diff --git a/nbd/server.c b/nbd/server.c
index ba25ce3604..8752885509 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -93,13 +93,45 @@ static void nbd_set_handlers(NBDClient *client);
 static void nbd_unset_handlers(NBDClient *client);
 static void nbd_update_can_read(NBDClient *client);
 
-static ssize_t drop_sync(int fd, size_t size)
+static void nbd_negotiate_continue(void *opaque)
+{
+    qemu_coroutine_enter(opaque, NULL);
+}
+
+static ssize_t nbd_negotiate_read(int fd, void *buffer, size_t size)
+{
+    ssize_t ret;
+
+    assert(qemu_in_coroutine());
+    /* Negotiation are always in main loop. */
+    qemu_set_fd_handler(fd, nbd_negotiate_continue, NULL,
+                        qemu_coroutine_self());
+    ret = read_sync(fd, buffer, size);
+    qemu_set_fd_handler(fd, NULL, NULL, NULL);
+    return ret;
+
+}
+
+static ssize_t nbd_negotiate_write(int fd, void *buffer, size_t size)
+{
+    ssize_t ret;
+
+    assert(qemu_in_coroutine());
+    /* Negotiation are always in main loop. */
+    qemu_set_fd_handler(fd, NULL, nbd_negotiate_continue,
+                        qemu_coroutine_self());
+    ret = write_sync(fd, buffer, size);
+    qemu_set_fd_handler(fd, NULL, NULL, NULL);
+    return ret;
+}
+
+static ssize_t nbd_negotiate_drop_sync(int fd, size_t size)
 {
     ssize_t ret, dropped = size;
     uint8_t *buffer = g_malloc(MIN(65536, size));
 
     while (size > 0) {
-        ret = read_sync(fd, buffer, MIN(65536, size));
+        ret = nbd_negotiate_read(fd, buffer, MIN(65536, size));
         if (ret < 0) {
             g_free(buffer);
             return ret;
@@ -140,96 +172,96 @@ static ssize_t drop_sync(int fd, size_t size)
 
 */
 
-static int nbd_send_rep(int csock, uint32_t type, uint32_t opt)
+static int nbd_negotiate_send_rep(int csock, uint32_t type, uint32_t opt)
 {
     uint64_t magic;
     uint32_t len;
 
     magic = cpu_to_be64(NBD_REP_MAGIC);
-    if (write_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
+    if (nbd_negotiate_write(csock, &magic, sizeof(magic)) != sizeof(magic)) {
         LOG("write failed (rep magic)");
         return -EINVAL;
     }
     opt = cpu_to_be32(opt);
-    if (write_sync(csock, &opt, sizeof(opt)) != sizeof(opt)) {
+    if (nbd_negotiate_write(csock, &opt, sizeof(opt)) != sizeof(opt)) {
         LOG("write failed (rep opt)");
         return -EINVAL;
     }
     type = cpu_to_be32(type);
-    if (write_sync(csock, &type, sizeof(type)) != sizeof(type)) {
+    if (nbd_negotiate_write(csock, &type, sizeof(type)) != sizeof(type)) {
         LOG("write failed (rep type)");
         return -EINVAL;
     }
     len = cpu_to_be32(0);
-    if (write_sync(csock, &len, sizeof(len)) != sizeof(len)) {
+    if (nbd_negotiate_write(csock, &len, sizeof(len)) != sizeof(len)) {
         LOG("write failed (rep data length)");
         return -EINVAL;
     }
     return 0;
 }
 
-static int nbd_send_rep_list(int csock, NBDExport *exp)
+static int nbd_negotiate_send_rep_list(int csock, NBDExport *exp)
 {
     uint64_t magic, name_len;
     uint32_t opt, type, len;
 
     name_len = strlen(exp->name);
     magic = cpu_to_be64(NBD_REP_MAGIC);
-    if (write_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
+    if (nbd_negotiate_write(csock, &magic, sizeof(magic)) != sizeof(magic)) {
         LOG("write failed (magic)");
         return -EINVAL;
      }
     opt = cpu_to_be32(NBD_OPT_LIST);
-    if (write_sync(csock, &opt, sizeof(opt)) != sizeof(opt)) {
+    if (nbd_negotiate_write(csock, &opt, sizeof(opt)) != sizeof(opt)) {
         LOG("write failed (opt)");
         return -EINVAL;
     }
     type = cpu_to_be32(NBD_REP_SERVER);
-    if (write_sync(csock, &type, sizeof(type)) != sizeof(type)) {
+    if (nbd_negotiate_write(csock, &type, sizeof(type)) != sizeof(type)) {
         LOG("write failed (reply type)");
         return -EINVAL;
     }
     len = cpu_to_be32(name_len + sizeof(len));
-    if (write_sync(csock, &len, sizeof(len)) != sizeof(len)) {
+    if (nbd_negotiate_write(csock, &len, sizeof(len)) != sizeof(len)) {
         LOG("write failed (length)");
         return -EINVAL;
     }
     len = cpu_to_be32(name_len);
-    if (write_sync(csock, &len, sizeof(len)) != sizeof(len)) {
+    if (nbd_negotiate_write(csock, &len, sizeof(len)) != sizeof(len)) {
         LOG("write failed (length)");
         return -EINVAL;
     }
-    if (write_sync(csock, exp->name, name_len) != name_len) {
+    if (nbd_negotiate_write(csock, exp->name, name_len) != name_len) {
         LOG("write failed (buffer)");
         return -EINVAL;
     }
     return 0;
 }
 
-static int nbd_handle_list(NBDClient *client, uint32_t length)
+static int nbd_negotiate_handle_list(NBDClient *client, uint32_t length)
 {
     int csock;
     NBDExport *exp;
 
     csock = client->sock;
     if (length) {
-        if (drop_sync(csock, length) != length) {
+        if (nbd_negotiate_drop_sync(csock, length) != length) {
             return -EIO;
         }
-        return nbd_send_rep(csock, NBD_REP_ERR_INVALID, NBD_OPT_LIST);
+        return nbd_negotiate_send_rep(csock, NBD_REP_ERR_INVALID, NBD_OPT_LIST);
     }
 
     /* For each export, send a NBD_REP_SERVER reply. */
     QTAILQ_FOREACH(exp, &exports, next) {
-        if (nbd_send_rep_list(csock, exp)) {
+        if (nbd_negotiate_send_rep_list(csock, exp)) {
             return -EINVAL;
         }
     }
     /* Finish with a NBD_REP_ACK. */
-    return nbd_send_rep(csock, NBD_REP_ACK, NBD_OPT_LIST);
+    return nbd_negotiate_send_rep(csock, NBD_REP_ACK, NBD_OPT_LIST);
 }
 
-static int nbd_handle_export_name(NBDClient *client, uint32_t length)
+static int nbd_negotiate_handle_export_name(NBDClient *client, uint32_t length)
 {
     int rc = -EINVAL, csock = client->sock;
     char name[256];
@@ -242,7 +274,7 @@ static int nbd_handle_export_name(NBDClient *client, uint32_t length)
         LOG("Bad length received");
         goto fail;
     }
-    if (read_sync(csock, name, length) != length) {
+    if (nbd_negotiate_read(csock, name, length) != length) {
         LOG("read failed");
         goto fail;
     }
@@ -261,7 +293,7 @@ fail:
     return rc;
 }
 
-static int nbd_receive_options(NBDClient *client)
+static int nbd_negotiate_options(NBDClient *client)
 {
     int csock = client->sock;
     uint32_t flags;
@@ -280,7 +312,7 @@ static int nbd_receive_options(NBDClient *client)
         ...           Rest of request
     */
 
-    if (read_sync(csock, &flags, sizeof(flags)) != sizeof(flags)) {
+    if (nbd_negotiate_read(csock, &flags, sizeof(flags)) != sizeof(flags)) {
         LOG("read failed");
         return -EIO;
     }
@@ -296,7 +328,7 @@ static int nbd_receive_options(NBDClient *client)
         uint32_t tmp, length;
         uint64_t magic;
 
-        if (read_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
+        if (nbd_negotiate_read(csock, &magic, sizeof(magic)) != sizeof(magic)) {
             LOG("read failed");
             return -EINVAL;
         }
@@ -306,12 +338,13 @@ static int nbd_receive_options(NBDClient *client)
             return -EINVAL;
         }
 
-        if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
+        if (nbd_negotiate_read(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
             LOG("read failed");
             return -EINVAL;
         }
 
-        if (read_sync(csock, &length, sizeof(length)) != sizeof(length)) {
+        if (nbd_negotiate_read(csock, &length,
+                               sizeof(length)) != sizeof(length)) {
             LOG("read failed");
             return -EINVAL;
         }
@@ -320,7 +353,7 @@ static int nbd_receive_options(NBDClient *client)
         TRACE("Checking option");
         switch (be32_to_cpu(tmp)) {
         case NBD_OPT_LIST:
-            ret = nbd_handle_list(client, length);
+            ret = nbd_negotiate_handle_list(client, length);
             if (ret < 0) {
                 return ret;
             }
@@ -330,19 +363,25 @@ static int nbd_receive_options(NBDClient *client)
             return -EINVAL;
 
         case NBD_OPT_EXPORT_NAME:
-            return nbd_handle_export_name(client, length);
+            return nbd_negotiate_handle_export_name(client, length);
 
         default:
             tmp = be32_to_cpu(tmp);
             LOG("Unsupported option 0x%x", tmp);
-            nbd_send_rep(client->sock, NBD_REP_ERR_UNSUP, tmp);
+            nbd_negotiate_send_rep(client->sock, NBD_REP_ERR_UNSUP, tmp);
             return -EINVAL;
         }
     }
 }
 
-static int nbd_send_negotiate(NBDClient *client)
+typedef struct {
+    NBDClient *client;
+    Coroutine *co;
+} NBDClientNewData;
+
+static coroutine_fn int nbd_negotiate(NBDClientNewData *data)
 {
+    NBDClient *client = data->client;
     int csock = client->sock;
     char buf[8 + 8 + 8 + 128];
     int rc;
@@ -368,7 +407,6 @@ static int nbd_send_negotiate(NBDClient *client)
         [28 .. 151]   reserved     (0)
      */
 
-    qemu_set_block(csock);
     rc = -EINVAL;
 
     TRACE("Beginning negotiation.");
@@ -385,16 +423,16 @@ static int nbd_send_negotiate(NBDClient *client)
     }
 
     if (client->exp) {
-        if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
+        if (nbd_negotiate_write(csock, buf, sizeof(buf)) != sizeof(buf)) {
             LOG("write failed");
             goto fail;
         }
     } else {
-        if (write_sync(csock, buf, 18) != 18) {
+        if (nbd_negotiate_write(csock, buf, 18) != 18) {
             LOG("write failed");
             goto fail;
         }
-        rc = nbd_receive_options(client);
+        rc = nbd_negotiate_options(client);
         if (rc != 0) {
             LOG("option negotiation failed");
             goto fail;
@@ -403,7 +441,8 @@ static int nbd_send_negotiate(NBDClient *client)
         assert ((client->exp->nbdflags & ~65535) == 0);
         cpu_to_be64w((uint64_t*)(buf + 18), client->exp->size);
         cpu_to_be16w((uint16_t*)(buf + 26), client->exp->nbdflags | myflags);
-        if (write_sync(csock, buf + 18, sizeof(buf) - 18) != sizeof(buf) - 18) {
+        if (nbd_negotiate_write(csock, buf + 18,
+                                sizeof(buf) - 18) != sizeof(buf) - 18) {
             LOG("write failed");
             goto fail;
         }
@@ -412,7 +451,6 @@ static int nbd_send_negotiate(NBDClient *client)
     TRACE("Negotiation succeeded.");
     rc = 0;
 fail:
-    qemu_set_nonblock(csock);
     return rc;
 }
 
@@ -1028,25 +1066,43 @@ static void nbd_update_can_read(NBDClient *client)
     }
 }
 
-void nbd_client_new(NBDExport *exp, int csock, void (*close_fn)(NBDClient *))
+static coroutine_fn void nbd_co_client_start(void *opaque)
 {
-    NBDClient *client;
-    client = g_malloc0(sizeof(NBDClient));
-    client->refcount = 1;
-    client->exp = exp;
-    client->sock = csock;
-    client->can_read = true;
-    if (nbd_send_negotiate(client)) {
-        shutdown(client->sock, 2);
-        close_fn(client);
-        return;
+    NBDClientNewData *data = opaque;
+    NBDClient *client = data->client;
+    NBDExport *exp = client->exp;
+
+    if (exp) {
+        nbd_export_get(exp);
+    }
+    if (nbd_negotiate(data)) {
+        shutdown(client->sock, 2);
+        client->close(client);
+        goto out;
     }
-    client->close = close_fn;
     qemu_co_mutex_init(&client->send_lock);
     nbd_set_handlers(client);
 
     if (exp) {
         QTAILQ_INSERT_TAIL(&exp->clients, client, next);
-        nbd_export_get(exp);
     }
+out:
+    g_free(data);
+}
+
+void nbd_client_new(NBDExport *exp, int csock, void (*close_fn)(NBDClient *))
+{
+    NBDClient *client;
+    NBDClientNewData *data = g_new(NBDClientNewData, 1);
+
+    client = g_malloc0(sizeof(NBDClient));
+    client->refcount = 1;
+    client->exp = exp;
+    client->sock = csock;
+    client->can_read = true;
+    client->close = close_fn;
+
+    data->client = client;
+    data->co = qemu_coroutine_create(nbd_co_client_start);
+    qemu_coroutine_enter(data->co, data);
 }