diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index a794e47209..67b549c1f5 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -10737,12 +10737,25 @@ qemuNodeDeviceDetachFlags(virNodeDevicePtr dev,
     if (!pci)
         goto cleanup;
 
-    if (!driverName || STREQ(driverName, "kvm")) {
-        if (virPCIDeviceSetStubDriver(pci, "pci-stub") < 0)
-            goto cleanup;
+    if (!driverName) {
+        /* prefer vfio */
+        if (qemuHostdevHostSupportsPassthroughVFIO())
+            driverName = "vfio";
+        else if (qemuHostdevHostSupportsPassthroughLegacy())
+            driverName = "kvm";
+    }
+
+    if (!driverName) {
+        virReportError(VIR_ERR_INVALID_ARG, "%s",
+                       _("neither VFIO nor kvm device assignment is "
+                         "currently supported on this system"));
+        goto cleanup;
     } else if (STREQ(driverName, "vfio")) {
         if (virPCIDeviceSetStubDriver(pci, "vfio-pci") < 0)
             goto cleanup;
+    } else if (STREQ(driverName, "kvm")) {
+        if (virPCIDeviceSetStubDriver(pci, "pci-stub") < 0)
+            goto cleanup;
     } else {
         virReportError(VIR_ERR_INVALID_ARG,
                        _("unknown driver name '%s'"), driverName);
diff --git a/src/qemu/qemu_hostdev.c b/src/qemu/qemu_hostdev.c
index f5cad15cf9..dee61e742d 100644
--- a/src/qemu/qemu_hostdev.c
+++ b/src/qemu/qemu_hostdev.c
@@ -501,7 +501,7 @@ qemuDomainHostdevNetConfigRestore(virDomainHostdevDefPtr hostdev,
 }
 
 
-static bool
+bool
 qemuHostdevHostSupportsPassthroughVFIO(void)
 {
     DIR *iommuDir = NULL;
@@ -541,7 +541,7 @@ cleanup:
 
 #if HAVE_LINUX_KVM_H
 # include <linux/kvm.h>
-static bool
+bool
 qemuHostdevHostSupportsPassthroughLegacy(void)
 {
     int kvmfd = -1;
@@ -563,7 +563,7 @@ cleanup:
     return ret;
 }
 #else
-static bool
+bool
 qemuHostdevHostSupportsPassthroughLegacy(void)
 {
     return false;
diff --git a/src/qemu/qemu_hostdev.h b/src/qemu/qemu_hostdev.h
index 272086effa..ffb3167ca1 100644
--- a/src/qemu/qemu_hostdev.h
+++ b/src/qemu/qemu_hostdev.h
@@ -1,7 +1,7 @@
 /*
  * qemu_hostdev.h: QEMU hostdev management
  *
- * Copyright (C) 2006-2007, 2009-2010 Red Hat, Inc.
+ * Copyright (C) 2006-2007, 2009-2013 Red Hat, Inc.
  * Copyright (C) 2006 Daniel P. Berrange
  *
  * This library is free software; you can redistribute it and/or
@@ -33,6 +33,8 @@ int qemuUpdateActiveUsbHostdevs(virQEMUDriverPtr driver,
                                 virDomainDefPtr def);
 int qemuUpdateActiveScsiHostdevs(virQEMUDriverPtr driver,
                                  virDomainDefPtr def);
+bool qemuHostdevHostSupportsPassthroughLegacy(void);
+bool qemuHostdevHostSupportsPassthroughVFIO(void);
 int qemuPrepareHostdevPCIDevices(virQEMUDriverPtr driver,
                                  const char *name,
                                  const unsigned char *uuid,