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[Qemu-devel] [PATCH v3 1/2] contrib: add ivshmem client and server


From: David Marchand
Subject: [Qemu-devel] [PATCH v3 1/2] contrib: add ivshmem client and server
Date: Fri, 8 Aug 2014 10:55:17 +0200

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 <address@hidden>
Signed-off-by: David Marchand <address@hidden>
---
 contrib/ivshmem-client/Makefile         |   29 +++
 contrib/ivshmem-client/ivshmem-client.c |  418 ++++++++++++++++++++++++++++++
 contrib/ivshmem-client/ivshmem-client.h |  238 ++++++++++++++++++
 contrib/ivshmem-client/main.c           |  246 ++++++++++++++++++
 contrib/ivshmem-server/Makefile         |   29 +++
 contrib/ivshmem-server/ivshmem-server.c |  420 +++++++++++++++++++++++++++++++
 contrib/ivshmem-server/ivshmem-server.h |  185 ++++++++++++++
 contrib/ivshmem-server/main.c           |  296 ++++++++++++++++++++++
 qemu-doc.texi                           |   10 +-
 9 files changed, 1868 insertions(+), 3 deletions(-)
 create mode 100644 contrib/ivshmem-client/Makefile
 create mode 100644 contrib/ivshmem-client/ivshmem-client.c
 create mode 100644 contrib/ivshmem-client/ivshmem-client.h
 create mode 100644 contrib/ivshmem-client/main.c
 create mode 100644 contrib/ivshmem-server/Makefile
 create mode 100644 contrib/ivshmem-server/ivshmem-server.c
 create mode 100644 contrib/ivshmem-server/ivshmem-server.h
 create mode 100644 contrib/ivshmem-server/main.c

diff --git a/contrib/ivshmem-client/Makefile b/contrib/ivshmem-client/Makefile
new file mode 100644
index 0000000..eee97c6
--- /dev/null
+++ b/contrib/ivshmem-client/Makefile
@@ -0,0 +1,29 @@
+# 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.
+
+S ?= $(CURDIR)
+O ?= $(CURDIR)
+
+CFLAGS += -Wall -Wextra -Werror -g
+LDFLAGS +=
+LDLIBS += -lrt
+
+VPATH = $(S)
+PROG = ivshmem-client
+OBJS := $(O)/ivshmem-client.o
+OBJS += $(O)/main.o
+
+$(O)/%.o: %.c
+       $(CC) $(CFLAGS) -o $@ -c $<
+
+$(O)/$(PROG): $(OBJS)
+       $(CC) $(LDFLAGS) -o $@ $^ $(LDLIBS)
+
+.PHONY: all
+all: $(O)/$(PROG)
+
+clean:
+       rm -f $(OBJS) $(O)/$(PROG)
diff --git a/contrib/ivshmem-client/ivshmem-client.c 
b/contrib/ivshmem-client/ivshmem-client.c
new file mode 100644
index 0000000..2166b64
--- /dev/null
+++ b/contrib/ivshmem-client/ivshmem-client.c
@@ -0,0 +1,418 @@
+/*
+ * 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 <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <signal.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include <sys/queue.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include "ivshmem-client.h"
+
+/* log a message on stdout if verbose=1 */
+#define debug_log(client, fmt, ...) do { \
+        if ((client)->verbose) {         \
+            printf(fmt, ## __VA_ARGS__); \
+        }                                \
+    } while (0)
+
+/* read message from the unix socket */
+static int
+read_one_msg(struct ivshmem_client *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) {
+        debug_log(client, "cannot read message: %s\n", strerror(errno));
+        return -1;
+    }
+    if (ret == 0) {
+        debug_log(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 advertise a disconnection or when the
+ * client is freed */
+static void
+free_peer(struct ivshmem_client *client, struct ivshmem_client_peer *peer)
+{
+    unsigned vector;
+
+    TAILQ_REMOVE(&client->peer_list, peer, next);
+    for (vector = 0; vector < peer->vectors_count; vector++) {
+        close(peer->vectors[vector]);
+    }
+
+    free(peer);
+}
+
+/* handle message coming from server (new peer, new vectors) */
+static int
+handle_server_msg(struct ivshmem_client *client)
+{
+    struct ivshmem_client_peer *peer;
+    long peer_id;
+    int ret, fd;
+
+    ret = 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) {
+            debug_log(client, "receive delete for invalid peer %ld", peer_id);
+            return -1;
+        }
+
+        debug_log(client, "delete peer id = %ld\n", peer_id);
+        free_peer(client, peer);
+        return 0;
+    }
+
+    /* new peer */
+    if (peer == NULL) {
+        peer = malloc(sizeof(*peer));
+        if (peer == NULL) {
+            debug_log(client, "cannot allocate new peer\n");
+            return -1;
+        }
+        memset(peer, 0, sizeof(*peer));
+        peer->id = peer_id;
+        peer->vectors_count = 0;
+        TAILQ_INSERT_TAIL(&client->peer_list, peer, next);
+        debug_log(client, "new peer id = %ld\n", peer_id);
+    }
+
+    /* new vector */
+    debug_log(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(struct ivshmem_client *client, const char *unix_sock_path,
+                    ivshmem_client_notif_cb_t notif_cb, void *notif_arg,
+                    int verbose)
+{
+    unsigned i;
+
+    memset(client, 0, sizeof(*client));
+
+    snprintf(client->unix_sock_path, sizeof(client->unix_sock_path),
+             "%s", unix_sock_path);
+
+    for (i = 0; i < IVSHMEM_CLIENT_MAX_VECTORS; i++) {
+        client->local.vectors[i] = -1;
+    }
+
+    TAILQ_INIT(&client->peer_list);
+    client->local.id = -1;
+
+    client->notif_cb = notif_cb;
+    client->notif_arg = notif_arg;
+    client->verbose = verbose;
+
+    return 0;
+}
+
+/* create and connect to the unix socket */
+int
+ivshmem_client_connect(struct ivshmem_client *client)
+{
+    struct sockaddr_un sun;
+    int fd;
+    long tmp;
+
+    debug_log(client, "connect to client %s\n", client->unix_sock_path);
+
+    client->sock_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (client->sock_fd < 0) {
+        debug_log(client, "cannot create socket: %s\n", strerror(errno));
+        return -1;
+    }
+
+    sun.sun_family = AF_UNIX;
+    snprintf(sun.sun_path, sizeof(sun.sun_path), "%s", client->unix_sock_path);
+    if (connect(client->sock_fd, (struct sockaddr *)&sun, sizeof(sun)) < 0) {
+        debug_log(client, "cannot connect to %s: %s\n", sun.sun_path,
+                  strerror(errno));
+        close(client->sock_fd);
+        client->sock_fd = -1;
+        return -1;
+    }
+
+    /* first, we expect our index + a fd == -1 */
+    if (read_one_msg(client, &client->local.id, &fd) < 0 ||
+        client->local.id < 0 || fd != -1) {
+        debug_log(client, "cannot read from server\n");
+        close(client->sock_fd);
+        client->sock_fd = -1;
+        return -1;
+    }
+    debug_log(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 (read_one_msg(client, &tmp, &fd) < 0 ||
+        tmp != -1 || fd < 0) {
+        debug_log(client, "cannot read from server (2)\n");
+        close(client->sock_fd);
+        client->sock_fd = -1;
+        return -1;
+    }
+    debug_log(client, "shm_fd=%d\n", fd);
+
+    return 0;
+}
+
+/* close connection to the server, and free all peer structures */
+void
+ivshmem_client_close(struct ivshmem_client *client)
+{
+    struct ivshmem_client_peer *peer;
+    unsigned i;
+
+    debug_log(client, "close client\n");
+
+    while ((peer = TAILQ_FIRST(&client->peer_list)) != NULL) {
+        free_peer(client, peer);
+    }
+
+    close(client->sock_fd);
+    client->sock_fd = -1;
+    client->local.id = -1;
+    for (i = 0; i < IVSHMEM_CLIENT_MAX_VECTORS; i++) {
+        client->local.vectors[i] = -1;
+    }
+}
+
+/* get the fd_set according to the unix socket and peer list */
+void
+ivshmem_client_get_fds(const struct ivshmem_client *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
+handle_event(struct ivshmem_client *client, const fd_set *cur, int maxfd)
+{
+    struct ivshmem_client_peer *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)) {
+            debug_log(client, "invalid read size = %d\n", ret);
+            errno = EINVAL;
+            return -1;
+        }
+        debug_log(client, "received event on fd %d vector %d: %ld\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(struct ivshmem_client *client, fd_set *fds, int 
maxfd)
+{
+    if (client->sock_fd < maxfd && FD_ISSET(client->sock_fd, fds) &&
+        handle_server_msg(client) < 0 && errno != EINTR) {
+        debug_log(client, "handle_server_msg() failed\n");
+        return -1;
+    } else if (handle_event(client, fds, maxfd) < 0 && errno != EINTR) {
+        debug_log(client, "handle_event() failed\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+/* send a notification on a vector of a peer */
+int
+ivshmem_client_notify(const struct ivshmem_client *client,
+                      const struct ivshmem_client_peer *peer, unsigned vector)
+{
+    uint64_t kick;
+    int fd;
+
+    if (vector > peer->vectors_count) {
+        debug_log(client, "invalid vector %u on peer %ld\n", vector, peer->id);
+        return -1;
+    }
+    fd = peer->vectors[vector];
+    debug_log(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 struct ivshmem_client *client,
+                                const struct ivshmem_client_peer *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 struct ivshmem_client *client)
+{
+    struct ivshmem_client_peer *peer;
+    int ret = 0;
+
+    TAILQ_FOREACH(peer, &client->peer_list, next) {
+        if (ivshmem_client_notify_all_vects(client, peer) < 0) {
+            ret = -1;
+        }
+    }
+
+    return ret;
+}
+
+/* lookup peer from its id */
+struct ivshmem_client_peer *
+ivshmem_client_search_peer(struct ivshmem_client *client, long peer_id)
+{
+    struct ivshmem_client_peer *peer;
+
+    if (peer_id == client->local.id) {
+        return &client->local;
+    }
+
+    TAILQ_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 struct ivshmem_client *client)
+{
+    const struct ivshmem_client_peer *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 */
+    TAILQ_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 0000000..d27222b
--- /dev/null
+++ b/contrib/ivshmem-client/ivshmem-client.h
@@ -0,0 +1,238 @@
+/*
+ * 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_
+#define _IVSHMEM_CLIENT_
+
+/**
+ * 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 <sys/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 ivshmem_client_peer
+ * structure to store the infos of this peer.
+ *
+ * This structure is also used to store the information of our own
+ * client in (struct ivshmem_client)->local.
+ */
+struct ivshmem_client_peer {
+    TAILQ_ENTRY(ivshmem_client_peer) 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 */
+};
+TAILQ_HEAD(ivshmem_client_peer_list, ivshmem_client_peer);
+
+struct ivshmem_client;
+
+/**
+ * Typedef of callback function used when our ivshmem_client receives a
+ * notification from a peer.
+ */
+typedef void (*ivshmem_client_notif_cb_t)(
+    const struct ivshmem_client *client,
+    const struct ivshmem_client_peer *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 ivshmem_client {
+    char unix_sock_path[PATH_MAX];        /**< path to unix sock */
+    int sock_fd;                          /**< unix sock filedesc */
+
+    struct ivshmem_client_peer_list peer_list;  /**< list of peers */
+    struct ivshmem_client_peer local;   /**< our own infos */
+
+    ivshmem_client_notif_cb_t notif_cb; /**< notification callback */
+    void *notif_arg;                      /**< notification argument */
+
+    int verbose;                          /**< true to enable debug */
+};
+
+/**
+ * Initialize an ivshmem client
+ *
+ * @param client
+ *   A pointer to an uninitialized ivshmem_client structure
+ * @param unix_sock_path
+ *   The pointer to the unix socket file name
+ * @param notif_cb
+ *   If not NULL, the pointer to the function to be called when we our
+ *   ivshmem_client receives a notification from a peer
+ * @param notif_arg
+ *   Opaque pointer given as-is to the notification callback function
+ * @param verbose
+ *   True to enable debug
+ *
+ * @return
+ *   0 on success, or a negative value on error
+ */
+int ivshmem_client_init(struct ivshmem_client *client,
+    const char *unix_sock_path, ivshmem_client_notif_cb_t notif_cb,
+    void *notif_arg, int 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.
+ *
+ * @param client
+ *   The ivshmem client
+ *
+ * @return
+ *   0 on success, or a negative value on error
+ */
+int ivshmem_client_connect(struct ivshmem_client *client);
+
+/**
+ * Close connection to the server and free all peer structures
+ *
+ * @param client
+ *   The ivshmem client
+ */
+void ivshmem_client_close(struct ivshmem_client *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.
+ *
+ * @param client
+ *   The ivshmem client
+ * @param fds
+ *   The fd_set to be updated
+ * @param maxfd
+ *   Must be set to the max file descriptor + 1 in fd_set. This value is
+ *   updated if this function adds a greated fd in fd_set.
+ */
+void ivshmem_client_get_fds(const struct ivshmem_client *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.
+ *
+ * @param client
+ *   The ivshmem client
+ * @param fds
+ *   The fd_set containing the file descriptors to be checked. Note
+ *   that file descriptors that are not related to our client are
+ *   ignored.
+ * @param maxfd
+ *   The maximum fd in fd_set, plus one.
+  *
+ * @return
+ *   0 on success, negative value on failure.
+ */
+int ivshmem_client_handle_fds(struct ivshmem_client *client, fd_set *fds,
+    int maxfd);
+
+/**
+ * Send a notification to a vector of a peer
+ *
+ * @param client
+ *   The ivshmem client
+ * @param peer
+ *   The peer to be notified
+ * @param vector
+ *   The number of the vector
+ *
+ * @return
+ *   0 on success, and a negative error on failure.
+ */
+int ivshmem_client_notify(const struct ivshmem_client *client,
+    const struct ivshmem_client_peer *peer, unsigned vector);
+
+/**
+ * Send a notification to all vectors of a peer
+ *
+ * @param client
+ *   The ivshmem client
+ * @param peer
+ *   The peer to be notified
+ *
+ * @return
+ *   0 on success, and a negative error on failure (at least one
+ *   notification failed).
+ */
+int ivshmem_client_notify_all_vects(const struct ivshmem_client *client,
+    const struct ivshmem_client_peer *peer);
+
+/**
+ * Broadcat a notification to all vectors of all peers
+ *
+ * @param client
+ *   The ivshmem client
+ *
+ * @return
+ *   0 on success, and a negative error on failure (at least one
+ *   notification failed).
+ */
+int ivshmem_client_notify_broadcast(const struct ivshmem_client *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.
+ *
+ * @param client
+ *   The ivshmem client
+ * @param peer_id
+ *   The identifier of the peer structure
+ *
+ * @return
+ *   The peer structure, or NULL if not found
+ */
+struct ivshmem_client_peer *
+ivshmem_client_search_peer(struct ivshmem_client *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.
+ *
+ * @param client
+ *   The ivshmem client
+ */
+void ivshmem_client_dump(const struct ivshmem_client *client);
+
+#endif /* _IVSHMEM_CLIENT_ */
diff --git a/contrib/ivshmem-client/main.c b/contrib/ivshmem-client/main.c
new file mode 100644
index 0000000..0d53f55
--- /dev/null
+++ b/contrib/ivshmem-client/main.c
@@ -0,0 +1,246 @@
+/*
+ * 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 <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <signal.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include <getopt.h>
+
+#include "ivshmem-client.h"
+
+#define DEFAULT_VERBOSE        0
+#define DEFAULT_UNIX_SOCK_PATH "/tmp/ivshmem_socket"
+
+struct ivshmem_client_args {
+    int verbose;
+    char *unix_sock_path;
+};
+
+/* show usage and exit with given error code */
+static void
+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 listen to.\n"
+                    "     default=%s\n", DEFAULT_UNIX_SOCK_PATH);
+    exit(code);
+}
+
+/* parse the program arguments, exit on error */
+static void
+parse_args(struct ivshmem_client_args *args, int argc, char *argv[])
+{
+    char c;
+
+    while ((c = getopt(argc, argv,
+                       "h"  /* help */
+                       "v"  /* verbose */
+                       "S:" /* unix_sock_path */
+                      )) != -1) {
+
+        switch (c) {
+        case 'h': /* help */
+            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:
+            usage(argv[0], 1);
+            break;
+        }
+    }
+}
+
+/* show command line help */
+static void
+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
+handle_stdin_command(struct ivshmem_client *client)
+{
+    struct ivshmem_client_peer *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, "?")) {
+            cmdline_help();
+        }
+        if (!strcmp(token, "help")) {
+            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) */
+int
+poll_events(struct ivshmem_client *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) &&
+            handle_stdin_command(client) < 0 && errno != EINTR) {
+            fprintf(stderr, "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) */
+void
+notification_cb(const struct ivshmem_client *client,
+                const struct ivshmem_client_peer *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;
+    struct ivshmem_client client;
+    struct ivshmem_client_args args = {
+        .verbose = DEFAULT_VERBOSE,
+        .unix_sock_path = DEFAULT_UNIX_SOCK_PATH,
+    };
+
+    /* parse arguments, will exit on error */
+    parse_args(&args, argc, argv);
+
+    /* Ignore SIGPIPE, see this link for more info:
+     * http://www.mail-archive.com/address@hidden/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;
+    }
+
+    cmdline_help();
+    printf("cmd> ");
+    fflush(stdout);
+
+    if (ivshmem_client_init(&client, args.unix_sock_path, 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 (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 b/contrib/ivshmem-server/Makefile
new file mode 100644
index 0000000..26b4a72
--- /dev/null
+++ b/contrib/ivshmem-server/Makefile
@@ -0,0 +1,29 @@
+# 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.
+
+S ?= $(CURDIR)
+O ?= $(CURDIR)
+
+CFLAGS += -Wall -Wextra -Werror -g
+LDFLAGS +=
+LDLIBS += -lrt
+
+VPATH = $(S)
+PROG = ivshmem-server
+OBJS := $(O)/ivshmem-server.o
+OBJS += $(O)/main.o
+
+$(O)/%.o: %.c
+       $(CC) $(CFLAGS) -o $@ -c $<
+
+$(O)/$(PROG): $(OBJS)
+       $(CC) $(LDFLAGS) -o $@ $^ $(LDLIBS)
+
+.PHONY: all
+all: $(O)/$(PROG)
+
+clean:
+       rm -f $(OBJS) $(O)/$(PROG)
diff --git a/contrib/ivshmem-server/ivshmem-server.c 
b/contrib/ivshmem-server/ivshmem-server.c
new file mode 100644
index 0000000..f6497bb
--- /dev/null
+++ b/contrib/ivshmem-server/ivshmem-server.c
@@ -0,0 +1,420 @@
+/*
+ * 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 <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <signal.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include <fcntl.h>
+
+#include <sys/queue.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <sys/eventfd.h>
+
+#include "ivshmem-server.h"
+
+/* log a message on stdout if verbose=1 */
+#define debug_log(server, fmt, ...) do { \
+        if ((server)->verbose) {         \
+            printf(fmt, ## __VA_ARGS__); \
+        }                                \
+    } while (0)
+
+/* browse the queue, allowing to remove/free the current element */
+#define    TAILQ_FOREACH_SAFE(var, var2, head, field)            \
+    for ((var) = TAILQ_FIRST((head)),                            \
+             (var2) = ((var) ? TAILQ_NEXT((var), field) : NULL); \
+         (var);                                                  \
+         (var) = (var2),                                         \
+             (var2) = ((var2) ? TAILQ_NEXT((var2), field) : NULL))
+
+/** maximum size of a huge page, used by ivshmem_ftruncate() */
+#define 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
+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) {
+        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 advertise a disconnection or when the
+ * server is freed */
+static void
+free_peer(struct ivshmem_server *server, struct ivshmem_server_peer *peer)
+{
+    unsigned vector;
+    struct ivshmem_server_peer *other_peer;
+
+    debug_log(server, "free peer %ld\n", peer->id);
+    close(peer->sock_fd);
+    TAILQ_REMOVE(&server->peer_list, peer, next);
+
+    /* advertise the deletion to other peers */
+    TAILQ_FOREACH(other_peer, &server->peer_list, next) {
+        send_one_msg(other_peer->sock_fd, peer->id, -1);
+    }
+
+    for (vector = 0; vector < peer->vectors_count; vector++) {
+        close(peer->vectors[vector]);
+    }
+
+    free(peer);
+}
+
+/* send the peer id and the shm_fd just after a new client connection */
+static int
+send_initial_info(struct ivshmem_server *server,
+                  struct ivshmem_server_peer *peer)
+{
+    int ret;
+
+    /* send the peer id to the client */
+    ret = send_one_msg(peer->sock_fd, peer->id, -1);
+    if (ret < 0) {
+        debug_log(server, "cannot send peer id: %s\n", strerror(errno));
+        return -1;
+    }
+
+    /* send the shm_fd */
+    ret = send_one_msg(peer->sock_fd, -1, server->shm_fd);
+    if (ret < 0) {
+        debug_log(server, "cannot send shm fd: %s\n", strerror(errno));
+        return -1;
+    }
+
+    return 0;
+}
+
+/* handle message on listening unix socket (new client connection) */
+static int
+handle_new_conn(struct ivshmem_server *server)
+{
+    struct ivshmem_server_peer *peer, *other_peer;
+    struct sockaddr_un unaddr;
+    socklen_t unaddr_len;
+    int newfd;
+    unsigned i;
+
+    /* accept the incoming connection */
+    unaddr_len = sizeof(unaddr);
+    newfd = accept(server->sock_fd, (struct sockaddr *)&unaddr, &unaddr_len);
+    if (newfd < 0) {
+        debug_log(server, "cannot accept() %s\n", strerror(errno));
+        return -1;
+    }
+
+    debug_log(server, "accept()=%d\n", newfd);
+
+    /* allocate new structure for this peer */
+    peer = malloc(sizeof(*peer));
+    if (peer == NULL) {
+        debug_log(server, "cannot allocate new peer\n");
+        close(newfd);
+        return -1;
+    }
+
+    /* initialize the peer struct, one eventfd per vector */
+    memset(peer, 0, 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++) {
+        peer->vectors[i] = eventfd(0, 0);
+        if (peer->vectors[i] < 0) {
+            debug_log(server, "cannot create eventfd\n");
+            goto fail;
+        }
+    }
+
+    /* send peer id and shm fd */
+    if (send_initial_info(server, peer) < 0) {
+        debug_log(server, "cannot send initial info\n");
+        goto fail;
+    }
+
+    /* advertise the new peer to others */
+    TAILQ_FOREACH(other_peer, &server->peer_list, next) {
+        for (i = 0; i < peer->vectors_count; i++) {
+            send_one_msg(other_peer->sock_fd, peer->id, peer->vectors[i]);
+        }
+    }
+
+    /* advertise the other peers to the new one */
+    TAILQ_FOREACH(other_peer, &server->peer_list, next) {
+        for (i = 0; i < peer->vectors_count; i++) {
+            send_one_msg(peer->sock_fd, other_peer->id, 
other_peer->vectors[i]);
+        }
+    }
+
+    /* advertise the new peer to itself */
+    for (i = 0; i < peer->vectors_count; i++) {
+        send_one_msg(peer->sock_fd, peer->id, peer->vectors[i]);
+    }
+
+    TAILQ_INSERT_TAIL(&server->peer_list, peer, next);
+    debug_log(server, "new peer id = %ld\n", peer->id);
+    return 0;
+
+fail:
+    while (i--) {
+        close(peer->vectors[i]);
+    }
+    peer->sock_fd = -1;
+    close(newfd);
+    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_ftruncate(int fd, unsigned shmsize)
+{
+    int ret;
+
+    /* align shmsize to next power of 2 */
+    shmsize--;
+    shmsize |= shmsize >> 1;
+    shmsize |= shmsize >> 2;
+    shmsize |= shmsize >> 4;
+    shmsize |= shmsize >> 8;
+    shmsize |= shmsize >> 16;
+    shmsize++;
+
+    while (shmsize <= 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(struct ivshmem_server *server, const char *unix_sock_path,
+                    const char *shm_path, size_t shm_size, unsigned n_vectors,
+                    int verbose)
+{
+    memset(server, 0, sizeof(*server));
+
+    snprintf(server->unix_sock_path, sizeof(server->unix_sock_path),
+             "%s", unix_sock_path);
+    snprintf(server->shm_path, sizeof(server->shm_path),
+             "%s", shm_path);
+
+    server->shm_size = shm_size;
+    server->n_vectors = n_vectors;
+    server->verbose = verbose;
+
+    TAILQ_INIT(&server->peer_list);
+
+    return 0;
+}
+
+/* open shm, create and bind to the unix socket */
+int
+ivshmem_server_start(struct ivshmem_server *server)
+{
+    struct sockaddr_un sun;
+    int shm_fd, sock_fd;
+
+    /* 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_ftruncate(shm_fd, server->shm_size) < 0) {
+        fprintf(stderr, "ftruncate(%s) failed: %s\n", server->shm_path,
+                strerror(errno));
+        return -1;
+    }
+
+    debug_log(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) {
+        debug_log(server, "cannot create socket: %s\n", strerror(errno));
+        close(shm_fd);
+        return -1;
+    }
+
+    sun.sun_family = AF_UNIX;
+    snprintf(sun.sun_path, sizeof(sun.sun_path), "%s", server->unix_sock_path);
+    unlink(sun.sun_path);
+    if (bind(sock_fd, (struct sockaddr *)&sun, sizeof(sun)) < 0) {
+        debug_log(server, "cannot connect to %s: %s\n", sun.sun_path,
+                  strerror(errno));
+        close(sock_fd);
+        close(shm_fd);
+        return -1;
+    }
+
+    if (listen(sock_fd, IVSHMEM_SERVER_LISTEN_BACKLOG) < 0) {
+        debug_log(server, "listen() failed: %s\n", strerror(errno));
+        close(sock_fd);
+        close(shm_fd);
+        return -1;
+    }
+
+    server->sock_fd = sock_fd;
+    server->shm_fd = shm_fd;
+
+    return 0;
+}
+
+/* close connections to clients, the unix socket and the shm fd */
+void
+ivshmem_server_close(struct ivshmem_server *server)
+{
+    struct ivshmem_server_peer *peer;
+
+    debug_log(server, "close server\n");
+
+    TAILQ_FOREACH(peer, &server->peer_list, next) {
+        free_peer(server, peer);
+    }
+
+    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 struct ivshmem_server *server, fd_set *fds,
+                       int *maxfd)
+{
+    struct ivshmem_server_peer *peer;
+
+    FD_SET(server->sock_fd, fds);
+    if (server->sock_fd >= *maxfd) {
+        *maxfd = server->sock_fd + 1;
+    }
+
+    TAILQ_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(struct ivshmem_server *server, fd_set *fds, int 
maxfd)
+{
+    struct ivshmem_server_peer *peer, *peer_next;
+
+    if (server->sock_fd < maxfd && FD_ISSET(server->sock_fd, fds) &&
+        handle_new_conn(server) < 0 && errno != EINTR) {
+        debug_log(server, "handle_new_conn() failed\n");
+        return -1;
+    }
+
+    TAILQ_FOREACH_SAFE(peer, peer_next, &server->peer_list, next) {
+        /* any message from a peer socket result in a close() */
+        debug_log(server, "peer->sock_fd=%d\n", peer->sock_fd);
+        if (peer->sock_fd < maxfd && FD_ISSET(peer->sock_fd, fds)) {
+            free_peer(server, peer);
+        }
+    }
+
+    return 0;
+}
+
+/* lookup peer from its id */
+struct ivshmem_server_peer *
+ivshmem_server_search_peer(struct ivshmem_server *server, long peer_id)
+{
+    struct ivshmem_server_peer *peer;
+
+    TAILQ_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 struct ivshmem_server *server)
+{
+    const struct ivshmem_server_peer *peer;
+    unsigned vector;
+
+    /* dump peers */
+    TAILQ_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,
+                   peer->vectors[vector]);
+        }
+    }
+}
diff --git a/contrib/ivshmem-server/ivshmem-server.h 
b/contrib/ivshmem-server/ivshmem-server.h
new file mode 100644
index 0000000..cd74bbf
--- /dev/null
+++ b/contrib/ivshmem-server/ivshmem-server.h
@@ -0,0 +1,185 @@
+/*
+ * 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_
+#define _IVSHMEM_SERVER_
+
+/**
+ * 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 <sys/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
+ * ivshmem_server_peer structure is created. This peer and all its
+ * vectors are advertised to all connected clients through the connected
+ * unix sockets.
+ */
+struct ivshmem_server_peer {
+    TAILQ_ENTRY(ivshmem_server_peer) next;    /**< next in list*/
+    int sock_fd;                                /**< connected unix sock */
+    long id;                                    /**< the id of the peer */
+    int vectors[IVSHMEM_SERVER_MAX_VECTORS];  /**< one fd per vector */
+    unsigned vectors_count;                     /**< number of vectors */
+};
+TAILQ_HEAD(ivshmem_server_peer_list, ivshmem_server_peer);
+
+/**
+ * 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.
+ */
+struct ivshmem_server {
+    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 */
+    int verbose;                    /**< true in verbose mode */
+    struct ivshmem_server_peer_list peer_list;  /**< list of peers */
+};
+
+/**
+ * Initialize an ivshmem server
+ *
+ * @param server
+ *   A pointer to an uninitialized ivshmem_server structure
+ * @param unix_sock_path
+ *   The pointer to the unix socket file name
+ * @param 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.
+ * @param shm_size
+ *   Size of shared memory
+ * @param n_vectors
+ *   Number of interrupt vectors per client
+ * @param verbose
+ *   True to enable verbose mode
+ *
+ * @return
+ *   0 on success, negative value on error
+ */
+int
+ivshmem_server_init(struct ivshmem_server *server,
+    const char *unix_sock_path, const char *shm_path, size_t shm_size,
+    unsigned n_vectors, int verbose);
+
+/**
+ * Open the shm, then create and bind to the unix socket
+ *
+ * @param server
+ *   The pointer to the initialized ivshmem server structure
+ *
+ * @return
+ *   0 on success, or a negative value on error
+ */
+int ivshmem_server_start(struct ivshmem_server *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().
+ *
+ * @param server
+ *   The ivshmem server
+ */
+void ivshmem_server_close(struct ivshmem_server *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.
+ *
+ * @param server
+ *   The ivshmem server
+ * @param fds
+ *   The fd_set to be updated
+ * @param maxfd
+ *   Must be set to the max file descriptor + 1 in fd_set. This value is
+ *   updated if this function adds a greated fd in fd_set.
+ */
+void
+ivshmem_server_get_fds(const struct ivshmem_server *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.
+ *
+ * @param server
+ *   The ivshmem server
+ * @param fds
+ *   The fd_set containing the file descriptors to be checked. Note
+ *   that file descriptors that are not related to our server are
+ *   ignored.
+ * @param maxfd
+ *   The maximum fd in fd_set, plus one.
+ *
+ * @return
+ *   0 on success, negative value on failure.
+ */
+int ivshmem_server_handle_fds(struct ivshmem_server *server, fd_set *fds,
+    int maxfd);
+
+/**
+ * Search a peer from its identifier
+ *
+ * @param server
+ *   The ivshmem server
+ * @param peer_id
+ *   The identifier of the peer structure
+ *
+ * @return
+ *   The peer structure, or NULL if not found
+ */
+struct ivshmem_server_peer *
+ivshmem_server_search_peer(struct ivshmem_server *server, long peer_id);
+
+/**
+ * Dump information of this ivshmem server and its peers on stdout
+ *
+ * @param server
+ *   The ivshmem server
+ */
+void ivshmem_server_dump(const struct ivshmem_server *server);
+
+#endif /* _IVSHMEM_SERVER_ */
diff --git a/contrib/ivshmem-server/main.c b/contrib/ivshmem-server/main.c
new file mode 100644
index 0000000..36b7028
--- /dev/null
+++ b/contrib/ivshmem-server/main.c
@@ -0,0 +1,296 @@
+/*
+ * 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 <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <signal.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include <sys/types.h>
+#include <limits.h>
+#include <getopt.h>
+
+#include "ivshmem-server.h"
+
+#define DEFAULT_VERBOSE        0
+#define DEFAULT_FOREGROUND     0
+#define DEFAULT_PID_FILE       "/var/run/ivshmem-server.pid"
+#define DEFAULT_UNIX_SOCK_PATH "/tmp/ivshmem_socket"
+#define DEFAULT_SHM_PATH       "ivshmem"
+#define DEFAULT_SHM_SIZE       (1024*1024)
+#define DEFAULT_N_VECTORS      16
+
+/* arguments given by the user */
+struct ivshmem_server_args {
+    int verbose;
+    int foreground;
+    char *pid_file;
+    char *unix_socket_path;
+    char *shm_path;
+    size_t shm_size;
+    unsigned n_vectors;
+};
+
+/* show usage and exit with given error code */
+static void
+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", DEFAULT_SHM_PATH);
+    fprintf(stderr, "  -S <unix_socket_path>: path to the unix socket\n"
+                    "     to listen to.\n"
+                    "     Default=%s\n", 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", 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", DEFAULT_SHM_SIZE);
+    fprintf(stderr, "  -n <n_vects>: number of vectors.\n"
+                    "     default=%u\n", DEFAULT_N_VECTORS);
+
+    exit(code);
+}
+
+/* parse the size of shm */
+static int
+parse_size(const char *val_str, size_t *val)
+{
+    char *endptr;
+    unsigned long long tmp;
+
+    errno = 0;
+    tmp = strtoull(val_str, &endptr, 0);
+    if ((errno == ERANGE && tmp == ULLONG_MAX) || (errno != 0 && tmp == 0)) {
+        return -1;
+    }
+    if (endptr == val_str) {
+        return -1;
+    }
+    if (endptr[0] == 'K' && endptr[1] == '\0') {
+        tmp *= 1024;
+    } else if (endptr[0] == 'M' && endptr[1] == '\0') {
+        tmp *= 1024 * 1024;
+    } else if (endptr[0] == 'G' && endptr[1] == '\0') {
+        tmp *= 1024 * 1024 * 1024;
+    } else if (endptr[0] != '\0') {
+        return -1;
+    }
+
+    *val = tmp;
+    return 0;
+}
+
+/* parse an unsigned int */
+static int
+parse_uint(const char *val_str, unsigned *val)
+{
+    char *endptr;
+    unsigned long tmp;
+
+    errno = 0;
+    tmp = strtoul(val_str, &endptr, 0);
+    if ((errno == ERANGE && tmp == ULONG_MAX) || (errno != 0 && tmp == 0)) {
+        return -1;
+    }
+    if (endptr == val_str || endptr[0] != '\0') {
+        return -1;
+    }
+    *val = tmp;
+    return 0;
+}
+
+/* parse the program arguments, exit on error */
+static void
+parse_args(struct ivshmem_server_args *args, int argc, char *argv[])
+{
+    char c;
+
+    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 */
+            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 */
+            if (parse_size(optarg, &args->shm_size) < 0) {
+                fprintf(stderr, "cannot parse shm size\n");
+                usage(argv[0], 1);
+            }
+            break;
+
+        case 'n': /* n_vectors */
+            if (parse_uint(optarg, &args->n_vectors) < 0) {
+                fprintf(stderr, "cannot parse n_vectors\n");
+                usage(argv[0], 1);
+            }
+            break;
+
+        default:
+            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);
+        usage(argv[0], 1);
+    }
+
+    if (args->verbose == 1 && args->foreground == 0) {
+        fprintf(stderr, "cannot use verbose in daemon mode\n");
+        usage(argv[0], 1);
+    }
+}
+
+/* wait for events on listening server unix socket and connected client
+ * sockets */
+int
+poll_events(struct ivshmem_server *server)
+{
+    fd_set fds;
+    int ret, maxfd;
+
+    while (1) {
+
+        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;
+}
+
+int
+main(int argc, char *argv[])
+{
+    struct ivshmem_server server;
+    struct sigaction sa;
+    struct ivshmem_server_args args = {
+        .verbose = DEFAULT_VERBOSE,
+        .foreground = DEFAULT_FOREGROUND,
+        .pid_file = DEFAULT_PID_FILE,
+        .unix_socket_path = DEFAULT_UNIX_SOCK_PATH,
+        .shm_path = DEFAULT_SHM_PATH,
+        .shm_size = DEFAULT_SHM_SIZE,
+        .n_vectors = DEFAULT_N_VECTORS,
+    };
+
+    /* parse arguments, will exit on error */
+    parse_args(&args, argc, argv);
+
+    /* Ignore SIGPIPE, see this link for more info:
+     * http://www.mail-archive.com/address@hidden/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;
+    }
+
+    /* 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");
+        return 1;
+    }
+
+    /* start the ivshmem server (open shm & unix socket) */
+    if (ivshmem_server_start(&server) < 0) {
+        fprintf(stderr, "cannot bind\n");
+        return 1;
+    }
+
+    /* daemonize if asked to */
+    if (!args.foreground) {
+        FILE *fp;
+
+        if (daemon(1, 1) < 0) {
+            fprintf(stderr, "cannot daemonize: %s\n", strerror(errno));
+            return 1;
+        }
+
+        /* write pid file */
+        fp = fopen(args.pid_file, "w");
+        if (fp == NULL) {
+            fprintf(stderr, "cannot write pid file: %s\n", strerror(errno));
+            return 1;
+        }
+
+        fprintf(fp, "%d\n", (int) getpid());
+        fclose(fp);
+    }
+
+    poll_events(&server);
+
+    fprintf(stdout, "server disconnected\n");
+    ivshmem_server_close(&server);
+
+    return 0;
+}
diff --git a/qemu-doc.texi b/qemu-doc.texi
index 2b232ae..380d573 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -1250,9 +1250,13 @@ 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
-- 
1.7.10.4




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