On Tue, 2022-03-08 at 17:33 +0100, Paolo Bonzini wrote:
>
> Queued, thanks.
Thanks. I've literally just a couple of minutes ago finished diagnosing
a sporadic live migration / live update bug which seems to happen
because adding an hrtimer in the past *sometimes* seems not to work,
although it always worked in my dev testing.
Incremental diff to the 'oneshot timers' patch looks like the first
hunk of this. I'm also pondering the second hunk which actively
*cancels* the pending timer on serialization.
Do you want a repost, or a proper incremental patch on top of kvm/queue
when it becomes visible?
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index a044cedca73f..9e1a8fd0c9c5 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -163,17 +163,19 @@ void __kvm_migrate_xen_timer(struct kvm_vcpu *vcpu)
hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED);
}
-static void kvm_xen_start_timer(struct kvm_vcpu *vcpu, u64 guest_abs, u64 delta_ns)
+static void kvm_xen_start_timer(struct kvm_vcpu *vcpu, u64 guest_abs, s64 delta_ns)
{
- ktime_t ktime_now;
-
atomic_set(&vcpu->arch.xen.timer_pending, 0);
vcpu->arch.xen.timer_expires = guest_abs;
- ktime_now = ktime_get();
- hrtimer_start(&vcpu->arch.xen.timer,
- ktime_add_ns(ktime_now, delta_ns),
- HRTIMER_MODE_ABS_PINNED);
+ if (delta_ns < 0) {
+ atomic_inc(&vcpu->arch.xen.timer_pending);
+ } else {
+ ktime_t ktime_now = ktime_get();
+ hrtimer_start(&vcpu->arch.xen.timer,
+ ktime_add_ns(ktime_now, delta_ns),
+ HRTIMER_MODE_ABS_PINNED);
+ }
}
static void kvm_xen_stop_timer(struct kvm_vcpu *vcpu)
@@ -837,7 +839,10 @@ int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
data->u.timer.port = vcpu->arch.xen.timer_virq;
data->u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
- data->u.timer.expires_ns = vcpu->arch.xen.timer_expires;
+ if (hrtimer_cancel(&vcpu->arch.xen.timer))
+ data->u.timer.expires_ns = vcpu->arch.xen.timer_expires;
+ else
+ data->u.timer.expires_ns = 0;
r = 0;
break;
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