linux-kernel - [PATCH v6 8/9] perf/x86: Enable NMI-source reporting for perfmon

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Message-ID: <20250513203803.2636561-9-sohil.mehta@intel.com>
Date: Tue, 13 May 2025 13:38:02 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: x86@...nel.org,
	linux-kernel@...r.kernel.org
Cc: Xin Li <xin@...or.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Tony Luck <tony.luck@...el.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sohil Mehta <sohil.mehta@...el.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Jacob Pan <jacob.pan@...ux.microsoft.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Kai Huang <kai.huang@...el.com>,
	Sandipan Das <sandipan.das@....com>,
	linux-perf-users@...r.kernel.org,
	linux-edac@...r.kernel.org,
	kvm@...r.kernel.org,
	linux-pm@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH v6 8/9] perf/x86: Enable NMI-source reporting for perfmon

From: Jacob Pan <jacob.jun.pan@...ux.intel.com>

Program the designated PMI NMI-source vector into the local vector table
for the PMU. An NMI for the PMU would directly invoke the PMI handler
without polling other NMI handlers, resulting in reduced PMI delivery
latency.

Co-developed-by: Zeng Guang <guang.zeng@...el.com>
Signed-off-by: Zeng Guang <guang.zeng@...el.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
Tested-by: Sandipan Das <sandipan.das@....com> # AMD overlapping bits
---
v6: Picked up a tested-by tag.

v5: No significant change.
---
 arch/x86/events/core.c       | 4 ++--
 arch/x86/events/intel/core.c | 6 +++---
 arch/x86/include/asm/apic.h  | 1 +
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 031e908f0d61..42b270526631 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1695,7 +1695,7 @@ 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, PERF_NMI);
 
 	for_each_set_bit(idx, x86_pmu.cntr_mask, X86_PMC_IDX_MAX) {
 		if (!test_bit(idx, cpuc->active_mask))
@@ -1737,7 +1737,7 @@ void perf_events_lapic_init(void)
 	/*
 	 * Always use NMI for PMU
 	 */
-	apic_write(APIC_LVTPC, APIC_DM_NMI);
+	apic_write(APIC_LVTPC, PERF_NMI);
 }
 
 static int
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 09d2d66c9f21..87c624686c58 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3202,7 +3202,7 @@ static int intel_pmu_handle_irq(struct pt_regs *regs)
 	 * NMI handler.
 	 */
 	if (!late_ack && !mid_ack)
-		apic_write(APIC_LVTPC, APIC_DM_NMI);
+		apic_write(APIC_LVTPC, PERF_NMI);
 	intel_bts_disable_local();
 	cpuc->enabled = 0;
 	__intel_pmu_disable_all(true);
@@ -3239,7 +3239,7 @@ static int intel_pmu_handle_irq(struct pt_regs *regs)
 
 done:
 	if (mid_ack)
-		apic_write(APIC_LVTPC, APIC_DM_NMI);
+		apic_write(APIC_LVTPC, PERF_NMI);
 	/* Only restore PMU state when it's active. See x86_pmu_disable(). */
 	cpuc->enabled = pmu_enabled;
 	if (pmu_enabled)
@@ -3252,7 +3252,7 @@ static int intel_pmu_handle_irq(struct pt_regs *regs)
 	 * Haswell CPUs.
 	 */
 	if (late_ack)
-		apic_write(APIC_LVTPC, APIC_DM_NMI);
+		apic_write(APIC_LVTPC, PERF_NMI);
 	return handled;
 }
 
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 99033bfb26ea..d637717d42bd 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -30,6 +30,7 @@
 #define BT_NMI			(APIC_DM_NMI | NMIS_VECTOR_BT)
 #define KGDB_NMI		(APIC_DM_NMI | NMIS_VECTOR_KGDB)
 #define MCE_NMI			(APIC_DM_NMI | NMIS_VECTOR_MCE)
+#define PERF_NMI		(APIC_DM_NMI | NMIS_VECTOR_PMI)
 
 /*
  * Debugging macros
-- 
2.43.0