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Date: Fri, 18 Aug 2023 03:12:55 +0200
From: Peter Hilber <peter.hilber@...nsynergy.com>
To: linux-kernel@...r.kernel.org,
kvm@...r.kernel.org,
kvmarm@...ts.linux.dev
Cc: Peter Hilber <peter.hilber@...nsynergy.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>,
Richard Cochran <richardcochran@...il.com>,
John Stultz <jstultz@...gle.com>,
Stephen Boyd <sboyd@...nel.org>,
netdev@...r.kernel.org,
Marc Zyngier <maz@...nel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Oliver Upton <oliver.upton@...ux.dev>,
James Morse <james.morse@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Zenghui Yu <yuzenghui@...wei.com>,
Sean Christopherson <seanjc@...gle.com>
Subject: [RFC PATCH 4/4] treewide: Use clocksource id for struct system_counterval_t
Use enum clocksource_ids, rather than struct clocksource *, in struct
system_counterval_t. This allows drivers to use
get_device_system_crosststamp() without referring to clocksource structs,
which are clocksource driver implementation details.
As a "treewide" change, this modifies code in timekeeping, ptp/kvm, and
x86/tsc.
So far, get_device_system_crosststamp() requires the caller to provide a
clocksource * as part of the cross-timestamp (through the
system_counterval_t * parameter in the get_time_fn() callback). But
clocksource * are not easily accessible to most code. As a workaround,
custom functions returning the clocksource * may be put into the
clocksource driver code (cf. kvm_arch_ptp_get_crosststamp() in
arm_arch_timer.c).
To avoid more interference with clocksource driver implementation details
from future code, change system_counterval_t to use enum clocksource_ids,
which serves as a unique identifier for relevant clocksources.
This change will allow the virtio_rtc driver, available as an RFC patch
series, to work without modifying the arm_arch_timer implementation.
This change should not alter any behavior. For the x86 ART related code,
.cs == NULL corresponds to system_counterval_t.cs_id == CSID_GENERIC (0).
The one drawback of this change is that clocksources now need a custom id
to work with get_device_system_crosststamp(), since they cannot be
distinguished otherwise.
Signed-off-by: Peter Hilber <peter.hilber@...nsynergy.com>
---
arch/x86/kernel/tsc.c | 6 +++---
drivers/ptp/ptp_kvm_common.c | 3 ++-
include/linux/timekeeping.h | 4 ++--
kernel/time/timekeeping.c | 3 ++-
4 files changed, 9 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index e56cc4e97d0d..eadfb819a0b5 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1313,7 +1313,7 @@ struct system_counterval_t convert_art_to_tsc(u64 art)
res += tmp + art_to_tsc_offset;
return (struct system_counterval_t) {
- .cs = have_art ? &clocksource_tsc : NULL,
+ .cs_id = have_art ? CSID_TSC : CSID_GENERIC,
.cycles = res
};
}
@@ -1335,7 +1335,7 @@ EXPORT_SYMBOL(convert_art_to_tsc);
* struct system_counterval_t - system counter value with the pointer to the
* corresponding clocksource
* @cycles: System counter value
- * @cs: Clocksource corresponding to system counter value. Used
+ * @cs_id: Clocksource corresponding to system counter value. Used
* by timekeeping code to verify comparability of two cycle
* values.
*/
@@ -1353,7 +1353,7 @@ struct system_counterval_t convert_art_ns_to_tsc(u64 art_ns)
res += tmp;
return (struct system_counterval_t) {
- .cs = have_art ? &clocksource_tsc : NULL,
+ .cs_id = have_art ? CSID_TSC : CSID_GENERIC,
.cycles = res
};
}
diff --git a/drivers/ptp/ptp_kvm_common.c b/drivers/ptp/ptp_kvm_common.c
index 2418977989be..d72e6ed71b7a 100644
--- a/drivers/ptp/ptp_kvm_common.c
+++ b/drivers/ptp/ptp_kvm_common.c
@@ -4,6 +4,7 @@
*
* Copyright (C) 2017 Red Hat Inc.
*/
+#include <linux/clocksource.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/init.h>
@@ -46,7 +47,7 @@ static int ptp_kvm_get_time_fn(ktime_t *device_time,
preempt_enable_notrace();
system_counter->cycles = cycle;
- system_counter->cs = cs;
+ system_counter->cs_id = cs->id;
*device_time = timespec64_to_ktime(tspec);
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index fe1e467ba046..2e7ae0f7f19e 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -270,12 +270,12 @@ struct system_device_crosststamp {
* struct system_counterval_t - system counter value with the pointer to the
* corresponding clocksource
* @cycles: System counter value
- * @cs: Clocksource corresponding to system counter value. Used by
+ * @cs_id: Clocksource corresponding to system counter value. Used by
* timekeeping code to verify comparibility of two cycle values
*/
struct system_counterval_t {
u64 cycles;
- struct clocksource *cs;
+ enum clocksource_ids cs_id;
};
/*
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 266d02809dbb..56428eadf4c1 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1236,7 +1236,8 @@ int get_device_system_crosststamp(int (*get_time_fn)
* system counter value is the same as the currently installed
* timekeeper clocksource
*/
- if (tk->tkr_mono.clock != system_counterval.cs)
+ if (system_counterval.cs_id == CSID_GENERIC ||
+ tk->tkr_mono.clock->id != system_counterval.cs_id)
return -ENODEV;
cycles = system_counterval.cycles;
--
2.39.2
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