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authorMarcelo Tosatti <mtosatti@redhat.com>2008-06-06 16:37:36 -0300
committerAvi Kivity <avi@qumranet.com>2008-06-24 12:16:59 +0300
commit06e05645661211b9eaadaf6344c335d2e80f0ba2 (patch)
tree8846d2a5052aec44141e811c0a76fdb39c2e77ca
parentd4acf7e7abe45457e751525a2a4d5b693dfdd597 (diff)
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>
-rw-r--r--arch/x86/kvm/i8254.c9
-rw-r--r--arch/x86/kvm/lapic.c1
-rw-r--r--arch/x86/kvm/x86.c1
-rw-r--r--include/linux/kvm_host.h1
4 files changed, 9 insertions, 3 deletions
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index f2f5d260874e..3829aa7b663f 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -200,9 +200,12 @@ int __pit_timer_fn(struct kvm_kpit_state *ps)
atomic_inc(&pt->pending);
smp_mb__after_atomic_inc();
- if (vcpu0 && waitqueue_active(&vcpu0->wq)) {
- vcpu0->arch.mp_state = KVM_MP_STATE_RUNNABLE;
- wake_up_interruptible(&vcpu0->wq);
+ if (vcpu0) {
+ set_bit(KVM_REQ_PENDING_TIMER, &vcpu0->requests);
+ if (waitqueue_active(&vcpu0->wq)) {
+ vcpu0->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+ wake_up_interruptible(&vcpu0->wq);
+ }
}
pt->timer.expires = ktime_add_ns(pt->timer.expires, pt->period);
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index c297c50eba63..ebc03f5ae162 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -940,6 +940,7 @@ static int __apic_timer_fn(struct kvm_lapic *apic)
wait_queue_head_t *q = &apic->vcpu->wq;
atomic_inc(&apic->timer.pending);
+ set_bit(KVM_REQ_PENDING_TIMER, &apic->vcpu->requests);
if (waitqueue_active(q)) {
apic->vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
wake_up_interruptible(q);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b90744a1dc3a..b08812d6b34c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2774,6 +2774,7 @@ again:
}
}
+ clear_bit(KVM_REQ_PENDING_TIMER, &vcpu->requests);
kvm_inject_pending_timer_irqs(vcpu);
preempt_disable();
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 092b1b25291d..de9d1df4bba2 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -33,6 +33,7 @@
#define KVM_REQ_REPORT_TPR_ACCESS 2
#define KVM_REQ_MMU_RELOAD 3
#define KVM_REQ_TRIPLE_FAULT 4
+#define KVM_REQ_PENDING_TIMER 5
struct kvm_vcpu;
extern struct kmem_cache *kvm_vcpu_cache;

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