[PATCH v7 3/5] um: allow PM with suspend-to-idle

[Anton Ivanov]

On 02/12/2020 19:58, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg at intel.com>
> 
> In order to be able to experiment with suspend in UML, add the
> minimal work to be able to suspend (s2idle) an instance of UML,
> and be able to wake it back up from that state with the USR1
> signal sent to the main UML process.
> 
> Signed-off-by: Johannes Berg <johannes.berg at intel.com>
> ---
>   arch/um/Kconfig                    |  5 +++++
>   arch/um/include/shared/kern_util.h |  2 ++
>   arch/um/include/shared/os.h        |  1 +
>   arch/um/kernel/um_arch.c           | 25 +++++++++++++++++++++++++
>   arch/um/os-Linux/signal.c          | 14 +++++++++++++-
>   5 files changed, 46 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/um/Kconfig b/arch/um/Kconfig
> index 4b799fad8b48..1c57599b82fa 100644
> --- a/arch/um/Kconfig
> +++ b/arch/um/Kconfig
> @@ -192,3 +192,8 @@ config UML_TIME_TRAVEL_SUPPORT
>   endmenu
>   
>   source "arch/um/drivers/Kconfig"
> +
> +config ARCH_SUSPEND_POSSIBLE
> +	def_bool y
> +
> +source "kernel/power/Kconfig"
> diff --git a/arch/um/include/shared/kern_util.h b/arch/um/include/shared/kern_util.h
> index ccafb62e8cce..9c08e728a675 100644
> --- a/arch/um/include/shared/kern_util.h
> +++ b/arch/um/include/shared/kern_util.h
> @@ -39,6 +39,8 @@ extern int is_syscall(unsigned long addr);
>   
>   extern void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs);
>   
> +extern void uml_pm_wake(void);
> +
>   extern int start_uml(void);
>   extern void paging_init(void);
>   
> diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
> index 0f7fb8bad728..78250a05394a 100644
> --- a/arch/um/include/shared/os.h
> +++ b/arch/um/include/shared/os.h
> @@ -241,6 +241,7 @@ extern int set_signals(int enable);
>   extern int set_signals_trace(int enable);
>   extern int os_is_signal_stack(void);
>   extern void deliver_alarm(void);
> +extern void register_pm_wake_signal(void);
>   
>   /* util.c */
>   extern void stack_protections(unsigned long address);
> diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
> index 76b37297b7d4..237a8d73a096 100644
> --- a/arch/um/kernel/um_arch.c
> +++ b/arch/um/kernel/um_arch.c
> @@ -13,6 +13,7 @@
>   #include <linux/sched.h>
>   #include <linux/sched/task.h>
>   #include <linux/kmsg_dump.h>
> +#include <linux/suspend.h>
>   
>   #include <asm/processor.h>
>   #include <asm/sections.h>
> @@ -377,3 +378,27 @@ void *text_poke(void *addr, const void *opcode, size_t len)
>   void text_poke_sync(void)
>   {
>   }
> +
> +#ifdef CONFIG_PM_SLEEP
> +void uml_pm_wake(void)
> +{
> +	pm_system_wakeup();
> +}
> +
> +static int init_pm_wake_signal(void)
> +{
> +	/*
> +	 * In external time-travel mode we can't use signals to wake up
> +	 * since that would mess with the scheduling. We'll have to do
> +	 * some additional work to support wakeup on virtio devices or
> +	 * similar, perhaps implementing a fake RTC controller that can
> +	 * trigger wakeup (and request the appropriate scheduling from
> +	 * the external scheduler when going to suspend.)
> +	 */
> +	if (time_travel_mode != TT_MODE_EXTERNAL)
> +		register_pm_wake_signal();
> +	return 0;
> +}
> +
> +late_initcall(init_pm_wake_signal);
> +#endif
> diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
> index b58bc68cbe64..0a2ea84033b4 100644
> --- a/arch/um/os-Linux/signal.c
> +++ b/arch/um/os-Linux/signal.c
> @@ -136,6 +136,16 @@ void set_sigstack(void *sig_stack, int size)
>   		panic("enabling signal stack failed, errno = %d\n", errno);
>   }
>   
> +static void sigusr1_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
> +{
> +	uml_pm_wake();
> +}
> +
> +void register_pm_wake_signal(void)
> +{
> +	set_handler(SIGUSR1);
> +}
> +
>   static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
>   	[SIGSEGV] = sig_handler,
>   	[SIGBUS] = sig_handler,
> @@ -145,7 +155,9 @@ static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
>   
>   	[SIGIO] = sig_handler,
>   	[SIGWINCH] = sig_handler,
> -	[SIGALRM] = timer_alarm_handler
> +	[SIGALRM] = timer_alarm_handler,
> +
> +	[SIGUSR1] = sigusr1_handler,
>   };
>   
>   static void hard_handler(int sig, siginfo_t *si, void *p)
> 

Acked-By: Anton Ivanov <anton.ivanov at cambridgegreys.com>

-- 
Anton R. Ivanov
https://www.kot-begemot.co.uk/