Re: [Xen-devel] [PATCH v9 02/25] docs/libxl: Introduce COLO_CONTEXT to support migration v2 colo streams

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 27/01/16 15:28, Konrad Rzeszutek Wilk wrote:
> On Wed, Jan 27, 2016 at 03:15:47PM +0000, Andrew Cooper wrote:
>> On 27/01/16 15:11, Konrad Rzeszutek Wilk wrote:
>>> On Wed, Jan 27, 2016 at 11:00:24AM +0000, Andrew Cooper wrote:
>>>> On 27/01/16 06:47, Wen Congyang wrote:
>>>>> On 01/27/2016 04:40 AM, Konrad Rzeszutek Wilk wrote:
>>>>>> On Wed, Dec 30, 2015 at 10:37:32AM +0800, Wen Congyang wrote:
>>>>>>> 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 <hongyang.yang@xxxxxxxxxxxx>
>>>>>>> ---
>>>>>>>  docs/specs/libxl-migration-stream.pandoc | 25 +++++++++++++++++++++++--
>>>>>>>  tools/libxl/libxl_sr_stream_format.h     | 11 +++++++++++
>>>>>>>  tools/python/xen/migration/libxl.py      |  9 +++++++++
>>>>>>>  3 files changed, 43 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/docs/specs/libxl-migration-stream.pandoc 
>>>>>>> b/docs/specs/libxl-migration-stream.pandoc
>>>>>>> index 2c97d86..5166d66 100644
>>>>>>> --- a/docs/specs/libxl-migration-stream.pandoc
>>>>>>> +++ b/docs/specs/libxl-migration-stream.pandoc
>>>>>>> @@ -1,6 +1,6 @@
>>>>>>>  % LibXenLight Domain Image Format
>>>>>>>  % Andrew Cooper <<andrew.cooper3@xxxxxxxxxx>>
>>>>>>> -% Revision 1
>>>>>>> +% Revision 2
>>>>>>>  
>>>>>>>  Introduction
>>>>>>>  ============
>>>>>>> @@ -119,7 +119,9 @@ type         0x00000000: END
>>>>>>>  
>>>>>>>               0x00000004: CHECKPOINT_END
>>>>>>>  
>>>>>>> -             0x00000005 - 0x7FFFFFFF: Reserved for future _mandatory_
>>>>>>> +             0x00000005: CHECKPOINT_STATE
>>>>>>> +
>>>>>>> +             0x00000006 - 0x7FFFFFFF: Reserved for future _mandatory_
>>>>>> This is in the 'mandatory' records. Should it be part of optional 
>>>>>> records?
>>>>>>
>>>>>> Would this checkpoint state always present on non-COLO guest migration?
>>>>> No. Will be fixed in the next version
>>>> It is correct that CHECKPOINT_STATE is a mandatory record.
>>>>
>>>> Optional records which are free for the receiving end to ignore if they
>>>> are not understood.
>>> What you are saying is that the receving end has to expect this 
>>> (CHECKPOINT_STATE)
>>> even there is nothing in them - as the size of them is zero (becuase there 
>>> are
>>> no  dirty PFNs to send).
>> The sole difference between a mandatory record an an option record is
>> the receivers behaviour.
>>
>> Mandatory records may not be ignored, and constitutes a hard error. 
>> Optional records may be ignored, without error, if they are not understood.
> You are still not answering my question.
>
> Is it a hard error if the mandatory record is zero length?

Not if the type specifies that a zero length record is permitted.

~Andrew

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel