linux-kernel - Re: [PATCH] KVM: SVM: compile out AVIC if !CONFIG_X86_LOCAL

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Message-ID: <fb8550c4-00d0-cbe7-33d4-a8147837ab00@amd.com>
Date:	Tue, 14 Jun 2016 17:09:26 -0500
From:	Suravee Suthikulanit <suravee.suthikulpanit@....com>
To:	Paolo Bonzini <pbonzini@...hat.com>
CC:	<linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
	<rkrcmar@...hat.com>
Subject: Re: [PATCH] KVM: SVM: compile out AVIC if !CONFIG_X86_LOCAL_APIC

On 6/14/2016 5:01 PM, Paolo Bonzini wrote:
>
> On 14/06/2016 23:44, Suravee Suthikulanit wrote:
>> > On 6/14/2016 4:22 PM, Paolo Bonzini wrote:
>>> >> ----- Original Message -----
>>>> >>> From: "Suravee Suthikulanit" <suravee.suthikulpanit@....com>
>>>> >>> To: "Paolo Bonzini" <pbonzini@...hat.com>,
>>>> >>> linux-kernel@...r.kernel.org, kvm@...r.kernel.org
>>>> >>> Cc: rkrcmar@...hat.com
>>>> >>> 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.
> I think it is by design that default_cpu_present_to_apicid() is absent.
>
> Perhaps you could create a kvm_cpu_get_apicid() function that is either
> __default_cpu_present_to_apicid() or WARN_ON_ONCE(1)+return 0?
>
> Paolo

Ok, I'll do that and send out V2.

Thanks,
Suravee