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

[Michael S. Tsirkin]

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 <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 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.

> -- 
> Eduardo