Re: [PATCH v2 3/3] KVM: SVM: Add irqchip_split() checks before enabling AVIC

[Suravee Suthikulpanit]

Radim,

On 9/14/17 08:23, Suravee Suthikulpanit wrote:
> Radim,
>
> On 9/14/17 08:20, Radim KrÄmÃÅ wrote:
> > > @@ -1594,6 +1593,12 @@ static int avic_init_vcpu(struct vcpu_svm *svm)
> > >      if (!avic)
> > >          return 0;
> > >
> > > +    if (!kvm_vcpu_apicv_active(&svm->vcpu)) {
> > > +        pr_debug("%s: Disable AVIC due to non-split irqchip.\n",
> > > +                  __func__);
> > We need to have an extra condition just because of this print ...
> > I removed the print altogether when applying -- I thought more about
> > that and it was aimed at people who wonder why AVIC was suddenly
> > disabled and it's unlikely that they will enable a debug message without
> > already knowing the reason,
>
> Make sense. Thanks.
>
> > thanks.
> >
> > > @@ -4388,7 +4393,7 @@ static void svm_set_virtual_x2apic_mode(struct kvm_vcpu
> > > *vcpu, bool set)
> > >
> > >  static bool svm_get_enable_apicv(struct kvm_vcpu *vcpu)
> > >  {
> > A close contender was pr_info_once() here:
> >
> >     if (avic && !irqchip_split(vcpu->kvm))
> >         pr_info_once(...)
>
> Looks good.

Actually, thinking about it again, this would not work either since 
pr_xxx_once() would only print the message once per loading of kvm_amd module. 
However, we would prefer the message to be printed per VM initialization. I also 
tried adding the check and print this message in the kvm_x86_ops.vm_init(), but 
this also does not work since the vm_init() function is called before the 
kvm_vm_ioctl_enable_cap(KVM_CAP_SPLIT_IRQCHIP).

Therefore, pr_info() might be better here, even though this would get print per 
VCPU initialization. Any other suggestions?

Thanks,
Suravee