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/Kconfig b/arch/x86/kvm/Kconfig
index 9d50efd..a47a3e5 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -21,8 +21,6 @@
 	tristate "Kernel-based Virtual Machine (KVM) support"
 	depends on HAVE_KVM
 	depends on HIGH_RES_TIMERS
-	# for device assignment:
-	depends on PCI
 	# for TASKSTATS/TASK_DELAY_ACCT:
 	depends on NET
 	select PREEMPT_NOTIFIERS
@@ -83,6 +81,17 @@
 	 This option adds a R/W kVM module parameter 'mmu_audit', which allows
 	 audit  KVM MMU at runtime.
 
+config KVM_DEVICE_ASSIGNMENT
+	bool "KVM legacy PCI device assignment support"
+	depends on KVM && PCI && IOMMU_API
+	default y
+	---help---
+	  Provide support for legacy PCI device assignment through KVM.  The
+	  kernel now also supports a full featured userspace device driver
+	  framework through VFIO, which supersedes much of this support.
+
+	  If unsure, say Y.
+
 # OK, it's a little counter-intuitive to do this, but it puts it neatly under
 # the virtualization menu.
 source drivers/vhost/Kconfig