[PATCH 2/2] PM: s2idle: Fully block the system from entering s2idle when cpuidle isn't supported

[Kazuki H]

s2idle isn't supported on platforms that don't support cpuidle as of
31a3409065d1 ("cpuidle / sleep: Do sanity checks in cpuidle_enter_freeze()
too").

There is a check in the cpuidle subsystem which would prevent the
system from entering s2idle. However, there is nothing in the suspend
framework which prevents this, which can cause the suspend subsystem to
think that the machine is entering s2idle while the cpuidle subsystem is
not, which can completely break the system.

Block the machine from entering s2idle when cpuidle isn't supported in
the suspend subsystem as well.

Link: https://lore.kernel.org/all/20230204152747.drte4uitljzngdt6@kazuki-mac
Fixes: 31a3409065d1 ("cpuidle / sleep: Do sanity checks in cpuidle_enter_freeze() too")
Signed-off-by: Kazuki H <kazukih0205@xxxxxxxxx>
---
 kernel/power/main.c    | 12 +++++++++---
 kernel/power/suspend.c |  5 +++++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/kernel/power/main.c b/kernel/power/main.c
index 31ec4a9b9d70..b14765447989 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -133,6 +133,8 @@ static ssize_t mem_sleep_show(struct kobject *kobj, struct kobj_attribute *attr,
 	for (i = PM_SUSPEND_MIN; i < PM_SUSPEND_MAX; i++) {
 		if (i >= PM_SUSPEND_MEM && cxl_mem_active())
 			continue;
+		if (i == PM_SUSPEND_TO_IDLE && cpuidle_not_available())
+			continue;
 		if (mem_sleep_states[i]) {
 			const char *label = mem_sleep_states[i];
 
@@ -185,11 +187,15 @@ static ssize_t mem_sleep_store(struct kobject *kobj, struct kobj_attribute *attr
 	}
 
 	state = decode_suspend_state(buf, n);
-	if (state < PM_SUSPEND_MAX && state > PM_SUSPEND_ON)
+	if (state == PM_SUSPEND_TO_IDLE && cpuidle_not_available())
+		goto einval;
+	if (state < PM_SUSPEND_MAX && state > PM_SUSPEND_ON) {
 		mem_sleep_current = state;
-	else
-		error = -EINVAL;
+		goto out;
+	}
 
+ einval:
+	error = -EINVAL;
  out:
 	pm_autosleep_unlock();
 	return error ? error : n;
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 3f436282547c..55ddf525aaaf 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -556,6 +556,11 @@ static int enter_state(suspend_state_t state)
 
 	trace_suspend_resume(TPS("suspend_enter"), state, true);
 	if (state == PM_SUSPEND_TO_IDLE) {
+		if (cpuidle_not_available()) {
+			pr_warn("s2idle is unsupported when cpuidle is unavailable");
+			return -EINVAL;
+		}
+
 #ifdef CONFIG_PM_DEBUG
 		if (pm_test_level != TEST_NONE && pm_test_level <= TEST_CPUS) {
 			pr_warn("Unsupported test mode for suspend to idle, please choose none/freezer/devices/platform.\n");
-- 
2.40.0