diff options
Diffstat (limited to 'arch/x86/kvm/lapic.c')
| -rw-r--r-- | arch/x86/kvm/lapic.c | 42 |
1 files changed, 23 insertions, 19 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index cf37586f0466..acd7d48100a1 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -59,7 +59,17 @@ #define MAX_APIC_VECTOR 256 #define APIC_VECTORS_PER_REG 32 -static bool lapic_timer_advance_dynamic __read_mostly; +/* + * Enable local APIC timer advancement (tscdeadline mode only) with adaptive + * tuning. When enabled, KVM programs the host timer event to fire early, i.e. + * before the deadline expires, to account for the delay between taking the + * VM-Exit (to inject the guest event) and the subsequent VM-Enter to resume + * the guest, i.e. so that the interrupt arrives in the guest with minimal + * latency relative to the deadline programmed by the guest. + */ +static bool lapic_timer_advance __read_mostly = true; +module_param(lapic_timer_advance, bool, 0444); + #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 @@ -1854,16 +1864,14 @@ static void __kvm_wait_lapic_expire(struct kvm_vcpu *vcpu) guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc()); trace_kvm_wait_lapic_expire(vcpu->vcpu_id, guest_tsc - tsc_deadline); - if (lapic_timer_advance_dynamic) { - adjust_lapic_timer_advance(vcpu, guest_tsc - tsc_deadline); - /* - * If the timer fired early, reread the TSC to account for the - * overhead of the above adjustment to avoid waiting longer - * than is necessary. - */ - if (guest_tsc < tsc_deadline) - guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc()); - } + adjust_lapic_timer_advance(vcpu, guest_tsc - tsc_deadline); + + /* + * If the timer fired early, reread the TSC to account for the overhead + * of the above adjustment to avoid waiting longer than is necessary. + */ + if (guest_tsc < tsc_deadline) + guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc()); if (guest_tsc < tsc_deadline) __wait_lapic_expire(vcpu, tsc_deadline - guest_tsc); @@ -2776,7 +2784,8 @@ int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type) trig_mode = reg & APIC_LVT_LEVEL_TRIGGER; r = __apic_accept_irq(apic, mode, vector, 1, trig_mode, NULL); - if (r && lvt_type == APIC_LVTPC) + if (r && lvt_type == APIC_LVTPC && + guest_cpuid_is_intel_compatible(apic->vcpu)) kvm_lapic_set_reg(apic, APIC_LVTPC, reg | APIC_LVT_MASKED); return r; } @@ -2811,7 +2820,7 @@ static enum hrtimer_restart apic_timer_fn(struct hrtimer *data) return HRTIMER_NORESTART; } -int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns) +int kvm_create_lapic(struct kvm_vcpu *vcpu) { struct kvm_lapic *apic; @@ -2844,13 +2853,8 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns) hrtimer_init(&apic->lapic_timer.timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD); apic->lapic_timer.timer.function = apic_timer_fn; - if (timer_advance_ns == -1) { + if (lapic_timer_advance) 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; - lapic_timer_advance_dynamic = false; - } /* * Stuff the APIC ENABLE bit in lieu of temporarily incrementing |