Re: [Qemu-devel] [PATCH v3 0/5] Migration Deciphering aid

[Amit Shah]

On (Tue) 20 Jan 2015 [11:54:50], Alexander Graf wrote:
> 
> 
> On 20.01.15 11:31, Amit Shah wrote:
> > On (Fri) 26 Dec 2014 [15:42:43], Alexander Graf wrote:
> >> Migration is a black hole to most people. One of the biggest reasons for
> >> this is that its protocol is a secret, undocumented sauce of code rolling
> >> around random parts of the QEMU code base.
> >>
> >> But what if we simply exposed the description of how the format looks like
> >> alongside the actual migration stream? This is what this patch set does.
> >>
> >> It adds a new section that comes after the end of stream marker (so that it
> >> doesn't slow down migration) that contains a JSON description of the device
> >> state description.
> >>
> >> Along with this patch set also comes a python script that can read said 
> >> JSON
> >> from a migration dump and decipher the device state and ram contents of the
> >> migration dump using it.
> >>
> >> With this, you can now fully examine all glorious details that go over the
> >> wire when virtual machine state gets dumped, such as during live migration.
> >>
> >> We discussed the approach taken here during KVM Forum 2013. Originally, my 
> >> idea
> >> was to include a special device that contains the JSON data which can be 
> >> enabled
> >> on demand. Anthony suggested however to just always include the 
> >> description data
> >> after the end marker which I think is a great idea.
> >>
> >>   Example decoded migration: http://csgraf.de/mig/mig.txt
> >>   Example migration description: http://csgraf.de/mig/mig.desc.txt
> >>   Presentation: https://www.youtube.com/watch?v=iq1x40Qsrew
> >>   Slides: https://www.dropbox.com/s/otp2pk2n3g087zp/Live%20Migration.pdf
> > 
> > Nice to finally see this!
> > 
> > I guess you have a v4 coming soon?
> 
> Yeah, I was just waiting on a bit more review :)

I have no problem with the series :-)

In fact I forgot to note - the vmstate checker can use the json output
introduced here :)

                Amit