On Thu, Jun 3, 2021 at 2:04 AM Wanpeng Li <kernellwp@xxxxxxxxx> wrote:
>
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>
> According to the SDM 10.5.4.1:
>
> A write of 0 to the initial-count register effectively stops the local
> APIC timer, in both one-shot and periodic mode.
If KVM is not correctly emulating this behavior then could you also
add a kvm-unit-test to test for the correct behavior?
>
> The lapic timer oneshot/periodic mode which is emulated by vmx-preemption
> timer doesn't stop since vmx->hv_deadline_tsc is still set. This patch
> fixes it by also cancel vmx-preemption timer when writing 0 to initial-count
> register.
>
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> ---
> arch/x86/kvm/lapic.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 8120e86..20dd2ae 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1494,6 +1494,15 @@ static void limit_periodic_timer_frequency(struct kvm_lapic *apic)
>
> static void cancel_hv_timer(struct kvm_lapic *apic);
>
> +static void cancel_timer(struct kvm_lapic *apic)
> +{
> + hrtimer_cancel(&apic->lapic_timer.timer);
> + preempt_disable();
> + if (apic->lapic_timer.hv_timer_in_use)
> + cancel_hv_timer(apic);
> + preempt_enable();
> +}
> +
> static void apic_update_lvtt(struct kvm_lapic *apic)
> {
> u32 timer_mode = kvm_lapic_get_reg(apic, APIC_LVTT) &
> @@ -1502,11 +1511,7 @@ static void apic_update_lvtt(struct kvm_lapic *apic)
> if (apic->lapic_timer.timer_mode != timer_mode) {
> if (apic_lvtt_tscdeadline(apic) != (timer_mode ==
> APIC_LVT_TIMER_TSCDEADLINE)) {
> - hrtimer_cancel(&apic->lapic_timer.timer);
> - preempt_disable();
> - if (apic->lapic_timer.hv_timer_in_use)
> - cancel_hv_timer(apic);
> - preempt_enable();
> + cancel_timer(apic);
> kvm_lapic_set_reg(apic, APIC_TMICT, 0);
> apic->lapic_timer.period = 0;
> apic->lapic_timer.tscdeadline = 0;
> @@ -2092,7 +2097,7 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
> if (apic_lvtt_tscdeadline(apic))
> break;
>
> - hrtimer_cancel(&apic->lapic_timer.timer);
> + cancel_timer(apic);
> kvm_lapic_set_reg(apic, APIC_TMICT, val);
> start_apic_timer(apic);
> break;
> --
> 2.7.4
>
