[dpdk-dev] [PATCH] vhost: fix external backends readiness

[Maxime Coquelin <maxime.coquelin@redhat.com>]

Commit d0fcc38f5fa4 ("vhost: improve device readiness notifications")
makes the assumption that every Virtio devices are considered
ready for preocessing as soon as first queue pair is configured
and enabled.

While this is true for Virtio-net, it isn't for Virtio-scsi
and Virtio-blk.

This patch fixes this by only making this assumption for
the builtin Virtio-net backend, and restores back to previous
behaviour for other backends.

Fixes: d0fcc38f5fa4 ("vhost: improve device readiness notifications")

Reported-by: Changpeng Liu <changpeng.liu@intel.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
---
 lib/librte_vhost/vhost_user.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index 501218e192..b00e1f91dc 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -1343,21 +1343,28 @@ vq_is_ready(struct virtio_net *dev, struct vhost_virtqueue *vq)
 	       vq->enabled;
 }
 
-#define VIRTIO_DEV_NUM_VQS_TO_BE_READY 2u
+#define VIRTIO_BUILTIN_NUM_VQS_TO_BE_READY 2u
 
 static int
 virtio_is_ready(struct virtio_net *dev)
 {
 	struct vhost_virtqueue *vq;
-	uint32_t i;
+	uint32_t i, nr_vring = dev->nr_vring;
 
 	if (dev->flags & VIRTIO_DEV_READY)
 		return 1;
 
-	if (dev->nr_vring < VIRTIO_DEV_NUM_VQS_TO_BE_READY)
+	if (!dev->nr_vring)
 		return 0;
 
-	for (i = 0; i < VIRTIO_DEV_NUM_VQS_TO_BE_READY; i++) {
+	if (dev->flags & VIRTIO_DEV_BUILTIN_VIRTIO_NET) {
+		nr_vring = VIRTIO_BUILTIN_NUM_VQS_TO_BE_READY;
+
+		if (dev->nr_vring < nr_vring)
+			return 0;
+	}
+
+	for (i = 0; i < nr_vring; i++) {
 		vq = dev->virtqueue[i];
 
 		if (!vq_is_ready(dev, vq))
-- 
2.26.2