On 21.04.2018 19:30, Anthoine Bourgeois wrote:
> Since the commit "8003c9ae204e: add APIC Timer periodic/oneshot mode VMX
> preemption timer support", a Windows 10 guest has some erratic timer
> spikes after few hours. As the uptime of the VM grows the spikes are
> larger.
>
> Here the results on a 150000 times 1ms timer without any load:
> Before 8003c9ae204e | After 8003c9ae204e
> Max 1834us | 86000us
> Mean 1100us | 1021us
> Deviation 59us | 149us
> Here the results on a 150000 times 1ms timer with a cpu-z stress test:
> Before 8003c9ae204e | After 8003c9ae204e
> Max 32000us | 140000us
> Mean 1006us | 1997us
> Deviation 140us | 11095us
>
> The current patch partially revert the previous commit by removing the
> target timer expectation to go back to the straight hrtimer calls. The
> APIC Timer periodic/oneshot mode support is kept because it is necessary
> on the new Windows Spring update.
>
> Signed-off-by: Anthoine Bourgeois <anthoine.bourgeois@xxxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/lapic.c | 57 ++++++++++++++++++++++++----------------------------
> arch/x86/kvm/lapic.h | 1 -
> 2 files changed, 26 insertions(+), 32 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 70dcb5548022..d88cf12259ef 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1173,7 +1173,7 @@ static void apic_send_ipi(struct kvm_lapic *apic)
>
> static u32 apic_get_tmcct(struct kvm_lapic *apic)
> {
> - ktime_t remaining, now;
> + ktime_t remaining;
> s64 ns;
> u32 tmcct;
>
> @@ -1184,8 +1184,7 @@ static u32 apic_get_tmcct(struct kvm_lapic *apic)
> apic->lapic_timer.period == 0)
> return 0;
>
> - now = ktime_get();
> - remaining = ktime_sub(apic->lapic_timer.target_expiration, now);
> + remaining = hrtimer_get_remaining(&apic->lapic_timer.timer);
> if (ktime_to_ns(remaining) < 0)
> remaining = 0;
>
> @@ -1465,32 +1464,48 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
>
> static void start_sw_period(struct kvm_lapic *apic)
> {
> + ktime_t now;
> +
> + /* lapic timer in oneshot or periodic mode */
> + now = ktime_get();
> + apic->lapic_timer.period = (u64)kvm_lapic_get_reg(apic, APIC_TMICT)
> + * APIC_BUS_CYCLE_NS * apic->divide_count;
> +
> if (!apic->lapic_timer.period)
> return;
>
> - if (apic_lvtt_oneshot(apic) &&
> - ktime_after(ktime_get(),
> - apic->lapic_timer.target_expiration)) {
> + limit_periodic_timer_frequency(apic);
> +
> + if (apic_lvtt_oneshot(apic)) {
> apic_timer_expired(apic);
> return;
> }
>
So in oneshot is mode hrtimer is never armed?
..Mika
