Merge tag 'vfio-v3.15-rc1' of git://github.com/awilliam/linux-vfio

Pull VFIO updates from Alex Williamson:
 "VFIO updates for v3.15 include:

   - Allow the vfio-type1 IOMMU to support multiple domains within a
     container
   - Plumb path to query whether all domains are cache-coherent
   - Wire query into kvm-vfio device to avoid KVM x86 WBINVD emulation
   - Always select CONFIG_ANON_INODES, vfio depends on it (Arnd)

  The first patch also makes the vfio-type1 IOMMU driver completely
  independent of the bus_type of the devices it's handling, which
  enables it to be used for both vfio-pci and a future vfio-platform
  (and hopefully combinations involving both simultaneously)"

* tag 'vfio-v3.15-rc1' of git://github.com/awilliam/linux-vfio:
  vfio: always select ANON_INODES
  kvm/vfio: Support for DMA coherent IOMMUs
  vfio: Add external user check extension interface
  vfio/type1: Add extension to test DMA cache coherence of IOMMU
  vfio/iommu_type1: Multi-IOMMU domain support

virt/kvm/vfio.c

@@ -59,6 +59,22 @@ static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group)
 	symbol_put(vfio_group_put_external_user);
 }
 
+static bool kvm_vfio_group_is_coherent(struct vfio_group *vfio_group)
+{
+	long (*fn)(struct vfio_group *, unsigned long);
+	long ret;
+
+	fn = symbol_get(vfio_external_check_extension);
+	if (!fn)
+		return false;
+
+	ret = fn(vfio_group, VFIO_DMA_CC_IOMMU);
+
+	symbol_put(vfio_external_check_extension);
+
+	return ret > 0;
+}
+
 /*
  * Groups can use the same or different IOMMU domains.  If the same then
  * adding a new group may change the coherency of groups we've previously
@@ -75,13 +91,10 @@ static void kvm_vfio_update_coherency(struct kvm_device *dev)
 	mutex_lock(&kv->lock);
 
 	list_for_each_entry(kvg, &kv->group_list, node) {
-		/*
-		 * TODO: We need an interface to check the coherency of
-		 * the IOMMU domain this group is using.  For now, assume
-		 * it's always noncoherent.
-		 */
-		noncoherent = true;
-		break;
+		if (!kvm_vfio_group_is_coherent(kvg->vfio_group)) {
+			noncoherent = true;
+			break;
+		}
 	}
 
 	if (noncoherent != kv->noncoherent) {