Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches

# gpg: Signature made Thu 27 Oct 2016 18:15:47 BST
# gpg:                using RSA key 0x7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (23 commits)
  iotests: Add test for NBD's blockdev-add interface
  iotests: Add assert_json_filename_equal() method
  socket_scm_helper: Accept fd directly
  iotests.py: Allow concurrent qemu instances
  iotests.py: Add qemu_nbd function
  qapi: Allow blockdev-add for NBD
  block/nbd: Use SocketAddress options
  block/nbd: Accept SocketAddress
  block/nbd: Add nbd_has_filename_options_conflict()
  block/nbd: Use qdict_put()
  block/nbd: Default port in nbd_refresh_filename()
  block/nbd: Reject port parameter without host
  block/nbd: Drop trailing "." in error messages
  qemu-iotests: Fix typo for NFS with IMGOPTSSYNTAX
  block: Remove bdrv_aio_ioctl()
  raw: Implement .bdrv_co_ioctl instead of .bdrv_aio_ioctl
  block: Introduce .bdrv_co_ioctl() driver callback
  block: Remove bdrv_ioctl()
  raw-posix: Don't use bdrv_ioctl()
  block: Use blk_co_ioctl() for all BB level ioctls
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

18 files changed, 527 insertions, 250 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index 1a724a8..c53ca30 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1099,26 +1099,36 @@ BlockAIOCB *blk_aio_pwritev(BlockBackend *blk, int64_t offset,
                         blk_aio_write_entry, flags, cb, opaque);
 }
 
+static void blk_aio_flush_entry(void *opaque)
+{
+    BlkAioEmAIOCB *acb = opaque;
+    BlkRwCo *rwco = &acb->rwco;
+
+    rwco->ret = blk_co_flush(rwco->blk);
+    blk_aio_complete(acb);
+}
+
 BlockAIOCB *blk_aio_flush(BlockBackend *blk,
                           BlockCompletionFunc *cb, void *opaque)
 {
-    if (!blk_is_available(blk)) {
-        return blk_abort_aio_request(blk, cb, opaque, -ENOMEDIUM);
-    }
+    return blk_aio_prwv(blk, 0, 0, NULL, blk_aio_flush_entry, 0, cb, opaque);
+}
+
+static void blk_aio_pdiscard_entry(void *opaque)
+{
+    BlkAioEmAIOCB *acb = opaque;
+    BlkRwCo *rwco = &acb->rwco;
 
-    return bdrv_aio_flush(blk_bs(blk), cb, opaque);
+    rwco->ret = blk_co_pdiscard(rwco->blk, rwco->offset, acb->bytes);
+    blk_aio_complete(acb);
 }
 
 BlockAIOCB *blk_aio_pdiscard(BlockBackend *blk,
                              int64_t offset, int count,
                              BlockCompletionFunc *cb, void *opaque)
 {
-    int ret = blk_check_byte_request(blk, offset, count);
-    if (ret < 0) {
-        return blk_abort_aio_request(blk, cb, opaque, ret);
-    }
-
-    return bdrv_aio_pdiscard(blk_bs(blk), offset, count, cb, opaque);
+    return blk_aio_prwv(blk, offset, count, NULL, blk_aio_pdiscard_entry, 0,
+                        cb, opaque);
 }
 
 void blk_aio_cancel(BlockAIOCB *acb)
@@ -1131,23 +1141,50 @@ void blk_aio_cancel_async(BlockAIOCB *acb)
     bdrv_aio_cancel_async(acb);
 }
 
-int blk_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
+int blk_co_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
 {
     if (!blk_is_available(blk)) {
         return -ENOMEDIUM;
     }
 
-    return bdrv_ioctl(blk_bs(blk), req, buf);
+    return bdrv_co_ioctl(blk_bs(blk), req, buf);
+}
+
+static void blk_ioctl_entry(void *opaque)
+{
+    BlkRwCo *rwco = opaque;
+    rwco->ret = blk_co_ioctl(rwco->blk, rwco->offset,
+                             rwco->qiov->iov[0].iov_base);
+}
+
+int blk_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
+{
+    return blk_prw(blk, req, buf, 0, blk_ioctl_entry, 0);
+}
+
+static void blk_aio_ioctl_entry(void *opaque)
+{
+    BlkAioEmAIOCB *acb = opaque;
+    BlkRwCo *rwco = &acb->rwco;
+
+    rwco->ret = blk_co_ioctl(rwco->blk, rwco->offset,
+                             rwco->qiov->iov[0].iov_base);
+    blk_aio_complete(acb);
 }
 
 BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
                           BlockCompletionFunc *cb, void *opaque)
 {
-    if (!blk_is_available(blk)) {
-        return blk_abort_aio_request(blk, cb, opaque, -ENOMEDIUM);
-    }
+    QEMUIOVector qiov;
+    struct iovec iov;
 
-    return bdrv_aio_ioctl(blk_bs(blk), req, buf, cb, opaque);
+    iov = (struct iovec) {
+        .iov_base = buf,
+        .iov_len = 0,
+    };
+    qemu_iovec_init_external(&qiov, &iov, 1);
+
+    return blk_aio_prwv(blk, req, 0, &qiov, blk_aio_ioctl_entry, 0, cb, opaque);
 }
 
 int blk_co_pdiscard(BlockBackend *blk, int64_t offset, int count)
@@ -1169,13 +1206,15 @@ int blk_co_flush(BlockBackend *blk)
     return bdrv_co_flush(blk_bs(blk));
 }
 
-int blk_flush(BlockBackend *blk)
+static void blk_flush_entry(void *opaque)
 {
-    if (!blk_is_available(blk)) {
-        return -ENOMEDIUM;
-    }
+    BlkRwCo *rwco = opaque;
+    rwco->ret = blk_co_flush(rwco->blk);
+}
 
-    return bdrv_flush(blk_bs(blk));
+int blk_flush(BlockBackend *blk)
+{
+    return blk_prw(blk, 0, NULL, 0, blk_flush_entry, 0);
 }
 
 void blk_drain(BlockBackend *blk)
@@ -1555,14 +1594,15 @@ int blk_truncate(BlockBackend *blk, int64_t offset)
     return bdrv_truncate(blk_bs(blk), offset);
 }
 
-int blk_pdiscard(BlockBackend *blk, int64_t offset, int count)
+static void blk_pdiscard_entry(void *opaque)
 {
-    int ret = blk_check_byte_request(blk, offset, count);
-    if (ret < 0) {
-        return ret;
-    }
+    BlkRwCo *rwco = opaque;
+    rwco->ret = blk_co_pdiscard(rwco->blk, rwco->offset, rwco->qiov->size);
+}
 
-    return bdrv_pdiscard(blk_bs(blk), offset, count);
+int blk_pdiscard(BlockBackend *blk, int64_t offset, int count)
+{
+    return blk_prw(blk, offset, NULL, count, blk_pdiscard_entry, 0);
 }
 
 int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
diff --git a/block/io.c b/block/io.c
index b136c89..79cbbdf 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2196,35 +2196,6 @@ BlockAIOCB *bdrv_aio_flush(BlockDriverState *bs,
     return &acb->common;
 }
 
-static void coroutine_fn bdrv_aio_pdiscard_co_entry(void *opaque)
-{
-    BlockAIOCBCoroutine *acb = opaque;
-    BlockDriverState *bs = acb->common.bs;
-
-    acb->req.error = bdrv_co_pdiscard(bs, acb->req.offset, acb->req.bytes);
-    bdrv_co_complete(acb);
-}
-
-BlockAIOCB *bdrv_aio_pdiscard(BlockDriverState *bs, int64_t offset, int count,
-                              BlockCompletionFunc *cb, void *opaque)
-{
-    Coroutine *co;
-    BlockAIOCBCoroutine *acb;
-
-    trace_bdrv_aio_pdiscard(bs, offset, count, opaque);
-
-    acb = qemu_aio_get(&bdrv_em_co_aiocb_info, bs, cb, opaque);
-    acb->need_bh = true;
-    acb->req.error = -EINPROGRESS;
-    acb->req.offset = offset;
-    acb->req.bytes = count;
-    co = qemu_coroutine_create(bdrv_aio_pdiscard_co_entry, acb);
-    qemu_coroutine_enter(co);
-
-    bdrv_co_maybe_schedule_bh(acb);
-    return &acb->common;
-}
-
 void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs,
                    BlockCompletionFunc *cb, void *opaque)
 {
@@ -2521,7 +2492,7 @@ int bdrv_pdiscard(BlockDriverState *bs, int64_t offset, int count)
     return rwco.ret;
 }
 
-static int bdrv_co_do_ioctl(BlockDriverState *bs, int req, void *buf)
+int bdrv_co_ioctl(BlockDriverState *bs, int req, void *buf)
 {
     BlockDriver *drv = bs->drv;
     BdrvTrackedRequest tracked_req;
@@ -2531,86 +2502,26 @@ static int bdrv_co_do_ioctl(BlockDriverState *bs, int req, void *buf)
     BlockAIOCB *acb;
 
     tracked_request_begin(&tracked_req, bs, 0, 0, BDRV_TRACKED_IOCTL);
-    if (!drv || !drv->bdrv_aio_ioctl) {
+    if (!drv || (!drv->bdrv_aio_ioctl && !drv->bdrv_co_ioctl)) {
         co.ret = -ENOTSUP;
         goto out;
     }
 
-    acb = drv->bdrv_aio_ioctl(bs, req, buf, bdrv_co_io_em_complete, &co);
-    if (!acb) {
-        co.ret = -ENOTSUP;
-        goto out;
+    if (drv->bdrv_co_ioctl) {
+        co.ret = drv->bdrv_co_ioctl(bs, req, buf);
+    } else {
+        acb = drv->bdrv_aio_ioctl(bs, req, buf, bdrv_co_io_em_complete, &co);
+        if (!acb) {
+            co.ret = -ENOTSUP;
+            goto out;
+        }
+        qemu_coroutine_yield();
     }
-    qemu_coroutine_yield();
 out:
     tracked_request_end(&tracked_req);
     return co.ret;
 }
 
-typedef struct {
-    BlockDriverState *bs;
-    int req;
-    void *buf;
-    int ret;
-} BdrvIoctlCoData;
-
-static void coroutine_fn bdrv_co_ioctl_entry(void *opaque)
-{
-    BdrvIoctlCoData *data = opaque;
-    data->ret = bdrv_co_do_ioctl(data->bs, data->req, data->buf);
-}
-
-/* needed for generic scsi interface */
-int bdrv_ioctl(BlockDriverState *bs, unsigned long int req, void *buf)
-{
-    BdrvIoctlCoData data = {
-        .bs = bs,
-        .req = req,
-        .buf = buf,
-        .ret = -EINPROGRESS,
-    };
-
-    if (qemu_in_coroutine()) {
-        /* Fast-path if already in coroutine context */
-        bdrv_co_ioctl_entry(&data);
-    } else {
-        Coroutine *co = qemu_coroutine_create(bdrv_co_ioctl_entry, &data);
-
-        qemu_coroutine_enter(co);
-        while (data.ret == -EINPROGRESS) {
-            aio_poll(bdrv_get_aio_context(bs), true);
-        }
-    }
-    return data.ret;
-}
-
-static void coroutine_fn bdrv_co_aio_ioctl_entry(void *opaque)
-{
-    BlockAIOCBCoroutine *acb = opaque;
-    acb->req.error = bdrv_co_do_ioctl(acb->common.bs,
-                                      acb->req.req, acb->req.buf);
-    bdrv_co_complete(acb);
-}
-
-BlockAIOCB *bdrv_aio_ioctl(BlockDriverState *bs,
-        unsigned long int req, void *buf,
-        BlockCompletionFunc *cb, void *opaque)
-{
-    BlockAIOCBCoroutine *acb = qemu_aio_get(&bdrv_em_co_aiocb_info,
-                                            bs, cb, opaque);
-    Coroutine *co;
-
-    acb->need_bh = true;
-    acb->req.error = -EINPROGRESS;
-    acb->req.req = req;
-    acb->req.buf = buf;
-    co = qemu_coroutine_create(bdrv_co_aio_ioctl_entry, acb);
-    qemu_coroutine_enter(co);
-
-    bdrv_co_maybe_schedule_bh(acb);
-    return &acb->common;
-}
-
 void *qemu_blockalign(BlockDriverState *bs, size_t size)
 {
     return qemu_memalign(bdrv_opt_mem_align(bs), size);
diff --git a/block/nbd.c b/block/nbd.c
index 6bc06d6..8ef1438 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -32,6 +32,9 @@
 #include "qemu/uri.h"
 #include "block/block_int.h"
 #include "qemu/module.h"
+#include "qapi-visit.h"
+#include "qapi/qobject-input-visitor.h"
+#include "qapi/qobject-output-visitor.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/qmp/qjson.h"
 #include "qapi/qmp/qint.h"
@@ -44,7 +47,8 @@ typedef struct BDRVNBDState {
     NbdClientSession client;
 
     /* For nbd_refresh_filename() */
-    char *path, *host, *port, *export, *tlscredsid;
+    SocketAddress *saddr;
+    char *export, *tlscredsid;
 } BDRVNBDState;
 
 static int nbd_parse_uri(const char *filename, QDict *options)
@@ -90,9 +94,13 @@ static int nbd_parse_uri(const char *filename, QDict *options)
             ret = -EINVAL;
             goto out;
         }
-        qdict_put(options, "path", qstring_from_str(qp->p[0].value));
+        qdict_put(options, "server.type", qstring_from_str("unix"));
+        qdict_put(options, "server.data.path",
+                  qstring_from_str(qp->p[0].value));
     } else {
         QString *host;
+        char *port_str;
+
         /* nbd[+tcp]://host[:port]/export */
         if (!uri->server) {
             ret = -EINVAL;
@@ -107,12 +115,12 @@ static int nbd_parse_uri(const char *filename, QDict *options)
             host = qstring_from_str(uri->server);
         }
 
-        qdict_put(options, "host", host);
-        if (uri->port) {
-            char* port_str = g_strdup_printf("%d", uri->port);
-            qdict_put(options, "port", qstring_from_str(port_str));
-            g_free(port_str);
-        }
+        qdict_put(options, "server.type", qstring_from_str("inet"));
+        qdict_put(options, "server.data.host", host);
+
+        port_str = g_strdup_printf("%d", uri->port ?: NBD_DEFAULT_PORT);
+        qdict_put(options, "server.data.port", qstring_from_str(port_str));
+        g_free(port_str);
     }
 
 out:
@@ -123,6 +131,26 @@ out:
     return ret;
 }
 
+static bool nbd_has_filename_options_conflict(QDict *options, Error **errp)
+{
+    const QDictEntry *e;
+
+    for (e = qdict_first(options); e; e = qdict_next(options, e)) {
+        if (!strcmp(e->key, "host") ||
+            !strcmp(e->key, "port") ||
+            !strcmp(e->key, "path") ||
+            !strcmp(e->key, "export") ||
+            strstart(e->key, "server.", NULL))
+        {
+            error_setg(errp, "Option '%s' cannot be used with a file name",
+                       e->key);
+            return true;
+        }
+    }
+
+    return false;
+}
+
 static void nbd_parse_filename(const char *filename, QDict *options,
                                Error **errp)
 {
@@ -131,12 +159,7 @@ static void nbd_parse_filename(const char *filename, QDict *options,
     const char *host_spec;
     const char *unixpath;
 
-    if (qdict_haskey(options, "host")
-        || qdict_haskey(options, "port")
-        || qdict_haskey(options, "path"))
-    {
-        error_setg(errp, "host/port/path and a file name may not be specified "
-                         "at the same time");
+    if (nbd_has_filename_options_conflict(options, errp)) {
         return;
     }
 
@@ -173,7 +196,8 @@ static void nbd_parse_filename(const char *filename, QDict *options,
 
     /* are we a UNIX or TCP socket? */
     if (strstart(host_spec, "unix:", &unixpath)) {
-        qdict_put(options, "path", qstring_from_str(unixpath));
+        qdict_put(options, "server.type", qstring_from_str("unix"));
+        qdict_put(options, "server.data.path", qstring_from_str(unixpath));
     } else {
         InetSocketAddress *addr = NULL;
 
@@ -182,8 +206,9 @@ static void nbd_parse_filename(const char *filename, QDict *options,
             goto out;
         }
 
-        qdict_put(options, "host", qstring_from_str(addr->host));
-        qdict_put(options, "port", qstring_from_str(addr->port));
+        qdict_put(options, "server.type", qstring_from_str("inet"));
+        qdict_put(options, "server.data.host", qstring_from_str(addr->host));
+        qdict_put(options, "server.data.port", qstring_from_str(addr->port));
         qapi_free_InetSocketAddress(addr);
     }
 
@@ -191,47 +216,81 @@ out:
     g_free(file);
 }
 
-static SocketAddress *nbd_config(BDRVNBDState *s, QemuOpts *opts, Error **errp)
+static bool nbd_process_legacy_socket_options(QDict *output_options,
+                                              QemuOpts *legacy_opts,
+                                              Error **errp)
 {
-    SocketAddress *saddr;
+    const char *path = qemu_opt_get(legacy_opts, "path");
+    const char *host = qemu_opt_get(legacy_opts, "host");
+    const char *port = qemu_opt_get(legacy_opts, "port");
+    const QDictEntry *e;
 
-    s->path = g_strdup(qemu_opt_get(opts, "path"));
-    s->host = g_strdup(qemu_opt_get(opts, "host"));
+    if (!path && !host && !port) {
+        return true;
+    }
 
-    if (!s->path == !s->host) {
-        if (s->path) {
-            error_setg(errp, "path and host may not be used at the same time.");
-        } else {
-            error_setg(errp, "one of path and host must be specified.");
+    for (e = qdict_first(output_options); e; e = qdict_next(output_options, e))
+    {
+        if (strstart(e->key, "server.", NULL)) {
+            error_setg(errp, "Cannot use 'server' and path/host/port at the "
+                       "same time");
+            return false;
         }
-        return NULL;
     }
 
-    saddr = g_new0(SocketAddress, 1);
+    if (path && host) {
+        error_setg(errp, "path and host may not be used at the same time");
+        return false;
+    } else if (path) {
+        if (port) {
+            error_setg(errp, "port may not be used without host");
+            return false;
+        }
 
-    if (s->path) {
-        UnixSocketAddress *q_unix;
-        saddr->type = SOCKET_ADDRESS_KIND_UNIX;
-        q_unix = saddr->u.q_unix.data = g_new0(UnixSocketAddress, 1);
-        q_unix->path = g_strdup(s->path);
-    } else {
-        InetSocketAddress *inet;
+        qdict_put(output_options, "server.type", qstring_from_str("unix"));
+        qdict_put(output_options, "server.data.path", qstring_from_str(path));
+    } else if (host) {
+        qdict_put(output_options, "server.type", qstring_from_str("inet"));
+        qdict_put(output_options, "server.data.host", qstring_from_str(host));
+        qdict_put(output_options, "server.data.port",
+                  qstring_from_str(port ?: stringify(NBD_DEFAULT_PORT)));
+    }
 
-        s->port = g_strdup(qemu_opt_get(opts, "port"));
+    return true;
+}
 
-        saddr->type = SOCKET_ADDRESS_KIND_INET;
-        inet = saddr->u.inet.data = g_new0(InetSocketAddress, 1);
-        inet->host = g_strdup(s->host);
-        inet->port = g_strdup(s->port);
-        if (!inet->port) {
-            inet->port = g_strdup_printf("%d", NBD_DEFAULT_PORT);
-        }
+static SocketAddress *nbd_config(BDRVNBDState *s, QDict *options, Error **errp)
+{
+    SocketAddress *saddr = NULL;
+    QDict *addr = NULL;
+    QObject *crumpled_addr = NULL;
+    Visitor *iv = NULL;
+    Error *local_err = NULL;
+
+    qdict_extract_subqdict(options, &addr, "server.");
+    if (!qdict_size(addr)) {
+        error_setg(errp, "NBD server address missing");
+        goto done;
     }
 
-    s->client.is_unix = saddr->type == SOCKET_ADDRESS_KIND_UNIX;
+    crumpled_addr = qdict_crumple(addr, errp);
+    if (!crumpled_addr) {
+        goto done;
+    }
 
-    s->export = g_strdup(qemu_opt_get(opts, "export"));
+    iv = qobject_input_visitor_new(crumpled_addr, true);
+    visit_type_SocketAddress(iv, NULL, &saddr, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto done;
+    }
+
+    s->client.is_unix = saddr->type == SOCKET_ADDRESS_KIND_UNIX;
 
+done:
+    QDECREF(addr);
+    qobject_decref(crumpled_addr);
+    visit_free(iv);
     return saddr;
 }
 
@@ -332,7 +391,6 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     QemuOpts *opts = NULL;
     Error *local_err = NULL;
     QIOChannelSocket *sioc = NULL;
-    SocketAddress *saddr = NULL;
     QCryptoTLSCreds *tlscreds = NULL;
     const char *hostname = NULL;
     int ret = -EINVAL;
@@ -344,12 +402,19 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
         goto error;
     }
 
+    /* Translate @host, @port, and @path to a SocketAddress */
+    if (!nbd_process_legacy_socket_options(options, opts, errp)) {
+        goto error;
+    }
+
     /* Pop the config into our state object. Exit if invalid. */
-    saddr = nbd_config(s, opts, errp);
-    if (!saddr) {
+    s->saddr = nbd_config(s, options, errp);
+    if (!s->saddr) {
         goto error;
     }
 
+    s->export = g_strdup(qemu_opt_get(opts, "export"));
+
     s->tlscredsid = g_strdup(qemu_opt_get(opts, "tls-creds"));
     if (s->tlscredsid) {
         tlscreds = nbd_get_tls_creds(s->tlscredsid, errp);
@@ -357,17 +422,17 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
             goto error;
         }
 
-        if (saddr->type != SOCKET_ADDRESS_KIND_INET) {
+        if (s->saddr->type != SOCKET_ADDRESS_KIND_INET) {
             error_setg(errp, "TLS only supported over IP sockets");
             goto error;
         }
-        hostname = saddr->u.inet.data->host;
+        hostname = s->saddr->u.inet.data->host;
     }
 
     /* establish TCP connection, return error if it fails
      * TODO: Configurable retry-until-timeout behaviour.
      */
-    sioc = nbd_establish_connection(saddr, errp);
+    sioc = nbd_establish_connection(s->saddr, errp);
     if (!sioc) {
         ret = -ECONNREFUSED;
         goto error;
@@ -384,13 +449,10 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
         object_unref(OBJECT(tlscreds));
     }
     if (ret < 0) {
-        g_free(s->path);
-        g_free(s->host);
-        g_free(s->port);
+        qapi_free_SocketAddress(s->saddr);
         g_free(s->export);
         g_free(s->tlscredsid);
     }
-    qapi_free_SocketAddress(saddr);
     qemu_opts_del(opts);
     return ret;
 }
@@ -412,9 +474,7 @@ static void nbd_close(BlockDriverState *bs)
 
     nbd_client_close(bs);
 
-    g_free(s->path);
-    g_free(s->host);
-    g_free(s->port);
+    qapi_free_SocketAddress(s->saddr);
     g_free(s->export);
     g_free(s->tlscredsid);
 }
@@ -441,45 +501,51 @@ static void nbd_refresh_filename(BlockDriverState *bs, QDict *options)
 {
     BDRVNBDState *s = bs->opaque;
     QDict *opts = qdict_new();
+    QObject *saddr_qdict;
+    Visitor *ov;
+    const char *host = NULL, *port = NULL, *path = NULL;
+
+    if (s->saddr->type == SOCKET_ADDRESS_KIND_INET) {
+        const InetSocketAddress *inet = s->saddr->u.inet.data;
+        if (!inet->has_ipv4 && !inet->has_ipv6 && !inet->has_to) {
+            host = inet->host;
+            port = inet->port;
+        }
+    } else if (s->saddr->type == SOCKET_ADDRESS_KIND_UNIX) {
+        path = s->saddr->u.q_unix.data->path;
+    }
 
-    qdict_put_obj(opts, "driver", QOBJECT(qstring_from_str("nbd")));
+    qdict_put(opts, "driver", qstring_from_str("nbd"));
 
-    if (s->path && s->export) {
+    if (path && s->export) {
         snprintf(bs->exact_filename, sizeof(bs->exact_filename),
-                 "nbd+unix:///%s?socket=%s", s->export, s->path);
-    } else if (s->path && !s->export) {
+                 "nbd+unix:///%s?socket=%s", s->export, path);
+    } else if (path && !s->export) {
         snprintf(bs->exact_filename, sizeof(bs->exact_filename),
-                 "nbd+unix://?socket=%s", s->path);
-    } else if (!s->path && s->export && s->port) {
+                 "nbd+unix://?socket=%s", path);
+    } else if (host && s->export) {
         snprintf(bs->exact_filename, sizeof(bs->exact_filename),
-                 "nbd://%s:%s/%s", s->host, s->port, s->export);
-    } else if (!s->path && s->export && !s->port) {
+                 "nbd://%s:%s/%s", host, port, s->export);
+    } else if (host && !s->export) {
         snprintf(bs->exact_filename, sizeof(bs->exact_filename),
-                 "nbd://%s/%s", s->host, s->export);
-    } else if (!s->path && !s->export && s->port) {
-        snprintf(bs->exact_filename, sizeof(bs->exact_filename),
-                 "nbd://%s:%s", s->host, s->port);
-    } else if (!s->path && !s->export && !s->port) {
-        snprintf(bs->exact_filename, sizeof(bs->exact_filename),
-                 "nbd://%s", s->host);
+                 "nbd://%s:%s", host, port);
     }
 
-    if (s->path) {
-        qdict_put_obj(opts, "path", QOBJECT(qstring_from_str(s->path)));
-    } else if (s->port) {
-        qdict_put_obj(opts, "host", QOBJECT(qstring_from_str(s->host)));
-        qdict_put_obj(opts, "port", QOBJECT(qstring_from_str(s->port)));
-    } else {
-        qdict_put_obj(opts, "host", QOBJECT(qstring_from_str(s->host)));
-    }
+    ov = qobject_output_visitor_new(&saddr_qdict);
+    visit_type_SocketAddress(ov, NULL, &s->saddr, &error_abort);
+    visit_complete(ov, &saddr_qdict);
+    assert(qobject_type(saddr_qdict) == QTYPE_QDICT);
+
+    qdict_put_obj(opts, "server", saddr_qdict);
+
     if (s->export) {
-        qdict_put_obj(opts, "export", QOBJECT(qstring_from_str(s->export)));
+        qdict_put(opts, "export", qstring_from_str(s->export));
     }
     if (s->tlscredsid) {
-        qdict_put_obj(opts, "tls-creds",
-                      QOBJECT(qstring_from_str(s->tlscredsid)));
+        qdict_put(opts, "tls-creds", qstring_from_str(s->tlscredsid));
     }
 
+    qdict_flatten(opts);
     bs->full_open_options = opts;
 }
 
diff --git a/block/raw-posix.c b/block/raw-posix.c
index f481e57..247e47b 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -2069,13 +2069,23 @@ static bool hdev_is_sg(BlockDriverState *bs)
 
 #if defined(__linux__)
 
+    BDRVRawState *s = bs->opaque;
     struct stat st;
     struct sg_scsi_id scsiid;
     int sg_version;
+    int ret;
+
+    if (stat(bs->filename, &st) < 0 || !S_ISCHR(st.st_mode)) {
+        return false;
+    }
 
-    if (stat(bs->filename, &st) >= 0 && S_ISCHR(st.st_mode) &&
-        !bdrv_ioctl(bs, SG_GET_VERSION_NUM, &sg_version) &&
-        !bdrv_ioctl(bs, SG_GET_SCSI_ID, &scsiid)) {
+    ret = ioctl(s->fd, SG_GET_VERSION_NUM, &sg_version);
+    if (ret < 0) {
+        return false;
+    }
+
+    ret = ioctl(s->fd, SG_GET_SCSI_ID, &scsiid);
+    if (ret >= 0) {
         DPRINTF("SG device found: type=%d, version=%d\n",
             scsiid.scsi_type, sg_version);
         return true;
diff --git a/block/raw_bsd.c b/block/raw_bsd.c
index 588d408..fc16ec1 100644
--- a/block/raw_bsd.c
+++ b/block/raw_bsd.c
@@ -176,12 +176,9 @@ static void raw_lock_medium(BlockDriverState *bs, bool locked)
     bdrv_lock_medium(bs->file->bs, locked);
 }
 
-static BlockAIOCB *raw_aio_ioctl(BlockDriverState *bs,
-                                 unsigned long int req, void *buf,
-                                 BlockCompletionFunc *cb,
-                                 void *opaque)
+static int raw_co_ioctl(BlockDriverState *bs, unsigned long int req, void *buf)
 {
-    return bdrv_aio_ioctl(bs->file->bs, req, buf, cb, opaque);
+    return bdrv_co_ioctl(bs->file->bs, req, buf);
 }
 
 static int raw_has_zero_init(BlockDriverState *bs)
@@ -261,7 +258,7 @@ BlockDriver bdrv_raw = {
     .bdrv_media_changed   = &raw_media_changed,
     .bdrv_eject           = &raw_eject,
     .bdrv_lock_medium     = &raw_lock_medium,
-    .bdrv_aio_ioctl       = &raw_aio_ioctl,
+    .bdrv_co_ioctl        = &raw_co_ioctl,
     .create_opts          = &raw_create_opts,
     .bdrv_has_zero_init   = &raw_has_zero_init
 };
diff --git a/block/trace-events b/block/trace-events
index 05fa13c..aff8a96 100644
--- a/block/trace-events
+++ b/block/trace-events
@@ -9,7 +9,6 @@ blk_co_preadv(void *blk, void *bs, int64_t offset, unsigned int bytes, int flags
 blk_co_pwritev(void *blk, void *bs, int64_t offset, unsigned int bytes, int flags) "blk %p bs %p offset %"PRId64" bytes %u flags %x"
 
 # block/io.c
-bdrv_aio_pdiscard(void *bs, int64_t offset, int count, void *opaque) "bs %p offset %"PRId64" count %d opaque %p"
 bdrv_aio_flush(void *bs, void *opaque) "bs %p opaque %p"
 bdrv_aio_readv(void *bs, int64_t sector_num, int nb_sectors, void *opaque) "bs %p sector_num %"PRId64" nb_sectors %d opaque %p"
 bdrv_aio_writev(void *bs, int64_t sector_num, int nb_sectors, void *opaque) "bs %p sector_num %"PRId64" nb_sectors %d opaque %p"
diff --git a/include/block/block.h b/include/block/block.h
index 107c603..398a050 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -314,17 +314,11 @@ BlockAIOCB *bdrv_aio_writev(BdrvChild *child, int64_t sector_num,
                             BlockCompletionFunc *cb, void *opaque);
 BlockAIOCB *bdrv_aio_flush(BlockDriverState *bs,
                            BlockCompletionFunc *cb, void *opaque);
-BlockAIOCB *bdrv_aio_pdiscard(BlockDriverState *bs,
-                              int64_t offset, int count,
-                              BlockCompletionFunc *cb, void *opaque);
 void bdrv_aio_cancel(BlockAIOCB *acb);
 void bdrv_aio_cancel_async(BlockAIOCB *acb);
 
 /* sg packet commands */
-int bdrv_ioctl(BlockDriverState *bs, unsigned long int req, void *buf);
-BlockAIOCB *bdrv_aio_ioctl(BlockDriverState *bs,
-        unsigned long int req, void *buf,
-        BlockCompletionFunc *cb, void *opaque);
+int bdrv_co_ioctl(BlockDriverState *bs, int req, void *buf);
 
 /* Invalidate any cached metadata used by image formats */
 void bdrv_invalidate_cache(BlockDriverState *bs, Error **errp);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 3e79228..e96e9ad 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -244,6 +244,8 @@ struct BlockDriver {
     BlockAIOCB *(*bdrv_aio_ioctl)(BlockDriverState *bs,
         unsigned long int req, void *buf,
         BlockCompletionFunc *cb, void *opaque);
+    int coroutine_fn (*bdrv_co_ioctl)(BlockDriverState *bs,
+                                      unsigned long int req, void *buf);
 
     /* List of options for creating images, terminated by name == NULL */
     QemuOptsList *create_opts;
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index b07159b..6444e41 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -146,6 +146,7 @@ BlockAIOCB *blk_aio_pdiscard(BlockBackend *blk, int64_t offset, int count,
                              BlockCompletionFunc *cb, void *opaque);
 void blk_aio_cancel(BlockAIOCB *acb);
 void blk_aio_cancel_async(BlockAIOCB *acb);
+int blk_co_ioctl(BlockBackend *blk, unsigned long int req, void *buf);
 int blk_ioctl(BlockBackend *blk, unsigned long int req, void *buf);
 BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
                           BlockCompletionFunc *cb, void *opaque);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 97b1205..cd1fa7b 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1703,15 +1703,16 @@
 #
 # @host_device, @host_cdrom: Since 2.1
 # @gluster: Since 2.7
+# @nbd: Since 2.8
 #
 # Since: 2.0
 ##
 { 'enum': 'BlockdevDriver',
   'data': [ 'archipelago', 'blkdebug', 'blkverify', 'bochs', 'cloop',
             'dmg', 'file', 'ftp', 'ftps', 'gluster', 'host_cdrom',
-            'host_device', 'http', 'https', 'luks', 'null-aio', 'null-co',
-            'parallels', 'qcow', 'qcow2', 'qed', 'quorum', 'raw',
-	    'replication', 'tftp', 'vdi', 'vhdx', 'vmdk', 'vpc', 'vvfat' ] }
+            'host_device', 'http', 'https', 'luks', 'nbd', 'null-aio',
+            'null-co', 'parallels', 'qcow', 'qcow2', 'qed', 'quorum', 'raw',
+            'replication', 'tftp', 'vdi', 'vhdx', 'vmdk', 'vpc', 'vvfat' ] }
 
 ##
 # @BlockdevOptionsFile
@@ -2220,6 +2221,24 @@
   'data': { 'filename': 'str' } }
 
 ##
+# @BlockdevOptionsNbd
+#
+# Driver specific block device options for NBD.
+#
+# @server:      NBD server address
+#
+# @export:      #optional export name
+#
+# @tls-creds:   #optional TLS credentials ID
+#
+# Since: 2.8
+##
+{ 'struct': 'BlockdevOptionsNbd',
+  'data': { 'server': 'SocketAddress',
+            '*export': 'str',
+            '*tls-creds': 'str' } }
+
+##
 # @BlockdevOptions
 #
 # Options for creating a block device.  Many options are available for all
@@ -2264,7 +2283,7 @@
       'https':      'BlockdevOptionsCurl',
 # TODO iscsi: Wait for structured options
       'luks':       'BlockdevOptionsLUKS',
-# TODO nbd: Should take InetSocketAddress for 'host'?
+      'nbd':        'BlockdevOptionsNbd',
 # TODO nfs: Wait for structured options
       'null-aio':   'BlockdevOptionsNull',
       'null-co':    'BlockdevOptionsNull',
diff --git a/tests/qemu-iotests/051.out b/tests/qemu-iotests/051.out
index 408d613..42bf416 100644
--- a/tests/qemu-iotests/051.out
+++ b/tests/qemu-iotests/051.out
@@ -222,7 +222,7 @@ Testing: -drive driver=file
 QEMU_PROG: -drive driver=file: The 'file' block driver requires a file name
 
 Testing: -drive driver=nbd
-QEMU_PROG: -drive driver=nbd: one of path and host must be specified.
+QEMU_PROG: -drive driver=nbd: NBD server address missing
 
 Testing: -drive driver=raw
 QEMU_PROG: -drive driver=raw: Can't use 'raw' as a block driver for the protocol level
@@ -231,7 +231,7 @@ Testing: -drive file.driver=file
 QEMU_PROG: -drive file.driver=file: The 'file' block driver requires a file name
 
 Testing: -drive file.driver=nbd
-QEMU_PROG: -drive file.driver=nbd: one of path and host must be specified.
+QEMU_PROG: -drive file.driver=nbd: NBD server address missing
 
 Testing: -drive file.driver=raw
 QEMU_PROG: -drive file.driver=raw: Can't use 'raw' as a block driver for the protocol level
diff --git a/tests/qemu-iotests/051.pc.out b/tests/qemu-iotests/051.pc.out
index ec6d222..603bb76 100644
--- a/tests/qemu-iotests/051.pc.out
+++ b/tests/qemu-iotests/051.pc.out
@@ -316,7 +316,7 @@ Testing: -drive driver=file
 QEMU_PROG: -drive driver=file: The 'file' block driver requires a file name
 
 Testing: -drive driver=nbd
-QEMU_PROG: -drive driver=nbd: one of path and host must be specified.
+QEMU_PROG: -drive driver=nbd: NBD server address missing
 
 Testing: -drive driver=raw
 QEMU_PROG: -drive driver=raw: Can't use 'raw' as a block driver for the protocol level
@@ -325,7 +325,7 @@ Testing: -drive file.driver=file
 QEMU_PROG: -drive file.driver=file: The 'file' block driver requires a file name
 
 Testing: -drive file.driver=nbd
-QEMU_PROG: -drive file.driver=nbd: one of path and host must be specified.
+QEMU_PROG: -drive file.driver=nbd: NBD server address missing
 
 Testing: -drive file.driver=raw
 QEMU_PROG: -drive file.driver=raw: Can't use 'raw' as a block driver for the protocol level
diff --git a/tests/qemu-iotests/147 b/tests/qemu-iotests/147
new file mode 100755
index 0000000..45469c9
--- /dev/null
+++ b/tests/qemu-iotests/147
@@ -0,0 +1,195 @@
+#!/usr/bin/env python
+#
+# Test case for NBD's blockdev-add interface
+#
+# Copyright (C) 2016 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import os
+import socket
+import stat
+import time
+import iotests
+from iotests import cachemode, imgfmt, qemu_img, qemu_nbd
+
+NBD_PORT = 10811
+
+test_img = os.path.join(iotests.test_dir, 'test.img')
+unix_socket = os.path.join(iotests.test_dir, 'nbd.socket')
+
+class NBDBlockdevAddBase(iotests.QMPTestCase):
+    def blockdev_add_options(self, address, export=None):
+        options = { 'node-name': 'nbd-blockdev',
+                    'driver': 'raw',
+                    'file': {
+                        'driver': 'nbd',
+                        'server': address
+                    } }
+        if export is not None:
+            options['file']['export'] = export
+        return options
+
+    def client_test(self, filename, address, export=None):
+        bao = self.blockdev_add_options(address, export)
+        result = self.vm.qmp('blockdev-add', **bao)
+        self.assert_qmp(result, 'return', {})
+
+        result = self.vm.qmp('query-named-block-nodes')
+        for node in result['return']:
+            if node['node-name'] == 'nbd-blockdev':
+                if isinstance(filename, str):
+                    self.assert_qmp(node, 'image/filename', filename)
+                else:
+                    self.assert_json_filename_equal(node['image']['filename'],
+                                                    filename)
+                break
+
+        result = self.vm.qmp('x-blockdev-del', node_name='nbd-blockdev')
+        self.assert_qmp(result, 'return', {})
+
+
+class QemuNBD(NBDBlockdevAddBase):
+    def setUp(self):
+        qemu_img('create', '-f', iotests.imgfmt, test_img, '64k')
+        self.vm = iotests.VM()
+        self.vm.launch()
+
+    def tearDown(self):
+        self.vm.shutdown()
+        os.remove(test_img)
+        try:
+            os.remove(unix_socket)
+        except OSError:
+            pass
+
+    def _server_up(self, *args):
+        self.assertEqual(qemu_nbd('-f', imgfmt, test_img, *args), 0)
+
+    def test_inet(self):
+        self._server_up('-p', str(NBD_PORT))
+        address = { 'type': 'inet',
+                    'data': {
+                        'host': 'localhost',
+                        'port': str(NBD_PORT)
+                    } }
+        self.client_test('nbd://localhost:%i' % NBD_PORT, address)
+
+    def test_unix(self):
+        self._server_up('-k', unix_socket)
+        address = { 'type': 'unix',
+                    'data': { 'path': unix_socket } }
+        self.client_test('nbd+unix://?socket=' + unix_socket, address)
+
+
+class BuiltinNBD(NBDBlockdevAddBase):
+    def setUp(self):
+        qemu_img('create', '-f', iotests.imgfmt, test_img, '64k')
+        self.vm = iotests.VM()
+        self.vm.launch()
+        self.server = iotests.VM('.server')
+        self.server.add_drive_raw('if=none,id=nbd-export,' +
+                                  'file=%s,' % test_img +
+                                  'format=%s,' % imgfmt +
+                                  'cache=%s' % cachemode)
+        self.server.launch()
+
+    def tearDown(self):
+        self.vm.shutdown()
+        self.server.shutdown()
+        os.remove(test_img)
+        try:
+            os.remove(unix_socket)
+        except OSError:
+            pass
+
+    def _server_up(self, address):
+        result = self.server.qmp('nbd-server-start', addr=address)
+        self.assert_qmp(result, 'return', {})
+
+        result = self.server.qmp('nbd-server-add', device='nbd-export')
+        self.assert_qmp(result, 'return', {})
+
+    def _server_down(self):
+        result = self.server.qmp('nbd-server-stop')
+        self.assert_qmp(result, 'return', {})
+
+    def test_inet(self):
+        address = { 'type': 'inet',
+                    'data': {
+                        'host': 'localhost',
+                        'port': str(NBD_PORT)
+                    } }
+        self._server_up(address)
+        self.client_test('nbd://localhost:%i/nbd-export' % NBD_PORT,
+                         address, 'nbd-export')
+        self._server_down()
+
+    def test_inet6(self):
+        address = { 'type': 'inet',
+                    'data': {
+                        'host': '::1',
+                        'port': str(NBD_PORT),
+                        'ipv4': False,
+                        'ipv6': True
+                    } }
+        filename = { 'driver': 'raw',
+                     'file': {
+                         'driver': 'nbd',
+                         'export': 'nbd-export',
+                         'server': address
+                     } }
+        self._server_up(address)
+        self.client_test(filename, address, 'nbd-export')
+        self._server_down()
+
+    def test_unix(self):
+        address = { 'type': 'unix',
+                    'data': { 'path': unix_socket } }
+        self._server_up(address)
+        self.client_test('nbd+unix:///nbd-export?socket=' + unix_socket,
+                         address, 'nbd-export')
+        self._server_down()
+
+    def test_fd(self):
+        self._server_up({ 'type': 'unix',
+                          'data': { 'path': unix_socket } })
+
+        sockfd = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        sockfd.connect(unix_socket)
+
+        result = self.vm.send_fd_scm(str(sockfd.fileno()))
+        self.assertEqual(result, 0, 'Failed to send socket FD')
+
+        result = self.vm.qmp('getfd', fdname='nbd-fifo')
+        self.assert_qmp(result, 'return', {})
+
+        address = { 'type': 'fd',
+                    'data': { 'str': 'nbd-fifo' } }
+        filename = { 'driver': 'raw',
+                     'file': {
+                         'driver': 'nbd',
+                         'export': 'nbd-export',
+                         'server': address
+                     } }
+        self.client_test(filename, address, 'nbd-export')
+
+        self._server_down()
+
+
+if __name__ == '__main__':
+    # Need to support image creation
+    iotests.main(supported_fmts=['vpc', 'parallels', 'qcow', 'vdi', 'qcow2',
+                                 'vmdk', 'raw', 'vhdx', 'qed'])
diff --git a/tests/qemu-iotests/147.out b/tests/qemu-iotests/147.out
new file mode 100644
index 0000000..3f8a935
--- /dev/null
+++ b/tests/qemu-iotests/147.out
@@ -0,0 +1,5 @@
+......
+----------------------------------------------------------------------
+Ran 6 tests
+
+OK
diff --git a/tests/qemu-iotests/common.rc b/tests/qemu-iotests/common.rc
index 126bd67..3213765 100644
--- a/tests/qemu-iotests/common.rc
+++ b/tests/qemu-iotests/common.rc
@@ -69,7 +69,7 @@ if [ "$IMGOPTSSYNTAX" = "true" ]; then
         TEST_IMG="$DRIVER,file.driver=ssh,file.host=127.0.0.1,file.path=$TEST_IMG_FILE"
     elif [ "$IMGPROTO" = "nfs" ]; then
         TEST_DIR="$DRIVER,file.driver=nfs,file.filename=nfs://127.0.0.1/$TEST_DIR"
-        TEST_IMG=$TEST_DIR_OPTS/t.$IMGFMT
+        TEST_IMG=$TEST_DIR/t.$IMGFMT
     elif [ "$IMGPROTO" = "archipelago" ]; then
         TEST_IMG="$DRIVER,file.driver=archipelago,file.volume=:at.$IMGFMT"
     else
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 7eb1770..d7d50cf 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -149,6 +149,7 @@
 144 rw auto quick
 145 auto quick
 146 auto quick
+147 auto
 148 rw auto quick
 149 rw auto sudo
 150 rw auto quick
diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 3329bc1..1f30cfc 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -39,6 +39,10 @@ qemu_io_args = [os.environ.get('QEMU_IO_PROG', 'qemu-io')]
 if os.environ.get('QEMU_IO_OPTIONS'):
     qemu_io_args += os.environ['QEMU_IO_OPTIONS'].strip().split(' ')
 
+qemu_nbd_args = [os.environ.get('QEMU_NBD_PROG', 'qemu-nbd')]
+if os.environ.get('QEMU_NBD_OPTIONS'):
+    qemu_nbd_args += os.environ['QEMU_NBD_OPTIONS'].strip().split(' ')
+
 qemu_prog = os.environ.get('QEMU_PROG', 'qemu')
 qemu_opts = os.environ.get('QEMU_OPTIONS', '').strip().split(' ')
 
@@ -87,6 +91,10 @@ def qemu_io(*args):
         sys.stderr.write('qemu-io received signal %i: %s\n' % (-exitcode, ' '.join(args)))
     return subp.communicate()[0]
 
+def qemu_nbd(*args):
+    '''Run qemu-nbd in daemon mode and return the parent's exit code'''
+    return subprocess.call(qemu_nbd_args + ['--fork'] + list(args))
+
 def compare_images(img1, img2, fmt1=imgfmt, fmt2=imgfmt):
     '''Return True if two image files are identical'''
     return qemu_img('compare', '-f', fmt1,
@@ -132,8 +140,10 @@ def log(msg, filters=[]):
 class VM(qtest.QEMUQtestMachine):
     '''A QEMU VM'''
 
-    def __init__(self):
-        super(VM, self).__init__(qemu_prog, qemu_opts, test_dir=test_dir,
+    def __init__(self, path_suffix=''):
+        name = "qemu%s-%d" % (path_suffix, os.getpid())
+        super(VM, self).__init__(qemu_prog, qemu_opts, name=name,
+                                 test_dir=test_dir,
                                  socket_scm_helper=socket_scm_helper)
         if debug:
             self._debug = True
@@ -212,6 +222,19 @@ class QMPTestCase(unittest.TestCase):
                     self.fail('invalid index "%s" in path "%s" in "%s"' % (idx, path, str(d)))
         return d
 
+    def flatten_qmp_object(self, obj, output=None, basestr=''):
+        if output is None:
+            output = dict()
+        if isinstance(obj, list):
+            for i in range(len(obj)):
+                self.flatten_qmp_object(obj[i], output, basestr + str(i) + '.')
+        elif isinstance(obj, dict):
+            for key in obj:
+                self.flatten_qmp_object(obj[key], output, basestr + key + '.')
+        else:
+            output[basestr[:-1]] = obj # Strip trailing '.'
+        return output
+
     def assert_qmp_absent(self, d, path):
         try:
             result = self.dictpath(d, path)
@@ -242,6 +265,13 @@ class QMPTestCase(unittest.TestCase):
         self.assertTrue(False, "Cannot find %s %s in result:\n%s" % \
                 (node_name, file_name, result))
 
+    def assert_json_filename_equal(self, json_filename, reference):
+        '''Asserts that the given filename is a json: filename and that its
+           content is equal to the given reference object'''
+        self.assertEqual(json_filename[:5], 'json:')
+        self.assertEqual(self.flatten_qmp_object(json.loads(json_filename[5:])),
+                         self.flatten_qmp_object(reference))
+
     def cancel_and_wait(self, drive='drive0', force=False, resume=False):
         '''Cancel a block job and wait for it to finish, returning the event'''
         result = self.vm.qmp('block-job-cancel', device=drive, force=force)
diff --git a/tests/qemu-iotests/socket_scm_helper.c b/tests/qemu-iotests/socket_scm_helper.c
index 80cadf4..eb76d31 100644
--- a/tests/qemu-iotests/socket_scm_helper.c
+++ b/tests/qemu-iotests/socket_scm_helper.c
@@ -60,7 +60,7 @@ static int send_fd(int fd, int fd_to_send)
 }
 
 /* Convert string to fd number. */
-static int get_fd_num(const char *fd_str)
+static int get_fd_num(const char *fd_str, bool silent)
 {
     int sock;
     char *err;
@@ -68,12 +68,16 @@ static int get_fd_num(const char *fd_str)
     errno = 0;
     sock = strtol(fd_str, &err, 10);
     if (errno) {
-        fprintf(stderr, "Failed in strtol for socket fd, reason: %s\n",
-                strerror(errno));
+        if (!silent) {
+            fprintf(stderr, "Failed in strtol for socket fd, reason: %s\n",
+                    strerror(errno));
+        }
         return -1;
     }
     if (!*fd_str || *err || sock < 0) {
-        fprintf(stderr, "bad numerical value for socket fd '%s'\n", fd_str);
+        if (!silent) {
+            fprintf(stderr, "bad numerical value for socket fd '%s'\n", fd_str);
+        }
         return -1;
     }
 
@@ -104,18 +108,21 @@ int main(int argc, char **argv, char **envp)
     }
 
 
-    sock = get_fd_num(argv[1]);
+    sock = get_fd_num(argv[1], false);
     if (sock < 0) {
         return EXIT_FAILURE;
     }
 
-    /* Now only open a file in readonly mode for test purpose. If more precise
-       control is needed, use python script in file operation, which is
-       supposed to fork and exec this program. */
-    fd = open(argv[2], O_RDONLY);
+    fd = get_fd_num(argv[2], true);
     if (fd < 0) {
-        fprintf(stderr, "Failed to open file '%s'\n", argv[2]);
-        return EXIT_FAILURE;
+        /* Now only open a file in readonly mode for test purpose. If more
+           precise control is needed, use python script in file operation, which
+           is supposed to fork and exec this program. */
+        fd = open(argv[2], O_RDONLY);
+        if (fd < 0) {
+            fprintf(stderr, "Failed to open file '%s'\n", argv[2]);
+            return EXIT_FAILURE;
+        }
     }
 
     ret = send_fd(sock, fd);