diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 1905d6f85d5b933240f019f6d19223398c5b98b2..4c4a9bd08b24153ef7deba954d33e0fb854275a8 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1428,8 +1428,11 @@ virNetDevVethDelete;
 
 # virnetdevvportprofile.h
 virNetDevVPortProfileAssociate;
+virNetDevVPortProfileCheckComplete;
+virNetDevVPortProfileCheckNoExtras;
 virNetDevVPortProfileDisassociate;
 virNetDevVPortProfileEqual;
+virNetDevVPortProfileMerge3;
 virNetDevVPortProfileOpTypeFromString;
 virNetDevVPortProfileOpTypeToString;
 
diff --git a/src/util/virnetdevvportprofile.c b/src/util/virnetdevvportprofile.c
index 6db04f7f117176bbeb92668532595a761e687bfa..e686fd961b3b6b6aabea2c3685e889751a3e689a 100644
--- a/src/util/virnetdevvportprofile.c
+++ b/src/util/virnetdevvportprofile.c
@@ -120,6 +120,319 @@ virNetDevVPortProfileEqual(virNetDevVPortProfilePtr a, virNetDevVPortProfilePtr
     return true;
 }
 
+/* virNetDevVPortProfileCheckComplete() checks that all attributes
+ * required for the type of virtport are specified. When
+ * generateMissing is true, any missing attribute that can be
+ * autogenerated, will be (instanceid, interfaceid). If virtport ==
+ * NULL or virtPortType == NONE, then the result is always 0
+ * (success). If a required attribute is missing, an error is logged
+ * and -1 is returned.
+ */
+int
+virNetDevVPortProfileCheckComplete(virNetDevVPortProfilePtr virtport,
+                                   bool generateMissing)
+{
+    const char *missing = NULL;
+
+    if (!virtport || virtport->virtPortType == VIR_NETDEV_VPORT_PROFILE_NONE)
+        return 0;
+
+    switch (virtport->virtPortType) {
+    case VIR_NETDEV_VPORT_PROFILE_8021QBG:
+        if (!virtport->managerID_specified) {
+            missing = "managerid";
+        } else if (!virtport->typeID_specified) {
+            missing = "typeid";
+        } else if (!virtport->typeIDVersion_specified) {
+            missing = "typeidversion";
+        } else if (!virtport->instanceID_specified) {
+            if (generateMissing) {
+                if (virUUIDGenerate(virtport->instanceID) < 0) {
+                    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                                   _("cannot generate a random uuid for instanceid"));
+                    return -1;
+                }
+                virtport->instanceID_specified = true;
+            } else {
+                missing = "instanceid";
+            }
+        }
+        break;
+
+    case VIR_NETDEV_VPORT_PROFILE_8021QBH:
+        if (!virtport->profileID[0])
+            missing = "profileid";
+        break;
+
+    case VIR_NETDEV_VPORT_PROFILE_OPENVSWITCH:
+        /* profileid is optional for openvswitch */
+        if (!virtport->interfaceID_specified) {
+            if (generateMissing) {
+                if (virUUIDGenerate(virtport->interfaceID) < 0) {
+                    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                                   _("cannot generate a random uuid for interfaceid"));
+                    return -1;
+                }
+                virtport->interfaceID_specified = true;
+            } else {
+                missing = "interfaceid";
+            }
+        }
+        break;
+    }
+
+    if (missing) {
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("missing %s in <virtualport type='%s'>"), missing,
+                       virNetDevVPortTypeToString(virtport->virtPortType));
+        return -1;
+    }
+
+    return 0;
+}
+
+/* virNetDevVPortProfileCheckNoExtras() checks that there are no
+ * attributes specified in this virtport that are inappropriate for
+ * the type. if virtport == NULL or virtPortType == NONE, then the
+ * result is always 0 (success). If an extra attribute is present,
+ * an error is logged and -1 is returned.
+ */
+int
+virNetDevVPortProfileCheckNoExtras(virNetDevVPortProfilePtr virtport)
+{
+    const char *extra = NULL;
+
+    if (!virtport || virtport->virtPortType == VIR_NETDEV_VPORT_PROFILE_NONE)
+        return 0;
+
+    switch (virtport->virtPortType) {
+    case VIR_NETDEV_VPORT_PROFILE_8021QBG:
+        if (virtport->profileID[0])
+            extra = "profileid";
+        else if (virtport->interfaceID_specified)
+            extra = "interfaceid";
+        break;
+
+    case VIR_NETDEV_VPORT_PROFILE_8021QBH:
+        if (virtport->managerID_specified)
+            extra = "managerid";
+        else if (virtport->typeID_specified)
+            extra = "typeid";
+        else if (virtport->typeIDVersion_specified)
+            extra = "typeidversion";
+        else if (virtport->instanceID_specified)
+            extra = "instanceid";
+        else if (virtport->interfaceID_specified)
+            extra = "interfaceid";
+        break;
+
+    case VIR_NETDEV_VPORT_PROFILE_OPENVSWITCH:
+        if (virtport->managerID_specified)
+            extra = "managerid";
+        else if (virtport->typeID_specified)
+            extra = "typeid";
+        else if (virtport->typeIDVersion_specified)
+            extra = "typeidversion";
+        else if (virtport->instanceID_specified)
+            extra = "instanceid";
+        break;
+    }
+
+    if (extra) {
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("extra %s unsupported in <virtualport type='%s'>"),
+                       extra,
+                       virNetDevVPortTypeToString(virtport->virtPortType));
+        return -1;
+    }
+
+    return 0;
+}
+
+/* virNetDevVPortProfileMerge() - merge the attributes in mods into
+ * orig. If anything that is set in mods has already been set in orig
+ * *and doesn't match*, log an error and return -1, otherwise return 0.
+ */
+static int
+virNetDevVPortProfileMerge(virNetDevVPortProfilePtr orig,
+                           virNetDevVPortProfilePtr mods)
+{
+    enum virNetDevVPortProfile otype;
+
+    if (!orig || !mods)
+        return 0;
+
+    otype = orig->virtPortType;
+
+    if (mods->virtPortType != VIR_NETDEV_VPORT_PROFILE_NONE) {
+        if (otype != VIR_NETDEV_VPORT_PROFILE_NONE &&
+            otype != mods->virtPortType) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("attempt to merge virtualports "
+                             "with mismatched types (%s and %s)"),
+                           virNetDevVPortTypeToString(otype),
+                           virNetDevVPortTypeToString(mods->virtPortType));
+            return -1;
+        }
+        otype = orig->virtPortType = mods->virtPortType;
+    }
+
+    if (mods->managerID_specified &&
+        (otype == VIR_NETDEV_VPORT_PROFILE_8021QBG ||
+         otype == VIR_NETDEV_VPORT_PROFILE_NONE)) {
+        if (orig->managerID_specified &&
+            (orig->managerID != mods->managerID)) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("attempt to merge virtualports "
+                             "with mismatched managerids (%d and %d)"),
+                           orig->managerID, mods->managerID);
+            return -1;
+        }
+        orig->managerID = mods->managerID;
+        orig->managerID_specified = true;
+    }
+
+    if (mods->typeID_specified &&
+        (otype == VIR_NETDEV_VPORT_PROFILE_8021QBG ||
+         otype == VIR_NETDEV_VPORT_PROFILE_NONE)) {
+        if (orig->typeID_specified &&
+            (orig->typeID != mods->typeID)) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("attempt to merge virtualports "
+                             "with mismatched typeids (%d and %d)"),
+                           orig->typeID, mods->typeID);
+            return -1;
+        }
+        orig->typeID = mods->typeID;
+        orig->typeID_specified = true;
+    }
+
+    if (mods->typeIDVersion_specified &&
+        (otype == VIR_NETDEV_VPORT_PROFILE_8021QBG ||
+         otype == VIR_NETDEV_VPORT_PROFILE_NONE)) {
+        if (orig->typeIDVersion_specified &&
+            (orig->typeIDVersion != mods->typeIDVersion)) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("attempt to merge virtualports with "
+                             "mismatched typeidversions (%d and %d)"),
+                           orig->typeIDVersion, mods->typeIDVersion);
+            return -1;
+        }
+        orig->typeIDVersion = mods->typeIDVersion;
+        orig->typeIDVersion_specified = true;
+    }
+
+    if (mods->instanceID_specified &&
+        (otype == VIR_NETDEV_VPORT_PROFILE_8021QBG ||
+         otype == VIR_NETDEV_VPORT_PROFILE_NONE)) {
+        if (orig->instanceID_specified &&
+            memcmp(orig->instanceID, mods->instanceID,
+                   sizeof(orig->instanceID))) {
+            char origuuid[VIR_UUID_STRING_BUFLEN];
+            char modsuuid[VIR_UUID_STRING_BUFLEN];
+
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("attempt to merge virtualports with "
+                             "mismatched instanceids ('%s' and '%s')"),
+                           virUUIDFormat(orig->instanceID, origuuid),
+                           virUUIDFormat(mods->instanceID, modsuuid));
+            return -1;
+        }
+        memcpy(orig->instanceID, mods->instanceID, sizeof(orig->instanceID));
+        orig->instanceID_specified = true;
+    }
+
+    if (mods->interfaceID_specified &&
+        (otype == VIR_NETDEV_VPORT_PROFILE_OPENVSWITCH ||
+         otype == VIR_NETDEV_VPORT_PROFILE_NONE)) {
+        if (orig->interfaceID_specified &&
+            memcmp(orig->interfaceID, mods->interfaceID,
+                   sizeof(orig->interfaceID))) {
+            char origuuid[VIR_UUID_STRING_BUFLEN];
+            char modsuuid[VIR_UUID_STRING_BUFLEN];
+
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("attempt to merge virtualports with "
+                             "mismatched interfaceids ('%s' and '%s')"),
+                           virUUIDFormat(orig->interfaceID, origuuid),
+                           virUUIDFormat(mods->interfaceID, modsuuid));
+            return -1;
+        }
+        memcpy(orig->interfaceID, mods->interfaceID, sizeof(orig->interfaceID));
+        orig->interfaceID_specified = true;
+    }
+
+    if (mods->profileID[0] &&
+        (otype == VIR_NETDEV_VPORT_PROFILE_OPENVSWITCH ||
+         otype == VIR_NETDEV_VPORT_PROFILE_8021QBH ||
+         otype == VIR_NETDEV_VPORT_PROFILE_NONE)) {
+        if (orig->profileID[0] &&
+            STRNEQ(orig->profileID, mods->profileID)) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("attempt to merge virtualports with "
+                             "mismatched profileids ('%s' and '%s')"),
+                           orig->profileID, mods->profileID);
+            return -1;
+        }
+        if (virStrcpyStatic(orig->profileID, mods->profileID)) {
+            /* this should never happen - it indicates mods->profileID
+             * isn't properly null terminated. */
+            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                           _("corrupted profileid string"));
+            return -1;
+        }
+    }
+    return 0;
+}
+
+/* virNetDevVPortProfileMerge3() - create a new virNetDevVPortProfile
+ * that is a combination of the three input profiles. fromInterface is
+ * highest priority and fromPortgroup is lowest. As lower priority
+ * objects' attributes are merged in, if the attribute is unset in the
+ * result object, it is set from the lower priority object, but if it
+ * is already set in the result and the lower priority object wants to
+ * change it, that is an error.
+ */
+
+int virNetDevVPortProfileMerge3(virNetDevVPortProfilePtr *result,
+                                virNetDevVPortProfilePtr fromInterface,
+                                virNetDevVPortProfilePtr fromNetwork,
+                                virNetDevVPortProfilePtr fromPortgroup)
+{
+    int ret = -1;
+    *result = NULL;
+
+    if ((!fromInterface || (fromInterface->virtPortType == VIR_NETDEV_VPORT_PROFILE_NONE)) &&
+        (!fromNetwork   || (fromNetwork->virtPortType   == VIR_NETDEV_VPORT_PROFILE_NONE)) &&
+        (!fromPortgroup || (fromPortgroup->virtPortType == VIR_NETDEV_VPORT_PROFILE_NONE))) {
+        return 0;
+    }
+
+    /* at least one of the source profiles is non-empty */
+    if (VIR_ALLOC(*result) < 0) {
+        virReportOOMError();
+        return ret;
+    }
+
+    /* start with the interface's profile. There are no pointers in a
+     * virtualPortProfile, so a shallow copy is sufficient.
+     */
+    if (fromInterface)
+        **result = *fromInterface;
+
+    if (virNetDevVPortProfileMerge(*result, fromNetwork) < 0)
+        goto error;
+    if (virNetDevVPortProfileMerge(*result, fromPortgroup) < 0)
+        goto error;
+
+    ret = 0;
+
+error:
+    if (ret < 0)
+        VIR_FREE(*result);
+    return ret;
+}
+
 
 #if WITH_VIRTUALPORT
 
diff --git a/src/util/virnetdevvportprofile.h b/src/util/virnetdevvportprofile.h
index 3c16bfed843146895b33402f9251303bf80cc56c..d23c284202a236507ce7b1baa9a856a6c0eaf949 100644
--- a/src/util/virnetdevvportprofile.h
+++ b/src/util/virnetdevvportprofile.h
@@ -58,18 +58,24 @@ VIR_ENUM_DECL(virNetDevVPortProfileOp)
 typedef struct _virNetDevVPortProfile virNetDevVPortProfile;
 typedef virNetDevVPortProfile *virNetDevVPortProfilePtr;
 struct _virNetDevVPortProfile {
-    enum virNetDevVPortProfile   virtPortType;
+    int           virtPortType; /* enum virNetDevVPortProfile */
     /* these members are used when virtPortType == 802.1Qbg */
     uint8_t       managerID;
+    bool          managerID_specified;
     uint32_t      typeID; /* 24 bit valid */
+    bool          typeID_specified;
     uint8_t       typeIDVersion;
+    bool          typeIDVersion_specified;
     unsigned char instanceID[VIR_UUID_BUFLEN];
+    bool          instanceID_specified;
 
     /* this member is used when virtPortType == 802.1Qbh|openvswitch */
+    /* this is a null-terminated character string */
     char          profileID[LIBVIRT_IFLA_VF_PORT_PROFILE_MAX];
 
     /* this member is used when virtPortType == openvswitch */
     unsigned char interfaceID[VIR_UUID_BUFLEN];
+    bool          interfaceID_specified;
     /* NB - if virtPortType == NONE, any/all of the items could be used */
 };
 
@@ -77,6 +83,15 @@ struct _virNetDevVPortProfile {
 bool virNetDevVPortProfileEqual(virNetDevVPortProfilePtr a,
                                 virNetDevVPortProfilePtr b);
 
+int virNetDevVPortProfileCheckComplete(virNetDevVPortProfilePtr virtport,
+                                       bool generateMissing);
+int virNetDevVPortProfileCheckNoExtras(virNetDevVPortProfilePtr virtport);
+
+int virNetDevVPortProfileMerge3(virNetDevVPortProfilePtr *result,
+                                virNetDevVPortProfilePtr fromInterface,
+                                virNetDevVPortProfilePtr fromNetwork,
+                                virNetDevVPortProfilePtr fromPortgroup);
+
 int virNetDevVPortProfileAssociate(const char *ifname,
                                    const virNetDevVPortProfilePtr virtPort,
                                    const virMacAddrPtr macaddr,