[PATCH 10/16] x86/paravirt: Move handling of unstable PV clocks into paravirt_set_sched_clock()
From: Sean Christopherson <seanjc@google.com>
Date: 2025-02-01 02:17:45
Also in:
kvm, linux-coco, lkml, virtualization, xen-devel
Subsystem:
kvm paravirt (kvm/paravirt), paravirt_ops interface, the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Paolo Bonzini, Juergen Gross, 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. Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/include/asm/paravirt.h | 7 ++++++- arch/x86/kernel/kvmclock.c | 5 +---- arch/x86/kernel/paravirt.c | 6 +++++- 3 files changed, 12 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 041aff51eb50..cfceabd5f7e1 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h@@ -28,7 +28,12 @@ u64 dummy_sched_clock(void); DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock); DECLARE_STATIC_CALL(pv_sched_clock, dummy_sched_clock); -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); +} static __always_inline u64 paravirt_sched_clock(void) {
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index b41ac7f27b9f..890535ddc059 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>
@@ -93,10 +92,8 @@ 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/paravirt.c b/arch/x86/kernel/paravirt.c
index 1ccaa3397a67..55c819673a9d 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c@@ -14,6 +14,7 @@ #include <linux/highmem.h> #include <linux/kprobes.h> #include <linux/pgtable.h> +#include <linux/sched/clock.h> #include <linux/static_call.h> #include <asm/bug.h>
@@ -85,8 +86,11 @@ static u64 native_steal_clock(int cpu) DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock); DEFINE_STATIC_CALL(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); }
--
2.48.1.362.g079036d154-goog