[dpdk-stable] [17.11] net/virtio-user: do not reset owner when driver resets

[Yahui Cao <yahui.cao@intel.com>]

[ backported from upstream commit 74dc6746a0f195907ec487df7de18a856108482f ]

When driver resets the device, virtio-user just needs to send
GET_VRING_BASE messages to stop the vhost backend, and that's
what QEMU does. With this change, we won't need to set owner
when starting virtio-user device anymore. This will help us to
get rid of below error message on startup:

vhost_kernel_ioctl(): VHOST_SET_OWNER failed: Device or resource busy

Fixes: bce7e9050f9b ("net/virtio-user: fix start with kernel vhost")
Fixes: 0d6a8752ac9d ("net/virtio-user: fix crash as features change")

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Signed-off-by: Yahui Cao <yahui.cao@intel.com>
---
 .../net/virtio/virtio_user/virtio_user_dev.c   | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c b/drivers/net/virtio/virtio_user/virtio_user_dev.c
index 7ce512c76..b13e77f5f 100644
--- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
+++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
@@ -166,17 +166,27 @@ virtio_user_start_device(struct virtio_user_dev *dev)
 
 int virtio_user_stop_device(struct virtio_user_dev *dev)
 {
+	struct vhost_vring_state state;
 	uint32_t i;
+	int error = 0;
 
 	for (i = 0; i < dev->max_queue_pairs; ++i)
 		dev->ops->enable_qp(dev, i, 0);
 
-	if (dev->ops->send_request(dev, VHOST_USER_RESET_OWNER, NULL) < 0) {
-		PMD_DRV_LOG(INFO, "Failed to reset the device\n");
-		return -1;
+	/* Stop the backend. */
+	for (i = 0; i < dev->max_queue_pairs * 2; ++i) {
+		state.index = i;
+		if (dev->ops->send_request(dev, VHOST_USER_GET_VRING_BASE,
+					   &state) < 0) {
+			PMD_DRV_LOG(ERR, "get_vring_base failed, index=%u\n",
+				    i);
+			error = -1;
+			goto out;
+		}
 	}
 
-	return 0;
+out:
+	return error;
 }
 
 static inline void
-- 
2.17.1