[PATCH V2 1/4] qapi/misc: Fix missed query-iothreads items

[PATCH V2 1/4] qapi/misc: Fix missed query-iothreads items

[Zhang Chen]

The example is incomplete: it misses members @poll-max-ns, @poll-grow,
@poll-shrink, @aio-max-batch.  Messed up in commit 5fc00480ab1
(monitor: add poll-* properties into query-iothreads result) and
commit 1793ad0247c (iothread: add aio-max-batch parameter).

cc: qemu-stable@nongnu.org

Signed-off-by: Zhang Chen <zhangckid@gmail.com>
---
 qapi/misc.json | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/qapi/misc.json b/qapi/misc.json
index 28c641fe2f..e87994c9d9 100644
--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -117,11 +117,19 @@
 #     <- { "return": [
 #              {
 #                 "id":"iothread0",
-#                 "thread-id":3134
+#                 "thread-id":3134,
+#                 'poll-max-ns':32768,
+#                 "poll-grow":0,
+#                 "poll-shrink":0,
+#                 "aio-max-batch":0
 #              },
 #              {
 #                 "id":"iothread1",
-#                 "thread-id":3135
+#                 "thread-id":3135,
+#                 'poll-max-ns':32768,
+#                 "poll-grow":0,
+#                 "poll-shrink":0,
+#                 "aio-max-batch":0
 #              }
 #           ]
 #        }
-- 
2.49.0

[PATCH V2 2/4] iothread: Introduce a new flag to show iothreads attached status

[Zhang Chen]

QEMU Need a flag to show current iothread attached status
when hotplug multi iothreads. For example virtio-blk.

Signed-off-by: Zhang Chen <zhangckid@gmail.com>
---
 include/system/iothread.h | 1 +
 iothread.c                | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/include/system/iothread.h b/include/system/iothread.h
index e26d13c6c7..3d00474523 100644
--- a/include/system/iothread.h
+++ b/include/system/iothread.h
@@ -32,6 +32,7 @@ struct IOThread {
     QemuSemaphore init_done_sem; /* is thread init done? */
     bool stopping;              /* has iothread_stop() been called? */
     bool running;               /* should iothread_run() continue? */
+    bool attached;              /* Whether or not attached to device */
     int thread_id;
 
     /* AioContext poll parameters */
diff --git a/iothread.c b/iothread.c
index caf68e0764..38e38fb44d 100644
--- a/iothread.c
+++ b/iothread.c
@@ -94,6 +94,7 @@ void iothread_stop(IOThread *iothread)
         return;
     }
     iothread->stopping = true;
+    iothread->attached = false;
     aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread);
     qemu_thread_join(&iothread->thread);
 }
@@ -199,6 +200,9 @@ static void iothread_init(EventLoopBase *base, Error **errp)
      */
     iothread_init_gcontext(iothread, thread_name);
 
+    /* Clear iothread attached flag for init gcontext */
+    iothread->attached = false;
+
     iothread_set_aio_context_params(base, &local_error);
     if (local_error) {
         error_propagate(errp, local_error);
@@ -336,6 +340,7 @@ char *iothread_get_id(IOThread *iothread)
 
 AioContext *iothread_get_aio_context(IOThread *iothread)
 {
+    iothread->attached = true;
     return iothread->ctx;
 }
 
-- 
2.49.0

[PATCH V2 3/4] qapi: Add attached flag for iothread

[Zhang Chen]

The attached flag depends on struct IOThreadInfo's
'attached': 'bool'. It can show whether the iothread
is attached to an actual device. Show in the qmp/hmp
CMD with "attached": true/false.

Signed-off-by: Zhang Chen <zhangckid@gmail.com>
---
 iothread.c         | 1 +
 monitor/hmp-cmds.c | 2 ++
 qapi/misc.json     | 6 ++++++
 3 files changed, 9 insertions(+)

diff --git a/iothread.c b/iothread.c
index 38e38fb44d..fb4898e491 100644
--- a/iothread.c
+++ b/iothread.c
@@ -358,6 +358,7 @@ static int query_one_iothread(Object *object, void *opaque)
     info = g_new0(IOThreadInfo, 1);
     info->id = iothread_get_id(iothread);
     info->thread_id = iothread->thread_id;
+    info->attached = iothread->attached;
     info->poll_max_ns = iothread->poll_max_ns;
     info->poll_grow = iothread->poll_grow;
     info->poll_shrink = iothread->poll_shrink;
diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index 5a673cddb2..7463f34bf5 100644
--- a/monitor/hmp-cmds.c
+++ b/monitor/hmp-cmds.c
@@ -202,6 +202,8 @@ void hmp_info_iothreads(Monitor *mon, const QDict *qdict)
         value = info->value;
         monitor_printf(mon, "%s:\n", value->id);
         monitor_printf(mon, "  thread_id=%" PRId64 "\n", value->thread_id);
+        monitor_printf(mon, "  attached=%s" "\n",
+                       value->attached ? "true" : "false");
         monitor_printf(mon, "  poll-max-ns=%" PRId64 "\n", value->poll_max_ns);
         monitor_printf(mon, "  poll-grow=%" PRId64 "\n", value->poll_grow);
         monitor_printf(mon, "  poll-shrink=%" PRId64 "\n", value->poll_shrink);
diff --git a/qapi/misc.json b/qapi/misc.json
index e87994c9d9..99ffd45ce5 100644
--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -76,6 +76,9 @@
 #
 # @thread-id: ID of the underlying host thread
 #
+# @attached: flag to show current iothread attach to device status
+#     (since 12.0)
+#
 # @poll-max-ns: maximum polling time in ns, 0 means polling is
 #     disabled (since 2.9)
 #
@@ -93,6 +96,7 @@
 { 'struct': 'IOThreadInfo',
   'data': {'id': 'str',
            'thread-id': 'int',
+           'attached': 'bool',
            'poll-max-ns': 'int',
            'poll-grow': 'int',
            'poll-shrink': 'int',
@@ -118,6 +122,7 @@
 #              {
 #                 "id":"iothread0",
 #                 "thread-id":3134,
+#                 "attached":false",
 #                 'poll-max-ns':32768,
 #                 "poll-grow":0,
 #                 "poll-shrink":0,
@@ -126,6 +131,7 @@
 #              {
 #                 "id":"iothread1",
 #                 "thread-id":3135,
+#                 "attached":true",
 #                 'poll-max-ns':32768,
 #                 "poll-grow":0,
 #                 "poll-shrink":0,
-- 
2.49.0

[PATCH V2 4/4] qemu-options: Introduce new flag for iothread

[Zhang Chen]

This demand comes from Cloud Native ecosystem.
User want to manage resources more flexible like containers (Kata container).
The real workload maybe changed(runc) in the VM without VM reboot,
It may need hotplug/unplug different multi disks with multi iothreads to meet
high level scheduler's needs(like K8s).

Signed-off-by: Zhang Chen <zhangckid@gmail.com>
---
 qemu-options.hx | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/qemu-options.hx b/qemu-options.hx
index ec92723f10..9afe9d4ebb 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -6352,7 +6352,7 @@ SRST
 
             CN=laptop.example.com,O=Example Home,L=London,ST=London,C=GB
 
-    ``-object iothread,id=id,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink,aio-max-batch=aio-max-batch``
+    ``-object iothread,id=id,attached=attached,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink,aio-max-batch=aio-max-batch``
         Creates a dedicated event loop thread that devices can be
         assigned to. This is known as an IOThread. By default device
         emulation happens in vCPU threads or the main event loop thread.
@@ -6376,6 +6376,13 @@ SRST
         for many cases but can be adjusted based on knowledge of the
         workload and/or host device latency.
 
+        The ``attached`` parameter is a flag to show whether the iothread
+        is attached to an actual device(for example virtio-blk). In hotplug
+        scenario, user can add multiple "-object iothread" and multiple
+        devices (like virtio-blk). When user hotunplug the devices can keep
+        the iothreads as a thread pool, following the new hotplug devices can
+        attach to the released iothread.
+
         The ``poll-max-ns`` parameter is the maximum number of
         nanoseconds to busy wait for events. Polling can be disabled by
         setting this value to 0.
-- 
2.49.0

Re: [PATCH V2 1/4] qapi/misc: Fix missed query-iothreads items

[Markus Armbruster]

Zhang Chen <zhangckid@gmail.com> writes:

> The example is incomplete: it misses members @poll-max-ns, @poll-grow,
> @poll-shrink, @aio-max-batch.  Messed up in commit 5fc00480ab1
> (monitor: add poll-* properties into query-iothreads result) and
> commit 1793ad0247c (iothread: add aio-max-batch parameter).
>
> cc: qemu-stable@nongnu.org
>
> Signed-off-by: Zhang Chen <zhangckid@gmail.com>
> ---
>  qapi/misc.json | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/qapi/misc.json b/qapi/misc.json
> index 28c641fe2f..e87994c9d9 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -117,11 +117,19 @@
>  #     <- { "return": [
>  #              {
>  #                 "id":"iothread0",
> -#                 "thread-id":3134
> +#                 "thread-id":3134,
> +#                 'poll-max-ns':32768,

Double quotes, please.

> +#                 "poll-grow":0,
> +#                 "poll-shrink":0,
> +#                 "aio-max-batch":0
>  #              },
>  #              {
>  #                 "id":"iothread1",
> -#                 "thread-id":3135
> +#                 "thread-id":3135,
> +#                 'poll-max-ns':32768,

Likewise.

> +#                 "poll-grow":0,
> +#                 "poll-shrink":0,
> +#                 "aio-max-batch":0
>  #              }
>  #           ]
>  #        }

Easiest way to avoid such mistakes is to copy actual QMP output.

Re: [PATCH V2 3/4] qapi: Add attached flag for iothread

[Markus Armbruster]

Zhang Chen <zhangckid@gmail.com> writes:

> The attached flag depends on struct IOThreadInfo's
> 'attached': 'bool'. It can show whether the iothread
> is attached to an actual device. Show in the qmp/hmp
> CMD with "attached": true/false.
>
> Signed-off-by: Zhang Chen <zhangckid@gmail.com>
> ---
>  iothread.c         | 1 +
>  monitor/hmp-cmds.c | 2 ++
>  qapi/misc.json     | 6 ++++++
>  3 files changed, 9 insertions(+)
>
> diff --git a/iothread.c b/iothread.c
> index 38e38fb44d..fb4898e491 100644
> --- a/iothread.c
> +++ b/iothread.c
> @@ -358,6 +358,7 @@ static int query_one_iothread(Object *object, void *opaque)
>      info = g_new0(IOThreadInfo, 1);
>      info->id = iothread_get_id(iothread);
>      info->thread_id = iothread->thread_id;
> +    info->attached = iothread->attached;
>      info->poll_max_ns = iothread->poll_max_ns;
>      info->poll_grow = iothread->poll_grow;
>      info->poll_shrink = iothread->poll_shrink;
> diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
> index 5a673cddb2..7463f34bf5 100644
> --- a/monitor/hmp-cmds.c
> +++ b/monitor/hmp-cmds.c
> @@ -202,6 +202,8 @@ void hmp_info_iothreads(Monitor *mon, const QDict *qdict)
>          value = info->value;
>          monitor_printf(mon, "%s:\n", value->id);
>          monitor_printf(mon, "  thread_id=%" PRId64 "\n", value->thread_id);
> +        monitor_printf(mon, "  attached=%s" "\n",
> +                       value->attached ? "true" : "false");
>          monitor_printf(mon, "  poll-max-ns=%" PRId64 "\n", value->poll_max_ns);
>          monitor_printf(mon, "  poll-grow=%" PRId64 "\n", value->poll_grow);
>          monitor_printf(mon, "  poll-shrink=%" PRId64 "\n", value->poll_shrink);
> diff --git a/qapi/misc.json b/qapi/misc.json
> index e87994c9d9..99ffd45ce5 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -76,6 +76,9 @@
>  #
>  # @thread-id: ID of the underlying host thread
>  #
> +# @attached: flag to show current iothread attach to device status
> +#     (since 12.0)

We started to talk about improving the description in review of v1.
Let's continue there.

> +#
>  # @poll-max-ns: maximum polling time in ns, 0 means polling is
>  #     disabled (since 2.9)
>  #
> @@ -93,6 +96,7 @@
>  { 'struct': 'IOThreadInfo',
>    'data': {'id': 'str',
>             'thread-id': 'int',
> +           'attached': 'bool',
>             'poll-max-ns': 'int',
>             'poll-grow': 'int',
>             'poll-shrink': 'int',
> @@ -118,6 +122,7 @@
>  #              {
>  #                 "id":"iothread0",
>  #                 "thread-id":3134,
> +#                 "attached":false",

Invalid JSON.  Drop the last ".

>  #                 'poll-max-ns':32768,
>  #                 "poll-grow":0,
>  #                 "poll-shrink":0,
> @@ -126,6 +131,7 @@
>  #              {
>  #                 "id":"iothread1",
>  #                 "thread-id":3135,
> +#                 "attached":true",

Likewise.

>  #                 'poll-max-ns':32768,
>  #                 "poll-grow":0,
>  #                 "poll-shrink":0,

Re: [PATCH V2 4/4] qemu-options: Introduce new flag for iothread

[Markus Armbruster]

Zhang Chen <zhangckid@gmail.com> writes:

> This demand comes from Cloud Native ecosystem.
> User want to manage resources more flexible like containers (Kata container).
> The real workload maybe changed(runc) in the VM without VM reboot,
> It may need hotplug/unplug different multi disks with multi iothreads to meet
> high level scheduler's needs(like K8s).
>
> Signed-off-by: Zhang Chen <zhangckid@gmail.com>
> ---
>  qemu-options.hx | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/qemu-options.hx b/qemu-options.hx
> index ec92723f10..9afe9d4ebb 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -6352,7 +6352,7 @@ SRST
>  
>              CN=laptop.example.com,O=Example Home,L=London,ST=London,C=GB
>  
> -    ``-object iothread,id=id,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink,aio-max-batch=aio-max-batch``
> +    ``-object iothread,id=id,attached=attached,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink,aio-max-batch=aio-max-batch``
>          Creates a dedicated event loop thread that devices can be
>          assigned to. This is known as an IOThread. By default device
>          emulation happens in vCPU threads or the main event loop thread.
> @@ -6376,6 +6376,13 @@ SRST
>          for many cases but can be adjusted based on knowledge of the
>          workload and/or host device latency.
>  
> +        The ``attached`` parameter is a flag to show whether the iothread
> +        is attached to an actual device(for example virtio-blk). In hotplug
> +        scenario, user can add multiple "-object iothread" and multiple
> +        devices (like virtio-blk). When user hotunplug the devices can keep
> +        the iothreads as a thread pool, following the new hotplug devices can
> +        attach to the released iothread.
> +
>          The ``poll-max-ns`` parameter is the maximum number of
>          nanoseconds to busy wait for events. Polling can be disabled by
>          setting this value to 0.

You're documenting something that does not exist:

    $ qemu-system-aarch64 -object iothread,id=iot0,attached=off
    upstream-qemu: -object iothread,id=iot0,attached=off: Invalid parameter 'attached'

The properties of iothread objects are defined in type
IothreadProperties in qapi/qom.json.

Re: [PATCH V2 1/4] qapi/misc: Fix missed query-iothreads items

[Zhang Chen]

[-- Attachment #1: Type: text/plain, Size: 1741 bytes --]

On Fri, Jan 23, 2026, 8:51 PM Markus Armbruster <armbru@redhat.com> wrote:

> Zhang Chen <zhangckid@gmail.com> writes:
>
> > The example is incomplete: it misses members @poll-max-ns, @poll-grow,
> > @poll-shrink, @aio-max-batch.  Messed up in commit 5fc00480ab1
> > (monitor: add poll-* properties into query-iothreads result) and
> > commit 1793ad0247c (iothread: add aio-max-batch parameter).
> >
> > cc: qemu-stable@nongnu.org
> >
> > Signed-off-by: Zhang Chen <zhangckid@gmail.com>
> > ---
> >  qapi/misc.json | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/qapi/misc.json b/qapi/misc.json
> > index 28c641fe2f..e87994c9d9 100644
> > --- a/qapi/misc.json
> > +++ b/qapi/misc.json
> > @@ -117,11 +117,19 @@
> >  #     <- { "return": [
> >  #              {
> >  #                 "id":"iothread0",
> > -#                 "thread-id":3134
> > +#                 "thread-id":3134,
> > +#                 'poll-max-ns':32768,
>
> Double quotes, please.
>
> > +#                 "poll-grow":0,
> > +#                 "poll-shrink":0,
> > +#                 "aio-max-batch":0
> >  #              },
> >  #              {
> >  #                 "id":"iothread1",
> > -#                 "thread-id":3135
> > +#                 "thread-id":3135,
> > +#                 'poll-max-ns':32768,
>
> Likewise.
>
> > +#                 "poll-grow":0,
> > +#                 "poll-shrink":0,
> > +#                 "aio-max-batch":0
> >  #              }
> >  #           ]
> >  #        }
>
> Easiest way to avoid such mistakes is to copy actual QMP output.
>

Oh, sorry to typo for this series... Will fix it with double check.

Thanks
Chen


>

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