Re: [Qemu-devel] [RFC] create a single workqueue for each vm to update vm irq routing table

[Avi Kivity]

On 11/26/2013 06:28 PM, Paolo Bonzini wrote:
> Il 26/11/2013 17:24, Gleb Natapov ha scritto:
> > >      VCPU writes to routing table
> > >                                         e = entry from IRQ routing table
> > >      kvm_irq_routing_update(kvm, new);
> > >      VCPU resumes execution
> > >                                         kvm_set_msi_irq(e, &irq);
> > >                                         kvm_irq_delivery_to_apic_fast();
> > >
> > > where the entry is stale but the VCPU has already resumed execution.
> > So how is it different from what we have now:
> >
> > disable_irq()
> > VCPU writes to routing table
> >                                   e = entry from IRQ routing table
> >                                   kvm_set_msi_irq(e, &irq);
> >                                   kvm_irq_delivery_to_apic_fast();
> > kvm_irq_routing_update(kvm, new);
> > synchronize_rcu()
> > VCPU resumes execution
> > enable_irq()
> > receive stale irq
> Adding a "disable/enable IRQs" looks like a relatively big change.  But
> perhaps it's not for some reason I'm missing.

Those are guest operations, which may not be there at all.