Subject: [PATCH v3 10/11] KVM: arm/arm64: timer: Allow the timer to control the active state

From: [email-masked] (Christoffer Dall)
Date: Tue, 4 Aug 2015 15:56:52 +0200

On Fri, Jul 24, 2015 at 04:55:08PM +0100, Marc Zyngier wrote:
> In order to remove the crude hack where we sneak the masked bit
> into the timer's control register, make use of the phys_irq_map
> API control the active state of the interrupt.
> 
> This causes some limited changes to allow for potential error
> propagation.
> 
> Signed-off-by: Marc Zyngier <[email-masked]>
> ---
>  arch/arm/kvm/reset.c         |  4 +---
>  arch/arm64/kvm/reset.c       |  4 +---
>  include/kvm/arm_arch_timer.h |  7 +++++--
>  virt/kvm/arm/arch_timer.c    | 29 ++++++++++++++++++++++-------
>  4 files changed, 29 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/arm/kvm/reset.c b/arch/arm/kvm/reset.c
> index f558c07..eeb85858 100644
> --- a/arch/arm/kvm/reset.c
> +++ b/arch/arm/kvm/reset.c
> @@ -77,7 +77,5 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
>  	kvm_reset_coprocs(vcpu);
>  
>  	/* Reset arch_timer context */
> -	kvm_timer_vcpu_reset(vcpu, cpu_vtimer_irq);
> -
> -	return 0;
> +	return kvm_timer_vcpu_reset(vcpu, cpu_vtimer_irq);
>  }
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index b4af618..91cf535 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -121,7 +121,5 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
>  	kvm_reset_sys_regs(vcpu);
>  
>  	/* Reset timer */
> -	kvm_timer_vcpu_reset(vcpu, cpu_vtimer_irq);
> -
> -	return 0;
> +	return kvm_timer_vcpu_reset(vcpu, cpu_vtimer_irq);
>  }
> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
> index e596675..e1e4d7c 100644
> --- a/include/kvm/arm_arch_timer.h
> +++ b/include/kvm/arm_arch_timer.h
> @@ -52,13 +52,16 @@ struct arch_timer_cpu {
>  
>  	/* Timer IRQ */
>  	const struct kvm_irq_level	*irq;
> +
> +	/* VGIC mapping */
> +	struct irq_phys_map		*map;
>  };
>  
>  int kvm_timer_hyp_init(void);
>  void kvm_timer_enable(struct kvm *kvm);
>  void kvm_timer_init(struct kvm *kvm);
> -void kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
> -			  const struct kvm_irq_level *irq);
> +int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
> +			 const struct kvm_irq_level *irq);
>  void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu);
>  void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu);
>  void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu);
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 98c95f2..76e38d2 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -64,10 +64,10 @@ static void kvm_timer_inject_irq(struct kvm_vcpu *vcpu)
>  	int ret;
>  	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
>  
> -	timer->cntv_ctl |= ARCH_TIMER_CTRL_IT_MASK;
> -	ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
> -				  timer->irq->irq,
> -				  timer->irq->level);
> +	kvm_vgic_set_phys_irq_active(timer->map, true);

actually, I'm not sure I understand the point of setting this boolean?
Is it just a check?  It seems everywhere we find the map in the VGIC
code, we have a BUG_ON(!map->active), so why doesn't (!!map) imply that
it should be marked as active?

Is this again for non-shared devices?

> +	ret = kvm_vgic_inject_mapped_irq(vcpu->kvm, vcpu->vcpu_id,
> +					 timer->map,
> +					 timer->irq->level);
>  	WARN_ON(ret);
>  }
>  
> @@ -117,7 +117,8 @@ bool kvm_timer_should_fire(struct kvm_vcpu *vcpu)
>  	cycle_t cval, now;
>  
>  	if ((timer->cntv_ctl & ARCH_TIMER_CTRL_IT_MASK) ||
> -		!(timer->cntv_ctl & ARCH_TIMER_CTRL_ENABLE))
> +	    !(timer->cntv_ctl & ARCH_TIMER_CTRL_ENABLE) ||
> +	    kvm_vgic_get_phys_irq_active(timer->map))

hmm, maybe this answers my question above.  It is the virtual active
state preventing us to keep injecting the virtual side?

I don't see anything functional wrong with this code though.

Thanks,
-Christoffer

>  		return false;
>  
>  	cval = timer->cntv_cval;
> @@ -184,10 +185,11 @@ void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
>  	timer_arm(timer, ns);
>  }
>  
> -void kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
> -			  const struct kvm_irq_level *irq)
> +int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
> +			 const struct kvm_irq_level *irq)
>  {
>  	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
> +	struct irq_phys_map *map;
>  
>  	/*
>  	 * The vcpu timer irq number cannot be determined in
> @@ -196,6 +198,17 @@ void kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
>  	 * vcpu timer irq number when the vcpu is reset.
>  	 */
>  	timer->irq = irq;
> +
> +	/*
> +	 * Tell the VGIC that the virtual interrupt is tied to a
> +	 * physical interrupt. We do that once per VCPU.
> +	 */
> +	map = kvm_vgic_map_phys_irq(vcpu, irq->irq, host_vtimer_irq);
> +	if (WARN_ON(IS_ERR(map)))
> +		return PTR_ERR(map);
> +
> +	timer->map = map;
> +	return 0;
>  }
>  
>  void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
> @@ -335,6 +348,8 @@ void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu)
>  	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
>  
>  	timer_disarm(timer);
> +	if (timer->map)
> +		kvm_vgic_unmap_phys_irq(vcpu, timer->map);
>  }
>  
>  void kvm_timer_enable(struct kvm *kvm)
> -- 
> 2.1.4
>