On Fri, Apr 27, 2018 at 05:05:15PM +0200, Igor Mammedov wrote: > This option allows pausing QEMU in the new RUN_STATE_PRECONFIG state, > allowing the configuration of QEMU from QMP before the machine jumps > into board initialization code of machine_run_board_init() > > The intent is to allow management to query machine state and additionally > configure it using previous query results within one QEMU instance > (i.e. eliminate the need to start QEMU twice, 1st to query board specific > parameters and 2nd for actual VM start using query results for > additional parameters). > > The new option complements -S option and could be used with or without > it. The difference is that -S pauses QEMU when the machine is completely > initialized with all devices wired up and ready to execute guest code > (QEMU needs only to unpause VCPUs to let guest execute its code), > while the "preconfig" option pauses QEMU early before board specific init > callback (machine_run_board_init) is executed and allows the configuration > of machine parameters which will be used by board init code.
> When early introspection/configuration is done, command 'exit-preconfig' > should be used to exit RUN_STATE_PRECONFIG and transition to the next > requested state (i.e. if -S is used then QEMU will pause the second > time when board/device initialization is completed or start guest > execution if -S isn't provided on CLI) If we're going to introduce this --preconfig facility I would very much like us to ensure that we do *not* need to continue to also use -S. IOW it would be nice to essentially consider --preconfig a better impl of -S and stop using -S, perhaps even deprecating it for removal. What logical things does QEMU do after exiting pre-config stage, but before starting CPUs that might be dependency for mgmt apps that would neccessitate using both --preconfig and -S ? Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
