From: Stephen Hemminger <shemming@brocade.com>
Date: Thu, 11 Jun 2015 15:53:27 +0000 (-0700)
Subject: virtio: fix ring size negotiation
X-Git-Tag: spdx-start~9117
X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=d78deadae4dca240e85054bf2d604a801676becc;p=dpdk.git

virtio: fix ring size negotiation

Negotiate the virtio ring size. The host may allow for very large
rings but application may only want a smaller ring.
Conversely, if the number of descriptors requested exceeds the virtio
host queue size, then just silently use the smaller host size.

This fixes issues with virtio in non-QEMU envirionments.
For example Google Compute Engine allows up to 16K elements
in ring.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Changchun Ouyang <changchun.ouyang@intel.com>
---

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index b18e54137d..a71aaa0011 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -267,13 +267,21 @@ int virtio_dev_queue_setup(struct rte_eth_dev *dev,
 	if (vq_size == 0) {
 		PMD_INIT_LOG(ERR, "%s: virtqueue does not exist", __func__);
 		return -EINVAL;
-	} else if (!rte_is_power_of_2(vq_size)) {
+	}
+
+	if (!rte_is_power_of_2(vq_size)) {
 		PMD_INIT_LOG(ERR, "%s: virtqueue size is not powerof 2", __func__);
 		return -EINVAL;
-	} else if (nb_desc != vq_size) {
-		PMD_INIT_LOG(ERR, "Warning: nb_desc(%d) is not equal to vq size (%d), fall to vq size",
-			nb_desc, vq_size);
-		nb_desc = vq_size;
+	}
+
+	if (nb_desc < vq_size) {
+		if (!rte_is_power_of_2(nb_desc)) {
+			PMD_INIT_LOG(ERR,
+				     "nb_desc(%u) size is not powerof 2",
+				     nb_desc);
+			return -EINVAL;
+		}
+		vq_size = nb_desc;
 	}
 
 	if (queue_type == VTNET_RQ) {