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>
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 31280df..debf582 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -952,6 +952,16 @@
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;