From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH 16/38] KVM: PPC: BookE: Add check_requests helper function
Date: Wed, 15 Aug 2012 15:28:54 -0300
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Cc: Alexander Graf <agraf@suse.de>, kvm-ppc@vger.kernel.org,
	KVM list <kvm@vger.kernel.org>
To: Scott Wood <scottwood@freescale.com>
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On Tue, Aug 14, 2012 at 07:10:43PM -0500, Scott Wood wrote:
> 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

It is good practice to document each memory barrier.