[PATCH 06/14] sched: move clock related paravirt code to kernel/sched

Juergen Gross
2025-09-11T06:35:20Z

Paravirt clock related functions are available in multiple archs.

In order to share the common parts, move the common static keys
to kernel/sched/ and remove them from the arch specific files.

Make a common paravirt_steal_clock() implementation available in
kernel/sched/cputime.c, guarding it with a new config option
CONFIG_HAVE_PV_STEAL_CLOCK_GEN, which can be selectd by an arch
in case it wants to use that common variant.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
arch/Kconfig | 3 +++
arch/arm/include/asm/paravirt.h | 4 ----
arch/arm/kernel/paravirt.c | 3 ---
arch/arm64/include/asm/paravirt.h | 4 ----
arch/arm64/kernel/paravirt.c | 4 +---
arch/loongarch/include/asm/paravirt.h | 3 ---
arch/loongarch/kernel/paravirt.c | 3 +--
arch/powerpc/include/asm/paravirt.h | 3 ---
arch/powerpc/platforms/pseries/setup.c | 4 +---
arch/riscv/include/asm/paravirt.h | 4 ----
arch/riscv/kernel/paravirt.c | 4 +---
arch/x86/include/asm/paravirt.h | 4 ----
arch/x86/kernel/cpu/vmware.c | 1 +
arch/x86/kernel/kvm.c | 1 +
arch/x86/kernel/paravirt.c | 3 ---
drivers/xen/time.c | 1 +
include/linux/sched/cputime.h | 18 ++++++++++++++++++
kernel/sched/core.c | 5 +++++
kernel/sched/cputime.c | 13 +++++++++++++
kernel/sched/sched.h | 2 +-
20 files changed, 47 insertions(+), 40 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index d1b4ffd6e085..7921be052472 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1003,6 +1003,9 @@ config HAVE_IRQ_TIME_ACCOUNTING
Archs need to ensure they use a high enough resolution clock to
support irq time accounting and then call enable_sched_clock_irqtime().

+config HAVE_PV_STEAL_CLOCK_GEN
+ bool
+
config HAVE_MOVE_PUD
bool
help
diff --git a/arch/arm/include/asm/paravirt.h b/arch/arm/include/asm/paravirt.h
index 95d5b0d625cd..69da4bdcf856 100644
--- a/arch/arm/include/asm/paravirt.h
+++ b/arch/arm/include/asm/paravirt.h
@@ -5,10 +5,6 @@
#ifdef CONFIG_PARAVIRT
#include <linux/static_call_types.h>

-struct static_key;
-extern struct static_key paravirt_steal_enabled;
-extern struct static_key paravirt_steal_rq_enabled;
-
u64 dummy_steal_clock(int cpu);

DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
diff --git a/arch/arm/kernel/paravirt.c b/arch/arm/kernel/paravirt.c
index 7dd9806369fb..3895a5578852 100644
--- a/arch/arm/kernel/paravirt.c
+++ b/arch/arm/kernel/paravirt.c
@@ -12,9 +12,6 @@
#include <linux/static_call.h>
#include <asm/paravirt.h>

-struct static_key paravirt_steal_enabled;
-struct static_key paravirt_steal_rq_enabled;
-
static u64 native_steal_clock(int cpu)
{
return 0;
diff --git a/arch/arm64/include/asm/paravirt.h b/arch/arm64/include/asm/paravirt.h
index 9aa193e0e8f2..c9f7590baacb 100644
--- a/arch/arm64/include/asm/paravirt.h
+++ b/arch/arm64/include/asm/paravirt.h
@@ -5,10 +5,6 @@
#ifdef CONFIG_PARAVIRT
#include <linux/static_call_types.h>

-struct static_key;
-extern struct static_key paravirt_steal_enabled;
-extern struct static_key paravirt_steal_rq_enabled;
-
u64 dummy_steal_clock(int cpu);

DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c
index aa718d6a9274..943b60ce12f4 100644
--- a/arch/arm64/kernel/paravirt.c
+++ b/arch/arm64/kernel/paravirt.c
@@ -19,14 +19,12 @@
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/static_call.h>
+#include <linux/sched/cputime.h>

#include <asm/paravirt.h>
#include <asm/pvclock-abi.h>
#include <asm/smp_plat.h>

-struct static_key paravirt_steal_enabled;
-struct static_key paravirt_steal_rq_enabled;
-
static u64 native_steal_clock(int cpu)
{
return 0;
diff --git a/arch/loongarch/include/asm/paravirt.h b/arch/loongarch/include/asm/paravirt.h
index 3f4323603e6a..d219ea0d98ac 100644
--- a/arch/loongarch/include/asm/paravirt.h
+++ b/arch/loongarch/include/asm/paravirt.h
@@ -5,9 +5,6 @@
#ifdef CONFIG_PARAVIRT

#include <linux/static_call_types.h>
-struct static_key;
-extern struct static_key paravirt_steal_enabled;
-extern struct static_key paravirt_steal_rq_enabled;

u64 dummy_steal_clock(int cpu);
DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
index b1b51f920b23..8caaa94fed1a 100644
--- a/arch/loongarch/kernel/paravirt.c
+++ b/arch/loongarch/kernel/paravirt.c
@@ -6,11 +6,10 @@
#include <linux/kvm_para.h>
#include <linux/reboot.h>
#include <linux/static_call.h>
+#include <linux/sched/cputime.h>
#include <asm/paravirt.h>

static int has_steal_clock;
-struct static_key paravirt_steal_enabled;
-struct static_key paravirt_steal_rq_enabled;
static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
DEFINE_STATIC_KEY_FALSE(virt_spin_lock_key);

diff --git a/arch/powerpc/include/asm/paravirt.h b/arch/powerpc/include/asm/paravirt.h
index b78b82d66057..92343a23ad15 100644
--- a/arch/powerpc/include/asm/paravirt.h
+++ b/arch/powerpc/include/asm/paravirt.h
@@ -23,9 +23,6 @@ static inline bool is_shared_processor(void)
}

#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
-extern struct static_key paravirt_steal_enabled;
-extern struct static_key paravirt_steal_rq_enabled;
-
u64 pseries_paravirt_steal_clock(int cpu);

static inline u64 paravirt_steal_clock(int cpu)
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index b10a25325238..50b26ed8432d 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -42,6 +42,7 @@
#include <linux/memblock.h>
#include <linux/swiotlb.h>
#include <linux/seq_buf.h>
+#include <linux/sched/cputime.h>

#include <asm/mmu.h>
#include <asm/processor.h>
@@ -83,9 +84,6 @@ DEFINE_STATIC_KEY_FALSE(shared_processor);
EXPORT_SYMBOL(shared_processor);

#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
-struct static_key paravirt_steal_enabled;
-struct static_key paravirt_steal_rq_enabled;
-
static bool steal_acc = true;
static int __init parse_no_stealacc(char *arg)
{
diff --git a/arch/riscv/include/asm/paravirt.h b/arch/riscv/include/asm/paravirt.h
index c0abde70fc2c..17e5e39c72c0 100644
--- a/arch/riscv/include/asm/paravirt.h
+++ b/arch/riscv/include/asm/paravirt.h
@@ -5,10 +5,6 @@
#ifdef CONFIG_PARAVIRT
#include <linux/static_call_types.h>

-struct static_key;
-extern struct static_key paravirt_steal_enabled;
-extern struct static_key paravirt_steal_rq_enabled;
-
u64 dummy_steal_clock(int cpu);

DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
diff --git a/arch/riscv/kernel/paravirt.c b/arch/riscv/kernel/paravirt.c
index fa6b0339a65d..d3c334f16172 100644
--- a/arch/riscv/kernel/paravirt.c
+++ b/arch/riscv/kernel/paravirt.c
@@ -16,15 +16,13 @@
#include <linux/printk.h>
#include <linux/static_call.h>
#include <linux/types.h>
+#include <linux/sched/cputime.h>

#include <asm/barrier.h>
#include <asm/page.h>
#include <asm/paravirt.h>
#include <asm/sbi.h>

-struct static_key paravirt_steal_enabled;
-struct static_key paravirt_steal_rq_enabled;
-
static u64 native_steal_clock(int cpu)
{
return 0;
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 0d1e611f619c..491cb7e037bf 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -34,10 +34,6 @@ static __always_inline u64 paravirt_sched_clock(void)
return static_call(pv_sched_clock)();
}

-struct static_key;
-extern struct static_key paravirt_steal_enabled;
-extern struct static_key paravirt_steal_rq_enabled;
-
__visible void __native_queued_spin_unlock(struct qspinlock *lock);
bool pv_is_native_spin_unlock(void);
__visible bool __native_vcpu_is_preempted(long cpu);
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index cb3f900c46fc..a3e6936839b1 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -29,6 +29,7 @@
#include <linux/efi.h>
#include <linux/reboot.h>
#include <linux/static_call.h>
+#include <linux/sched/cputime.h>
#include <asm/div64.h>
#include <asm/x86_init.h>
#include <asm/hypervisor.h>
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 8ae750cde0c6..a23211eaaeed 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -29,6 +29,7 @@
#include <linux/syscore_ops.h>
#include <linux/cc_platform.h>
#include <linux/efi.h>
+#include <linux/sched/cputime.h>
#include <asm/timer.h>
#include <asm/cpu.h>
#include <asm/traps.h>
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index ab3e172dcc69..a3ba4747be1c 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -60,9 +60,6 @@ void __init native_pv_lock_init(void)
static_branch_enable(&virt_spin_lock_key);
}

-struct static_key paravirt_steal_enabled;
-struct static_key paravirt_steal_rq_enabled;
-
static u64 native_steal_clock(int cpu)
{
return 0;
diff --git a/drivers/xen/time.c b/drivers/xen/time.c
index 5683383d2305..d360ded2ef39 100644
--- a/drivers/xen/time.c
+++ b/drivers/xen/time.c
@@ -8,6 +8,7 @@
#include <linux/gfp.h>
#include <linux/slab.h>
#include <linux/static_call.h>
+#include <linux/sched/cputime.h>

#include <asm/paravirt.h>
#include <asm/xen/hypervisor.h>
diff --git a/include/linux/sched/cputime.h b/include/linux/sched/cputime.h
index 5f8fd5b24a2e..e90efaf6d26e 100644
--- a/include/linux/sched/cputime.h
+++ b/include/linux/sched/cputime.h
@@ -2,6 +2,7 @@
#ifndef _LINUX_SCHED_CPUTIME_H
#define _LINUX_SCHED_CPUTIME_H

+#include <linux/static_call_types.h>
#include <linux/sched/signal.h>

/*
@@ -180,4 +181,21 @@ static inline void prev_cputime_init(struct prev_cputime *prev)
extern unsigned long long
task_sched_runtime(struct task_struct *task);

+#ifdef CONFIG_PARAVIRT
+struct static_key;
+extern struct static_key paravirt_steal_enabled;
+extern struct static_key paravirt_steal_rq_enabled;
+
+#ifdef CONFIG_HAVE_PV_STEAL_CLOCK_GEN
+u64 dummy_steal_clock(int cpu);
+
+DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
+
+static inline u64 paravirt_steal_clock(int cpu)
+{
+ return static_call(pv_steal_clock)(cpu);
+}
+#endif
+#endif
+
#endif /* _LINUX_SCHED_CPUTIME_H */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index be00629f0ba4..e723226e4e11 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -767,6 +767,11 @@ struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
* RQ-clock updating methods:
*/

+/* Use CONFIG_PARAVIRT as this will avoid more #ifdef in arch code. */
+#ifdef CONFIG_PARAVIRT
+struct static_key paravirt_steal_rq_enabled;
+#endif
+
static void update_rq_clock_task(struct rq *rq, s64 delta)
{
/*
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 7097de2c8cda..ed8f71e08047 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -251,6 +251,19 @@ void __account_forceidle_time(struct task_struct *p, u64 delta)
* ticks are not redelivered later. Due to that, this function may on
* occasion account more time than the calling functions think elapsed.
*/
+#ifdef CONFIG_PARAVIRT
+struct static_key paravirt_steal_enabled;
+
+#ifdef CONFIG_HAVE_PV_STEAL_CLOCK_GEN
+static u64 native_steal_clock(int cpu)
+{
+ return 0;
+}
+
+DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
+#endif
+#endif
+
static __always_inline u64 steal_account_process_time(u64 maxtime)
{
#ifdef CONFIG_PARAVIRT
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 6442441b46d7..fdf3021bdf7d 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -82,7 +82,7 @@ struct rt_rq;
struct sched_group;
struct cpuidle_state;

-#ifdef CONFIG_PARAVIRT
+#if defined(CONFIG_PARAVIRT) && !defined(CONFIG_HAVE_PV_STEAL_CLOCK_GEN)
# include <asm/paravirt.h>
#endif

--
2.51.0