Description: build: avoid testpmd only working in XEN

With LIBRTE_PMD_XENVIRT enabled testpmd is built in a way to ONLY work
in XEN environments.
It will surface as:
   PMD: gntalloc: ioctl error
   EAL: Error - exiting with code: 1
     Cause: Creation of mbuf pool for socket 0 failed

There could be a complex solution checking if this is a Xen env via
something like:
   #include <xenstore.h>
   struct xs_handle *xsh = NULL;
   xsh = xs_open(XS_OPEN_READONLY);
   check for xsh being NULL ...

But I see no reason to go so complex and instead the patch goes the
simple and more readable way of just falling back to the normal
allocation if the xen based allocation failed.

Forwarded: Yes - Accepted as bece7b6cf6849331c1817e1034c03fab251952a7
Author: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Last-Update: 2016-04-12

Index: dpdk/app/test-pmd/testpmd.c
===================================================================
--- dpdk.orig/app/test-pmd/testpmd.c
+++ dpdk/app/test-pmd/testpmd.c
@@ -410,7 +410,7 @@ mbuf_pool_create(uint16_t mbuf_seg_size,
 		 unsigned int socket_id)
 {
 	char pool_name[RTE_MEMPOOL_NAMESIZE];
-	struct rte_mempool *rte_mp;
+	struct rte_mempool *rte_mp = NULL;
 	uint32_t mb_size;
 
 	mb_size = sizeof(struct rte_mbuf) + mbuf_seg_size;
@@ -423,24 +423,23 @@ mbuf_pool_create(uint16_t mbuf_seg_size,
 		rte_pktmbuf_pool_init, NULL,
 		rte_pktmbuf_init, NULL,
 		socket_id, 0);
-
-
-
-#else
-	if (mp_anon != 0)
-		rte_mp = mempool_anon_create(pool_name, nb_mbuf, mb_size,
-				    (unsigned) mb_mempool_cache,
-				    sizeof(struct rte_pktmbuf_pool_private),
-				    rte_pktmbuf_pool_init, NULL,
-				    rte_pktmbuf_init, NULL,
-				    socket_id, 0);
-	else
-		/* wrapper to rte_mempool_create() */
-		rte_mp = rte_pktmbuf_pool_create(pool_name, nb_mbuf,
-			mb_mempool_cache, 0, mbuf_seg_size, socket_id);
-
 #endif
 
+	/* if the former XEN allocation failed fall back to normal allocation */
+	if (rte_mp == NULL) {
+		if (mp_anon != 0)
+			rte_mp = mempool_anon_create(pool_name, nb_mbuf,
+					mb_size, (unsigned) mb_mempool_cache,
+					sizeof(struct rte_pktmbuf_pool_private),
+					rte_pktmbuf_pool_init, NULL,
+					rte_pktmbuf_init, NULL,
+					socket_id, 0);
+		else
+			/* wrapper to rte_mempool_create() */
+			rte_mp = rte_pktmbuf_pool_create(pool_name, nb_mbuf,
+				mb_mempool_cache, 0, mbuf_seg_size, socket_id);
+	}
+
 	if (rte_mp == NULL) {
 		rte_exit(EXIT_FAILURE, "Creation of mbuf pool for socket %u "
 						"failed\n", socket_id);