Re: [Qemu-devel] [PATCH] migration: fix analyze-migration.py script

[Alexander Graf]

On 26.11.15 16:31, Dr. David Alan Gilbert wrote:
> * Alexander Graf (address@hidden) wrote:
>>
>>
>> On 30.10.15 17:50, Mark Cave-Ayland wrote:
>>> On 26/10/15 09:48, Mark Cave-Ayland wrote:
>>>
>>>> On 06/09/15 12:54, Mark Cave-Ayland wrote:
>>>>
>>>>> On 06/09/15 09:36, Alexander Graf wrote:
>>>>>
>>>>>> On 05.09.15 21:51, Mark Cave-Ayland wrote:
>>>>>>> Commit 61964 "Add configuration section" broke the analyze-migration.py 
>>>>>>> script
>>>>>>> which terminates due to the unrecognised section. Fix the script by 
>>>>>>> parsing
>>>>>>> the contents of the configuration section directly into a new
>>>>>>> ConfigurationSection object (although nothing is done with it yet).
>>>>>>>
>>>>>>> Signed-off-by: Mark Cave-Ayland <address@hidden>
>>>>>>> ---
>>>>>>>  scripts/analyze-migration.py |   13 +++++++++++++
>>>>>>>  1 file changed, 13 insertions(+)
>>>>>>>
>>>>>>> diff --git a/scripts/analyze-migration.py b/scripts/analyze-migration.py
>>>>>>> index f6894be..1455387 100755
>>>>>>> --- a/scripts/analyze-migration.py
>>>>>>> +++ b/scripts/analyze-migration.py
>>>>>>> @@ -252,6 +252,15 @@ class HTABSection(object):
>>>>>>>      def getDict(self):
>>>>>>>          return ""
>>>>>>>  
>>>>>>> +
>>>>>>> +class ConfigurationSection(object):
>>>>>>> +    def __init__(self, file):
>>>>>>> +        self.file = file
>>>>>>> +
>>>>>>> +    def read(self):
>>>>>>> +        name_len = self.file.read32()
>>>>>>> +        name = self.file.readstr(len = name_len)
>>>>>>> +
>>>>>>>  class VMSDFieldGeneric(object):
>>>>>>>      def __init__(self, desc, file):
>>>>>>>          self.file = file
>>>>>>> @@ -474,6 +483,7 @@ class MigrationDump(object):
>>>>>>>      QEMU_VM_SECTION_FULL  = 0x04
>>>>>>>      QEMU_VM_SUBSECTION    = 0x05
>>>>>>>      QEMU_VM_VMDESCRIPTION = 0x06
>>>>>>> +    QEMU_VM_CONFIGURATION = 0x07
>>>>>>>      QEMU_VM_SECTION_FOOTER= 0x7e
>>>>>>>  
>>>>>>>      def __init__(self, filename):
>>>>>>> @@ -514,6 +524,9 @@ class MigrationDump(object):
>>>>>>>              section_type = file.read8()
>>>>>>>              if section_type == self.QEMU_VM_EOF:
>>>>>>>                  break
>>>>>>> +            elif section_type == self.QEMU_VM_CONFIGURATION:
>>>>>>> +                section = ConfigurationSection(file)
>>>>>>> +                section.read()
>>>>>>
>>>>>> So since we don't have a normal section header, there is no version
>>>>>> field either. That in turn means that the format is determined by the
>>>>>> machine version only - bleks.
>>>>>
>>>>> Yes :(  I double-checked the output of a migration file with hexdump and
>>>>> confirmed that just the raw fields are included without any additional
>>>>> metadata, even though the state is held in a VMStateDescription.
>>>>>
>>>>>> So if there ever has to be more in the configuration section than the
>>>>>> machine name, please move to a more detectable scheme. Ideally something
>>>>>> that contains
>>>>>>
>>>>>>   * version
>>>>>>   * length of dynamically sized fields
>>>>>>   * lenght of full blob
>>>>>>
>>>>>> would be ideal, so that we have a chance to at least put code into the
>>>>>> analyze script to examine it.
>>>>>>
>>>>>> For now, I think the hard coded solution in the analyze script is
>>>>>> reasonable.
>>>>>>
>>>>>> However, I think we should print out the name if we find it. It should
>>>>>> be as simple as adding a special case for the configuration section in
>>>>>> MigrationDump.getDict().
>>>>>
>>>>> I did play with adding a separate JSON object for configuration but was
>>>>> torn between whether configuration should have its own JSON object
>>>>> (better if we include extra fields and metadata as above) or to just
>>>>> embed it as a simple "machine" property similar to "page_size". I'll
>>>>> wait until we hear back from David/Juan and submit a v2 accordingly.
>>>>
>>>> Ping again from Juan/David? The analyze-migration.py script is currently
>>>> broken without this patch (or another equivalent) applied.
>>>
>>> Ping^2? FWIW I've added this to the wiki at
>>> http://wiki.qemu.org/Planning/2.5 since without this patch or something
>>> similar applied, this feature is completely broken.
>>
>> Juan, David?
> 
> Isn't this already in ( 96e5c9bc77acef8b7b56cbe23a8a2611feff9e34 ) - or is
> this a different breakage?

Awesome, I didn't see an accepted email :). Sorry for the fuss.


Alex