[PATCH v2 2/2] KVM: x86: Fix access to vcpu->arch.apic when the irqchip is not in kernel

[Jue Wang <juew@google.com>]

Fix an access to vcpu->arch.apic when KVM_X86_SETUP_MCE is called
without KVM_CREATE_IRQCHIP called or KVM_CAP_SPLIT_IRQCHIP is
enabled.

Reported-by: https://syzkaller.appspot.com/bug?id=10b9b238e087a6c9bef2cc48bee2375f58fabbfc

Fixes: 4b903561ec49 ("KVM: x86: Add Corrected Machine Check Interrupt (CMCI) emulation to lapic.")
Signed-off-by: Jue Wang <juew@google.com>
---
 arch/x86/kvm/x86.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4322a1365f74..5913f90ec3f2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4820,8 +4820,9 @@ static int kvm_vcpu_ioctl_x86_setup_mce(struct kvm_vcpu *vcpu,
 		if (mcg_cap & MCG_CMCI_P)
 			vcpu->arch.mci_ctl2_banks[bank] = 0;
 	}
-	vcpu->arch.apic->nr_lvt_entries =
-		KVM_APIC_MAX_NR_LVT_ENTRIES - !(mcg_cap & MCG_CMCI_P);
+	if (lapic_in_kernel(vcpu))
+		vcpu->arch.apic->nr_lvt_entries =
+			KVM_APIC_MAX_NR_LVT_ENTRIES - !(mcg_cap & MCG_CMCI_P);
 
 	static_call(kvm_x86_setup_mce)(vcpu);
 out:
-- 
2.37.0.rc0.161.g10f37bed90-goog