Re: [Qemu-devel] [RFC PATCH 06/17] migration: introduce icount field for snapshots

[Eric Blake]

On 04/25/2018 07:46 AM, Pavel Dovgalyuk wrote:
> 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 <address@hidden>
> ---
>  block/qapi.c             |   11 +++++++----
>  blockdev.c               |    3 +++
>  include/block/snapshot.h |    1 +
>  migration/savevm.c       |    1 +
>  qapi/block-core.json     |    5 ++++-
>  qapi/block.json          |    3 ++-
>  6 files changed, 18 insertions(+), 6 deletions(-)

Using scripts/git.orderfile may make your patches easier to review, by
hoisting interfaces above implementation.

> +++ b/qapi/block-core.json
> @@ -25,13 +25,16 @@
>  #
>  # @vm-clock-nsec: fractional part in nano seconds to be used with 
> vm-clock-sec
>  #
> +# @icount: current instruction count for execution record/replay

Missing a '(since 2.13)' tag.

> +#
>  # 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' } }

'icount' should be optional, as older qcow2 images will not have that
information available.  Also, putting patch 7 before this patch may make
more sense.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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