diff --git a/block/Makefile.objs b/block/Makefile.objs
index f43ecbc..4e8c91e 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -10,7 +10,7 @@
 block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
 
 ifeq ($(CONFIG_POSIX),y)
-block-obj-y += nbd.o sheepdog.o
+block-obj-y += nbd.o nbd-client.o sheepdog.o
 block-obj-$(CONFIG_LIBISCSI) += iscsi.o
 block-obj-$(CONFIG_CURL) += curl.o
 block-obj-$(CONFIG_RBD) += rbd.o
diff --git a/block/nbd-client.c b/block/nbd-client.c
new file mode 100644
index 0000000..0922b78
--- /dev/null
+++ b/block/nbd-client.c
@@ -0,0 +1,385 @@
+/*
+ * QEMU Block driver for  NBD
+ *
+ * Copyright (C) 2008 Bull S.A.S.
+ *     Author: Laurent Vivier <Laurent.Vivier@bull.net>
+ *
+ * Some parts:
+ *    Copyright (C) 2007 Anthony Liguori <anthony@codemonkey.ws>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "nbd-client.h"
+#include "qemu/sockets.h"
+
+#define HANDLE_TO_INDEX(bs, handle) ((handle) ^ ((uint64_t)(intptr_t)bs))
+#define INDEX_TO_HANDLE(bs, index)  ((index)  ^ ((uint64_t)(intptr_t)bs))
+
+static void nbd_recv_coroutines_enter_all(NbdClientSession *s)
+{
+    int i;
+
+    for (i = 0; i < MAX_NBD_REQUESTS; i++) {
+        if (s->recv_coroutine[i]) {
+            qemu_coroutine_enter(s->recv_coroutine[i], NULL);
+        }
+    }
+}
+
+static void nbd_reply_ready(void *opaque)
+{
+    NbdClientSession *s = opaque;
+    uint64_t i;
+    int ret;
+
+    if (s->reply.handle == 0) {
+        /* No reply already in flight.  Fetch a header.  It is possible
+         * that another thread has done the same thing in parallel, so
+         * the socket is not readable anymore.
+         */
+        ret = nbd_receive_reply(s->sock, &s->reply);
+        if (ret == -EAGAIN) {
+            return;
+        }
+        if (ret < 0) {
+            s->reply.handle = 0;
+            goto fail;
+        }
+    }
+
+    /* There's no need for a mutex on the receive side, because the
+     * handler acts as a synchronization point and ensures that only
+     * one coroutine is called until the reply finishes.  */
+    i = HANDLE_TO_INDEX(s, s->reply.handle);
+    if (i >= MAX_NBD_REQUESTS) {
+        goto fail;
+    }
+
+    if (s->recv_coroutine[i]) {
+        qemu_coroutine_enter(s->recv_coroutine[i], NULL);
+        return;
+    }
+
+fail:
+    nbd_recv_coroutines_enter_all(s);
+}
+
+static void nbd_restart_write(void *opaque)
+{
+    NbdClientSession *s = opaque;
+
+    qemu_coroutine_enter(s->send_coroutine, NULL);
+}
+
+static int nbd_co_send_request(NbdClientSession *s,
+    struct nbd_request *request,
+    QEMUIOVector *qiov, int offset)
+{
+    int rc, ret;
+
+    qemu_co_mutex_lock(&s->send_mutex);
+    s->send_coroutine = qemu_coroutine_self();
+    qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, nbd_restart_write, s);
+    if (qiov) {
+        if (!s->is_unix) {
+            socket_set_cork(s->sock, 1);
+        }
+        rc = nbd_send_request(s->sock, request);
+        if (rc >= 0) {
+            ret = qemu_co_sendv(s->sock, qiov->iov, qiov->niov,
+                                offset, request->len);
+            if (ret != request->len) {
+                rc = -EIO;
+            }
+        }
+        if (!s->is_unix) {
+            socket_set_cork(s->sock, 0);
+        }
+    } else {
+        rc = nbd_send_request(s->sock, request);
+    }
+    qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL, s);
+    s->send_coroutine = NULL;
+    qemu_co_mutex_unlock(&s->send_mutex);
+    return rc;
+}
+
+static void nbd_co_receive_reply(NbdClientSession *s,
+    struct nbd_request *request, struct nbd_reply *reply,
+    QEMUIOVector *qiov, int offset)
+{
+    int ret;
+
+    /* Wait until we're woken up by the read handler.  TODO: perhaps
+     * peek at the next reply and avoid yielding if it's ours?  */
+    qemu_coroutine_yield();
+    *reply = s->reply;
+    if (reply->handle != request->handle) {
+        reply->error = EIO;
+    } else {
+        if (qiov && reply->error == 0) {
+            ret = qemu_co_recvv(s->sock, qiov->iov, qiov->niov,
+                                offset, request->len);
+            if (ret != request->len) {
+                reply->error = EIO;
+            }
+        }
+
+        /* Tell the read handler to read another header.  */
+        s->reply.handle = 0;
+    }
+}
+
+static void nbd_coroutine_start(NbdClientSession *s,
+   struct nbd_request *request)
+{
+    int i;
+
+    /* Poor man semaphore.  The free_sema is locked when no other request
+     * can be accepted, and unlocked after receiving one reply.  */
+    if (s->in_flight >= MAX_NBD_REQUESTS - 1) {
+        qemu_co_mutex_lock(&s->free_sema);
+        assert(s->in_flight < MAX_NBD_REQUESTS);
+    }
+    s->in_flight++;
+
+    for (i = 0; i < MAX_NBD_REQUESTS; i++) {
+        if (s->recv_coroutine[i] == NULL) {
+            s->recv_coroutine[i] = qemu_coroutine_self();
+            break;
+        }
+    }
+
+    assert(i < MAX_NBD_REQUESTS);
+    request->handle = INDEX_TO_HANDLE(s, i);
+}
+
+static void nbd_coroutine_end(NbdClientSession *s,
+    struct nbd_request *request)
+{
+    int i = HANDLE_TO_INDEX(s, request->handle);
+    s->recv_coroutine[i] = NULL;
+    if (s->in_flight-- == MAX_NBD_REQUESTS) {
+        qemu_co_mutex_unlock(&s->free_sema);
+    }
+}
+
+static int nbd_co_readv_1(NbdClientSession *client, int64_t sector_num,
+                          int nb_sectors, QEMUIOVector *qiov,
+                          int offset)
+{
+    struct nbd_request request = { .type = NBD_CMD_READ };
+    struct nbd_reply reply;
+    ssize_t ret;
+
+    request.from = sector_num * 512;
+    request.len = nb_sectors * 512;
+
+    nbd_coroutine_start(client, &request);
+    ret = nbd_co_send_request(client, &request, NULL, 0);
+    if (ret < 0) {
+        reply.error = -ret;
+    } else {
+        nbd_co_receive_reply(client, &request, &reply, qiov, offset);
+    }
+    nbd_coroutine_end(client, &request);
+    return -reply.error;
+
+}
+
+static int nbd_co_writev_1(NbdClientSession *client, int64_t sector_num,
+                           int nb_sectors, QEMUIOVector *qiov,
+                           int offset)
+{
+    struct nbd_request request = { .type = NBD_CMD_WRITE };
+    struct nbd_reply reply;
+    ssize_t ret;
+
+    if (!bdrv_enable_write_cache(client->bs) &&
+        (client->nbdflags & NBD_FLAG_SEND_FUA)) {
+        request.type |= NBD_CMD_FLAG_FUA;
+    }
+
+    request.from = sector_num * 512;
+    request.len = nb_sectors * 512;
+
+    nbd_coroutine_start(client, &request);
+    ret = nbd_co_send_request(client, &request, qiov, offset);
+    if (ret < 0) {
+        reply.error = -ret;
+    } else {
+        nbd_co_receive_reply(client, &request, &reply, NULL, 0);
+    }
+    nbd_coroutine_end(client, &request);
+    return -reply.error;
+}
+
+/* qemu-nbd has a limit of slightly less than 1M per request.  Try to
+ * remain aligned to 4K. */
+#define NBD_MAX_SECTORS 2040
+
+int nbd_client_session_co_readv(NbdClientSession *client, int64_t sector_num,
+    int nb_sectors, QEMUIOVector *qiov)
+{
+    int offset = 0;
+    int ret;
+    while (nb_sectors > NBD_MAX_SECTORS) {
+        ret = nbd_co_readv_1(client, sector_num,
+                             NBD_MAX_SECTORS, qiov, offset);
+        if (ret < 0) {
+            return ret;
+        }
+        offset += NBD_MAX_SECTORS * 512;
+        sector_num += NBD_MAX_SECTORS;
+        nb_sectors -= NBD_MAX_SECTORS;
+    }
+    return nbd_co_readv_1(client, sector_num, nb_sectors, qiov, offset);
+}
+
+int nbd_client_session_co_writev(NbdClientSession *client, int64_t sector_num,
+                                 int nb_sectors, QEMUIOVector *qiov)
+{
+    int offset = 0;
+    int ret;
+    while (nb_sectors > NBD_MAX_SECTORS) {
+        ret = nbd_co_writev_1(client, sector_num,
+                              NBD_MAX_SECTORS, qiov, offset);
+        if (ret < 0) {
+            return ret;
+        }
+        offset += NBD_MAX_SECTORS * 512;
+        sector_num += NBD_MAX_SECTORS;
+        nb_sectors -= NBD_MAX_SECTORS;
+    }
+    return nbd_co_writev_1(client, sector_num, nb_sectors, qiov, offset);
+}
+
+int nbd_client_session_co_flush(NbdClientSession *client)
+{
+    struct nbd_request request = { .type = NBD_CMD_FLUSH };
+    struct nbd_reply reply;
+    ssize_t ret;
+
+    if (!(client->nbdflags & NBD_FLAG_SEND_FLUSH)) {
+        return 0;
+    }
+
+    if (client->nbdflags & NBD_FLAG_SEND_FUA) {
+        request.type |= NBD_CMD_FLAG_FUA;
+    }
+
+    request.from = 0;
+    request.len = 0;
+
+    nbd_coroutine_start(client, &request);
+    ret = nbd_co_send_request(client, &request, NULL, 0);
+    if (ret < 0) {
+        reply.error = -ret;
+    } else {
+        nbd_co_receive_reply(client, &request, &reply, NULL, 0);
+    }
+    nbd_coroutine_end(client, &request);
+    return -reply.error;
+}
+
+int nbd_client_session_co_discard(NbdClientSession *client, int64_t sector_num,
+    int nb_sectors)
+{
+    struct nbd_request request = { .type = NBD_CMD_TRIM };
+    struct nbd_reply reply;
+    ssize_t ret;
+
+    if (!(client->nbdflags & NBD_FLAG_SEND_TRIM)) {
+        return 0;
+    }
+    request.from = sector_num * 512;
+    request.len = nb_sectors * 512;
+
+    nbd_coroutine_start(client, &request);
+    ret = nbd_co_send_request(client, &request, NULL, 0);
+    if (ret < 0) {
+        reply.error = -ret;
+    } else {
+        nbd_co_receive_reply(client, &request, &reply, NULL, 0);
+    }
+    nbd_coroutine_end(client, &request);
+    return -reply.error;
+
+}
+
+static void nbd_teardown_connection(NbdClientSession *client)
+{
+    struct nbd_request request = {
+        .type = NBD_CMD_DISC,
+        .from = 0,
+        .len = 0
+    };
+
+    nbd_send_request(client->sock, &request);
+
+    /* finish any pending coroutines */
+    shutdown(client->sock, 2);
+    nbd_recv_coroutines_enter_all(client);
+
+    qemu_aio_set_fd_handler(client->sock, NULL, NULL, NULL);
+    closesocket(client->sock);
+    client->sock = -1;
+}
+
+void nbd_client_session_close(NbdClientSession *client)
+{
+    if (!client->bs) {
+        return;
+    }
+
+    nbd_teardown_connection(client);
+    client->bs = NULL;
+}
+
+int nbd_client_session_init(NbdClientSession *client, BlockDriverState *bs,
+    int sock, const char *export)
+{
+    int ret;
+
+    /* NBD handshake */
+    logout("session init %s\n", export);
+    qemu_set_block(sock);
+    ret = nbd_receive_negotiate(sock, export,
+                                &client->nbdflags, &client->size,
+                                &client->blocksize);
+    if (ret < 0) {
+        logout("Failed to negotiate with the NBD server\n");
+        closesocket(sock);
+        return ret;
+    }
+
+    qemu_co_mutex_init(&client->send_mutex);
+    qemu_co_mutex_init(&client->free_sema);
+    client->bs = bs;
+    client->sock = sock;
+
+    /* Now that we're connected, set the socket to be non-blocking and
+     * kick the reply mechanism.  */
+    qemu_set_nonblock(sock);
+    qemu_aio_set_fd_handler(sock, nbd_reply_ready, NULL, client);
+
+    logout("Established connection with NBD server\n");
+    return 0;
+}
diff --git a/block/nbd-client.h b/block/nbd-client.h
new file mode 100644
index 0000000..f2a6337
--- /dev/null
+++ b/block/nbd-client.h
@@ -0,0 +1,50 @@
+#ifndef NBD_CLIENT_H
+#define NBD_CLIENT_H
+
+#include "qemu-common.h"
+#include "block/nbd.h"
+#include "block/block_int.h"
+
+/* #define DEBUG_NBD */
+
+#if defined(DEBUG_NBD)
+#define logout(fmt, ...) \
+    fprintf(stderr, "nbd\t%-24s" fmt, __func__, ##__VA_ARGS__)
+#else
+#define logout(fmt, ...) ((void)0)
+#endif
+
+#define MAX_NBD_REQUESTS    16
+
+typedef struct NbdClientSession {
+    int sock;
+    uint32_t nbdflags;
+    off_t size;
+    size_t blocksize;
+
+    CoMutex send_mutex;
+    CoMutex free_sema;
+    Coroutine *send_coroutine;
+    int in_flight;
+
+    Coroutine *recv_coroutine[MAX_NBD_REQUESTS];
+    struct nbd_reply reply;
+
+    bool is_unix;
+
+    BlockDriverState *bs;
+} NbdClientSession;
+
+int nbd_client_session_init(NbdClientSession *client, BlockDriverState *bs,
+                            int sock, const char *export_name);
+void nbd_client_session_close(NbdClientSession *client);
+
+int nbd_client_session_co_discard(NbdClientSession *client, int64_t sector_num,
+                                  int nb_sectors);
+int nbd_client_session_co_flush(NbdClientSession *client);
+int nbd_client_session_co_writev(NbdClientSession *client, int64_t sector_num,
+                                 int nb_sectors, QEMUIOVector *qiov);
+int nbd_client_session_co_readv(NbdClientSession *client, int64_t sector_num,
+                                int nb_sectors, QEMUIOVector *qiov);
+
+#endif /* NBD_CLIENT_H */
diff --git a/block/nbd.c b/block/nbd.c
index c8deeee..4455a13 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -26,8 +26,7 @@
  * THE SOFTWARE.
  */
 
-#include "qemu-common.h"
-#include "block/nbd.h"
+#include "block/nbd-client.h"
 #include "qemu/uri.h"
 #include "block/block_int.h"
 #include "qemu/module.h"
@@ -40,37 +39,9 @@
 
 #define EN_OPTSTR ":exportname="
 
-/* #define DEBUG_NBD */
-
-#if defined(DEBUG_NBD)
-#define logout(fmt, ...) \
-                fprintf(stderr, "nbd\t%-24s" fmt, __func__, ##__VA_ARGS__)
-#else
-#define logout(fmt, ...) ((void)0)
-#endif
-
-#define MAX_NBD_REQUESTS	16
-#define HANDLE_TO_INDEX(bs, handle) ((handle) ^ ((uint64_t)(intptr_t)bs))
-#define INDEX_TO_HANDLE(bs, index)  ((index)  ^ ((uint64_t)(intptr_t)bs))
-
 typedef struct BDRVNBDState {
-    int sock;
-    uint32_t nbdflags;
-    off_t size;
-    size_t blocksize;
-
-    CoMutex send_mutex;
-    CoMutex free_sema;
-    Coroutine *send_coroutine;
-    int in_flight;
-
-    Coroutine *recv_coroutine[MAX_NBD_REQUESTS];
-    struct nbd_reply reply;
-
-    bool is_unix;
+    NbdClientSession client;
     QemuOpts *socket_opts;
-
-    char *export_name; /* An NBD server may export several devices */
 } BDRVNBDState;
 
 static int nbd_parse_uri(const char *filename, QDict *options)
@@ -217,7 +188,7 @@
     g_free(file);
 }
 
-static int nbd_config(BDRVNBDState *s, QDict *options)
+static int nbd_config(BDRVNBDState *s, QDict *options, char **export)
 {
     Error *local_err = NULL;
 
@@ -227,9 +198,9 @@
                           "be used at the same time.");
             return -EINVAL;
         }
-        s->is_unix = true;
+        s->client.is_unix = true;
     } else if (qdict_haskey(options, "host")) {
-        s->is_unix = false;
+        s->client.is_unix = false;
     } else {
         return -EINVAL;
     }
@@ -247,162 +218,20 @@
         qemu_opt_set_number(s->socket_opts, "port", NBD_DEFAULT_PORT);
     }
 
-    s->export_name = g_strdup(qdict_get_try_str(options, "export"));
-    if (s->export_name) {
+    *export = g_strdup(qdict_get_try_str(options, "export"));
+    if (*export) {
         qdict_del(options, "export");
     }
 
     return 0;
 }
 
-
-static void nbd_coroutine_start(BDRVNBDState *s, struct nbd_request *request)
-{
-    int i;
-
-    /* Poor man semaphore.  The free_sema is locked when no other request
-     * can be accepted, and unlocked after receiving one reply.  */
-    if (s->in_flight >= MAX_NBD_REQUESTS - 1) {
-        qemu_co_mutex_lock(&s->free_sema);
-        assert(s->in_flight < MAX_NBD_REQUESTS);
-    }
-    s->in_flight++;
-
-    for (i = 0; i < MAX_NBD_REQUESTS; i++) {
-        if (s->recv_coroutine[i] == NULL) {
-            s->recv_coroutine[i] = qemu_coroutine_self();
-            break;
-        }
-    }
-
-    assert(i < MAX_NBD_REQUESTS);
-    request->handle = INDEX_TO_HANDLE(s, i);
-}
-
-static void nbd_reply_ready(void *opaque)
-{
-    BDRVNBDState *s = opaque;
-    uint64_t i;
-    int ret;
-
-    if (s->reply.handle == 0) {
-        /* No reply already in flight.  Fetch a header.  It is possible
-         * that another thread has done the same thing in parallel, so
-         * the socket is not readable anymore.
-         */
-        ret = nbd_receive_reply(s->sock, &s->reply);
-        if (ret == -EAGAIN) {
-            return;
-        }
-        if (ret < 0) {
-            s->reply.handle = 0;
-            goto fail;
-        }
-    }
-
-    /* There's no need for a mutex on the receive side, because the
-     * handler acts as a synchronization point and ensures that only
-     * one coroutine is called until the reply finishes.  */
-    i = HANDLE_TO_INDEX(s, s->reply.handle);
-    if (i >= MAX_NBD_REQUESTS) {
-        goto fail;
-    }
-
-    if (s->recv_coroutine[i]) {
-        qemu_coroutine_enter(s->recv_coroutine[i], NULL);
-        return;
-    }
-
-fail:
-    for (i = 0; i < MAX_NBD_REQUESTS; i++) {
-        if (s->recv_coroutine[i]) {
-            qemu_coroutine_enter(s->recv_coroutine[i], NULL);
-        }
-    }
-}
-
-static void nbd_restart_write(void *opaque)
-{
-    BDRVNBDState *s = opaque;
-    qemu_coroutine_enter(s->send_coroutine, NULL);
-}
-
-static int nbd_co_send_request(BDRVNBDState *s, struct nbd_request *request,
-                               QEMUIOVector *qiov, int offset)
-{
-    int rc, ret;
-
-    qemu_co_mutex_lock(&s->send_mutex);
-    s->send_coroutine = qemu_coroutine_self();
-    qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, nbd_restart_write, s);
-    if (qiov) {
-        if (!s->is_unix) {
-            socket_set_cork(s->sock, 1);
-        }
-        rc = nbd_send_request(s->sock, request);
-        if (rc >= 0) {
-            ret = qemu_co_sendv(s->sock, qiov->iov, qiov->niov,
-                                offset, request->len);
-            if (ret != request->len) {
-                rc = -EIO;
-            }
-        }
-        if (!s->is_unix) {
-            socket_set_cork(s->sock, 0);
-        }
-    } else {
-        rc = nbd_send_request(s->sock, request);
-    }
-    qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL, s);
-    s->send_coroutine = NULL;
-    qemu_co_mutex_unlock(&s->send_mutex);
-    return rc;
-}
-
-static void nbd_co_receive_reply(BDRVNBDState *s, struct nbd_request *request,
-                                 struct nbd_reply *reply,
-                                 QEMUIOVector *qiov, int offset)
-{
-    int ret;
-
-    /* Wait until we're woken up by the read handler.  TODO: perhaps
-     * peek at the next reply and avoid yielding if it's ours?  */
-    qemu_coroutine_yield();
-    *reply = s->reply;
-    if (reply->handle != request->handle) {
-        reply->error = EIO;
-    } else {
-        if (qiov && reply->error == 0) {
-            ret = qemu_co_recvv(s->sock, qiov->iov, qiov->niov,
-                                offset, request->len);
-            if (ret != request->len) {
-                reply->error = EIO;
-            }
-        }
-
-        /* Tell the read handler to read another header.  */
-        s->reply.handle = 0;
-    }
-}
-
-static void nbd_coroutine_end(BDRVNBDState *s, struct nbd_request *request)
-{
-    int i = HANDLE_TO_INDEX(s, request->handle);
-    s->recv_coroutine[i] = NULL;
-    if (s->in_flight-- == MAX_NBD_REQUESTS) {
-        qemu_co_mutex_unlock(&s->free_sema);
-    }
-}
-
 static int nbd_establish_connection(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
     int sock;
-    int ret;
-    off_t size;
-    size_t blocksize;
 
-    if (s->is_unix) {
+    if (s->client.is_unix) {
         sock = unix_socket_outgoing(qemu_opt_get(s->socket_opts, "path"));
     } else {
         sock = tcp_socket_outgoing_opts(s->socket_opts);
@@ -417,53 +246,18 @@
         return -errno;
     }
 
-    /* NBD handshake */
-    ret = nbd_receive_negotiate(sock, s->export_name, &s->nbdflags, &size,
-                                &blocksize);
-    if (ret < 0) {
-        logout("Failed to negotiate with the NBD server\n");
-        closesocket(sock);
-        return ret;
-    }
-
-    /* Now that we're connected, set the socket to be non-blocking and
-     * kick the reply mechanism.  */
-    qemu_set_nonblock(sock);
-    qemu_aio_set_fd_handler(sock, nbd_reply_ready, NULL, s);
-
-    s->sock = sock;
-    s->size = size;
-    s->blocksize = blocksize;
-
-    logout("Established connection with NBD server\n");
-    return 0;
-}
-
-static void nbd_teardown_connection(BlockDriverState *bs)
-{
-    BDRVNBDState *s = bs->opaque;
-    struct nbd_request request;
-
-    request.type = NBD_CMD_DISC;
-    request.from = 0;
-    request.len = 0;
-    nbd_send_request(s->sock, &request);
-
-    qemu_aio_set_fd_handler(s->sock, NULL, NULL, NULL);
-    closesocket(s->sock);
+    return sock;
 }
 
 static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
     BDRVNBDState *s = bs->opaque;
-    int result;
-
-    qemu_co_mutex_init(&s->send_mutex);
-    qemu_co_mutex_init(&s->free_sema);
+    char *export = NULL;
+    int result, sock;
 
     /* Pop the config into our state object. Exit if invalid. */
-    result = nbd_config(s, options);
+    result = nbd_config(s, options, &export);
     if (result != 0) {
         return result;
     }
@@ -471,172 +265,64 @@
     /* establish TCP connection, return error if it fails
      * TODO: Configurable retry-until-timeout behaviour.
      */
-    result = nbd_establish_connection(bs);
+    sock = nbd_establish_connection(bs);
+    if (sock < 0) {
+        return sock;
+    }
 
+    /* NBD handshake */
+    result = nbd_client_session_init(&s->client, bs, sock, export);
+    g_free(export);
     return result;
 }
 
-static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num,
-                          int nb_sectors, QEMUIOVector *qiov,
-                          int offset)
-{
-    BDRVNBDState *s = bs->opaque;
-    struct nbd_request request;
-    struct nbd_reply reply;
-    ssize_t ret;
-
-    request.type = NBD_CMD_READ;
-    request.from = sector_num * 512;
-    request.len = nb_sectors * 512;
-
-    nbd_coroutine_start(s, &request);
-    ret = nbd_co_send_request(s, &request, NULL, 0);
-    if (ret < 0) {
-        reply.error = -ret;
-    } else {
-        nbd_co_receive_reply(s, &request, &reply, qiov, offset);
-    }
-    nbd_coroutine_end(s, &request);
-    return -reply.error;
-
-}
-
-static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,
-                           int nb_sectors, QEMUIOVector *qiov,
-                           int offset)
-{
-    BDRVNBDState *s = bs->opaque;
-    struct nbd_request request;
-    struct nbd_reply reply;
-    ssize_t ret;
-
-    request.type = NBD_CMD_WRITE;
-    if (!bdrv_enable_write_cache(bs) && (s->nbdflags & NBD_FLAG_SEND_FUA)) {
-        request.type |= NBD_CMD_FLAG_FUA;
-    }
-
-    request.from = sector_num * 512;
-    request.len = nb_sectors * 512;
-
-    nbd_coroutine_start(s, &request);
-    ret = nbd_co_send_request(s, &request, qiov, offset);
-    if (ret < 0) {
-        reply.error = -ret;
-    } else {
-        nbd_co_receive_reply(s, &request, &reply, NULL, 0);
-    }
-    nbd_coroutine_end(s, &request);
-    return -reply.error;
-}
-
-/* qemu-nbd has a limit of slightly less than 1M per request.  Try to
- * remain aligned to 4K. */
-#define NBD_MAX_SECTORS 2040
-
 static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num,
                         int nb_sectors, QEMUIOVector *qiov)
 {
-    int offset = 0;
-    int ret;
-    while (nb_sectors > NBD_MAX_SECTORS) {
-        ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
-        if (ret < 0) {
-            return ret;
-        }
-        offset += NBD_MAX_SECTORS * 512;
-        sector_num += NBD_MAX_SECTORS;
-        nb_sectors -= NBD_MAX_SECTORS;
-    }
-    return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset);
+    BDRVNBDState *s = bs->opaque;
+
+    return nbd_client_session_co_readv(&s->client, sector_num,
+                                       nb_sectors, qiov);
 }
 
 static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num,
                          int nb_sectors, QEMUIOVector *qiov)
 {
-    int offset = 0;
-    int ret;
-    while (nb_sectors > NBD_MAX_SECTORS) {
-        ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
-        if (ret < 0) {
-            return ret;
-        }
-        offset += NBD_MAX_SECTORS * 512;
-        sector_num += NBD_MAX_SECTORS;
-        nb_sectors -= NBD_MAX_SECTORS;
-    }
-    return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset);
+    BDRVNBDState *s = bs->opaque;
+
+    return nbd_client_session_co_writev(&s->client, sector_num,
+                                        nb_sectors, qiov);
 }
 
 static int nbd_co_flush(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
-    struct nbd_request request;
-    struct nbd_reply reply;
-    ssize_t ret;
 
-    if (!(s->nbdflags & NBD_FLAG_SEND_FLUSH)) {
-        return 0;
-    }
-
-    request.type = NBD_CMD_FLUSH;
-    if (s->nbdflags & NBD_FLAG_SEND_FUA) {
-        request.type |= NBD_CMD_FLAG_FUA;
-    }
-
-    request.from = 0;
-    request.len = 0;
-
-    nbd_coroutine_start(s, &request);
-    ret = nbd_co_send_request(s, &request, NULL, 0);
-    if (ret < 0) {
-        reply.error = -ret;
-    } else {
-        nbd_co_receive_reply(s, &request, &reply, NULL, 0);
-    }
-    nbd_coroutine_end(s, &request);
-    return -reply.error;
+    return nbd_client_session_co_flush(&s->client);
 }
 
 static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num,
                           int nb_sectors)
 {
     BDRVNBDState *s = bs->opaque;
-    struct nbd_request request;
-    struct nbd_reply reply;
-    ssize_t ret;
 
-    if (!(s->nbdflags & NBD_FLAG_SEND_TRIM)) {
-        return 0;
-    }
-    request.type = NBD_CMD_TRIM;
-    request.from = sector_num * 512;
-    request.len = nb_sectors * 512;
-
-    nbd_coroutine_start(s, &request);
-    ret = nbd_co_send_request(s, &request, NULL, 0);
-    if (ret < 0) {
-        reply.error = -ret;
-    } else {
-        nbd_co_receive_reply(s, &request, &reply, NULL, 0);
-    }
-    nbd_coroutine_end(s, &request);
-    return -reply.error;
+    return nbd_client_session_co_discard(&s->client, sector_num,
+                                         nb_sectors);
 }
 
 static void nbd_close(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
-    g_free(s->export_name);
-    qemu_opts_del(s->socket_opts);
 
-    nbd_teardown_connection(bs);
+    qemu_opts_del(s->socket_opts);
+    nbd_client_session_close(&s->client);
 }
 
 static int64_t nbd_getlength(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
 
-    return s->size;
+    return s->client.size;
 }
 
 static BlockDriver bdrv_nbd = {
diff --git a/blockdev.c b/blockdev.c
index 44755e1..6a85961 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1523,7 +1523,7 @@
 }
 
 void qmp_change_blockdev(const char *device, const char *filename,
-                         bool has_format, const char *format, Error **errp)
+                         const char *format, Error **errp)
 {
     BlockDriverState *bs;
     BlockDriver *drv = NULL;
diff --git a/hw/display/qxl.c b/hw/display/qxl.c
index efdefd6..e4f172e 100644
--- a/hw/display/qxl.c
+++ b/hw/display/qxl.c
@@ -1144,8 +1144,14 @@
 
 static void qxl_hard_reset(PCIQXLDevice *d, int loadvm)
 {
+    bool startstop = qemu_spice_display_is_running(&d->ssd);
+
     trace_qxl_hard_reset(d->id, loadvm);
 
+    if (startstop) {
+        qemu_spice_display_stop();
+    }
+
     qxl_spice_reset_cursor(d);
     qxl_spice_reset_image_cache(d);
     qxl_reset_surfaces(d);
@@ -1159,6 +1165,10 @@
     }
     qemu_spice_create_host_memslot(&d->ssd);
     qxl_soft_reset(d);
+
+    if (startstop) {
+        qemu_spice_display_start();
+    }
 }
 
 static void qxl_reset_handler(DeviceState *dev)
diff --git a/include/sysemu/blockdev.h b/include/sysemu/blockdev.h
index 1082091..134712b 100644
--- a/include/sysemu/blockdev.h
+++ b/include/sysemu/blockdev.h
@@ -64,7 +64,7 @@
 DriveInfo *add_init_drive(const char *opts);
 
 void qmp_change_blockdev(const char *device, const char *filename,
-                         bool has_format, const char *format, Error **errp);
+                         const char *format, Error **errp);
 void do_commit(Monitor *mon, const QDict *qdict);
 int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data);
 #endif
diff --git a/include/sysemu/char.h b/include/sysemu/char.h
index ad101d9..b81a6ff 100644
--- a/include/sysemu/char.h
+++ b/include/sysemu/char.h
@@ -69,6 +69,7 @@
     void (*chr_accept_input)(struct CharDriverState *chr);
     void (*chr_set_echo)(struct CharDriverState *chr, bool echo);
     void (*chr_set_fe_open)(struct CharDriverState *chr, int fe_open);
+    void (*chr_fe_event)(struct CharDriverState *chr, int event);
     void *opaque;
     char *label;
     char *filename;
@@ -138,6 +139,15 @@
 void qemu_chr_fe_set_open(struct CharDriverState *chr, int fe_open);
 
 /**
+ * @qemu_chr_fe_event:
+ *
+ * Send an event from the front end to the back end.
+ *
+ * @event the event to send
+ */
+void qemu_chr_fe_event(CharDriverState *s, int event);
+
+/**
  * @qemu_chr_fe_printf:
  *
  * Write to a character backend using a printf style interface.
diff --git a/include/ui/qemu-spice.h b/include/ui/qemu-spice.h
index 86c75c7..a93b4b2 100644
--- a/include/ui/qemu-spice.h
+++ b/include/ui/qemu-spice.h
@@ -18,6 +18,8 @@
 #ifndef QEMU_SPICE_H
 #define QEMU_SPICE_H
 
+#include "config-host.h"
+
 #ifdef CONFIG_SPICE
 
 #include <spice.h>
diff --git a/libcacard/vscclient.c b/libcacard/vscclient.c
index f1d46d3..24f7088 100644
--- a/libcacard/vscclient.c
+++ b/libcacard/vscclient.c
@@ -58,7 +58,7 @@
 static guint socket_tag;
 
 static void
-update_socket_watch(gboolean out);
+update_socket_watch(void);
 
 static gboolean
 do_socket_send(GIOChannel *source,
@@ -80,7 +80,7 @@
     g_byte_array_remove_range(socket_to_send, 0, bw);
 
     if (socket_to_send->len == 0) {
-        update_socket_watch(FALSE);
+        update_socket_watch();
         return FALSE;
     }
     return TRUE;
@@ -89,7 +89,7 @@
 static gboolean
 socket_prepare_sending(gpointer user_data)
 {
-    update_socket_watch(TRUE);
+    update_socket_watch();
 
     return FALSE;
 }
@@ -440,8 +440,10 @@
 }
 
 static void
-update_socket_watch(gboolean out)
+update_socket_watch(void)
 {
+    gboolean out = socket_to_send->len > 0;
+
     if (socket_tag != 0) {
         g_source_remove(socket_tag);
     }
diff --git a/nbd.c b/nbd.c
index f847940..030f56b 100644
--- a/nbd.c
+++ b/nbd.c
@@ -443,7 +443,6 @@
 
     TRACE("Receiving negotiation.");
 
-    qemu_set_block(csock);
     rc = -EINVAL;
 
     if (read_sync(csock, buf, 8) != 8) {
@@ -558,7 +557,6 @@
     rc = 0;
 
 fail:
-    qemu_set_nonblock(csock);
     return rc;
 }
 
diff --git a/qemu-char.c b/qemu-char.c
index e00f84c..418dc69 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -3353,6 +3353,13 @@
     }
 }
 
+void qemu_chr_fe_event(struct CharDriverState *chr, int event)
+{
+    if (chr->chr_fe_event) {
+        chr->chr_fe_event(chr, event);
+    }
+}
+
 int qemu_chr_fe_add_watch(CharDriverState *s, GIOCondition cond,
                           GIOFunc func, void *user_data)
 {
diff --git a/qmp.c b/qmp.c
index 4c149b3..1d7a04d 100644
--- a/qmp.c
+++ b/qmp.c
@@ -400,7 +400,7 @@
     if (strcmp(device, "vnc") == 0) {
         qmp_change_vnc(target, has_arg, arg, err);
     } else {
-        qmp_change_blockdev(device, target, has_arg, arg, err);
+        qmp_change_blockdev(device, target, arg, err);
     }
 }
 
diff --git a/spice-qemu-char.c b/spice-qemu-char.c
index 6d147a7..16439c5 100644
--- a/spice-qemu-char.c
+++ b/spice-qemu-char.c
@@ -11,7 +11,6 @@
 typedef struct SpiceCharDriver {
     CharDriverState*      chr;
     SpiceCharDeviceInstance     sin;
-    char                  *subtype;
     bool                  active;
     bool                  blocked;
     const uint8_t         *datapos;
@@ -223,6 +222,15 @@
     }
 }
 
+static void spice_chr_fe_event(struct CharDriverState *chr, int event)
+{
+#if SPICE_SERVER_VERSION >= 0x000c02
+    SpiceCharDriver *s = chr->opaque;
+
+    spice_server_port_event(&s->sin, event);
+#endif
+}
+
 static void print_allowed_subtypes(void)
 {
     const char** psubtype;
@@ -256,6 +264,7 @@
     chr->chr_close = spice_chr_close;
     chr->chr_set_fe_open = spice_chr_set_fe_open;
     chr->explicit_be_open = true;
+    chr->chr_fe_event = spice_chr_fe_event;
 
     QLIST_INSERT_HEAD(&spice_chars, s, next);
 
diff --git a/ui/spice-core.c b/ui/spice-core.c
index e4d533d..4cce3b3 100644
--- a/ui/spice-core.c
+++ b/ui/spice-core.c
@@ -47,6 +47,7 @@
 static char *auth_passwd;
 static time_t auth_expires = TIME_MAX;
 static int spice_migration_completed;
+static int spice_display_is_running;
 int using_spice = 0;
 
 static QemuThread me;
@@ -622,9 +623,7 @@
 {
     if (running) {
         qemu_spice_display_start();
-        spice_server_vm_start(spice_server);
     } else {
-        spice_server_vm_stop(spice_server);
         qemu_spice_display_stop();
     }
 }
@@ -776,6 +775,8 @@
     if (str) {
         int streaming_video = parse_stream_video(str);
         spice_server_set_streaming_video(spice_server, streaming_video);
+    } else {
+        spice_server_set_streaming_video(spice_server, SPICE_STREAM_VIDEO_OFF);
     }
 
     spice_server_set_agent_mouse
@@ -902,6 +903,23 @@
     }
 }
 
+void qemu_spice_display_start(void)
+{
+    spice_display_is_running = true;
+    spice_server_vm_start(spice_server);
+}
+
+void qemu_spice_display_stop(void)
+{
+    spice_server_vm_stop(spice_server);
+    spice_display_is_running = false;
+}
+
+int qemu_spice_display_is_running(SimpleSpiceDisplay *ssd)
+{
+    return spice_display_is_running;
+}
+
 static void spice_register_config(void)
 {
     qemu_add_opts(&qemu_spice_opts);
diff --git a/ui/spice-display.c b/ui/spice-display.c
index f23a318..9bb42f1 100644
--- a/ui/spice-display.c
+++ b/ui/spice-display.c
@@ -126,23 +126,6 @@
     spice_qxl_wakeup(&ssd->qxl);
 }
 
-static int spice_display_is_running;
-
-void qemu_spice_display_start(void)
-{
-    spice_display_is_running = true;
-}
-
-void qemu_spice_display_stop(void)
-{
-    spice_display_is_running = false;
-}
-
-int qemu_spice_display_is_running(SimpleSpiceDisplay *ssd)
-{
-    return spice_display_is_running;
-}
-
 static void qemu_spice_create_one_update(SimpleSpiceDisplay *ssd,
                                          QXLRect *rect)
 {