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@redhat.com> 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@redhat.com> 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@redhat.com>
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