KVM: SVM: allocate AVIC data structures based on kvm_amd module parameter

Even if APICv is disabled at startup, the backing page and ir_list need
to be initialized in case they are needed later.  The only case in
which this can be skipped is for userspace irqchip, and that must be
done because avic_init_backing_page dereferences vcpu->arch.apic
(which is NULL for userspace irqchip).

Tested-by: rmuncrief@humanavance.com
Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=206579Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm.c

@@ -2194,8 +2194,9 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 static int avic_init_vcpu(struct vcpu_svm *svm)
 {
 	int ret;
+	struct kvm_vcpu *vcpu = &svm->vcpu;
 
-	if (!kvm_vcpu_apicv_active(&svm->vcpu))
+	if (!avic || !irqchip_in_kernel(vcpu->kvm))
 		return 0;
 
 	ret = avic_init_backing_page(&svm->vcpu);