KVM: close timer injection race window in __vcpu_run
If a timer fires after kvm_inject_pending_timer_irqs() but before local_irq_disable() the code will enter guest mode and only inject such timer interrupt the next time an unrelated event causes an exit. It would be simpler if the timer->pending irq conversion could be done with IRQ's disabled, so that the above problem cannot happen. For now introduce a new vcpu requests bit to cancel guest entry. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
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@ -200,10 +200,13 @@ int __pit_timer_fn(struct kvm_kpit_state *ps)
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atomic_inc(&pt->pending);
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smp_mb__after_atomic_inc();
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if (vcpu0 && waitqueue_active(&vcpu0->wq)) {
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if (vcpu0) {
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set_bit(KVM_REQ_PENDING_TIMER, &vcpu0->requests);
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if (waitqueue_active(&vcpu0->wq)) {
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vcpu0->arch.mp_state = KVM_MP_STATE_RUNNABLE;
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wake_up_interruptible(&vcpu0->wq);
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}
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}
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pt->timer.expires = ktime_add_ns(pt->timer.expires, pt->period);
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pt->scheduled = ktime_to_ns(pt->timer.expires);
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@ -940,6 +940,7 @@ static int __apic_timer_fn(struct kvm_lapic *apic)
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wait_queue_head_t *q = &apic->vcpu->wq;
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atomic_inc(&apic->timer.pending);
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set_bit(KVM_REQ_PENDING_TIMER, &apic->vcpu->requests);
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if (waitqueue_active(q)) {
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apic->vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
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wake_up_interruptible(q);
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@ -2774,6 +2774,7 @@ again:
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}
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}
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clear_bit(KVM_REQ_PENDING_TIMER, &vcpu->requests);
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kvm_inject_pending_timer_irqs(vcpu);
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preempt_disable();
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@ -33,6 +33,7 @@
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#define KVM_REQ_REPORT_TPR_ACCESS 2
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#define KVM_REQ_MMU_RELOAD 3
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#define KVM_REQ_TRIPLE_FAULT 4
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#define KVM_REQ_PENDING_TIMER 5
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struct kvm_vcpu;
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extern struct kmem_cache *kvm_vcpu_cache;
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