Re: [PATCH v3 4/4] x86/kvm: add boot parameter for setting max number of vcpus per guest

From: Sean Christopherson
Date: Thu Nov 18 2021 - 10:46:44 EST


On Thu, Nov 18, 2021, Juergen Gross wrote:
> On 18.11.21 16:05, Sean Christopherson wrote:
> > Which is a good segue into pointing out that if a module param is added, it needs
> > to be sanity checked against a KVM-defined max. The admin may be trusted to some
> > extent, but there is zero reason to let userspace set max_vcspus to 4 billion.
> > At that point, it really is just a param vs. capability question.
>
> I agree. Capping it at e.g. 65536 would probably be a good idea.

Any reason to choose 65536 in particular? Why not cap it at the upper limit of
NR_CPUS_RANGE_END / MAXSMP, which is currently 8192?