Re: [PATCH v3 3/3] qapi: Allow introspecting fix for savevm's cooperation with blockdev

[Eric Blake <eblake@redhat.com>]

On 10/10/19 6:05 AM, Peter Krempa wrote:

In addition to Markus' review,

> 'savevm' was buggy as it considered all monitor-owned block device nodes
> for snapshot. With introduction of -blockdev the common usage made all

With the introduction of -blockdev, the common usage

> nodes including protocol and backing file nodes monitor-owned and thus

nodes be monitor-owned

> considered for snapshot.
> 
> This is a problem since the 'file' protocol nodes can't have internal
> snapshots and it does not make sense to take snapshot of nodes
> representing backing files.
> 
> This was fixed by commit 05f4aced658a02b02 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 | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/qapi/misc.json b/qapi/misc.json
> index 6bd11f50e6..5d0070aa43 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -1020,6 +1020,12 @@
>   #
>   # @cpu-index: The CPU to use for commands that require an implicit CPU
>   #
> +# Features:
> +# @savevm-blockdev-monitor-nodes: If present, the HMP command savevm only
> +#                                 snapshots monitor-owned nodes if they have no
> +#                                 parents. This allows to use 'savevm' with
> +#                                 -blockdev. (since 4.2)

s/to use/the use of/

> +#
>   # Returns: the output of the command as a string
>   #
>   # Since: 0.14.0
> @@ -1047,7 +1053,8 @@
>   ##
>   { 'command': 'human-monitor-command',
>     'data': {'command-line': 'str', '*cpu-index': 'int'},
> -  'returns': 'str' }
> +  'returns': 'str',
> +  'features': [ 'savevm-blockdev-monitor-nodes' ] }
> 
>   ##
>   # @change:
> 

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