[PATCH 2/2] vhost: only drop vqs with built-in virtio_net.c driver

[Stefan Hajnoczi <stefanha@redhat.com>]

Commit e29109323595beb3884da58126ebb3b878cb66f5 ("vhost: destroy unused
virtqueues when multiqueue not negotiated") broke vhost-scsi by removing
virtqueues when the virtio-net-specific VIRTIO_NET_F_MQ feature bit is
missing.

The vhost_user.c code shouldn't assume all devices are vhost net device
backends.  Use the new VIRTIO_DEV_BUILTIN_VIRTIO_NET flag to check
whether virtio_net.c is being used.

This fixes examples/vhost_scsi.

Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 lib/librte_vhost/vhost_user.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index 1dd1a61b6..65ee33919 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -187,7 +187,8 @@ vhost_user_set_features(struct virtio_net *dev, uint64_t features)
 		(dev->features & (1 << VIRTIO_NET_F_MRG_RXBUF)) ? "on" : "off",
 		(dev->features & (1ULL << VIRTIO_F_VERSION_1)) ? "on" : "off");
 
-	if (!(dev->features & (1ULL << VIRTIO_NET_F_MQ))) {
+	if ((dev->flags & VIRTIO_DEV_BUILTIN_VIRTIO_NET) &&
+	    !(dev->features & (1ULL << VIRTIO_NET_F_MQ))) {
 		/*
 		 * Remove all but first queue pair if MQ hasn't been
 		 * negotiated. This is safe because the device is not
-- 
2.14.3