[dpdk-dev] [PATCH v7 5/8] virtio: fix deadloop due to reading virtio_net_config incorrectly

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

From: Changchun Ouyang <changchun.ouyang@intel.com>

The old code adjusts the config bytes we want to read depending on
what kind of features we have, but we later cast the entire buf we
read with "struct virtio_net_config", which is obviously wrong.

The wrong config reading results to a dead loop at virtio_send_command()
while starting testpmd.

The right way to go is to read related config bytes when corresponding
feature is set, which is exactly what this patch does.

Fixes: 823ad647950a ("virtio: support multiple queues")

Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Acked-by: Flavio Leitner <fbl@sysclose.org>

---

v7: commit log fixes

v6: read mac unconditionally.
---
 drivers/net/virtio/virtio_ethdev.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index 147aca1..a654168 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -1163,7 +1163,6 @@ eth_virtio_dev_init(struct rte_eth_dev *eth_dev)
 	struct virtio_hw *hw = eth_dev->data->dev_private;
 	struct virtio_net_config *config;
 	struct virtio_net_config local_config;
-	uint32_t offset_conf = sizeof(config->mac);
 	struct rte_pci_device *pci_dev;
 
 	RTE_BUILD_BUG_ON(RTE_PKTMBUF_HEADROOM < sizeof(struct virtio_net_hdr));
@@ -1222,8 +1221,14 @@ eth_virtio_dev_init(struct rte_eth_dev *eth_dev)
 	if (vtpci_with_feature(hw, VIRTIO_NET_F_CTRL_VQ)) {
 		config = &local_config;
 
+		vtpci_read_dev_config(hw,
+			offsetof(struct virtio_net_config, mac),
+			&config->mac, sizeof(config->mac));
+
 		if (vtpci_with_feature(hw, VIRTIO_NET_F_STATUS)) {
-			offset_conf += sizeof(config->status);
+			vtpci_read_dev_config(hw,
+				offsetof(struct virtio_net_config, status),
+				&config->status, sizeof(config->status));
 		} else {
 			PMD_INIT_LOG(DEBUG,
 				     "VIRTIO_NET_F_STATUS is not supported");
@@ -1231,15 +1236,16 @@ eth_virtio_dev_init(struct rte_eth_dev *eth_dev)
 		}
 
 		if (vtpci_with_feature(hw, VIRTIO_NET_F_MQ)) {
-			offset_conf += sizeof(config->max_virtqueue_pairs);
+			vtpci_read_dev_config(hw,
+				offsetof(struct virtio_net_config, max_virtqueue_pairs),
+				&config->max_virtqueue_pairs,
+				sizeof(config->max_virtqueue_pairs));
 		} else {
 			PMD_INIT_LOG(DEBUG,
 				     "VIRTIO_NET_F_MQ is not supported");
 			config->max_virtqueue_pairs = 1;
 		}
 
-		vtpci_read_dev_config(hw, 0, (uint8_t *)config, offset_conf);
-
 		hw->max_rx_queues =
 			(VIRTIO_MAX_RX_QUEUES < config->max_virtqueue_pairs) ?
 			VIRTIO_MAX_RX_QUEUES : config->max_virtqueue_pairs;
-- 
1.9.0