Index: sys/amd64/amd64/apic_vector.S
===================================================================
--- sys/amd64/amd64/apic_vector.S
+++ sys/amd64/amd64/apic_vector.S
@@ -150,6 +150,15 @@
 	KMSAN_LEAVE
 	jmp	doreti
 
+/*
+ * Local APIC thermal interrupt handler.
+ */
+	INTR_HANDLER thermalint
+	KMSAN_ENTER
+	call	lapic_handle_thermal
+	KMSAN_LEAVE
+	jmp	doreti
+
 #ifdef XENHVM
 /*
  * Xen event channel upcall interrupt handler.
Index: sys/x86/include/apicvar.h
===================================================================
--- sys/x86/include/apicvar.h
+++ sys/x86/include/apicvar.h
@@ -178,12 +178,12 @@
 inthand_t
 	IDTVEC(apic_isr1), IDTVEC(apic_isr2), IDTVEC(apic_isr3),
 	IDTVEC(apic_isr4), IDTVEC(apic_isr5), IDTVEC(apic_isr6),
-	IDTVEC(apic_isr7), IDTVEC(cmcint), IDTVEC(errorint),
-	IDTVEC(spuriousint), IDTVEC(timerint),
+	IDTVEC(apic_isr7), IDTVEC(cmcint), IDTVEC(thermalint),
+	IDTVEC(errorint), IDTVEC(spuriousint), IDTVEC(timerint),
 	IDTVEC(apic_isr1_pti), IDTVEC(apic_isr2_pti), IDTVEC(apic_isr3_pti),
 	IDTVEC(apic_isr4_pti), IDTVEC(apic_isr5_pti), IDTVEC(apic_isr6_pti),
-	IDTVEC(apic_isr7_pti), IDTVEC(cmcint_pti), IDTVEC(errorint_pti),
-	IDTVEC(spuriousint_pti), IDTVEC(timerint_pti);
+	IDTVEC(apic_isr7_pti), IDTVEC(cmcint_pti), IDTVEC(thermalint_pti),
+	IDTVEC(errorint_pti), IDTVEC(spuriousint_pti), IDTVEC(timerint_pti);
 
 extern vm_paddr_t lapic_paddr;
 extern int *apic_cpuids;
@@ -224,6 +224,8 @@
 void	apic_disable_vector(u_int apic_id, u_int vector);
 void	apic_free_vector(u_int apic_id, u_int vector, u_int irq);
 void	lapic_calibrate_timer(void);
+void	lapic_enable_thermal(void (* thermfunc)(int, void *), void *value);
+void	lapic_disable_thermal(void);
 int	lapic_enable_pmc(void);
 void	lapic_disable_pmc(void);
 void	lapic_reenable_pmc(void);
@@ -248,6 +250,7 @@
 int	lapic_set_lvt_triggermode(u_int apic_id, u_int lvt,
 	    enum intr_trigger trigger);
 void	lapic_handle_cmc(void);
+void	lapic_handle_thermal(void);
 void	lapic_handle_error(void);
 void	lapic_handle_intr(int vector, struct trapframe *frame);
 void	lapic_handle_timer(struct trapframe *frame);
Index: sys/x86/x86/local_apic.c
===================================================================
--- sys/x86/x86/local_apic.c
+++ sys/x86/x86/local_apic.c
@@ -206,6 +206,8 @@
 static int __read_mostly lapic_ds_idle_timeout = 1000000;
 #endif
 unsigned int max_apic_id;
+static void *lapic_thermal_function_value = NULL;
+static void (* lapic_handle_thermal_function)(int, void *) = NULL;
 
 SYSCTL_NODE(_hw, OID_AUTO, apic, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
     "APIC options");
@@ -470,7 +472,9 @@
 	setidt(APIC_ERROR_INT, pti ? IDTVEC(errorint_pti) : IDTVEC(errorint),
 	    SDT_APIC, SEL_KPL, GSEL_APIC);
 
-	/* XXX: Thermal interrupt */
+	/* Thermal interrupt */
+	setidt(APIC_THERMAL_INT, pti ? IDTVEC(thermalint_pti) : IDTVEC(thermalint),
+	    SDT_APIC, SEL_KPL, GSEL_APIC);
 
 	/* Local APIC CMCI. */
 	setidt(APIC_CMC_INT, pti ? IDTVEC(cmcint_pti) : IDTVEC(cmcint),
@@ -768,7 +772,9 @@
 	    lapic_read32(LAPIC_LVT_ERROR)));
 	lapic_write32(LAPIC_ESR, 0);
 
-	/* XXX: Thermal LVT */
+	/* Thermal LVT */
+	lapic_write32(LAPIC_LVT_THERMAL, lvt_mode(la, APIC_LVT_THERMAL,
+	    lapic_read32(LAPIC_LVT_THERMAL)));
 
 	/* Program the CMCI LVT entry if present. */
 	if (maxlvt >= APIC_LVT_CMCI) {
@@ -1477,6 +1483,71 @@
 	return (APIC_ELVT_MCA);
 }
 
+void
+lapic_handle_thermal(void)
+{
+	if(lapic_handle_thermal_function != NULL)
+		lapic_handle_thermal_function(PCPU_GET(cpuid), lapic_thermal_function_value);
+
+	lapic_eoi();
+}
+
+static void
+lapic_update_thermal(void *nouse)
+{
+	struct lapic *la;
+
+	la = &lapics[lapic_id()];
+	lapic_write32(LAPIC_LVT_THERMAL, lvt_mode(la, APIC_LVT_THERMAL,
+	    lapic_read32(LAPIC_LVT_THERMAL)));
+}
+
+void
+lapic_enable_thermal(void (* thermfunc)(int, void *), void *value)
+{
+#ifdef DEV_ATPIC
+	if (!x2apic_mode && lapic_map == NULL)
+		return;
+#endif
+
+	lapic_handle_thermal_function = thermfunc;
+	lapic_thermal_function_value = value;
+
+	lvts[APIC_LVT_THERMAL].lvt_masked = 0;
+
+#ifdef EARLY_AP_STARTUP
+	MPASS(mp_ncpus == 1 || smp_started);
+	smp_rendezvous(NULL, lapic_update_thermal, NULL, NULL);
+#else
+#ifdef SMP
+	if (smp_started)
+		smp_rendezvous(NULL, lapic_update_thermal, NULL, NULL);
+	else
+#endif
+		lapic_update_thermal(NULL);
+#endif
+}
+
+void
+lapic_disable_thermal(void)
+{
+#ifdef DEV_ATPIC
+	/* Fail if the local APIC is not present. */
+	if (!x2apic_mode && lapic_map == NULL)
+		return;
+#endif
+
+	lvts[APIC_LVT_THERMAL].lvt_masked = 1;
+
+#ifdef SMP
+	KASSERT(mp_ncpus == 1 || smp_started, ("thermal driver unloaded too early"));
+#endif
+	smp_rendezvous(NULL, lapic_update_thermal, NULL, NULL);
+
+	lapic_handle_thermal_function = NULL;
+	lapic_thermal_function_value = NULL;
+}
+
 void
 lapic_handle_error(void)
 {