[PATCH v5 7/8] KVM: arm/arm64: Provide a get_input_level for the arch timer

[Andrew Jones]

On Mon, Nov 20, 2017 at 08:16:48PM +0100, Christoffer Dall wrote:
> The VGIC can now support the life-cycle of mapped level-triggered
> interrupts, and we no longer have to read back the timer state on every
> exit from the VM if we had an asserted timer interrupt signal, because
> the VGIC already knows if we hit the unlikely case where the guest
> disables the timer without ACKing the virtual timer interrupt.
> 
> This means we rework a bit of the code to factor out the functionality
> to snapshot the timer state from vtimer_save_state(), and we can reuse
> this functionality in the sync path when we have an irqchip in
> userspace, and also to support our implementation of the
> get_input_level() function for the timer.
> 
> This change also means that we can no longer rely on the timer's view of
> the interrupt line to set the active state, because we no longer
> maintain this state for mapped interrupts when exiting from the guest.
> Instead, we only set the active state if the virtual interrupt is
> active, and otherwise we simply let the timer fire again and raise the
> virtual interrupt from the ISR.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
> ---
>  include/kvm/arm_arch_timer.h |  2 ++
>  virt/kvm/arm/arch_timer.c    | 76 +++++++++++++++++++++-----------------------
>  2 files changed, 39 insertions(+), 39 deletions(-)
> 
> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
> index 6e45608b2399..b1dcfde0a3ef 100644
> --- a/include/kvm/arm_arch_timer.h
> +++ b/include/kvm/arm_arch_timer.h
> @@ -90,6 +90,8 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu);
>  
>  void kvm_timer_init_vhe(void);
>  
> +bool kvm_arch_timer_get_input_level(int vintid);
> +
>  #define vcpu_vtimer(v)	(&(v)->arch.timer_cpu.vtimer)
>  #define vcpu_ptimer(v)	(&(v)->arch.timer_cpu.ptimer)
>  
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 8f804ba5896f..bcde6bb99669 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -343,6 +343,12 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu)
>  	phys_timer_emulate(vcpu);
>  }
>  
> +static void __timer_snapshot_state(struct arch_timer_context *timer)
> +{
> +	timer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> +	timer->cnt_cval = read_sysreg_el0(cntv_cval);
> +}
> +
>  static void vtimer_save_state(struct kvm_vcpu *vcpu)
>  {
>  	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
> @@ -354,10 +360,8 @@ static void vtimer_save_state(struct kvm_vcpu *vcpu)
>  	if (!vtimer->loaded)
>  		goto out;
>  
> -	if (timer->enabled) {
> -		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> -		vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
> -	}
> +	if (timer->enabled)
> +		__timer_snapshot_state(vtimer);
>  
>  	/* Disable the virtual timer */
>  	write_sysreg_el0(0, cntv_ctl);
> @@ -454,8 +458,7 @@ static void kvm_timer_vcpu_load_vgic(struct kvm_vcpu *vcpu)
>  	bool phys_active;
>  	int ret;
>  
> -	phys_active = vtimer->irq.level ||
> -		      kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
> +	phys_active = kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
>  
>  	ret = irq_set_irqchip_state(host_vtimer_irq,
>  				    IRQCHIP_STATE_ACTIVE,
> @@ -535,27 +538,19 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
>  	set_cntvoff(0);
>  }
>  
> -static void unmask_vtimer_irq(struct kvm_vcpu *vcpu)
> +/*
> + * With a userspace irqchip we have to check if the guest de-asserted the
> + * timer and if so, unmask the timer irq signal on the host interrupt
> + * controller to ensure that we see future timer signals.
> + */
> +static void unmask_vtimer_irq_user(struct kvm_vcpu *vcpu)
>  {
>  	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
>  
>  	if (unlikely(!irqchip_in_kernel(vcpu->kvm))) {
> -		kvm_vtimer_update_mask_user(vcpu);
> -		return;
> -	}
> -
> -	/*
> -	 * If the guest disabled the timer without acking the interrupt, then
> -	 * we must make sure the physical and virtual active states are in
> -	 * sync by deactivating the physical interrupt, because otherwise we
> -	 * wouldn't see the next timer interrupt in the host.
> -	 */
> -	if (!kvm_vgic_map_is_active(vcpu, vtimer->irq.irq)) {
> -		int ret;
> -		ret = irq_set_irqchip_state(host_vtimer_irq,
> -					    IRQCHIP_STATE_ACTIVE,
> -					    false);
> -		WARN_ON(ret);
> +		__timer_snapshot_state(vtimer);
> +		if (!kvm_timer_should_fire(vtimer))
> +			kvm_vtimer_update_mask_user(vcpu);
>  	}
>  }
>  
> @@ -568,21 +563,7 @@ static void unmask_vtimer_irq(struct kvm_vcpu *vcpu)
>   */
>  void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
>  {
> -	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
> -
> -	/*
> -	 * If we entered the guest with the vtimer output asserted we have to
> -	 * check if the guest has modified the timer so that we should lower
> -	 * the line at this point.
> -	 */
> -	if (vtimer->irq.level) {
> -		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> -		vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
> -		if (!kvm_timer_should_fire(vtimer)) {
> -			kvm_timer_update_irq(vcpu, false, vtimer);
> -			unmask_vtimer_irq(vcpu);
> -		}
> -	}
> +	unmask_vtimer_irq_user(vcpu);
>  }
>  
>  int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
> @@ -813,6 +794,23 @@ static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu)
>  	return true;
>  }
>  
> +bool kvm_arch_timer_get_input_level(int vintid)
> +{
> +	struct kvm_vcpu *vcpu = kvm_arm_get_running_vcpu();
> +	struct arch_timer_context *timer;
> +
> +

extra blank line here

> +	if (vintid == vcpu_vtimer(vcpu)->irq.irq)
> +		timer = vcpu_vtimer(vcpu);
> +	else
> +		BUG(); /* We only map the vtimer so far */
> +
> +	if (timer->loaded)
> +		__timer_snapshot_state(timer);
> +
> +	return kvm_timer_should_fire(timer);
> +}
> +
>  int kvm_timer_enable(struct kvm_vcpu *vcpu)
>  {
>  	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
> @@ -835,7 +833,7 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
>  	}
>  
>  	ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq,
> -				    NULL);
> +				    kvm_arch_timer_get_input_level);
>  	if (ret)
>  		return ret;
>  
> -- 
> 2.14.2
>