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 <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
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@ -1778,6 +1778,11 @@ int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu)
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return 0;
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}
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int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
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{
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return 0;
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}
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gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
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{
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return gfn;
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@ -325,6 +325,11 @@ int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu)
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return rc;
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}
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int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
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{
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return 0;
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}
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int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
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{
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u64 now, sltime;
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@ -212,6 +212,16 @@ int __pit_timer_fn(struct kvm_kpit_state *ps)
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return (pt->period == 0 ? 0 : 1);
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}
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int pit_has_pending_timer(struct kvm_vcpu *vcpu)
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{
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struct kvm_pit *pit = vcpu->kvm->arch.vpit;
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if (pit && vcpu->vcpu_id == 0)
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return atomic_read(&pit->pit_state.pit_timer.pending);
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return 0;
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}
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static enum hrtimer_restart pit_timer_fn(struct hrtimer *data)
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{
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struct kvm_kpit_state *ps;
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@ -25,6 +25,21 @@
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#include "irq.h"
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#include "i8254.h"
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/*
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* check if there are pending timer events
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* to be processed.
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*/
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int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
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{
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int ret;
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ret = pit_has_pending_timer(vcpu);
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ret |= apic_has_pending_timer(vcpu);
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return ret;
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}
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EXPORT_SYMBOL(kvm_cpu_has_pending_timer);
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/*
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* check if there is pending interrupt without
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* intack.
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@ -85,4 +85,7 @@ void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu);
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void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu);
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void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu);
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int pit_has_pending_timer(struct kvm_vcpu *vcpu);
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int apic_has_pending_timer(struct kvm_vcpu *vcpu);
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#endif
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@ -952,6 +952,16 @@ static int __apic_timer_fn(struct kvm_lapic *apic)
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return result;
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}
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int apic_has_pending_timer(struct kvm_vcpu *vcpu)
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{
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struct kvm_lapic *lapic = vcpu->arch.apic;
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if (lapic)
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return atomic_read(&lapic->timer.pending);
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return 0;
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}
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static int __inject_apic_timer_irq(struct kvm_lapic *apic)
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{
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int vector;
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@ -269,6 +269,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm);
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int kvm_cpu_get_interrupt(struct kvm_vcpu *v);
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int kvm_cpu_has_interrupt(struct kvm_vcpu *v);
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int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu);
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void kvm_vcpu_kick(struct kvm_vcpu *vcpu);
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static inline void kvm_guest_enter(void)
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@ -765,6 +765,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
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* We will block until either an interrupt or a signal wakes us up
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*/
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while (!kvm_cpu_has_interrupt(vcpu)
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&& !kvm_cpu_has_pending_timer(vcpu)
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&& !signal_pending(current)
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&& !kvm_arch_vcpu_runnable(vcpu)) {
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set_current_state(TASK_INTERRUPTIBLE);
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