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

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Date:   Tue, 1 Mar 2022 18:36:43 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] PM: notify of PM_POST_VMFORK events from vmgenid

On Tue, Mar 1, 2022 at 6:31 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
>
> 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.

Well, what does power management have to do with WireGuard'?

> 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();

IMV, this is completely confusing.

>  }
>
>  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
>