Re: [patch] x86, kvm: fix build failure with CONFIG_SMP disabled

From: Randy Dunlap <rdunlap@infradead.org>
To: "Zhang, Yang Z" <yang.z.zhang@intel.com>
Cc: David Rientjes <rientjes@google.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Gleb Natapov <gleb@redhat.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	"x86@kernel.org" <x86@kernel.org>,
	"linux-next@vger.kernel.org" <linux-next@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	KVM <kvm@vger.kernel.org>
Subject: Re: [patch] x86, kvm: fix build failure with CONFIG_SMP disabled
Date: Wed, 17 Apr 2013 17:47:07 -0700	[thread overview]
Message-ID: <516F428B.7010900@infradead.org> (raw)
In-Reply-To: <A9667DDFB95DB7438FA9D7D576C3D87E09A13B08@SHSMSX101.ccr.corp.intel.com>

On 04/17/13 17:35, Zhang, Yang Z wrote:
> David Rientjes wrote on 2013-04-18:
>> On Wed, 17 Apr 2013, Randy Dunlap wrote:
>>
>>> On 04/17/13 16:12, David Rientjes wrote:
>>>> The build fails when CONFIG_SMP is disabled:
>>>>
>>>> 	arch/x86/kvm/vmx.c: In function 'vmx_deliver_posted_interrupt':
>>>> 	arch/x86/kvm/vmx.c:3950:3: error: 'apic' undeclared (first use in
>>>> this function)
>>>>
>>>> Fix it by including the necessary header.
>>>
>>> Sorry, i386 build still fails with the same error message plus this one:
>>>
>>> ERROR: "apic" [arch/x86/kvm/kvm-intel.ko] undefined!
>>>
>>
>> Ahh, that's because you don't have CONFIG_X86_LOCAL_APIC as you already
>> mentioned.  So it looks like this error can manifest in two different ways
>> and we got different reports.
>>
>> This failure came from "KVM: VMX: Add the deliver posted interrupt
>> algorithm", so adding Yang to the cc to specify the dependency this has on
>> apic and how it can be protected without CONFIG_X86_LOCAL_APIC on i386.
> How about the follow patch?
> 
> commit a49dd819f502c1029c5a857e87201ef25ec06ce6
> Author: Yang Zhang <yang.z.zhang@Intel.com>
> Date:   Wed Apr 17 05:34:07 2013 -0400
> 
>     KVM: x86: Don't sending posted interrupt if not config CONFIG_SMP
> 
>     In UP, posted interrupt logic will not work. So we should not send
>     posted interrupt and let vcpu to pick the pending interrupt before
>     vmentry.
> 
>     Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>

Missing Reported-by: and the patch does not apply cleanly (looks like
lots of spaces instead of tabs in it)... but it does build now after
massaging the patch.

Thanks.

Acked-by: Randy Dunlap <rdunlap@infradead.org>

> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 52b21da..d5c6b95 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3946,10 +3946,12 @@ static void vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu, int vector)
> 
>         r = pi_test_and_set_on(&vmx->pi_desc);
>         kvm_make_request(KVM_REQ_EVENT, vcpu);
> +#ifdef CONFIG_SMP
>         if (!r && (vcpu->mode == IN_GUEST_MODE))
>                 apic->send_IPI_mask(get_cpu_mask(vcpu->cpu),
>                                 POSTED_INTR_VECTOR);
>         else
> +#endif
>                 kvm_vcpu_kick(vcpu);
>  }
> 
> Best regards,
> Yang
> 
> 

-- 
~Randy