linux-kernel - [PATCH RFC] misc/pvpanic: add support for normal shutdowns

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Message-Id: <20231104-pvpanic-shutdown-v1-1-5ee7c9b3e301@weissschuh.net>
Date:   Sat, 04 Nov 2023 12:29:30 +0100
From:   Thomas Weißschuh <linux@...ssschuh.net>
To:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, Zhangjin Wu <falcon@...ylab.org>,
        Willy Tarreau <w@....eu>, Yuan Tan <tanyuan@...ylab.org>,
        Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH RFC] misc/pvpanic: add support for normal shutdowns

Shutdown requests are normally hardware dependent.
By extending pvpanic to also handle shutdown requests, guests can
submit such requests with an easily implementable and cross-platform
mechanism.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
The corresponding patch to qemu has also been submitted[0].
General discussions about the feature should happen on the other thread.

[0] https://lore.kernel.org/qemu-devel/20231104-pvpanic-shutdown-v1-0-02353157891b@t-8ch.de/
---
 drivers/misc/pvpanic/pvpanic.c | 19 +++++++++++++++++--
 include/uapi/misc/pvpanic.h    |  1 +
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/pvpanic/pvpanic.c b/drivers/misc/pvpanic/pvpanic.c
index 305b367e0ce3..d7d807f5e47a 100644
--- a/drivers/misc/pvpanic/pvpanic.c
+++ b/drivers/misc/pvpanic/pvpanic.c
@@ -15,6 +15,7 @@
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/panic_notifier.h>
+#include <linux/reboot.h>
 #include <linux/types.h>
 #include <linux/cdev.h>
 #include <linux/list.h>
@@ -74,6 +75,13 @@ static struct notifier_block pvpanic_panic_nb = {
 	.priority = INT_MAX,
 };
 
+static int pvpanic_sys_off(struct sys_off_data *data)
+{
+	pvpanic_send_event(PVPANIC_SHUTDOWN);
+
+	return NOTIFY_DONE;
+}
+
 static void pvpanic_remove(void *param)
 {
 	struct pvpanic_instance *pi_cur, *pi_next;
@@ -152,7 +160,7 @@ int devm_pvpanic_probe(struct device *dev, void __iomem *base)
 		return -ENOMEM;
 
 	pi->base = base;
-	pi->capability = PVPANIC_PANICKED | PVPANIC_CRASH_LOADED;
+	pi->capability = PVPANIC_PANICKED | PVPANIC_CRASH_LOADED | PVPANIC_SHUTDOWN;
 
 	/* initlize capability by RDPT */
 	pi->capability &= ioread8(base);
@@ -168,12 +176,18 @@ int devm_pvpanic_probe(struct device *dev, void __iomem *base)
 }
 EXPORT_SYMBOL_GPL(devm_pvpanic_probe);
 
+static struct sys_off_handler *sys_off_handler;
+
 static int pvpanic_init(void)
 {
 	INIT_LIST_HEAD(&pvpanic_list);
 	spin_lock_init(&pvpanic_lock);
 
 	atomic_notifier_chain_register(&panic_notifier_list, &pvpanic_panic_nb);
+	sys_off_handler = register_sys_off_handler(SYS_OFF_MODE_POWER_OFF, SYS_OFF_PRIO_DEFAULT,
+						   pvpanic_sys_off, NULL);
+	if (IS_ERR(sys_off_handler))
+		sys_off_handler = NULL;
 
 	return 0;
 }
@@ -182,6 +196,7 @@ module_init(pvpanic_init);
 static void pvpanic_exit(void)
 {
 	atomic_notifier_chain_unregister(&panic_notifier_list, &pvpanic_panic_nb);
-
+	if (sys_off_handler)
+		unregister_sys_off_handler(sys_off_handler);
 }
 module_exit(pvpanic_exit);
diff --git a/include/uapi/misc/pvpanic.h b/include/uapi/misc/pvpanic.h
index 54b7485390d3..82fc618bfbcf 100644
--- a/include/uapi/misc/pvpanic.h
+++ b/include/uapi/misc/pvpanic.h
@@ -5,5 +5,6 @@
 
 #define PVPANIC_PANICKED	(1 << 0)
 #define PVPANIC_CRASH_LOADED	(1 << 1)
+#define PVPANIC_SHUTDOWN	(1 << 2)
 
 #endif /* __PVPANIC_H__ */

---
base-commit: 90b0c2b2edd1adff742c621e246562fbefa11b70
change-id: 20231104-pvpanic-shutdown-5fa38a879ad1

Best regards,
-- 
Thomas Weißschuh <linux@...ssschuh.net>