On Wed, 13 Jul 2016 10:19:00 +0200
Igor Mammedov <imamm...@redhat.com> wrote:
> On Wed, 13 Jul 2016 09:42:54 +0200
> Igor Mammedov <imamm...@redhat.com> wrote:
>
> > On Wed, 13 Jul 2016 12:20:20 +0530
> > Bharata B Rao <bhar...@linux.vnet.ibm.com> wrote:
> >
> > > If CPU core addition or removal is allowed in random order leading to
> > > holes in the core id range (and hence in the cpu_index range), migration
> > > can fail as migration with holes in cpu_index range isn't yet handled
> > > correctly.
> > >
> > > Prevent this situation by enforcing the addition in contiguous order
> > > and removal in LIFO order so that we never end up with holes in
> > > cpu_index range.
> > Adding this limitation looks better than adding migration_id as
> > it will allow libvirt to use the current -numa cpus=... while
> > doing the same amount of guess work as it does now.
> >
> > Similar patch for x86 won't be so simple as cpu-add can add cpus
> > with gaps (breaking migration at that), so I'd need to keep it
> > that way with some compat code, but that shouldn't be issue.
> CCing Peter for libvirt's opinion on this turn of events
didn't actually CCed him :/
>
> >
> >
> > > Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com>
> > > ---
> > > While there is work in progress to support migration when there are holes
> > > in cpu_index range resulting from out-of-order plug or unplug, this patch
> > > is intended as a last resort if no easy, risk-free and elegant solution
> > > emerges before 2.7 dev cycle ends.
> > >
> > > hw/ppc/spapr_cpu_core.c | 21 ++++++++++++++++++++-
> > > 1 file changed, 20 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> > > index bc52b3c..4bfc96b 100644
> > > --- a/hw/ppc/spapr_cpu_core.c
> > > +++ b/hw/ppc/spapr_cpu_core.c
> > > @@ -126,12 +126,23 @@ static void spapr_core_release(DeviceState *dev,
> > > void *opaque)
> > > void spapr_core_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
> > > Error **errp)
> > > {
> > > + sPAPRMachineState *spapr = SPAPR_MACHINE(OBJECT(hotplug_dev));
> > > CPUCore *cc = CPU_CORE(dev);
> > > sPAPRDRConnector *drc =
> > > spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU,
> > > cc->core_id);
> > > sPAPRDRConnectorClass *drck;
> > > Error *local_err = NULL;
> > > + int smt = kvmppc_smt_threads();
> > > + int index = cc->core_id / smt;
> > > + int spapr_max_cores = max_cpus / smp_threads;
> > > + int i;
> > >
> > > + for (i = spapr_max_cores - 1; i > index; i--) {
> > > + if (spapr->cores[i]) {
> > > + error_setg(errp, "core-id %d should be removed first", i *
> > > smt);
> > > + return;
> > > + }
> > > + }
> > > g_assert(drc);
> > >
> > > drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> > > @@ -214,7 +225,7 @@ void spapr_core_pre_plug(HotplugHandler *hotplug_dev,
> > > DeviceState *dev,
> > > sPAPRMachineClass *smc =
> > > SPAPR_MACHINE_GET_CLASS(OBJECT(hotplug_dev));
> > > sPAPRMachineState *spapr = SPAPR_MACHINE(OBJECT(hotplug_dev));
> > > int spapr_max_cores = max_cpus / smp_threads;
> > > - int index;
> > > + int index, i;
> > > int smt = kvmppc_smt_threads();
> > > Error *local_err = NULL;
> > > CPUCore *cc = CPU_CORE(dev);
> > > @@ -252,6 +263,14 @@ void spapr_core_pre_plug(HotplugHandler
> > > *hotplug_dev, DeviceState *dev,
> > > goto out;
> > > }
> > >
> > > + for (i = 0; i < index; i++) {
> > > + if (!spapr->cores[i]) {
> > > + error_setg(&local_err, "core-id %d should be added first",
> > > + i * smt);
> > > + goto out;
> > > + }
> > > + }
> > > +
> > > out:
> > > g_free(base_core_type);
> > > error_propagate(errp, local_err);
> >
> >
>
>
