Re: [PATCH i-g-t 03/10] tools/vmtb: Fix VM snapshot query handling

["Bernatowicz, Marcin" <marcin.bernatowicz@linux.intel.com>]

On 2/24/2026 8:50 AM, Adam Miszczak wrote:
> QMP command 'query-named-block-nodes' is used to select a block device
> for saving VM snapshot (QMP 'snapshot-save').
>
> Add polling for the command's return message in QMP response queue.
> It sporadically happened that unsolicited QMP message like:
> [QMP RSP] <- {"timestamp": {...}, "event": "RTC_CHANGE" ...}
> was falsely taken as a response to previously submitted
> QMP 'query-named-block-nodes' command.
> Hence, no 'block device node' argument is passed to
> 'snapshot-load' command which leads to migration tests fail.
> Also, add a condition to check if a given block node
> is writable (not read-only).
>
> Signed-off-by: Adam Miszczak <adam.miszczak@linux.intel.com>
> ---
>   .../machines/virtual/backends/qmp_monitor.py  | 25 ++++++++++---------
>   1 file changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/tools/vmtb/bench/machines/virtual/backends/qmp_monitor.py b/tools/vmtb/bench/machines/virtual/backends/qmp_monitor.py
> index ef3c8aa1c..d364a5711 100644
> --- a/tools/vmtb/bench/machines/virtual/backends/qmp_monitor.py
> +++ b/tools/vmtb/bench/machines/virtual/backends/qmp_monitor.py
> @@ -1,5 +1,5 @@
>   # SPDX-License-Identifier: MIT
> -# Copyright © 2024 Intel Corporation
> +# Copyright © 2024-2026 Intel Corporation
>   
>   import json
>   import logging
> @@ -123,17 +123,18 @@ class QmpMonitor():
>           ret: typing.Dict = {}
>   
>           qmp_msg = self.qmp_queue.get()
> -        # logger.debug('[QMP RSP Queue] -> %s', qmp_msg)
> -        if 'return' in qmp_msg:
> -            ret = qmp_msg.get('return')
> -            for block in ret:
> -                if block.get('drv') == 'qcow2':
> -                    node_name = block.get('node-name')
> -                    # Get the most recent state snapshot from the snapshots list:
> -                    snapshots = block.get('image').get('snapshots')
> -                    if snapshots:
> -                        snapshot_tag = snapshots[-1].get('name')
> -                    break
> +        while 'return' not in qmp_msg:
> +            qmp_msg = self.qmp_queue.get()
> +
> +        ret = qmp_msg.get('return')
> +        for block in ret:
> +            if block.get('drv') == 'qcow2' and block.get('ro') is False:
> +                node_name = block.get('node-name')
> +                # Get the most recent state snapshot from the snapshots list:
> +                snapshots = block.get('image').get('snapshots')
> +                if snapshots:
> +                    snapshot_tag = snapshots[-1].get('name')
> +                break
LGTM,
Reviewed-by: Marcin Bernatowicz <marcin.bernatowicz@linux.intel.com>
>   
>           return (node_name, snapshot_tag)
>