Re: [Qemu-devel] [PATCH v4 0/4] Migration Deciphering aid

[Amit Shah]

On (Thu) 22 Jan 2015 [15:01:36], 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.

'make check' fails with this series applied:

migration/vmstate.o: In function `vmstate_save_state':
qemu/migration/vmstate.c:289: undefined reference to `json_prop_str'
qemu/migration/vmstate.c:290: undefined reference to `json_prop_int'
qemu/migration/vmstate.c:291: undefined reference to `json_start_array'
migration/vmstate.o: In function `vmsd_desc_field_start':
qemu/migration/vmstate.c:245: undefined reference to `json_start_object'
qemu/migration/vmstate.c:246: undefined reference to `json_prop_str'
qemu/migration/vmstate.c:249: undefined reference to `json_prop_int'
qemu/migration/vmstate.c:254: undefined reference to `json_prop_str'
migration/vmstate.o: In function `vmsd_desc_field_end':
qemu/migration/vmstate.c:275: undefined reference to `json_prop_int'
qemu/migration/vmstate.c:276: undefined reference to `json_end_object'
migration/vmstate.o: In function `vmstate_save_state':
qemu/migration/vmstate.c:337: undefined reference to `json_end_array'
migration/vmstate.o: In function `vmstate_subsection_save':
qemu/migration/vmstate.c:423: undefined reference to `json_start_object'
qemu/migration/vmstate.c:434: undefined reference to `json_end_object'
qemu/migration/vmstate.c:419: undefined reference to `json_start_array'
migration/vmstate.o: In function `vmsd_desc_field_start':
qemu/migration/vmstate.c:251: undefined reference to `json_prop_int'
migration/vmstate.o: In function `vmsd_desc_field_end':
qemu/migration/vmstate.c:272: undefined reference to `json_end_object'
migration/vmstate.o: In function `vmsd_desc_field_start':
qemu/migration/vmstate.c:257: undefined reference to `json_start_object'
migration/vmstate.o: In function `vmstate_subsection_save':
qemu/migration/vmstate.c:441: undefined reference to `json_end_array'
collect2: error: ld returned 1 exit status
qemu/rules.mak:122: recipe for target 'tests/test-vmstate' failed
make: *** [tests/test-vmstate] Error 1

                Amit