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/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index 9c56b64..ca1cfb1 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -1778,6 +1778,11 @@
return 0;
}
+int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
+{
+ return 0;
+}
+
gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
{
return gfn;
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index f62588c..fcd1ed8 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -325,6 +325,11 @@
return rc;
}
+int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
+{
+ return 0;
+}
+
int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
{
u64 now, sltime;
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 9f118e2..ed1af80 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -212,6 +212,16 @@
return (pt->period == 0 ? 0 : 1);
}
+int pit_has_pending_timer(struct kvm_vcpu *vcpu)
+{
+ struct kvm_pit *pit = vcpu->kvm->arch.vpit;
+
+ if (pit && vcpu->vcpu_id == 0)
+ return atomic_read(&pit->pit_state.pit_timer.pending);
+
+ return 0;
+}
+
static enum hrtimer_restart pit_timer_fn(struct hrtimer *data)
{
struct kvm_kpit_state *ps;
diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index dbfe21c..ce1f583 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -26,6 +26,21 @@
#include "i8254.h"
/*
+ * check if there are pending timer events
+ * to be processed.
+ */
+int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
+{
+ int ret;
+
+ ret = pit_has_pending_timer(vcpu);
+ ret |= apic_has_pending_timer(vcpu);
+
+ return ret;
+}
+EXPORT_SYMBOL(kvm_cpu_has_pending_timer);
+
+/*
* check if there is pending interrupt without
* intack.
*/
diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
index fa5ed5d..1802134 100644
--- a/arch/x86/kvm/irq.h
+++ b/arch/x86/kvm/irq.h
@@ -85,4 +85,7 @@
void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu);
void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu);
+int pit_has_pending_timer(struct kvm_vcpu *vcpu);
+int apic_has_pending_timer(struct kvm_vcpu *vcpu);
+
#endif
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;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index bd0c2d2..0bc4003 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -269,6 +269,7 @@
int kvm_cpu_get_interrupt(struct kvm_vcpu *v);
int kvm_cpu_has_interrupt(struct kvm_vcpu *v);
+int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu);
void kvm_vcpu_kick(struct kvm_vcpu *vcpu);
static inline void kvm_guest_enter(void)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d5911d9..47cbc6e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -765,6 +765,7 @@
* We will block until either an interrupt or a signal wakes us up
*/
while (!kvm_cpu_has_interrupt(vcpu)
+ && !kvm_cpu_has_pending_timer(vcpu)
&& !signal_pending(current)
&& !kvm_arch_vcpu_runnable(vcpu)) {
set_current_state(TASK_INTERRUPTIBLE);
