[libvirt] [RFC 12/42] pc: initialize legacy hotplug only for 2.6 and older machine types

Igor Mammedov imammedo at redhat.com
Thu May 12 13:20:51 UTC 2016

On Thu, 12 May 2016 13:04:23 +0200
Peter Krempa <pkrempa at redhat.com> wrote:

> On Thu, May 12, 2016 at 07:52:23 -0300, Eduardo Habkost wrote:
> > I don't think we should do that, unless users already had time to
> > update their scripts and libvirt had time to implement code
> > supporting the new method.
> > 
> > I believe libvirt (and people's scripts) use maxcpus only when
> > they want CPU hotplug, so making max_cpus > smp_cpus enable CPU
> > hotplug implicitly would probably solve the compatibility issue.  
> Libvirt uses maxcpus only if the configuration explicitly has less
> active cpus than the maximum number. This option would be the best IMO.
> > If we want to deprecate the use of maxcpus to enable CPU hotplug,
> > then we can make it print a warning for a few releases, so people
> > have time to update their code.  
> At that point libvirt also needs a way to detect that the new argument
> is supported by qemu, so we can start passing it on the command line
> basically every time we now pass 'maxcpus'.
> The warning will get most probably ignored by people using libvirt as
> the stdout/err of qemu is not visible to them.
Ok, to make things less complicated I'll drop machine.cpu-hotplug
and leave it always enabled as it used to be and as Michael suggested.

I'll drop following patches: 12, 13, 14, 20, 23 and respin series

> Peter

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