Merge tag 'pm-5.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management fixes from Rafael Wysocki:
 "These fix a crash during resume from hibernation introduced during the
  4.19 cycle, cause the new Performance and Energy Bias Hint (EPB) code
  to be built only if CONFIG_PM is set and add a few missing kerneldoc
  comments.

  Specifics:

   - Fix a crash that occurs when a kernel with 'nosmt' in the command
     line is used to resume the system from hibernation (as the
     "restore" kernel), because memory mapping differences between the
     restore and image kernels cause SMT siblings to be woken up from
     idle states and subsequently they try to fetch instructions from
     incorrect memory locations (Jiri Kosina).

   - Cause the new Performance and Energy Bias Hint (EPB) code to be
     built only if CONFIG_PM is set, because that code is not really
     necessary otherwise (Rafael Wysocki).

   - Add kerneldoc comments to documents some helper functions related
     to system-wide suspend to avoid possible confusion regarding their
     purpose (Rafael Wysocki)"

* tag 'pm-5.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  x86/power: Fix 'nosmt' vs hibernation triple fault during resume
  PM: sleep: Add kerneldoc comments to some functions
  x86: intel_epb: Do not build when CONFIG_PM is unset

kernel/cpu.c

@@ -2061,7 +2061,7 @@ static void cpuhp_online_cpu_device(unsigned int cpu)
 	kobject_uevent(&dev->kobj, KOBJ_ONLINE);
 }
 
-static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
+int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
 {
 	int cpu, ret = 0;
 
@@ -2093,7 +2093,7 @@ static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
 	return ret;
 }
 
-static int cpuhp_smt_enable(void)
+int cpuhp_smt_enable(void)
 {
 	int cpu, ret = 0;
 

kernel/power/hibernate.c

@@ -257,6 +257,11 @@ void swsusp_show_speed(ktime_t start, ktime_t stop,
 		(kps % 1000) / 10);
 }
 
+__weak int arch_resume_nosmt(void)
+{
+	return 0;
+}
+
 /**
  * create_image - Create a hibernation image.
  * @platform_mode: Whether or not to use the platform driver.
@@ -324,6 +329,10 @@ static int create_image(int platform_mode)
  Enable_cpus:
 	suspend_enable_secondary_cpus();
 
+	/* Allow architectures to do nosmt-specific post-resume dances */
+	if (!in_suspend)
+		error = arch_resume_nosmt();
+
  Platform_finish:
 	platform_finish(platform_mode);
 

kernel/power/suspend.c

@@ -62,6 +62,12 @@ static DECLARE_SWAIT_QUEUE_HEAD(s2idle_wait_head);
 enum s2idle_states __read_mostly s2idle_state;
 static DEFINE_RAW_SPINLOCK(s2idle_lock);
 
+/**
+ * pm_suspend_via_s2idle - Check if suspend-to-idle is the default suspend.
+ *
+ * Return 'true' if suspend-to-idle has been selected as the default system
+ * suspend method.
+ */
 bool pm_suspend_via_s2idle(void)
 {
 	return mem_sleep_current == PM_SUSPEND_TO_IDLE;