Re: [PATCH 0/3] KVM: Tie MWAIT/HLT/PAUSE interception to initially disabled capabilities

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Nov 29, 2017 at 02:20:34AM +0200, Michael S. Tsirkin wrote:
> On Wed, Nov 29, 2017 at 01:07:32AM +0100, Paolo Bonzini wrote:
> > On 28/11/2017 15:08, Michael S. Tsirkin wrote:
> > > I think guests still want some way to halt when
> > > giving up CPU for a long time.
> > > 
> > > If you are not worried about guests entering low power states,
> > > then you only need MWAIT and maybe PAUSE.
> > > 
> > > HLT within guest only makes sense if you do not want to
> > > allow guest to enter power state.
> > > 
> > > If you don't exit on any of these, you want some other way
> > > to actually halt the VCPU.
> > 
> > If you want to do something in userspace, send a signal.  Otherwise, it
> > doesn't really matter (if you have a dedicated physical CPU) whether the
> > task is runnable or not, as long as the CPU isn't in C0.
> > 
> > Paolo
> 
> If VCPU wants to give up its timeslice, how is it supposed to do it
> if all exits are blocked?

All this doesn't mean the patch can't be applied. But I think
it would be handy to add another way to exit to host
and stop until an interrupt. E.g. an access to a special
address could do it.

> -- 
> MST