On 10/23/2017 10:13 AM, Vadim Galitsyn wrote: > 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 migration -- it might be an issue because ‘writeconfig’ data became outdated 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?
I don't think we should expose 'writeconfig' via QMP as long as there is still the chance of inconsistent data being written. And I think we have a lot more issues where existing code abuses QemuOpts in ways that current configuration does not match the original command line, but where you cannot easily expose the current configuration in a way that would be reparsed by the command line into the current state. Therefore, I'm not sure this series is worthwhile. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
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