I have only compile-tested it, but it should optimize the switch and
also fix two bugs. The first one is major.
This needs that the deadline clearing in [5/5] is fixed.
---8<---
We must start the hrimer even if the expiration is already in the past,
otherwise the periodic timer would not rearm the hrtimer.
And computing next expiration of a period timer does not require current
time. The period should be constant, so it is more precise to add the
period to the last expiration time. This fixes a time difference
between hrtimer expiration and apic->lapic_timer.target_expiration.
Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
---
arch/x86/kvm/lapic.c | 38 +++++++++++++-------------------------
1 file changed, 13 insertions(+), 25 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index f4734fe12803..6244988418be 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1350,19 +1350,19 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
static void start_sw_period(struct kvm_lapic *apic)
{
- ktime_t now;
-
- now = apic->lapic_timer.timer.base->get_time();
-
if (!apic->lapic_timer.period)
return;
- if (likely(ktime_after(apic->lapic_timer.target_expiration, now)))
- hrtimer_start(&apic->lapic_timer.timer,
- apic->lapic_timer.target_expiration,
- HRTIMER_MODE_ABS_PINNED);
- else
+ if (apic_lvtt_oneshot(apic) &&
+ ktime_after(apic->lapic_timer.target_expiration,
+ apic->lapic_timer.timer.base->get_time())) {
apic_timer_expired(apic);
+ return;
+ }
+
+ hrtimer_start(&apic->lapic_timer.timer,
+ apic->lapic_timer.target_expiration,
+ HRTIMER_MODE_ABS_PINNED);
}
static bool set_target_expiration(struct kvm_lapic *apic)
@@ -1414,10 +1414,11 @@ static bool set_target_expiration(struct kvm_lapic *apic)
static void advance_periodic_target_expiration(struct kvm_lapic *apic)
{
- apic->lapic_timer.tscdeadline = kvm_read_l1_tsc(apic->vcpu, rdtsc()) +
+ apic->lapic_timer.tscdeadline +=
nsec_to_cycles(apic->vcpu, apic->lapic_timer.period);
- apic->lapic_timer.target_expiration = ktime_add_ns(apic->lapic_timer.timer.base->get_time(),
- apic->lapic_timer.period);
+ apic->lapic_timer.target_expiration =
+ ktime_add_ns(apic->lapic_timer.target_expiration,
+ apic->lapic_timer.period);
}
bool kvm_lapic_hv_timer_in_use(struct kvm_vcpu *vcpu)
@@ -1481,19 +1482,6 @@ void kvm_lapic_switch_to_hv_timer(struct kvm_vcpu *vcpu)
WARN_ON(apic->lapic_timer.hv_timer_in_use);
- if (apic_lvtt_period(apic)) {
- ktime_t remaining, now;
- u64 tscl = rdtsc();
-
- now = apic->lapic_timer.timer.base->get_time();
- remaining = hrtimer_get_remaining(&apic->lapic_timer.timer);
- if (ktime_to_ns(remaining) < 0)
- remaining = ktime_set(0, 0);
-
- apic->lapic_timer.tscdeadline = kvm_read_l1_tsc(apic->vcpu, tscl) +
- nsec_to_cycles(apic->vcpu, ktime_to_ns(remaining));
- apic->lapic_timer.target_expiration = ktime_add_ns(now, ktime_to_ns(remaining));
- }
start_hv_timer(apic);
}
EXPORT_SYMBOL_GPL(kvm_lapic_switch_to_hv_timer);
--
2.10.1
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
