On Tue, Apr 04, 2017 at 07:46:12PM +0200, Christoffer Dall wrote:
> On Fri, Mar 31, 2017 at 06:06:56PM +0200, Andrew Jones wrote:
> > Refactor PMU overflow handling in order to remove the request-less
> > vcpu kick.  Now, since kvm_vgic_inject_irq() uses vcpu requests,
> > there should be no chance that a kick sent at just the wrong time
> > (between the VCPU's call to kvm_pmu_flush_hwstate() and before it
> > enters guest mode) results in a failure for the guest to see updated
> > GIC state until its next exit some time later for some other reason.
> > 
> > Signed-off-by: Andrew Jones <drjo...@redhat.com>
> > ---
> >  virt/kvm/arm/pmu.c | 29 +++++++++++++++--------------
> >  1 file changed, 15 insertions(+), 14 deletions(-)
> > 
> > diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> > index 69ccce308458..9d725f3afb11 100644
> > --- a/virt/kvm/arm/pmu.c
> > +++ b/virt/kvm/arm/pmu.c
> > @@ -203,6 +203,19 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu 
> > *vcpu)
> >     return reg;
> >  }
> >  
> > +static void kvm_pmu_check_overflow(struct kvm_vcpu *vcpu)
> > +{
> > +   struct kvm_pmu *pmu = &vcpu->arch.pmu;
> > +   bool overflow;
> > +
> > +   overflow = !!kvm_pmu_overflow_status(vcpu);
> > +   if (pmu->irq_level != overflow) {
> > +           pmu->irq_level = overflow;
> > +           kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
> > +                               pmu->irq_num, overflow);
> > +   }
> > +}
> > +
> 
> If we are changing the way the PMU works to adjust the interrupt
> signaling whenever the PMU changes its internal state, do we still ahv
> to call kvm_pmu_update_state() from each flush/sync path now?

The thought crossed my mind to rework that completely, in order to remove
that flush/sync, but then went for the smaller patch for this series.  I
can take a look at it though.

Thanks,
drew

> 
> >  /**
> >   * kvm_pmu_overflow_set - set PMU overflow interrupt
> >   * @vcpu: The vcpu pointer
> > @@ -210,31 +223,19 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu 
> > *vcpu)
> >   */
> >  void kvm_pmu_overflow_set(struct kvm_vcpu *vcpu, u64 val)
> >  {
> > -   u64 reg;
> > -
> >     if (val == 0)
> >             return;
> >  
> >     vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= val;
> > -   reg = kvm_pmu_overflow_status(vcpu);
> > -   if (reg != 0)
> > -           kvm_vcpu_kick(vcpu);
> > +   kvm_pmu_check_overflow(vcpu);
> >  }
> >  
> >  static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
> >  {
> > -   struct kvm_pmu *pmu = &vcpu->arch.pmu;
> > -   bool overflow;
> > -
> >     if (!kvm_arm_pmu_v3_ready(vcpu))
> >             return;
> >  
> > -   overflow = !!kvm_pmu_overflow_status(vcpu);
> > -   if (pmu->irq_level != overflow) {
> > -           pmu->irq_level = overflow;
> > -           kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
> > -                               pmu->irq_num, overflow);
> > -   }
> > +   kvm_pmu_check_overflow(vcpu);
> >  }
> >  
> >  /**
> > -- 
> > 2.9.3
> > 
> 
> Thanks,
> -Christoffer
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