Re: [PATCH] KVM: SVM: compile out AVIC if !CONFIG_X86_LOCAL_APIC

[Suravee Suthikulanit]

On 6/14/2016 4:22 PM, Paolo Bonzini wrote:
> ----- Original Message -----
> > From: "Suravee Suthikulanit" <suravee.suthikulpanit@xxxxxxx>
> > To: "Paolo Bonzini" <pbonzini@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, kvm@xxxxxxxxxxxxxxx
> > Cc: rkrcmar@xxxxxxxxxx
> > Sent: Tuesday, June 14, 2016 8:20:30 PM
> > Subject: Re: [PATCH] KVM: SVM: compile out AVIC if !CONFIG_X86_LOCAL_APIC
> >
> > Hi Paolo,
> >
> > On 6/14/2016 11:40 AM, Paolo Bonzini wrote:
> > > AVIC needs __default_cpu_present_to_apicid.  Stub out all functions
> > > that use it, and disable the module parameter, if Linux is
> > > compiled without local APIC support.
> >
> > I think you are right that we should disable AVIC #ifndef
> > CONFIG_X86_LOCAL_APIC. However, do you think we should just use
> > default_cpu_present_to_apicid() instead of the
> > __default_cpu_present_to_apicid()?
>
> I'm not sure why that would help?  default_cpu_present_to_apicid
> is also declared only if CONFIG_X86_LOCAL_APIC is defined.

Actually, I also meant to include the change that I sent out 
(https://lkml.org/lkml/2016/6/13/898), which declares a dummy for the 
case #ifndef CONFIG_X86_LOCAL_APIC.  That should help with the issue here.

> > As for disabling AVIC, I think we can also do:
> >
> >      if (!IS_ENABLED(CONFIG_X86_LOCAL_APIC))
> >          avic = false;
>
> Yes, we'll need to do that once AVIC is enabled by default; or
>
> static bool avic = IS_ENABLED(CONFIG_X86_LOCAL_APIC);
>
> In any case the module parameter must be hidden if there's no
> support in the kernel for the local APIC.
>
> Paolo

Agree.

If you okay with using default_cpu_present_to_apicid(), I can send out 
the v2 of the "[PATCH] x86/SVM: Fix implicit declaration issue for 
__default_cpu_present_to_apicid()" with changes that you suggested here.

Thanks,
Suravee