linux-kernel - [PATCH] KVM: x86: VMX: fix building without CONFIG

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Date:   Fri, 25 May 2018 17:36:17 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Cc:     Lan Tianyu <Tianyu.Lan@...rosoft.com>,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Jim Mattson <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        David Hildenbrand <david@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: x86: VMX: fix building without CONFIG_HYPERV

The global ms_hyperv variable is part of the hyperv support, so
we get a link error from accessing it in kernels that have this
turned off:

arch/x86/kvm/vmx.o: In function `alloc_loaded_vmcs':
vmx.c:(.text+0x1654a): undefined reference to `ms_hyperv'
vmx.c:(.text+0x1657a): undefined reference to `ms_hyperv'

This changes the condition to first check the compile-time
configuration symbol to avoid the link error.

Fixes: ceef7d10dfb6 ("KVM: x86: VMX: hyper-v: Enlightened MSR-Bitmap support")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/x86/kvm/vmx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ea098131dcce..e6d6ccab43c3 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4232,7 +4232,8 @@ static int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs)
 			goto out_vmcs;
 		memset(loaded_vmcs->msr_bitmap, 0xff, PAGE_SIZE);
 
-		if (static_branch_unlikely(&enable_evmcs) &&
+		if (IS_ENABLED(CONFIG_HYPERV) &&
+		    static_branch_unlikely(&enable_evmcs) &&
 		    (ms_hyperv.nested_features & HV_X64_NESTED_MSR_BITMAP)) {
 			struct hv_enlightened_vmcs *evmcs =
 				(struct hv_enlightened_vmcs *)loaded_vmcs->vmcs;
-- 
2.9.0