netdev - Re: [PATCH v5 3/6] timekeeping: Add clocksource to system_time

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Date:   Tue, 15 Oct 2019 18:37:39 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jianyong Wu <jianyong.wu@....com>, netdev@...r.kernel.org,
        yangbo.lu@....com, john.stultz@...aro.org, tglx@...utronix.de,
        sean.j.christopherson@...el.com, maz@...nel.org,
        richardcochran@...il.com, Mark.Rutland@....com, will@...nel.org,
        suzuki.poulose@....com
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        Steve.Capper@....com, Kaly.Xin@....com, justin.he@....com,
        nd@....com
Subject: Re: [PATCH v5 3/6] timekeeping: Add clocksource to
 system_time_snapshot

On 15/10/19 12:48, Jianyong Wu wrote:
> Sometimes, we need check current clocksource outside of
> timekeeping area. Add clocksource to system_time_snapshot then
> we can get clocksource as well as system time.
> 
> Signed-off-by: Jianyong Wu <jianyong.wu@....com>
> Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  include/linux/timekeeping.h | 35 ++++++++++++++++++-----------------
>  kernel/time/timekeeping.c   |  7 ++++---
>  2 files changed, 22 insertions(+), 20 deletions(-)
> 
> diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
> index a8ab0f143ac4..964c14fbbf69 100644
> --- a/include/linux/timekeeping.h
> +++ b/include/linux/timekeeping.h
> @@ -194,23 +194,6 @@ extern bool timekeeping_rtc_skipresume(void);
>  
>  extern void timekeeping_inject_sleeptime64(const struct timespec64 *delta);
>  
> -/*
> - * struct system_time_snapshot - simultaneous raw/real time capture with
> - *	counter value
> - * @cycles:	Clocksource counter value to produce the system times
> - * @real:	Realtime system time
> - * @raw:	Monotonic raw system time
> - * @clock_was_set_seq:	The sequence number of clock was set events
> - * @cs_was_changed_seq:	The sequence number of clocksource change events
> - */
> -struct system_time_snapshot {
> -	u64		cycles;
> -	ktime_t		real;
> -	ktime_t		raw;
> -	unsigned int	clock_was_set_seq;
> -	u8		cs_was_changed_seq;
> -};
> -
>  /*
>   * struct system_device_crosststamp - system/device cross-timestamp
>   *	(syncronized capture)
> @@ -236,6 +219,24 @@ struct system_counterval_t {
>  	struct clocksource	*cs;
>  };
>  
> +/*
> + * struct system_time_snapshot - simultaneous raw/real time capture with
> + *	counter value
> + * @sc:		Contains clocksource and clocksource counter value to produce
> + * 	the system times
> + * @real:	Realtime system time
> + * @raw:	Monotonic raw system time
> + * @clock_was_set_seq:	The sequence number of clock was set events
> + * @cs_was_changed_seq:	The sequence number of clocksource change events
> + */
> +struct system_time_snapshot {
> +	struct system_counterval_t sc;
> +	ktime_t		real;
> +	ktime_t		raw;
> +	unsigned int	clock_was_set_seq;
> +	u8		cs_was_changed_seq;
> +};
> +
>  /*
>   * Get cross timestamp between system clock and device clock
>   */
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 44b726bab4bd..66ff089605b3 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -983,7 +983,8 @@ void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
>  		nsec_raw  = timekeeping_cycles_to_ns(&tk->tkr_raw, now);
>  	} while (read_seqcount_retry(&tk_core.seq, seq));
>  
> -	systime_snapshot->cycles = now;
> +	systime_snapshot->sc.cycles = now;
> +	systime_snapshot->sc.cs = tk->tkr_mono.clock;
>  	systime_snapshot->real = ktime_add_ns(base_real, nsec_real);
>  	systime_snapshot->raw = ktime_add_ns(base_raw, nsec_raw);
>  }
> @@ -1189,12 +1190,12 @@ int get_device_system_crosststamp(int (*get_time_fn)
>  		 * clocksource change
>  		 */
>  		if (!history_begin ||
> -		    !cycle_between(history_begin->cycles,
> +		    !cycle_between(history_begin->sc.cycles,
>  				   system_counterval.cycles, cycles) ||
>  		    history_begin->cs_was_changed_seq != cs_was_changed_seq)
>  			return -EINVAL;
>  		partial_history_cycles = cycles - system_counterval.cycles;
> -		total_history_cycles = cycles - history_begin->cycles;
> +		total_history_cycles = cycles - history_begin->sc.cycles;
>  		discontinuity =
>  			history_begin->clock_was_set_seq != clock_was_set_seq;
>  
> 

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>