Merge tag 'pm-6.16-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management fixes from Rafael Wysocki:
 "These fix the cpupower utility installation, fix up the recently added
  Rust abstractions for cpufreq and OPP, restore the x86 update
  eliminating mwait_play_dead_cpuid_hint() that has been reverted during
  the 6.16 merge window along with preventing the failure caused by it
  from happening, and clean up mwait_idle_with_hints() usage in
  intel_idle:

   - Implement CpuId Rust abstraction and use it to fix doctest failure
     related to the recently introduced cpumask abstraction (Viresh
     Kumar)

   - Do minor cleanups in the `# Safety` sections for cpufreq
     abstractions added recently (Viresh Kumar)

   - Unbreak cpupower systemd service units installation on some systems
     by adding a unitdir variable for specifying the location to install
     them (Francesco Poli)

   - Eliminate mwait_play_dead_cpuid_hint() again after reverting its
     elimination during the 6.16 merge window due to a problem with
     handling "dead" SMT siblings, but this time prevent leaving them in
     C1 after initialization by taking them online and back offline when
     a proper cpuidle driver for the platform has been registered
     (Rafael Wysocki)

   - Update data types of variables passed as arguments to
     mwait_idle_with_hints() to match the function definition after
     recent changes (Uros Bizjak)"

* tag 'pm-6.16-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  rust: cpu: Add CpuId::current() to retrieve current CPU ID
  rust: Use CpuId in place of raw CPU numbers
  rust: cpu: Introduce CpuId abstraction
  intel_idle: Update arguments of mwait_idle_with_hints()
  cpufreq: Convert `/// SAFETY` lines to `# Safety` sections
  cpupower: split unitdir from libdir in Makefile
  Reapply "x86/smp: Eliminate mwait_play_dead_cpuid_hint()"
  ACPI: processor: Rescan "dead" SMT siblings during initialization
  intel_idle: Rescan "dead" SMT siblings during initialization
  x86/smp: PM/hibernate: Split arch_resume_nosmt()
  intel_idle: Use subsys_initcall_sync() for initialization

3 files changed, 37 insertions, 60 deletions

diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 18266cc3d98c..b014e6d229f9 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -299,3 +299,27 @@ 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 fc78c2325fd2..58ede3fa6a75 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1244,6 +1244,10 @@ void play_dead_common(void)
 	local_irq_disable();
 }
 
+/*
+ * We need to flush the caches before going to sleep, lest we have
+ * dirty data in our caches when we come back up.
+ */
 void __noreturn mwait_play_dead(unsigned int eax_hint)
 {
 	struct mwait_cpu_dead *md = this_cpu_ptr(&mwait_cpu_dead);
@@ -1290,50 +1294,6 @@ void __noreturn mwait_play_dead(unsigned int eax_hint)
 }
 
 /*
- * 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_cpuid_hint(void)
-{
-	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;
-
-	eax = CPUID_LEAF_MWAIT;
-	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);
-	}
-
-	mwait_play_dead(eax);
-}
-
-/*
  * Kick all "offline" CPUs out of mwait on kexec(). See comment in
  * mwait_play_dead().
  */
@@ -1383,9 +1343,9 @@ void native_play_dead(void)
 	play_dead_common();
 	tboot_shutdown(TB_SHUTDOWN_WFS);
 
-	mwait_play_dead_cpuid_hint();
-	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 a7c23f2a58c9..a2294c1649f6 100644
--- a/arch/x86/power/hibernate.c
+++ b/arch/x86/power/hibernate.c
@@ -192,7 +192,8 @@ out:
 
 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
@@ -206,18 +207,10 @@ 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;
 }