From: David Woodhouse dwmw@amazon.co.uk
This was introduced in commit 0061d53daf26 ("KVM: x86: limit difference between kvmclock updates") to reduce cross-vCPU differences which arose because the KVM clock was based on CLOCK_MONOTONIC and thus subject to NTP frequency corrections.
However, commit 53fafdbb8b21 ("KVM: x86: switch KVMCLOCK base to monotonic raw clock") switched to using CLOCK_MONOTONIC_RAW as the basis for the KVM clock, avoiding the NTP frequency skew altogether.
So remove KVM_REQ_GLOBAL_CLOCK_UPDATE. In kvm_write_system_time(), all that's needed is a single KVM_REQ_CLOCK_UPDATE for the vCPU whose KVM clock is being configured.
Signed-off-by: David Woodhouse dwmw@amazon.co.uk --- arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/x86.c | 57 ++------------------------------- 2 files changed, 4 insertions(+), 55 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 8440c4081727..cfac72b4aa64 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -98,7 +98,7 @@ KVM_ARCH_REQ_FLAGS(14, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) #define KVM_REQ_SCAN_IOAPIC \ KVM_ARCH_REQ_FLAGS(15, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) -#define KVM_REQ_GLOBAL_CLOCK_UPDATE KVM_ARCH_REQ(16) +/* KVM_ARCH_REQ(16) is available to be reused */ #define KVM_REQ_APIC_PAGE_RELOAD \ KVM_ARCH_REQ_FLAGS(17, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) #define KVM_REQ_HV_CRASH KVM_ARCH_REQ(18) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 4ec4eb850c5b..f870e29d2558 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2354,13 +2354,13 @@ static void kvm_write_system_time(struct kvm_vcpu *vcpu, gpa_t system_time, }
vcpu->arch.time = system_time; - kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu);
/* we verify if the enable bit is set... */ - if (system_time & 1) + if (system_time & 1) { kvm_gpc_activate(&vcpu->arch.pv_time, system_time & ~1ULL, sizeof(struct pvclock_vcpu_time_info)); - else + kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu); + } else kvm_gpc_deactivate(&vcpu->arch.pv_time);
return; @@ -3391,46 +3391,6 @@ uint64_t kvm_get_wall_clock_epoch(struct kvm *kvm) return ktime_get_real_ns() - get_kvmclock_ns(kvm); }
-/* - * kvmclock updates which are isolated to a given vcpu, such as - * vcpu->cpu migration, should not allow system_timestamp from - * the rest of the vcpus to remain static. Otherwise ntp frequency - * correction applies to one vcpu's system_timestamp but not - * the others. - * - * So in those cases, request a kvmclock update for all vcpus. - * We need to rate-limit these requests though, as they can - * considerably slow guests that have a large number of vcpus. - * The time for a remote vcpu to update its kvmclock is bound - * by the delay we use to rate-limit the updates. - */ - -#define KVMCLOCK_UPDATE_DELAY msecs_to_jiffies(100) - -static void kvmclock_update_fn(struct work_struct *work) -{ - unsigned long i; - struct delayed_work *dwork = to_delayed_work(work); - struct kvm_arch *ka = container_of(dwork, struct kvm_arch, - kvmclock_update_work); - struct kvm *kvm = container_of(ka, struct kvm, arch); - struct kvm_vcpu *vcpu; - - kvm_for_each_vcpu(i, vcpu, kvm) { - kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu); - kvm_vcpu_kick(vcpu); - } -} - -static void kvm_gen_kvmclock_update(struct kvm_vcpu *v) -{ - struct kvm *kvm = v->kvm; - - kvm_make_request(KVM_REQ_CLOCK_UPDATE, v); - schedule_delayed_work(&kvm->arch.kvmclock_update_work, - KVMCLOCK_UPDATE_DELAY); -} - /* These helpers are safe iff @msr is known to be an MCx bank MSR. */ static bool is_mci_control_msr(u32 msr) { @@ -5018,12 +4978,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) if (kvm_lapic_hv_timer_in_use(vcpu)) kvm_lapic_restart_hv_timer(vcpu);
- /* - * On a host with synchronized TSC, there is no need to update - * kvmclock on vcpu->cpu migration - */ - if (!vcpu->kvm->arch.use_master_clock || vcpu->cpu == -1) - kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu); if (vcpu->cpu != cpu) kvm_make_request(KVM_REQ_MIGRATE_TIMER, vcpu); vcpu->cpu = cpu; @@ -10961,8 +10915,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) __kvm_migrate_timers(vcpu); if (kvm_check_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu)) kvm_update_masterclock(vcpu->kvm); - if (kvm_check_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu)) - kvm_gen_kvmclock_update(vcpu); if (kvm_check_request(KVM_REQ_CLOCK_UPDATE, vcpu)) { r = kvm_guest_time_update(vcpu); if (unlikely(r)) @@ -12780,8 +12732,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) kvm->arch.hv_root_tdp = INVALID_PAGE; #endif
- INIT_DELAYED_WORK(&kvm->arch.kvmclock_update_work, kvmclock_update_fn); - kvm_apicv_init(kvm); kvm_hv_init_vm(kvm); kvm_xen_init_vm(kvm); @@ -12820,7 +12770,6 @@ static void kvm_unload_vcpu_mmus(struct kvm *kvm)
void kvm_arch_sync_events(struct kvm *kvm) { - cancel_delayed_work_sync(&kvm->arch.kvmclock_update_work); kvm_free_pit(kvm); }