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

[Zhang Chen <zhangckid@gmail.com>]

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