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Subject[PATCH 15/43] KVM: PIT: remove usage of count_load_time for channel 0
Date
From: Marcelo Tosatti <mtosatti@redhat.com>

We can infer elapsed time from hrtimer_expires_remaining.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
arch/x86/kvm/i8254.c | 37 +++++++++++++++++++++++++++++++------
1 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 3eddae6..09ae841 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -98,6 +98,32 @@ static int pit_get_gate(struct kvm *kvm, int channel)
return kvm->arch.vpit->pit_state.channels[channel].gate;
}

+static s64 __kpit_elapsed(struct kvm *kvm)
+{
+ s64 elapsed;
+ ktime_t remaining;
+ struct kvm_kpit_state *ps = &kvm->arch.vpit->pit_state;
+
+ remaining = hrtimer_expires_remaining(&ps->pit_timer.timer);
+ if (ktime_to_ns(remaining) < 0)
+ remaining = ktime_set(0, 0);
+
+ elapsed = ps->pit_timer.period;
+ if (ktime_to_ns(remaining) <= ps->pit_timer.period)
+ elapsed = ps->pit_timer.period - ktime_to_ns(remaining);
+
+ return elapsed;
+}
+
+static s64 kpit_elapsed(struct kvm *kvm, struct kvm_kpit_channel_state *c,
+ int channel)
+{
+ if (channel == 0)
+ return __kpit_elapsed(kvm);
+
+ return ktime_to_ns(ktime_sub(ktime_get(), c->count_load_time));
+}
+
static int pit_get_count(struct kvm *kvm, int channel)
{
struct kvm_kpit_channel_state *c =
@@ -107,7 +133,7 @@ static int pit_get_count(struct kvm *kvm, int channel)

WARN_ON(!mutex_is_locked(&kvm->arch.vpit->pit_state.lock));

- t = ktime_to_ns(ktime_sub(ktime_get(), c->count_load_time));
+ t = kpit_elapsed(kvm, c, channel);
d = muldiv64(t, KVM_PIT_FREQ, NSEC_PER_SEC);

switch (c->mode) {
@@ -137,7 +163,7 @@ static int pit_get_out(struct kvm *kvm, int channel)

WARN_ON(!mutex_is_locked(&kvm->arch.vpit->pit_state.lock));

- t = ktime_to_ns(ktime_sub(ktime_get(), c->count_load_time));
+ t = kpit_elapsed(kvm, c, channel);
d = muldiv64(t, KVM_PIT_FREQ, NSEC_PER_SEC);

switch (c->mode) {
@@ -208,8 +234,6 @@ static int __pit_timer_fn(struct kvm_kpit_state *ps)
wake_up_interruptible(&vcpu0->wq);

hrtimer_add_expires_ns(&pt->timer, pt->period);
- if (pt->period)
- ps->channels[0].count_load_time = ktime_get();

return (pt->period == 0 ? 0 : 1);
}
@@ -305,11 +329,12 @@ static void pit_load_count(struct kvm *kvm, int channel, u32 val)
if (val == 0)
val = 0x10000;

- ps->channels[channel].count_load_time = ktime_get();
ps->channels[channel].count = val;

- if (channel != 0)
+ if (channel != 0) {
+ ps->channels[channel].count_load_time = ktime_get();
return;
+ }

/* Two types of timer
* mode 1 is one shot, mode 2 is period, otherwise del timer */
--
1.6.0.6


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