Re: [PATCH] Fix almost infinite loop in APIC

Sheng Yang
2009-01-21T05:11:28Z

On Wednesday 21 January 2009 12:23:30 Marcelo Tosatti wrote:
> On Wed, Jan 21, 2009 at 10:40:49AM +0800, Sheng Yang wrote:
> > Mind continue to change...
> >
> > A: time_fire
> > B: intr_post
> > C: read TMCCT
> >
> > I think the sequence can be AABC or AACB(I just consider AABC last
> > night...). We have determined to return A->C as TMCCT, and the interval
> > between different A is period which can be ignored. So how about simply
> > return
> > hrtimer_expires_remaining() for all tmcct reading including pending ones?
> >
> > (And sorry for I still can't get why you return injection delay for
> > TMCCT...)
>
> You're right. How about this.
>
>
> diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
> index c019b8e..cf17ed5 100644
> --- a/arch/x86/kvm/irq.c
> +++ b/arch/x86/kvm/irq.c
> @@ -87,13 +87,6 @@ void kvm_inject_pending_timer_irqs(struct kvm_vcpu
> *vcpu) }
> EXPORT_SYMBOL_GPL(kvm_inject_pending_timer_irqs);
>
> -void kvm_timer_intr_post(struct kvm_vcpu *vcpu, int vec)
> -{
> - kvm_apic_timer_intr_post(vcpu, vec);
> - /* TODO: PIT, RTC etc. */
> -}
> -EXPORT_SYMBOL_GPL(kvm_timer_intr_post);
> -
> void __kvm_migrate_timers(struct kvm_vcpu *vcpu)
> {
> __kvm_migrate_apic_timer(vcpu);
> diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
> index 2bf32a0..82579ee 100644
> --- a/arch/x86/kvm/irq.h
> +++ b/arch/x86/kvm/irq.h
> @@ -89,7 +89,6 @@ static inline int irqchip_in_kernel(struct kvm *kvm)
>
> void kvm_pic_reset(struct kvm_kpic_state *s);
>
> -void kvm_timer_intr_post(struct kvm_vcpu *vcpu, int vec);
> void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu);
> void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu);
> void kvm_apic_nmi_wd_deliver(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index afac68c..b66f71e 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -511,52 +511,22 @@ static void apic_send_ipi(struct kvm_lapic *apic)
>
> static u32 apic_get_tmcct(struct kvm_lapic *apic)
> {
> - u64 counter_passed;
> - ktime_t passed, now;
> + ktime_t remaining;
> + s64 ns;
> u32 tmcct;
>
> ASSERT(apic != NULL);
>
> - now = apic->timer.dev.base->get_time();
> - tmcct = apic_get_reg(apic, APIC_TMICT);
> -
> /* if initial count is 0, current count should also be 0 */
> - if (tmcct == 0)
> + if (apic_get_reg(apic, APIC_TMICT) == 0)
> return 0;
>
> - if (unlikely(ktime_to_ns(now) <=
> - ktime_to_ns(apic->timer.last_update))) {
> - /* Wrap around */
> - passed = ktime_add(( {
> - (ktime_t) {
> - .tv64 = KTIME_MAX -
> - (apic->timer.last_update).tv64}; }
> - ), now);
> - apic_debug("time elapsed\n");
> - } else
> - passed = ktime_sub(now, apic->timer.last_update);
> -
> - counter_passed = div64_u64(ktime_to_ns(passed),
> - (APIC_BUS_CYCLE_NS * apic->timer.divide_count));
> -
> - if (counter_passed > tmcct) {
> - if (unlikely(!apic_lvtt_period(apic))) {
> - /* one-shot timers stick at 0 until reset */
> - tmcct = 0;
> - } else {
> - /*
> - * periodic timers reset to APIC_TMICT when they
> - * hit 0. The while loop simulates this happening N
> - * times. (counter_passed %= tmcct) would also work,
> - * but might be slower or not work on 32-bit??
> - */
> - while (counter_passed > tmcct)
> - counter_passed -= tmcct;
> - tmcct -= counter_passed;
> - }
> - } else {
> - tmcct -= counter_passed;
> - }
> + remaining = hrtimer_expires_remaining(&apic->timer.dev);
> + if (remaining.tv64 < 0)

Use ktime_to_ns() macro is better.

The remaining parts are fine with me. But please do more test. :)

Thanks for work!

--
regards
Yang, Sheng

> + remaining = ktime_set(0, 0);
> +
> + ns = ktime_to_ns(remaining) % apic->timer.period;
> + tmcct = div64_u64(ns, (APIC_BUS_CYCLE_NS * apic->timer.divide_count));
>
> return tmcct;
> }
> @@ -653,8 +623,6 @@ static void start_apic_timer(struct kvm_lapic *apic)
> {
> ktime_t now = apic->timer.dev.base->get_time();
>
> - apic->timer.last_update = now;
> -
> apic->timer.period = apic_get_reg(apic, APIC_TMICT) *
> APIC_BUS_CYCLE_NS * apic->timer.divide_count;
> atomic_set(&apic->timer.pending, 0);
> @@ -1110,16 +1078,6 @@ void kvm_inject_apic_timer_irqs(struct kvm_vcpu
> *vcpu) }
> }
>
> -void kvm_apic_timer_intr_post(struct kvm_vcpu *vcpu, int vec)
> -{
> - struct kvm_lapic *apic = vcpu->arch.apic;
> -
> - if (apic && apic_lvt_vector(apic, APIC_LVTT) == vec)
> - apic->timer.last_update = ktime_add_ns(
> - apic->timer.last_update,
> - apic->timer.period);
> -}
> -
> int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu)
> {
> int vector = kvm_apic_has_interrupt(vcpu);
> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> index 8185888..45ab6ee 100644
> --- a/arch/x86/kvm/lapic.h
> +++ b/arch/x86/kvm/lapic.h
> @@ -12,7 +12,6 @@ struct kvm_lapic {
> atomic_t pending;
> s64 period; /* unit: ns */
> u32 divide_count;
> - ktime_t last_update;
> struct hrtimer dev;
> } timer;
> struct kvm_vcpu *vcpu;
> @@ -42,7 +41,6 @@ void kvm_set_apic_base(struct kvm_vcpu *vcpu, u64 data);
> void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu);
> int kvm_lapic_enabled(struct kvm_vcpu *vcpu);
> int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu);
> -void kvm_apic_timer_intr_post(struct kvm_vcpu *vcpu, int vec);
>
> void kvm_lapic_set_vapic_addr(struct kvm_vcpu *vcpu, gpa_t vapic_addr);
> void kvm_lapic_sync_from_vapic(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 14e517e..db5021b 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2305,7 +2305,6 @@ static void svm_intr_assist(struct kvm_vcpu *vcpu)
> /* Okay, we can deliver the interrupt: grab it and update PIC state. */
> intr_vector = kvm_cpu_get_interrupt(vcpu);
> svm_inject_irq(svm, intr_vector);
> - kvm_timer_intr_post(vcpu, intr_vector);
> out:
> update_cr8_intercept(vcpu);
> }
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 9b56d21..25aaf11 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3377,7 +3377,6 @@ static void vmx_intr_assist(struct kvm_vcpu *vcpu)
> }
> if (vcpu->arch.interrupt.pending) {
> vmx_inject_irq(vcpu, vcpu->arch.interrupt.nr);
> - kvm_timer_intr_post(vcpu, vcpu->arch.interrupt.nr);
> if (kvm_cpu_has_interrupt(vcpu))
> enable_irq_window(vcpu);
> }