[PATCH 2/4] s390/irq/idle: Use stcke instead of stckf for time stamps
From: Heiko Carstens
Date: Wed May 13 2026 - 10:13:51 EST
The upcoming cpu idle time accounting rework involves comparing and
subtracting cross cpu time stamps. Time stamps created with the stckf
instruction monotonic with respect to the local cpu. For cross cpu
monotonic time stamps the slightly slower stcke instruction has to
be used [1].
Convert the idle time accounting relevant usages of stckf to stcke.
[1] Principles of Operation - Setting and Inspecting the Clock
Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
---
arch/s390/include/asm/idle.h | 3 ++-
arch/s390/include/asm/lowcore.h | 4 ++--
arch/s390/include/asm/vtime.h | 4 ++--
arch/s390/kernel/entry.S | 2 +-
arch/s390/kernel/idle.c | 4 ++--
arch/s390/kernel/irq.c | 7 ++++---
drivers/s390/cio/qdio_main.c | 2 +-
drivers/s390/cio/qdio_thinint.c | 2 +-
8 files changed, 15 insertions(+), 13 deletions(-)
diff --git a/arch/s390/include/asm/idle.h b/arch/s390/include/asm/idle.h
index e4ad09a22400..6963e92b60a1 100644
--- a/arch/s390/include/asm/idle.h
+++ b/arch/s390/include/asm/idle.h
@@ -11,14 +11,15 @@
#include <linux/percpu-defs.h>
#include <linux/types.h>
#include <linux/device.h>
+#include <asm/tod_types.h>
struct s390_idle_data {
bool idle_dyntick;
unsigned long idle_count;
unsigned long idle_time;
- unsigned long clock_idle_enter;
unsigned long timer_idle_enter;
unsigned long mt_cycles_enter[8];
+ union tod_clock clock_idle_enter;
};
DECLARE_PER_CPU(struct s390_idle_data, s390_idle);
diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h
index 50ffe75adeb4..b7720484b2f7 100644
--- a/arch/s390/include/asm/lowcore.h
+++ b/arch/s390/include/asm/lowcore.h
@@ -10,6 +10,7 @@
#define _ASM_S390_LOWCORE_H
#include <linux/types.h>
+#include <asm/tod_types.h>
#include <asm/machine.h>
#include <asm/ptrace.h>
#include <asm/ctlreg.h>
@@ -125,8 +126,7 @@ struct lowcore {
__u64 avg_steal_timer; /* 0x0300 */
__u64 last_update_timer; /* 0x0308 */
__u64 last_update_clock; /* 0x0310 */
- __u64 int_clock; /* 0x0318 */
- __u8 pad_0x0320[0x0328-0x0320]; /* 0x0320 */
+ union tod_clock int_clock; /* 0x0318 */
__u64 clock_comparator; /* 0x0328 */
__u8 pad_0x0330[0x0340-0x0330]; /* 0x0330 */
diff --git a/arch/s390/include/asm/vtime.h b/arch/s390/include/asm/vtime.h
index b1db75d14e9d..da116a93d3b6 100644
--- a/arch/s390/include/asm/vtime.h
+++ b/arch/s390/include/asm/vtime.h
@@ -48,8 +48,8 @@ static inline void update_timer_idle(void)
* The accounted CPU times will be subtracted again from steal_timer
* when accumulated steal time is calculated in do_account_vtime().
*/
- lc->steal_timer += idle->clock_idle_enter - lc->last_update_clock;
- lc->last_update_clock = lc->int_clock;
+ lc->steal_timer += idle->clock_idle_enter.tod - lc->last_update_clock;
+ lc->last_update_clock = lc->int_clock.tod;
lc->system_timer += lc->last_update_timer - idle->timer_idle_enter;
lc->last_update_timer = lc->sys_enter_timer;
}
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index bb806d1ddae0..7147f3e51ace 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -379,7 +379,7 @@ SYM_CODE_END(pgm_check_handler)
SYM_CODE_START(\name)
STMG_LC %r8,%r15,__LC_SAVE_AREA
GET_LC %r13
- stckf __LC_INT_CLOCK(%r13)
+ stcke __LC_INT_CLOCK(%r13)
stpt __LC_SYS_ENTER_TIMER(%r13)
STBEAR __LC_LAST_BREAK(%r13)
BPOFF
diff --git a/arch/s390/kernel/idle.c b/arch/s390/kernel/idle.c
index 4685d7c5bc51..36020dffb86b 100644
--- a/arch/s390/kernel/idle.c
+++ b/arch/s390/kernel/idle.c
@@ -26,7 +26,7 @@ void account_idle_time_irq(void)
struct s390_idle_data *idle = this_cpu_ptr(&s390_idle);
unsigned long idle_time;
- idle_time = get_lowcore()->int_clock - idle->clock_idle_enter;
+ idle_time = get_lowcore()->int_clock.tod - idle->clock_idle_enter.tod;
/* Account time spent with enabled wait psw loaded as idle time. */
__atomic64_add(idle_time, &idle->idle_time);
@@ -49,7 +49,7 @@ void noinstr arch_cpu_idle(void)
set_cpu_flag(CIF_ENABLED_WAIT);
if (smp_cpu_mtid)
stcctm(MT_DIAG, smp_cpu_mtid, (u64 *)&idle->mt_cycles_enter);
- idle->clock_idle_enter = get_tod_clock_fast();
+ store_tod_clock_ext(&idle->clock_idle_enter);
idle->timer_idle_enter = get_cpu_timer();
bpon();
__load_psw_mask(psw_mask);
diff --git a/arch/s390/kernel/irq.c b/arch/s390/kernel/irq.c
index d10a17e6531d..24f44f4a3aac 100644
--- a/arch/s390/kernel/irq.c
+++ b/arch/s390/kernel/irq.c
@@ -103,9 +103,10 @@ static const struct irq_class irqclass_sub_desc[] = {
static void do_IRQ(struct pt_regs *regs, int irq)
{
- if (tod_after_eq(get_lowcore()->int_clock,
- get_lowcore()->clock_comparator))
- /* Serve timer interrupts first. */
+ struct lowcore *lc = get_lowcore();
+
+ /* Serve timer interrupts first */
+ if (tod_after_eq(lc->int_clock.tod, lc->clock_comparator))
clock_comparator_work();
generic_handle_irq(irq);
}
diff --git a/drivers/s390/cio/qdio_main.c b/drivers/s390/cio/qdio_main.c
index 7e594a800525..c1e09fa34e77 100644
--- a/drivers/s390/cio/qdio_main.c
+++ b/drivers/s390/cio/qdio_main.c
@@ -695,7 +695,7 @@ static void qdio_int_handler_pci(struct qdio_irq *irq_ptr)
return;
qdio_deliver_irq(irq_ptr);
- irq_ptr->last_data_irq_time = get_lowcore()->int_clock;
+ irq_ptr->last_data_irq_time = get_lowcore()->int_clock.tod;
}
static void qdio_handle_activate_check(struct qdio_irq *irq_ptr,
diff --git a/drivers/s390/cio/qdio_thinint.c b/drivers/s390/cio/qdio_thinint.c
index 85ca8650adeb..e167aa75c3df 100644
--- a/drivers/s390/cio/qdio_thinint.c
+++ b/drivers/s390/cio/qdio_thinint.c
@@ -99,7 +99,7 @@ static inline u32 clear_shared_ind(void)
static void tiqdio_thinint_handler(struct airq_struct *airq,
struct tpi_info *tpi_info)
{
- u64 irq_time = get_lowcore()->int_clock;
+ u64 irq_time = get_lowcore()->int_clock.tod;
u32 si_used = clear_shared_ind();
struct qdio_irq *irq;
--
2.51.0