From 3d80840d96127401ba6aeadd813c3a15b84e70fe Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Fri, 11 Apr 2008 14:53:26 -0300 Subject: [PATCH] KVM: hlt emulation should take in-kernel APIC/PIT timers into account Timers that fire between guest hlt and vcpu_block's add_wait_queue() are ignored, possibly resulting in hangs. Also make sure that atomic_inc and waitqueue_active tests happen in the specified order, otherwise the following race is open: CPU0 CPU1 if (waitqueue_active(wq)) add_wait_queue() if (!atomic_read(pit_timer->pending)) schedule() atomic_inc(pit_timer->pending) Signed-off-by: Marcelo Tosatti Signed-off-by: Avi Kivity --- arch/ia64/kvm/kvm-ia64.c | 5 +++++ arch/s390/kvm/interrupt.c | 5 +++++ arch/x86/kvm/i8254.c | 10 ++++++++++ arch/x86/kvm/irq.c | 15 +++++++++++++++ arch/x86/kvm/irq.h | 3 +++ arch/x86/kvm/lapic.c | 10 ++++++++++ include/linux/kvm_host.h | 1 + virt/kvm/kvm_main.c | 1 + 8 files changed, 50 insertions(+) diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c index 9c56b6429cb6..ca1cfb124d4f 100644 --- a/arch/ia64/kvm/kvm-ia64.c +++ b/arch/ia64/kvm/kvm-ia64.c @@ -1778,6 +1778,11 @@ int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu) return 0; } +int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu) +{ + return 0; +} + gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn) { return gfn; diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index f62588cb75f8..fcd1ed8015c1 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -325,6 +325,11 @@ int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu) return rc; } +int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu) +{ + return 0; +} + int kvm_s390_handle_wait(struct kvm_vcpu *vcpu) { u64 now, sltime; diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c index 9f118e2f350d..ed1af80432b3 100644 --- a/arch/x86/kvm/i8254.c +++ b/arch/x86/kvm/i8254.c @@ -212,6 +212,16 @@ int __pit_timer_fn(struct kvm_kpit_state *ps) return (pt->period == 0 ? 0 : 1); } +int pit_has_pending_timer(struct kvm_vcpu *vcpu) +{ + struct kvm_pit *pit = vcpu->kvm->arch.vpit; + + if (pit && vcpu->vcpu_id == 0) + return atomic_read(&pit->pit_state.pit_timer.pending); + + return 0; +} + static enum hrtimer_restart pit_timer_fn(struct hrtimer *data) { struct kvm_kpit_state *ps; diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c index dbfe21c99c48..ce1f583459b1 100644 --- a/arch/x86/kvm/irq.c +++ b/arch/x86/kvm/irq.c @@ -25,6 +25,21 @@ #include "irq.h" #include "i8254.h" +/* + * check if there are pending timer events + * to be processed. + */ +int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu) +{ + int ret; + + ret = pit_has_pending_timer(vcpu); + ret |= apic_has_pending_timer(vcpu); + + return ret; +} +EXPORT_SYMBOL(kvm_cpu_has_pending_timer); + /* * check if there is pending interrupt without * intack. diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h index fa5ed5d59b5d..1802134b836f 100644 --- a/arch/x86/kvm/irq.h +++ b/arch/x86/kvm/irq.h @@ -85,4 +85,7 @@ void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu); void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu); void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu); +int pit_has_pending_timer(struct kvm_vcpu *vcpu); +int apic_has_pending_timer(struct kvm_vcpu *vcpu); + #endif diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 31280df7d2e3..debf58211bdd 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -952,6 +952,16 @@ static int __apic_timer_fn(struct kvm_lapic *apic) return result; } +int apic_has_pending_timer(struct kvm_vcpu *vcpu) +{ + struct kvm_lapic *lapic = vcpu->arch.apic; + + if (lapic) + return atomic_read(&lapic->timer.pending); + + return 0; +} + static int __inject_apic_timer_irq(struct kvm_lapic *apic) { int vector; diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index bd0c2d2d840f..0bc400387cae 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -269,6 +269,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm); int kvm_cpu_get_interrupt(struct kvm_vcpu *v); int kvm_cpu_has_interrupt(struct kvm_vcpu *v); +int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu); void kvm_vcpu_kick(struct kvm_vcpu *vcpu); static inline void kvm_guest_enter(void) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index d5911d9895c3..47cbc6e3fafd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -765,6 +765,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) * We will block until either an interrupt or a signal wakes us up */ while (!kvm_cpu_has_interrupt(vcpu) + && !kvm_cpu_has_pending_timer(vcpu) && !signal_pending(current) && !kvm_arch_vcpu_runnable(vcpu)) { set_current_state(TASK_INTERRUPTIBLE); -- 2.20.1