Re: [Qemu-devel] [RFC 12/42] pc: initialize legacy hotplug only for 2.6 and older machine types

[Eduardo Habkost]

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 <address@hidden> 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 <address@hidden>  
> > > 
> > > 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 believe we should at least warn people (early, during
initialization) that their configuration don't make sense
anymore.

-- 
Eduardo