On 27/09/21 16:59, Sean Christopherson wrote:
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?
No, but...
I would go so far as to say that halt_poll_ns should be a hard limit on
the capability
... this would not be a good idea I think. Anything that wants to do a
lot of polling can just do "for (;;)".
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
* just make halt_poll_ns read-only.
Paolo
