[PATCH v5 31/51] x86/paravirt: Move handling of unstable PV clocks into paravirt_set_sched_clock()
From: Sean Christopherson <seanjc@google.com>
Date: 2026-07-01 19:33:06
Also in:
kvm, linux-coco, linux-doc, linux-hyperv, lkml, xen-devel
Subsystem:
kvm paravirt (kvm/paravirt), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Move the handling of unstable PV clocks, of which kvmclock is the only example, into paravirt_set_sched_clock(). This will allow modifying paravirt_set_sched_clock() to keep using the TSC for sched_clock in certain scenarios without unintentionally marking the TSC-based clock as unstable. No functional change intended. Reviewed-by: David Woodhouse <redacted> Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/include/asm/timer.h | 7 ++++++- arch/x86/kernel/kvmclock.c | 5 +---- arch/x86/kernel/tsc.c | 5 ++++- 3 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/timer.h b/arch/x86/include/asm/timer.h
index c71b466d6ace..fe41d40a9ae6 100644
--- a/arch/x86/include/asm/timer.h
+++ b/arch/x86/include/asm/timer.h@@ -14,7 +14,12 @@ extern int no_timer_check; extern bool using_native_sched_clock(void); #ifdef CONFIG_PARAVIRT -void paravirt_set_sched_clock(u64 (*func)(void)); +void __paravirt_set_sched_clock(u64 (*func)(void), bool stable); + +static inline void paravirt_set_sched_clock(u64 (*func)(void)) +{ + __paravirt_set_sched_clock(func, true); +} #endif /*
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index a3ec298d56d7..4bc0495f1f9e 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c@@ -12,7 +12,6 @@ #include <linux/hardirq.h> #include <linux/cpuhotplug.h> #include <linux/sched.h> -#include <linux/sched/clock.h> #include <linux/mm.h> #include <linux/slab.h> #include <linux/set_memory.h>
@@ -115,10 +114,8 @@ static noinstr u64 kvm_sched_clock_read(void) static inline void kvm_sched_clock_init(bool stable) { - if (!stable) - clear_sched_clock_stable(); kvm_sched_clock_offset = kvm_clock_read(); - paravirt_set_sched_clock(kvm_sched_clock_read); + __paravirt_set_sched_clock(kvm_sched_clock_read, stable); pr_info("kvm-clock: using sched offset of %llu cycles", kvm_sched_clock_offset);
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 375b0279df66..a762cb5cec0f 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c@@ -280,8 +280,11 @@ bool using_native_sched_clock(void) return static_call_query(pv_sched_clock) == native_sched_clock; } -void paravirt_set_sched_clock(u64 (*func)(void)) +void __paravirt_set_sched_clock(u64 (*func)(void), bool stable) { + if (!stable) + clear_sched_clock_stable(); + static_call_update(pv_sched_clock, func); } #else
--
2.55.0.rc0.799.gd6f94ed593-goog