Re: [Xen-devel] [PATCH v2 4/4] VMX: fixup PI descritpor when cpu is offline

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> >> > @@ -122,10 +124,25 @@ static void vmx_vcpu_block(struct vcpu *v)
> >> >           * new vCPU to the list.
> >> >           */
> >> >          spin_unlock_irqrestore(&v->arch.hvm_vmx.pi_hotplug_lock, flags);
> >> > -        return;
> >> > +        return 1;
> >> >      }
> >> >
> >> >      spin_lock(pi_blocking_list_lock);
> >> > +    if ( unlikely(per_cpu(vmx_pi_blocking, v->processor).down) )
> >>
> >> Is this something that can actually happen? vmx_pi_desc_fixup()
> >> runs in stop-machine context, i.e. no CPU can actively be here (or
> >> anywhere near the arch_vcpu_block() call sites).
> >
> > This is related to scheduler, maybe Dario can give some input about
> > this. Dario?
> 
> Yeah, I was going to say just looking through this -- there's no way
> that vmx_cpu_dead() will be called while there are vcpus *still
> running* on that pcpu.  vcpus will be migrated to other pcpus before
> that happens.  All of your changes around vmx_vcpu_block() are
> unnecessary.

Thanks for the clarification, George!

Thanks,
Feng
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