contrib: add ivshmem client and server

When using ivshmem devices, notifications between guests can be sent as
interrupts using a ivshmem-server (typical use described in documentation).
The client is provided as a debug tool.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Signed-off-by: David Marchand <david.marchand@6wind.com>
[fix a valgrind warning, option and server_close() segvs, extra server
headers includes, getopt() return type, out-of-tree build, use qemu
event_notifier instead of eventfd, fix x86/osx warnings - Marc-André]
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

12 files changed, 1759 insertions, 3 deletions

diff --git a/Makefile b/Makefile
index cbf252d547..fc1f8bb934 100644
--- a/Makefile
+++ b/Makefile
@@ -151,6 +151,8 @@ dummy := $(call unnest-vars,, \
                 stub-obj-y \
                 util-obj-y \
                 qga-obj-y \
+                ivshmem-client-obj-y \
+                ivshmem-server-obj-y \
                 qga-vss-dll-obj-y \
                 block-obj-y \
                 block-obj-m \
@@ -323,6 +325,11 @@ ifneq ($(EXESUF),)
 qemu-ga: qemu-ga$(EXESUF) $(QGA_VSS_PROVIDER) $(QEMU_GA_MSI)
 endif
 
+ivshmem-client$(EXESUF): $(ivshmem-client-obj-y)
+	$(call LINK, $^)
+ivshmem-server$(EXESUF): $(ivshmem-server-obj-y) libqemuutil.a libqemustub.a
+	$(call LINK, $^)
+
 clean:
 # avoid old build problems by removing potentially incorrect old files
 	rm -f config.mak op-i386.h opc-i386.h gen-op-i386.h op-arm.h opc-arm.h gen-op-arm.h
diff --git a/Makefile.objs b/Makefile.objs
index ecfe03c195..fe02ee2cf4 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -104,3 +104,8 @@ target-obj-y += trace/
 # by libqemuutil.a.  These should be moved to a separate .json schema.
 qga-obj-y = qga/
 qga-vss-dll-obj-y = qga/
+
+######################################################################
+# contrib
+ivshmem-client-obj-y = contrib/ivshmem-client/
+ivshmem-server-obj-y = contrib/ivshmem-server/
diff --git a/configure b/configure
index 2a129bb6de..7a1d08dc4a 100755
--- a/configure
+++ b/configure
@@ -4508,6 +4508,7 @@ if test "$want_tools" = "yes" ; then
   tools="qemu-img\$(EXESUF) qemu-io\$(EXESUF) $tools"
   if [ "$linux" = "yes" -o "$bsd" = "yes" -o "$solaris" = "yes" ] ; then
     tools="qemu-nbd\$(EXESUF) $tools"
+    tools="ivshmem-client\$(EXESUF) ivshmem-server\$(EXESUF) $tools"
   fi
 fi
 if test "$softmmu" = yes ; then
diff --git a/contrib/ivshmem-client/Makefile.objs b/contrib/ivshmem-client/Makefile.objs
new file mode 100644
index 0000000000..bfab2d20dd
--- /dev/null
+++ b/contrib/ivshmem-client/Makefile.objs
@@ -0,0 +1 @@
+ivshmem-client-obj-y = ivshmem-client.o main.o
diff --git a/contrib/ivshmem-client/ivshmem-client.c b/contrib/ivshmem-client/ivshmem-client.c
new file mode 100644
index 0000000000..fcc0930eb6
--- /dev/null
+++ b/contrib/ivshmem-client/ivshmem-client.c
@@ -0,0 +1,433 @@
+/*
+ * Copyright 6WIND S.A., 2014
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include "qemu-common.h"
+#include "qemu/queue.h"
+
+#include "ivshmem-client.h"
+
+/* log a message on stdout if verbose=1 */
+#define IVSHMEM_CLIENT_DEBUG(client, fmt, ...) do { \
+        if ((client)->verbose) {         \
+            printf(fmt, ## __VA_ARGS__); \
+        }                                \
+    } while (0)
+
+/* read message from the unix socket */
+static int
+ivshmem_client_read_one_msg(IvshmemClient *client, long *index, int *fd)
+{
+    int ret;
+    struct msghdr msg;
+    struct iovec iov[1];
+    union {
+        struct cmsghdr cmsg;
+        char control[CMSG_SPACE(sizeof(int))];
+    } msg_control;
+    struct cmsghdr *cmsg;
+
+    iov[0].iov_base = index;
+    iov[0].iov_len = sizeof(*index);
+
+    memset(&msg, 0, sizeof(msg));
+    msg.msg_iov = iov;
+    msg.msg_iovlen = 1;
+    msg.msg_control = &msg_control;
+    msg.msg_controllen = sizeof(msg_control);
+
+    ret = recvmsg(client->sock_fd, &msg, 0);
+    if (ret < 0) {
+        IVSHMEM_CLIENT_DEBUG(client, "cannot read message: %s\n",
+                             strerror(errno));
+        return -1;
+    }
+    if (ret == 0) {
+        IVSHMEM_CLIENT_DEBUG(client, "lost connection to server\n");
+        return -1;
+    }
+
+    *fd = -1;
+
+    for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+
+        if (cmsg->cmsg_len != CMSG_LEN(sizeof(int)) ||
+            cmsg->cmsg_level != SOL_SOCKET ||
+            cmsg->cmsg_type != SCM_RIGHTS) {
+            continue;
+        }
+
+        memcpy(fd, CMSG_DATA(cmsg), sizeof(*fd));
+    }
+
+    return 0;
+}
+
+/* free a peer when the server advertises a disconnection or when the
+ * client is freed */
+static void
+ivshmem_client_free_peer(IvshmemClient *client, IvshmemClientPeer *peer)
+{
+    unsigned vector;
+
+    QTAILQ_REMOVE(&client->peer_list, peer, next);
+    for (vector = 0; vector < peer->vectors_count; vector++) {
+        close(peer->vectors[vector]);
+    }
+
+    g_free(peer);
+}
+
+/* handle message coming from server (new peer, new vectors) */
+static int
+ivshmem_client_handle_server_msg(IvshmemClient *client)
+{
+    IvshmemClientPeer *peer;
+    long peer_id;
+    int ret, fd;
+
+    ret = ivshmem_client_read_one_msg(client, &peer_id, &fd);
+    if (ret < 0) {
+        return -1;
+    }
+
+    /* can return a peer or the local client */
+    peer = ivshmem_client_search_peer(client, peer_id);
+
+    /* delete peer */
+    if (fd == -1) {
+
+        if (peer == NULL || peer == &client->local) {
+            IVSHMEM_CLIENT_DEBUG(client, "receive delete for invalid "
+                                 "peer %ld\n", peer_id);
+            return -1;
+        }
+
+        IVSHMEM_CLIENT_DEBUG(client, "delete peer id = %ld\n", peer_id);
+        ivshmem_client_free_peer(client, peer);
+        return 0;
+    }
+
+    /* new peer */
+    if (peer == NULL) {
+        peer = g_malloc0(sizeof(*peer));
+        peer->id = peer_id;
+        peer->vectors_count = 0;
+        QTAILQ_INSERT_TAIL(&client->peer_list, peer, next);
+        IVSHMEM_CLIENT_DEBUG(client, "new peer id = %ld\n", peer_id);
+    }
+
+    /* new vector */
+    IVSHMEM_CLIENT_DEBUG(client, "  new vector %d (fd=%d) for peer id %ld\n",
+                         peer->vectors_count, fd, peer->id);
+    peer->vectors[peer->vectors_count] = fd;
+    peer->vectors_count++;
+
+    return 0;
+}
+
+/* init a new ivshmem client */
+int
+ivshmem_client_init(IvshmemClient *client, const char *unix_sock_path,
+                    IvshmemClientNotifCb notif_cb, void *notif_arg,
+                    bool verbose)
+{
+    int ret;
+    unsigned i;
+
+    memset(client, 0, sizeof(*client));
+
+    ret = snprintf(client->unix_sock_path, sizeof(client->unix_sock_path),
+                   "%s", unix_sock_path);
+
+    if (ret < 0 || ret >= sizeof(client->unix_sock_path)) {
+        IVSHMEM_CLIENT_DEBUG(client, "could not copy unix socket path\n");
+        return -1;
+    }
+
+    for (i = 0; i < IVSHMEM_CLIENT_MAX_VECTORS; i++) {
+        client->local.vectors[i] = -1;
+    }
+
+    QTAILQ_INIT(&client->peer_list);
+    client->local.id = -1;
+
+    client->notif_cb = notif_cb;
+    client->notif_arg = notif_arg;
+    client->verbose = verbose;
+    client->shm_fd = -1;
+    client->sock_fd = -1;
+
+    return 0;
+}
+
+/* create and connect to the unix socket */
+int
+ivshmem_client_connect(IvshmemClient *client)
+{
+    struct sockaddr_un sun;
+    int fd, ret;
+    long tmp;
+
+    IVSHMEM_CLIENT_DEBUG(client, "connect to client %s\n",
+                         client->unix_sock_path);
+
+    client->sock_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (client->sock_fd < 0) {
+        IVSHMEM_CLIENT_DEBUG(client, "cannot create socket: %s\n",
+                             strerror(errno));
+        return -1;
+    }
+
+    sun.sun_family = AF_UNIX;
+    ret = snprintf(sun.sun_path, sizeof(sun.sun_path), "%s",
+                   client->unix_sock_path);
+    if (ret < 0 || ret >= sizeof(sun.sun_path)) {
+        IVSHMEM_CLIENT_DEBUG(client, "could not copy unix socket path\n");
+        goto err_close;
+    }
+
+    if (connect(client->sock_fd, (struct sockaddr *)&sun, sizeof(sun)) < 0) {
+        IVSHMEM_CLIENT_DEBUG(client, "cannot connect to %s: %s\n", sun.sun_path,
+                             strerror(errno));
+        goto err_close;
+    }
+
+    /* first, we expect our index + a fd == -1 */
+    if (ivshmem_client_read_one_msg(client, &client->local.id, &fd) < 0 ||
+        client->local.id < 0 || fd != -1) {
+        IVSHMEM_CLIENT_DEBUG(client, "cannot read from server\n");
+        goto err_close;
+    }
+    IVSHMEM_CLIENT_DEBUG(client, "our_id=%ld\n", client->local.id);
+
+    /* now, we expect shared mem fd + a -1 index, note that shm fd
+     * is not used */
+    if (ivshmem_client_read_one_msg(client, &tmp, &fd) < 0 ||
+        tmp != -1 || fd < 0) {
+        if (fd >= 0) {
+            close(fd);
+        }
+        IVSHMEM_CLIENT_DEBUG(client, "cannot read from server (2)\n");
+        goto err_close;
+    }
+    client->shm_fd = fd;
+    IVSHMEM_CLIENT_DEBUG(client, "shm_fd=%d\n", fd);
+
+    return 0;
+
+err_close:
+    close(client->sock_fd);
+    client->sock_fd = -1;
+    return -1;
+}
+
+/* close connection to the server, and free all peer structures */
+void
+ivshmem_client_close(IvshmemClient *client)
+{
+    IvshmemClientPeer *peer;
+    unsigned i;
+
+    IVSHMEM_CLIENT_DEBUG(client, "close client\n");
+
+    while ((peer = QTAILQ_FIRST(&client->peer_list)) != NULL) {
+        ivshmem_client_free_peer(client, peer);
+    }
+
+    close(client->shm_fd);
+    client->shm_fd = -1;
+    close(client->sock_fd);
+    client->sock_fd = -1;
+    client->local.id = -1;
+    for (i = 0; i < IVSHMEM_CLIENT_MAX_VECTORS; i++) {
+        close(client->local.vectors[i]);
+        client->local.vectors[i] = -1;
+    }
+    client->local.vectors_count = 0;
+}
+
+/* get the fd_set according to the unix socket and peer list */
+void
+ivshmem_client_get_fds(const IvshmemClient *client, fd_set *fds, int *maxfd)
+{
+    int fd;
+    unsigned vector;
+
+    FD_SET(client->sock_fd, fds);
+    if (client->sock_fd >= *maxfd) {
+        *maxfd = client->sock_fd + 1;
+    }
+
+    for (vector = 0; vector < client->local.vectors_count; vector++) {
+        fd = client->local.vectors[vector];
+        FD_SET(fd, fds);
+        if (fd >= *maxfd) {
+            *maxfd = fd + 1;
+        }
+    }
+}
+
+/* handle events from eventfd: just print a message on notification */
+static int
+ivshmem_client_handle_event(IvshmemClient *client, const fd_set *cur, int maxfd)
+{
+    IvshmemClientPeer *peer;
+    uint64_t kick;
+    unsigned i;
+    int ret;
+
+    peer = &client->local;
+
+    for (i = 0; i < peer->vectors_count; i++) {
+        if (peer->vectors[i] >= maxfd || !FD_ISSET(peer->vectors[i], cur)) {
+            continue;
+        }
+
+        ret = read(peer->vectors[i], &kick, sizeof(kick));
+        if (ret < 0) {
+            return ret;
+        }
+        if (ret != sizeof(kick)) {
+            IVSHMEM_CLIENT_DEBUG(client, "invalid read size = %d\n", ret);
+            errno = EINVAL;
+            return -1;
+        }
+        IVSHMEM_CLIENT_DEBUG(client, "received event on fd %d vector %d: %"
+                             PRIu64 "\n", peer->vectors[i], i, kick);
+        if (client->notif_cb != NULL) {
+            client->notif_cb(client, peer, i, client->notif_arg);
+        }
+    }
+
+    return 0;
+}
+
+/* read and handle new messages on the given fd_set */
+int
+ivshmem_client_handle_fds(IvshmemClient *client, fd_set *fds, int maxfd)
+{
+    if (client->sock_fd < maxfd && FD_ISSET(client->sock_fd, fds) &&
+        ivshmem_client_handle_server_msg(client) < 0 && errno != EINTR) {
+        IVSHMEM_CLIENT_DEBUG(client, "ivshmem_client_handle_server_msg() "
+                             "failed\n");
+        return -1;
+    } else if (ivshmem_client_handle_event(client, fds, maxfd) < 0 &&
+               errno != EINTR) {
+        IVSHMEM_CLIENT_DEBUG(client, "ivshmem_client_handle_event() failed\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+/* send a notification on a vector of a peer */
+int
+ivshmem_client_notify(const IvshmemClient *client,
+                      const IvshmemClientPeer *peer, unsigned vector)
+{
+    uint64_t kick;
+    int fd;
+
+    if (vector >= peer->vectors_count) {
+        IVSHMEM_CLIENT_DEBUG(client, "invalid vector %u on peer %ld\n",
+                             vector, peer->id);
+        return -1;
+    }
+    fd = peer->vectors[vector];
+    IVSHMEM_CLIENT_DEBUG(client, "notify peer %ld on vector %d, fd %d\n",
+                         peer->id, vector, fd);
+
+    kick = 1;
+    if (write(fd, &kick, sizeof(kick)) != sizeof(kick)) {
+        fprintf(stderr, "could not write to %d: %s\n", peer->vectors[vector],
+                strerror(errno));
+        return -1;
+    }
+    return 0;
+}
+
+/* send a notification to all vectors of a peer */
+int
+ivshmem_client_notify_all_vects(const IvshmemClient *client,
+                                const IvshmemClientPeer *peer)
+{
+    unsigned vector;
+    int ret = 0;
+
+    for (vector = 0; vector < peer->vectors_count; vector++) {
+        if (ivshmem_client_notify(client, peer, vector) < 0) {
+            ret = -1;
+        }
+    }
+
+    return ret;
+}
+
+/* send a notification to all peers */
+int
+ivshmem_client_notify_broadcast(const IvshmemClient *client)
+{
+    IvshmemClientPeer *peer;
+    int ret = 0;
+
+    QTAILQ_FOREACH(peer, &client->peer_list, next) {
+        if (ivshmem_client_notify_all_vects(client, peer) < 0) {
+            ret = -1;
+        }
+    }
+
+    return ret;
+}
+
+/* lookup peer from its id */
+IvshmemClientPeer *
+ivshmem_client_search_peer(IvshmemClient *client, long peer_id)
+{
+    IvshmemClientPeer *peer;
+
+    if (peer_id == client->local.id) {
+        return &client->local;
+    }
+
+    QTAILQ_FOREACH(peer, &client->peer_list, next) {
+        if (peer->id == peer_id) {
+            return peer;
+        }
+    }
+    return NULL;
+}
+
+/* dump our info, the list of peers their vectors on stdout */
+void
+ivshmem_client_dump(const IvshmemClient *client)
+{
+    const IvshmemClientPeer *peer;
+    unsigned vector;
+
+    /* dump local infos */
+    peer = &client->local;
+    printf("our_id = %ld\n", peer->id);
+    for (vector = 0; vector < peer->vectors_count; vector++) {
+        printf("  vector %d is enabled (fd=%d)\n", vector,
+               peer->vectors[vector]);
+    }
+
+    /* dump peers */
+    QTAILQ_FOREACH(peer, &client->peer_list, next) {
+        printf("peer_id = %ld\n", peer->id);
+
+        for (vector = 0; vector < peer->vectors_count; vector++) {
+            printf("  vector %d is enabled (fd=%d)\n", vector,
+                   peer->vectors[vector]);
+        }
+    }
+}
diff --git a/contrib/ivshmem-client/ivshmem-client.h b/contrib/ivshmem-client/ivshmem-client.h
new file mode 100644
index 0000000000..284c4a37fb
--- /dev/null
+++ b/contrib/ivshmem-client/ivshmem-client.h
@@ -0,0 +1,212 @@
+/*
+ * Copyright 6WIND S.A., 2014
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ */
+
+#ifndef _IVSHMEM_CLIENT_H_
+#define _IVSHMEM_CLIENT_H_
+
+/**
+ * This file provides helper to implement an ivshmem client. It is used
+ * on the host to ask QEMU to send an interrupt to an ivshmem PCI device in a
+ * guest. QEMU also implements an ivshmem client similar to this one, they both
+ * connect to an ivshmem server.
+ *
+ * A standalone ivshmem client based on this file is provided for debug/test
+ * purposes.
+ */
+
+#include <limits.h>
+#include <sys/select.h>
+
+#include "qemu/queue.h"
+
+/**
+ * Maximum number of notification vectors supported by the client
+ */
+#define IVSHMEM_CLIENT_MAX_VECTORS 64
+
+/**
+ * Structure storing a peer
+ *
+ * Each time a client connects to an ivshmem server, it is advertised to
+ * all connected clients through the unix socket. When our ivshmem
+ * client receives a notification, it creates a IvshmemClientPeer
+ * structure to store the infos of this peer.
+ *
+ * This structure is also used to store the information of our own
+ * client in (IvshmemClient)->local.
+ */
+typedef struct IvshmemClientPeer {
+    QTAILQ_ENTRY(IvshmemClientPeer) next;    /**< next in list*/
+    long id;                                 /**< the id of the peer */
+    int vectors[IVSHMEM_CLIENT_MAX_VECTORS]; /**< one fd per vector */
+    unsigned vectors_count;                  /**< number of vectors */
+} IvshmemClientPeer;
+QTAILQ_HEAD(IvshmemClientPeerList, IvshmemClientPeer);
+
+typedef struct IvshmemClientPeerList IvshmemClientPeerList;
+typedef struct IvshmemClient IvshmemClient;
+
+/**
+ * Typedef of callback function used when our IvshmemClient receives a
+ * notification from a peer.
+ */
+typedef void (*IvshmemClientNotifCb)(
+    const IvshmemClient *client,
+    const IvshmemClientPeer *peer,
+    unsigned vect, void *arg);
+
+/**
+ * Structure describing an ivshmem client
+ *
+ * This structure stores all information related to our client: the name
+ * of the server unix socket, the list of peers advertised by the
+ * server, our own client information, and a pointer the notification
+ * callback function used when we receive a notification from a peer.
+ */
+struct IvshmemClient {
+    char unix_sock_path[PATH_MAX];      /**< path to unix sock */
+    int sock_fd;                        /**< unix sock filedesc */
+    int shm_fd;                         /**< shm file descriptor */
+
+    IvshmemClientPeerList peer_list;    /**< list of peers */
+    IvshmemClientPeer local;            /**< our own infos */
+
+    IvshmemClientNotifCb notif_cb;      /**< notification callback */
+    void *notif_arg;                    /**< notification argument */
+
+    bool verbose;                       /**< true to enable debug */
+};
+
+/**
+ * Initialize an ivshmem client
+ *
+ * @client:         A pointer to an uninitialized IvshmemClient structure
+ * @unix_sock_path: The pointer to the unix socket file name
+ * @notif_cb:       If not NULL, the pointer to the function to be called when
+ *                  our IvshmemClient receives a notification from a peer
+ * @notif_arg:      Opaque pointer given as-is to the notification callback
+ *                  function
+ * @verbose:        True to enable debug
+ *
+ * Returns:         0 on success, or a negative value on error
+ */
+int ivshmem_client_init(IvshmemClient *client, const char *unix_sock_path,
+                        IvshmemClientNotifCb notif_cb, void *notif_arg,
+                        bool verbose);
+
+/**
+ * Connect to the server
+ *
+ * Connect to the server unix socket, and read the first initial
+ * messages sent by the server, giving the ID of the client and the file
+ * descriptor of the shared memory.
+ *
+ * @client: The ivshmem client
+ *
+ * Returns: 0 on success, or a negative value on error
+ */
+int ivshmem_client_connect(IvshmemClient *client);
+
+/**
+ * Close connection to the server and free all peer structures
+ *
+ * @client: The ivshmem client
+ */
+void ivshmem_client_close(IvshmemClient *client);
+
+/**
+ * Fill a fd_set with file descriptors to be monitored
+ *
+ * This function will fill a fd_set with all file descriptors
+ * that must be polled (unix server socket and peers eventfd). The
+ * function will not initialize the fd_set, it is up to the caller
+ * to do this.
+ *
+ * @client: The ivshmem client
+ * @fds:    The fd_set to be updated
+ * @maxfd:  Must be set to the max file descriptor + 1 in fd_set. This value is
+ *          updated if this function adds a greater fd in fd_set.
+ */
+void ivshmem_client_get_fds(const IvshmemClient *client, fd_set *fds,
+                            int *maxfd);
+
+/**
+ * Read and handle new messages
+ *
+ * Given a fd_set filled by select(), handle incoming messages from
+ * server or peers.
+ *
+ * @client: The ivshmem client
+ * @fds:    The fd_set containing the file descriptors to be checked. Note
+ *          that file descriptors that are not related to our client are
+ *          ignored.
+ * @maxfd:  The maximum fd in fd_set, plus one.
+ *
+ * Returns: 0 on success, or a negative value on error
+ */
+int ivshmem_client_handle_fds(IvshmemClient *client, fd_set *fds, int maxfd);
+
+/**
+ * Send a notification to a vector of a peer
+ *
+ * @client: The ivshmem client
+ * @peer:   The peer to be notified
+ * @vector: The number of the vector
+ *
+ * Returns: 0 on success, or a negative value on error
+ */
+int ivshmem_client_notify(const IvshmemClient *client,
+                          const IvshmemClientPeer *peer, unsigned vector);
+
+/**
+ * Send a notification to all vectors of a peer
+ *
+ * @client: The ivshmem client
+ * @peer:   The peer to be notified
+ *
+ * Returns: 0 on success, or a negative value on error (at least one
+ *          notification failed)
+ */
+int ivshmem_client_notify_all_vects(const IvshmemClient *client,
+                                    const IvshmemClientPeer *peer);
+
+/**
+ * Broadcat a notification to all vectors of all peers
+ *
+ * @client: The ivshmem client
+ *
+ * Returns: 0 on success, or a negative value on error (at least one
+ *          notification failed)
+ */
+int ivshmem_client_notify_broadcast(const IvshmemClient *client);
+
+/**
+ * Search a peer from its identifier
+ *
+ * Return the peer structure from its peer_id. If the given peer_id is
+ * the local id, the function returns the local peer structure.
+ *
+ * @client:  The ivshmem client
+ * @peer_id: The identifier of the peer structure
+ *
+ * Returns:  The peer structure, or NULL if not found
+ */
+IvshmemClientPeer *
+ivshmem_client_search_peer(IvshmemClient *client, long peer_id);
+
+/**
+ * Dump information of this ivshmem client on stdout
+ *
+ * Dump the id and the vectors of the given ivshmem client and the list
+ * of its peers and their vectors on stdout.
+ *
+ * @client: The ivshmem client
+ */
+void ivshmem_client_dump(const IvshmemClient *client);
+
+#endif /* _IVSHMEM_CLIENT_H_ */
diff --git a/contrib/ivshmem-client/main.c b/contrib/ivshmem-client/main.c
new file mode 100644
index 0000000000..44531f57be
--- /dev/null
+++ b/contrib/ivshmem-client/main.c
@@ -0,0 +1,239 @@
+/*
+ * Copyright 6WIND S.A., 2014
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ */
+
+#include "qemu-common.h"
+
+#include "ivshmem-client.h"
+
+#define IVSHMEM_CLIENT_DEFAULT_VERBOSE        0
+#define IVSHMEM_CLIENT_DEFAULT_UNIX_SOCK_PATH "/tmp/ivshmem_socket"
+
+typedef struct IvshmemClientArgs {
+    bool verbose;
+    const char *unix_sock_path;
+} IvshmemClientArgs;
+
+/* show ivshmem_client_usage and exit with given error code */
+static void
+ivshmem_client_usage(const char *name, int code)
+{
+    fprintf(stderr, "%s [opts]\n", name);
+    fprintf(stderr, "  -h: show this help\n");
+    fprintf(stderr, "  -v: verbose mode\n");
+    fprintf(stderr, "  -S <unix_sock_path>: path to the unix socket\n"
+                    "     to connect to.\n"
+                    "     default=%s\n", IVSHMEM_CLIENT_DEFAULT_UNIX_SOCK_PATH);
+    exit(code);
+}
+
+/* parse the program arguments, exit on error */
+static void
+ivshmem_client_parse_args(IvshmemClientArgs *args, int argc, char *argv[])
+{
+    int c;
+
+    while ((c = getopt(argc, argv,
+                       "h"  /* help */
+                       "v"  /* verbose */
+                       "S:" /* unix_sock_path */
+                      )) != -1) {
+
+        switch (c) {
+        case 'h': /* help */
+            ivshmem_client_usage(argv[0], 0);
+            break;
+
+        case 'v': /* verbose */
+            args->verbose = 1;
+            break;
+
+        case 'S': /* unix_sock_path */
+            args->unix_sock_path = strdup(optarg);
+            break;
+
+        default:
+            ivshmem_client_usage(argv[0], 1);
+            break;
+        }
+    }
+}
+
+/* show command line help */
+static void
+ivshmem_client_cmdline_help(void)
+{
+    printf("dump: dump peers (including us)\n"
+           "int <peer> <vector>: notify one vector on a peer\n"
+           "int <peer> all: notify all vectors of a peer\n"
+           "int all: notify all vectors of all peers (excepting us)\n");
+}
+
+/* read stdin and handle commands */
+static int
+ivshmem_client_handle_stdin_command(IvshmemClient *client)
+{
+    IvshmemClientPeer *peer;
+    char buf[128];
+    char *s, *token;
+    int ret;
+    int peer_id, vector;
+
+    memset(buf, 0, sizeof(buf));
+    ret = read(0, buf, sizeof(buf) - 1);
+    if (ret < 0) {
+        return -1;
+    }
+
+    s = buf;
+    while ((token = strsep(&s, "\n\r;")) != NULL) {
+        if (!strcmp(token, "")) {
+            continue;
+        }
+        if (!strcmp(token, "?")) {
+            ivshmem_client_cmdline_help();
+        }
+        if (!strcmp(token, "help")) {
+            ivshmem_client_cmdline_help();
+        } else if (!strcmp(token, "dump")) {
+            ivshmem_client_dump(client);
+        } else if (!strcmp(token, "int all")) {
+            ivshmem_client_notify_broadcast(client);
+        } else if (sscanf(token, "int %d %d", &peer_id, &vector) == 2) {
+            peer = ivshmem_client_search_peer(client, peer_id);
+            if (peer == NULL) {
+                printf("cannot find peer_id = %d\n", peer_id);
+                continue;
+            }
+            ivshmem_client_notify(client, peer, vector);
+        } else if (sscanf(token, "int %d all", &peer_id) == 1) {
+            peer = ivshmem_client_search_peer(client, peer_id);
+            if (peer == NULL) {
+                printf("cannot find peer_id = %d\n", peer_id);
+                continue;
+            }
+            ivshmem_client_notify_all_vects(client, peer);
+        } else {
+            printf("invalid command, type help\n");
+        }
+    }
+
+    printf("cmd> ");
+    fflush(stdout);
+    return 0;
+}
+
+/* listen on stdin (command line), on unix socket (notifications of new
+ * and dead peers), and on eventfd (IRQ request) */
+static int
+ivshmem_client_poll_events(IvshmemClient *client)
+{
+    fd_set fds;
+    int ret, maxfd;
+
+    while (1) {
+
+        FD_ZERO(&fds);
+        FD_SET(0, &fds); /* add stdin in fd_set */
+        maxfd = 1;
+
+        ivshmem_client_get_fds(client, &fds, &maxfd);
+
+        ret = select(maxfd, &fds, NULL, NULL, NULL);
+        if (ret < 0) {
+            if (errno == EINTR) {
+                continue;
+            }
+
+            fprintf(stderr, "select error: %s\n", strerror(errno));
+            break;
+        }
+        if (ret == 0) {
+            continue;
+        }
+
+        if (FD_ISSET(0, &fds) &&
+            ivshmem_client_handle_stdin_command(client) < 0 && errno != EINTR) {
+            fprintf(stderr, "ivshmem_client_handle_stdin_command() failed\n");
+            break;
+        }
+
+        if (ivshmem_client_handle_fds(client, &fds, maxfd) < 0) {
+            fprintf(stderr, "ivshmem_client_handle_fds() failed\n");
+            break;
+        }
+    }
+
+    return ret;
+}
+
+/* callback when we receive a notification (just display it) */
+static void
+ivshmem_client_notification_cb(const IvshmemClient *client,
+                               const IvshmemClientPeer *peer,
+                               unsigned vect, void *arg)
+{
+    (void)client;
+    (void)arg;
+    printf("receive notification from peer_id=%ld vector=%d\n", peer->id, vect);
+}
+
+int
+main(int argc, char *argv[])
+{
+    struct sigaction sa;
+    IvshmemClient client;
+    IvshmemClientArgs args = {
+        .verbose = IVSHMEM_CLIENT_DEFAULT_VERBOSE,
+        .unix_sock_path = IVSHMEM_CLIENT_DEFAULT_UNIX_SOCK_PATH,
+    };
+
+    /* parse arguments, will exit on error */
+    ivshmem_client_parse_args(&args, argc, argv);
+
+    /* Ignore SIGPIPE, see this link for more info:
+     * http://www.mail-archive.com/libevent-users@monkey.org/msg01606.html */
+    sa.sa_handler = SIG_IGN;
+    sa.sa_flags = 0;
+    if (sigemptyset(&sa.sa_mask) == -1 ||
+        sigaction(SIGPIPE, &sa, 0) == -1) {
+        perror("failed to ignore SIGPIPE; sigaction");
+        return 1;
+    }
+
+    ivshmem_client_cmdline_help();
+    printf("cmd> ");
+    fflush(stdout);
+
+    if (ivshmem_client_init(&client, args.unix_sock_path,
+                            ivshmem_client_notification_cb, NULL,
+                            args.verbose) < 0) {
+        fprintf(stderr, "cannot init client\n");
+        return 1;
+    }
+
+    while (1) {
+        if (ivshmem_client_connect(&client) < 0) {
+            fprintf(stderr, "cannot connect to server, retry in 1 second\n");
+            sleep(1);
+            continue;
+        }
+
+        fprintf(stdout, "listen on server socket %d\n", client.sock_fd);
+
+        if (ivshmem_client_poll_events(&client) == 0) {
+            continue;
+        }
+
+        /* disconnected from server, reset all peers */
+        fprintf(stdout, "disconnected from server\n");
+
+        ivshmem_client_close(&client);
+    }
+
+    return 0;
+}
diff --git a/contrib/ivshmem-server/Makefile.objs b/contrib/ivshmem-server/Makefile.objs
new file mode 100644
index 0000000000..c060dd3698
--- /dev/null
+++ b/contrib/ivshmem-server/Makefile.objs
@@ -0,0 +1 @@
+ivshmem-server-obj-y = ivshmem-server.o main.o
diff --git a/contrib/ivshmem-server/ivshmem-server.c b/contrib/ivshmem-server/ivshmem-server.c
new file mode 100644
index 0000000000..56b5df8ab7
--- /dev/null
+++ b/contrib/ivshmem-server/ivshmem-server.c
@@ -0,0 +1,422 @@
+/*
+ * Copyright 6WIND S.A., 2014
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ */
+#include "qemu-common.h"
+#include "qemu/sockets.h"
+
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include "ivshmem-server.h"
+
+/* log a message on stdout if verbose=1 */
+#define IVSHMEM_SERVER_DEBUG(server, fmt, ...) do { \
+        if ((server)->verbose) {         \
+            printf(fmt, ## __VA_ARGS__); \
+        }                                \
+    } while (0)
+
+/** maximum size of a huge page, used by ivshmem_server_ftruncate() */
+#define IVSHMEM_SERVER_MAX_HUGEPAGE_SIZE (1024 * 1024 * 1024)
+
+/** default listen backlog (number of sockets not accepted) */
+#define IVSHMEM_SERVER_LISTEN_BACKLOG 10
+
+/* send message to a client unix socket */
+static int
+ivshmem_server_send_one_msg(int sock_fd, long peer_id, int fd)
+{
+    int ret;
+    struct msghdr msg;
+    struct iovec iov[1];
+    union {
+        struct cmsghdr cmsg;
+        char control[CMSG_SPACE(sizeof(int))];
+    } msg_control;
+    struct cmsghdr *cmsg;
+
+    iov[0].iov_base = &peer_id;
+    iov[0].iov_len = sizeof(peer_id);
+
+    memset(&msg, 0, sizeof(msg));
+    msg.msg_iov = iov;
+    msg.msg_iovlen = 1;
+
+    /* if fd is specified, add it in a cmsg */
+    if (fd >= 0) {
+        memset(&msg_control, 0, sizeof(msg_control));
+        msg.msg_control = &msg_control;
+        msg.msg_controllen = sizeof(msg_control);
+        cmsg = CMSG_FIRSTHDR(&msg);
+        cmsg->cmsg_level = SOL_SOCKET;
+        cmsg->cmsg_type = SCM_RIGHTS;
+        cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+        memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
+    }
+
+    ret = sendmsg(sock_fd, &msg, 0);
+    if (ret <= 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+/* free a peer when the server advertises a disconnection or when the
+ * server is freed */
+static void
+ivshmem_server_free_peer(IvshmemServer *server, IvshmemServerPeer *peer)
+{
+    unsigned vector;
+    IvshmemServerPeer *other_peer;
+
+    IVSHMEM_SERVER_DEBUG(server, "free peer %ld\n", peer->id);
+    close(peer->sock_fd);
+    QTAILQ_REMOVE(&server->peer_list, peer, next);
+
+    /* advertise the deletion to other peers */
+    QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
+        ivshmem_server_send_one_msg(other_peer->sock_fd, peer->id, -1);
+    }
+
+    for (vector = 0; vector < peer->vectors_count; vector++) {
+        event_notifier_cleanup(&peer->vectors[vector]);
+    }
+
+    g_free(peer);
+}
+
+/* send the peer id and the shm_fd just after a new client connection */
+static int
+ivshmem_server_send_initial_info(IvshmemServer *server, IvshmemServerPeer *peer)
+{
+    int ret;
+
+    /* send the peer id to the client */
+    ret = ivshmem_server_send_one_msg(peer->sock_fd, peer->id, -1);
+    if (ret < 0) {
+        IVSHMEM_SERVER_DEBUG(server, "cannot send peer id: %s\n",
+                             strerror(errno));
+        return -1;
+    }
+
+    /* send the shm_fd */
+    ret = ivshmem_server_send_one_msg(peer->sock_fd, -1, server->shm_fd);
+    if (ret < 0) {
+        IVSHMEM_SERVER_DEBUG(server, "cannot send shm fd: %s\n",
+                             strerror(errno));
+        return -1;
+    }
+
+    return 0;
+}
+
+/* handle message on listening unix socket (new client connection) */
+static int
+ivshmem_server_handle_new_conn(IvshmemServer *server)
+{
+    IvshmemServerPeer *peer, *other_peer;
+    struct sockaddr_un unaddr;
+    socklen_t unaddr_len;
+    int newfd;
+    unsigned i;
+
+    /* accept the incoming connection */
+    unaddr_len = sizeof(unaddr);
+    newfd = qemu_accept(server->sock_fd,
+                        (struct sockaddr *)&unaddr, &unaddr_len);
+
+    if (newfd < 0) {
+        IVSHMEM_SERVER_DEBUG(server, "cannot accept() %s\n", strerror(errno));
+        return -1;
+    }
+
+    qemu_set_nonblock(newfd);
+    IVSHMEM_SERVER_DEBUG(server, "accept()=%d\n", newfd);
+
+    /* allocate new structure for this peer */
+    peer = g_malloc0(sizeof(*peer));
+    peer->sock_fd = newfd;
+
+    /* get an unused peer id */
+    while (ivshmem_server_search_peer(server, server->cur_id) != NULL) {
+        server->cur_id++;
+    }
+    peer->id = server->cur_id++;
+
+    /* create eventfd, one per vector */
+    peer->vectors_count = server->n_vectors;
+    for (i = 0; i < peer->vectors_count; i++) {
+        if (event_notifier_init(&peer->vectors[i], FALSE) < 0) {
+            IVSHMEM_SERVER_DEBUG(server, "cannot create eventfd\n");
+            goto fail;
+        }
+    }
+
+    /* send peer id and shm fd */
+    if (ivshmem_server_send_initial_info(server, peer) < 0) {
+        IVSHMEM_SERVER_DEBUG(server, "cannot send initial info\n");
+        goto fail;
+    }
+
+    /* advertise the new peer to others */
+    QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
+        for (i = 0; i < peer->vectors_count; i++) {
+            ivshmem_server_send_one_msg(other_peer->sock_fd, peer->id,
+                                        peer->vectors[i].wfd);
+        }
+    }
+
+    /* advertise the other peers to the new one */
+    QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
+        for (i = 0; i < peer->vectors_count; i++) {
+            ivshmem_server_send_one_msg(peer->sock_fd, other_peer->id,
+                                        other_peer->vectors[i].wfd);
+        }
+    }
+
+    /* advertise the new peer to itself */
+    for (i = 0; i < peer->vectors_count; i++) {
+        ivshmem_server_send_one_msg(peer->sock_fd, peer->id,
+                                    event_notifier_get_fd(&peer->vectors[i]));
+    }
+
+    QTAILQ_INSERT_TAIL(&server->peer_list, peer, next);
+    IVSHMEM_SERVER_DEBUG(server, "new peer id = %ld\n",
+                         peer->id);
+    return 0;
+
+fail:
+    while (i--) {
+        event_notifier_cleanup(&peer->vectors[i]);
+    }
+    close(newfd);
+    g_free(peer);
+    return -1;
+}
+
+/* Try to ftruncate a file to next power of 2 of shmsize.
+ * If it fails; all power of 2 above shmsize are tested until
+ * we reach the maximum huge page size. This is useful
+ * if the shm file is in a hugetlbfs that cannot be truncated to the
+ * shm_size value. */
+static int
+ivshmem_server_ftruncate(int fd, unsigned shmsize)
+{
+    int ret;
+    struct stat mapstat;
+
+    /* align shmsize to next power of 2 */
+    shmsize = pow2ceil(shmsize);
+
+    if (fstat(fd, &mapstat) != -1 && mapstat.st_size == shmsize) {
+        return 0;
+    }
+
+    while (shmsize <= IVSHMEM_SERVER_MAX_HUGEPAGE_SIZE) {
+        ret = ftruncate(fd, shmsize);
+        if (ret == 0) {
+            return ret;
+        }
+        shmsize *= 2;
+    }
+
+    return -1;
+}
+
+/* Init a new ivshmem server */
+int
+ivshmem_server_init(IvshmemServer *server, const char *unix_sock_path,
+                    const char *shm_path, size_t shm_size, unsigned n_vectors,
+                    bool verbose)
+{
+    int ret;
+
+    memset(server, 0, sizeof(*server));
+    server->verbose = verbose;
+
+    ret = snprintf(server->unix_sock_path, sizeof(server->unix_sock_path),
+                   "%s", unix_sock_path);
+    if (ret < 0 || ret >= sizeof(server->unix_sock_path)) {
+        IVSHMEM_SERVER_DEBUG(server, "could not copy unix socket path\n");
+        return -1;
+    }
+    ret = snprintf(server->shm_path, sizeof(server->shm_path),
+                   "%s", shm_path);
+    if (ret < 0 || ret >= sizeof(server->shm_path)) {
+        IVSHMEM_SERVER_DEBUG(server, "could not copy shm path\n");
+        return -1;
+    }
+
+    server->shm_size = shm_size;
+    server->n_vectors = n_vectors;
+
+    QTAILQ_INIT(&server->peer_list);
+
+    return 0;
+}
+
+/* open shm, create and bind to the unix socket */
+int
+ivshmem_server_start(IvshmemServer *server)
+{
+    struct sockaddr_un sun;
+    int shm_fd, sock_fd, ret;
+
+    /* open shm file */
+    shm_fd = shm_open(server->shm_path, O_CREAT|O_RDWR, S_IRWXU);
+    if (shm_fd < 0) {
+        fprintf(stderr, "cannot open shm file %s: %s\n", server->shm_path,
+                strerror(errno));
+        return -1;
+    }
+    if (ivshmem_server_ftruncate(shm_fd, server->shm_size) < 0) {
+        fprintf(stderr, "ftruncate(%s) failed: %s\n", server->shm_path,
+                strerror(errno));
+        goto err_close_shm;
+    }
+
+    IVSHMEM_SERVER_DEBUG(server, "create & bind socket %s\n",
+                         server->unix_sock_path);
+
+    /* create the unix listening socket */
+    sock_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (sock_fd < 0) {
+        IVSHMEM_SERVER_DEBUG(server, "cannot create socket: %s\n",
+                             strerror(errno));
+        goto err_close_shm;
+    }
+
+    sun.sun_family = AF_UNIX;
+    ret = snprintf(sun.sun_path, sizeof(sun.sun_path), "%s",
+                   server->unix_sock_path);
+    if (ret < 0 || ret >= sizeof(sun.sun_path)) {
+        IVSHMEM_SERVER_DEBUG(server, "could not copy unix socket path\n");
+        goto err_close_sock;
+    }
+    if (bind(sock_fd, (struct sockaddr *)&sun, sizeof(sun)) < 0) {
+        IVSHMEM_SERVER_DEBUG(server, "cannot connect to %s: %s\n", sun.sun_path,
+                             strerror(errno));
+        goto err_close_sock;
+    }
+
+    if (listen(sock_fd, IVSHMEM_SERVER_LISTEN_BACKLOG) < 0) {
+        IVSHMEM_SERVER_DEBUG(server, "listen() failed: %s\n", strerror(errno));
+        goto err_close_sock;
+    }
+
+    server->sock_fd = sock_fd;
+    server->shm_fd = shm_fd;
+
+    return 0;
+
+err_close_sock:
+    close(sock_fd);
+err_close_shm:
+    close(shm_fd);
+    return -1;
+}
+
+/* close connections to clients, the unix socket and the shm fd */
+void
+ivshmem_server_close(IvshmemServer *server)
+{
+    IvshmemServerPeer *peer, *npeer;
+
+    IVSHMEM_SERVER_DEBUG(server, "close server\n");
+
+    QTAILQ_FOREACH_SAFE(peer, &server->peer_list, next, npeer) {
+        ivshmem_server_free_peer(server, peer);
+    }
+
+    unlink(server->unix_sock_path);
+    close(server->sock_fd);
+    close(server->shm_fd);
+    server->sock_fd = -1;
+    server->shm_fd = -1;
+}
+
+/* get the fd_set according to the unix socket and the peer list */
+void
+ivshmem_server_get_fds(const IvshmemServer *server, fd_set *fds, int *maxfd)
+{
+    IvshmemServerPeer *peer;
+
+    if (server->sock_fd == -1) {
+        return;
+    }
+
+    FD_SET(server->sock_fd, fds);
+    if (server->sock_fd >= *maxfd) {
+        *maxfd = server->sock_fd + 1;
+    }
+
+    QTAILQ_FOREACH(peer, &server->peer_list, next) {
+        FD_SET(peer->sock_fd, fds);
+        if (peer->sock_fd >= *maxfd) {
+            *maxfd = peer->sock_fd + 1;
+        }
+    }
+}
+
+/* process incoming messages on the sockets in fd_set */
+int
+ivshmem_server_handle_fds(IvshmemServer *server, fd_set *fds, int maxfd)
+{
+    IvshmemServerPeer *peer, *peer_next;
+
+    if (server->sock_fd < maxfd && FD_ISSET(server->sock_fd, fds) &&
+        ivshmem_server_handle_new_conn(server) < 0 && errno != EINTR) {
+        IVSHMEM_SERVER_DEBUG(server, "ivshmem_server_handle_new_conn() "
+                             "failed\n");
+        return -1;
+    }
+
+    QTAILQ_FOREACH_SAFE(peer, &server->peer_list, next, peer_next) {
+        /* any message from a peer socket result in a close() */
+        IVSHMEM_SERVER_DEBUG(server, "peer->sock_fd=%d\n", peer->sock_fd);
+        if (peer->sock_fd < maxfd && FD_ISSET(peer->sock_fd, fds)) {
+            ivshmem_server_free_peer(server, peer);
+        }
+    }
+
+    return 0;
+}
+
+/* lookup peer from its id */
+IvshmemServerPeer *
+ivshmem_server_search_peer(IvshmemServer *server, long peer_id)
+{
+    IvshmemServerPeer *peer;
+
+    QTAILQ_FOREACH(peer, &server->peer_list, next) {
+        if (peer->id == peer_id) {
+            return peer;
+        }
+    }
+    return NULL;
+}
+
+/* dump our info, the list of peers their vectors on stdout */
+void
+ivshmem_server_dump(const IvshmemServer *server)
+{
+    const IvshmemServerPeer *peer;
+    unsigned vector;
+
+    /* dump peers */
+    QTAILQ_FOREACH(peer, &server->peer_list, next) {
+        printf("peer_id = %ld\n", peer->id);
+
+        for (vector = 0; vector < peer->vectors_count; vector++) {
+            printf("  vector %d is enabled (fd=%d)\n", vector,
+                   event_notifier_get_fd(&peer->vectors[vector]));
+        }
+    }
+}
diff --git a/contrib/ivshmem-server/ivshmem-server.h b/contrib/ivshmem-server/ivshmem-server.h
new file mode 100644
index 0000000000..bf7de7a7ca
--- /dev/null
+++ b/contrib/ivshmem-server/ivshmem-server.h
@@ -0,0 +1,167 @@
+/*
+ * Copyright 6WIND S.A., 2014
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ */
+
+#ifndef _IVSHMEM_SERVER_H_
+#define _IVSHMEM_SERVER_H_
+
+/**
+ * The ivshmem server is a daemon that creates a unix socket in listen
+ * mode. The ivshmem clients (qemu or ivshmem-client) connect to this
+ * unix socket. For each client, the server will create some eventfd
+ * (see EVENTFD(2)), one per vector. These fd are transmitted to all
+ * clients using the SCM_RIGHTS cmsg message. Therefore, each client is
+ * able to send a notification to another client without beeing
+ * "profixied" by the server.
+ *
+ * We use this mechanism to send interruptions between guests.
+ * qemu is able to transform an event on a eventfd into a PCI MSI-x
+ * interruption in the guest.
+ *
+ * The ivshmem server is also able to share the file descriptor
+ * associated to the ivshmem shared memory.
+ */
+
+#include <limits.h>
+#include <sys/select.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "qemu/event_notifier.h"
+#include "qemu/queue.h"
+
+/**
+ * Maximum number of notification vectors supported by the server
+ */
+#define IVSHMEM_SERVER_MAX_VECTORS 64
+
+/**
+ * Structure storing a peer
+ *
+ * Each time a client connects to an ivshmem server, a new
+ * IvshmemServerPeer structure is created. This peer and all its
+ * vectors are advertised to all connected clients through the connected
+ * unix sockets.
+ */
+typedef struct IvshmemServerPeer {
+    QTAILQ_ENTRY(IvshmemServerPeer) next;    /**< next in list*/
+    int sock_fd;                             /**< connected unix sock */
+    long id;                                 /**< the id of the peer */
+    EventNotifier vectors[IVSHMEM_SERVER_MAX_VECTORS]; /**< one per vector */
+    unsigned vectors_count;                  /**< number of vectors */
+} IvshmemServerPeer;
+QTAILQ_HEAD(IvshmemServerPeerList, IvshmemServerPeer);
+
+typedef struct IvshmemServerPeerList IvshmemServerPeerList;
+
+/**
+ * Structure describing an ivshmem server
+ *
+ * This structure stores all information related to our server: the name
+ * of the server unix socket and the list of connected peers.
+ */
+typedef struct IvshmemServer {
+    char unix_sock_path[PATH_MAX];   /**< path to unix socket */
+    int sock_fd;                     /**< unix sock file descriptor */
+    char shm_path[PATH_MAX];         /**< path to shm */
+    size_t shm_size;                 /**< size of shm */
+    int shm_fd;                      /**< shm file descriptor */
+    unsigned n_vectors;              /**< number of vectors */
+    long cur_id;                     /**< id to be given to next client */
+    bool verbose;                    /**< true in verbose mode */
+    IvshmemServerPeerList peer_list; /**< list of peers */
+} IvshmemServer;
+
+/**
+ * Initialize an ivshmem server
+ *
+ * @server:         A pointer to an uninitialized IvshmemServer structure
+ * @unix_sock_path: The pointer to the unix socket file name
+ * @shm_path:       Path to the shared memory. The path corresponds to a POSIX
+ *                  shm name. To use a real file, for instance in a hugetlbfs,
+ *                  it is possible to use /../../abspath/to/file.
+ * @shm_size:       Size of shared memory
+ * @n_vectors:      Number of interrupt vectors per client
+ * @verbose:        True to enable verbose mode
+ *
+ * Returns:         0 on success, or a negative value on error
+ */
+int
+ivshmem_server_init(IvshmemServer *server, const char *unix_sock_path,
+                    const char *shm_path, size_t shm_size, unsigned n_vectors,
+                    bool verbose);
+
+/**
+ * Open the shm, then create and bind to the unix socket
+ *
+ * @server: The pointer to the initialized IvshmemServer structure
+ *
+ * Returns: 0 on success, or a negative value on error
+ */
+int ivshmem_server_start(IvshmemServer *server);
+
+/**
+ * Close the server
+ *
+ * Close connections to all clients, close the unix socket and the
+ * shared memory file descriptor. The structure remains initialized, so
+ * it is possible to call ivshmem_server_start() again after a call to
+ * ivshmem_server_close().
+ *
+ * @server: The ivshmem server
+ */
+void ivshmem_server_close(IvshmemServer *server);
+
+/**
+ * Fill a fd_set with file descriptors to be monitored
+ *
+ * This function will fill a fd_set with all file descriptors that must
+ * be polled (unix server socket and peers unix socket). The function
+ * will not initialize the fd_set, it is up to the caller to do it.
+ *
+ * @server: The ivshmem server
+ * @fds:    The fd_set to be updated
+ * @maxfd:  Must be set to the max file descriptor + 1 in fd_set. This value is
+ *          updated if this function adds a greater fd in fd_set.
+ */
+void
+ivshmem_server_get_fds(const IvshmemServer *server, fd_set *fds, int *maxfd);
+
+/**
+ * Read and handle new messages
+ *
+ * Given a fd_set (for instance filled by a call to select()), handle
+ * incoming messages from peers.
+ *
+ * @server: The ivshmem server
+ * @fds:    The fd_set containing the file descriptors to be checked. Note that
+ *          file descriptors that are not related to our server are ignored.
+ * @maxfd:  The maximum fd in fd_set, plus one.
+ *
+ * Returns: 0 on success, or a negative value on error
+ */
+int ivshmem_server_handle_fds(IvshmemServer *server, fd_set *fds, int maxfd);
+
+/**
+ * Search a peer from its identifier
+ *
+ * @server:  The ivshmem server
+ * @peer_id: The identifier of the peer structure
+ *
+ * Returns:  The peer structure, or NULL if not found
+ */
+IvshmemServerPeer *
+ivshmem_server_search_peer(IvshmemServer *server, long peer_id);
+
+/**
+ * Dump information of this ivshmem server and its peers on stdout
+ *
+ * @server: The ivshmem server
+ */
+void ivshmem_server_dump(const IvshmemServer *server);
+
+#endif /* _IVSHMEM_SERVER_H_ */
diff --git a/contrib/ivshmem-server/main.c b/contrib/ivshmem-server/main.c
new file mode 100644
index 0000000000..064de02277
--- /dev/null
+++ b/contrib/ivshmem-server/main.c
@@ -0,0 +1,264 @@
+/*
+ * Copyright 6WIND S.A., 2014
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ */
+
+#include "qemu-common.h"
+
+#include "ivshmem-server.h"
+
+#define IVSHMEM_SERVER_DEFAULT_VERBOSE        0
+#define IVSHMEM_SERVER_DEFAULT_FOREGROUND     0
+#define IVSHMEM_SERVER_DEFAULT_PID_FILE       "/var/run/ivshmem-server.pid"
+#define IVSHMEM_SERVER_DEFAULT_UNIX_SOCK_PATH "/tmp/ivshmem_socket"
+#define IVSHMEM_SERVER_DEFAULT_SHM_PATH       "ivshmem"
+#define IVSHMEM_SERVER_DEFAULT_SHM_SIZE       (4*1024*1024)
+#define IVSHMEM_SERVER_DEFAULT_N_VECTORS      1
+
+/* used to quit on signal SIGTERM */
+static int ivshmem_server_quit;
+
+/* arguments given by the user */
+typedef struct IvshmemServerArgs {
+    bool verbose;
+    bool foreground;
+    const char *pid_file;
+    const char *unix_socket_path;
+    const char *shm_path;
+    uint64_t shm_size;
+    unsigned n_vectors;
+} IvshmemServerArgs;
+
+/* show ivshmem_server_usage and exit with given error code */
+static void
+ivshmem_server_usage(const char *name, int code)
+{
+    fprintf(stderr, "%s [opts]\n", name);
+    fprintf(stderr, "  -h: show this help\n");
+    fprintf(stderr, "  -v: verbose mode\n");
+    fprintf(stderr, "  -F: foreground mode (default is to daemonize)\n");
+    fprintf(stderr, "  -p <pid_file>: path to the PID file (used in daemon\n"
+                    "     mode only).\n"
+                    "     Default=%s\n", IVSHMEM_SERVER_DEFAULT_SHM_PATH);
+    fprintf(stderr, "  -S <unix_socket_path>: path to the unix socket\n"
+                    "     to listen to.\n"
+                    "     Default=%s\n", IVSHMEM_SERVER_DEFAULT_UNIX_SOCK_PATH);
+    fprintf(stderr, "  -m <shm_path>: path to the shared memory.\n"
+                    "     The path corresponds to a POSIX shm name. To use a\n"
+                    "     real file, for instance in a hugetlbfs, use\n"
+                    "     /../../abspath/to/file.\n"
+                    "     default=%s\n", IVSHMEM_SERVER_DEFAULT_SHM_PATH);
+    fprintf(stderr, "  -l <size>: size of shared memory in bytes. The suffix\n"
+                    "     K, M and G can be used (ex: 1K means 1024).\n"
+                    "     default=%u\n", IVSHMEM_SERVER_DEFAULT_SHM_SIZE);
+    fprintf(stderr, "  -n <n_vects>: number of vectors.\n"
+                    "     default=%u\n", IVSHMEM_SERVER_DEFAULT_N_VECTORS);
+
+    exit(code);
+}
+
+/* parse the program arguments, exit on error */
+static void
+ivshmem_server_parse_args(IvshmemServerArgs *args, int argc, char *argv[])
+{
+    int c;
+    unsigned long long v;
+    Error *errp = NULL;
+
+    while ((c = getopt(argc, argv,
+                       "h"  /* help */
+                       "v"  /* verbose */
+                       "F"  /* foreground */
+                       "p:" /* pid_file */
+                       "S:" /* unix_socket_path */
+                       "m:" /* shm_path */
+                       "l:" /* shm_size */
+                       "n:" /* n_vectors */
+                      )) != -1) {
+
+        switch (c) {
+        case 'h': /* help */
+            ivshmem_server_usage(argv[0], 0);
+            break;
+
+        case 'v': /* verbose */
+            args->verbose = 1;
+            break;
+
+        case 'F': /* foreground */
+            args->foreground = 1;
+            break;
+
+        case 'p': /* pid_file */
+            args->pid_file = strdup(optarg);
+            break;
+
+        case 'S': /* unix_socket_path */
+            args->unix_socket_path = strdup(optarg);
+            break;
+
+        case 'm': /* shm_path */
+            args->shm_path = strdup(optarg);
+            break;
+
+        case 'l': /* shm_size */
+            parse_option_size("shm_size", optarg, &args->shm_size, &errp);
+            if (errp) {
+                fprintf(stderr, "cannot parse shm size: %s\n",
+                        error_get_pretty(errp));
+                error_free(errp);
+                ivshmem_server_usage(argv[0], 1);
+            }
+            break;
+
+        case 'n': /* n_vectors */
+            if (parse_uint_full(optarg, &v, 0) < 0) {
+                fprintf(stderr, "cannot parse n_vectors\n");
+                ivshmem_server_usage(argv[0], 1);
+            }
+            args->n_vectors = v;
+            break;
+
+        default:
+            ivshmem_server_usage(argv[0], 1);
+            break;
+        }
+    }
+
+    if (args->n_vectors > IVSHMEM_SERVER_MAX_VECTORS) {
+        fprintf(stderr, "too many requested vectors (max is %d)\n",
+                IVSHMEM_SERVER_MAX_VECTORS);
+        ivshmem_server_usage(argv[0], 1);
+    }
+
+    if (args->verbose == 1 && args->foreground == 0) {
+        fprintf(stderr, "cannot use verbose in daemon mode\n");
+        ivshmem_server_usage(argv[0], 1);
+    }
+}
+
+/* wait for events on listening server unix socket and connected client
+ * sockets */
+static int
+ivshmem_server_poll_events(IvshmemServer *server)
+{
+    fd_set fds;
+    int ret = 0, maxfd;
+
+    while (!ivshmem_server_quit) {
+
+        FD_ZERO(&fds);
+        maxfd = 0;
+        ivshmem_server_get_fds(server, &fds, &maxfd);
+
+        ret = select(maxfd, &fds, NULL, NULL, NULL);
+
+        if (ret < 0) {
+            if (errno == EINTR) {
+                continue;
+            }
+
+            fprintf(stderr, "select error: %s\n", strerror(errno));
+            break;
+        }
+        if (ret == 0) {
+            continue;
+        }
+
+        if (ivshmem_server_handle_fds(server, &fds, maxfd) < 0) {
+            fprintf(stderr, "ivshmem_server_handle_fds() failed\n");
+            break;
+        }
+    }
+
+    return ret;
+}
+
+static void
+ivshmem_server_quit_cb(int signum)
+{
+    ivshmem_server_quit = 1;
+}
+
+int
+main(int argc, char *argv[])
+{
+    IvshmemServer server;
+    struct sigaction sa, sa_quit;
+    IvshmemServerArgs args = {
+        .verbose = IVSHMEM_SERVER_DEFAULT_VERBOSE,
+        .foreground = IVSHMEM_SERVER_DEFAULT_FOREGROUND,
+        .pid_file = IVSHMEM_SERVER_DEFAULT_PID_FILE,
+        .unix_socket_path = IVSHMEM_SERVER_DEFAULT_UNIX_SOCK_PATH,
+        .shm_path = IVSHMEM_SERVER_DEFAULT_SHM_PATH,
+        .shm_size = IVSHMEM_SERVER_DEFAULT_SHM_SIZE,
+        .n_vectors = IVSHMEM_SERVER_DEFAULT_N_VECTORS,
+    };
+    int ret = 1;
+
+    /* parse arguments, will exit on error */
+    ivshmem_server_parse_args(&args, argc, argv);
+
+    /* Ignore SIGPIPE, see this link for more info:
+     * http://www.mail-archive.com/libevent-users@monkey.org/msg01606.html */
+    sa.sa_handler = SIG_IGN;
+    sa.sa_flags = 0;
+    if (sigemptyset(&sa.sa_mask) == -1 ||
+        sigaction(SIGPIPE, &sa, 0) == -1) {
+        perror("failed to ignore SIGPIPE; sigaction");
+        goto err;
+    }
+
+    sa_quit.sa_handler = ivshmem_server_quit_cb;
+    sa_quit.sa_flags = 0;
+    if (sigemptyset(&sa_quit.sa_mask) == -1 ||
+        sigaction(SIGTERM, &sa_quit, 0) == -1) {
+        perror("failed to add SIGTERM handler; sigaction");
+        goto err;
+    }
+
+    /* init the ivshms structure */
+    if (ivshmem_server_init(&server, args.unix_socket_path, args.shm_path,
+                            args.shm_size, args.n_vectors, args.verbose) < 0) {
+        fprintf(stderr, "cannot init server\n");
+        goto err;
+    }
+
+    /* start the ivshmem server (open shm & unix socket) */
+    if (ivshmem_server_start(&server) < 0) {
+        fprintf(stderr, "cannot bind\n");
+        goto err;
+    }
+
+    /* daemonize if asked to */
+    if (!args.foreground) {
+        FILE *fp;
+
+        if (qemu_daemon(1, 1) < 0) {
+            fprintf(stderr, "cannot daemonize: %s\n", strerror(errno));
+            goto err_close;
+        }
+
+        /* write pid file */
+        fp = fopen(args.pid_file, "w");
+        if (fp == NULL) {
+            fprintf(stderr, "cannot write pid file: %s\n", strerror(errno));
+            goto err_close;
+        }
+
+        fprintf(fp, "%d\n", (int) getpid());
+        fclose(fp);
+    }
+
+    ivshmem_server_poll_events(&server);
+    fprintf(stdout, "server disconnected\n");
+    ret = 0;
+
+err_close:
+    ivshmem_server_close(&server);
+err:
+    return ret;
+}
diff --git a/qemu-doc.texi b/qemu-doc.texi
index 5b81aa052d..afa226303b 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -1266,9 +1266,13 @@ is qemu.git/contrib/ivshmem-server.  An example syntax when using the shared
 memory server is:
 
 @example
-qemu-system-i386 -device ivshmem,size=<size in format accepted by -m>[,chardev=<id>]
-                 [,msi=on][,ioeventfd=on][,vectors=n][,role=peer|master]
-qemu-system-i386 -chardev socket,path=<path>,id=<id>
+# First start the ivshmem server once and for all
+ivshmem-server -p <pidfile> -S <path> -m <shm name> -l <shm size> -n <vectors n>
+
+# Then start your qemu instances with matching arguments
+qemu-system-i386 -device ivshmem,size=<shm size>,vectors=<vectors n>,chardev=<id>
+                 [,msi=on][,ioeventfd=on][,role=peer|master]
+                 -chardev socket,path=<path>,id=<id>
 @end example
 
 When using the server, the guest will be assigned a VM ID (>=0) that allows guests