linux-kernel - [PATCH 1/2] xenbus: Use .freeze/.thaw to handle xenbus devices

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Message-ID: <20251119224731.61497-2-jason.andryuk@amd.com>
Date: Wed, 19 Nov 2025 17:47:29 -0500
From: Jason Andryuk <jason.andryuk@....com>
To: Juergen Gross <jgross@...e.com>, Stefano Stabellini
	<sstabellini@...nel.org>, Oleksandr Tyshchenko
	<oleksandr_tyshchenko@...m.com>
CC: Yann Sionneau <yann.sionneau@...es.tech>, Jason Andryuk
	<jason.andryuk@....com>, <xen-devel@...ts.xenproject.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] xenbus: Use .freeze/.thaw to handle xenbus devices

The goal is to fix s2idle and S3 for Xen PV devices.  A domain resuming
from s3 or s2idle disconnects its PV devices during resume.  The
backends are not expecting this and do not reconnect.

b3e96c0c7562 ("xen: use freeze/restore/thaw PM events for suspend/
resume/chkpt") changed xen_suspend()/do_suspend() from
PMSG_SUSPEND/PMSG_RESUME to PMSG_FREEZE/PMSG_THAW/PMSG_RESTORE, but the
suspend/resume callbacks remained.

.freeze/restore are used with hiberation where Linux restarts in a new
place in the future.  .suspend/resume are useful for runtime power
management for the duration of a boot.

The current behavior of the callbacks works for an xl save/restore or
live migration where the domain is restored/migrated to a new location
and connecting to a not-already-connected backend.

Change xenbus_pm_ops to use .freeze/thaw/restore and drop the
.suspend/resume hook.  This matches the use in drivers/xen/manage.c for
save/restore and live migration.  With .suspend/resume empty, PV devices
are left connected during s2idle and s3, so PV devices are not changed
and work after resume.

Signed-off-by: Jason Andryuk <jason.andryuk@....com>
---
 drivers/xen/xenbus/xenbus_probe_frontend.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_probe_frontend.c b/drivers/xen/xenbus/xenbus_probe_frontend.c
index 6d1819269cbe..199917b6f77c 100644
--- a/drivers/xen/xenbus/xenbus_probe_frontend.c
+++ b/drivers/xen/xenbus/xenbus_probe_frontend.c
@@ -148,11 +148,9 @@ static void xenbus_frontend_dev_shutdown(struct device *_dev)
 }

 static const struct dev_pm_ops xenbus_pm_ops = {
-	.suspend	= xenbus_dev_suspend,
-	.resume		= xenbus_frontend_dev_resume,
 	.freeze		= xenbus_dev_suspend,
 	.thaw		= xenbus_dev_cancel,
-	.restore	= xenbus_dev_resume,
+	.restore	= xenbus_frontend_dev_resume,
 };

 static struct xen_bus_type xenbus_frontend = {
-- 
2.34.1