This reverts commit 
04d81227960b ("vhost: workaround MQ fails to
startup").
As agreed when this workaround was introduced, it can be reverted
as Qemu v2.10 that fixes the issue is now out.
The reply-ack feature is required for vhost-user IOMMU support.
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Yuanhan Liu <yliu@fridaylinux.org>
 
 #define VHOST_USER_PROTOCOL_F_REPLY_ACK        3
 #define VHOST_USER_PROTOCOL_F_NET_MTU 4
 
-/*
- * disable REPLY_ACK feature to workaround the buggy QEMU implementation.
- * Proved buggy QEMU includes v2.7 - v2.9.
- */
 #define VHOST_USER_PROTOCOL_FEATURES   ((1ULL << VHOST_USER_PROTOCOL_F_MQ) | \
                                         (1ULL << VHOST_USER_PROTOCOL_F_LOG_SHMFD) |\
                                         (1ULL << VHOST_USER_PROTOCOL_F_RARP) | \
-                                        (0ULL << VHOST_USER_PROTOCOL_F_REPLY_ACK) | \
+                                        (1ULL << VHOST_USER_PROTOCOL_F_REPLY_ACK) | \
                                         (1ULL << VHOST_USER_PROTOCOL_F_NET_MTU))
 
 typedef enum VhostUserRequest {