selftests/bpf: Fix xdpxceiver failures for no hugepages

xsk_configure_umem() needs hugepages to work in unaligned mode. So when
hugepages are not configured, 'unaligned' tests should be skipped which
is determined by the helper function hugepages_present(). This function
erroneously returns true with MAP_NORESERVE flag even when no hugepages
are configured. The removal of this flag fixes the issue.

The test TEST_TYPE_UNALIGNED_INV_DESC also needs to be skipped when
there are no hugepages. However, this was not skipped as there was no
check for presence of hugepages and hence was failing. The check to skip
the test has now been added.

Fixes: a4ba98dd (selftests: xsk: Add test for unaligned mode)
Signed-off-by: NTirthendu Sarkar <tirthendu.sarkar@intel.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211117123613.22288-1-tirthendu.sarkar@intel.com

tools/testing/selftests/bpf/xdpxceiver.c

@@ -1217,7 +1217,7 @@ static bool hugepages_present(struct ifobject *ifobject)
 	void *bufs;
 
 	bufs = mmap(NULL, mmap_sz, PROT_READ | PROT_WRITE,
-		    MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE | MAP_HUGETLB, -1, 0);
+		    MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);
 	if (bufs == MAP_FAILED)
 		return false;
 
@@ -1364,6 +1364,10 @@ static void run_pkt_test(struct test_spec *test, enum test_mode mode, enum test_
 		testapp_invalid_desc(test);
 		break;
 	case TEST_TYPE_UNALIGNED_INV_DESC:
+		if (!hugepages_present(test->ifobj_tx)) {
+			ksft_test_result_skip("No 2M huge pages present.\n");
+			return;
+		}
 		test_spec_set_name(test, "UNALIGNED_INV_DESC");
 		test->ifobj_tx->umem->unaligned_mode = true;
 		test->ifobj_rx->umem->unaligned_mode = true;