[PATCH v5 36/51] x86/paravirt: Pass sched_clock save/restore helpers during registration
From: Sean Christopherson <seanjc@google.com>
Date: 2026-07-01 19:33:12
Also in:
kvm, linux-coco, linux-hyperv, lkml, virtualization, xen-devel
Subsystem:
clocksource, clockevent drivers, hyper-v/azure core and drivers, kvm paravirt (kvm/paravirt), the rest, vmware hypervisor interface, x86 architecture (32-bit and 64-bit), xen hypervisor x86 · Maintainers:
Daniel Lezcano, Thomas Gleixner, "K. Y. Srinivasan", Haiyang Zhang, Wei Liu, Dexuan Cui, Long Li, Paolo Bonzini, Linus Torvalds, Ajay Kaher, Alexey Makhalov, Ingo Molnar, Borislav Petkov, Dave Hansen, Juergen Gross
Pass in a PV clock's save/restore helpers when configuring sched_clock instead of relying on each PV clock to manually set the save/restore hooks. In addition to bringing sanity to the code, this will allow gracefully "rejecting" a PV sched_clock, e.g. when running as a CoCo guest that has access to a "secure" TSC. No functional change intended. Reviewed-by: David Woodhouse <redacted> Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/include/asm/timer.h | 9 ++++++--- arch/x86/kernel/cpu/vmware.c | 8 +++----- arch/x86/kernel/kvmclock.c | 6 +++--- arch/x86/kernel/tsc.c | 5 ++++- arch/x86/xen/time.c | 5 ++--- drivers/clocksource/hyperv_timer.c | 6 ++---- 6 files changed, 20 insertions(+), 19 deletions(-)
diff --git a/arch/x86/include/asm/timer.h b/arch/x86/include/asm/timer.h
index fe41d40a9ae6..e97cd1ae03d1 100644
--- a/arch/x86/include/asm/timer.h
+++ b/arch/x86/include/asm/timer.h@@ -14,11 +14,14 @@ extern int no_timer_check; extern bool using_native_sched_clock(void); #ifdef CONFIG_PARAVIRT -void __paravirt_set_sched_clock(u64 (*func)(void), bool stable); +void __paravirt_set_sched_clock(u64 (*func)(void), bool stable, + void (*save)(void), void (*restore)(void)); -static inline void paravirt_set_sched_clock(u64 (*func)(void)) +static inline void paravirt_set_sched_clock(u64 (*func)(void), + void (*save)(void), + void (*restore)(void)) { - __paravirt_set_sched_clock(func, true); + __paravirt_set_sched_clock(func, true, save, restore); } #endif
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 5c1ccaf4a25e..232255279a6e 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c@@ -347,11 +347,9 @@ static void __init vmware_paravirt_ops_setup(void) vmware_cyc2ns_setup(); - if (vmw_sched_clock) { - paravirt_set_sched_clock(vmware_sched_clock); - x86_platform.save_sched_clock_state = x86_init_noop; - x86_platform.restore_sched_clock_state = x86_init_noop; - } + if (vmw_sched_clock) + paravirt_set_sched_clock(vmware_sched_clock, + x86_init_noop, x86_init_noop); if (vmware_is_stealclock_available()) { has_steal_clock = true;
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 07e875738c39..5b9955343199 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c@@ -158,7 +158,9 @@ static void kvm_restore_sched_clock_state(void) static inline void kvm_sched_clock_init(bool stable) { kvm_sched_clock_offset = kvm_clock_read(); - __paravirt_set_sched_clock(kvm_sched_clock_read, stable); + __paravirt_set_sched_clock(kvm_sched_clock_read, stable, + kvm_save_sched_clock_state, + kvm_restore_sched_clock_state); pr_info("kvm-clock: using sched offset of %llu cycles", kvm_sched_clock_offset);
@@ -367,8 +369,6 @@ void __init kvmclock_init(bool prefer_tsc) #ifdef CONFIG_SMP x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock; #endif - x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; - x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; kvm_get_preset_lpj(); /*
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 7473dcab4775..83353d643150 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c@@ -280,12 +280,15 @@ bool using_native_sched_clock(void) return static_call_query(pv_sched_clock) == native_sched_clock; } -void __paravirt_set_sched_clock(u64 (*func)(void), bool stable) +void __paravirt_set_sched_clock(u64 (*func)(void), bool stable, + void (*save)(void), void (*restore)(void)) { if (!stable) clear_sched_clock_stable(); static_call_update(pv_sched_clock, func); + x86_platform.save_sched_clock_state = save; + x86_platform.restore_sched_clock_state = restore; } #else u64 sched_clock_noinstr(void) __attribute__((alias("native_sched_clock")));
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 477441752f40..8cd8bfaf1320 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c@@ -566,13 +566,12 @@ static void __init xen_init_time_common(void) { xen_sched_clock_offset = xen_clocksource_read(); static_call_update(pv_steal_clock, xen_steal_clock); - paravirt_set_sched_clock(xen_sched_clock); + /* * Xen has paravirtualized suspend/resume and so doesn't use the common * x86 sched_clock save/restore hooks. */ - x86_platform.save_sched_clock_state = x86_init_noop; - x86_platform.restore_sched_clock_state = x86_init_noop; + paravirt_set_sched_clock(xen_sched_clock, x86_init_noop, x86_init_noop); x86_init.hyper.get_tsc_khz = xen_tsc_khz; x86_platform.get_wallclock = xen_get_wallclock;
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 220668207d19..8ee7a9de0f4f 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c@@ -570,10 +570,8 @@ static void hv_restore_sched_clock_state(void) static __always_inline void hv_setup_sched_clock(void *sched_clock) { /* We're on x86/x64 *and* using PV ops */ - paravirt_set_sched_clock(sched_clock); - - x86_platform.save_sched_clock_state = hv_save_sched_clock_state; - x86_platform.restore_sched_clock_state = hv_restore_sched_clock_state; + paravirt_set_sched_clock(sched_clock, hv_save_sched_clock_state, + hv_restore_sched_clock_state); } #else /* !CONFIG_GENERIC_SCHED_CLOCK && !CONFIG_PARAVIRT */ static __always_inline void hv_setup_sched_clock(void *sched_clock) {}
--
2.55.0.rc0.799.gd6f94ed593-goog