xen-pm-use-suspend.patch

From 7e1526209cf972f51281558f1cb979d18e49cdd1 Mon Sep 17 00:00:00 2001
From: Simon Gaiser <simon@invisiblethingslab.com>
Date: Tue, 30 Apr 2024 14:27:33 +0200
Subject: [PATCH] Add experimental flag to use suspend instad of freeze for Xen
 VM suspend

When suspending a VM the Xen driver currently uses the "freeze" methods
for going to sleep. This doesn't put devices in low power state, at
least for some drivers (for example USB). But for S0ix we need to put
all (real) devices into their low power state. For this the "suspend"
methods needs to be used.

(See Documentation/driver-api/pm/devices.rst for description of those
methods.)

To be able to include this in a stable release put this behind an
experimental flag such that by default the old behavior is unmodified.
This flag is unstable and likely will go away.

TODO: If this should be upstreamed it needs to be clarified when the old
behavior in xenbus_frontend_dev_resume is needed (save/restore, I guess)
and the new behavior adapted accordingly.
---
 drivers/xen/manage.c                       | 14 ++++++++++----
 drivers/xen/xenbus/xenbus_probe_frontend.c |  5 +++++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index e20c40a62e64..dec7b7d544c9 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -47,6 +47,9 @@ struct suspend_info {
 
 static RAW_NOTIFIER_HEAD(xen_resume_notifier);
 
+bool __read_mostly xen_use_suspend;
+core_param(qubes_exp_pm_use_suspend, xen_use_suspend, bool, 0);
+
 void xen_resume_notifier_register(struct notifier_block *nb)
 {
 	raw_notifier_chain_register(&xen_resume_notifier, nb);
@@ -114,7 +117,10 @@ static void do_suspend(void)
 		goto out_thaw;
 	}
 
-	err = dpm_suspend_start(PMSG_FREEZE);
+	pr_info("Using %s for sleep/wakeup\n",
+		xen_use_suspend ? "suspend/resume" :"freeze/restore/thaw");
+
+	err = dpm_suspend_start(xen_use_suspend ? PMSG_SUSPEND : PMSG_FREEZE);
 	if (err) {
 		pr_err("%s: dpm_suspend_start %d\n", __func__, err);
 		goto out_resume_end;
@@ -123,7 +129,7 @@ static void do_suspend(void)
 	printk(KERN_DEBUG "suspending xenstore...\n");
 	xs_suspend();
 
-	err = dpm_suspend_end(PMSG_FREEZE);
+	err = dpm_suspend_end(xen_use_suspend ? PMSG_SUSPEND : PMSG_FREEZE);
 	if (err) {
 		pr_err("dpm_suspend_end failed: %d\n", err);
 		si.cancelled = 0;
@@ -144,7 +150,7 @@ static void do_suspend(void)
 
 	xen_arch_resume();
 
-	dpm_resume_start(si.cancelled ? PMSG_THAW : PMSG_RESTORE);
+	dpm_resume_start(xen_use_suspend ? PMSG_RESUME : (si.cancelled ? PMSG_THAW : PMSG_RESTORE));
 
 	if (err) {
 		pr_err("failed to start xen_suspend: %d\n", err);
@@ -158,7 +164,7 @@ static void do_suspend(void)
 		xs_suspend_cancel();
 
 out_resume_end:
-	dpm_resume_end(si.cancelled ? PMSG_THAW : PMSG_RESTORE);
+	dpm_resume_end(xen_use_suspend ? PMSG_RESUME : (si.cancelled ? PMSG_THAW : PMSG_RESTORE));
 
 out_thaw:
 	thaw_processes();
diff --git a/drivers/xen/xenbus/xenbus_probe_frontend.c b/drivers/xen/xenbus/xenbus_probe_frontend.c
index f04707d1f667..d9273b9f35a5 100644
--- a/drivers/xen/xenbus/xenbus_probe_frontend.c
+++ b/drivers/xen/xenbus/xenbus_probe_frontend.c
@@ -98,8 +98,13 @@ static void xenbus_frontend_delayed_restore(struct work_struct *w)
 	xenbus_dev_restore(&xdev->dev);
 }
 
+extern bool __read_mostly xen_use_suspend;
+
 static int xenbus_frontend_dev_restore(struct device *dev)
 {
+	if (xen_use_suspend)
+		return xenbus_dev_thaw(dev);
+
 	/*
 	 * If xenstored is running in this domain, we cannot access the backend
 	 * state at the moment, so we need to defer xenbus_dev_resume
-- 
2.52.0