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

4 files changed, 48 insertions, 22 deletions

diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index 1796d2bdcaaa..5102bf7c8192 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -28,7 +28,10 @@ obj-y			+= cpuid-deps.o
 obj-$(CONFIG_PROC_FS)	+= proc.o
 obj-$(CONFIG_X86_FEATURE_NAMES) += capflags.o powerflags.o
 
-obj-$(CONFIG_CPU_SUP_INTEL)		+= intel.o intel_pconfig.o intel_epb.o
+ifdef CONFIG_CPU_SUP_INTEL
+obj-y			+= intel.o intel_pconfig.o
+obj-$(CONFIG_PM)	+= intel_epb.o
+endif
 obj-$(CONFIG_CPU_SUP_AMD)		+= amd.o
 obj-$(CONFIG_CPU_SUP_HYGON)		+= hygon.o
 obj-$(CONFIG_CPU_SUP_CYRIX_32)		+= cyrix.o
diff --git a/arch/x86/kernel/cpu/intel_epb.c b/arch/x86/kernel/cpu/intel_epb.c
index ebb14a26f117..f4dd73396f28 100644
--- a/arch/x86/kernel/cpu/intel_epb.c
+++ b/arch/x86/kernel/cpu/intel_epb.c
@@ -97,7 +97,6 @@ static void intel_epb_restore(void)
 	wrmsrl(MSR_IA32_ENERGY_PERF_BIAS, (epb & ~EPB_MASK) | val);
 }
 
-#ifdef CONFIG_PM
 static struct syscore_ops intel_epb_syscore_ops = {
 	.suspend = intel_epb_save,
 	.resume = intel_epb_restore,
@@ -194,25 +193,6 @@ static int intel_epb_offline(unsigned int cpu)
 	return 0;
 }
 
-static inline void register_intel_ebp_syscore_ops(void)
-{
-	register_syscore_ops(&intel_epb_syscore_ops);
-}
-#else /* !CONFIG_PM */
-static int intel_epb_online(unsigned int cpu)
-{
-	intel_epb_restore();
-	return 0;
-}
-
-static int intel_epb_offline(unsigned int cpu)
-{
-	return intel_epb_save();
-}
-
-static inline void register_intel_ebp_syscore_ops(void) {}
-#endif
-
 static __init int intel_epb_init(void)
 {
 	int ret;
@@ -226,7 +206,7 @@ static __init int intel_epb_init(void)
 	if (ret < 0)
 		goto err_out_online;
 
-	register_intel_ebp_syscore_ops();
+	register_syscore_ops(&intel_epb_syscore_ops);
 	return 0;
 
 err_out_online:
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index a7d966964c6f..513ce09e9950 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -299,7 +299,17 @@ int hibernate_resume_nonboot_cpu_disable(void)
 	 * address in its instruction pointer may not be possible to resolve
 	 * any more at that point (the page tables used by it previously may
 	 * have been overwritten by hibernate image data).
+	 *
+	 * First, make sure that we wake up all the potentially disabled SMT
+	 * threads which have been initially brought up and then put into
+	 * mwait/cpuidle sleep.
+	 * Those will be put to proper (not interfering with hibernation
+	 * resume) sleep afterwards, and the resumed kernel will decide itself
+	 * what to do with them.
 	 */
+	ret = cpuhp_smt_enable();
+	if (ret)
+		return ret;
 	smp_ops.play_dead = resume_play_dead;
 	ret = disable_nonboot_cpus();
 	smp_ops.play_dead = play_dead;
diff --git a/arch/x86/power/hibernate.c b/arch/x86/power/hibernate.c
index 4845b8c7be7f..fc413717a45f 100644
--- a/arch/x86/power/hibernate.c
+++ b/arch/x86/power/hibernate.c
@@ -11,6 +11,7 @@
 #include <linux/suspend.h>
 #include <linux/scatterlist.h>
 #include <linux/kdebug.h>
+#include <linux/cpu.h>
 
 #include <crypto/hash.h>
 
@@ -245,3 +246,35 @@ out:
 	__flush_tlb_all();
 	return 0;
 }
+
+int arch_resume_nosmt(void)
+{
+	int ret = 0;
+	/*
+	 * We reached this while coming out of hibernation. This means
+	 * that SMT siblings are sleeping in hlt, as mwait is not safe
+	 * against control transition during resume (see comment in
+	 * hibernate_resume_nonboot_cpu_disable()).
+	 *
+	 * If the resumed kernel has SMT disabled, we have to take all the
+	 * SMT siblings out of hlt, and offline them again so that they
+	 * end up in mwait proper.
+	 *
+	 * 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:
+	cpu_hotplug_disable();
+	return ret;
+}