diff options
| author | Marcelo Tosatti <mtosatti@redhat.com> | 2008-06-11 19:52:53 -0300 |
|---|---|---|
| committer | Avi Kivity <avi@qumranet.com> | 2008-07-20 12:42:32 +0300 |
| commit | 622395a9e63bf87a16faecf555ed02375cbae5b7 (patch) | |
| tree | c4a8082660a4e4bf8f687a33921d292ae35f6394 | |
| parent | 7f39f8ac177db258200053074aa7a3d98656b1cf (diff) | |
KVM: only abort guest entry if timer count goes from 0->1
Only abort guest entry if the timer count went from 0->1, since for 1->2
or larger the bit will either be set already or a timer irq will have
been injected.
Using atomic_inc_and_test() for it also introduces an SMP barrier
to the LAPIC version (thought it was unecessary because of timer
migration, but guest can be scheduled to a different pCPU between exit
and kvm_vcpu_block(), so there is the possibility for a race).
Noticed by Avi.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
| -rw-r--r-- | arch/x86/kvm/i8254.c | 11 | ||||
| -rw-r--r-- | arch/x86/kvm/lapic.c | 4 |
2 files changed, 6 insertions, 9 deletions
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c index 9e3391e9a1b..c0f7872a912 100644 --- a/arch/x86/kvm/i8254.c +++ b/arch/x86/kvm/i8254.c @@ -198,14 +198,11 @@ static int __pit_timer_fn(struct kvm_kpit_state *ps) struct kvm_vcpu *vcpu0 = ps->pit->kvm->vcpus[0]; struct kvm_kpit_timer *pt = &ps->pit_timer; - atomic_inc(&pt->pending); - smp_mb__after_atomic_inc(); - if (vcpu0) { + if (!atomic_inc_and_test(&pt->pending)) 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); - } + if (vcpu0 && 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 180ba7316da..73f43de69f6 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -945,8 +945,8 @@ static int __apic_timer_fn(struct kvm_lapic *apic) int result = 0; wait_queue_head_t *q = &apic->vcpu->wq; - atomic_inc(&apic->timer.pending); - set_bit(KVM_REQ_PENDING_TIMER, &apic->vcpu->requests); + if(!atomic_inc_and_test(&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); |