Re: [libvirt] [RFC] kvm: x86: export vCPU halted state to sysfs
On Fri, 2 Feb 2018 16:49:54 -0500
Luiz Capitulino <lcapitulino(a)redhat.com> wrote:
On Fri, 2 Feb 2018 18:41:44 -0200
Eduardo Habkost <ehabkost(a)redhat.com> wrote:
> On Fri, Feb 02, 2018 at 03:19:45PM -0500, Luiz Capitulino wrote:
> > On Fri, 2 Feb 2018 18:09:12 -0200
> > Eduardo Habkost <ehabkost(a)redhat.com> wrote:
> [...]
> > > Your plan above covers what will happen when using newer QEMU
> > > versions, but libvirt still needs to work sanely if running QEMU
> > > 2.11. My suggestion is that libvirt do not run query-cpus to ask
> > > for the "halted" field on any architecture except s390.
> >
> > My current plan is to ask libvirt to completely remove query-cpus
> > usage, independent of the arch and use the new command instead.
>
> This would be a regression for people running QEMU 2.11 on s390.
libvirt could use query-cpus on s390 if the new command is not
available.
Btw, even on s390 query-cpus runs run_on_cpu(), which is what
causes vCPUs to go to user-space. So, s390 should suffer the same
performance problem. Pick your regression.
>
> (But maybe it would be an acceptable regression? Viktor, what do
> you think? Are there production releases of management systems
> that already rely on vcpu.<n>.halted?)
>