[v2,18/38] x86/paravirt: Pass sched_clock save/restore helpers during registration

Commit Message

Sean Christopherson Feb. 27, 2025, 2:18 a.m. UTC

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.

Signed-off-by: Sean Christopherson <[e-mail]>
---
 arch/x86/include/asm/paravirt.h    | 8 +++++---
 arch/x86/kernel/cpu/vmware.c       | 7 ++-----
 arch/x86/kernel/kvmclock.c         | 5 ++---
 arch/x86/kernel/paravirt.c         | 5 ++++-
 arch/x86/xen/time.c                | 5 ++---
 drivers/clocksource/hyperv_timer.c | 6 ++----
 6 files changed, 17 insertions(+), 19 deletions(-)

Patch

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index cfceabd5f7e1..dc26a3c26527 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -28,11 +28,13 @@  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), 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);
 }
 
 static __always_inline u64 paravirt_sched_clock(void)
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index d6eadb5b37fd..399cf3286a60 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -344,11 +344,8 @@  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 = NULL;
-		x86_platform.restore_sched_clock_state = NULL;
-	}
+	if (vmw_sched_clock)
+		paravirt_set_sched_clock(vmware_sched_clock, NULL, NULL);
 
 	if (vmware_is_stealclock_available()) {
 		has_steal_clock = true;
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index c78db52ae399..1ad3878cc1d9 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -136,7 +136,8 @@  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);
@@ -343,8 +344,6 @@  void __init kvmclock_init(void)
 #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/paravirt.c b/arch/x86/kernel/paravirt.c
index 55c819673a9d..9673cd3a3f0a 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -86,12 +86,15 @@  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), 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;
 }
 
 /* These are in entry.S */
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 51eba986cd18..3179f850352d 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -564,13 +564,12 @@  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 = NULL;
-	x86_platform.restore_sched_clock_state = NULL;
+	paravirt_set_sched_clock(xen_sched_clock, NULL, NULL);
 
 	tsc_register_calibration_routines(xen_tsc_khz, NULL);
 	x86_platform.get_wallclock = xen_get_wallclock;
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 4a21874e91b9..1c4ed9995cb2 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -550,10 +550,8 @@  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) {}