diff options
Diffstat (limited to 'arch/x86/kvm/lapic.c')
| -rw-r--r-- | arch/x86/kvm/lapic.c | 35 |
1 files changed, 18 insertions, 17 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 8675458c2205..87b0fcc23ef8 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -65,8 +65,11 @@ #define APIC_BROADCAST 0xFF #define X2APIC_BROADCAST 0xFFFFFFFFul -#define LAPIC_TIMER_ADVANCE_ADJUST_DONE 100 -#define LAPIC_TIMER_ADVANCE_ADJUST_INIT 1000 +static bool lapic_timer_advance_dynamic __read_mostly; +#define LAPIC_TIMER_ADVANCE_ADJUST_MIN 100 /* clock cycles */ +#define LAPIC_TIMER_ADVANCE_ADJUST_MAX 10000 /* clock cycles */ +#define LAPIC_TIMER_ADVANCE_NS_INIT 1000 +#define LAPIC_TIMER_ADVANCE_NS_MAX 5000 /* step-by-step approximation to mitigate fluctuation */ #define LAPIC_TIMER_ADVANCE_ADJUST_STEP 8 @@ -1485,26 +1488,25 @@ static inline void adjust_lapic_timer_advance(struct kvm_vcpu *vcpu, u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns; u64 ns; + /* Do not adjust for tiny fluctuations or large random spikes. */ + if (abs(advance_expire_delta) > LAPIC_TIMER_ADVANCE_ADJUST_MAX || + abs(advance_expire_delta) < LAPIC_TIMER_ADVANCE_ADJUST_MIN) + return; + /* too early */ if (advance_expire_delta < 0) { ns = -advance_expire_delta * 1000000ULL; do_div(ns, vcpu->arch.virtual_tsc_khz); - timer_advance_ns -= min((u32)ns, - timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP); + timer_advance_ns -= ns/LAPIC_TIMER_ADVANCE_ADJUST_STEP; } else { /* too late */ ns = advance_expire_delta * 1000000ULL; do_div(ns, vcpu->arch.virtual_tsc_khz); - timer_advance_ns += min((u32)ns, - timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP); + timer_advance_ns += ns/LAPIC_TIMER_ADVANCE_ADJUST_STEP; } - if (abs(advance_expire_delta) < LAPIC_TIMER_ADVANCE_ADJUST_DONE) - apic->lapic_timer.timer_advance_adjust_done = true; - if (unlikely(timer_advance_ns > 5000)) { - timer_advance_ns = LAPIC_TIMER_ADVANCE_ADJUST_INIT; - apic->lapic_timer.timer_advance_adjust_done = false; - } + if (unlikely(timer_advance_ns > LAPIC_TIMER_ADVANCE_NS_MAX)) + timer_advance_ns = LAPIC_TIMER_ADVANCE_NS_INIT; apic->lapic_timer.timer_advance_ns = timer_advance_ns; } @@ -1524,7 +1526,7 @@ static void __kvm_wait_lapic_expire(struct kvm_vcpu *vcpu) if (guest_tsc < tsc_deadline) __wait_lapic_expire(vcpu, tsc_deadline - guest_tsc); - if (unlikely(!apic->lapic_timer.timer_advance_adjust_done)) + if (lapic_timer_advance_dynamic) adjust_lapic_timer_advance(vcpu, apic->lapic_timer.advance_expire_delta); } @@ -2301,14 +2303,13 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns) HRTIMER_MODE_ABS_HARD); apic->lapic_timer.timer.function = apic_timer_fn; if (timer_advance_ns == -1) { - apic->lapic_timer.timer_advance_ns = LAPIC_TIMER_ADVANCE_ADJUST_INIT; - apic->lapic_timer.timer_advance_adjust_done = false; + apic->lapic_timer.timer_advance_ns = LAPIC_TIMER_ADVANCE_NS_INIT; + lapic_timer_advance_dynamic = true; } else { apic->lapic_timer.timer_advance_ns = timer_advance_ns; - apic->lapic_timer.timer_advance_adjust_done = true; + lapic_timer_advance_dynamic = false; } - /* * APIC is created enabled. This will prevent kvm_lapic_set_base from * thinking that APIC state has changed. |