[dpdk-dev] [PATCH] vhost: fix build error on old kernel doesn't support MQ

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

Fix build error:

  virtio-net.c:80:89: error: ‘VIRTIO_NET_F_MQ’ undeclared here
  rte_virtio_net.h:109: error: ‘VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX’ undeclared here

Above two virtio-net MQ macros are introduced since kernel v3.8.
For older kernel, we should not reference them directly, hence,
this patch introduced two wrapper macros, with proper values
being set depending on we support MQ or not.

Fixes: 19d4d7ef2a21 ("vhost-user: enable multiple queue")

Reported-by: Gu YongjieX <yongjiex.gu@intel.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
---
 lib/librte_vhost/rte_virtio_net.h            | 17 ++++++++++++++++-
 lib/librte_vhost/vhost_user/vhost-net-user.c |  2 +-
 lib/librte_vhost/virtio-net.c                |  2 +-
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
index 426a70d..b6386f9 100644
--- a/lib/librte_vhost/rte_virtio_net.h
+++ b/lib/librte_vhost/rte_virtio_net.h
@@ -93,6 +93,21 @@ struct vhost_virtqueue {
 	struct buf_vector	buf_vec[BUF_VECTOR_MAX];	/**< for scatter RX. */
 } __rte_cache_aligned;
 
+
+/*
+ * Make an extra wrapper for VIRTIO_NET_F_MQ and
+ * VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX as they are
+ * introduced since kernel v3.8. This makes our
+ * code buildable for older kernel.
+ */
+#ifdef VIRTIO_NET_F_MQ
+ #define VHOST_MAX_QUEUE_PAIRS	VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX
+ #define VHOST_SUPPORTS_MQ	(1ULL << VIRTIO_NET_F_MQ)
+#else
+ #define VHOST_MAX_QUEUE_PAIRS	1
+ #define VHOST_SUPPORTS_MQ	0
+#endif
+
 /**
  * Device structure contains all configuration information relating to the device.
  */
@@ -106,7 +121,7 @@ struct virtio_net {
 	char			ifname[IF_NAME_SZ];	/**< Name of the tap device or socket path. */
 	uint32_t		virt_qp_nb;	/**< number of queue pair we have allocated */
 	void			*priv;		/**< private context */
-	struct vhost_virtqueue	*virtqueue[VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX];	/**< Contains all virtqueue information. */
+	struct vhost_virtqueue	*virtqueue[VHOST_MAX_QUEUE_PAIRS * 2];	/**< Contains all virtqueue information. */
 } __rte_cache_aligned;
 
 /**
diff --git a/lib/librte_vhost/vhost_user/vhost-net-user.c b/lib/librte_vhost/vhost_user/vhost-net-user.c
index f681676..2dc0547 100644
--- a/lib/librte_vhost/vhost_user/vhost-net-user.c
+++ b/lib/librte_vhost/vhost_user/vhost-net-user.c
@@ -424,7 +424,7 @@ vserver_message_handler(int connfd, void *dat, int *remove)
 		break;
 
 	case VHOST_USER_GET_QUEUE_NUM:
-		msg.payload.u64 = VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX;
+		msg.payload.u64 = VHOST_MAX_QUEUE_PAIRS;
 		msg.size = sizeof(msg.payload.u64);
 		send_vhost_message(connfd, &msg);
 		break;
diff --git a/lib/librte_vhost/virtio-net.c b/lib/librte_vhost/virtio-net.c
index 97213c5..3e82605 100644
--- a/lib/librte_vhost/virtio-net.c
+++ b/lib/librte_vhost/virtio-net.c
@@ -74,7 +74,7 @@ static struct virtio_net_config_ll *ll_root;
 #define VHOST_SUPPORTED_FEATURES ((1ULL << VIRTIO_NET_F_MRG_RXBUF) | \
 				(1ULL << VIRTIO_NET_F_CTRL_VQ) | \
 				(1ULL << VIRTIO_NET_F_CTRL_RX) | \
-				(1ULL << VIRTIO_NET_F_MQ)      | \
+				(VHOST_SUPPORTS_MQ)            | \
 				(1ULL << VHOST_F_LOG_ALL)      | \
 				(1ULL << VHOST_USER_F_PROTOCOL_FEATURES))
 static uint64_t VHOST_FEATURES = VHOST_SUPPORTED_FEATURES;
-- 
1.9.0