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 19:40:27 +0200

On Tue, Aug 04, 2015 at 05:14:53PM +0100, Marc Zyngier wrote:
> On 04/08/15 14:56, Christoffer Dall wrote:
> > 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?
> > 
> 
> Setting the boolean here means that the interrupt should be marked
> active at the distributor level when the interrupt is injected. This
> also allows the timer code to find out when we can inject another
> interrupt (by checking that the interrupt is now inactive).
> 
> As for the BUG_ON(), this is really some debug stuff to make sure we
> have a consistent state.
> 
> Non-shared devices are handled separately (and setting the active state
> doesn't make much sense, as we expect this to be entirely HW driven).
> 
> Do you see anything I should add to make it more clear?
> 

no, I'm good with it now, I think adding more commentary etc. will just
confuse people even more... One simply has to understand this part of
the logic.

> >> +	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?
> > 
> 
> Exactly. This is effectively what the MASK state was doing, now
> replicated in SW...
> 

ok, in that case:

Reviewed-by: Christoffer Dall <[email-masked]>