linux-kernel - RE: [patch] x86, kvm: fix build failure with CONFIG

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Date:	Thu, 18 Apr 2013 00:35:14 +0000
From:	"Zhang, Yang Z" <yang.z.zhang@...el.com>
To:	David Rientjes <rientjes@...gle.com>,
	Randy Dunlap <rdunlap@...radead.org>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	KVM <kvm@...r.kernel.org>
Subject: RE: [patch] x86, kvm: fix build failure with CONFIG_SMP disabled

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@...el.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@...el.com>

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


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