Re: [Qemu-devel] [PATCH v9 08/21] migration: introduce icount field for snapshots

[Markus Armbruster <armbru@redhat.com>]

Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru> writes:

> Saving icount as a parameters of the snapshot allows navigation between
> them in the execution replay scenario.
> This information can be used for finding a specific snapshot for rewinding
> the recorded execution to the specific moment of the time.
> E.g., 'reverse step' action needs to load the nearest snapshot which is
> prior to the current moment of time .
>
> Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
>
> --
>
> v2:
>  - made icount in SnapshotInfo optional (suggested by Eric Blake)
> v7:
>  - added more comments for icount member (suggested by Markus Armbruster)
> v9:
>  - updated icount comment
> ---
[...]
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 762000f..a197e5f 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -26,13 +26,19 @@
>  #
>  # @vm-clock-nsec: fractional part in nano seconds to be used with vm-clock-sec
>  #
> +# @icount: Current instruction count. Appears when execution record/replay
> +#          is enabled. Used for "time-traveling" to match the moment
> +#          in the recorded execution with the snapshots. This counter may
> +#          be obtained through @query-replay command (since 4.0)

query-replay appears only in PATCH 11.  Please delay the last sentence
until then.

> +#
>  # Since: 1.3
>  #
>  ##
>  { 'struct': 'SnapshotInfo',
>    'data': { 'id': 'str', 'name': 'str', 'vm-state-size': 'int',
>              'date-sec': 'int', 'date-nsec': 'int',
> -            'vm-clock-sec': 'int', 'vm-clock-nsec': 'int' } }
> +            'vm-clock-sec': 'int', 'vm-clock-nsec': 'int',
> +            '*icount': 'int' } }
>  
>  ##
>  # @ImageInfoSpecificQCow2EncryptionBase:
> diff --git a/qapi/block.json b/qapi/block.json
> index 11f01f2..a6396a9 100644
> --- a/qapi/block.json
> +++ b/qapi/block.json
> @@ -176,7 +176,8 @@
>  #                    "date-sec": 1000012,
>  #                    "date-nsec": 10,
>  #                    "vm-clock-sec": 100,
> -#                    "vm-clock-nsec": 20
> +#                    "vm-clock-nsec": 20,
> +#                    "icount": 220414
>  #      }
>  #    }
>  #