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-rw-r--r--async.c8
-rw-r--r--block.c275
-rw-r--r--block/Makefile.objs1
-rw-r--r--block/blkdebug.c2
-rw-r--r--block/blkverify.c4
-rw-r--r--block/io.c71
-rw-r--r--block/qapi.c8
-rw-r--r--block/qcow2.c11
-rw-r--r--block/qcow2.h5
-rw-r--r--block/quorum.c51
-rw-r--r--block/raw-posix.c5
-rw-r--r--block/throttle-groups.c496
-rw-r--r--block/vmdk.c84
-rw-r--r--blockdev.c62
-rw-r--r--default-configs/s390x-softmmu.mak1
-rw-r--r--hmp.c10
-rw-r--r--hw/core/nmi.c20
-rw-r--r--hw/watchdog/Makefile.objs1
-rw-r--r--hw/watchdog/watchdog.c10
-rw-r--r--hw/watchdog/wdt_diag288.c122
-rw-r--r--include/block/block.h15
-rw-r--r--include/block/block_int.h26
-rw-r--r--include/block/throttle-groups.h46
-rw-r--r--include/hw/nmi.h1
-rw-r--r--include/hw/watchdog/wdt_diag288.h36
-rw-r--r--include/qapi/qmp/qdict.h4
-rw-r--r--include/qemu/queue.h6
-rw-r--r--include/qemu/throttle.h46
-rw-r--r--iothread.c11
-rw-r--r--pc-bios/s390-ccw/Makefile2
-rw-r--r--qapi-schema.json6
-rw-r--r--qapi/block-core.json29
-rw-r--r--qemu-options.hx27
-rw-r--r--qmp-commands.hx3
-rw-r--r--qobject/qdict.c111
-rw-r--r--target-s390x/cpu.h1
-rw-r--r--target-s390x/kvm.c18
-rw-r--r--target-s390x/misc_helper.c29
-rw-r--r--tests/check-qdict.c67
-rwxr-xr-xtests/qemu-iotests/0511
-rw-r--r--tests/qemu-iotests/051.out3
-rwxr-xr-xtests/qemu-iotests/09393
-rwxr-xr-xtests/qemu-iotests/10310
-rw-r--r--tests/qemu-iotests/103.out5
-rwxr-xr-xtests/qemu-iotests/11960
-rw-r--r--tests/qemu-iotests/119.out11
-rwxr-xr-xtests/qemu-iotests/12065
-rw-r--r--tests/qemu-iotests/120.out15
-rw-r--r--tests/qemu-iotests/1242
-rwxr-xr-xtests/qemu-iotests/1284
-rw-r--r--tests/qemu-iotests/group2
-rw-r--r--tests/test-aio.c19
-rw-r--r--tests/test-throttle.c163
-rw-r--r--util/throttle.c81
54 files changed, 1875 insertions, 390 deletions
diff --git a/async.c b/async.c
index 46d9e639d7..77d080d6f5 100644
--- a/async.c
+++ b/async.c
@@ -280,6 +280,12 @@ static void aio_timerlist_notify(void *opaque)
     aio_notify(opaque);
 }
 
+static void aio_rfifolock_cb(void *opaque)
+{
+    /* Kick owner thread in case they are blocked in aio_poll() */
+    aio_notify(opaque);
+}
+
 AioContext *aio_context_new(Error **errp)
 {
     int ret;
@@ -297,7 +303,7 @@ AioContext *aio_context_new(Error **errp)
                            event_notifier_test_and_clear);
     ctx->thread_pool = NULL;
     qemu_mutex_init(&ctx->bh_lock);
-    rfifolock_init(&ctx->lock, NULL, NULL);
+    rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx);
     timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
 
     return ctx;
diff --git a/block.c b/block.c
index 2b9ceae02f..dd4f58d6cb 100644
--- a/block.c
+++ b/block.c
@@ -36,6 +36,7 @@
 #include "qmp-commands.h"
 #include "qemu/timer.h"
 #include "qapi-event.h"
+#include "block/throttle-groups.h"
 
 #ifdef CONFIG_BSD
 #include <sys/types.h>
@@ -79,6 +80,12 @@ static QTAILQ_HEAD(, BlockDriverState) graph_bdrv_states =
 static QLIST_HEAD(, BlockDriver) bdrv_drivers =
     QLIST_HEAD_INITIALIZER(bdrv_drivers);
 
+static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
+                             const char *reference, QDict *options, int flags,
+                             BlockDriverState *parent,
+                             const BdrvChildRole *child_role,
+                             BlockDriver *drv, Error **errp);
+
 static void bdrv_dirty_bitmap_truncate(BlockDriverState *bs);
 /* If non-zero, use only whitelisted block drivers */
 static int use_bdrv_whitelist;
@@ -682,8 +689,8 @@ static int bdrv_temp_snapshot_flags(int flags)
 }
 
 /*
- * Returns the flags that bs->file should get, based on the given flags for
- * the parent BDS
+ * Returns the flags that bs->file should get if a protocol driver is expected,
+ * based on the given flags for the parent BDS
  */
 static int bdrv_inherited_flags(int flags)
 {
@@ -700,6 +707,25 @@ static int bdrv_inherited_flags(int flags)
     return flags;
 }
 
+const BdrvChildRole child_file = {
+    .inherit_flags = bdrv_inherited_flags,
+};
+
+/*
+ * Returns the flags that bs->file should get if the use of formats (and not
+ * only protocols) is permitted for it, based on the given flags for the parent
+ * BDS
+ */
+static int bdrv_inherited_fmt_flags(int parent_flags)
+{
+    int flags = child_file.inherit_flags(parent_flags);
+    return flags & ~BDRV_O_PROTOCOL;
+}
+
+const BdrvChildRole child_format = {
+    .inherit_flags = bdrv_inherited_fmt_flags,
+};
+
 /*
  * Returns the flags that bs->backing_hd should get, based on the given flags
  * for the parent BDS
@@ -715,6 +741,10 @@ static int bdrv_backing_flags(int flags)
     return flags;
 }
 
+static const BdrvChildRole child_backing = {
+    .inherit_flags = bdrv_backing_flags,
+};
+
 static int bdrv_open_flags(BlockDriverState *bs, int flags)
 {
     int open_flags = flags | BDRV_O_CACHE_WB;
@@ -767,6 +797,19 @@ static void bdrv_assign_node_name(BlockDriverState *bs,
     QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs, node_list);
 }
 
+static QemuOptsList bdrv_runtime_opts = {
+    .name = "bdrv_common",
+    .head = QTAILQ_HEAD_INITIALIZER(bdrv_runtime_opts.head),
+    .desc = {
+        {
+            .name = "node-name",
+            .type = QEMU_OPT_STRING,
+            .help = "Node name of the block device node",
+        },
+        { /* end of list */ }
+    },
+};
+
 /*
  * Common part for opening disk images and files
  *
@@ -778,6 +821,7 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
     int ret, open_flags;
     const char *filename;
     const char *node_name = NULL;
+    QemuOpts *opts;
     Error *local_err = NULL;
 
     assert(drv != NULL);
@@ -798,23 +842,22 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
 
     trace_bdrv_open_common(bs, filename ?: "", flags, drv->format_name);
 
-    node_name = qdict_get_try_str(options, "node-name");
-    bdrv_assign_node_name(bs, node_name, &local_err);
+    opts = qemu_opts_create(&bdrv_runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
-        return -EINVAL;
+        ret = -EINVAL;
+        goto fail_opts;
     }
-    qdict_del(options, "node-name");
 
-    /* bdrv_open() with directly using a protocol as drv. This layer is already
-     * opened, so assign it to bs (while file becomes a closed BlockDriverState)
-     * and return immediately. */
-    if (file != NULL && drv->bdrv_file_open) {
-        bdrv_swap(file, bs);
-        return 0;
+    node_name = qemu_opt_get(opts, "node-name");
+    bdrv_assign_node_name(bs, node_name, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto fail_opts;
     }
 
-    bs->open_flags = flags;
     bs->guest_block_size = 512;
     bs->request_alignment = 512;
     bs->zero_beyond_eof = true;
@@ -827,7 +870,8 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
                         ? "Driver '%s' can only be used for read-only devices"
                         : "Driver '%s' is not whitelisted",
                    drv->format_name);
-        return -ENOTSUP;
+        ret = -ENOTSUP;
+        goto fail_opts;
     }
 
     assert(bs->copy_on_read == 0); /* bdrv_new() and bdrv_close() make it so */
@@ -836,7 +880,8 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
             bdrv_enable_copy_on_read(bs);
         } else {
             error_setg(errp, "Can't use copy-on-read on read-only device");
-            return -EINVAL;
+            ret = -EINVAL;
+            goto fail_opts;
         }
     }
 
@@ -902,6 +947,8 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
     assert(bdrv_opt_mem_align(bs) != 0);
     assert(bdrv_min_mem_align(bs) != 0);
     assert((bs->request_alignment != 0) || bs->sg);
+
+    qemu_opts_del(opts);
     return 0;
 
 free_and_fail:
@@ -909,6 +956,8 @@ free_and_fail:
     g_free(bs->opaque);
     bs->opaque = NULL;
     bs->drv = NULL;
+fail_opts:
+    qemu_opts_del(opts);
     return ret;
 }
 
@@ -942,14 +991,17 @@ static QDict *parse_json_filename(const char *filename, Error **errp)
 /*
  * Fills in default options for opening images and converts the legacy
  * filename/flags pair to option QDict entries.
+ * The BDRV_O_PROTOCOL flag in *flags will be set or cleared accordingly if a
+ * block driver has been specified explicitly.
  */
-static int bdrv_fill_options(QDict **options, const char **pfilename, int flags,
-                             BlockDriver *drv, Error **errp)
+static int bdrv_fill_options(QDict **options, const char **pfilename,
+                             int *flags, BlockDriver *drv, Error **errp)
 {
     const char *filename = *pfilename;
     const char *drvname;
-    bool protocol = flags & BDRV_O_PROTOCOL;
+    bool protocol = *flags & BDRV_O_PROTOCOL;
     bool parse_filename = false;
+    BlockDriver *tmp_drv;
     Error *local_err = NULL;
 
     /* Parse json: pseudo-protocol */
@@ -967,6 +1019,24 @@ static int bdrv_fill_options(QDict **options, const char **pfilename, int flags,
         *pfilename = filename = NULL;
     }
 
+    drvname = qdict_get_try_str(*options, "driver");
+
+    /* If the user has explicitly specified the driver, this choice should
+     * override the BDRV_O_PROTOCOL flag */
+    tmp_drv = drv;
+    if (!tmp_drv && drvname) {
+        tmp_drv = bdrv_find_format(drvname);
+    }
+    if (tmp_drv) {
+        protocol = tmp_drv->bdrv_file_open;
+    }
+
+    if (protocol) {
+        *flags |= BDRV_O_PROTOCOL;
+    } else {
+        *flags &= ~BDRV_O_PROTOCOL;
+    }
+
     /* Fetch the file name from the options QDict if necessary */
     if (protocol && filename) {
         if (!qdict_haskey(*options, "filename")) {
@@ -981,7 +1051,6 @@ static int bdrv_fill_options(QDict **options, const char **pfilename, int flags,
 
     /* Find the right block driver */
     filename = qdict_get_try_str(*options, "filename");
-    drvname = qdict_get_try_str(*options, "driver");
 
     if (drv) {
         if (drvname) {
@@ -1118,9 +1187,10 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
     }
 
     assert(bs->backing_hd == NULL);
-    ret = bdrv_open(&backing_hd,
-                    *backing_filename ? backing_filename : NULL, NULL, options,
-                    bdrv_backing_flags(bs->open_flags), NULL, &local_err);
+    ret = bdrv_open_inherit(&backing_hd,
+                            *backing_filename ? backing_filename : NULL,
+                            NULL, options, 0, bs, &child_backing,
+                            NULL, &local_err);
     if (ret < 0) {
         bdrv_unref(backing_hd);
         backing_hd = NULL;
@@ -1154,7 +1224,8 @@ free_exit:
  * To conform with the behavior of bdrv_open(), *pbs has to be NULL.
  */
 int bdrv_open_image(BlockDriverState **pbs, const char *filename,
-                    QDict *options, const char *bdref_key, int flags,
+                    QDict *options, const char *bdref_key,
+                    BlockDriverState* parent, const BdrvChildRole *child_role,
                     bool allow_none, Error **errp)
 {
     QDict *image_options;
@@ -1182,7 +1253,8 @@ int bdrv_open_image(BlockDriverState **pbs, const char *filename,
         goto done;
     }
 
-    ret = bdrv_open(pbs, filename, reference, image_options, flags, NULL, errp);
+    ret = bdrv_open_inherit(pbs, filename, reference, image_options, 0,
+                            parent, child_role, NULL, errp);
 
 done:
     qdict_del(options, bdref_key);
@@ -1254,6 +1326,19 @@ out:
     return ret;
 }
 
+static void bdrv_attach_child(BlockDriverState *parent_bs,
+                              BlockDriverState *child_bs,
+                              const BdrvChildRole *child_role)
+{
+    BdrvChild *child = g_new(BdrvChild, 1);
+    *child = (BdrvChild) {
+        .bs     = child_bs,
+        .role   = child_role,
+    };
+
+    QLIST_INSERT_HEAD(&parent_bs->children, child, next);
+}
+
 /*
  * Opens a disk image (raw, qcow2, vmdk, ...)
  *
@@ -1269,9 +1354,11 @@ out:
  * should be opened. If specified, neither options nor a filename may be given,
  * nor can an existing BDS be reused (that is, *pbs has to be NULL).
  */
-int bdrv_open(BlockDriverState **pbs, const char *filename,
-              const char *reference, QDict *options, int flags,
-              BlockDriver *drv, Error **errp)
+static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
+                             const char *reference, QDict *options, int flags,
+                             BlockDriverState *parent,
+                             const BdrvChildRole *child_role,
+                             BlockDriver *drv, Error **errp)
 {
     int ret;
     BlockDriverState *file = NULL, *bs;
@@ -1280,6 +1367,8 @@ int bdrv_open(BlockDriverState **pbs, const char *filename,
     int snapshot_flags = 0;
 
     assert(pbs);
+    assert(!child_role || !flags);
+    assert(!child_role == !parent);
 
     if (reference) {
         bool options_non_empty = options ? qdict_size(options) : false;
@@ -1302,6 +1391,9 @@ int bdrv_open(BlockDriverState **pbs, const char *filename,
             return -ENODEV;
         }
         bdrv_ref(bs);
+        if (child_role) {
+            bdrv_attach_child(parent, bs, child_role);
+        }
         *pbs = bs;
         return 0;
     }
@@ -1317,7 +1409,12 @@ int bdrv_open(BlockDriverState **pbs, const char *filename,
         options = qdict_new();
     }
 
-    ret = bdrv_fill_options(&options, &filename, flags, drv, &local_err);
+    if (child_role) {
+        bs->inherits_from = parent;
+        flags = child_role->inherit_flags(parent->open_flags);
+    }
+
+    ret = bdrv_fill_options(&options, &filename, &flags, drv, &local_err);
     if (local_err) {
         goto fail;
     }
@@ -1336,12 +1433,8 @@ int bdrv_open(BlockDriverState **pbs, const char *filename,
     }
 
     assert(drvname || !(flags & BDRV_O_PROTOCOL));
-    if (drv && !drv->bdrv_file_open) {
-        /* If the user explicitly wants a format driver here, we'll need to add
-         * another layer for the protocol in bs->file */
-        flags &= ~BDRV_O_PROTOCOL;
-    }
 
+    bs->open_flags = flags;
     bs->options = options;
     options = qdict_clone_shallow(options);
 
@@ -1356,9 +1449,9 @@ int bdrv_open(BlockDriverState **pbs, const char *filename,
         }
 
         assert(file == NULL);
+        bs->open_flags = flags;
         ret = bdrv_open_image(&file, filename, options, "file",
-                              bdrv_inherited_flags(flags),
-                              true, &local_err);
+                              bs, &child_file, true, &local_err);
         if (ret < 0) {
             goto fail;
         }
@@ -1377,6 +1470,12 @@ int bdrv_open(BlockDriverState **pbs, const char *filename,
         goto fail;
     }
 
+    /* BDRV_O_PROTOCOL must be set iff a protocol BDS is about to be created */
+    assert(!!(flags & BDRV_O_PROTOCOL) == !!drv->bdrv_file_open);
+    /* file must be NULL if a protocol BDS is about to be created
+     * (the inverse results in an error message from bdrv_open_common()) */
+    assert(!(flags & BDRV_O_PROTOCOL) || !file);
+
     /* Open the image */
     ret = bdrv_open_common(bs, file, options, flags, drv, &local_err);
     if (ret < 0) {
@@ -1439,6 +1538,10 @@ int bdrv_open(BlockDriverState **pbs, const char *filename,
         goto close_and_fail;
     }
 
+    if (child_role) {
+        bdrv_attach_child(parent, bs, child_role);
+    }
+
     QDECREF(options);
     *pbs = bs;
     return 0;
@@ -1475,6 +1578,14 @@ close_and_fail:
     return ret;
 }
 
+int bdrv_open(BlockDriverState **pbs, const char *filename,
+              const char *reference, QDict *options, int flags,
+              BlockDriver *drv, Error **errp)
+{
+    return bdrv_open_inherit(pbs, filename, reference, options, flags, NULL,
+                             NULL, drv, errp);
+}
+
 typedef struct BlockReopenQueueEntry {
      bool prepared;
      BDRVReopenState state;
@@ -1505,6 +1616,8 @@ BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
     assert(bs != NULL);
 
     BlockReopenQueueEntry *bs_entry;
+    BdrvChild *child;
+
     if (bs_queue == NULL) {
         bs_queue = g_new0(BlockReopenQueue, 1);
         QSIMPLEQ_INIT(bs_queue);
@@ -1513,8 +1626,15 @@ BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
     /* bdrv_open() masks this flag out */
     flags &= ~BDRV_O_PROTOCOL;
 
-    if (bs->file) {
-        bdrv_reopen_queue(bs_queue, bs->file, bdrv_inherited_flags(flags));
+    QLIST_FOREACH(child, &bs->children, next) {
+        int child_flags;
+
+        if (child->bs->inherits_from != bs) {
+            continue;
+        }
+
+        child_flags = child->role->inherit_flags(flags);
+        bdrv_reopen_queue(bs_queue, child->bs, child_flags);
     }
 
     bs_entry = g_new0(BlockReopenQueueEntry, 1);
@@ -1725,6 +1845,16 @@ void bdrv_close(BlockDriverState *bs)
     notifier_list_notify(&bs->close_notifiers, bs);
 
     if (bs->drv) {
+        BdrvChild *child, *next;
+
+        QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
+            if (child->bs->inherits_from == bs) {
+                child->bs->inherits_from = NULL;
+            }
+            QLIST_REMOVE(child, next);
+            g_free(child);
+        }
+
         if (bs->backing_hd) {
             BlockDriverState *backing_hd = bs->backing_hd;
             bdrv_set_backing_hd(bs, NULL);
@@ -1822,12 +1952,18 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
     bs_dest->enable_write_cache = bs_src->enable_write_cache;
 
     /* i/o throttled req */
-    memcpy(&bs_dest->throttle_state,
-           &bs_src->throttle_state,
-           sizeof(ThrottleState));
+    bs_dest->throttle_state     = bs_src->throttle_state,
+    bs_dest->io_limits_enabled  = bs_src->io_limits_enabled;
+    bs_dest->pending_reqs[0]    = bs_src->pending_reqs[0];
+    bs_dest->pending_reqs[1]    = bs_src->pending_reqs[1];
     bs_dest->throttled_reqs[0]  = bs_src->throttled_reqs[0];
     bs_dest->throttled_reqs[1]  = bs_src->throttled_reqs[1];
-    bs_dest->io_limits_enabled  = bs_src->io_limits_enabled;
+    memcpy(&bs_dest->round_robin,
+           &bs_src->round_robin,
+           sizeof(bs_dest->round_robin));
+    memcpy(&bs_dest->throttle_timers,
+           &bs_src->throttle_timers,
+           sizeof(ThrottleTimers));
 
     /* r/w error */
     bs_dest->on_read_error      = bs_src->on_read_error;
@@ -1869,6 +2005,10 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
 void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
 {
     BlockDriverState tmp;
+    BdrvChild *child;
+
+    bdrv_drain(bs_new);
+    bdrv_drain(bs_old);
 
     /* The code needs to swap the node_name but simply swapping node_list won't
      * work so first remove the nodes from the graph list, do the swap then
@@ -1881,12 +2021,21 @@ void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
         QTAILQ_REMOVE(&graph_bdrv_states, bs_old, node_list);
     }
 
+    /* If the BlockDriverState is part of a throttling group acquire
+     * its lock since we're going to mess with the protected fields.
+     * Otherwise there's no need to worry since no one else can touch
+     * them. */
+    if (bs_old->throttle_state) {
+        throttle_group_lock(bs_old);
+    }
+
     /* bs_new must be unattached and shouldn't have anything fancy enabled */
     assert(!bs_new->blk);
     assert(QLIST_EMPTY(&bs_new->dirty_bitmaps));
     assert(bs_new->job == NULL);
     assert(bs_new->io_limits_enabled == false);
-    assert(!throttle_have_timer(&bs_new->throttle_state));
+    assert(bs_new->throttle_state == NULL);
+    assert(!throttle_timers_are_initialized(&bs_new->throttle_timers));
 
     tmp = *bs_new;
     *bs_new = *bs_old;
@@ -1903,7 +2052,13 @@ void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
     /* Check a few fields that should remain attached to the device */
     assert(bs_new->job == NULL);
     assert(bs_new->io_limits_enabled == false);
-    assert(!throttle_have_timer(&bs_new->throttle_state));
+    assert(bs_new->throttle_state == NULL);
+    assert(!throttle_timers_are_initialized(&bs_new->throttle_timers));
+
+    /* Release the ThrottleGroup lock */
+    if (bs_old->throttle_state) {
+        throttle_group_unlock(bs_old);
+    }
 
     /* insert the nodes back into the graph node list if needed */
     if (bs_new->node_name[0] != '\0') {
@@ -1913,6 +2068,30 @@ void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
         QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs_old, node_list);
     }
 
+    /*
+     * Update lh_first.le_prev for non-empty lists.
+     *
+     * The head of the op blocker list doesn't change because it is moved back
+     * in bdrv_move_feature_fields().
+     */
+    assert(QLIST_EMPTY(&bs_old->tracked_requests));
+    assert(QLIST_EMPTY(&bs_new->tracked_requests));
+
+    QLIST_FIX_HEAD_PTR(&bs_new->children, next);
+    QLIST_FIX_HEAD_PTR(&bs_old->children, next);
+
+    /* Update references in bs->opaque and children */
+    QLIST_FOREACH(child, &bs_old->children, next) {
+        if (child->bs->inherits_from == bs_new) {
+            child->bs->inherits_from = bs_old;
+        }
+    }
+    QLIST_FOREACH(child, &bs_new->children, next) {
+        if (child->bs->inherits_from == bs_old) {
+            child->bs->inherits_from = bs_new;
+        }
+    }
+
     bdrv_rebind(bs_new);
     bdrv_rebind(bs_old);
 }
@@ -1935,6 +2114,7 @@ void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top)
     /* The contents of 'tmp' will become bs_top, as we are
      * swapping bs_new and bs_top contents. */
     bdrv_set_backing_hd(bs_top, bs_new);
+    bdrv_attach_child(bs_top, bs_new, &child_backing);
 }
 
 static void bdrv_delete(BlockDriverState *bs)
@@ -3220,10 +3400,9 @@ static void bdrv_dirty_bitmap_truncate(BlockDriverState *bs)
     uint64_t size = bdrv_nb_sectors(bs);
 
     QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
-        if (bdrv_dirty_bitmap_frozen(bitmap)) {
-            continue;
-        }
+        assert(!bdrv_dirty_bitmap_frozen(bitmap));
         hbitmap_truncate(bitmap->bitmap, size);
+        bitmap->size = size;
     }
 }
 
@@ -3691,7 +3870,7 @@ void bdrv_detach_aio_context(BlockDriverState *bs)
     }
 
     if (bs->io_limits_enabled) {
-        throttle_detach_aio_context(&bs->throttle_state);
+        throttle_timers_detach_aio_context(&bs->throttle_timers);
     }
     if (bs->drv->bdrv_detach_aio_context) {
         bs->drv->bdrv_detach_aio_context(bs);
@@ -3727,7 +3906,7 @@ void bdrv_attach_aio_context(BlockDriverState *bs,
         bs->drv->bdrv_attach_aio_context(bs, new_context);
     }
     if (bs->io_limits_enabled) {
-        throttle_attach_aio_context(&bs->throttle_state, new_context);
+        throttle_timers_attach_aio_context(&bs->throttle_timers, new_context);
     }
 
     QLIST_FOREACH(ban, &bs->aio_notifiers, list) {
diff --git a/block/Makefile.objs b/block/Makefile.objs
index 0d8c2a4ab6..c34fd7cdc2 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -10,6 +10,7 @@ block-obj-$(CONFIG_WIN32) += raw-win32.o win32-aio.o
 block-obj-$(CONFIG_POSIX) += raw-posix.o
 block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
 block-obj-y += null.o mirror.o io.o
+block-obj-y += throttle-groups.o
 
 block-obj-y += nbd.o nbd-client.o sheepdog.o
 block-obj-$(CONFIG_LIBISCSI) += iscsi.o
diff --git a/block/blkdebug.c b/block/blkdebug.c
index 1e92607ef3..bc247f46f5 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -429,7 +429,7 @@ static int blkdebug_open(BlockDriverState *bs, QDict *options, int flags,
     /* Open the backing file */
     assert(bs->file == NULL);
     ret = bdrv_open_image(&bs->file, qemu_opt_get(opts, "x-image"), options, "image",
-                          flags | BDRV_O_PROTOCOL, false, &local_err);
+                          bs, &child_file, false, &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto out;
diff --git a/block/blkverify.c b/block/blkverify.c
index 438dff8bcb..d277e63220 100644
--- a/block/blkverify.c
+++ b/block/blkverify.c
@@ -125,7 +125,7 @@ static int blkverify_open(BlockDriverState *bs, QDict *options, int flags,
     /* Open the raw file */
     assert(bs->file == NULL);
     ret = bdrv_open_image(&bs->file, qemu_opt_get(opts, "x-raw"), options,
-                          "raw", flags | BDRV_O_PROTOCOL, false, &local_err);
+                          "raw", bs, &child_file, false, &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto fail;
@@ -134,7 +134,7 @@ static int blkverify_open(BlockDriverState *bs, QDict *options, int flags,
     /* Open the test file */
     assert(s->test_file == NULL);
     ret = bdrv_open_image(&s->test_file, qemu_opt_get(opts, "x-image"), options,
-                          "test", flags, false, &local_err);
+                          "test", bs, &child_format, false, &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         s->test_file = NULL;
diff --git a/block/io.c b/block/io.c
index e394d92626..bb4f78784e 100644
--- a/block/io.c
+++ b/block/io.c
@@ -23,9 +23,9 @@
  */
 
 #include "trace.h"
-#include "sysemu/qtest.h"
 #include "block/blockjob.h"
 #include "block/block_int.h"
+#include "block/throttle-groups.h"
 
 #define NOT_DONE 0x7fffffff /* used while emulated sync operation in progress */
 
@@ -65,7 +65,7 @@ void bdrv_set_io_limits(BlockDriverState *bs,
 {
     int i;
 
-    throttle_config(&bs->throttle_state, cfg);
+    throttle_group_config(bs, cfg);
 
     for (i = 0; i < 2; i++) {
         qemu_co_enter_next(&bs->throttled_reqs[i]);
@@ -95,72 +95,33 @@ static bool bdrv_start_throttled_reqs(BlockDriverState *bs)
 void bdrv_io_limits_disable(BlockDriverState *bs)
 {
     bs->io_limits_enabled = false;
-
     bdrv_start_throttled_reqs(bs);
-
-    throttle_destroy(&bs->throttle_state);
-}
-
-static void bdrv_throttle_read_timer_cb(void *opaque)
-{
-    BlockDriverState *bs = opaque;
-    qemu_co_enter_next(&bs->throttled_reqs[0]);
-}
-
-static void bdrv_throttle_write_timer_cb(void *opaque)
-{
-    BlockDriverState *bs = opaque;
-    qemu_co_enter_next(&bs->throttled_reqs[1]);
+    throttle_group_unregister_bs(bs);
 }
 
 /* should be called before bdrv_set_io_limits if a limit is set */
-void bdrv_io_limits_enable(BlockDriverState *bs)
+void bdrv_io_limits_enable(BlockDriverState *bs, const char *group)
 {
-    int clock_type = QEMU_CLOCK_REALTIME;
-
-    if (qtest_enabled()) {
-        /* For testing block IO throttling only */
-        clock_type = QEMU_CLOCK_VIRTUAL;
-    }
     assert(!bs->io_limits_enabled);
-    throttle_init(&bs->throttle_state,
-                  bdrv_get_aio_context(bs),
-                  clock_type,
-                  bdrv_throttle_read_timer_cb,
-                  bdrv_throttle_write_timer_cb,
-                  bs);
+    throttle_group_register_bs(bs, group);
     bs->io_limits_enabled = true;
 }
 
-/* This function makes an IO wait if needed
- *
- * @nb_sectors: the number of sectors of the IO
- * @is_write:   is the IO a write
- */
-static void bdrv_io_limits_intercept(BlockDriverState *bs,
-                                     unsigned int bytes,
-                                     bool is_write)
+void bdrv_io_limits_update_group(BlockDriverState *bs, const char *group)
 {
-    /* does this io must wait */
-    bool must_wait = throttle_schedule_timer(&bs->throttle_state, is_write);
-
-    /* if must wait or any request of this type throttled queue the IO */
-    if (must_wait ||
-        !qemu_co_queue_empty(&bs->throttled_reqs[is_write])) {
-        qemu_co_queue_wait(&bs->throttled_reqs[is_write]);
+    /* this bs is not part of any group */
+    if (!bs->throttle_state) {
+        return;
     }
 
-    /* the IO will be executed, do the accounting */
-    throttle_account(&bs->throttle_state, is_write, bytes);
-
-
-    /* if the next request must wait -> do nothing */
-    if (throttle_schedule_timer(&bs->throttle_state, is_write)) {
+    /* this bs is a part of the same group than the one we want */
+    if (!g_strcmp0(throttle_group_get_name(bs), group)) {
         return;
     }
 
-    /* else queue next request for execution */
-    qemu_co_queue_next(&bs->throttled_reqs[is_write]);
+    /* need to change the group this bs belong to */
+    bdrv_io_limits_disable(bs);
+    bdrv_io_limits_enable(bs, group);
 }
 
 void bdrv_setup_io_funcs(BlockDriver *bdrv)
@@ -967,7 +928,7 @@ static int coroutine_fn bdrv_co_do_preadv(BlockDriverState *bs,
 
     /* throttling disk I/O */
     if (bs->io_limits_enabled) {
-        bdrv_io_limits_intercept(bs, bytes, false);
+        throttle_group_co_io_limits_intercept(bs, bytes, false);
     }
 
     /* Align read if necessary by padding qiov */
@@ -1297,7 +1258,7 @@ static int coroutine_fn bdrv_co_do_pwritev(BlockDriverState *bs,
 
     /* throttling disk I/O */
     if (bs->io_limits_enabled) {
-        bdrv_io_limits_intercept(bs, bytes, true);
+        throttle_group_co_io_limits_intercept(bs, bytes, true);
     }
 
     /*
diff --git a/block/qapi.c b/block/qapi.c
index 18d2b95f54..a738148bce 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -24,6 +24,7 @@
 
 #include "block/qapi.h"
 #include "block/block_int.h"
+#include "block/throttle-groups.h"
 #include "block/write-threshold.h"
 #include "qmp-commands.h"
 #include "qapi-visit.h"
@@ -65,7 +66,9 @@ BlockDeviceInfo *bdrv_block_device_info(BlockDriverState *bs, Error **errp)
 
     if (bs->io_limits_enabled) {
         ThrottleConfig cfg;
-        throttle_get_config(&bs->throttle_state, &cfg);
+
+        throttle_group_get_config(bs, &cfg);
+
         info->bps     = cfg.buckets[THROTTLE_BPS_TOTAL].avg;
         info->bps_rd  = cfg.buckets[THROTTLE_BPS_READ].avg;
         info->bps_wr  = cfg.buckets[THROTTLE_BPS_WRITE].avg;
@@ -90,6 +93,9 @@ BlockDeviceInfo *bdrv_block_device_info(BlockDriverState *bs, Error **errp)
 
         info->has_iops_size = cfg.op_size;
         info->iops_size = cfg.op_size;
+
+        info->has_group = true;
+        info->group = g_strdup(throttle_group_get_name(bs));
     }
 
     info->write_threshold = bdrv_write_threshold_get(bs);
diff --git a/block/qcow2.c b/block/qcow2.c
index f7b4cc6a32..c4f6938a36 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -483,9 +483,11 @@ static const char *overlap_bool_option_names[QCOW2_OL_MAX_BITNR] = {
     [QCOW2_OL_INACTIVE_L2_BITNR]    = QCOW2_OPT_OVERLAP_INACTIVE_L2,
 };
 
-static void read_cache_sizes(QemuOpts *opts, uint64_t *l2_cache_size,
+static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts,
+                             uint64_t *l2_cache_size,
                              uint64_t *refcount_cache_size, Error **errp)
 {
+    BDRVQcowState *s = bs->opaque;
     uint64_t combined_cache_size;
     bool l2_cache_size_set, refcount_cache_size_set, combined_cache_size_set;
 
@@ -525,7 +527,9 @@ static void read_cache_sizes(QemuOpts *opts, uint64_t *l2_cache_size,
         }
     } else {
         if (!l2_cache_size_set && !refcount_cache_size_set) {
-            *l2_cache_size = DEFAULT_L2_CACHE_BYTE_SIZE;
+            *l2_cache_size = MAX(DEFAULT_L2_CACHE_BYTE_SIZE,
+                                 (uint64_t)DEFAULT_L2_CACHE_CLUSTERS
+                                 * s->cluster_size);
             *refcount_cache_size = *l2_cache_size
                                  / DEFAULT_L2_REFCOUNT_SIZE_RATIO;
         } else if (!l2_cache_size_set) {
@@ -803,7 +807,8 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }
 
-    read_cache_sizes(opts, &l2_cache_size, &refcount_cache_size, &local_err);
+    read_cache_sizes(bs, opts, &l2_cache_size, &refcount_cache_size,
+                     &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
         ret = -EINVAL;
diff --git a/block/qcow2.h b/block/qcow2.h
index 0076512af4..5936d299a3 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -62,11 +62,14 @@
 #define MIN_CLUSTER_BITS 9
 #define MAX_CLUSTER_BITS 21
 
-#define MIN_L2_CACHE_SIZE 1 /* cluster */
+/* Must be at least 2 to cover COW */
+#define MIN_L2_CACHE_SIZE 2 /* clusters */
 
 /* Must be at least 4 to cover all cases of refcount table growth */
 #define MIN_REFCOUNT_CACHE_SIZE 4 /* clusters */
 
+/* Whichever is more */
+#define DEFAULT_L2_CACHE_CLUSTERS 8 /* clusters */
 #define DEFAULT_L2_CACHE_BYTE_SIZE 1048576 /* bytes */
 
 /* The refblock cache needs only a fourth of the L2 cache size to cover as many
diff --git a/block/quorum.c b/block/quorum.c
index f91ef75a84..77e55b2775 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -866,25 +866,18 @@ static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
     Error *local_err = NULL;
     QemuOpts *opts = NULL;
     bool *opened;
-    QDict *sub = NULL;
-    QList *list = NULL;
-    const QListEntry *lentry;
     int i;
     int ret = 0;
 
     qdict_flatten(options);
-    qdict_extract_subqdict(options, &sub, "children.");
-    qdict_array_split(sub, &list);
 
-    if (qdict_size(sub)) {
-        error_setg(&local_err, "Invalid option children.%s",
-                   qdict_first(sub)->key);
+    /* count how many different children are present */
+    s->num_children = qdict_array_entries(options, "children.");
+    if (s->num_children < 0) {
+        error_setg(&local_err, "Option children is not a valid array");
         ret = -EINVAL;
         goto exit;
     }
-
-    /* count how many different children are present */
-    s->num_children = qlist_size(list);
     if (s->num_children < 2) {
         error_setg(&local_err,
                    "Number of provided children must be greater than 1");
@@ -937,37 +930,17 @@ static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
     s->bs = g_new0(BlockDriverState *, s->num_children);
     opened = g_new0(bool, s->num_children);
 
-    for (i = 0, lentry = qlist_first(list); lentry;
-         lentry = qlist_next(lentry), i++) {
-        QDict *d;
-        QString *string;
-
-        switch (qobject_type(lentry->value))
-        {
-            /* List of options */
-            case QTYPE_QDICT:
-                d = qobject_to_qdict(lentry->value);
-                QINCREF(d);
-                ret = bdrv_open(&s->bs[i], NULL, NULL, d, flags, NULL,
-                                &local_err);
-                break;
-
-            /* QMP reference */
-            case QTYPE_QSTRING:
-                string = qobject_to_qstring(lentry->value);
-                ret = bdrv_open(&s->bs[i], NULL, qstring_get_str(string), NULL,
-                                flags, NULL, &local_err);
-                break;
-
-            default:
-                error_setg(&local_err, "Specification of child block device %i "
-                           "is invalid", i);
-                ret = -EINVAL;
-        }
+    for (i = 0; i < s->num_children; i++) {
+        char indexstr[32];
+        ret = snprintf(indexstr, 32, "children.%d", i);
+        assert(ret < 32);
 
+        ret = bdrv_open_image(&s->bs[i], NULL, options, indexstr, bs,
+                              &child_format, false, &local_err);
         if (ret < 0) {
             goto close_exit;
         }
+
         opened[i] = true;
     }
 
@@ -990,8 +963,6 @@ exit:
     if (local_err) {
         error_propagate(errp, local_err);
     }
-    QDECREF(list);
-    QDECREF(sub);
     return ret;
 }
 
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 2990e954ae..44ade8cf4e 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -1848,8 +1848,9 @@ static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
         *pnum = nb_sectors;
         ret = BDRV_BLOCK_DATA;
     } else if (data == start) {
-        /* On a data extent, compute sectors to the end of the extent.  */
-        *pnum = MIN(nb_sectors, (hole - start) / BDRV_SECTOR_SIZE);
+        /* On a data extent, compute sectors to the end of the extent,
+         * possibly including a partial sector at EOF. */
+        *pnum = MIN(nb_sectors, DIV_ROUND_UP(hole - start, BDRV_SECTOR_SIZE));
         ret = BDRV_BLOCK_DATA;
     } else {
         /* On a hole, compute sectors to the beginning of the next extent.  */
diff --git a/block/throttle-groups.c b/block/throttle-groups.c
new file mode 100644
index 0000000000..efc462fbc5
--- /dev/null
+++ b/block/throttle-groups.c
@@ -0,0 +1,496 @@
+/*
+ * QEMU block throttling group infrastructure
+ *
+ * Copyright (C) Nodalink, EURL. 2014
+ * Copyright (C) Igalia, S.L. 2015
+ *
+ * Authors:
+ *   Benoît Canet <benoit.canet@nodalink.com>
+ *   Alberto Garcia <berto@igalia.com>
+ *
+ * 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 or
+ * (at your option) version 3 of the License.
+ *
+ * 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/>.
+ */
+
+#include "block/throttle-groups.h"
+#include "qemu/queue.h"
+#include "qemu/thread.h"
+#include "sysemu/qtest.h"
+
+/* The ThrottleGroup structure (with its ThrottleState) is shared
+ * among different BlockDriverState and it's independent from
+ * AioContext, so in order to use it from different threads it needs
+ * its own locking.
+ *
+ * This locking is however handled internally in this file, so it's
+ * mostly transparent to outside users (but see the documentation in
+ * throttle_groups_lock()).
+ *
+ * The whole ThrottleGroup structure is private and invisible to
+ * outside users, that only use it through its ThrottleState.
+ *
+ * In addition to the ThrottleGroup structure, BlockDriverState has
+ * fields that need to be accessed by other members of the group and
+ * therefore also need to be protected by this lock. Once a BDS is
+ * registered in a group those fields can be accessed by other threads
+ * any time.
+ *
+ * Again, all this is handled internally and is mostly transparent to
+ * the outside. The 'throttle_timers' field however has an additional
+ * constraint because it may be temporarily invalid (see for example
+ * bdrv_set_aio_context()). Therefore in this file a thread will
+ * access some other BDS's timers only after verifying that that BDS
+ * has throttled requests in the queue.
+ */
+typedef struct ThrottleGroup {
+    char *name; /* This is constant during the lifetime of the group */
+
+    QemuMutex lock; /* This lock protects the following four fields */
+    ThrottleState ts;
+    QLIST_HEAD(, BlockDriverState) head;
+    BlockDriverState *tokens[2];
+    bool any_timer_armed[2];
+
+    /* These two are protected by the global throttle_groups_lock */
+    unsigned refcount;
+    QTAILQ_ENTRY(ThrottleGroup) list;
+} ThrottleGroup;
+
+static QemuMutex throttle_groups_lock;
+static QTAILQ_HEAD(, ThrottleGroup) throttle_groups =
+    QTAILQ_HEAD_INITIALIZER(throttle_groups);
+
+/* Increments the reference count of a ThrottleGroup given its name.
+ *
+ * If no ThrottleGroup is found with the given name a new one is
+ * created.
+ *
+ * @name: the name of the ThrottleGroup
+ * @ret:  the ThrottleGroup
+ */
+static ThrottleGroup *throttle_group_incref(const char *name)
+{
+    ThrottleGroup *tg = NULL;
+    ThrottleGroup *iter;
+
+    qemu_mutex_lock(&throttle_groups_lock);
+
+    /* Look for an existing group with that name */
+    QTAILQ_FOREACH(iter, &throttle_groups, list) {
+        if (!strcmp(name, iter->name)) {
+            tg = iter;
+            break;
+        }
+    }
+
+    /* Create a new one if not found */
+    if (!tg) {
+        tg = g_new0(ThrottleGroup, 1);
+        tg->name = g_strdup(name);
+        qemu_mutex_init(&tg->lock);
+        throttle_init(&tg->ts);
+        QLIST_INIT(&tg->head);
+
+        QTAILQ_INSERT_TAIL(&throttle_groups, tg, list);
+    }
+
+    tg->refcount++;
+
+    qemu_mutex_unlock(&throttle_groups_lock);
+
+    return tg;
+}
+
+/* Decrease the reference count of a ThrottleGroup.
+ *
+ * When the reference count reaches zero the ThrottleGroup is
+ * destroyed.
+ *
+ * @tg:  The ThrottleGroup to unref
+ */
+static void throttle_group_unref(ThrottleGroup *tg)
+{
+    qemu_mutex_lock(&throttle_groups_lock);
+    if (--tg->refcount == 0) {
+        QTAILQ_REMOVE(&throttle_groups, tg, list);
+        qemu_mutex_destroy(&tg->lock);
+        g_free(tg->name);
+        g_free(tg);
+    }
+    qemu_mutex_unlock(&throttle_groups_lock);
+}
+
+/* Get the name from a BlockDriverState's ThrottleGroup. The name (and
+ * the pointer) is guaranteed to remain constant during the lifetime
+ * of the group.
+ *
+ * @bs:   a BlockDriverState that is member of a throttling group
+ * @ret:  the name of the group.
+ */
+const char *throttle_group_get_name(BlockDriverState *bs)
+{
+    ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
+    return tg->name;
+}
+
+/* Return the next BlockDriverState in the round-robin sequence,
+ * simulating a circular list.
+ *
+ * This assumes that tg->lock is held.
+ *
+ * @bs:  the current BlockDriverState
+ * @ret: the next BlockDriverState in the sequence
+ */
+static BlockDriverState *throttle_group_next_bs(BlockDriverState *bs)
+{
+    ThrottleState *ts = bs->throttle_state;
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+    BlockDriverState *next = QLIST_NEXT(bs, round_robin);
+
+    if (!next) {
+        return QLIST_FIRST(&tg->head);
+    }
+
+    return next;
+}
+
+/* Return the next BlockDriverState in the round-robin sequence with
+ * pending I/O requests.
+ *
+ * This assumes that tg->lock is held.
+ *
+ * @bs:        the current BlockDriverState
+ * @is_write:  the type of operation (read/write)
+ * @ret:       the next BlockDriverState with pending requests, or bs
+ *             if there is none.
+ */
+static BlockDriverState *next_throttle_token(BlockDriverState *bs,
+                                             bool is_write)
+{
+    ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
+    BlockDriverState *token, *start;
+
+    start = token = tg->tokens[is_write];
+
+    /* get next bs round in round robin style */
+    token = throttle_group_next_bs(token);
+    while (token != start && !token->pending_reqs[is_write]) {
+        token = throttle_group_next_bs(token);
+    }
+
+    /* If no IO are queued for scheduling on the next round robin token
+     * then decide the token is the current bs because chances are
+     * the current bs get the current request queued.
+     */
+    if (token == start && !token->pending_reqs[is_write]) {
+        token = bs;
+    }
+
+    return token;
+}
+
+/* Check if the next I/O request for a BlockDriverState needs to be
+ * throttled or not. If there's no timer set in this group, set one
+ * and update the token accordingly.
+ *
+ * This assumes that tg->lock is held.
+ *
+ * @bs:         the current BlockDriverState
+ * @is_write:   the type of operation (read/write)
+ * @ret:        whether the I/O request needs to be throttled or not
+ */
+static bool throttle_group_schedule_timer(BlockDriverState *bs,
+                                          bool is_write)
+{
+    ThrottleState *ts = bs->throttle_state;
+    ThrottleTimers *tt = &bs->throttle_timers;
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+    bool must_wait;
+
+    /* Check if any of the timers in this group is already armed */
+    if (tg->any_timer_armed[is_write]) {
+        return true;
+    }
+
+    must_wait = throttle_schedule_timer(ts, tt, is_write);
+
+    /* If a timer just got armed, set bs as the current token */
+    if (must_wait) {
+        tg->tokens[is_write] = bs;
+        tg->any_timer_armed[is_write] = true;
+    }
+
+    return must_wait;
+}
+
+/* Look for the next pending I/O request and schedule it.
+ *
+ * This assumes that tg->lock is held.
+ *
+ * @bs:        the current BlockDriverState
+ * @is_write:  the type of operation (read/write)
+ */
+static void schedule_next_request(BlockDriverState *bs, bool is_write)
+{
+    ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
+    bool must_wait;
+    BlockDriverState *token;
+
+    /* Check if there's any pending request to schedule next */
+    token = next_throttle_token(bs, is_write);
+    if (!token->pending_reqs[is_write]) {
+        return;
+    }
+
+    /* Set a timer for the request if it needs to be throttled */
+    must_wait = throttle_group_schedule_timer(token, is_write);
+
+    /* If it doesn't have to wait, queue it for immediate execution */
+    if (!must_wait) {
+        /* Give preference to requests from the current bs */
+        if (qemu_in_coroutine() &&
+            qemu_co_queue_next(&bs->throttled_reqs[is_write])) {
+            token = bs;
+        } else {
+            ThrottleTimers *tt = &token->throttle_timers;
+            int64_t now = qemu_clock_get_ns(tt->clock_type);
+            timer_mod(tt->timers[is_write], now + 1);
+            tg->any_timer_armed[is_write] = true;
+        }
+        tg->tokens[is_write] = token;
+    }
+}
+
+/* Check if an I/O request needs to be throttled, wait and set a timer
+ * if necessary, and schedule the next request using a round robin
+ * algorithm.
+ *
+ * @bs:        the current BlockDriverState
+ * @bytes:     the number of bytes for this I/O
+ * @is_write:  the type of operation (read/write)
+ */
+void coroutine_fn throttle_group_co_io_limits_intercept(BlockDriverState *bs,
+                                                        unsigned int bytes,
+                                                        bool is_write)
+{
+    bool must_wait;
+    BlockDriverState *token;
+
+    ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
+    qemu_mutex_lock(&tg->lock);
+
+    /* First we check if this I/O has to be throttled. */
+    token = next_throttle_token(bs, is_write);
+    must_wait = throttle_group_schedule_timer(token, is_write);
+
+    /* Wait if there's a timer set or queued requests of this type */
+    if (must_wait || bs->pending_reqs[is_write]) {
+        bs->pending_reqs[is_write]++;
+        qemu_mutex_unlock(&tg->lock);
+        qemu_co_queue_wait(&bs->throttled_reqs[is_write]);
+        qemu_mutex_lock(&tg->lock);
+        bs->pending_reqs[is_write]--;
+    }
+
+    /* The I/O will be executed, so do the accounting */
+    throttle_account(bs->throttle_state, is_write, bytes);
+
+    /* Schedule the next request */
+    schedule_next_request(bs, is_write);
+
+    qemu_mutex_unlock(&tg->lock);
+}
+
+/* Update the throttle configuration for a particular group. Similar
+ * to throttle_config(), but guarantees atomicity within the
+ * throttling group.
+ *
+ * @bs:  a BlockDriverState that is member of the group
+ * @cfg: the configuration to set
+ */
+void throttle_group_config(BlockDriverState *bs, ThrottleConfig *cfg)
+{
+    ThrottleTimers *tt = &bs->throttle_timers;
+    ThrottleState *ts = bs->throttle_state;
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+    qemu_mutex_lock(&tg->lock);
+    throttle_config(ts, tt, cfg);
+    /* throttle_config() cancels the timers */
+    tg->any_timer_armed[0] = tg->any_timer_armed[1] = false;
+    qemu_mutex_unlock(&tg->lock);
+}
+
+/* Get the throttle configuration from a particular group. Similar to
+ * throttle_get_config(), but guarantees atomicity within the
+ * throttling group.
+ *
+ * @bs:  a BlockDriverState that is member of the group
+ * @cfg: the configuration will be written here
+ */
+void throttle_group_get_config(BlockDriverState *bs, ThrottleConfig *cfg)
+{
+    ThrottleState *ts = bs->throttle_state;
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+    qemu_mutex_lock(&tg->lock);
+    throttle_get_config(ts, cfg);
+    qemu_mutex_unlock(&tg->lock);
+}
+
+/* ThrottleTimers callback. This wakes up a request that was waiting
+ * because it had been throttled.
+ *
+ * @bs:        the BlockDriverState whose request had been throttled
+ * @is_write:  the type of operation (read/write)
+ */
+static void timer_cb(BlockDriverState *bs, bool is_write)
+{
+    ThrottleState *ts = bs->throttle_state;
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+    bool empty_queue;
+
+    /* The timer has just been fired, so we can update the flag */
+    qemu_mutex_lock(&tg->lock);
+    tg->any_timer_armed[is_write] = false;
+    qemu_mutex_unlock(&tg->lock);
+
+    /* Run the request that was waiting for this timer */
+    empty_queue = !qemu_co_enter_next(&bs->throttled_reqs[is_write]);
+
+    /* If the request queue was empty then we have to take care of
+     * scheduling the next one */
+    if (empty_queue) {
+        qemu_mutex_lock(&tg->lock);
+        schedule_next_request(bs, is_write);
+        qemu_mutex_unlock(&tg->lock);
+    }
+}
+
+static void read_timer_cb(void *opaque)
+{
+    timer_cb(opaque, false);
+}
+
+static void write_timer_cb(void *opaque)
+{
+    timer_cb(opaque, true);
+}
+
+/* Register a BlockDriverState in the throttling group, also
+ * initializing its timers and updating its throttle_state pointer to
+ * point to it. If a throttling group with that name does not exist
+ * yet, it will be created.
+ *
+ * @bs:        the BlockDriverState to insert
+ * @groupname: the name of the group
+ */
+void throttle_group_register_bs(BlockDriverState *bs, const char *groupname)
+{
+    int i;
+    ThrottleGroup *tg = throttle_group_incref(groupname);
+    int clock_type = QEMU_CLOCK_REALTIME;
+
+    if (qtest_enabled()) {
+        /* For testing block IO throttling only */
+        clock_type = QEMU_CLOCK_VIRTUAL;
+    }
+
+    bs->throttle_state = &tg->ts;
+
+    qemu_mutex_lock(&tg->lock);
+    /* If the ThrottleGroup is new set this BlockDriverState as the token */
+    for (i = 0; i < 2; i++) {
+        if (!tg->tokens[i]) {
+            tg->tokens[i] = bs;
+        }
+    }
+
+    QLIST_INSERT_HEAD(&tg->head, bs, round_robin);
+
+    throttle_timers_init(&bs->throttle_timers,
+                         bdrv_get_aio_context(bs),
+                         clock_type,
+                         read_timer_cb,
+                         write_timer_cb,
+                         bs);
+
+    qemu_mutex_unlock(&tg->lock);
+}
+
+/* Unregister a BlockDriverState from its group, removing it from the
+ * list, destroying the timers and setting the throttle_state pointer
+ * to NULL.
+ *
+ * The group will be destroyed if it's empty after this operation.
+ *
+ * @bs: the BlockDriverState to remove
+ */
+void throttle_group_unregister_bs(BlockDriverState *bs)
+{
+    ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
+    int i;
+
+    qemu_mutex_lock(&tg->lock);
+    for (i = 0; i < 2; i++) {
+        if (tg->tokens[i] == bs) {
+            BlockDriverState *token = throttle_group_next_bs(bs);
+            /* Take care of the case where this is the last bs in the group */
+            if (token == bs) {
+                token = NULL;
+            }
+            tg->tokens[i] = token;
+        }
+    }
+
+    /* remove the current bs from the list */
+    QLIST_REMOVE(bs, round_robin);
+    throttle_timers_destroy(&bs->throttle_timers);
+    qemu_mutex_unlock(&tg->lock);
+
+    throttle_group_unref(tg);
+    bs->throttle_state = NULL;
+}
+
+/* Acquire the lock of this throttling group.
+ *
+ * You won't normally need to use this. None of the functions from the
+ * ThrottleGroup API require you to acquire the lock since all of them
+ * deal with it internally.
+ *
+ * This should only be used in exceptional cases when you want to
+ * access the protected fields of a BlockDriverState directly
+ * (e.g. bdrv_swap()).
+ *
+ * @bs: a BlockDriverState that is member of the group
+ */
+void throttle_group_lock(BlockDriverState *bs)
+{
+    ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
+    qemu_mutex_lock(&tg->lock);
+}
+
+/* Release the lock of this throttling group.
+ *
+ * See the comments in throttle_group_lock().
+ */
+void throttle_group_unlock(BlockDriverState *bs)
+{
+    ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
+    qemu_mutex_unlock(&tg->lock);
+}
+
+static void throttle_groups_init(void)
+{
+    qemu_mutex_init(&throttle_groups_lock);
+}
+
+block_init(throttle_groups_init);
diff --git a/block/vmdk.c b/block/vmdk.c
index b66745dfdd..be9263a34e 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -321,37 +321,13 @@ static int vmdk_is_cid_valid(BlockDriverState *bs)
     return 1;
 }
 
-/* Queue extents, if any, for reopen() */
+/* We have nothing to do for VMDK reopen, stubs just return success */
 static int vmdk_reopen_prepare(BDRVReopenState *state,
                                BlockReopenQueue *queue, Error **errp)
 {
-    BDRVVmdkState *s;
-    int ret = -1;
-    int i;
-    VmdkExtent *e;
-
     assert(state != NULL);
     assert(state->bs != NULL);
-
-    if (queue == NULL) {
-        error_setg(errp, "No reopen queue for VMDK extents");
-        goto exit;
-    }
-
-    s = state->bs->opaque;
-
-    assert(s != NULL);
-
-    for (i = 0; i < s->num_extents; i++) {
-        e = &s->extents[i];
-        if (e->file != state->bs->file) {
-            bdrv_reopen_queue(queue, e->file, state->flags);
-        }
-    }
-    ret = 0;
-
-exit:
-    return ret;
+    return 0;
 }
 
 static int vmdk_parent_open(BlockDriverState *bs)
@@ -543,7 +519,7 @@ static int vmdk_open_vmfs_sparse(BlockDriverState *bs,
 }
 
 static int vmdk_open_desc_file(BlockDriverState *bs, int flags, char *buf,
-                               Error **errp);
+                               QDict *options, Error **errp);
 
 static char *vmdk_read_desc(BlockDriverState *file, uint64_t desc_offset,
                             Error **errp)
@@ -582,7 +558,7 @@ static char *vmdk_read_desc(BlockDriverState *file, uint64_t desc_offset,
 
 static int vmdk_open_vmdk4(BlockDriverState *bs,
                            BlockDriverState *file,
-                           int flags, Error **errp)
+                           int flags, QDict *options, Error **errp)
 {
     int ret;
     uint32_t magic;
@@ -606,7 +582,7 @@ static int vmdk_open_vmdk4(BlockDriverState *bs,
             if (!buf) {
                 return -EINVAL;
             }
-            ret = vmdk_open_desc_file(bs, flags, buf, errp);
+            ret = vmdk_open_desc_file(bs, flags, buf, options, errp);
             g_free(buf);
             return ret;
         }
@@ -763,7 +739,7 @@ static int vmdk_parse_description(const char *desc, const char *opt_name,
 /* Open an extent file and append to bs array */
 static int vmdk_open_sparse(BlockDriverState *bs,
                             BlockDriverState *file, int flags,
-                            char *buf, Error **errp)
+                            char *buf, QDict *options, Error **errp)
 {
     uint32_t magic;
 
@@ -773,7 +749,7 @@ static int vmdk_open_sparse(BlockDriverState *bs,
             return vmdk_open_vmfs_sparse(bs, file, flags, errp);
             break;
         case VMDK4_MAGIC:
-            return vmdk_open_vmdk4(bs, file, flags, errp);
+            return vmdk_open_vmdk4(bs, file, flags, options, errp);
             break;
         default:
             error_setg(errp, "Image not in VMDK format");
@@ -783,7 +759,8 @@ static int vmdk_open_sparse(BlockDriverState *bs,
 }
 
 static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
-                              const char *desc_file_path, Error **errp)
+                              const char *desc_file_path, QDict *options,
+                              Error **errp)
 {
     int ret;
     int matches;
@@ -797,6 +774,7 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
     BlockDriverState *extent_file;
     BDRVVmdkState *s = bs->opaque;
     VmdkExtent *extent;
+    char extent_opt_prefix[32];
 
     while (*p) {
         /* parse extent line in one of below formats:
@@ -846,8 +824,12 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
         extent_path = g_malloc0(PATH_MAX);
         path_combine(extent_path, PATH_MAX, desc_file_path, fname);
         extent_file = NULL;
-        ret = bdrv_open(&extent_file, extent_path, NULL, NULL,
-                        bs->open_flags | BDRV_O_PROTOCOL, NULL, errp);
+
+        ret = snprintf(extent_opt_prefix, 32, "extents.%d", s->num_extents);
+        assert(ret < 32);
+
+        ret = bdrv_open_image(&extent_file, extent_path, options,
+                              extent_opt_prefix, bs, &child_file, false, errp);
         g_free(extent_path);
         if (ret) {
             return ret;
@@ -870,7 +852,8 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
             if (!buf) {
                 ret = -EINVAL;
             } else {
-                ret = vmdk_open_sparse(bs, extent_file, bs->open_flags, buf, errp);
+                ret = vmdk_open_sparse(bs, extent_file, bs->open_flags, buf,
+                                       options, errp);
             }
             g_free(buf);
             if (ret) {
@@ -898,7 +881,7 @@ next_line:
 }
 
 static int vmdk_open_desc_file(BlockDriverState *bs, int flags, char *buf,
-                               Error **errp)
+                               QDict *options, Error **errp)
 {
     int ret;
     char ct[128];
@@ -920,7 +903,7 @@ static int vmdk_open_desc_file(BlockDriverState *bs, int flags, char *buf,
     }
     s->create_type = g_strdup(ct);
     s->desc_offset = 0;
-    ret = vmdk_parse_extents(buf, bs, bs->file->exact_filename, errp);
+    ret = vmdk_parse_extents(buf, bs, bs->file->exact_filename, options, errp);
 exit:
     return ret;
 }
@@ -942,11 +925,11 @@ static int vmdk_open(BlockDriverState *bs, QDict *options, int flags,
     switch (magic) {
         case VMDK3_MAGIC:
         case VMDK4_MAGIC:
-            ret = vmdk_open_sparse(bs, bs->file, flags, buf, errp);
+            ret = vmdk_open_sparse(bs, bs->file, flags, buf, options, errp);
             s->desc_offset = 0x200;
             break;
         default:
-            ret = vmdk_open_desc_file(bs, flags, buf, errp);
+            ret = vmdk_open_desc_file(bs, flags, buf, options, errp);
             break;
     }
     if (ret) {
@@ -1248,6 +1231,17 @@ static VmdkExtent *find_extent(BDRVVmdkState *s,
     return NULL;
 }
 
+static inline uint64_t vmdk_find_index_in_cluster(VmdkExtent *extent,
+                                                  int64_t sector_num)
+{
+    uint64_t index_in_cluster, extent_begin_sector, extent_relative_sector_num;
+
+    extent_begin_sector = extent->end_sector - extent->sectors;
+    extent_relative_sector_num = sector_num - extent_begin_sector;
+    index_in_cluster = extent_relative_sector_num % extent->cluster_sectors;
+    return index_in_cluster;
+}
+
 static int64_t coroutine_fn vmdk_co_get_block_status(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, int *pnum)
 {
@@ -1285,7 +1279,7 @@ static int64_t coroutine_fn vmdk_co_get_block_status(BlockDriverState *bs,
         break;
     }
 
-    index_in_cluster = sector_num % extent->cluster_sectors;
+    index_in_cluster = vmdk_find_index_in_cluster(extent, sector_num);
     n = extent->cluster_sectors - index_in_cluster;
     if (n > nb_sectors) {
         n = nb_sectors;
@@ -1413,7 +1407,6 @@ static int vmdk_read(BlockDriverState *bs, int64_t sector_num,
     BDRVVmdkState *s = bs->opaque;
     int ret;
     uint64_t n, index_in_cluster;
-    uint64_t extent_begin_sector, extent_relative_sector_num;
     VmdkExtent *extent = NULL;
     uint64_t cluster_offset;
 
@@ -1425,9 +1418,7 @@ static int vmdk_read(BlockDriverState *bs, int64_t sector_num,
         ret = get_cluster_offset(bs, extent, NULL,
                                  sector_num << 9, false, &cluster_offset,
                                  0, 0);
-        extent_begin_sector = extent->end_sector - extent->sectors;
-        extent_relative_sector_num = sector_num - extent_begin_sector;
-        index_in_cluster = extent_relative_sector_num % extent->cluster_sectors;
+        index_in_cluster = vmdk_find_index_in_cluster(extent, sector_num);
         n = extent->cluster_sectors - index_in_cluster;
         if (n > nb_sectors) {
             n = nb_sectors;
@@ -1489,7 +1480,6 @@ static int vmdk_write(BlockDriverState *bs, int64_t sector_num,
     VmdkExtent *extent = NULL;
     int ret;
     int64_t index_in_cluster, n;
-    uint64_t extent_begin_sector, extent_relative_sector_num;
     uint64_t cluster_offset;
     VmdkMetaData m_data;
 
@@ -1505,9 +1495,7 @@ static int vmdk_write(BlockDriverState *bs, int64_t sector_num,
         if (!extent) {
             return -EIO;
         }
-        extent_begin_sector = extent->end_sector - extent->sectors;
-        extent_relative_sector_num = sector_num - extent_begin_sector;
-        index_in_cluster = extent_relative_sector_num % extent->cluster_sectors;
+        index_in_cluster = vmdk_find_index_in_cluster(extent, sector_num);
         n = extent->cluster_sectors - index_in_cluster;
         if (n > nb_sectors) {
             n = nb_sectors;
diff --git a/blockdev.c b/blockdev.c
index de94a8bcb3..3aa1ae6698 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -34,6 +34,7 @@
 #include "sysemu/blockdev.h"
 #include "hw/block/block.h"
 #include "block/blockjob.h"
+#include "block/throttle-groups.h"
 #include "monitor/monitor.h"
 #include "qemu/option.h"
 #include "qemu/config-file.h"
@@ -357,6 +358,7 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
     const char *id;
     bool has_driver_specific_opts;
     BlockdevDetectZeroesOptions detect_zeroes;
+    const char *throttling_group;
 
     /* Check common options by copying from bs_opts to opts, all other options
      * stay in bs_opts for processing by bdrv_open(). */
@@ -391,13 +393,13 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
         }
     }
 
-    if (qemu_opt_get_bool(opts, "cache.writeback", true)) {
+    if (qemu_opt_get_bool(opts, BDRV_OPT_CACHE_WB, true)) {
         bdrv_flags |= BDRV_O_CACHE_WB;
     }
-    if (qemu_opt_get_bool(opts, "cache.direct", false)) {
+    if (qemu_opt_get_bool(opts, BDRV_OPT_CACHE_DIRECT, false)) {
         bdrv_flags |= BDRV_O_NOCACHE;
     }
-    if (qemu_opt_get_bool(opts, "cache.no-flush", false)) {
+    if (qemu_opt_get_bool(opts, BDRV_OPT_CACHE_NO_FLUSH, false)) {
         bdrv_flags |= BDRV_O_NO_FLUSH;
     }
 
@@ -459,6 +461,8 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
 
     cfg.op_size = qemu_opt_get_number(opts, "throttling.iops-size", 0);
 
+    throttling_group = qemu_opt_get(opts, "throttling.group");
+
     if (!check_throttle_config(&cfg, &error)) {
         error_propagate(errp, error);
         goto early_err;
@@ -547,7 +551,10 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
 
     /* disk I/O throttling */
     if (throttle_enabled(&cfg)) {
-        bdrv_io_limits_enable(bs);
+        if (!throttling_group) {
+            throttling_group = blk_name(blk);
+        }
+        bdrv_io_limits_enable(bs, throttling_group);
         bdrv_set_io_limits(bs, &cfg);
     }
 
@@ -711,6 +718,8 @@ DriveInfo *drive_new(QemuOpts *all_opts, BlockInterfaceType block_default_type)
 
         { "iops_size",      "throttling.iops-size" },
 
+        { "group",          "throttling.group" },
+
         { "readonly",       "read-only" },
     };
 
@@ -733,16 +742,16 @@ DriveInfo *drive_new(QemuOpts *all_opts, BlockInterfaceType block_default_type)
         }
 
         /* Specific options take precedence */
-        if (!qemu_opt_get(all_opts, "cache.writeback")) {
-            qemu_opt_set_bool(all_opts, "cache.writeback",
+        if (!qemu_opt_get(all_opts, BDRV_OPT_CACHE_WB)) {
+            qemu_opt_set_bool(all_opts, BDRV_OPT_CACHE_WB,
                               !!(flags & BDRV_O_CACHE_WB), &error_abort);
         }
-        if (!qemu_opt_get(all_opts, "cache.direct")) {
-            qemu_opt_set_bool(all_opts, "cache.direct",
+        if (!qemu_opt_get(all_opts, BDRV_OPT_CACHE_DIRECT)) {
+            qemu_opt_set_bool(all_opts, BDRV_OPT_CACHE_DIRECT,
                               !!(flags & BDRV_O_NOCACHE), &error_abort);
         }
-        if (!qemu_opt_get(all_opts, "cache.no-flush")) {
-            qemu_opt_set_bool(all_opts, "cache.no-flush",
+        if (!qemu_opt_get(all_opts, BDRV_OPT_CACHE_NO_FLUSH)) {
+            qemu_opt_set_bool(all_opts, BDRV_OPT_CACHE_NO_FLUSH,
                               !!(flags & BDRV_O_NO_FLUSH), &error_abort);
         }
         qemu_opt_unset(all_opts, "cache");
@@ -1951,7 +1960,9 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
                                bool has_iops_wr_max,
                                int64_t iops_wr_max,
                                bool has_iops_size,
-                               int64_t iops_size, Error **errp)
+                               int64_t iops_size,
+                               bool has_group,
+                               const char *group, Error **errp)
 {
     ThrottleConfig cfg;
     BlockDriverState *bs;
@@ -2004,14 +2015,19 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
     aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(aio_context);
 
-    if (!bs->io_limits_enabled && throttle_enabled(&cfg)) {
-        bdrv_io_limits_enable(bs);
-    } else if (bs->io_limits_enabled && !throttle_enabled(&cfg)) {
-        bdrv_io_limits_disable(bs);
-    }
-
-    if (bs->io_limits_enabled) {
+    if (throttle_enabled(&cfg)) {
+        /* Enable I/O limits if they're not enabled yet, otherwise
+         * just update the throttling group. */
+        if (!bs->io_limits_enabled) {
+            bdrv_io_limits_enable(bs, has_group ? group : device);
+        } else if (has_group) {
+            bdrv_io_limits_update_group(bs, group);
+        }
+        /* Set the new throttling configuration */
         bdrv_set_io_limits(bs, &cfg);
+    } else if (bs->io_limits_enabled) {
+        /* If all throttling settings are set to 0, disable I/O limits */
+        bdrv_io_limits_disable(bs);
     }
 
     aio_context_release(aio_context);
@@ -3105,15 +3121,15 @@ QemuOptsList qemu_common_drive_opts = {
             .type = QEMU_OPT_STRING,
             .help = "discard operation (ignore/off, unmap/on)",
         },{
-            .name = "cache.writeback",
+            .name = BDRV_OPT_CACHE_WB,
             .type = QEMU_OPT_BOOL,
             .help = "enables writeback mode for any caches",
         },{
-            .name = "cache.direct",
+            .name = BDRV_OPT_CACHE_DIRECT,
             .type = QEMU_OPT_BOOL,
             .help = "enables use of O_DIRECT (bypass the host page cache)",
         },{
-            .name = "cache.no-flush",
+            .name = BDRV_OPT_CACHE_NO_FLUSH,
             .type = QEMU_OPT_BOOL,
             .help = "ignore any flush requests for the device",
         },{
@@ -3189,6 +3205,10 @@ QemuOptsList qemu_common_drive_opts = {
             .type = QEMU_OPT_NUMBER,
             .help = "when limiting by iops max size of an I/O in bytes",
         },{
+            .name = "throttling.group",
+            .type = QEMU_OPT_STRING,
+            .help = "name of the block throttling group",
+        },{
             .name = "copy-on-read",
             .type = QEMU_OPT_BOOL,
             .help = "copy read data from backing file into image file",
diff --git a/default-configs/s390x-softmmu.mak b/default-configs/s390x-softmmu.mak
index f9e13f177e..36e15de336 100644
--- a/default-configs/s390x-softmmu.mak
+++ b/default-configs/s390x-softmmu.mak
@@ -4,3 +4,4 @@ CONFIG_VIRTIO=y
 CONFIG_SCLPCONSOLE=y
 CONFIG_S390_FLIC=y
 CONFIG_S390_FLIC_KVM=$(CONFIG_KVM)
+CONFIG_WDT_DIAG288=y
diff --git a/hmp.c b/hmp.c
index 1e7cac02ac..23abc7d9f1 100644
--- a/hmp.c
+++ b/hmp.c
@@ -400,7 +400,8 @@ static void print_block_info(Monitor *mon, BlockInfo *info,
                         " iops_max=%" PRId64
                         " iops_rd_max=%" PRId64
                         " iops_wr_max=%" PRId64
-                        " iops_size=%" PRId64 "\n",
+                        " iops_size=%" PRId64
+                        " group=%s\n",
                         inserted->bps,
                         inserted->bps_rd,
                         inserted->bps_wr,
@@ -413,7 +414,8 @@ static void print_block_info(Monitor *mon, BlockInfo *info,
                         inserted->iops_max,
                         inserted->iops_rd_max,
                         inserted->iops_wr_max,
-                        inserted->iops_size);
+                        inserted->iops_size,
+                        inserted->group);
     }
 
     if (verbose) {
@@ -1357,7 +1359,9 @@ void hmp_block_set_io_throttle(Monitor *mon, const QDict *qdict)
                               false,
                               0,
                               false, /* No default I/O size */
-                              0, &err);
+                              0,
+                              false,
+                              NULL, &err);
     hmp_handle_error(mon, &err);
 }
 
diff --git a/hw/core/nmi.c b/hw/core/nmi.c
index 3dff020659..5260d6c1ec 100644
--- a/hw/core/nmi.c
+++ b/hw/core/nmi.c
@@ -21,6 +21,7 @@
 
 #include "hw/nmi.h"
 #include "qapi/qmp/qerror.h"
+#include "monitor/monitor.h"
 
 struct do_nmi_s {
     int cpu_index;
@@ -70,6 +71,25 @@ void nmi_monitor_handle(int cpu_index, Error **errp)
     }
 }
 
+void inject_nmi(void)
+{
+#if defined(TARGET_I386)
+    CPUState *cs;
+
+    CPU_FOREACH(cs) {
+        X86CPU *cpu = X86_CPU(cs);
+
+        if (!cpu->apic_state) {
+            cpu_interrupt(cs, CPU_INTERRUPT_NMI);
+        } else {
+            apic_deliver_nmi(cpu->apic_state);
+        }
+    }
+#else
+    nmi_monitor_handle(0, NULL);
+#endif
+}
+
 static const TypeInfo nmi_info = {
     .name          = TYPE_NMI,
     .parent        = TYPE_INTERFACE,
diff --git a/hw/watchdog/Makefile.objs b/hw/watchdog/Makefile.objs
index 4b0374a555..72e3ffd93c 100644
--- a/hw/watchdog/Makefile.objs
+++ b/hw/watchdog/Makefile.objs
@@ -1,3 +1,4 @@
 common-obj-y += watchdog.o
 common-obj-$(CONFIG_WDT_IB6300ESB) += wdt_i6300esb.o
 common-obj-$(CONFIG_WDT_IB700) += wdt_ib700.o
+common-obj-$(CONFIG_WDT_DIAG288) += wdt_diag288.o
diff --git a/hw/watchdog/watchdog.c b/hw/watchdog/watchdog.c
index 54440c91c5..8d4b0eeeb0 100644
--- a/hw/watchdog/watchdog.c
+++ b/hw/watchdog/watchdog.c
@@ -27,6 +27,7 @@
 #include "sysemu/sysemu.h"
 #include "sysemu/watchdog.h"
 #include "qapi-event.h"
+#include "hw/nmi.h"
 
 /* Possible values for action parameter. */
 #define WDT_RESET        1	/* Hard reset. */
@@ -35,6 +36,7 @@
 #define WDT_PAUSE        4	/* Pause. */
 #define WDT_DEBUG        5	/* Prints a message and continues running. */
 #define WDT_NONE         6	/* Do nothing. */
+#define WDT_NMI          7	/* Inject nmi into the guest */
 
 static int watchdog_action = WDT_RESET;
 static QLIST_HEAD(watchdog_list, WatchdogTimerModel) watchdog_list;
@@ -95,6 +97,8 @@ int select_watchdog_action(const char *p)
         watchdog_action = WDT_DEBUG;
     else if (strcasecmp(p, "none") == 0)
         watchdog_action = WDT_NONE;
+    else if (strcasecmp(p, "inject-nmi") == 0)
+        watchdog_action = WDT_NMI;
     else
         return -1;
 
@@ -138,5 +142,11 @@ void watchdog_perform_action(void)
     case WDT_NONE:
         qapi_event_send_watchdog(WATCHDOG_EXPIRATION_ACTION_NONE, &error_abort);
         break;
+
+    case WDT_NMI:
+        qapi_event_send_watchdog(WATCHDOG_EXPIRATION_ACTION_INJECT_NMI,
+                                 &error_abort);
+        inject_nmi();
+        break;
     }
 }
diff --git a/hw/watchdog/wdt_diag288.c b/hw/watchdog/wdt_diag288.c
new file mode 100644
index 0000000000..1185e0681c
--- /dev/null
+++ b/hw/watchdog/wdt_diag288.c
@@ -0,0 +1,122 @@
+/*
+ * watchdog device diag288 support
+ *
+ * Copyright IBM, Corp. 2015
+ *
+ * Authors:
+ *  Xu Wang <gesaint@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or (at your
+ * option) any later version.  See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "sysemu/watchdog.h"
+#include "hw/sysbus.h"
+#include "qemu/timer.h"
+#include "hw/watchdog/wdt_diag288.h"
+
+static WatchdogTimerModel model = {
+    .wdt_name = TYPE_WDT_DIAG288,
+    .wdt_description = "diag288 device for s390x platform",
+};
+
+static const VMStateDescription vmstate_diag288 = {
+    .name = "vmstate_diag288",
+    .version_id = 0,
+    .minimum_version_id = 0,
+    .fields = (VMStateField[]) {
+        VMSTATE_TIMER_PTR(timer, DIAG288State),
+        VMSTATE_BOOL(enabled, DIAG288State),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static void wdt_diag288_reset(DeviceState *dev)
+{
+    DIAG288State *diag288 = DIAG288(dev);
+
+    diag288->enabled = false;
+    timer_del(diag288->timer);
+}
+
+static void diag288_timer_expired(void *dev)
+{
+    qemu_log_mask(CPU_LOG_RESET, "Watchdog timer expired.\n");
+    watchdog_perform_action();
+    wdt_diag288_reset(dev);
+}
+
+static int wdt_diag288_handle_timer(DIAG288State *diag288,
+                                     uint64_t func, uint64_t timeout)
+{
+    switch (func) {
+    case WDT_DIAG288_INIT:
+        diag288->enabled = true;
+        /* fall through */
+    case WDT_DIAG288_CHANGE:
+        if (!diag288->enabled) {
+            return -1;
+        }
+        timer_mod(diag288->timer,
+                  qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
+                  timeout * get_ticks_per_sec());
+        break;
+    case WDT_DIAG288_CANCEL:
+        if (!diag288->enabled) {
+            return -1;
+        }
+        diag288->enabled = false;
+        timer_del(diag288->timer);
+        break;
+    default:
+        return -1;
+    }
+
+    return 0;
+}
+
+static void wdt_diag288_realize(DeviceState *dev, Error **errp)
+{
+    DIAG288State *diag288 = DIAG288(dev);
+
+    diag288->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, diag288_timer_expired,
+                                  dev);
+}
+
+static void wdt_diag288_unrealize(DeviceState *dev, Error **errp)
+{
+    DIAG288State *diag288 = DIAG288(dev);
+
+    timer_del(diag288->timer);
+    timer_free(diag288->timer);
+}
+
+static void wdt_diag288_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    DIAG288Class *diag288 = DIAG288_CLASS(klass);
+
+    dc->realize = wdt_diag288_realize;
+    dc->unrealize = wdt_diag288_unrealize;
+    dc->reset = wdt_diag288_reset;
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+    dc->vmsd = &vmstate_diag288;
+    diag288->handle_timer = wdt_diag288_handle_timer;
+}
+
+static const TypeInfo wdt_diag288_info = {
+    .class_init = wdt_diag288_class_init,
+    .parent = TYPE_DEVICE,
+    .name  = TYPE_WDT_DIAG288,
+    .instance_size  = sizeof(DIAG288State),
+    .class_size = sizeof(DIAG288Class),
+};
+
+static void wdt_diag288_register_types(void)
+{
+    watchdog_add_model(&model);
+    type_register_static(&wdt_diag288_info);
+}
+
+type_init(wdt_diag288_register_types)
diff --git a/include/block/block.h b/include/block/block.h
index f7680b6e68..07bb724f7d 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -12,6 +12,7 @@
 /* block.c */
 typedef struct BlockDriver BlockDriver;
 typedef struct BlockJob BlockJob;
+typedef struct BdrvChildRole BdrvChildRole;
 
 typedef struct BlockDriverInfo {
     /* in bytes, 0 if irrelevant */
@@ -90,6 +91,14 @@ typedef struct HDGeometry {
 
 #define BDRV_O_CACHE_MASK  (BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH)
 
+
+/* Option names of options parsed by the block layer */
+
+#define BDRV_OPT_CACHE_WB       "cache.writeback"
+#define BDRV_OPT_CACHE_DIRECT   "cache.direct"
+#define BDRV_OPT_CACHE_NO_FLUSH "cache.no-flush"
+
+
 #define BDRV_SECTOR_BITS   9
 #define BDRV_SECTOR_SIZE   (1ULL << BDRV_SECTOR_BITS)
 #define BDRV_SECTOR_MASK   ~(BDRV_SECTOR_SIZE - 1)
@@ -173,8 +182,9 @@ void bdrv_stats_print(Monitor *mon, const QObject *data);
 void bdrv_info_stats(Monitor *mon, QObject **ret_data);
 
 /* disk I/O throttling */
-void bdrv_io_limits_enable(BlockDriverState *bs);
+void bdrv_io_limits_enable(BlockDriverState *bs, const char *group);
 void bdrv_io_limits_disable(BlockDriverState *bs);
+void bdrv_io_limits_update_group(BlockDriverState *bs, const char *group);
 
 void bdrv_init(void);
 void bdrv_init_with_whitelist(void);
@@ -195,7 +205,8 @@ void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top);
 int bdrv_parse_cache_flags(const char *mode, int *flags);
 int bdrv_parse_discard_flags(const char *mode, int *flags);
 int bdrv_open_image(BlockDriverState **pbs, const char *filename,
-                    QDict *options, const char *bdref_key, int flags,
+                    QDict *options, const char *bdref_key,
+                    BlockDriverState* parent, const BdrvChildRole *child_role,
                     bool allow_none, Error **errp);
 void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd);
 int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index f004378d58..888ec09e96 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -330,6 +330,19 @@ typedef struct BdrvAioNotifier {
     QLIST_ENTRY(BdrvAioNotifier) list;
 } BdrvAioNotifier;
 
+struct BdrvChildRole {
+    int (*inherit_flags)(int parent_flags);
+};
+
+extern const BdrvChildRole child_file;
+extern const BdrvChildRole child_format;
+
+typedef struct BdrvChild {
+    BlockDriverState *bs;
+    const BdrvChildRole *role;
+    QLIST_ENTRY(BdrvChild) next;
+} BdrvChild;
+
 /*
  * Note: the function bdrv_append() copies and swaps contents of
  * BlockDriverStates, so if you add new fields to this struct, please
@@ -379,9 +392,14 @@ struct BlockDriverState {
     unsigned int serialising_in_flight;
 
     /* I/O throttling */
-    ThrottleState throttle_state;
     CoQueue      throttled_reqs[2];
     bool         io_limits_enabled;
+    /* The following fields are protected by the ThrottleGroup lock.
+     * See the ThrottleGroup documentation for details. */
+    ThrottleState *throttle_state;
+    ThrottleTimers throttle_timers;
+    unsigned       pending_reqs[2];
+    QLIST_ENTRY(BlockDriverState) round_robin;
 
     /* I/O stats (display with "info blockstats"). */
     BlockAcctStats stats;
@@ -424,6 +442,12 @@ struct BlockDriverState {
     /* long-running background operation */
     BlockJob *job;
 
+    /* The node that this node inherited default options from (and a reopen on
+     * which can affect this node by changing these defaults). This is always a
+     * parent node of this node. */
+    BlockDriverState *inherits_from;
+    QLIST_HEAD(, BdrvChild) children;
+
     QDict *options;
     BlockdevDetectZeroesOptions detect_zeroes;
 
diff --git a/include/block/throttle-groups.h b/include/block/throttle-groups.h
new file mode 100644
index 0000000000..fab113f6d1
--- /dev/null
+++ b/include/block/throttle-groups.h
@@ -0,0 +1,46 @@
+/*
+ * QEMU block throttling group infrastructure
+ *
+ * Copyright (C) Nodalink, EURL. 2014
+ * Copyright (C) Igalia, S.L. 2015
+ *
+ * Authors:
+ *   Benoît Canet <benoit.canet@nodalink.com>
+ *   Alberto Garcia <berto@igalia.com>
+ *
+ * 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 or
+ * (at your option) version 3 of the License.
+ *
+ * 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/>.
+ */
+
+#ifndef THROTTLE_GROUPS_H
+#define THROTTLE_GROUPS_H
+
+#include "qemu/throttle.h"
+#include "block/block_int.h"
+
+const char *throttle_group_get_name(BlockDriverState *bs);
+
+void throttle_group_config(BlockDriverState *bs, ThrottleConfig *cfg);
+void throttle_group_get_config(BlockDriverState *bs, ThrottleConfig *cfg);
+
+void throttle_group_register_bs(BlockDriverState *bs, const char *groupname);
+void throttle_group_unregister_bs(BlockDriverState *bs);
+
+void coroutine_fn throttle_group_co_io_limits_intercept(BlockDriverState *bs,
+                                                        unsigned int bytes,
+                                                        bool is_write);
+
+void throttle_group_lock(BlockDriverState *bs);
+void throttle_group_unlock(BlockDriverState *bs);
+
+#endif
diff --git a/include/hw/nmi.h b/include/hw/nmi.h
index b541772e1d..f4cec6257d 100644
--- a/include/hw/nmi.h
+++ b/include/hw/nmi.h
@@ -45,5 +45,6 @@ typedef struct NMIClass {
 } NMIClass;
 
 void nmi_monitor_handle(int cpu_index, Error **errp);
+void inject_nmi(void);
 
 #endif /* NMI_H */
diff --git a/include/hw/watchdog/wdt_diag288.h b/include/hw/watchdog/wdt_diag288.h
new file mode 100644
index 0000000000..7f3fd450dc
--- /dev/null
+++ b/include/hw/watchdog/wdt_diag288.h
@@ -0,0 +1,36 @@
+#ifndef WDT_DIAG288_H
+#define WDT_DIAG288_H
+
+#include "hw/qdev.h"
+
+#define TYPE_WDT_DIAG288 "diag288"
+#define DIAG288(obj) \
+    OBJECT_CHECK(DIAG288State, (obj), TYPE_WDT_DIAG288)
+#define DIAG288_CLASS(klass) \
+    OBJECT_CLASS_CHECK(DIAG288Class, (klass), TYPE_WDT_DIAG288)
+#define DIAG288_GET_CLASS(obj) \
+    OBJECT_GET_CLASS(DIAG288Class, (obj), TYPE_WDT_DIAG288)
+
+#define WDT_DIAG288_INIT      0
+#define WDT_DIAG288_CHANGE    1
+#define WDT_DIAG288_CANCEL    2
+
+typedef struct DIAG288State {
+    /*< private >*/
+    DeviceState parent_obj;
+    QEMUTimer *timer;
+    bool enabled;
+
+    /*< public >*/
+} DIAG288State;
+
+typedef struct DIAG288Class {
+    /*< private >*/
+    DeviceClass parent_class;
+
+    /*< public >*/
+    int (*handle_timer)(DIAG288State *dev,
+                        uint64_t func, uint64_t timeout);
+} DIAG288Class;
+
+#endif  /* WDT_DIAG288_H */
diff --git a/include/qapi/qmp/qdict.h b/include/qapi/qmp/qdict.h
index d68f4eb4d5..9fbf68ee0c 100644
--- a/include/qapi/qmp/qdict.h
+++ b/include/qapi/qmp/qdict.h
@@ -65,11 +65,15 @@ int64_t qdict_get_try_int(const QDict *qdict, const char *key,
 int qdict_get_try_bool(const QDict *qdict, const char *key, int def_value);
 const char *qdict_get_try_str(const QDict *qdict, const char *key);
 
+void qdict_copy_default(QDict *dst, QDict *src, const char *key);
+void qdict_set_default_str(QDict *dst, const char *key, const char *val);
+
 QDict *qdict_clone_shallow(const QDict *src);
 void qdict_flatten(QDict *qdict);
 
 void qdict_extract_subqdict(QDict *src, QDict **dst, const char *start);
 void qdict_array_split(QDict *src, QList **dst);
+int qdict_array_entries(QDict *src, const char *subqdict);
 
 void qdict_join(QDict *dest, QDict *src, bool overwrite);
 
diff --git a/include/qemu/queue.h b/include/qemu/queue.h
index f781aa20a8..a8d3cb8e63 100644
--- a/include/qemu/queue.h
+++ b/include/qemu/queue.h
@@ -117,6 +117,12 @@ struct {                                                                \
         }                                                               \
 } while (/*CONSTCOND*/0)
 
+#define QLIST_FIX_HEAD_PTR(head, field) do {                            \
+        if ((head)->lh_first != NULL) {                                 \
+            (head)->lh_first->field.le_prev = &(head)->lh_first;        \
+        }                                                               \
+} while (/*CONSTCOND*/0)
+
 #define QLIST_INSERT_AFTER(listelm, elm, field) do {                    \
         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
                 (listelm)->field.le_next->field.le_prev =               \
diff --git a/include/qemu/throttle.h b/include/qemu/throttle.h
index b890613a9c..5af76f0ff4 100644
--- a/include/qemu/throttle.h
+++ b/include/qemu/throttle.h
@@ -1,10 +1,12 @@
 /*
  * QEMU throttling infrastructure
  *
- * Copyright (C) Nodalink, SARL. 2013
+ * Copyright (C) Nodalink, EURL. 2013-2014
+ * Copyright (C) Igalia, S.L. 2015
  *
- * Author:
- *   Benoît Canet <benoit.canet@irqsave.net>
+ * Authors:
+ *   Benoît Canet <benoit.canet@nodalink.com>
+ *   Alberto Garcia <berto@igalia.com>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -65,14 +67,17 @@ typedef struct ThrottleConfig {
 typedef struct ThrottleState {
     ThrottleConfig cfg;       /* configuration */
     int64_t previous_leak;    /* timestamp of the last leak done */
-    QEMUTimer * timers[2];    /* timers used to do the throttling */
+} ThrottleState;
+
+typedef struct ThrottleTimers {
+    QEMUTimer *timers[2];     /* timers used to do the throttling */
     QEMUClockType clock_type; /* the clock used */
 
     /* Callbacks */
     QEMUTimerCB *read_timer_cb;
     QEMUTimerCB *write_timer_cb;
     void *timer_opaque;
-} ThrottleState;
+} ThrottleTimers;
 
 /* operations on single leaky buckets */
 void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta);
@@ -86,20 +91,23 @@ bool throttle_compute_timer(ThrottleState *ts,
                             int64_t *next_timestamp);
 
 /* init/destroy cycle */
-void throttle_init(ThrottleState *ts,
-                   AioContext *aio_context,
-                   QEMUClockType clock_type,
-                   void (read_timer)(void *),
-                   void (write_timer)(void *),
-                   void *timer_opaque);
+void throttle_init(ThrottleState *ts);
+
+void throttle_timers_init(ThrottleTimers *tt,
+                          AioContext *aio_context,
+                          QEMUClockType clock_type,
+                          QEMUTimerCB *read_timer_cb,
+                          QEMUTimerCB *write_timer_cb,
+                          void *timer_opaque);
 
-void throttle_destroy(ThrottleState *ts);
+void throttle_timers_destroy(ThrottleTimers *tt);
 
-void throttle_detach_aio_context(ThrottleState *ts);
+void throttle_timers_detach_aio_context(ThrottleTimers *tt);
 
-void throttle_attach_aio_context(ThrottleState *ts, AioContext *new_context);
+void throttle_timers_attach_aio_context(ThrottleTimers *tt,
+                                        AioContext *new_context);
 
-bool throttle_have_timer(ThrottleState *ts);
+bool throttle_timers_are_initialized(ThrottleTimers *tt);
 
 /* configuration */
 bool throttle_enabled(ThrottleConfig *cfg);
@@ -108,12 +116,16 @@ bool throttle_conflicting(ThrottleConfig *cfg);
 
 bool throttle_is_valid(ThrottleConfig *cfg);
 
-void throttle_config(ThrottleState *ts, ThrottleConfig *cfg);
+void throttle_config(ThrottleState *ts,
+                     ThrottleTimers *tt,
+                     ThrottleConfig *cfg);
 
 void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg);
 
 /* usage */
-bool throttle_schedule_timer(ThrottleState *ts, bool is_write);
+bool throttle_schedule_timer(ThrottleState *ts,
+                             ThrottleTimers *tt,
+                             bool is_write);
 
 void throttle_account(ThrottleState *ts, bool is_write, uint64_t size);
 
diff --git a/iothread.c b/iothread.c
index 0416fc4268..878a594ef4 100644
--- a/iothread.c
+++ b/iothread.c
@@ -31,14 +31,21 @@ typedef ObjectClass IOThreadClass;
 static void *iothread_run(void *opaque)
 {
     IOThread *iothread = opaque;
+    bool blocking;
 
     qemu_mutex_lock(&iothread->init_done_lock);
     iothread->thread_id = qemu_get_thread_id();
     qemu_cond_signal(&iothread->init_done_cond);
     qemu_mutex_unlock(&iothread->init_done_lock);
 
-    while (!atomic_read(&iothread->stopping)) {
-        aio_poll(iothread->ctx, true);
+    while (!iothread->stopping) {
+        aio_context_acquire(iothread->ctx);
+        blocking = true;
+        while (!iothread->stopping && aio_poll(iothread->ctx, blocking)) {
+            /* Progress was made, keep going */
+            blocking = false;
+        }
+        aio_context_release(iothread->ctx);
     }
     return NULL;
 }
diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
index 009bb8de1c..746603a315 100644
--- a/pc-bios/s390-ccw/Makefile
+++ b/pc-bios/s390-ccw/Makefile
@@ -10,7 +10,7 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
 .PHONY : all clean build-all
 
 OBJECTS = start.o main.o bootmap.o sclp-ascii.o virtio.o
-CFLAGS += -fPIE -fno-stack-protector -ffreestanding
+CFLAGS += -fPIE -fno-stack-protector -ffreestanding -fno-delete-null-pointer-checks
 LDFLAGS += -Wl,-pie -nostdlib
 
 build-all: s390-ccw.img
diff --git a/qapi-schema.json b/qapi-schema.json
index bcc604b813..106008cdeb 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3746,10 +3746,14 @@
 #
 # @none: nothing is done
 #
+# @inject-nmi: a non-maskable interrupt is injected into the first VCPU (all
+#              VCPUS on x86) (since 2.4)
+#
 # Since: 2.1
 ##
 { 'enum': 'WatchdogExpirationAction',
-  'data': [ 'reset', 'shutdown', 'poweroff', 'pause', 'debug', 'none' ] }
+  'data': [ 'reset', 'shutdown', 'poweroff', 'pause', 'debug', 'none',
+            'inject-nmi' ] }
 
 ##
 # @IoOperationType
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 8411d4f83a..afa9d3d1f3 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -259,6 +259,8 @@
 #
 # @iops_size: #optional an I/O size in bytes (Since 1.7)
 #
+# @group: #optional throttle group name (Since 2.4)
+#
 # @cache: the cache mode used for the block device (since: 2.3)
 #
 # @write_threshold: configured write threshold for the device.
@@ -278,7 +280,7 @@
             '*bps_max': 'int', '*bps_rd_max': 'int',
             '*bps_wr_max': 'int', '*iops_max': 'int',
             '*iops_rd_max': 'int', '*iops_wr_max': 'int',
-            '*iops_size': 'int', 'cache': 'BlockdevCacheInfo',
+            '*iops_size': 'int', '*group': 'str', 'cache': 'BlockdevCacheInfo',
             'write_threshold': 'int' } }
 
 ##
@@ -1062,6 +1064,27 @@
 #
 # Change I/O throttle limits for a block drive.
 #
+# Since QEMU 2.4, each device with I/O limits is member of a throttle
+# group.
+#
+# If two or more devices are members of the same group, the limits
+# will apply to the combined I/O of the whole group in a round-robin
+# fashion. Therefore, setting new I/O limits to a device will affect
+# the whole group.
+#
+# The name of the group can be specified using the 'group' parameter.
+# If the parameter is unset, it is assumed to be the current group of
+# that device. If it's not in any group yet, the name of the device
+# will be used as the name for its group.
+#
+# The 'group' parameter can also be used to move a device to a
+# different group. In this case the limits specified in the parameters
+# will be applied to the new group only.
+#
+# I/O limits can be disabled by setting all of them to 0. In this case
+# the device will be removed from its group and the rest of its
+# members will no be affected. The 'group' parameter is ignored.
+#
 # @device: The name of the device
 #
 # @bps: total throughput limit in bytes per second
@@ -1090,6 +1113,8 @@
 #
 # @iops_size: #optional an I/O size in bytes (Since 1.7)
 #
+# @group: #optional throttle group name (Since 2.4)
+#
 # Returns: Nothing on success
 #          If @device is not a valid block device, DeviceNotFound
 #
@@ -1101,7 +1126,7 @@
             '*bps_max': 'int', '*bps_rd_max': 'int',
             '*bps_wr_max': 'int', '*iops_max': 'int',
             '*iops_rd_max': 'int', '*iops_wr_max': 'int',
-            '*iops_size': 'int' } }
+            '*iops_size': 'int', '*group': 'str' } }
 
 ##
 # @block-stream:
diff --git a/qemu-options.hx b/qemu-options.hx
index 1d281f6818..bf1683e5b4 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -468,6 +468,7 @@ DEF("drive", HAS_ARG, QEMU_OPTION_drive,
     "       [[,bps_max=bm]|[[,bps_rd_max=rm][,bps_wr_max=wm]]]\n"
     "       [[,iops_max=im]|[[,iops_rd_max=irm][,iops_wr_max=iwm]]]\n"
     "       [[,iops_size=is]]\n"
+    "       [[,group=g]]\n"
     "                use 'file' as a drive image\n", QEMU_ARCH_ALL)
 STEXI
 @item -drive @var{option}[,@var{option}[,@var{option}[,...]]]
@@ -3152,7 +3153,7 @@ when the shift value is high (how high depends on the host machine).
 ETEXI
 
 DEF("watchdog", HAS_ARG, QEMU_OPTION_watchdog, \
-    "-watchdog i6300esb|ib700\n" \
+    "-watchdog model\n" \
     "                enable virtual hardware watchdog [default=none]\n",
     QEMU_ARCH_ALL)
 STEXI
@@ -3160,16 +3161,24 @@ STEXI
 @findex -watchdog
 Create a virtual hardware watchdog device.  Once enabled (by a guest
 action), the watchdog must be periodically polled by an agent inside
-the guest or else the guest will be restarted.
+the guest or else the guest will be restarted. Choose a model for
+which your guest has drivers.
 
-The @var{model} is the model of hardware watchdog to emulate.  Choices
-for model are: @code{ib700} (iBASE 700) which is a very simple ISA
-watchdog with a single timer, or @code{i6300esb} (Intel 6300ESB I/O
-controller hub) which is a much more featureful PCI-based dual-timer
-watchdog.  Choose a model for which your guest has drivers.
-
-Use @code{-watchdog help} to list available hardware models.  Only one
+The @var{model} is the model of hardware watchdog to emulate. Use
+@code{-watchdog help} to list available hardware models. Only one
 watchdog can be enabled for a guest.
+
+The following models may be available:
+@table @option
+@item ib700
+iBASE 700 is a very simple ISA watchdog with a single timer.
+@item i6300esb
+Intel 6300ESB I/O controller hub is a much more featureful PCI-based
+dual-timer watchdog.
+@item diag288
+A virtual watchdog for s390x backed by the diagnose 288 hypercall
+(currently KVM only).
+@end table
 ETEXI
 
 DEF("watchdog-action", HAS_ARG, QEMU_OPTION_watchdog_action, \
diff --git a/qmp-commands.hx b/qmp-commands.hx
index c97d0d7667..1db6524e97 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1853,7 +1853,7 @@ EQMP
 
     {
         .name       = "block_set_io_throttle",
-        .args_type  = "device:B,bps:l,bps_rd:l,bps_wr:l,iops:l,iops_rd:l,iops_wr:l,bps_max:l?,bps_rd_max:l?,bps_wr_max:l?,iops_max:l?,iops_rd_max:l?,iops_wr_max:l?,iops_size:l?",
+        .args_type  = "device:B,bps:l,bps_rd:l,bps_wr:l,iops:l,iops_rd:l,iops_wr:l,bps_max:l?,bps_rd_max:l?,bps_wr_max:l?,iops_max:l?,iops_rd_max:l?,iops_wr_max:l?,iops_size:l?,group:s?",
         .mhandler.cmd_new = qmp_marshal_input_block_set_io_throttle,
     },
 
@@ -1879,6 +1879,7 @@ Arguments:
 - "iops_rd_max":  read I/O operations max (json-int)
 - "iops_wr_max":  write I/O operations max (json-int)
 - "iops_size":  I/O size in bytes when limiting (json-int)
+- "group": throttle group name (json-string)
 
 Example:
 
diff --git a/qobject/qdict.c b/qobject/qdict.c
index ea239f082e..190791becf 100644
--- a/qobject/qdict.c
+++ b/qobject/qdict.c
@@ -477,6 +477,39 @@ static void qdict_destroy_obj(QObject *obj)
     g_free(qdict);
 }
 
+/**
+ * qdict_copy_default(): If no entry mapped by 'key' exists in 'dst' yet, the
+ * value of 'key' in 'src' is copied there (and the refcount increased
+ * accordingly).
+ */
+void qdict_copy_default(QDict *dst, QDict *src, const char *key)
+{
+    QObject *val;
+
+    if (qdict_haskey(dst, key)) {
+        return;
+    }
+
+    val = qdict_get(src, key);
+    if (val) {
+        qobject_incref(val);
+        qdict_put_obj(dst, key, val);
+    }
+}
+
+/**
+ * qdict_set_default_str(): If no entry mapped by 'key' exists in 'dst' yet, a
+ * new QString initialised by 'val' is put there.
+ */
+void qdict_set_default_str(QDict *dst, const char *key, const char *val)
+{
+    if (qdict_haskey(dst, key)) {
+        return;
+    }
+
+    qdict_put(dst, key, qstring_from_str(val));
+}
+
 static void qdict_flatten_qdict(QDict *qdict, QDict *target,
                                 const char *prefix);
 
@@ -597,17 +630,21 @@ void qdict_extract_subqdict(QDict *src, QDict **dst, const char *start)
     }
 }
 
-static bool qdict_has_prefixed_entries(const QDict *src, const char *start)
+static int qdict_count_prefixed_entries(const QDict *src, const char *start)
 {
     const QDictEntry *entry;
+    int count = 0;
 
     for (entry = qdict_first(src); entry; entry = qdict_next(src, entry)) {
         if (strstart(entry->key, start, NULL)) {
-            return true;
+            if (count == INT_MAX) {
+                return -ERANGE;
+            }
+            count++;
         }
     }
 
-    return false;
+    return count;
 }
 
 /**
@@ -646,7 +683,8 @@ void qdict_array_split(QDict *src, QList **dst)
         snprintf_ret = snprintf(prefix, 32, "%u.", i);
         assert(snprintf_ret < 32);
 
-        is_subqdict = qdict_has_prefixed_entries(src, prefix);
+        /* Overflow is the same as positive non-zero results */
+        is_subqdict = qdict_count_prefixed_entries(src, prefix);
 
         // There may be either a single subordinate object (named "%u") or
         // multiple objects (each with a key prefixed "%u."), but not both.
@@ -667,6 +705,71 @@ void qdict_array_split(QDict *src, QList **dst)
 }
 
 /**
+ * qdict_array_entries(): Returns the number of direct array entries if the
+ * sub-QDict of src specified by the prefix in subqdict (or src itself for
+ * prefix == "") is valid as an array, i.e. the length of the created list if
+ * the sub-QDict would become empty after calling qdict_array_split() on it. If
+ * the array is not valid, -EINVAL is returned.
+ */
+int qdict_array_entries(QDict *src, const char *subqdict)
+{
+    const QDictEntry *entry;
+    unsigned i;
+    unsigned entries = 0;
+    size_t subqdict_len = strlen(subqdict);
+
+    assert(!subqdict_len || subqdict[subqdict_len - 1] == '.');
+
+    /* qdict_array_split() loops until UINT_MAX, but as we want to return
+     * negative errors, we only have a signed return value here. Any additional
+     * entries will lead to -EINVAL. */
+    for (i = 0; i < INT_MAX; i++) {
+        QObject *subqobj;
+        int subqdict_entries;
+        size_t slen = 32 + subqdict_len;
+        char indexstr[slen], prefix[slen];
+        size_t snprintf_ret;
+
+        snprintf_ret = snprintf(indexstr, slen, "%s%u", subqdict, i);
+        assert(snprintf_ret < slen);
+
+        subqobj = qdict_get(src, indexstr);
+
+        snprintf_ret = snprintf(prefix, slen, "%s%u.", subqdict, i);
+        assert(snprintf_ret < slen);
+
+        subqdict_entries = qdict_count_prefixed_entries(src, prefix);
+        if (subqdict_entries < 0) {
+            return subqdict_entries;
+        }
+
+        /* There may be either a single subordinate object (named "%u") or
+         * multiple objects (each with a key prefixed "%u."), but not both. */
+        if (subqobj && subqdict_entries) {
+            return -EINVAL;
+        } else if (!subqobj && !subqdict_entries) {
+            break;
+        }
+
+        entries += subqdict_entries ? subqdict_entries : 1;
+    }
+
+    /* Consider everything handled that isn't part of the given sub-QDict */
+    for (entry = qdict_first(src); entry; entry = qdict_next(src, entry)) {
+        if (!strstart(qdict_entry_key(entry), subqdict, NULL)) {
+            entries++;
+        }
+    }
+
+    /* Anything left in the sub-QDict that wasn't handled? */
+    if (qdict_size(src) != entries) {
+        return -EINVAL;
+    }
+
+    return i;
+}
+
+/**
  * qdict_join(): Absorb the src QDict into the dest QDict, that is, move all
  * elements from src to dest.
  *
diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index 584e74b89a..d63eb51186 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -1100,6 +1100,7 @@ uint32_t set_cc_nz_f128(float128 v);
 
 /* misc_helper.c */
 #ifndef CONFIG_USER_ONLY
+int handle_diag_288(CPUS390XState *env, uint64_t r1, uint64_t r3);
 void handle_diag_308(CPUS390XState *env, uint64_t r1, uint64_t r3);
 #endif
 void program_interrupt(CPUS390XState *env, uint32_t code, int ilen);
diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c
index f6f61b9619..b02ff8d61d 100644
--- a/target-s390x/kvm.c
+++ b/target-s390x/kvm.c
@@ -98,6 +98,7 @@
 #define PRIV_E3_MPCIFC                  0xd0
 #define PRIV_E3_STPCIFC                 0xd4
 
+#define DIAG_TIMEREVENT                 0x288
 #define DIAG_IPL                        0x308
 #define DIAG_KVM_HYPERCALL              0x500
 #define DIAG_KVM_BREAKPOINT             0x501
@@ -1267,6 +1268,20 @@ static int handle_hypercall(S390CPU *cpu, struct kvm_run *run)
     return ret;
 }
 
+static void kvm_handle_diag_288(S390CPU *cpu, struct kvm_run *run)
+{
+    uint64_t r1, r3;
+    int rc;
+
+    cpu_synchronize_state(CPU(cpu));
+    r1 = (run->s390_sieic.ipa & 0x00f0) >> 4;
+    r3 = run->s390_sieic.ipa & 0x000f;
+    rc = handle_diag_288(&cpu->env, r1, r3);
+    if (rc) {
+        enter_pgmcheck(cpu, PGM_SPECIFICATION);
+    }
+}
+
 static void kvm_handle_diag_308(S390CPU *cpu, struct kvm_run *run)
 {
     uint64_t r1, r3;
@@ -1306,6 +1321,9 @@ static int handle_diag(S390CPU *cpu, struct kvm_run *run, uint32_t ipb)
      */
     func_code = decode_basedisp_rs(&cpu->env, ipb, NULL) & DIAG_KVM_CODE_MASK;
     switch (func_code) {
+    case DIAG_TIMEREVENT:
+        kvm_handle_diag_288(cpu, run);
+        break;
     case DIAG_IPL:
         kvm_handle_diag_308(cpu, run);
         break;
diff --git a/target-s390x/misc_helper.c b/target-s390x/misc_helper.c
index b375ab724b..6711504221 100644
--- a/target-s390x/misc_helper.c
+++ b/target-s390x/misc_helper.c
@@ -30,6 +30,7 @@
 #include <linux/kvm.h>
 #endif
 #include "exec/cpu_ldst.h"
+#include "hw/watchdog/wdt_diag288.h"
 
 #if !defined(CONFIG_USER_ONLY)
 #include "sysemu/cpus.h"
@@ -153,6 +154,34 @@ static int load_normal_reset(S390CPU *cpu)
     return 0;
 }
 
+int handle_diag_288(CPUS390XState *env, uint64_t r1, uint64_t r3)
+{
+    uint64_t func = env->regs[r1];
+    uint64_t timeout = env->regs[r1 + 1];
+    uint64_t action = env->regs[r3];
+    Object *obj;
+    DIAG288State *diag288;
+    DIAG288Class *diag288_class;
+
+    if (r1 % 2 || action != 0) {
+        return -1;
+    }
+
+    /* Timeout must be more than 15 seconds except for timer deletion */
+    if (func != WDT_DIAG288_CANCEL && timeout < 15) {
+        return -1;
+    }
+
+    obj = object_resolve_path_type("", TYPE_WDT_DIAG288, NULL);
+    if (!obj) {
+        return -1;
+    }
+
+    diag288 = DIAG288(obj);
+    diag288_class = DIAG288_GET_CLASS(diag288);
+    return diag288_class->handle_timer(diag288, func, timeout);
+}
+
 #define DIAG_308_RC_OK              0x0001
 #define DIAG_308_RC_NO_CONF         0x0102
 #define DIAG_308_RC_INVALID         0x0402
diff --git a/tests/check-qdict.c b/tests/check-qdict.c
index a9296f0833..a136f2addf 100644
--- a/tests/check-qdict.c
+++ b/tests/check-qdict.c
@@ -152,6 +152,28 @@ static void qdict_get_try_str_test(void)
     QDECREF(tests_dict);
 }
 
+static void qdict_defaults_test(void)
+{
+    QDict *dict, *copy;
+
+    dict = qdict_new();
+    copy = qdict_new();
+
+    qdict_set_default_str(dict, "foo", "abc");
+    qdict_set_default_str(dict, "foo", "def");
+    g_assert_cmpstr(qdict_get_str(dict, "foo"), ==, "abc");
+    qdict_set_default_str(dict, "bar", "ghi");
+
+    qdict_copy_default(copy, dict, "foo");
+    g_assert_cmpstr(qdict_get_str(copy, "foo"), ==, "abc");
+    qdict_set_default_str(copy, "bar", "xyz");
+    qdict_copy_default(copy, dict, "bar");
+    g_assert_cmpstr(qdict_get_str(copy, "bar"), ==, "xyz");
+
+    QDECREF(copy);
+    QDECREF(dict);
+}
+
 static void qdict_haskey_not_test(void)
 {
     QDict *tests_dict = qdict_new();
@@ -444,6 +466,49 @@ static void qdict_array_split_test(void)
     QDECREF(test_dict);
 }
 
+static void qdict_array_entries_test(void)
+{
+    QDict *dict = qdict_new();
+
+    g_assert_cmpint(qdict_array_entries(dict, "foo."), ==, 0);
+
+    qdict_put(dict, "bar", qint_from_int(0));
+    qdict_put(dict, "baz.0", qint_from_int(0));
+    g_assert_cmpint(qdict_array_entries(dict, "foo."), ==, 0);
+
+    qdict_put(dict, "foo.1", qint_from_int(0));
+    g_assert_cmpint(qdict_array_entries(dict, "foo."), ==, -EINVAL);
+    qdict_put(dict, "foo.0", qint_from_int(0));
+    g_assert_cmpint(qdict_array_entries(dict, "foo."), ==, 2);
+    qdict_put(dict, "foo.bar", qint_from_int(0));
+    g_assert_cmpint(qdict_array_entries(dict, "foo."), ==, -EINVAL);
+    qdict_del(dict, "foo.bar");
+
+    qdict_put(dict, "foo.2.a", qint_from_int(0));
+    qdict_put(dict, "foo.2.b", qint_from_int(0));
+    qdict_put(dict, "foo.2.c", qint_from_int(0));
+    g_assert_cmpint(qdict_array_entries(dict, "foo."), ==, 3);
+    g_assert_cmpint(qdict_array_entries(dict, ""), ==, -EINVAL);
+
+    QDECREF(dict);
+
+    dict = qdict_new();
+    qdict_put(dict, "1", qint_from_int(0));
+    g_assert_cmpint(qdict_array_entries(dict, ""), ==, -EINVAL);
+    qdict_put(dict, "0", qint_from_int(0));
+    g_assert_cmpint(qdict_array_entries(dict, ""), ==, 2);
+    qdict_put(dict, "bar", qint_from_int(0));
+    g_assert_cmpint(qdict_array_entries(dict, ""), ==, -EINVAL);
+    qdict_del(dict, "bar");
+
+    qdict_put(dict, "2.a", qint_from_int(0));
+    qdict_put(dict, "2.b", qint_from_int(0));
+    qdict_put(dict, "2.c", qint_from_int(0));
+    g_assert_cmpint(qdict_array_entries(dict, ""), ==, 3);
+
+    QDECREF(dict);
+}
+
 static void qdict_join_test(void)
 {
     QDict *dict1, *dict2;
@@ -663,6 +728,7 @@ int main(int argc, char **argv)
     g_test_add_func("/public/get_try_int", qdict_get_try_int_test);
     g_test_add_func("/public/get_str", qdict_get_str_test);
     g_test_add_func("/public/get_try_str", qdict_get_try_str_test);
+    g_test_add_func("/public/defaults", qdict_defaults_test);
     g_test_add_func("/public/haskey_not", qdict_haskey_not_test);
     g_test_add_func("/public/haskey", qdict_haskey_test);
     g_test_add_func("/public/del", qdict_del_test);
@@ -670,6 +736,7 @@ int main(int argc, char **argv)
     g_test_add_func("/public/iterapi", qdict_iterapi_test);
     g_test_add_func("/public/flatten", qdict_flatten_test);
     g_test_add_func("/public/array_split", qdict_array_split_test);
+    g_test_add_func("/public/array_entries", qdict_array_entries_test);
     g_test_add_func("/public/join", qdict_join_test);
 
     g_test_add_func("/errors/put_exists", qdict_put_exists_test);
diff --git a/tests/qemu-iotests/051 b/tests/qemu-iotests/051
index 0360f37e5a..4a8055b673 100755
--- a/tests/qemu-iotests/051
+++ b/tests/qemu-iotests/051
@@ -194,7 +194,6 @@ echo === Specifying the protocol layer ===
 echo
 
 run_qemu -drive file="$TEST_IMG",file.driver=file
-run_qemu -drive file="$TEST_IMG",file.driver=qcow2
 
 echo
 echo === Leaving out required options ===
diff --git a/tests/qemu-iotests/051.out b/tests/qemu-iotests/051.out
index 2890eac084..652dd63bf8 100644
--- a/tests/qemu-iotests/051.out
+++ b/tests/qemu-iotests/051.out
@@ -253,9 +253,6 @@ Testing: -drive file=TEST_DIR/t.qcow2,file.driver=file
 QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) qququiquit
 
-Testing: -drive file=TEST_DIR/t.qcow2,file.driver=qcow2
-QEMU_PROG: -drive file=TEST_DIR/t.qcow2,file.driver=qcow2: Block format 'qcow2' used by device '' doesn't support the option 'filename'
-
 
 === Leaving out required options ===
 
diff --git a/tests/qemu-iotests/093 b/tests/qemu-iotests/093
index b9096a55d4..c0e9e2b0b5 100755
--- a/tests/qemu-iotests/093
+++ b/tests/qemu-iotests/093
@@ -3,6 +3,7 @@
 # Tests for IO throttling
 #
 # Copyright (C) 2015 Red Hat, Inc.
+# Copyright (C) 2015 Igalia, S.L.
 #
 # 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
@@ -22,6 +23,7 @@ import iotests
 
 class ThrottleTestCase(iotests.QMPTestCase):
     test_img = "null-aio://"
+    max_drives = 3
 
     def blockstats(self, device):
         result = self.vm.qmp("query-blockstats")
@@ -32,26 +34,31 @@ class ThrottleTestCase(iotests.QMPTestCase):
         raise Exception("Device not found for blockstats: %s" % device)
 
     def setUp(self):
-        self.vm = iotests.VM().add_drive(self.test_img)
+        self.vm = iotests.VM()
+        for i in range(0, self.max_drives):
+            self.vm.add_drive(self.test_img)
         self.vm.launch()
 
     def tearDown(self):
         self.vm.shutdown()
 
-    def do_test_throttle(self, seconds, params):
+    def do_test_throttle(self, ndrives, seconds, params):
         def check_limit(limit, num):
             # IO throttling algorithm is discrete, allow 10% error so the test
             # is more robust
             return limit == 0 or \
-                   (num < seconds * limit * 1.1
-                   and num > seconds * limit * 0.9)
+                   (num < seconds * limit * 1.1 / ndrives
+                   and num > seconds * limit * 0.9 / ndrives)
 
         nsec_per_sec = 1000000000
 
-        params['device'] = 'drive0'
+        params['group'] = 'test'
 
-        result = self.vm.qmp("block_set_io_throttle", conv_keys=False, **params)
-        self.assert_qmp(result, 'return', {})
+        # Set the I/O throttling parameters to all drives
+        for i in range(0, ndrives):
+            params['device'] = 'drive%d' % i
+            result = self.vm.qmp("block_set_io_throttle", conv_keys=False, **params)
+            self.assert_qmp(result, 'return', {})
 
         # Set vm clock to a known value
         ns = seconds * nsec_per_sec
@@ -66,32 +73,60 @@ class ThrottleTestCase(iotests.QMPTestCase):
                     params['iops'] / 2,
                     params['iops_rd'])
         rd_nr *= seconds * 2
+        rd_nr /= ndrives
         wr_nr = max(params['bps'] / rq_size / 2,
                     params['bps_wr'] / rq_size,
                     params['iops'] / 2,
                     params['iops_wr'])
         wr_nr *= seconds * 2
+        wr_nr /= ndrives
+
+        # Send I/O requests to all drives
         for i in range(rd_nr):
-            self.vm.hmp_qemu_io("drive0", "aio_read %d %d" % (i * rq_size, rq_size))
-        for i in range(wr_nr):
-            self.vm.hmp_qemu_io("drive0", "aio_write %d %d" % (i * rq_size, rq_size))
+            for drive in range(0, ndrives):
+                self.vm.hmp_qemu_io("drive%d" % drive, "aio_read %d %d" %
+                                    (i * rq_size, rq_size))
 
-        start_rd_bytes, start_rd_iops, start_wr_bytes, start_wr_iops = self.blockstats('drive0')
+        for i in range(wr_nr):
+            for drive in range(0, ndrives):
+                self.vm.hmp_qemu_io("drive%d" % drive, "aio_write %d %d" %
+                                    (i * rq_size, rq_size))
+
+        # We'll store the I/O stats for each drive in these arrays
+        start_rd_bytes = [0] * ndrives
+        start_rd_iops  = [0] * ndrives
+        start_wr_bytes = [0] * ndrives
+        start_wr_iops  = [0] * ndrives
+        end_rd_bytes   = [0] * ndrives
+        end_rd_iops    = [0] * ndrives
+        end_wr_bytes   = [0] * ndrives
+        end_wr_iops    = [0] * ndrives
+
+        # Read the stats before advancing the clock
+        for i in range(0, ndrives):
+            start_rd_bytes[i], start_rd_iops[i], start_wr_bytes[i], \
+                start_wr_iops[i] = self.blockstats('drive%d' % i)
 
         self.vm.qtest("clock_step %d" % ns)
-        end_rd_bytes, end_rd_iops, end_wr_bytes, end_wr_iops = self.blockstats('drive0')
-
-        rd_bytes = end_rd_bytes - start_rd_bytes
-        rd_iops = end_rd_iops - start_rd_iops
-        wr_bytes = end_wr_bytes - start_wr_bytes
-        wr_iops = end_wr_iops - start_wr_iops
 
-        self.assertTrue(check_limit(params['bps'], rd_bytes + wr_bytes))
-        self.assertTrue(check_limit(params['bps_rd'], rd_bytes))
-        self.assertTrue(check_limit(params['bps_wr'], wr_bytes))
-        self.assertTrue(check_limit(params['iops'], rd_iops + wr_iops))
-        self.assertTrue(check_limit(params['iops_rd'], rd_iops))
-        self.assertTrue(check_limit(params['iops_wr'], wr_iops))
+        # Read the stats after advancing the clock
+        for i in range(0, ndrives):
+            end_rd_bytes[i], end_rd_iops[i], end_wr_bytes[i], \
+                end_wr_iops[i] = self.blockstats('drive%d' % i)
+
+        # Check that the I/O is within the limits and evenly distributed
+        for i in range(0, ndrives):
+            rd_bytes = end_rd_bytes[i] - start_rd_bytes[i]
+            rd_iops = end_rd_iops[i] - start_rd_iops[i]
+            wr_bytes = end_wr_bytes[i] - start_wr_bytes[i]
+            wr_iops = end_wr_iops[i] - start_wr_iops[i]
+
+            self.assertTrue(check_limit(params['bps'], rd_bytes + wr_bytes))
+            self.assertTrue(check_limit(params['bps_rd'], rd_bytes))
+            self.assertTrue(check_limit(params['bps_wr'], wr_bytes))
+            self.assertTrue(check_limit(params['iops'], rd_iops + wr_iops))
+            self.assertTrue(check_limit(params['iops_rd'], rd_iops))
+            self.assertTrue(check_limit(params['iops_wr'], wr_iops))
 
     def test_all(self):
         params = {"bps": 4096,
@@ -101,11 +136,13 @@ class ThrottleTestCase(iotests.QMPTestCase):
                   "iops_rd": 10,
                   "iops_wr": 10,
                  }
-        # Pick each out of all possible params and test
-        for tk in params:
-            limits = dict([(k, 0) for k in params])
-            limits[tk] = params[tk]
-            self.do_test_throttle(5, limits)
+        # Repeat the test with different numbers of drives
+        for ndrives in range(1, self.max_drives + 1):
+            # Pick each out of all possible params and test
+            for tk in params:
+                limits = dict([(k, 0) for k in params])
+                limits[tk] = params[tk] * ndrives
+                self.do_test_throttle(ndrives, 5, limits)
 
 class ThrottleTestCoroutine(ThrottleTestCase):
     test_img = "null-co://"
diff --git a/tests/qemu-iotests/103 b/tests/qemu-iotests/103
index ccab551f63..fa9a3c1fc9 100755
--- a/tests/qemu-iotests/103
+++ b/tests/qemu-iotests/103
@@ -93,6 +93,16 @@ $QEMU_IO -c "open -o l2-cache-size=1M,refcount-cache-size=0.25M $TEST_IMG" \
          -c 'read -P 42 0 64k' \
     | _filter_qemu_io
 
+echo
+echo '=== Testing minimal L2 cache and COW ==='
+echo
+
+$QEMU_IMG snapshot -c foo "$TEST_IMG"
+# This requires a COW operation, which accesses two L2 tables simultaneously
+# (COW source and destination), so there must be enough space in the cache to
+# place both tables there (and qemu should not crash)
+$QEMU_IO -c "open -o cache-size=0 $TEST_IMG" -c 'write 0 64k' | _filter_qemu_io
+
 # success, all done
 echo '*** done'
 rm -f $seq.full
diff --git a/tests/qemu-iotests/103.out b/tests/qemu-iotests/103.out
index ee705b05f0..d05f49fdba 100644
--- a/tests/qemu-iotests/103.out
+++ b/tests/qemu-iotests/103.out
@@ -26,4 +26,9 @@ read 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+=== Testing minimal L2 cache and COW ===
+
+wrote 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 *** done
diff --git a/tests/qemu-iotests/119 b/tests/qemu-iotests/119
new file mode 100755
index 0000000000..9a11f1b921
--- /dev/null
+++ b/tests/qemu-iotests/119
@@ -0,0 +1,60 @@
+#!/bin/bash
+#
+# NBD test case for overriding BDRV_O_PROTOCOL by explicitly specifying
+# a driver
+#
+# Copyright (C) 2015 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=mreitz@redhat.com
+
+seq="$(basename $0)"
+echo "QA output created by $seq"
+
+here="$PWD"
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+	_cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt raw
+_supported_proto nbd
+_supported_os Linux
+
+_make_test_img 64M
+# This should not crash
+echo "{'execute': 'qmp_capabilities'}
+      {'execute': 'human-monitor-command',
+       'arguments': {'command-line': 'qemu-io drv \"read -P 0 0 64k\"'}}
+      {'execute': 'quit'}" \
+    | $QEMU -drive id=drv,if=none,file="$TEST_IMG",driver=nbd \
+            -qmp stdio -nodefaults \
+    | _filter_qmp | _filter_qemu_io
+
+# success, all done
+echo
+echo '*** done'
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/119.out b/tests/qemu-iotests/119.out
new file mode 100644
index 0000000000..58e7114e8b
--- /dev/null
+++ b/tests/qemu-iotests/119.out
@@ -0,0 +1,11 @@
+QA output created by 119
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+QMP_VERSION
+{"return": {}}
+read 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+{"return": ""}
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN"}
+
+*** done
diff --git a/tests/qemu-iotests/120 b/tests/qemu-iotests/120
new file mode 100755
index 0000000000..9f13078764
--- /dev/null
+++ b/tests/qemu-iotests/120
@@ -0,0 +1,65 @@
+#!/bin/bash
+#
+# Non-NBD test cases for overriding BDRV_O_PROTOCOL by explicitly
+# specifying a driver
+#
+# Copyright (C) 2015 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/>.
+#
+
+# creator
+owner=mreitz@redhat.com
+
+seq="$(basename $0)"
+echo "QA output created by $seq"
+
+here="$PWD"
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+	_cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt generic
+_supported_proto file
+_supported_os Linux
+
+_make_test_img 64M
+
+echo "{'execute': 'qmp_capabilities'}
+      {'execute': 'human-monitor-command',
+       'arguments': {'command-line': 'qemu-io drv \"write -P 42 0 64k\"'}}
+      {'execute': 'quit'}" \
+    | $QEMU -qmp stdio -nodefaults \
+            -drive id=drv,if=none,file="$TEST_IMG",driver=raw,file.driver=$IMGFMT \
+    | _filter_qmp | _filter_qemu_io
+$QEMU_IO -c 'read -P 42 0 64k' "$TEST_IMG" | _filter_qemu_io
+
+$QEMU_IO_PROG -c 'read -P 42 0 64k' \
+    "json:{'driver': 'raw', 'file': {'driver': '$IMGFMT', 'file': {'filename': '$TEST_IMG'}}}" \
+    | _filter_qemu_io
+
+# success, all done
+echo
+echo '*** done'
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/120.out b/tests/qemu-iotests/120.out
new file mode 100644
index 0000000000..9131b1bce9
--- /dev/null
+++ b/tests/qemu-iotests/120.out
@@ -0,0 +1,15 @@
+QA output created by 120
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+QMP_VERSION
+{"return": {}}
+wrote 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+{"return": ""}
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN"}
+read 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+*** done
diff --git a/tests/qemu-iotests/124 b/tests/qemu-iotests/124
index 3ee78cd1f1..8abce2f869 100644
--- a/tests/qemu-iotests/124
+++ b/tests/qemu-iotests/124
@@ -125,7 +125,7 @@ class TestIncrementalBackup(iotests.QMPTestCase):
 
         event = self.vm.event_wait(name="BLOCK_JOB_COMPLETED",
                                    match={'data': {'device': kwargs['device']}})
-        self.assertIsNotNone(event)
+        self.assertNotEqual(event, None)
 
         try:
             failure = self.dictpath(event, 'data/error')
diff --git a/tests/qemu-iotests/128 b/tests/qemu-iotests/128
index 249a865581..e2a0f2f890 100755
--- a/tests/qemu-iotests/128
+++ b/tests/qemu-iotests/128
@@ -29,6 +29,7 @@ tmp=/tmp/$$
 status=1	# failure is the default!
 
 devname="eiodev$$"
+sudo=""
 
 _setup_eiodev()
 {
@@ -37,6 +38,7 @@ _setup_eiodev()
 		echo "0 $((1024 * 1024 * 1024 / 512)) error" | \
 			$cmd dmsetup create "$devname" 2>/dev/null
 		if [ "$?" -eq 0 ]; then
+			sudo="$cmd"
 			return
 		fi
 	done
@@ -74,7 +76,7 @@ TEST_IMG="/dev/mapper/$devname"
 echo
 echo "== reading from error device =="
 # Opening image should succeed but the read operation should fail
-$QEMU_IO --format "$IMGFMT" --nocache -c "read 0 65536" "$TEST_IMG" | _filter_qemu_io
+$sudo $QEMU_IO --format "$IMGFMT" --nocache -c "read 0 65536" "$TEST_IMG" | _filter_qemu_io
 
 # success, all done
 echo "*** done"
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 0b817ca32d..4597fc11c0 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -121,6 +121,8 @@
 114 rw auto quick
 115 rw auto
 116 rw auto quick
+119 rw auto quick
+120 rw auto quick
 121 rw auto
 122 rw auto
 123 rw auto quick
diff --git a/tests/test-aio.c b/tests/test-aio.c
index 4b0cb45d31..a7cb5c9915 100644
--- a/tests/test-aio.c
+++ b/tests/test-aio.c
@@ -107,7 +107,6 @@ static void test_notify(void)
 
 typedef struct {
     QemuMutex start_lock;
-    EventNotifier notifier;
     bool thread_acquired;
 } AcquireTestData;
 
@@ -119,8 +118,6 @@ static void *test_acquire_thread(void *opaque)
     qemu_mutex_lock(&data->start_lock);
     qemu_mutex_unlock(&data->start_lock);
 
-    g_usleep(500000);
-    event_notifier_set(&data->notifier);
     aio_context_acquire(ctx);
     aio_context_release(ctx);
 
@@ -129,19 +126,20 @@ static void *test_acquire_thread(void *opaque)
     return NULL;
 }
 
-static void dummy_notifier_read(EventNotifier *n)
+static void dummy_notifier_read(EventNotifier *unused)
 {
-    event_notifier_test_and_clear(n);
+    g_assert(false); /* should never be invoked */
 }
 
 static void test_acquire(void)
 {
     QemuThread thread;
+    EventNotifier notifier;
     AcquireTestData data;
 
     /* Dummy event notifier ensures aio_poll() will block */
-    event_notifier_init(&data.notifier, false);
-    aio_set_event_notifier(ctx, &data.notifier, dummy_notifier_read);
+    event_notifier_init(&notifier, false);
+    aio_set_event_notifier(ctx, &notifier, dummy_notifier_read);
     g_assert(!aio_poll(ctx, false)); /* consume aio_notify() */
 
     qemu_mutex_init(&data.start_lock);
@@ -155,13 +153,12 @@ static void test_acquire(void)
     /* Block in aio_poll(), let other thread kick us and acquire context */
     aio_context_acquire(ctx);
     qemu_mutex_unlock(&data.start_lock); /* let the thread run */
-    g_assert(aio_poll(ctx, true));
-    g_assert(!data.thread_acquired);
+    g_assert(!aio_poll(ctx, true));
     aio_context_release(ctx);
 
     qemu_thread_join(&thread);
-    aio_set_event_notifier(ctx, &data.notifier, NULL);
-    event_notifier_cleanup(&data.notifier);
+    aio_set_event_notifier(ctx, &notifier, NULL);
+    event_notifier_cleanup(&notifier);
 
     g_assert(data.thread_acquired);
 }
diff --git a/tests/test-throttle.c b/tests/test-throttle.c
index d8ba415e43..016844546a 100644
--- a/tests/test-throttle.c
+++ b/tests/test-throttle.c
@@ -1,10 +1,12 @@
 /*
  * Throttle infrastructure tests
  *
- * Copyright Nodalink, SARL. 2013
+ * Copyright Nodalink, EURL. 2013-2014
+ * Copyright Igalia, S.L. 2015
  *
  * Authors:
- *  Benoît Canet     <benoit.canet@irqsave.net>
+ *  Benoît Canet     <benoit.canet@nodalink.com>
+ *  Alberto Garcia   <berto@igalia.com>
  *
  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  * See the COPYING.LIB file in the top-level directory.
@@ -15,11 +17,13 @@
 #include "block/aio.h"
 #include "qemu/throttle.h"
 #include "qemu/error-report.h"
+#include "block/throttle-groups.h"
 
 static AioContext     *ctx;
 static LeakyBucket    bkt;
 static ThrottleConfig cfg;
 static ThrottleState  ts;
+static ThrottleTimers tt;
 
 /* useful function */
 static bool double_cmp(double x, double y)
@@ -103,17 +107,19 @@ static void test_init(void)
 {
     int i;
 
-    /* fill the structure with crap */
+    /* fill the structures with crap */
     memset(&ts, 1, sizeof(ts));
+    memset(&tt, 1, sizeof(tt));
 
-    /* init the structure */
-    throttle_init(&ts, ctx, QEMU_CLOCK_VIRTUAL,
-                  read_timer_cb, write_timer_cb, &ts);
+    /* init structures */
+    throttle_init(&ts);
+    throttle_timers_init(&tt, ctx, QEMU_CLOCK_VIRTUAL,
+                         read_timer_cb, write_timer_cb, &ts);
 
     /* check initialized fields */
-    g_assert(ts.clock_type == QEMU_CLOCK_VIRTUAL);
-    g_assert(ts.timers[0]);
-    g_assert(ts.timers[1]);
+    g_assert(tt.clock_type == QEMU_CLOCK_VIRTUAL);
+    g_assert(tt.timers[0]);
+    g_assert(tt.timers[1]);
 
     /* check other fields where cleared */
     g_assert(!ts.previous_leak);
@@ -124,17 +130,18 @@ static void test_init(void)
         g_assert(!ts.cfg.buckets[i].level);
     }
 
-    throttle_destroy(&ts);
+    throttle_timers_destroy(&tt);
 }
 
 static void test_destroy(void)
 {
     int i;
-    throttle_init(&ts, ctx, QEMU_CLOCK_VIRTUAL,
-                  read_timer_cb, write_timer_cb, &ts);
-    throttle_destroy(&ts);
+    throttle_init(&ts);
+    throttle_timers_init(&tt, ctx, QEMU_CLOCK_VIRTUAL,
+                         read_timer_cb, write_timer_cb, &ts);
+    throttle_timers_destroy(&tt);
     for (i = 0; i < 2; i++) {
-        g_assert(!ts.timers[i]);
+        g_assert(!tt.timers[i]);
     }
 }
 
@@ -170,11 +177,12 @@ static void test_config_functions(void)
 
     orig_cfg.op_size = 1;
 
-    throttle_init(&ts, ctx, QEMU_CLOCK_VIRTUAL,
-                  read_timer_cb, write_timer_cb, &ts);
+    throttle_init(&ts);
+    throttle_timers_init(&tt, ctx, QEMU_CLOCK_VIRTUAL,
+                         read_timer_cb, write_timer_cb, &ts);
     /* structure reset by throttle_init previous_leak should be null */
     g_assert(!ts.previous_leak);
-    throttle_config(&ts, &orig_cfg);
+    throttle_config(&ts, &tt, &orig_cfg);
 
     /* has previous leak been initialized by throttle_config ? */
     g_assert(ts.previous_leak);
@@ -182,7 +190,7 @@ static void test_config_functions(void)
     /* get back the fixed configuration */
     throttle_get_config(&ts, &final_cfg);
 
-    throttle_destroy(&ts);
+    throttle_timers_destroy(&tt);
 
     g_assert(final_cfg.buckets[THROTTLE_BPS_TOTAL].avg == 153);
     g_assert(final_cfg.buckets[THROTTLE_BPS_READ].avg  == 56);
@@ -323,43 +331,47 @@ static void test_is_valid(void)
 
 static void test_have_timer(void)
 {
-    /* zero the structure */
+    /* zero structures */
     memset(&ts, 0, sizeof(ts));
+    memset(&tt, 0, sizeof(tt));
 
     /* no timer set should return false */
-    g_assert(!throttle_have_timer(&ts));
+    g_assert(!throttle_timers_are_initialized(&tt));
 
-    /* init the structure */
-    throttle_init(&ts, ctx, QEMU_CLOCK_VIRTUAL,
-                  read_timer_cb, write_timer_cb, &ts);
+    /* init structures */
+    throttle_init(&ts);
+    throttle_timers_init(&tt, ctx, QEMU_CLOCK_VIRTUAL,
+                         read_timer_cb, write_timer_cb, &ts);
 
     /* timer set by init should return true */
-    g_assert(throttle_have_timer(&ts));
+    g_assert(throttle_timers_are_initialized(&tt));
 
-    throttle_destroy(&ts);
+    throttle_timers_destroy(&tt);
 }
 
 static void test_detach_attach(void)
 {
-    /* zero the structure */
+    /* zero structures */
     memset(&ts, 0, sizeof(ts));
+    memset(&tt, 0, sizeof(tt));
 
     /* init the structure */
-    throttle_init(&ts, ctx, QEMU_CLOCK_VIRTUAL,
-                  read_timer_cb, write_timer_cb, &ts);
+    throttle_init(&ts);
+    throttle_timers_init(&tt, ctx, QEMU_CLOCK_VIRTUAL,
+                         read_timer_cb, write_timer_cb, &ts);
 
     /* timer set by init should return true */
-    g_assert(throttle_have_timer(&ts));
+    g_assert(throttle_timers_are_initialized(&tt));
 
     /* timer should no longer exist after detaching */
-    throttle_detach_aio_context(&ts);
-    g_assert(!throttle_have_timer(&ts));
+    throttle_timers_detach_aio_context(&tt);
+    g_assert(!throttle_timers_are_initialized(&tt));
 
     /* timer should exist again after attaching */
-    throttle_attach_aio_context(&ts, ctx);
-    g_assert(throttle_have_timer(&ts));
+    throttle_timers_attach_aio_context(&tt, ctx);
+    g_assert(throttle_timers_are_initialized(&tt));
 
-    throttle_destroy(&ts);
+    throttle_timers_destroy(&tt);
 }
 
 static bool do_test_accounting(bool is_ops, /* are we testing bps or ops */
@@ -387,9 +399,10 @@ static bool do_test_accounting(bool is_ops, /* are we testing bps or ops */
 
     cfg.op_size = op_size;
 
-    throttle_init(&ts, ctx, QEMU_CLOCK_VIRTUAL,
-                  read_timer_cb, write_timer_cb, &ts);
-    throttle_config(&ts, &cfg);
+    throttle_init(&ts);
+    throttle_timers_init(&tt, ctx, QEMU_CLOCK_VIRTUAL,
+                         read_timer_cb, write_timer_cb, &ts);
+    throttle_config(&ts, &tt, &cfg);
 
     /* account a read */
     throttle_account(&ts, false, size);
@@ -414,7 +427,7 @@ static bool do_test_accounting(bool is_ops, /* are we testing bps or ops */
         return false;
     }
 
-    throttle_destroy(&ts);
+    throttle_timers_destroy(&tt);
 
     return true;
 }
@@ -490,23 +503,80 @@ static void test_accounting(void)
                                 (64.0 / 13)));
 }
 
+static void test_groups(void)
+{
+    ThrottleConfig cfg1, cfg2;
+    BlockDriverState *bdrv1, *bdrv2, *bdrv3;
+
+    bdrv1 = bdrv_new();
+    bdrv2 = bdrv_new();
+    bdrv3 = bdrv_new();
+
+    g_assert(bdrv1->throttle_state == NULL);
+    g_assert(bdrv2->throttle_state == NULL);
+    g_assert(bdrv3->throttle_state == NULL);
+
+    throttle_group_register_bs(bdrv1, "bar");
+    throttle_group_register_bs(bdrv2, "foo");
+    throttle_group_register_bs(bdrv3, "bar");
+
+    g_assert(bdrv1->throttle_state != NULL);
+    g_assert(bdrv2->throttle_state != NULL);
+    g_assert(bdrv3->throttle_state != NULL);
+
+    g_assert(!strcmp(throttle_group_get_name(bdrv1), "bar"));
+    g_assert(!strcmp(throttle_group_get_name(bdrv2), "foo"));
+    g_assert(bdrv1->throttle_state == bdrv3->throttle_state);
+
+    /* Setting the config of a group member affects the whole group */
+    memset(&cfg1, 0, sizeof(cfg1));
+    cfg1.buckets[THROTTLE_BPS_READ].avg  = 500000;
+    cfg1.buckets[THROTTLE_BPS_WRITE].avg = 285000;
+    cfg1.buckets[THROTTLE_OPS_READ].avg  = 20000;
+    cfg1.buckets[THROTTLE_OPS_WRITE].avg = 12000;
+    throttle_group_config(bdrv1, &cfg1);
+
+    throttle_group_get_config(bdrv1, &cfg1);
+    throttle_group_get_config(bdrv3, &cfg2);
+    g_assert(!memcmp(&cfg1, &cfg2, sizeof(cfg1)));
+
+    cfg2.buckets[THROTTLE_BPS_READ].avg  = 4547;
+    cfg2.buckets[THROTTLE_BPS_WRITE].avg = 1349;
+    cfg2.buckets[THROTTLE_OPS_READ].avg  = 123;
+    cfg2.buckets[THROTTLE_OPS_WRITE].avg = 86;
+    throttle_group_config(bdrv3, &cfg1);
+
+    throttle_group_get_config(bdrv1, &cfg1);
+    throttle_group_get_config(bdrv3, &cfg2);
+    g_assert(!memcmp(&cfg1, &cfg2, sizeof(cfg1)));
+
+    throttle_group_unregister_bs(bdrv1);
+    throttle_group_unregister_bs(bdrv2);
+    throttle_group_unregister_bs(bdrv3);
+
+    g_assert(bdrv1->throttle_state == NULL);
+    g_assert(bdrv2->throttle_state == NULL);
+    g_assert(bdrv3->throttle_state == NULL);
+}
+
 int main(int argc, char **argv)
 {
-    GSource *src;
     Error *local_error = NULL;
 
-    init_clocks();
+    qemu_init_main_loop(&local_error);
+    ctx = qemu_get_aio_context();
 
-    ctx = aio_context_new(&local_error);
     if (!ctx) {
         error_report("Failed to create AIO Context: '%s'",
-                     error_get_pretty(local_error));
-        error_free(local_error);
+                     local_error ? error_get_pretty(local_error) :
+                     "Failed to initialize the QEMU main loop");
+        if (local_error) {
+            error_free(local_error);
+        }
         exit(1);
     }
-    src = aio_get_g_source(ctx);
-    g_source_attach(src, NULL);
-    g_source_unref(src);
+
+    bdrv_init();
 
     do {} while (g_main_context_iteration(NULL, false));
 
@@ -523,6 +593,7 @@ int main(int argc, char **argv)
     g_test_add_func("/throttle/config/is_valid",    test_is_valid);
     g_test_add_func("/throttle/config_functions",   test_config_functions);
     g_test_add_func("/throttle/accounting",         test_accounting);
+    g_test_add_func("/throttle/groups",             test_groups);
     return g_test_run();
 }
 
diff --git a/util/throttle.c b/util/throttle.c
index f976ac7de5..706c13111e 100644
--- a/util/throttle.c
+++ b/util/throttle.c
@@ -1,10 +1,12 @@
 /*
  * QEMU throttling infrastructure
  *
- * Copyright (C) Nodalink, SARL. 2013
+ * Copyright (C) Nodalink, EURL. 2013-2014
+ * Copyright (C) Igalia, S.L. 2015
  *
- * Author:
- *   Benoît Canet <benoit.canet@irqsave.net>
+ * Authors:
+ *   Benoît Canet <benoit.canet@nodalink.com>
+ *   Alberto Garcia <berto@igalia.com>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -159,29 +161,36 @@ bool throttle_compute_timer(ThrottleState *ts,
 }
 
 /* Add timers to event loop */
-void throttle_attach_aio_context(ThrottleState *ts, AioContext *new_context)
+void throttle_timers_attach_aio_context(ThrottleTimers *tt,
+                                        AioContext *new_context)
 {
-    ts->timers[0] = aio_timer_new(new_context, ts->clock_type, SCALE_NS,
-                                  ts->read_timer_cb, ts->timer_opaque);
-    ts->timers[1] = aio_timer_new(new_context, ts->clock_type, SCALE_NS,
-                                  ts->write_timer_cb, ts->timer_opaque);
+    tt->timers[0] = aio_timer_new(new_context, tt->clock_type, SCALE_NS,
+                                  tt->read_timer_cb, tt->timer_opaque);
+    tt->timers[1] = aio_timer_new(new_context, tt->clock_type, SCALE_NS,
+                                  tt->write_timer_cb, tt->timer_opaque);
 }
 
 /* To be called first on the ThrottleState */
-void throttle_init(ThrottleState *ts,
-                   AioContext *aio_context,
-                   QEMUClockType clock_type,
-                   QEMUTimerCB *read_timer_cb,
-                   QEMUTimerCB *write_timer_cb,
-                   void *timer_opaque)
+void throttle_init(ThrottleState *ts)
 {
     memset(ts, 0, sizeof(ThrottleState));
+}
+
+/* To be called first on the ThrottleTimers */
+void throttle_timers_init(ThrottleTimers *tt,
+                          AioContext *aio_context,
+                          QEMUClockType clock_type,
+                          QEMUTimerCB *read_timer_cb,
+                          QEMUTimerCB *write_timer_cb,
+                          void *timer_opaque)
+{
+    memset(tt, 0, sizeof(ThrottleTimers));
 
-    ts->clock_type = clock_type;
-    ts->read_timer_cb = read_timer_cb;
-    ts->write_timer_cb = write_timer_cb;
-    ts->timer_opaque = timer_opaque;
-    throttle_attach_aio_context(ts, aio_context);
+    tt->clock_type = clock_type;
+    tt->read_timer_cb = read_timer_cb;
+    tt->write_timer_cb = write_timer_cb;
+    tt->timer_opaque = timer_opaque;
+    throttle_timers_attach_aio_context(tt, aio_context);
 }
 
 /* destroy a timer */
@@ -195,25 +204,25 @@ static void throttle_timer_destroy(QEMUTimer **timer)
 }
 
 /* Remove timers from event loop */
-void throttle_detach_aio_context(ThrottleState *ts)
+void throttle_timers_detach_aio_context(ThrottleTimers *tt)
 {
     int i;
 
     for (i = 0; i < 2; i++) {
-        throttle_timer_destroy(&ts->timers[i]);
+        throttle_timer_destroy(&tt->timers[i]);
     }
 }
 
-/* To be called last on the ThrottleState */
-void throttle_destroy(ThrottleState *ts)
+/* To be called last on the ThrottleTimers */
+void throttle_timers_destroy(ThrottleTimers *tt)
 {
-    throttle_detach_aio_context(ts);
+    throttle_timers_detach_aio_context(tt);
 }
 
 /* is any throttling timer configured */
-bool throttle_have_timer(ThrottleState *ts)
+bool throttle_timers_are_initialized(ThrottleTimers *tt)
 {
-    if (ts->timers[0]) {
+    if (tt->timers[0]) {
         return true;
     }
 
@@ -324,9 +333,12 @@ static void throttle_cancel_timer(QEMUTimer *timer)
 /* Used to configure the throttle
  *
  * @ts: the throttle state we are working on
+ * @tt: the throttle timers we use in this aio context
  * @cfg: the config to set
  */
-void throttle_config(ThrottleState *ts, ThrottleConfig *cfg)
+void throttle_config(ThrottleState *ts,
+                     ThrottleTimers *tt,
+                     ThrottleConfig *cfg)
 {
     int i;
 
@@ -336,10 +348,10 @@ void throttle_config(ThrottleState *ts, ThrottleConfig *cfg)
         throttle_fix_bucket(&ts->cfg.buckets[i]);
     }
 
-    ts->previous_leak = qemu_clock_get_ns(ts->clock_type);
+    ts->previous_leak = qemu_clock_get_ns(tt->clock_type);
 
     for (i = 0; i < 2; i++) {
-        throttle_cancel_timer(ts->timers[i]);
+        throttle_cancel_timer(tt->timers[i]);
     }
 }
 
@@ -358,12 +370,15 @@ void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg)
  *
  * NOTE: this function is not unit tested due to it's usage of timer_mod
  *
+ * @tt:       the timers structure
  * @is_write: the type of operation (read/write)
  * @ret:      true if the timer has been scheduled else false
  */
-bool throttle_schedule_timer(ThrottleState *ts, bool is_write)
+bool throttle_schedule_timer(ThrottleState *ts,
+                             ThrottleTimers *tt,
+                             bool is_write)
 {
-    int64_t now = qemu_clock_get_ns(ts->clock_type);
+    int64_t now = qemu_clock_get_ns(tt->clock_type);
     int64_t next_timestamp;
     bool must_wait;
 
@@ -378,12 +393,12 @@ bool throttle_schedule_timer(ThrottleState *ts, bool is_write)
     }
 
     /* request throttled and timer pending -> do nothing */
-    if (timer_pending(ts->timers[is_write])) {
+    if (timer_pending(tt->timers[is_write])) {
         return true;
     }
 
     /* request throttled and timer not pending -> arm timer */
-    timer_mod(ts->timers[is_write], next_timestamp);
+    timer_mod(tt->timers[is_write], next_timestamp);
     return true;
 }