[Qemu-devel] QMP, HMP: introduce 'writeconfig' command

[Vadim Galitsyn]

Hi Guys,

This thread is a continuation of discussion started in
http://lists.nongnu.org/archive/html/qemu-devel/2017-02/msg03182.html.

This series introduces ‘writeconfig’ command support for QMP and HMP monitors. 
This functionality might be useful for live migration for cases when guest 
configuration was modified in runtime (for example as a result of hot- 
plug/unplug operations) and actual Qemu command line no longer reflects setup 
exposed to guest.

Original series has ‘qemu_opts’ patch as well 
(http://lists.nongnu.org/archive/html/qemu-devel/2017-02/msg03183.html) because 
HMP’s ‘object_add’ result was not reflected in ‘writeconfig’ output. Later I 
found that QMP’s ‘object-add’ has the same issue. Anyway, I don’t include 
‘qemu_opts’ patches here because Markus mentioned (here 
http://lists.nongnu.org/archive/html/qemu-devel/2017-02/msg03476.html) that 
this functionality is going to be reworked in some future and such patches 
might collide with the rework process.

Markus, could you please post if you have an update on this topic? Current 
‘master’ branch (9993c82dc2f5ce58b41d708b765e1a717ad4281d) still has the issue.

Also, Markus mentioned that once configuration was changed during live 
migration -- it might be an issue because ‘writeconfig’ data became outdated 
(and might be make sense to think about to embed this data into migration 
stream itself). In the same time David said that this is another problem which 
is unrelated to this patch series. What is your current opinion on this topic? 
Can we consider these patches to be included into ‘master’ taking into account 
that not all configuration is dumped by ‘writeconfig’ (‘object_add’ problem), 
but this can be fixed later?

Best regards,
Vadim