[Patch v2 0/7] perf/x86: Miscellaneous PMU bug fixes and optimizations

[Patch v2 0/7] perf/x86: Miscellaneous PMU bug fixes and optimizations

[Dapeng Mi]

Changes since v1:
- Patch 3/7: Ensure cpuc->pmu is not the static pmu before calling
  hybrid_pmu(cpuc->pmu) in intel_pmu_cpu_dead() (Sashiko).

This series fixes recently found x86 core PMU bugs. Most of bugs are
found by Sashiko in reviewing the "Support SIMD/eGPRs/SSP registers 
sampling for perf" patch-set, e.g.,
https://lore.kernel.org/all/20260706022123.480411F000E9@smtp.kernel.org/
https://lore.kernel.org/all/20260706021852.DE2ED1F000E9@smtp.kernel.org/

The last patch 7/7 optimizes ACR handling in match_prev_assignment() and
mitigate the performance overhead.

Tests:
Below test cases are run on Diamonds and Novalake. No issues are found.
- Perf stat test
  $ perf test 119
- Perf record tests 
  $ perf test 155
- Perf record LBR tests
  $ perf test 156

History:
v1: https://lore.kernel.org/all/20260710065128.1799838-1-dapeng1.mi@linux.intel.com/

Dapeng Mi (7):
  perf/x86: Unregister PMI handler on PMU init failure
  perf/x86: Free hybrid state on PMU init failure
  perf/x86: Guard intel_pmu_cpu_dead() against invalid hybrid PMU casts
  perf/x86/intel: Unwind cpuc state if PEBS buffer setup fails
  perf/x86: Remove stale fixed counter helper and fix hybrid PMU access
  perf/x86/intel: Fix intel_cap handling on hybrid PMUs
  perf/x86: Optimize ACR handling in match_prev_assignment()

 arch/x86/events/core.c       | 45 +++++++++++++++++++-------
 arch/x86/events/intel/core.c | 61 ++++++++++++++++++++++++++----------
 arch/x86/events/perf_event.h | 12 ++-----
 3 files changed, 81 insertions(+), 37 deletions(-)


base-commit: edda9051e267b7390c7ce24b1b71434414ad156e
-- 
2.34.1

[Patch v2 1/7] perf/x86: Unregister PMI handler on PMU init failure

[Dapeng Mi]

Fix an NMI handler leak in init_hw_perf_events(). When PMU
initialization fails after register_nmi_handler(), the error path
exits without calling unregister_nmi_handler(), leaving a stale
NMI_LOCAL "PMI" handler registered. Add the missing call before
clearing x86_pmu state.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
 arch/x86/events/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index af0b67ffb43d..872d07a5fa80 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2219,7 +2219,7 @@ static int __init init_hw_perf_events(void)
 	err = cpuhp_setup_state(CPUHP_PERF_X86_PREPARE, "perf/x86:prepare",
 				x86_pmu_prepare_cpu, x86_pmu_dead_cpu);
 	if (err)
-		return err;
+		goto pmi_unregister;
 
 	err = cpuhp_setup_state(CPUHP_AP_PERF_X86_STARTING,
 				"perf/x86:starting", x86_pmu_starting_cpu,
@@ -2273,6 +2273,8 @@ static int __init init_hw_perf_events(void)
 	cpuhp_remove_state(CPUHP_AP_PERF_X86_STARTING);
 out:
 	cpuhp_remove_state(CPUHP_PERF_X86_PREPARE);
+pmi_unregister:
+	unregister_nmi_handler(NMI_LOCAL, "PMI");
 out_bad_pmu:
 	memset(&x86_pmu, 0, sizeof(x86_pmu));
 	return err;
-- 
2.34.1

[Patch v2 2/7] perf/x86: Free hybrid state on PMU init failure

[Dapeng Mi]

If PMU initialization fails, for example in check_hw_exists(), hybrid
state can be left partially initialized: x86_pmu.hybrid_pmu is not freed
and perf_is_hybrid remains set. This can leak memory and leave stale
hybrid state reachable after a failed init path.

Add x86_pmu_free_hybrid() and use it on PMU init failure paths so all
hybrid-related state is consistently reset.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
 arch/x86/events/core.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 872d07a5fa80..6c63b27e11e6 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2130,6 +2130,17 @@ void x86_pmu_show_pmu_cap(struct pmu *pmu)
 	pr_info("... global_ctrl mask:          %016llx\n", hybrid(pmu, intel_ctrl));
 }
 
+static void x86_pmu_free_hybrid(void)
+{
+	if (!x86_pmu.hybrid_pmu)
+		return;
+
+	static_branch_disable(&perf_is_hybrid);
+	kfree(x86_pmu.hybrid_pmu);
+	x86_pmu.hybrid_pmu = NULL;
+	x86_pmu.num_hybrid_pmus = 0;
+}
+
 static int __init init_hw_perf_events(void)
 {
 	struct x86_pmu_quirk *quirk;
@@ -2258,9 +2269,6 @@ static int __init init_hw_perf_events(void)
 			for (j = 0; j < i; j++)
 				perf_pmu_unregister(&x86_pmu.hybrid_pmu[j].pmu);
 			pr_warn("Failed to register hybrid PMUs\n");
-			kfree(x86_pmu.hybrid_pmu);
-			x86_pmu.hybrid_pmu = NULL;
-			x86_pmu.num_hybrid_pmus = 0;
 			goto out2;
 		}
 	}
@@ -2276,6 +2284,7 @@ static int __init init_hw_perf_events(void)
 pmi_unregister:
 	unregister_nmi_handler(NMI_LOCAL, "PMI");
 out_bad_pmu:
+	x86_pmu_free_hybrid();
 	memset(&x86_pmu, 0, sizeof(x86_pmu));
 	return err;
 }
-- 
2.34.1

[Patch v2 3/7] perf/x86: Guard intel_pmu_cpu_dead() against invalid hybrid PMU casts

[Dapeng Mi]

In failure paths, cpuc->pmu can still point to the global static pmu
instead of an embedded x86_hybrid_pmu::pmu. Calling hybrid_pmu() on
that pointer causes an invalid container conversion and may lead to
out-of-bounds access.

This can happen in at least two cases:
- init_hybrid_pmu() fails check_hw_exists() and leaves cpuc->pmu as-is.
- CPU hotplug fails between CPUHP_PERF_X86_PREPARE and
CPUHP_AP_PERF_X86_STARTING, and rollback invokes intel_pmu_cpu_dead().

Fix both paths by:
- Clear cpuc->pmu to NULL when check_hw_exists() fails.
- Validat that cpuc->pmu is not the global static pmu before calling
  hybrid_pmu() in intel_pmu_cpu_dead().

A new helper x86_get_static_pmu() is added to get the global static pmu.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
 arch/x86/events/core.c       | 5 +++++
 arch/x86/events/intel/core.c | 7 +++++--
 arch/x86/events/perf_event.h | 1 +
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 6c63b27e11e6..a02f303a9151 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -790,6 +790,11 @@ int is_x86_event(struct perf_event *event)
 	return false;
 }
 
+inline struct pmu *x86_get_static_pmu(void)
+{
+	return &pmu;
+}
+
 struct pmu *x86_get_pmu(unsigned int cpu)
 {
 	struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index b39c6ce0efb5..a991fc4f1575 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -6329,8 +6329,10 @@ static bool init_hybrid_pmu(int cpu)
 
 	intel_pmu_check_hybrid_pmus(pmu);
 
-	if (!check_hw_exists(&pmu->pmu, pmu->cntr_mask, pmu->fixed_cntr_mask))
+	if (!check_hw_exists(&pmu->pmu, pmu->cntr_mask, pmu->fixed_cntr_mask)) {
+		cpuc->pmu = NULL;
 		return false;
+	}
 
 	pr_info("%s PMU driver: ", pmu->name);
 
@@ -6475,11 +6477,12 @@ void intel_cpuc_finish(struct cpu_hw_events *cpuc)
 static void intel_pmu_cpu_dead(int cpu)
 {
 	struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
+	struct pmu *pmu = x86_get_static_pmu();
 
 	release_arch_pebs_buf_on_cpu(cpu);
 	intel_cpuc_finish(cpuc);
 
-	if (is_hybrid() && cpuc->pmu)
+	if (is_hybrid() && cpuc->pmu && cpuc->pmu != pmu)
 		cpumask_clear_cpu(cpu, &hybrid_pmu(cpuc->pmu)->supported_cpus);
 }
 
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index a8afea8d38f0..01ae287cde16 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -1161,6 +1161,7 @@ static struct perf_pmu_format_hybrid_attr format_attr_hybrid_##_name = {\
 	.pmu_type	= _pmu,						\
 }
 
+struct pmu *x86_get_static_pmu(void);
 struct pmu *x86_get_pmu(unsigned int cpu);
 extern struct x86_pmu x86_pmu __read_mostly;
 
-- 
2.34.1

[Patch v2 4/7] perf/x86/intel: Unwind cpuc state if PEBS buffer setup fails

[Dapeng Mi]

intel_pmu_cpu_prepare() allocates per-CPU perf state first and then sets
up the arch PEBS buffer. If alloc_arch_pebs_buf_on_cpu() fails,
the previously allocated cpuc resources are left behind.

Make the failure path call intel_cpuc_finish(cpuc) to release the per-CPU
state allocated by intel_cpuc_prepare().

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
 arch/x86/events/intel/core.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index a991fc4f1575..b47d2f00ac13 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -5924,13 +5924,20 @@ int intel_cpuc_prepare(struct cpu_hw_events *cpuc, int cpu)
 
 static int intel_pmu_cpu_prepare(int cpu)
 {
+	struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
 	int ret;
 
-	ret = intel_cpuc_prepare(&per_cpu(cpu_hw_events, cpu), cpu);
+	ret = intel_cpuc_prepare(cpuc, cpu);
 	if (ret)
 		return ret;
 
-	return alloc_arch_pebs_buf_on_cpu(cpu);
+	ret = alloc_arch_pebs_buf_on_cpu(cpu);
+	if (ret) {
+		intel_cpuc_finish(cpuc);
+		return ret;
+	}
+
+	return 0;
 }
 
 static void flip_smm_bit(void *data)
-- 
2.34.1

[Patch v2 5/7] perf/x86: Remove stale fixed counter helper and fix hybrid PMU access

[Dapeng Mi]

On hybrid systems, init_hw_perf_events() can call check_hw_exists() with
the global PMU pointer after perf_is_hybrid is set. In that case,
fixed_counter_disabled() uses hybrid() on a non-hybrid PMU object, so the
intel_ctrl access is taken from the wrong layout and can read out of
bounds.

fixed_counter_disabled() was added in commit 32451614da2a
("perf/x86/intel: Support CPUID 10.ECX to disable fixed counters"), when
fixed counters were tracked via num_fixed_counters. Today fixed counters
are represented by fixed_cntr_mask, so this helper is obsolete.

Remove fixed_counter_disabled() and its callers, and rely directly on the
fixed-counter bitmask. With the helper gone, check_hw_exists() no longer
needs a PMU argument, so drop that parameter as well. This removes the
invalid hybrid access and closes the out-of-bounds read risk.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
 arch/x86/events/core.c       | 8 ++------
 arch/x86/events/intel/core.c | 4 +---
 arch/x86/events/perf_event.h | 9 +--------
 3 files changed, 4 insertions(+), 17 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index a02f303a9151..143a6e735d9e 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -265,7 +265,7 @@ static void release_pmc_hardware(void) {}
 
 #endif
 
-bool check_hw_exists(struct pmu *pmu, unsigned long *cntr_mask,
+bool check_hw_exists(unsigned long *cntr_mask,
 		     unsigned long *fixed_cntr_mask)
 {
 	u64 val, val_fail = -1, val_new= ~0;
@@ -297,8 +297,6 @@ bool check_hw_exists(struct pmu *pmu, unsigned long *cntr_mask,
 		if (ret)
 			goto msr_fail;
 		for_each_set_bit(i, fixed_cntr_mask, X86_PMC_IDX_MAX) {
-			if (fixed_counter_disabled(i, pmu))
-				continue;
 			if (val & (0x03ULL << i*4)) {
 				bios_fail = 1;
 				val_fail = val;
@@ -1618,8 +1616,6 @@ void perf_event_print_debug(void)
 			cpu, idx, prev_left);
 	}
 	for_each_set_bit(idx, fixed_cntr_mask, X86_PMC_IDX_MAX) {
-		if (fixed_counter_disabled(idx, cpuc->pmu))
-			continue;
 		rdmsrq(x86_pmu_fixed_ctr_addr(idx), pmc_count);
 
 		pr_info("CPU#%d: fixed-PMC%d count: %016llx\n",
@@ -2180,7 +2176,7 @@ static int __init init_hw_perf_events(void)
 	pmu_check_apic();
 
 	/* sanity check that the hardware exists or is emulated */
-	if (!check_hw_exists(&pmu, x86_pmu.cntr_mask, x86_pmu.fixed_cntr_mask))
+	if (!check_hw_exists(x86_pmu.cntr_mask, x86_pmu.fixed_cntr_mask))
 		goto out_bad_pmu;
 
 	pr_cont("%s PMU driver.\n", x86_pmu.name);
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index b47d2f00ac13..c418176065f6 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3713,8 +3713,6 @@ static void intel_pmu_reset(void)
 		wrmsrq_safe(x86_pmu_event_addr(idx),  0ull);
 	}
 	for_each_set_bit(idx, fixed_cntr_mask, INTEL_PMC_MAX_FIXED) {
-		if (fixed_counter_disabled(idx, cpuc->pmu))
-			continue;
 		wrmsrq_safe(x86_pmu_fixed_ctr_addr(idx), 0ull);
 	}
 
@@ -6336,7 +6334,7 @@ static bool init_hybrid_pmu(int cpu)
 
 	intel_pmu_check_hybrid_pmus(pmu);
 
-	if (!check_hw_exists(&pmu->pmu, pmu->cntr_mask, pmu->fixed_cntr_mask)) {
+	if (!check_hw_exists(pmu->cntr_mask, pmu->fixed_cntr_mask)) {
 		cpuc->pmu = NULL;
 		return false;
 	}
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 01ae287cde16..cc9cfaae4f01 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -1243,7 +1243,7 @@ static inline int x86_pmu_rdpmc_index(int index)
 	return x86_pmu.rdpmc_index ? x86_pmu.rdpmc_index(index) : index;
 }
 
-bool check_hw_exists(struct pmu *pmu, unsigned long *cntr_mask,
+bool check_hw_exists(unsigned long *cntr_mask,
 		     unsigned long *fixed_cntr_mask);
 
 int x86_add_exclusive(unsigned int what);
@@ -1456,13 +1456,6 @@ ssize_t events_hybrid_sysfs_show(struct device *dev,
 				 struct device_attribute *attr,
 				 char *page);
 
-static inline bool fixed_counter_disabled(int i, struct pmu *pmu)
-{
-	u64 intel_ctrl = hybrid(pmu, intel_ctrl);
-
-	return !(intel_ctrl >> (i + INTEL_PMC_IDX_FIXED));
-}
-
 #ifdef CONFIG_CPU_SUP_AMD
 
 int amd_pmu_init(void);
-- 
2.34.1

[Patch v2 6/7] perf/x86/intel: Fix intel_cap handling on hybrid PMUs

[Dapeng Mi]

intel_cap (IA32_PERF_CAPABILITIES) updates are currently tied to
X86_FEATURE_ARCH_PERFMON_EXT, but these are independent feature paths.
As a result, hybrid PMU capability state can be updated under the wrong
condition.

Also, intel_pmu_broken_perf_cap() is too narrow. Per RPL018, the missing
PERF_METRICS_AVAILABLE bit affects both Raptor Lake and Meteor Lake
parts, not only the currently covered subset.

Move intel_cap updates out of the ARCH_PERFMON_EXT-gated path, extend
intel_pmu_broken_perf_cap() coverage to both RPL and MTL families, and
introduce intel_update_pmu_caps() to centralize PMU capability updates.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
 arch/x86/events/intel/core.c | 41 ++++++++++++++++++++++++++----------
 1 file changed, 30 insertions(+), 11 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index c418176065f6..bec92163a09f 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -6147,8 +6147,15 @@ static void intel_pmu_check_extra_regs(struct extra_reg *extra_regs);
 
 static inline bool intel_pmu_broken_perf_cap(void)
 {
-	/* The Perf Metric (Bit 15) is always cleared */
-	if (boot_cpu_data.x86_vfm == INTEL_METEORLAKE ||
+	/*
+	 * The Perf Metric (Bit 15) is always cleared on P-core of
+	 * PRL and MTL. Details can be found in RPL018 Errata Details.
+	 * https://edc.intel.com/content/www/us/en/design/products/platforms/details/raptor-lake-s/13th-generation-core-processor-specification-update/errata-details/
+	 */
+	if (boot_cpu_data.x86_vfm == INTEL_RAPTORLAKE ||
+	    boot_cpu_data.x86_vfm == INTEL_RAPTORLAKE_P ||
+	    boot_cpu_data.x86_vfm == INTEL_RAPTORLAKE_S ||
+	    boot_cpu_data.x86_vfm == INTEL_METEORLAKE ||
 	    boot_cpu_data.x86_vfm == INTEL_METEORLAKE_L)
 		return true;
 
@@ -6183,7 +6190,7 @@ static inline void __intel_update_large_pebs_flags(struct pmu *pmu)
 
 #define counter_mask(_gp, _fixed) ((_gp) | ((u64)(_fixed) << INTEL_PMC_IDX_FIXED))
 
-static void update_pmu_cap(struct pmu *pmu)
+static void update_pmu_cap_from_perfmonext(struct pmu *pmu)
 {
 	unsigned int eax, ebx, ecx, edx;
 	union cpuid35_eax eax_0;
@@ -6241,10 +6248,24 @@ static void update_pmu_cap(struct pmu *pmu)
 		WARN_ON(x86_pmu.arch_pebs == 1);
 		x86_pmu.arch_pebs = 0;
 	}
+}
+
+static void intel_update_pmu_caps(struct pmu *pmu)
+{
+	if (this_cpu_has(X86_FEATURE_ARCH_PERFMON_EXT))
+		update_pmu_cap_from_perfmonext(pmu);
 
-	if (!intel_pmu_broken_perf_cap()) {
-		/* Perf Metric (Bit 15) and PEBS via PT (Bit 16) are hybrid enumeration */
-		rdmsrq(MSR_IA32_PERF_CAPABILITIES, hybrid(pmu, intel_cap).capabilities);
+	if (is_hybrid() && this_cpu_has(X86_FEATURE_PDCM)) {
+		rdmsrq(MSR_IA32_PERF_CAPABILITIES,
+		       hybrid(pmu, intel_cap).capabilities);
+
+		/*
+		 * Restore perf_metrics on platforms with broken
+		 * perf_capablities.
+		 */
+		if (intel_pmu_broken_perf_cap() &&
+		    hybrid_pmu(pmu)->pmu_type == hybrid_big)
+			hybrid(pmu, intel_cap).perf_metrics = 1;
 	}
 }
 
@@ -6329,9 +6350,7 @@ static bool init_hybrid_pmu(int cpu)
 	if (!cpumask_empty(&pmu->supported_cpus))
 		goto end;
 
-	if (this_cpu_has(X86_FEATURE_ARCH_PERFMON_EXT))
-		update_pmu_cap(&pmu->pmu);
-
+	intel_update_pmu_caps(&pmu->pmu);
 	intel_pmu_check_hybrid_pmus(pmu);
 
 	if (!check_hw_exists(pmu->cntr_mask, pmu->fixed_cntr_mask)) {
@@ -8828,8 +8847,8 @@ __init int intel_pmu_init(void)
 	 * from the leaf 0xa. The core specific update will be done later
 	 * when a new type is online.
 	 */
-	if (!is_hybrid() && boot_cpu_has(X86_FEATURE_ARCH_PERFMON_EXT))
-		update_pmu_cap(NULL);
+	if (!is_hybrid())
+		intel_update_pmu_caps(NULL);
 
 	if (x86_pmu.arch_pebs) {
 		static_call_update(intel_pmu_disable_event_ext,
-- 
2.34.1

[Patch v2 7/7] perf/x86: Optimize ACR handling in match_prev_assignment()

[Dapeng Mi]

match_prev_assignment() currently forces a mismatch for ACR events, so
ACR counter indices are reprogrammed on every scheduling pass. That
causes avoidable overhead because disable and enable paths must touch
multiple MSRs.

The previous ACR assignment is already cached in acr_cfg_b[]. Use that
state to compare the newly computed ACR counter indices in hwc->config1
against the cached value in acr_cfg_b[hwc->idx]. If they match, skip
unnecessary disable and enable work.

Also tighten is_acr_self_reload_event() so it first verifies the event
is an ACR event before testing for the self-reload case.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
 arch/x86/events/core.c       | 13 ++++++++++++-
 arch/x86/events/perf_event.h |  2 +-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 143a6e735d9e..8b3ea0adb965 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1297,6 +1297,17 @@ int x86_perf_rdpmc_index(struct perf_event *event)
 	return event->hw.event_base_rdpmc;
 }
 
+static inline bool acr_match_prev_indices(struct perf_event *event,
+					  struct cpu_hw_events *cpuc)
+{
+	struct hw_perf_event *hwc = &event->hw;
+
+	if (!is_acr_event_group(event))
+		return true;
+	/* ACR counter indices don't change. */
+	return hwc->config1 == cpuc->acr_cfg_b[hwc->idx];
+}
+
 static inline int match_prev_assignment(struct perf_event *event,
 					struct cpu_hw_events *cpuc,
 					int i)
@@ -1306,7 +1317,7 @@ static inline int match_prev_assignment(struct perf_event *event,
 	return hwc->idx == cpuc->assign[i] &&
 	       hwc->last_cpu == smp_processor_id() &&
 	       hwc->last_tag == cpuc->tags[i] &&
-	       !is_acr_event_group(event);
+	       acr_match_prev_indices(event, cpuc);
 }
 
 static void x86_pmu_start(struct perf_event *event, int flags);
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index cc9cfaae4f01..fa381110f7a7 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -141,7 +141,7 @@ static inline bool is_acr_self_reload_event(struct perf_event *event)
 {
 	struct hw_perf_event *hwc = &event->hw;
 
-	if (hwc->idx < 0)
+	if (hwc->idx < 0 || !is_acr_event_group(event))
 		return false;
 
 	return test_bit(hwc->idx, (unsigned long *)&hwc->config1);
-- 
2.34.1

Re: [Patch v2 3/7] perf/x86: Guard intel_pmu_cpu_dead() against invalid hybrid PMU casts

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:

Pre-existing issues:
- [High] Race condition in NMI handler causing out-of-bounds access during hybrid CPU bring-up.
- [High] Unhandled #GP exceptions (kernel panic) in NMI and hotplug paths if hybrid PMU initialization fails.
--

--- Patch [3]: [Patch v2 3/7] perf/x86: Guard intel_pmu_cpu_dead() against invalid hybrid PMU casts ---
commit 419f89d32dfc7abe942483376114f8e4845bc1a8
Author: Dapeng Mi <dapeng1.mi@linux.intel.com>

perf/x86: Guard intel_pmu_cpu_dead() against invalid hybrid PMU casts

In failure paths, cpuc->pmu can point to the global static pmu instead of
an embedded x86_hybrid_pmu::pmu. This commit clears cpuc->pmu to NULL when
check_hw_exists() fails and validates cpuc->pmu before hybrid container
conversion during CPU rollback paths.

> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index b39c6ce0efb5c..a991fc4f1575f 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
[ ... ]
> @@ -6329,8 +6329,10 @@ static bool init_hybrid_pmu(int cpu)
>  
>  	intel_pmu_check_hybrid_pmus(pmu);
>  
> -	if (!check_hw_exists(&pmu->pmu, pmu->cntr_mask, pmu->fixed_cntr_mask))
> +	if (!check_hw_exists(&pmu->pmu, pmu->cntr_mask, pmu->fixed_cntr_mask)) {
> +		cpuc->pmu = NULL;
>  		return false;
> +	}

[Severity: High]
This is a pre-existing issue, but is it possible for an NMI to fire before
this initialization completes during hybrid CPU bring-up?

If a secondary CPU unmasks NMIs early and an NMI fires before the
CPUHP_AP_PERF_X86_STARTING callback executes init_hybrid_pmu(),
perf_event_nmi_handler() will run.

If active_events is greater than zero globally, intel_pmu_handle_irq()
executes:

arch/x86/events/intel/core.c:intel_pmu_handle_irq() {
    ...
    bool late_ack = hybrid_bit(cpuc->pmu, late_ack);
    ...
}

Since cpuc->pmu is statically initialized to the global &pmu at this stage,
could this cause hybrid_pmu() to perform an invalid container_of cast and
lead to an out-of-bounds access?

[Severity: High]
This is a pre-existing issue, but if check_hw_exists() fails and we return
false here, leaving the CPU online without a functioning PMU, could this lead
to unhandled #GP exceptions?

If an NMI fires while active_events is greater than zero globally,
intel_pmu_handle_irq() unconditionally reads PMU MSRs:

arch/x86/events/intel/core.c:intel_pmu_handle_irq() {
    ...
    status = intel_pmu_get_status();
    ...
}

Since check_hw_exists() failed, the MSRs are likely inaccessible. Would
executing rdmsrl() trigger a #GP exception and a kernel panic?

Similarly, during CPU teardown, does intel_pmu_cpu_dying() blindly write to
MSRs without checking if the PMU was successfully initialized?

arch/x86/events/intel/ds.c:fini_arch_pebs_on_cpu() {
    ...
    wrmsrq_on_cpu(cpu, MSR_IA32_PEBS_BASE, 0);
    ...
}

Could this wrmsrq_on_cpu() without fault protection also cause a #GP panic if
PMU initialization had failed?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260713082734.3162099-1-dapeng1.mi@linux.intel.com?part=3