btl/uct: fix bug when using a transport without zero-copy

This commit fixes a crash that can occur if a transport
is usable but doesn't have zero-copy support. In this
case do not attempt to use zero-copy and set the max
send size off the bcopy limit.

Signed-off-by: Nathan Hjelm <hjelmn@google.com>

opal/mca/btl/uct/btl_uct_am.c

@@ -175,7 +175,8 @@ int mca_btl_uct_send_frag (mca_btl_uct_module_t *uct_btl, mca_btl_uct_base_frag_
     if (!context->in_am_callback) {
         mca_btl_uct_context_lock (context);
         /* attempt to post the fragment */
-        if (NULL != frag->base.super.registration) {
+        if (NULL != frag->base.super.registration &&
+            (context->uct_iface_attr.cap.flags & UCT_IFACE_FLAG_AM_ZCOPY)) {
             frag->comp.dev_context = context;
             ucs_status = uct_ep_am_zcopy (ep_handle, MCA_BTL_UCT_FRAG, &frag->header, sizeof (frag->header),
                                           &frag->uct_iov, 1, 0, &frag->comp.uct_comp);

opal/mca/btl/uct/btl_uct_tl.c

@@ -461,8 +461,14 @@ static void mca_btl_uct_set_tl_am (mca_btl_uct_module_t *module, mca_btl_uct_tl_
 	tl->max_device_contexts = mca_btl_uct_component.num_contexts_per_module;
     }
 
-    module->super.btl_max_send_size = MCA_BTL_UCT_TL_ATTR(tl, 0).cap.am.max_zcopy - sizeof (mca_btl_uct_am_header_t);
-    module->super.btl_eager_limit = MCA_BTL_UCT_TL_ATTR(tl, 0).cap.am.max_bcopy - sizeof (mca_btl_uct_am_header_t);
+    module->super.btl_eager_limit = MCA_BTL_UCT_TL_ATTR(tl, 0).cap.am.max_bcopy -
+        sizeof (mca_btl_uct_am_header_t);
+    if (MCA_BTL_UCT_TL_ATTR(tl, 0).cap.flags & UCT_IFACE_FLAG_AM_ZCOPY) {
+        module->super.btl_max_send_size = MCA_BTL_UCT_TL_ATTR(tl, 0).cap.am.max_zcopy -
+            sizeof (mca_btl_uct_am_header_t);
+    } else {
+        module->super.btl_max_send_size = module->super.btl_eager_limit;
+    }
 }
 
 static int mca_btl_uct_set_tl_conn (mca_btl_uct_module_t *module, mca_btl_uct_tl_t *tl)