Re: [RFC PATCH v2 06/19] KVM: arm/arm64: Make timer_arm and timer_disarm helpers more generic

Marc Zyngier
2017-08-01T14:10:59Z

On 17/07/17 15:27, Christoffer Dall wrote:
> We are about to add an additional soft timer to the arch timer state for
> a VCPU and would like to be able to reuse the functions to program and
> cancel a timer, so we make them slightly more generic and rename to make
> it more clear that these functions work on soft timers and not the
> hardware resource that this code is managing.
>
> Signed-off-by: Christoffer Dall <cdall@linaro.org>
> ---
> virt/kvm/arm/arch_timer.c | 33 ++++++++++++++++-----------------
> 1 file changed, 16 insertions(+), 17 deletions(-)
>
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 8e89d63..871d8ae 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -56,26 +56,22 @@ u64 kvm_phys_timer_read(void)
> return timecounter->cc->read(timecounter->cc);
> }
>
> -static bool timer_is_armed(struct arch_timer_cpu *timer)
> +static bool soft_timer_is_armed(struct arch_timer_cpu *timer)
> {
> return timer->armed;
> }
>
> -/* timer_arm: as in "arm the timer", not as in ARM the company */
> -static void timer_arm(struct arch_timer_cpu *timer, u64 ns)
> +static void soft_timer_start(struct hrtimer *hrt, u64 ns)

I find it a bit confusing that the soft_timer_* functions operate on
different object types: arch_timer_cpu for soft_timer_is_armed(), and
hrtimer for soft_timer_start. Is there anything that prevents us from
keeping arch_timer_cpu for all of them?

> {
> - timer->armed = true;
> - hrtimer_start(&timer->timer, ktime_add_ns(ktime_get(), ns),
> + hrtimer_start(hrt, ktime_add_ns(ktime_get(), ns),
> HRTIMER_MODE_ABS);
> }
>
> -static void timer_disarm(struct arch_timer_cpu *timer)
> +static void soft_timer_cancel(struct hrtimer *hrt, struct work_struct *work)
> {
> - if (timer_is_armed(timer)) {
> - hrtimer_cancel(&timer->timer);
> - cancel_work_sync(&timer->expired);
> - timer->armed = false;
> - }
> + hrtimer_cancel(hrt);
> + if (work)
> + cancel_work_sync(work);
> }
>
> static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
> @@ -271,7 +267,7 @@ static void kvm_timer_emulate(struct kvm_vcpu *vcpu,
> return;
>
> /* The timer has not yet expired, schedule a background timer */
> - timer_arm(timer, kvm_timer_compute_delta(timer_ctx));
> + soft_timer_start(&timer->timer, kvm_timer_compute_delta(timer_ctx));
> }
>
> /*
> @@ -285,7 +281,7 @@ void kvm_timer_schedule(struct kvm_vcpu *vcpu)
> struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
> struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
>
> - BUG_ON(timer_is_armed(timer));
> + BUG_ON(soft_timer_is_armed(timer));
>
> /*
> * No need to schedule a background timer if any guest timer has
> @@ -306,13 +302,16 @@ void kvm_timer_schedule(struct kvm_vcpu *vcpu)
> * The guest timers have not yet expired, schedule a background timer.
> * Set the earliest expiration time among the guest timers.
> */
> - timer_arm(timer, kvm_timer_earliest_exp(vcpu));
> + timer->armed = true;
> + soft_timer_start(&timer->timer, kvm_timer_earliest_exp(vcpu));
> }
>
> void kvm_timer_unschedule(struct kvm_vcpu *vcpu)
> {
> struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
> - timer_disarm(timer);
> +
> + soft_timer_cancel(&timer->timer, &timer->expired);
> + timer->armed = false;
> }
>
> static void kvm_timer_flush_hwstate_vgic(struct kvm_vcpu *vcpu)
> @@ -448,7 +447,7 @@ void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
> * This is to cancel the background timer for the physical timer
> * emulation if it is set.
> */
> - timer_disarm(timer);
> + soft_timer_cancel(&timer->timer, &timer->expired);
>
> /*
> * The guest could have modified the timer registers or the timer
> @@ -615,7 +614,7 @@ void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu)
> struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
> struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
>
> - timer_disarm(timer);
> + soft_timer_cancel(&timer->timer, &timer->expired);
> kvm_vgic_unmap_phys_irq(vcpu, vtimer->irq.irq);
> }
>
>

Otherwise looks good to me.

Thanks,

M.
--
Jazz is not dead. It just smells funny...