On Mon, Jul 18, 2016 at 04:01:18PM +0200, Peter Krempa wrote: > On Mon, Jul 18, 2016 at 19:19:20 +1000, David Gibson wrote: > > We've recently added a new device_add based cpu hotplug > > implementation, with the spapr machine type being the first user. In > > order to overcome the limitations of the old cpu_add interface, it > > works very differently. That's going to require a new interface in > > libvirt to properly use the new interface in qemu, which will in turn > > require work further up the stack to make use of it. > > > > While that's certainly necessary in the long run, it would be nice if > > we could have at least something working with the old cpu_add > > interface. This patch is an attempt to do so. > > > > This patch implements cpu-add on machines which don't support it > > directly but which do support the query-hotpluggable-cpus interface. > > Essentially, > > cpu-add <n> > > will be treated as a device_add of the n-th entry in the list provided > > by query-hotpluggable-cpus. > > Does this have the same implications when libvirt will need to re-create > a matching qemu process for migration target? (Will we need to specify > -device cpu,... for every CPU 'entity' added this way on the command > line?) > > When using cpu_add libvirt recreates the process by just increasing the > number of active cpus specified via '-smp'. > > In case where libvirt would need to add the -device entries this would > create just problems with compatibility. Libvirt needs to add XML > specification of the cpus in order to allow tracking which cpus need to > be added on the commandline.
Is this compatability handling any different from how libvirt already handles memory specified by -m and by -device pc-dimm ? Isn't cpus specified by -smp and by -device kind of comparable to the memory case ? Regards, Bharata.
