Re: [Xen-devel] [PATCH v8 --for 4.6 COLO 02/25] docs/libxl: Introduce COLO_CONTEXT to support migration v2 colo streams

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/07/15 07:32, Yang Hongyang wrote:
>
>
> On 07/16/2015 12:52 AM, Andrew Cooper wrote:
>> On 15/07/15 10:18, Yang Hongyang wrote:
>>> From: Wen Congyang <wency@xxxxxxxxxxxxxx>
>>>
>>> It is the negotiation record for COLO.
>>> Primary->Secondary:
>>> control_id      0x00000000: Secondary VM is out of sync, start a new
>>> checkpoint
>>> Secondary->Primary:
>>>                  0x00000001: Secondary VM is suspended
>>>                  0x00000002: Secondary VM is ready
>>>                  0x00000003: Secondary VM is resumed
>>>
>>> Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
>>> Signed-off-by: Yang Hongyang <yanghy@xxxxxxxxxxxxxx>
>>> ---
>>>   docs/specs/libxl-migration-stream.pandoc | 22 +++++++++++++++++++++-
>>>   tools/libxl/libxl_sr_stream_format.h     | 11 +++++++++++
>>>   tools/python/xen/migration/libxl.py      |  9 +++++++++
>>>   3 files changed, 41 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/docs/specs/libxl-migration-stream.pandoc
>>> b/docs/specs/libxl-migration-stream.pandoc
>>> index c24a434..5986273 100644
>>> --- a/docs/specs/libxl-migration-stream.pandoc
>>> +++ b/docs/specs/libxl-migration-stream.pandoc
>>> @@ -121,7 +121,9 @@ type         0x00000000: END
>>>
>>>                0x00000004: CHECKPOINT_END
>>>
>>> -             0x00000005 - 0x7FFFFFFF: Reserved for future _mandatory_
>>> +             0x00000005: COLO_CONTEXT
>>> +
>>> +             0x00000006 - 0x7FFFFFFF: Reserved for future _mandatory_
>>>                records.
>>>
>>>                0x80000000 - 0xFFFFFFFF: Reserved for future _optional_
>>> @@ -215,3 +217,21 @@ A checkpoint end record marks the end of a
>>> checkpoint in the image.
>>>       +-------------------------------------------------+
>>>
>>>   The end record contains no fields; its body_length is 0.
>>> +
>>> +COLO\_CONTEXT
>>> +--------------
>>> +
>>> +A COLO context record contains the control information for COLO.
>>> +
>>> +     0     1     2     3     4     5     6     7 octet
>>> +    +------------------------+------------------------+
>>> +    | control_id             | padding                |
>>> +    +------------------------+------------------------+
>>> +
>>> +--------------------------------------------------------------------
>>> +Field            Description
>>> +------------     ---------------------------------------------------
>>> +control_id       0x00000000: Secondary VM is out of sync, start a
>>> new checkpoint
>>> +                 0x00000001: Secondary VM is suspended
>>> +                 0x00000002: Secondary VM is ready
>>> +                 0x00000003: Secondary VM is resumed
>>
>> This style of table in pandoc need to be terminated with a line of
>> -------, just like the head of the table.
>
> Ok
>
>>
>> Also, I wonder at the name "COLO_CONTEXT".  CONTEXT implies an
>> associated blob of data, but this is not the case here.  Here, it is
>> more of a status update, with expected actions on some states.
>
> True, could you suggest a better name? sorry for my bad English...

In hindsight, I would also avoid putting COLO in the name.

How about CHECKPOINT_SECONDARY_STATE ?

You also want to note that this record should currently only be found in
the libxl backchannel.

~Andrew

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