linux-kernel - [PATCH] PM: notify of PM_POST

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Message-Id: <20220301173120.297105-1-Jason@zx2c4.com>
Date:   Tue,  1 Mar 2022 18:31:20 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     rafael@...nel.org, pavel@....cz, len.brown@...el.com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH] PM: notify of PM_POST_VMFORK events from vmgenid

There's an additional virtual power state that various crypto-oriented
drivers may benefit from being notified of, such as WireGuard: right
after a virtual machine has forked. In WireGuard's case, the PM notifier
there that clears keys pre-suspend will be adjusted to also clear them
post-vmfork. This trivial commit wires up the machinery for that change,
which builds on the recently added vmgenid driver in the random.git
tree.

Cc: Rafael J. Wysocki <rafael@...nel.org>
Cc: Pavel Machek <pavel@....cz>
Cc: Len Brown <len.brown@...el.com>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 drivers/virt/vmgenid.c  | 2 ++
 include/linux/suspend.h | 4 ++++
 kernel/power/main.c     | 6 ++++++
 3 files changed, 12 insertions(+)

diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
index 0ae1a39f2e28..4bef3e8b3476 100644
--- a/drivers/virt/vmgenid.c
+++ b/drivers/virt/vmgenid.c
@@ -10,6 +10,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/acpi.h>
+#include <linux/suspend.h>
 #include <linux/random.h>
 
 ACPI_MODULE_NAME("vmgenid");
@@ -75,6 +76,7 @@ static void vmgenid_notify(struct acpi_device *device, u32 event)
 	if (!memcmp(old_id, state->this_id, sizeof(old_id)))
 		return;
 	add_vmfork_randomness(state->this_id, sizeof(state->this_id));
+	pm_notify_vmfork();
 }
 
 static const struct acpi_device_id vmgenid_ids[] = {
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 300273ff40cc..a3836473b87b 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -477,6 +477,7 @@ static inline int is_hibernate_resume_dev(dev_t dev) { return 0; }
 #define PM_POST_SUSPEND		0x0004 /* Suspend finished */
 #define PM_RESTORE_PREPARE	0x0005 /* Going to restore a saved image */
 #define PM_POST_RESTORE		0x0006 /* Restore failed */
+#define PM_POST_VMFORK		0x0007 /* Virtual machine has just forked */
 
 extern struct mutex system_transition_mutex;
 
@@ -487,6 +488,7 @@ void restore_processor_state(void);
 /* kernel/power/main.c */
 extern int register_pm_notifier(struct notifier_block *nb);
 extern int unregister_pm_notifier(struct notifier_block *nb);
+extern void pm_notify_vmfork(void);
 extern void ksys_sync_helper(void);
 
 #define pm_notifier(fn, pri) {				\
@@ -525,6 +527,8 @@ static inline int unregister_pm_notifier(struct notifier_block *nb)
 	return 0;
 }
 
+static inline void pm_notify_vmfork(void) {}
+
 static inline void ksys_sync_helper(void) {}
 
 #define pm_notifier(fn, pri)	do { (void)(fn); } while (0)
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 7e646079fbeb..a64cfb36b1b3 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -94,6 +94,12 @@ int pm_notifier_call_chain(unsigned long val)
 	return blocking_notifier_call_chain(&pm_chain_head, val, NULL);
 }
 
+void pm_notify_vmfork(void)
+{
+	pm_notifier_call_chain(PM_POST_VMFORK);
+}
+EXPORT_SYMBOL_GPL(pm_notify_vmfork);
+
 /* If set, devices may be suspended and resumed asynchronously. */
 int pm_async_enabled = 1;
 
-- 
2.35.1