Re: [PATCH v14 01/11] s390x/cpu topology: adding s390 specificities to CPU topology

[Thomas Huth]

On 16/01/2023 18.28, Pierre Morel wrote:
> On 1/13/23 17:58, Nina Schoetterl-Glausch wrote:
> > On Thu, 2023-01-05 at 15:53 +0100, Pierre Morel wrote:
> > > S390 adds two new SMP levels, drawers and books to the CPU
> > > topology.
> > > The S390 CPU have specific toplogy features like dedication
> > > and polarity to give to the guest indications on the host
> > > vCPUs scheduling and help the guest take the best decisions
> > > on the scheduling of threads on the vCPUs.
> > >
> > > Let us provide the SMP properties with books and drawers levels
> > > and S390 CPU with dedication and polarity,
> > >
> > > Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> > > ---
...
> PTF([01]) are no performance bottle neck and the number of CPU is likely to 
> be small, even a maximum of 248 is possible KVM warns above 16 CPU so the 
> loop for setting all CPU inside PTF interception is not very problematic I 
> think.

KVM warns if you try to use more than the number of physical CPUs that you 
have, not at hard-coded 16 CPUs. So if you've got an LPAR with 248 CPUs, 
it's perfectly fine to use also 248 CPUs for your guest.

 Thomas