Re: disabling halt polling broken? (was Re: [PATCH 00/14] KVM: Halt-polling fixes, cleanups and a new stat)

From: Paolo Bonzini
Date: Mon Sep 27 2021 - 13:29:27 EST

On Mon, Sep 27, 2021 at 5:17 PM Christian Borntraeger
<borntraeger@xxxxxxxxxx> wrote:
> > So I think there are two possibilities that makes sense:
> >
> > * track what is using KVM_CAP_HALT_POLL, and make writes to halt_poll_ns follow that
> what about using halt_poll_ns for those VMs that did not uses KVM_CAP_HALT_POLL and the private number for those that did.

Yes, that's what I meant. David pointed out that doesn't allow you to
disable halt polling altogether, but for that you can always ask each
VM's userspace one by one, or just not use KVM_CAP_HALT_POLL. (Also, I
don't know about Google's usecase, but mine was actually more about
using KVM_CAP_HALT_POLL to *disable* halt polling on some VMs!).