[Qemu-devel] Re: [RFC] allow multi-core guests: introduce cores= option to -cpu

[Alexander Graf]

On 04.07.2009, at 17:25, Avi Kivity wrote:

> On 07/03/2009 05:41 PM, Andre Przywara wrote:
> > Hi,
> >
> > currently SMP guests happen to see<n>  vCPUs as<n>  different  
> > sockets.
> > Some guests (Windows comes to mind) have license restrictions and  
> > refuse
> > to run on multi-socket machines.
> > So lets introduce a "cores=" parameter to the -cpu option to let  
> > the user
> > specify the number of _cores_ the guest should see.
> >
> > This patch has not been tested with all corner cases, so I just  
> > want to
> > hear your comments whether
> > a) we need such an option  and
> > b) you like this particular approach.
> >
> > Applying this qemu.git patch to qemu-kvm.git fixes Windows SMP boot  
> > on
> > some versions, I successfully tried up to -smp 16 -cpu host,cores=8  
> > with
> > WindowsXP Pro.
>
> I thought of using -smp [processors=]2,cores=4,threads=2 (for a  
> total of 16 threads), but I think it makes more sense with -cpu.

I actually think putting this in -smp makes more sense. -cpu really  
shouldn't need to be touched by normal users and as long as you can  
either -cpu host or -cpu safe that should be enough.

But then again maybe we should replace -smp with something more useful  
like -numa where you'd then specify #CPUs, #cores, mem-cpu connection,  
etc.

Alex