[dpdk-stable] [PATCH v2] net/virtio-user: fix advertising of protocol features

[Olivier Matz <olivier.matz@6wind.com>]

When connected to a vhost-user backend, the flag
VHOST_USER_F_PROTOCOL_FEATURES is not advertised, preventing to do
multiqueue (the VHOST_USER_PROTOCOL_F_MQ protocol feature is ignored by
some backends if the VHOST_USER_F_PROTOCOL_FEATURES feature is not set).

When setting vhost-user features, advertise this flag if it was
advertised by our peer.

Fixes: 8e7561054ac7 ("net/virtio: support vhost-user protocol features")
Cc: stable@dpdk.org

Suggested-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
---

v2
* fix obvious fallthrough case, sorry for the noise

 drivers/net/virtio/virtio_user/vhost_user.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio/virtio_user/vhost_user.c b/drivers/net/virtio/virtio_user/vhost_user.c
index b93e65c60b..350eed4182 100644
--- a/drivers/net/virtio/virtio_user/vhost_user.c
+++ b/drivers/net/virtio/virtio_user/vhost_user.c
@@ -297,13 +297,18 @@ vhost_user_sock(struct virtio_user_dev *dev,
 		if (has_reply_ack)
 			msg.flags |= VHOST_USER_NEED_REPLY_MASK;
 		/* Fallthrough */
-	case VHOST_USER_SET_FEATURES:
 	case VHOST_USER_SET_PROTOCOL_FEATURES:
 	case VHOST_USER_SET_LOG_BASE:
 		msg.payload.u64 = *((__u64 *)arg);
 		msg.size = sizeof(m.payload.u64);
 		break;
 
+	case VHOST_USER_SET_FEATURES:
+		msg.payload.u64 = *((__u64 *)arg) | (dev->device_features &
+			(1ULL << VHOST_USER_F_PROTOCOL_FEATURES));
+		msg.size = sizeof(m.payload.u64);
+		break;
+
 	case VHOST_USER_SET_OWNER:
 	case VHOST_USER_RESET_OWNER:
 		break;
-- 
2.25.1