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Date: Mon, 21 Apr 2008 13:29:37 +0300
From: Avi Kivity <avi@...ranet.com>
To: kvm-devel@...ts.sourceforge.net
Cc: linux-kernel@...r.kernel.org, Marcelo Tosatti <mtosatti@...hat.com>
Subject: [PATCH 11/31] KVM: hlt emulation should take in-kernel APIC/PIT timers into account
From: Marcelo Tosatti <mtosatti@...hat.com>
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@...hat.com>
Signed-off-by: Avi Kivity <avi@...ranet.com>
---
arch/ia64/kvm/kvm-ia64.c | 5 +++++
arch/s390/kvm/interrupt.c | 5 +++++
arch/x86/kvm/i8254.c | 11 +++++++++++
arch/x86/kvm/irq.c | 15 +++++++++++++++
arch/x86/kvm/irq.h | 3 +++
arch/x86/kvm/lapic.c | 10 ++++++++++
include/linux/kvm_host.h | 1 +
virt/kvm/kvm_main.c | 1 +
8 files changed, 51 insertions(+), 0 deletions(-)
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 @@ int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu)
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 @@ int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu)
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 06a241a..abb4b16 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -199,6 +199,7 @@ int __pit_timer_fn(struct kvm_kpit_state *ps)
struct kvm_kpit_timer *pt = &ps->pit_timer;
atomic_inc(&pt->pending);
+ smp_mb__after_atomic_inc();
if (vcpu0 && waitqueue_active(&vcpu0->wq)) {
vcpu0->arch.mp_state = VCPU_MP_STATE_RUNNABLE;
wake_up_interruptible(&vcpu0->wq);
@@ -210,6 +211,16 @@ int __pit_timer_fn(struct kvm_kpit_state *ps)
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_pending_timer_irqs(struct kvm_vcpu *vcpu);
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 @@ static int __apic_timer_fn(struct kvm_lapic *apic)
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 @@ void kvm_arch_destroy_vm(struct kvm *kvm);
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 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
* 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);
--
1.5.5
--
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