[dpdk-dev] [PATCH] examples/vhost: fix port init failure in mergeable mode

[Chenbo Xia <chenbo.xia@intel.com>]

When the example starts in mergeable mode with an i40e port,
it fails to launch because the examples use default mtu MAX_MTU
to configure ethdev. The root cause is some devices have Ethernet
frame overhead and then MAX_MTU will be larger than device's max
mtu, so the ethdev configure will fail.

This patch checks the device's max mtu before setting the ethdev
configuration. If the device has a max mtu, use that value to
configure.

Fixes: 1bb4a528c41f ("ethdev: fix max Rx packet length")

Signed-off-by: Chenbo Xia <chenbo.xia@intel.com>
Reported-by: Xingguang He <xingguang.he@intel.com>
---
 examples/vhost/main.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/examples/vhost/main.c b/examples/vhost/main.c
index 58e12aa710..09fb2382bf 100644
--- a/examples/vhost/main.c
+++ b/examples/vhost/main.c
@@ -273,6 +273,13 @@ port_init(uint16_t port)
 
 	tx_rings = (uint16_t)rte_lcore_count();
 
+	if (mergeable) {
+		if (dev_info.max_mtu != UINT16_MAX && dev_info.max_rx_pktlen > dev_info.max_mtu)
+			vmdq_conf_default.rxmode.mtu = dev_info.max_mtu;
+		else
+			vmdq_conf_default.rxmode.mtu = MAX_MTU;
+	}
+
 	/* Get port configuration. */
 	retval = get_eth_conf(&port_conf, num_devices);
 	if (retval < 0)
@@ -631,8 +638,6 @@ us_vhost_parse_args(int argc, char **argv)
 				return -1;
 			}
 			mergeable = !!ret;
-			if (ret)
-				vmdq_conf_default.rxmode.mtu = MAX_MTU;
 			break;
 
 		case OPT_STATS_NUM:
-- 
2.17.1