Re: [PATCH v3 2/2] KVM: x86/xen: Stop Xen timer before changing IRQ

[Sean Christopherson]

On Tue, Aug 09, 2022, Paolo Bonzini wrote:
> On 8/9/22 16:16, David Woodhouse wrote:
> > I find the new version a bit harder to follow, with its init-then-stop-
> > then-start logic:
> > 
> > 	case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
> > 		if (data->u.timer.port &&
> > 		    data->u.timer.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL) {
> > 			r = -EINVAL;
> > 			break;
> >                  }
> > 
> > 		if (!vcpu->arch.xen.timer.function)
> > 			kvm_xen_init_timer(vcpu);
> > 
> > 		/* Stop the timer (if it's running) before changing the vector */
> > 		kvm_xen_stop_timer(vcpu);
> > 		vcpu->arch.xen.timer_virq = data->u.timer.port;
> 
> 
> I think this is fine, if anything the kvm_xen_stop_timer() call could be
> placed in an "else" but I'm leaning towards applying this version of the
> patch.

I wanted to separate the "init" from the "stop+start", e.g. if there were a more
appropriate place for invoking kvm_xen_init_timer() I would have suggested moving
the call outside of KVM_XEN_VCPU_ATTR_TYPE_TIMER entirely.