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

[Christian Borntraeger]

While looking into this series,

I realized that Davids patch

commit acd05785e48c01edb2c4f4d014d28478b5f19fb5
Author:     David Matlack <dmatlack@xxxxxxxxxx>
AuthorDate: Fri Apr 17 15:14:46 2020 -0700
Commit:     Paolo Bonzini <pbonzini@xxxxxxxxxx>
CommitDate: Fri Apr 24 12:53:17 2020 -0400

    kvm: add capability for halt polling

broke the possibility for an admin to disable halt polling for already running KVM guests.
In past times doing
echo 0 > /sys/module/kvm/parameters/halt_poll_ns

stopped polling system wide.
Now all KVM guests will use the halt_poll_ns value that was active during startup - even those that do not use KVM_CAP_HALT_POLL.

I guess this was not intended?