kvm: Allow build-time configuration of KVM device assignment

We hope to at some point deprecate KVM legacy device assignment in
favor of VFIO-based assignment.  Towards that end, allow legacy
device assignment to be deconfigured.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 145b1c8..8747fef 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2501,7 +2501,6 @@
 	case KVM_CAP_USER_NMI:
 	case KVM_CAP_REINJECT_CONTROL:
 	case KVM_CAP_IRQ_INJECT_STATUS:
-	case KVM_CAP_ASSIGN_DEV_IRQ:
 	case KVM_CAP_IRQFD:
 	case KVM_CAP_IOEVENTFD:
 	case KVM_CAP_PIT2:
@@ -2519,9 +2518,12 @@
 	case KVM_CAP_XSAVE:
 	case KVM_CAP_ASYNC_PF:
 	case KVM_CAP_GET_TSC_KHZ:
-	case KVM_CAP_PCI_2_3:
 	case KVM_CAP_KVMCLOCK_CTRL:
 	case KVM_CAP_READONLY_MEM:
+#ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
+	case KVM_CAP_ASSIGN_DEV_IRQ:
+	case KVM_CAP_PCI_2_3:
+#endif
 		r = 1;
 		break;
 	case KVM_CAP_COALESCED_MMIO: