Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV spinlock

[Peter Zijlstra]

On Mon, Sep 04, 2017 at 04:28:36PM +0200, Oscar Salvador wrote:
> This is just a resend of Waiman Long's patch.
> I could not find why it was not merged to upstream, so I thought
> to give it another chance.
> What follows is what Waiman Long wrote.
> 
> Xen has an kernel command line argument "xen_nopvspin" to disable
> paravirtual spinlocks. This patch adds a similar "kvm_nopvspin"
> argument to disable paravirtual spinlocks for KVM. This can be useful
> for testing as well as allowing administrators to choose unfair lock
> for their KVM guests if they want to.

For testing its trivial to hack your kernel and I don't feel this is
something an Admin can make reasonable decisions about.

So why? In general less knobs is better.