diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index b36e8785c199f4563d2d3727bafbe2ae62365149..a6de0a8c1dc64611928ce3356dce0f1577c4b8eb 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -122,6 +122,7 @@ void wbinvd_on_cpu(int cpu);
 int wbinvd_on_all_cpus(void);
 
 void smp_kick_mwait_play_dead(void);
+void __noreturn mwait_play_dead(unsigned int eax_hint);
 
 void native_smp_send_reschedule(int cpu);
 void native_send_call_func_ipi(const struct cpumask *mask);
@@ -172,6 +173,8 @@ static inline struct cpumask *cpu_llc_shared_mask(int cpu)
 {
 	return (struct cpumask *)cpumask_of(0);
 }
+
+static inline void __noreturn mwait_play_dead(unsigned int eax_hint) { BUG(); }
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_DEBUG_NMI_SELFTEST
diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index 76b1d87f1531d1328338ad315c5950fd9a77f8a3..ff09685f00ba5212243ab66c4d87e365a2edff72 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -220,6 +220,16 @@ static inline bool topology_is_primary_thread(unsigned int cpu)
 	return cpumask_test_cpu(cpu, cpu_primary_thread_mask);
 }
 
+int topology_get_primary_thread(unsigned int cpu);
+
+static inline bool topology_is_core_online(unsigned int cpu)
+{
+	int pcpu = topology_get_primary_thread(cpu);
+
+	return pcpu >= 0 ? cpu_online(pcpu) : false;
+}
+#define topology_is_core_online topology_is_core_online
+
 #else /* CONFIG_SMP */
 static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; }
 static inline int topology_max_smt_threads(void) { return 1; }
diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index a851e580689a32099f123461a16d8ab673f5d0ab..8d4c9cff0b5bbc136f7f77c0378a0dee491981ea 100644
--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -15,6 +15,7 @@
 #include <acpi/processor.h>
 #include <asm/mwait.h>
 #include <asm/special_insns.h>
+#include <asm/smp.h>
 
 /*
  * Initialize bm_flags based on the CPU cache properties
@@ -204,6 +205,16 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,
 }
 EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe);
 
+void __noreturn acpi_processor_ffh_play_dead(struct acpi_processor_cx *cx)
+{
+	unsigned int cpu = smp_processor_id();
+	struct cstate_entry *percpu_entry;
+
+	percpu_entry = per_cpu_ptr(cpu_cstate_entry, cpu);
+	mwait_play_dead(percpu_entry->states[cx->index].eax);
+}
+EXPORT_SYMBOL_GPL(acpi_processor_ffh_play_dead);
+
 void __cpuidle acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cx)
 {
 	unsigned int cpu = smp_processor_id();
diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index a8d1cc6d223df9fbe5b6f3aab5f72ba31f1b19e3..cd0cfd42ea8b0bbdb6cf0fabbb9f7453e7ff5d55 100644
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -371,6 +371,19 @@ unsigned int topology_unit_count(u32 apicid, enum x86_topology_domains which_uni
 	return topo_unit_count(lvlid, at_level, apic_maps[which_units].map);
 }
 
+#ifdef CONFIG_SMP
+int topology_get_primary_thread(unsigned int cpu)
+{
+	u32 apic_id = cpuid_to_apicid[cpu];
+
+	/*
+	 * Get the core domain level APIC id, which is the primary thread
+	 * and return the CPU number assigned to it.
+	 */
+	return topo_lookup_cpuid(topo_apicid(apic_id, TOPO_CORE_DOMAIN));
+}
+#endif
+
 #ifdef CONFIG_ACPI_HOTPLUG_CPU
 /**
  * topology_hotplug_apic - Handle a physical hotplugged APIC after boot
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index e1dcb241b2e10458fcc74f65c211cf1d3a746b88..c51e103bca79a272d8a49dcd5637edf11aec5855 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -942,9 +942,6 @@ static bool __init mwait_pc10_supported(void)
 	if (!cpu_feature_enabled(X86_FEATURE_MWAIT))
 		return false;
 
-	if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
-		return false;
-
 	cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &mwait_substates);
 
 	return (ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) &&
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 96a771f9f930a6aba1b77967169808bce3b3eace..1e8e6efe8ddffa8d532294ca808644b94ef944b8 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -295,3 +295,27 @@ struct smp_ops smp_ops = {
 	.send_call_func_single_ipi = native_send_call_func_single_ipi,
 };
 EXPORT_SYMBOL_GPL(smp_ops);
+
+int arch_cpu_rescan_dead_smt_siblings(void)
+{
+	enum cpuhp_smt_control old = cpu_smt_control;
+	int ret;
+
+	/*
+	 * If SMT has been disabled and SMT siblings are in HLT, bring them back
+	 * online and offline them again so that they end up in MWAIT proper.
+	 *
+	 * Called with hotplug enabled.
+	 */
+	if (old != CPU_SMT_DISABLED && old != CPU_SMT_FORCE_DISABLED)
+		return 0;
+
+	ret = cpuhp_smt_enable();
+	if (ret)
+		return ret;
+
+	ret = cpuhp_smt_disable(old);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(arch_cpu_rescan_dead_smt_siblings);
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index c3ac9e6025582426d18e53a5b5a62a426b4b18c6..9b818af170ed0d1dc338bdf9d45d9246dbab3523 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1293,45 +1293,9 @@ void play_dead_common(void)
  * We need to flush the caches before going to sleep, lest we have
  * dirty data in our caches when we come back up.
  */
-static inline void mwait_play_dead(void)
+void __noreturn mwait_play_dead(unsigned int eax_hint)
 {
 	struct mwait_cpu_dead *md = this_cpu_ptr(&mwait_cpu_dead);
-	unsigned int eax, ebx, ecx, edx;
-	unsigned int highest_cstate = 0;
-	unsigned int highest_subcstate = 0;
-	int i;
-
-	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
-	    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
-		return;
-	if (!this_cpu_has(X86_FEATURE_MWAIT))
-		return;
-	if (!this_cpu_has(X86_FEATURE_CLFLUSH))
-		return;
-	if (__this_cpu_read(cpu_info.cpuid_level) < CPUID_MWAIT_LEAF)
-		return;
-
-	eax = CPUID_MWAIT_LEAF;
-	ecx = 0;
-	native_cpuid(&eax, &ebx, &ecx, &edx);
-
-	/*
-	 * eax will be 0 if EDX enumeration is not valid.
-	 * Initialized below to cstate, sub_cstate value when EDX is valid.
-	 */
-	if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED)) {
-		eax = 0;
-	} else {
-		edx >>= MWAIT_SUBSTATE_SIZE;
-		for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
-			if (edx & MWAIT_SUBSTATE_MASK) {
-				highest_cstate = i;
-				highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
-			}
-		}
-		eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
-			(highest_subcstate - 1);
-	}
 
 	/* Set up state for the kexec() hack below */
 	md->status = CPUDEAD_MWAIT_WAIT;
@@ -1352,7 +1316,7 @@ static inline void mwait_play_dead(void)
 		mb();
 		__monitor(md, 0, 0);
 		mb();
-		__mwait(eax, 0);
+		__mwait(eax_hint, 0);
 
 		if (READ_ONCE(md->control) == CPUDEAD_MWAIT_KEXEC_HLT) {
 			/*
@@ -1417,9 +1381,9 @@ void native_play_dead(void)
 	play_dead_common();
 	tboot_shutdown(TB_SHUTDOWN_WFS);
 
-	mwait_play_dead();
-	if (cpuidle_play_dead())
-		hlt_play_dead();
+	/* Below returns only on error. */
+	cpuidle_play_dead();
+	hlt_play_dead();
 }
 
 #else /* ... !CONFIG_HOTPLUG_CPU */
diff --git a/arch/x86/power/hibernate.c b/arch/x86/power/hibernate.c
index d8af46e6775034a49211c07431f3d35433c5ff29..ee3c56af548ece29e423232c2cf9d83db43c16d8 100644
--- a/arch/x86/power/hibernate.c
+++ b/arch/x86/power/hibernate.c
@@ -188,7 +188,8 @@ int relocate_restore_code(void)
 
 int arch_resume_nosmt(void)
 {
-	int ret = 0;
+	int ret;
+
 	/*
 	 * We reached this while coming out of hibernation. This means
 	 * that SMT siblings are sleeping in hlt, as mwait is not safe
@@ -202,18 +203,10 @@ int arch_resume_nosmt(void)
 	 * Called with hotplug disabled.
 	 */
 	cpu_hotplug_enable();
-	if (cpu_smt_control == CPU_SMT_DISABLED ||
-			cpu_smt_control == CPU_SMT_FORCE_DISABLED) {
-		enum cpuhp_smt_control old = cpu_smt_control;
-
-		ret = cpuhp_smt_enable();
-		if (ret)
-			goto out;
-		ret = cpuhp_smt_disable(old);
-		if (ret)
-			goto out;
-	}
-out:
+
+	ret = arch_cpu_rescan_dead_smt_siblings();
+
 	cpu_hotplug_disable();
+
 	return ret;
 }
diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
index 71e25c7989762870b9871472e4d7ddb503a3e95d..5af09a6f84e44e58ecef16ae4b7172df16d0f5e5 100644
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -41,8 +41,6 @@ static void power_saving_mwait_init(void)
 
 	if (!boot_cpu_has(X86_FEATURE_MWAIT))
 		return;
-	if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
-		return;
 
 	cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
 
diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 1e8ee97fc85f38c49182c2c574c8d254a33be79d..a7fb8a3038bdd793841c755683624b18a7ae6f25 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -155,6 +155,12 @@ bool processor_physically_present(acpi_handle handle);
 static inline void acpi_early_processor_control_setup(void) {}
 #endif
 
+#ifdef CONFIG_ACPI_PROCESSOR_CSTATE
+void acpi_idle_rescan_dead_smt_siblings(void);
+#else
+static inline void acpi_idle_rescan_dead_smt_siblings(void) {}
+#endif
+
 /* --------------------------------------------------------------------------
                                   Embedded Controller
    -------------------------------------------------------------------------- */
diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index 4bd16b3f0781481f6cfd54d760f47f3ad54b405a..126643dde2d4a3c733ebee3b968f244664e860e8 100644
--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -283,6 +283,9 @@ static int __init acpi_processor_driver_init(void)
 				  NULL, acpi_soft_cpu_dead);
 
 	acpi_processor_throttling_init();
+
+	acpi_idle_rescan_dead_smt_siblings();
+
 	return 0;
 err:
 	driver_unregister(&acpi_processor_driver);
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 86e026c49aeb31e745d735ac8c8fcc811e1a23cc..24b56b074860dee414e31af3655288fac20d0c07 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -24,6 +24,8 @@
 #include <acpi/processor.h>
 #include <linux/context_tracking.h>
 
+#include "internal.h"
+
 /*
  * Include the apic definitions for x86 to have the APIC timer related defines
  * available also for UP (on SMP it gets magically included via linux/smp.h).
@@ -55,6 +57,12 @@ struct cpuidle_driver acpi_idle_driver = {
 };
 
 #ifdef CONFIG_ACPI_PROCESSOR_CSTATE
+void acpi_idle_rescan_dead_smt_siblings(void)
+{
+	if (cpuidle_get_driver() == &acpi_idle_driver)
+		arch_cpu_rescan_dead_smt_siblings();
+}
+
 static
 DEFINE_PER_CPU(struct acpi_processor_cx * [CPUIDLE_STATE_MAX], acpi_cstate);
 
@@ -588,7 +596,7 @@ static void __cpuidle acpi_idle_do_entry(struct acpi_processor_cx *cx)
  * @dev: the target CPU
  * @index: the index of suggested state
  */
-static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
+static void acpi_idle_play_dead(struct cpuidle_device *dev, int index)
 {
 	struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);
 
@@ -600,12 +608,11 @@ static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
 			raw_safe_halt();
 		else if (cx->entry_method == ACPI_CSTATE_SYSTEMIO) {
 			io_idle(cx->address);
+		} else if (cx->entry_method == ACPI_CSTATE_FFH) {
+			acpi_processor_ffh_play_dead(cx);
 		} else
-			return -ENODEV;
+			return;
 	}
-
-	/* Never reached */
-	return 0;
 }
 
 static __always_inline bool acpi_idle_fallback_to_c1(struct acpi_processor *pr)
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 6704d610573ad653133df994daa2778c2173e053..c075e0e1ab6ae400916ba62ae0a6e70ba6b73d1e 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -69,11 +69,15 @@ int cpuidle_play_dead(void)
 	if (!drv)
 		return -ENODEV;
 
-	/* Find lowest-power state that supports long-term idle */
-	for (i = drv->state_count - 1; i >= 0; i--)
+	for (i = drv->state_count - 1; i >= 0; i--) {
 		if (drv->states[i].enter_dead)
-			return drv->states[i].enter_dead(dev, i);
+			drv->states[i].enter_dead(dev, i);
+	}
 
+	/*
+	 * If :enter_dead() is successful, it will never return, so reaching
+	 * here means that all of them failed above or were not present.
+	 */
 	return -ENODEV;
 }
 
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 21dfe0d73ef4b0467493931771e830d1a78c36de..c576d614a8e5b033f44fb928e2022171f4a7df09 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -58,6 +58,7 @@
 #include <asm/msr.h>
 #include <asm/tsc.h>
 #include <asm/fpu/api.h>
+#include <asm/smp.h>
 
 #define INTEL_IDLE_VERSION "0.5.1"
 
@@ -228,6 +229,15 @@ static __cpuidle int intel_idle_s2idle(struct cpuidle_device *dev,
 	return 0;
 }
 
+static void intel_idle_enter_dead(struct cpuidle_device *dev, int index)
+{
+	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
+	struct cpuidle_state *state = &drv->states[index];
+	unsigned long eax = flg2MWAIT(state->flags);
+
+	mwait_play_dead(eax);
+}
+
 /*
  * States are indexed by the cstate number,
  * which is also the index into the MWAIT hint array.
@@ -1727,6 +1737,7 @@ static void __init intel_idle_init_cstates_acpi(struct cpuidle_driver *drv)
 			mark_tsc_unstable("TSC halts in idle");
 
 		state->enter = intel_idle;
+		state->enter_dead = intel_idle_enter_dead;
 		state->enter_s2idle = intel_idle_s2idle;
 	}
 }
@@ -2073,6 +2084,9 @@ static void __init intel_idle_init_cstates_icpu(struct cpuidle_driver *drv)
 		    !cpuidle_state_table[cstate].enter_s2idle)
 			break;
 
+		if (!cpuidle_state_table[cstate].enter_dead)
+			cpuidle_state_table[cstate].enter_dead = intel_idle_enter_dead;
+
 		/* If marked as unusable, skip this state. */
 		if (cpuidle_state_table[cstate].flags & CPUIDLE_FLAG_UNUSABLE) {
 			pr_debug("state %s is disabled\n",
@@ -2242,9 +2256,6 @@ static int __init intel_idle_init(void)
 			return -ENODEV;
 	}
 
-	if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
-		return -ENODEV;
-
 	cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &mwait_substates);
 
 	if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
@@ -2291,6 +2302,8 @@ static int __init intel_idle_init(void)
 	pr_debug("Local APIC timer is reliable in %s\n",
 		 boot_cpu_has(X86_FEATURE_ARAT) ? "all C-states" : "C1");
 
+	arch_cpu_rescan_dead_smt_siblings();
+
 	return 0;
 
 hp_setup_fail:
@@ -2301,7 +2314,7 @@ static int __init intel_idle_init(void)
 	return retval;
 
 }
-device_initcall(intel_idle_init);
+subsys_initcall_sync(intel_idle_init);
 
 /*
  * We are not really modular, but we used to support that.  Meaning we also
diff --git a/include/acpi/processor.h b/include/acpi/processor.h
index 3f34ebb275253e281fbecaad602a0531b1e6e55d..034edf4178be2f90751b4e151d963188572a3021 100644
--- a/include/acpi/processor.h
+++ b/include/acpi/processor.h
@@ -280,6 +280,7 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,
 				    struct acpi_processor_cx *cx,
 				    struct acpi_power_register *reg);
 void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cstate);
+void __noreturn acpi_processor_ffh_play_dead(struct acpi_processor_cx *cx);
 #else
 static inline void acpi_processor_power_init_bm_check(struct
 						      acpi_processor_flags
@@ -300,6 +301,10 @@ static inline void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx
 {
 	return;
 }
+static inline void __noreturn acpi_processor_ffh_play_dead(struct acpi_processor_cx *cx)
+{
+	BUG();
+}
 #endif
 
 static inline int call_on_cpu(int cpu, long (*fn)(void *), void *arg,
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 8e596dc11a0ff5ee80d57b92caf560790d17e52e..afbaf476237143e2f27b0670b34f6518975b5c5f 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -115,6 +115,7 @@ extern void cpu_maps_update_begin(void);
 extern void cpu_maps_update_done(void);
 int bringup_hibernate_cpu(unsigned int sleep_cpu);
 void bringup_nonboot_cpus(unsigned int setup_max_cpus);
+int arch_cpu_rescan_dead_smt_siblings(void);
 
 #else	/* CONFIG_SMP */
 #define cpuhp_tasks_frozen	0
@@ -129,6 +130,8 @@ static inline void cpu_maps_update_done(void)
 
 static inline int add_cpu(unsigned int cpu) { return 0;}
 
+static inline int arch_cpu_rescan_dead_smt_siblings(void) { return 0; }
+
 #endif /* CONFIG_SMP */
 extern struct bus_type cpu_subsys;
 
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 3183aeb7f5b4238a2b88349ae4bf8c492475460f..a9ee4fe55dcfcca8200cc69b9651f91ca1b6b696 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -61,7 +61,7 @@ struct cpuidle_state {
 			struct cpuidle_driver *drv,
 			int index);
 
-	int (*enter_dead) (struct cpuidle_device *dev, int index);
+	void (*enter_dead) (struct cpuidle_device *dev, int index);
 
 	/*
 	 * CPUs execute ->enter_s2idle with the local tick or entire timekeeping
diff --git a/tools/objtool/noreturns.h b/tools/objtool/noreturns.h
index 80a3e6acf31e4b962f7b79fb10d98192e08013f6..57cb18636e34c13d7df3e840e37e2ecfa1d0a71e 100644
--- a/tools/objtool/noreturns.h
+++ b/tools/objtool/noreturns.h
@@ -12,6 +12,7 @@ NORETURN(__reiserfs_panic)
 NORETURN(__stack_chk_fail)
 NORETURN(__ubsan_handle_builtin_unreachable)
 NORETURN(arch_call_rest_init)
+NORETURN(acpi_processor_ffh_play_dead)
 NORETURN(arch_cpu_idle_dead)
 NORETURN(cpu_bringup_and_idle)
 NORETURN(cpu_startup_entry)
@@ -28,6 +29,7 @@ NORETURN(kunit_try_catch_throw)
 NORETURN(machine_real_restart)
 NORETURN(make_task_dead)
 NORETURN(mpt_halt_firmware)
+NORETURN(mwait_play_dead)
 NORETURN(nmi_panic_self_stop)
 NORETURN(panic)
 NORETURN(panic_smp_self_stop)