Add blktap2 support to xend driver

Xen4.0 includes a new blktap2 implementation, which is specified
with 'tap2' prefix.  AFAICT it's configuration syntax is identical
to blktap, with exception of 'tap2' vs 'tap' prefix.  This patch
takes the simple approach of accepting and generating sexp
containing 'tap2' prefix.

src/xen/xend_internal.c

@@ -1386,7 +1386,8 @@ xenDaemonParseSxprDisks(virDomainDefPtr def,
            but blktap disks ended up in a differently named
            (device (tap ....)) block.... */
         if (sexpr_lookup(node, "device/vbd") ||
-            sexpr_lookup(node, "device/tap")) {
+            sexpr_lookup(node, "device/tap") ||
+            sexpr_lookup(node, "device/tap2")) {
             char *offset;
             const char *src = NULL;
             const char *dst = NULL;
@@ -1397,6 +1398,10 @@ xenDaemonParseSxprDisks(virDomainDefPtr def,
                 src = sexpr_node(node, "device/vbd/uname");
                 dst = sexpr_node(node, "device/vbd/dev");
                 mode = sexpr_node(node, "device/vbd/mode");
+            } else if (sexpr_lookup(node, "device/tap2")) {
+                src = sexpr_node(node, "device/tap2/uname");
+                dst = sexpr_node(node, "device/tap2/dev");
+                mode = sexpr_node(node, "device/tap2/mode");
             } else {
                 src = sexpr_node(node, "device/tap/uname");
                 dst = sexpr_node(node, "device/tap/dev");
@@ -1444,7 +1449,8 @@ xenDaemonParseSxprDisks(virDomainDefPtr def,
 
                 src = offset + 1;
 
-                if (STREQ (disk->driverName, "tap")) {
+                if (STREQ (disk->driverName, "tap") ||
+                    STREQ (disk->driverName, "tap2")) {
                     offset = strchr(src, ':');
                     if (!offset) {
                         virXendError(VIR_ERR_INTERNAL_ERROR,
@@ -5306,9 +5312,10 @@ xenDaemonFormatSxprDisk(virConnectPtr conn ATTRIBUTE_UNUSED,
     /* Normally disks are in a (device (vbd ...)) block
      * but blktap disks ended up in a differently named
      * (device (tap ....)) block.... */
-    if (def->driverName &&
-        STREQ(def->driverName, "tap")) {
+    if (def->driverName && STREQ(def->driverName, "tap")) {
         virBufferAddLit(buf, "(tap ");
+    } else if (def->driverName && STREQ(def->driverName, "tap2")) {
+        virBufferAddLit(buf, "(tap2 ");
     } else {
         virBufferAddLit(buf, "(vbd ");
     }
@@ -5329,7 +5336,8 @@ xenDaemonFormatSxprDisk(virConnectPtr conn ATTRIBUTE_UNUSED,
 
     if (def->src) {
         if (def->driverName) {
-            if (STREQ(def->driverName, "tap")) {
+            if (STREQ(def->driverName, "tap") ||
+                STREQ(def->driverName, "tap2")) {
                 virBufferVSprintf(buf, "(uname '%s:%s:%s')",
                                   def->driverName,
                                   def->driverType ? def->driverType : "aio",
@@ -5928,6 +5936,9 @@ virDomainXMLDevID(virDomainPtr domain,
         if (dev->data.disk->driverName &&
             STREQ(dev->data.disk->driverName, "tap"))
             strcpy(class, "tap");
+        else if (dev->data.disk->driverName &&
+            STREQ(dev->data.disk->driverName, "tap2"))
+            strcpy(class, "tap2");
         else
             strcpy(class, "vbd");