Revert "x86: kvm: introduce periodic global clock updates"

This reverts commit 332967a.

Commit 332967a ("x86: kvm: introduce periodic global clock
updates") introduced a 300s interval work to sync ntp corrections
across all vcpus.

Since commit 53fafdb ("KVM: x86: switch KVMCLOCK base to
monotonic raw clock"), kvmclock switched to mono raw clock,
we can no longer take ntp into consideration.

Signed-off-by: Lei Chen <lei.chen@smartx.com>
Link: https://patch.msgid.link/20250819152027.1687487-2-lei.chen@smartx.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: Lei Chen

arch/x86/include/asm/kvm_host.h

@@ -1457,7 +1457,6 @@ struct kvm_arch {
 	u64 master_kernel_ns;
 	u64 master_cycle_now;
 	struct delayed_work kvmclock_update_work;
-	struct delayed_work kvmclock_sync_work;
 
 #ifdef CONFIG_KVM_HYPERV
 	struct kvm_hv hyperv;

arch/x86/kvm/x86.c

@@ -159,9 +159,6 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(report_ignored_msrs);
 unsigned int min_timer_period_us = 200;
 module_param(min_timer_period_us, uint, 0644);
 
-static bool __read_mostly kvmclock_periodic_sync = true;
-module_param(kvmclock_periodic_sync, bool, 0444);
-
 /* tsc tolerance in parts per million - default to 1/2 of the NTP threshold */
 static u32 __read_mostly tsc_tolerance_ppm = 250;
 module_param(tsc_tolerance_ppm, uint, 0644);
@@ -3558,20 +3555,6 @@ static void kvm_gen_kvmclock_update(struct kvm_vcpu *v)
 					KVMCLOCK_UPDATE_DELAY);
 }
 
-#define KVMCLOCK_SYNC_PERIOD (300 * HZ)
-
-static void kvmclock_sync_fn(struct work_struct *work)
-{
-	struct delayed_work *dwork = to_delayed_work(work);
-	struct kvm_arch *ka = container_of(dwork, struct kvm_arch,
-					   kvmclock_sync_work);
-	struct kvm *kvm = container_of(ka, struct kvm, arch);
-
-	schedule_delayed_work(&kvm->arch.kvmclock_update_work, 0);
-	schedule_delayed_work(&kvm->arch.kvmclock_sync_work,
-					KVMCLOCK_SYNC_PERIOD);
-}
-
 /* These helpers are safe iff @msr is known to be an MCx bank MSR. */
 static bool is_mci_control_msr(u32 msr)
 {
@@ -12757,8 +12740,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 
 void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
 {
-	struct kvm *kvm = vcpu->kvm;
-
 	if (mutex_lock_killable(&vcpu->mutex))
 		return;
 	vcpu_load(vcpu);
@@ -12769,10 +12750,6 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
 	vcpu->arch.msr_kvm_poll_control = 1;
 
 	mutex_unlock(&vcpu->mutex);
-
-	if (kvmclock_periodic_sync && vcpu->vcpu_idx == 0)
-		schedule_delayed_work(&kvm->arch.kvmclock_sync_work,
-						KVMCLOCK_SYNC_PERIOD);
 }
 
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
@@ -13187,7 +13164,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 #endif
 
 	INIT_DELAYED_WORK(&kvm->arch.kvmclock_update_work, kvmclock_update_fn);
-	INIT_DELAYED_WORK(&kvm->arch.kvmclock_sync_work, kvmclock_sync_fn);
 
 	kvm_apicv_init(kvm);
 	kvm_hv_init_vm(kvm);
@@ -13295,7 +13271,6 @@ void kvm_arch_pre_destroy_vm(struct kvm *kvm)
 	 * is unsafe, i.e. will lead to use-after-free.  The PIT also needs to
 	 * be stopped before IRQ routing is freed.
 	 */
-	cancel_delayed_work_sync(&kvm->arch.kvmclock_sync_work);
 	cancel_delayed_work_sync(&kvm->arch.kvmclock_update_work);
 
 #ifdef CONFIG_KVM_IOAPIC