Re: [PATCH 1/4] KVM: PPC: BookE: Allow irq deliveries to inject requests

[Scott Wood <scottwood@freescale.com>]

On 01/04/2013 11:36:37 AM, Alexander Graf wrote:
> When injecting an interrupt into guest context, we usually don't need
> to check for requests anymore. At least not until today.
> 
> With the introduction of EPR, we will have to create a request when  
> the
> guest has successfully accepted an external interrupt though.
> 
> So we need to prepare the interrupt delivery to abort guest entry
> gracefully. Otherwise we'd delay the EPR request.
> 
> Signed-off-by: Alexander Graf <agraf@suse.de>
> ---
>  arch/powerpc/kvm/booke.c |   14 ++++++++++----
>  1 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index 69f1140..4ae83f9 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -554,14 +554,16 @@ static void update_timer_ints(struct kvm_vcpu  
> *vcpu)
>  		kvmppc_core_dequeue_watchdog(vcpu);
>  }
> 
> -static void kvmppc_core_check_exceptions(struct kvm_vcpu *vcpu)
> +static int kvmppc_core_check_exceptions(struct kvm_vcpu *vcpu)
>  {
>  	unsigned long *pending = &vcpu->arch.pending_exceptions;
>  	unsigned int priority;
> +	int r = 0;
> 
>  	priority = __ffs(*pending);
>  	while (priority < BOOKE_IRQPRIO_MAX) {
> -		if (kvmppc_booke_irqprio_deliver(vcpu, priority))
> +		r = kvmppc_booke_irqprio_deliver(vcpu, priority);
> +		if (r)
>  			break;
> 
>  		priority = find_next_bit(pending,
> @@ -571,15 +573,19 @@ static void kvmppc_core_check_exceptions(struct  
> kvm_vcpu *vcpu)
> 
>  	/* Tell the guest about our interrupt status */
>  	vcpu->arch.shared->int_pending = !!*pending;
> +
> +	return r > 1;
>  }

It isn't until patch 3/4 that the reason for "r > 1" appears...

Why not just:

diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 69f1140..964f447 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -581,6 +581,11 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu  
*vcpu)

  	kvmppc_core_check_exceptions(vcpu);

+	if (vcpu->requests) {
+		/* Exception delivery raised request; start over */
+		return 1;
+	}
+
  	if (vcpu->arch.shared->msr & MSR_WE) {
  		local_irq_enable();
  		kvm_vcpu_block(vcpu);

...or if you really want to do it through return values, make it an  
enum rather than a magic "2".

-Scott