Re: [PATCH v2 5/6] perf/x86: Enable NMI source reporting for perfmon
From: H. Peter Anvin
Date: Tue Jun 11 2024 - 15:11:30 EST
On 6/11/24 09:54, Jacob Pan wrote:
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 1ef2201e48ac..db8c30881f5c 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -46,6 +46,7 @@
struct x86_pmu x86_pmu __read_mostly;
static struct pmu pmu;
+u32 apic_perfmon_ctr = APIC_DM_NMI;
DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events) = {
.enabled = 1,
@@ -1680,7 +1681,7 @@ int x86_pmu_handle_irq(struct pt_regs *regs)
* This generic handler doesn't seem to have any issues where the
* unmasking occurs so it was left at the top.
*/
- apic_write(APIC_LVTPC, APIC_DM_NMI);
+ apic_write(APIC_LVTPC, apic_perfmon_ctr);
for (idx = 0; idx < x86_pmu.num_counters; idx++) {
if (!test_bit(idx, cpuc->active_mask))
@@ -1723,7 +1724,10 @@ void perf_events_lapic_init(void)
/*
* Always use NMI for PMU
*/
- apic_write(APIC_LVTPC, APIC_DM_NMI);
+ if (cpu_feature_enabled(X86_FEATURE_NMI_SOURCE))
+ apic_perfmon_ctr |= NMI_SOURCE_VEC_PMI;
+
+ apic_write(APIC_LVTPC, apic_perfmon_ctr);
}
There really is no reason to not do this unconditinoally. If NMI source
is not supported it is simply a noop.
-hpa