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

[Alexander Graf <agraf@suse.de>]

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 <mark.cave-ayland@ilande.co.uk>
>>>>> ---
>>>>>  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?


Alex