diff options
| -rw-r--r-- | include/linux/clocksource.h | 24 | ||||
| -rw-r--r-- | include/linux/timekeeping.h | 6 | ||||
| -rw-r--r-- | kernel/time/timekeeping.c | 21 |
3 files changed, 50 insertions, 1 deletions
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 7c38190b10bf..6d9ddf1587a2 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -32,6 +32,21 @@ struct module; #include <vdso/clocksource.h> /** + * struct clocksource_hw_snapshot - Snapshot for the underlying hardware counter of derived + * clocksources like kvmclock or Hyper-V scaled TSC + * @hw_cycles: The hardware counter value + * @hw_csid: Clocksource ID of the hardware counter + * + * Such clocksources must implement the read_snapshot() callback and fill in the + * hardware counter value, the clocksource ID of the hardware counter and derive + * the actual clocksource cycles from @hw_cycles to provide an atomic snapshot + */ +struct clocksource_hw_snapshot { + u64 hw_cycles; + enum clocksource_ids hw_csid; +}; + +/** * struct clocksource - hardware abstraction for a free running counter * Provides mostly state-free accessors to the underlying hardware. * This is the structure used for system time. @@ -72,6 +87,14 @@ struct module; * @flags: Flags describing special properties * @base: Hardware abstraction for clock on which a clocksource * is based + * @read_snapshot: Extended @read() function for clocksources such as + * kvmclock or the Hyper-V scaled TSC where the actual + * clocksource value for timekeeping is calculated from an + * underlying hardware counter. Returns the timekeeping + * relevant cycle value and stores the raw value of the + * underlying counter from which it was calculated + * including the clocksource ID of that counter in the + * clocksource hardware snapshot. * @enable: Optional function to enable the clocksource * @disable: Optional function to disable the clocksource * @suspend: Optional suspend function for the clocksource @@ -113,6 +136,7 @@ struct clocksource { unsigned long flags; struct clocksource_base *base; + u64 (*read_snapshot)(struct clocksource *cs, struct clocksource_hw_snapshot *chs); int (*enable)(struct clocksource *cs); void (*disable)(struct clocksource *cs); void (*suspend)(struct clocksource *cs); diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h index 7f03e1cefcf6..984a866d293b 100644 --- a/include/linux/timekeeping.h +++ b/include/linux/timekeeping.h @@ -279,18 +279,24 @@ static inline bool ktime_get_aux_ts64(clockid_t id, struct timespec64 *kt) { ret * struct system_time_snapshot - Simultaneous time capture of CLOCK_MONOTONIC_RAW, * a selected CLOCK_* and the clocksource counter value * @cycles: Clocksource counter value to produce the system times + * @hw_cycles: For derived clocksources, the hardware counter value from + * which @cycles was derived * @systime: The system time of the selected CLOCK ID * @monoraw: Monotonic raw system time * @cs_id: Clocksource ID + * @hw_csid: Clocksource ID of the underlying hardware counter for derived + * clocksources which implement the read_snapshot() callback. * @clock_was_set_seq: The sequence number of clock-was-set events * @cs_was_changed_seq: The sequence number of clocksource change events * @valid: True if the snapshot is valid */ struct system_time_snapshot { u64 cycles; + u64 hw_cycles; ktime_t systime; ktime_t monoraw; enum clocksource_ids cs_id; + enum clocksource_ids hw_csid; unsigned int clock_was_set_seq; u8 cs_was_changed_seq; u8 valid; diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 65d870c2d40d..0d5b67f609bb 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -320,6 +320,7 @@ static __always_inline u64 tk_clock_read(const struct tk_read_base *tkr) return clock->read(clock); } + static inline void clocksource_disable_inline_read(void) { } static inline void clocksource_enable_inline_read(void) { } #endif @@ -1187,6 +1188,18 @@ noinstr time64_t __ktime_get_real_seconds(void) return tk->xtime_sec; } +static inline u64 tk_clock_read_snapshot(const struct tk_read_base *tkr, + struct clocksource_hw_snapshot *chs) +{ + struct clocksource *clock = READ_ONCE(tkr->clock); + + if (unlikely(clock->read_snapshot)) + return clock->read_snapshot(clock, chs); + + return clock->read(clock); +} + + /** * ktime_get_snapshot_id - Simultaneously snapshot a given clock ID with * CLOCK_MONOTONIC_RAW and the underlying @@ -1237,14 +1250,20 @@ void ktime_get_snapshot_id(clockid_t clock_id, struct system_time_snapshot *syst tk = &tkd->timekeeper; do { + struct clocksource_hw_snapshot chs = { }; + seq = read_seqcount_begin(&tkd->seq); /* Aux clocks can be invalid */ if (!tk->clock_valid) return; - now = tk_clock_read(&tk->tkr_mono); + now = tk_clock_read_snapshot(&tk->tkr_mono, &chs); systime_snapshot->cs_id = tk->tkr_mono.clock->id; + + systime_snapshot->hw_cycles = chs.hw_cycles; + systime_snapshot->hw_csid = chs.hw_csid; + systime_snapshot->cs_was_changed_seq = tk->cs_was_changed_seq; systime_snapshot->clock_was_set_seq = tk->clock_was_set_seq; |