diff --git a/contrib-libvhost-user-Protect-slave-fd-with-mutex.patch b/contrib-libvhost-user-Protect-slave-fd-with-mutex.patch
new file mode 100644
index 0000000..44fc428
--- /dev/null
+++ b/contrib-libvhost-user-Protect-slave-fd-with-mutex.patch
@@ -0,0 +1,121 @@
+From f076af734a5964c3e48b2d223130f855b86f40e5 Mon Sep 17 00:00:00 2001
+From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
+Date: Fri, 1 Mar 2019 11:18:30 +0000
+Subject: [PATCH] contrib/libvhost-user: Protect slave fd with mutex
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+In future patches we'll be performing commands on the slave-fd driven
+by commands on queues, since those queues will be driven by individual
+threads we need to make sure they don't attempt to use the slave-fd
+for multiple commands in parallel.
+
+Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
+Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
+Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
+---
+ contrib/libvhost-user/libvhost-user.c | 24 ++++++++++++++++++++----
+ contrib/libvhost-user/libvhost-user.h |  3 +++
+ 2 files changed, 23 insertions(+), 4 deletions(-)
+
+diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
+index cb5f5770e4..fb75837032 100644
+--- a/contrib/libvhost-user/libvhost-user.c
++++ b/contrib/libvhost-user/libvhost-user.c
+@@ -387,26 +387,37 @@ vu_send_reply(VuDev *dev, int conn_fd, VhostUserMsg *vmsg)
+     return vu_message_write(dev, conn_fd, vmsg);
+ }
+ 
++/*
++ * Processes a reply on the slave channel.
++ * Entered with slave_mutex held and releases it before exit.
++ * Returns true on success.
++ */
+ static bool
+ vu_process_message_reply(VuDev *dev, const VhostUserMsg *vmsg)
+ {
+     VhostUserMsg msg_reply;
++    bool result = false;
+ 
+     if ((vmsg->flags & VHOST_USER_NEED_REPLY_MASK) == 0) {
+-        return true;
++        result = true;
++        goto out;
+     }
+ 
+     if (!vu_message_read(dev, dev->slave_fd, &msg_reply)) {
+-        return false;
++        goto out;
+     }
+ 
+     if (msg_reply.request != vmsg->request) {
+         DPRINT("Received unexpected msg type. Expected %d received %d",
+                vmsg->request, msg_reply.request);
+-        return false;
++        goto out;
+     }
+ 
+-    return msg_reply.payload.u64 == 0;
++    result = msg_reply.payload.u64 == 0;
++
++out:
++    pthread_mutex_unlock(&dev->slave_mutex);
++    return result;
+ }
+ 
+ /* Kick the log_call_fd if required. */
+@@ -1102,10 +1113,13 @@ bool vu_set_queue_host_notifier(VuDev *dev, VuVirtq *vq, int fd,
+         return false;
+     }
+ 
++    pthread_mutex_lock(&dev->slave_mutex);
+     if (!vu_message_write(dev, dev->slave_fd, &vmsg)) {
++        pthread_mutex_unlock(&dev->slave_mutex);
+         return false;
+     }
+ 
++    /* Also unlocks the slave_mutex */
+     return vu_process_message_reply(dev, &vmsg);
+ }
+ 
+@@ -1625,6 +1639,7 @@ vu_deinit(VuDev *dev)
+         close(dev->slave_fd);
+         dev->slave_fd = -1;
+     }
++    pthread_mutex_destroy(&dev->slave_mutex);
+ 
+     if (dev->sock != -1) {
+         close(dev->sock);
+@@ -1660,6 +1675,7 @@ vu_init(VuDev *dev,
+     dev->remove_watch = remove_watch;
+     dev->iface = iface;
+     dev->log_call_fd = -1;
++    pthread_mutex_init(&dev->slave_mutex, NULL);
+     dev->slave_fd = -1;
+     dev->max_queues = max_queues;
+ 
+diff --git a/contrib/libvhost-user/libvhost-user.h b/contrib/libvhost-user/libvhost-user.h
+index 46b600799b..1844b6f8d4 100644
+--- a/contrib/libvhost-user/libvhost-user.h
++++ b/contrib/libvhost-user/libvhost-user.h
+@@ -19,6 +19,7 @@
+ #include <stddef.h>
+ #include <sys/poll.h>
+ #include <linux/vhost.h>
++#include <pthread.h>
+ #include "standard-headers/linux/virtio_ring.h"
+ 
+ /* Based on qemu/hw/virtio/vhost-user.c */
+@@ -355,6 +356,8 @@ struct VuDev {
+     VuVirtq *vq;
+     VuDevInflightInfo inflight_info;
+     int log_call_fd;
++    /* Must be held while using slave_fd */
++    pthread_mutex_t slave_mutex;
+     int slave_fd;
+     uint64_t log_size;
+     uint8_t *log_table;
+-- 
+2.27.0
+