On Thu, May 12, 2016 at 12:29:55PM +0200, Igor Mammedov wrote: > On Thu, 12 May 2016 10:07:03 +0300 > "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > > On Wed, May 11, 2016 at 08:28:59PM -0300, Eduardo Habkost wrote: > > > On Thu, May 12, 2016 at 12:51:55AM +0300, Michael S. Tsirkin wrote: > > > > On Wed, May 11, 2016 at 03:50:39PM +0200, Igor Mammedov wrote: > > > > > On Tue, 10 May 2016 17:24:14 -0300 > > > > > Eduardo Habkost <ehabkost@xxxxxxxxxx> wrote: > > > > > > > > > > > On Mon, May 02, 2016 at 02:33:21PM +0200, Igor Mammedov wrote: > > > > > > > on old machine types CPU hotplug was uncondtionally > > > > > > > enabled since it was introduced, consuming IO ports > > > > > > > and providing AML regardles of whether it was actually > > > > > > > in use or not. Keep it so for 2.6 and older machines. > > > > > > > > > > > > > > New machine types will have an option to turn CPU > > > > > > > hotplug on if it's needed while by default it stays > > > > > > > disabled not consuming extra RAM/IO resources. > > > > > > > > > > > > > > Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx> > > > > > > > > > > > > What if people are using "-machine pc -smp N,max_cpus=M"? > > > > > > Shouldn't we at least warning about missing CPU hotplug support > > > > > > when using just "max_cpus" with no "cpu-hotplug=on" with pc-2.7 > > > > > > and newer? > > > > > Yep, I'll add it on next respin. > > > > > Would hard error better than warning? > > > > > > > > Most people don't need cpu hotplug, attempts > > > > to hotplug fail, should be enough. > > > > > > People who don't need CPU hotplug shouldn't be using the max_cpus > > > option. > > > > I agree. > > > > > I believe we should at least warn people (early, during > > > initialization) that their configuration don't make sense > > > anymore. > > > > I think we should try to keep old command line working > > if we can. > this patch won't break old command line for old machine types, > but for new machine type users would need to fix it > and be explicit if they want cpu-hotplug. 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. 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. -- Eduardo -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list