linux-kernel - [PATCH 04/13] timekeeping: Add the boot clock to system time snapshot

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Message-ID: <20240911093029.3279154-5-vdonnefort@google.com>
Date: Wed, 11 Sep 2024 10:30:20 +0100
From: Vincent Donnefort <vdonnefort@...gle.com>
To: rostedt@...dmis.org, mhiramat@...nel.org, 
	linux-trace-kernel@...r.kernel.org, maz@...nel.org, oliver.upton@...ux.dev
Cc: kvmarm@...ts.linux.dev, will@...nel.org, qperret@...gle.com, 
	kernel-team@...roid.com, linux-kernel@...r.kernel.org, 
	Vincent Donnefort <vdonnefort@...gle.com>, John Stultz <jstultz@...gle.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Stephen Boyd <sboyd@...nel.org>, 
	"Christopher S. Hall" <christopher.s.hall@...el.com>, Richard Cochran <richardcochran@...il.com>, 
	Lakshmi Sowjanya D <lakshmi.sowjanya.d@...el.com>
Subject: [PATCH 04/13] timekeeping: Add the boot clock to system time snapshot

For tracing purpose, the boot clock is interesting as it doesn't stop on
suspend. Export it as part of the time snapshot. This will later allow
the hypervisor to add boot clock timestamps to its events.

Cc: John Stultz <jstultz@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Stephen Boyd <sboyd@...nel.org>
Cc: Christopher S. Hall <christopher.s.hall@...el.com>
Cc: Richard Cochran <richardcochran@...il.com>
Cc: Lakshmi Sowjanya D <lakshmi.sowjanya.d@...el.com>
Signed-off-by: Vincent Donnefort <vdonnefort@...gle.com>

diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index fc12a9ba2c88..e85c27347e44 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -275,6 +275,7 @@ struct ktime_timestamps {
  *				 counter value
  * @cycles:	Clocksource counter value to produce the system times
  * @real:	Realtime system time
+ * @boot:	Boot time
  * @raw:	Monotonic raw system time
  * @cs_id:	Clocksource ID
  * @clock_was_set_seq:	The sequence number of clock-was-set events
@@ -283,6 +284,7 @@ struct ktime_timestamps {
 struct system_time_snapshot {
 	u64			cycles;
 	ktime_t			real;
+	ktime_t			boot;
 	ktime_t			raw;
 	enum clocksource_ids	cs_id;
 	unsigned int		clock_was_set_seq;
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 5391e4167d60..db16c44dccc3 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1060,6 +1060,7 @@ void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
 	unsigned int seq;
 	ktime_t base_raw;
 	ktime_t base_real;
+	ktime_t base_boot;
 	u64 nsec_raw;
 	u64 nsec_real;
 	u64 now;
@@ -1074,6 +1075,8 @@ void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
 		systime_snapshot->clock_was_set_seq = tk->clock_was_set_seq;
 		base_real = ktime_add(tk->tkr_mono.base,
 				      tk_core.timekeeper.offs_real);
+		base_boot = ktime_add(tk->tkr_mono.base,
+				      tk_core.timekeeper.offs_boot);
 		base_raw = tk->tkr_raw.base;
 		nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, now);
 		nsec_raw  = timekeeping_cycles_to_ns(&tk->tkr_raw, now);
@@ -1081,6 +1084,7 @@ void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
 
 	systime_snapshot->cycles = now;
 	systime_snapshot->real = ktime_add_ns(base_real, nsec_real);
+	systime_snapshot->boot = ktime_add_ns(base_boot, nsec_real);
 	systime_snapshot->raw = ktime_add_ns(base_raw, nsec_raw);
 }
 EXPORT_SYMBOL_GPL(ktime_get_snapshot);
-- 
2.46.0.598.g6f2099f65c-goog