Re: [Qemu-devel] [PATCH 2/2] qapi: Allow introspecting fix for savevm's cooperation with blockdev

[Eric Blake <eblake@redhat.com>]

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On 9/17/19 10:49 AM, Peter Krempa wrote:
> savevm was buggy as it considered all monitor owned block device nodes
> for snapshot. With introduction of -blockdev the common usage made all
> nodes including protocol nodes monitor owned and thus considered for
> snapshot. This was fixed but clients need to be able to detect whether
> this fix is present.
> 
> Since savevm does not have an QMP alternative add the feature for the
> 'human-monitor-command' backdoor which is used to call this command in
> modern use.
> 
> Signed-off-by: Peter Krempa <pkrempa@redhat.com>
> ---
>  qapi/misc.json | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/qapi/misc.json b/qapi/misc.json
> index 6bd11f50e6..e2b33c3f8a 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -1020,6 +1020,11 @@
>  #
>  # @cpu-index: The CPU to use for commands that require an implicit CPU
>  #
> +# Features:
> +# @savevm-blockdev-monitor-nodes: If present, the savevm monitor command
> +#                                 correctly handles monitor owned block nodes
> +#                                 when taking a snapshot.

Is it worth adding a '(since 4.2)' on when features are added?

> +#
>  # Returns: the output of the command as a string
>  #
>  # Since: 0.14.0
> @@ -1047,7 +1052,8 @@
>  ##
>  { 'command': 'human-monitor-command',
>    'data': {'command-line': 'str', '*cpu-index': 'int'},
> -  'returns': 'str' }
> +  'returns': 'str',
> +  'features' : [ { 'name': 'savevm-blockdev-monitor-nodes' } ] }

We could, of course, actually implement a QMP 'savevm' and use _that_ as
the introspection.  But that's a bigger can of worms, so this is
reasonable enough for the 4.2 timeframe.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org


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