h | 13 ++++++++-
arch/x86/events/intel/uncore_snb.c | 2 +-
3 files changed, 46 insertions(+), 13 deletions(-)
diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
index 06ef89f..feb8c3b 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -757,7 +757,7 @@ static int uncore_pmu_event_init(struct perf_event *event)
pmu = uncore_event_to_pmu(event);
/* no device found for this pmu */
- if (!pmu->registered)
+ if (!uncore_pmu_available(pmu))
return -ENOENT;
/* Sampling not supported yet */
@@ -953,16 +953,18 @@ static int uncore_pmu_register(struct intel_uncore_pmu *pmu)
ret = perf_pmu_register(&pmu->pmu, pmu->name, -1);
if (!ret)
- pmu->registered = true;
+ uncore_pmu_set_registered(pmu);
return ret;
}
static void uncore_pmu_unregister(struct intel_uncore_pmu *pmu)
{
- if (!pmu->registered)
+ if (!uncore_pmu_registered(pmu))
return;
perf_pmu_unregister(&pmu->pmu);
- pmu->registered = false;
+
+ /* Keep PMU_BROKEN_BIT sticky. */
+ uncore_pmu_clear_registered(pmu);
}
static void uncore_free_boxes(struct intel_uncore_pmu *pmu)
@@ -1153,7 +1155,12 @@ static int uncore_box_setup(struct intel_uncore_pmu *pmu,
{
int ret;
- uncore_box_init(box);
+ if (uncore_pmu_broken(pmu))
+ return -ENODEV;
+
+ ret = uncore_box_init(box);
+ if (ret)
+ goto err;
/* First active box registers the pmu. */
if (atomic_inc_return(&pmu->activeboxes) > 1)
@@ -1167,6 +1174,16 @@ static int uncore_box_setup(struct intel_uncore_pmu *pmu,
return 0;
err:
+ /*
+ * If any box fails, mark the per-package PMU as broken regardless of
+ * whether it was registered or not.
+ *
+ * Don't decrement refcnt to avoid other in-die CPUs from trying to set
+ * up the PMU box again.
+ *
+ * Don't kfree box; MSR and MMIO boxes are freed at module exit only.
+ */
+ uncore_pmu_set_broken(pmu);
uncore_box_exit(box);
return ret;
}
@@ -1190,8 +1207,10 @@ static int uncore_pci_pmu_register(struct pci_dev *pdev,
return -EINVAL;
box = uncore_alloc_box(type, NUMA_NO_NODE);
- if (!box)
+ if (!box) {
+ uncore_pmu_set_broken(pmu);
return -ENOMEM;
+ }
atomic_inc(&box->refcnt);
box->dieid = die;
@@ -1507,7 +1526,8 @@ static void uncore_change_type_ctx(struct intel_uncore_type *type, int old_cpu,
if (old_cpu < 0) {
WARN_ON_ONCE(box->cpu != -1);
- if (uncore_die_has_box(type, die, pmu->pmu_idx)) {
+ if (uncore_die_has_box(type, die, pmu->pmu_idx) &&
+ !uncore_pmu_broken(pmu)) {
box->cpu = new_cpu;
cpumask_set_cpu(new_cpu, &pmu->cpu_mask);
}
@@ -1515,12 +1535,14 @@ static void uncore_change_type_ctx(struct intel_uncore_type *type, int old_cpu,
}
WARN_ON_ONCE(box->cpu != -1 && box->cpu != old_cpu);
- box->cpu = -1;
cpumask_clear_cpu(old_cpu, &pmu->cpu_mask);
- if (new_cpu < 0)
+ if (new_cpu < 0) {
+ box->cpu = -1;
continue;
+ }
- if (!uncore_die_has_box(type, die, pmu->pmu_idx))
+ /* An inactive box doesn't need migration. */
+ if (box->cpu == -1)
continue;
uncore_pmu_cancel_hrtimer(box);
perf_pmu_migrate_context(&pmu->pmu, old_cpu, new_cpu);
@@ -1596,7 +1618,7 @@ static int allocate_boxes(struct intel_uncore_type **types,
type = *types;
pmu = type->pmus;
for (i = 0; i < type->num_boxes; i++, pmu++) {
- if (pmu->boxes[die])
+ if (pmu->boxes[die] || uncore_pmu_broken(pmu))
continue;
box = uncore_alloc_box(type, cpu_to_node(cpu));
if (!box)
diff --git a/arch/x86/events/intel/uncore.h b/arch/x86/events/intel/uncore.h
index d732b87..0adb477 100644
--- a/arch/x86/events/intel/uncore.h
+++ b/arch/x86/events/intel/uncore.h
@@ -146,13 +146,24 @@ struct intel_uncore_pmu {
struct pmu pmu;
char name[UNCORE_PMU_NAME_LEN];
int pmu_idx;
- bool registered;
+ unsigned long flags;
atomic_t activeboxes;
cpumask_t cpu_mask;
struct intel_uncore_type *type;
struct intel_uncore_box **boxes;
};
+#define PMU_REGISTERED_BIT 0
+#define PMU_BROKEN_BIT 1
+
+#define uncore_pmu_registered(pmu) test_bit(PMU_REGISTERED_BIT, &(pmu)->flags)
+#define uncore_pmu_broken(pmu) test_bit(PMU_BROKEN_BIT, &(pmu)->flags)
+#define uncore_pmu_available(pmu) (uncore_pmu_registered(pmu) && \
+ !uncore_pmu_broken(pmu))
+#define uncore_pmu_set_registered(pmu) set_bit(PMU_REGISTERED_BIT, &(pmu)->flags)
+#define uncore_pmu_set_broken(pmu) set_bit(PMU_BROKEN_BIT, &(pmu)->flags)
+#define uncore_pmu_clear_registered(pmu) clear_bit(PMU_REGISTERED_BIT, &(pmu)->flags)
+
struct intel_uncore_extra_reg {
raw_spinlock_t lock;
u64 config, config1, config2;
diff --git a/arch/x86/events/intel/uncore_snb.c b/arch/x86/events/intel/uncore_snb.c
index c534792..055131c 100644
--- a/arch/x86/events/intel/uncore_snb.c
+++ b/arch/x86/events/intel/uncore_snb.c
@@ -940,7 +940,7 @@ static int snb_uncore_imc_event_init(struct perf_event *event)
pmu = uncore_event_to_pmu(event);
/* no device found for this pmu */
- if (!pmu->registered)
+ if (!uncore_pmu_available(pmu))
return -ENOENT;
/* Sampling not supported yet */