On 8/21/20 6:25 PM, Anchal Agarwal wrote:

From: Munehisa Kamata <redacted>  

Guest hibernation is different from xen suspend/resume/live migration.
Xen save/restore does not use pm_ops as is needed by guest hibernation.
Hibernation in guest follows ACPI path and is guest inititated , the
hibernation image is saved within guest as compared to later modes
which are xen toolstack assisted and image creation/storage is in
control of hypervisor/host machine.
To differentiate between Xen suspend and PM hibernation, keep track
of the on-going suspend mode by mainly using a new API to keep track of
SHUTDOWN_SUSPEND state.
Introduce a simple function that keeps track of on-going suspend mode
so that PM hibernation code can behave differently according to the
current suspend mode.
Since Xen suspend doesn't have corresponding PM event, its main logic
is modfied to acquire pm_mutex.

lock_system_sleep() is not taking this mutex.

Though, accquirng pm_mutex is still right thing to do, we may
see deadlock if PM hibernation is interrupted by Xen suspend.
PM hibernation depends on xenwatch thread to process xenbus state
transactions, but the thread will sleep to wait pm_mutex which is
already held by PM hibernation context in the scenario. Xen shutdown
code may need some changes to avoid the issue.

Is it Xen's shutdown or suspend code that needs to address this? (Or I
may not understand what the problem is that you are describing)

+
+static int xen_pm_notifier(struct notifier_block *notifier,
+	unsigned long pm_event, void *unused)
+{
+	int ret;
+
+	switch (pm_event) {
+	case PM_SUSPEND_PREPARE:
+	case PM_HIBERNATION_PREPARE:
+	/* Guest hibernation is not supported for aarch64 currently*/
+	if (IS_ENABLED(CONFIG_ARM64)) {
+		ret = NOTIFY_BAD;
+		break;
+	}

Indentation.

+	case PM_RESTORE_PREPARE:
+	case PM_POST_SUSPEND:
+	case PM_POST_HIBERNATION:
+	case PM_POST_RESTORE:
+	default:
+		ret = NOTIFY_OK;
+	}
+	return ret;
+};

This whole routine now is

	if (IS_ENABLED(CONFIG_ARM64))
		return NOTIFY_BAD;

	return NOTIFY_OK;

isn't it?

+
+static struct notifier_block xen_pm_notifier_block = {
+	.notifier_call = xen_pm_notifier
+};
+
+static int xen_setup_pm_notifier(void)
+{
+	if (!xen_hvm_domain() || xen_initial_domain())
+		return -ENODEV;

I don't think this works anymore.

In the past your notifier would set suspend_mode (or something) but now
it really doesn't do anything except reports an error in some (ARM) cases.

So I think you should move this check into the notifier.

(And BTW I still think PM_SUSPEND_PREPARE should return an error too.
The fact that we are using "suspend" in xen routine names is irrelevant)



-boris

+	return register_pm_notifier(&xen_pm_notifier_block);
+}
+