lkml.org 
[lkml]   [2016]   [Jun]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
SubjectRe: [PATCH] KVM: vmx: fix underflow in TSC deadline calculation
2016-06-29 4:07 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>
>
> On 28/06/2016 20:34, yunhong jiang wrote:
>> Paolo, thanks for reply.
>>
>> Which race window you are talking about? Is it the
>> kvm_lapic_switch_to_hv_timer()? If yes, hope we will not forgot it once the
>> lapic timer is not pinned anymore in future.
>
> Yes, it's that one. This is a good point against using
> local_irq_save/restore.
>
> Paolo

How about something like below(untested, just want to know if this is
what you mean):

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index fdc05ae..adf8e32 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1361,6 +1361,33 @@ void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu)
}
EXPORT_SYMBOL_GPL(kvm_lapic_expired_hv_timer);

+static void start_hv_tscdeadline(struct kvm_lapic *apic)
+{
+ unsigned long flags;
+ u64 tscdeadline = apic->lapic_timer.tscdeadline;
+
+ local_irq_save(flags);
+ if (kvm_x86_ops->set_hv_timer(apic->vcpu, tscdeadline)) {
+ if (apic->lapic_timer.hv_timer_in_use) {
+ apic->lapic_timer.hv_timer_in_use = false;
+ kvm_x86_ops->cancel_hv_timer(apic->vcpu);
+ }
+ start_sw_tscdeadline(apic);
+ } else {
+ apic->lapic_timer.hv_timer_in_use = true;
+ hrtimer_cancel(&apic->lapic_timer.timer);
+
+ /* In case the sw timer triggered in the window */
+ if (atomic_read(&apic->lapic_timer.pending)) {
+ apic->lapic_timer.hv_timer_in_use = false;
+ kvm_x86_ops->cancel_hv_timer(apic->vcpu);
+ }
+ }
+ local_irq_restore(flags);
+ trace_kvm_hv_timer_state(apic->vcpu->vcpu_id,
+ apic->lapic_timer.hv_timer_in_use);
+}
+
void kvm_lapic_switch_to_hv_timer(struct kvm_vcpu *vcpu)
{
struct kvm_lapic *apic = vcpu->arch.apic;
@@ -1368,22 +1395,8 @@ void kvm_lapic_switch_to_hv_timer(struct kvm_vcpu *vcpu)
WARN_ON(apic->lapic_timer.hv_timer_in_use);

if (apic_lvtt_tscdeadline(apic) &&
- !atomic_read(&apic->lapic_timer.pending)) {
- u64 tscdeadline = apic->lapic_timer.tscdeadline;
-
- if (!kvm_x86_ops->set_hv_timer(vcpu, tscdeadline)) {
- apic->lapic_timer.hv_timer_in_use = true;
- hrtimer_cancel(&apic->lapic_timer.timer);
-
- /* In case the sw timer triggered in the window */
- if (atomic_read(&apic->lapic_timer.pending)) {
- apic->lapic_timer.hv_timer_in_use = false;
- kvm_x86_ops->cancel_hv_timer(apic->vcpu);
- }
- }
- trace_kvm_hv_timer_state(vcpu->vcpu_id,
- apic->lapic_timer.hv_timer_in_use);
- }
+ !atomic_read(&apic->lapic_timer.pending))
+ start_hv_tscdeadline(apic);
}
EXPORT_SYMBOL_GPL(kvm_lapic_switch_to_hv_timer);

@@ -1451,15 +1464,9 @@ static void start_apic_timer(struct kvm_lapic *apic)
ktime_to_ns(ktime_add_ns(now,
apic->lapic_timer.period)));
} else if (apic_lvtt_tscdeadline(apic)) {
- /* lapic timer in tsc deadline mode */
- u64 tscdeadline = apic->lapic_timer.tscdeadline;
-
- if (kvm_x86_ops->set_hv_timer &&
- !kvm_x86_ops->set_hv_timer(apic->vcpu, tscdeadline)) {
- apic->lapic_timer.hv_timer_in_use = true;
- trace_kvm_hv_timer_state(apic->vcpu->vcpu_id,
- apic->lapic_timer.hv_timer_in_use);
- } else
+ if (kvm_x86_ops->set_hv_timer)
+ start_hv_tscdeadline(apic);
+ else
start_sw_tscdeadline(apic);
}
}
\
 
 \ /
  Last update: 2016-06-29 01:21    [W:0.060 / U:0.788 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site