[tip: perf/core] perf/x86/intel: Consolidate MSR_IA32_PERF_CFG_C tracking

[tip-bot2 for Dapeng Mi]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     5c3cdc74af25fc7f64a3ed260b4f6eb8313a3b75
Gitweb:        https://git.kernel.org/tip/5c3cdc74af25fc7f64a3ed260b4f6eb8313a3b75
Author:        Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
AuthorDate:    Thu, 30 Apr 2026 08:25:58 +08:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 05 May 2026 12:47:24 +02:00

perf/x86/intel: Consolidate MSR_IA32_PERF_CFG_C tracking

Both Auto Counter Reload (ACR) and Architectural PEBS use the PERF_CFG_C
MSRs to configure event behavior. Currently, the driver maintains two
independent variables acr_cfg_c and cfg_c_val to cache the values intended
for these MSRs.

Using separate variables to track a single hardware register state is
error-prone and can lead to configuration conflicts. Consolidate the
tracking into a single cfg_c_val variable to ensure a unified and
consistent view of the PERF_CFG_C MSR state.

Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://patch.msgid.link/20260430002558.712334-6-dapeng1.mi@xxxxxxxxxxxxxxx
---
 arch/x86/events/intel/core.c | 13 +++++++------
 arch/x86/events/perf_event.h |  4 +---
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index dd1e3aa..2b05587 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3169,10 +3169,10 @@ static void intel_pmu_config_acr(int idx, u64 mask, u32 reload)
 		wrmsrl(msr_b + msr_offset, mask);
 		cpuc->acr_cfg_b[idx] = mask;
 	}
-	/* Only need to update the reload value when there is a valid config value. */
-	if (mask && cpuc->acr_cfg_c[idx] != reload) {
+	/* Only update CFG_C reload when ACR is actively enabled (mask != 0) */
+	if (mask && ((cpuc->cfg_c_val[idx] & ARCH_PEBS_RELOAD) != reload)) {
 		wrmsrl(msr_c + msr_offset, reload);
-		cpuc->acr_cfg_c[idx] = reload;
+		cpuc->cfg_c_val[idx] = reload;
 	}
 }
 
@@ -3198,14 +3198,15 @@ static void intel_pmu_enable_event_ext(struct perf_event *event)
 {
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	struct hw_perf_event *hwc = &event->hw;
-	union arch_pebs_index old, new;
-	struct arch_pebs_cap cap;
 	u64 ext = 0;
 
-	cap = hybrid(cpuc->pmu, arch_pebs_cap);
+	if (is_acr_event_group(event))
+		ext |= (-hwc->sample_period) & ARCH_PEBS_RELOAD;
 
 	if (event->attr.precise_ip) {
 		u64 pebs_data_cfg = intel_get_arch_pebs_data_config(event);
+		struct arch_pebs_cap cap = hybrid(cpuc->pmu, arch_pebs_cap);
+		union arch_pebs_index old, new;
 
 		ext |= ARCH_PEBS_EN;
 		if (hwc->flags & PERF_X86_EVENT_AUTO_RELOAD)
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 524668d..40d6fe0 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -322,10 +322,8 @@ struct cpu_hw_events {
 	u64			fixed_ctrl_val;
 	u64			active_fixed_ctrl_val;
 
-	/* Intel ACR configuration */
+	/* Intel ACR/arch-PEBS configuration */
 	u64			acr_cfg_b[X86_PMC_IDX_MAX];
-	u64			acr_cfg_c[X86_PMC_IDX_MAX];
-	/* Cached CFG_C values */
 	u64			cfg_c_val[X86_PMC_IDX_MAX];
 
 	/*