Re: [PATCH 16/38] KVM: PPC: BookE: Add check_requests helper function

[Scott Wood <scottwood@freescale.com>]

On 08/14/2012 06:04 PM, Alexander Graf wrote:
> We need a central place to check for pending requests in. Add one that
> only does the timer check we already do in a different place.
> 
> Later, this central function can be extended by more checks.
> 
> Signed-off-by: Alexander Graf <agraf@suse.de>
> ---
>  arch/powerpc/kvm/booke.c |   24 +++++++++++++++++-------
>  1 files changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index 1d4ce9a..bcf87fe 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -419,13 +419,6 @@ static void kvmppc_core_check_exceptions(struct kvm_vcpu *vcpu)
>  	unsigned long *pending = &vcpu->arch.pending_exceptions;
>  	unsigned int priority;
>  
> -	if (vcpu->requests) {
> -		if (kvm_check_request(KVM_REQ_PENDING_TIMER, vcpu)) {
> -			smp_mb();
> -			update_timer_ints(vcpu);
> -		}
> -	}
> -
>  	priority = __ffs(*pending);
>  	while (priority < BOOKE_IRQPRIO_MAX) {
>  		if (kvmppc_booke_irqprio_deliver(vcpu, priority))
> @@ -461,6 +454,14 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
>  	return r;
>  }
>  
> +static void kvmppc_check_requests(struct kvm_vcpu *vcpu)
> +{
> +	if (vcpu->requests) {
> +		if (kvm_check_request(KVM_REQ_PENDING_TIMER, vcpu))
> +			update_timer_ints(vcpu);
> +	}
> +}
> +
>  /*
>   * Common checks before entering the guest world.  Call with interrupts
>   * disabled.
> @@ -485,6 +486,15 @@ static int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
>  			break;
>  		}
>  
> +		smp_mb();
> +		if (vcpu->requests) {
> +			/* Make sure we process requests preemptable */
> +			local_irq_enable();
> +			kvmppc_check_requests(vcpu);
> +			local_irq_disable();
> +			continue;
> +		}

What previous memory access is the smp_mb() ordering against?

-Scott