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Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already presen
From: |
Bharata B Rao |
Subject: |
Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present |
Date: |
Thu, 10 Mar 2016 20:15:23 +0530 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Thu, Mar 10, 2016 at 11:39:46AM +0100, Igor Mammedov wrote:
> On Thu, 10 Mar 2016 11:32:44 +0530
> Bharata B Rao <address@hidden> wrote:
>
> > On Thu, Mar 10, 2016 at 04:22:43PM +1100, David Gibson wrote:
> > > On Wed, Mar 09, 2016 at 11:07:40AM +0100, Igor Mammedov wrote:
> > > > On Tue, 8 Mar 2016 20:04:12 +0530
> > > > Bharata B Rao <address@hidden> wrote:
> > > >
> > > > > On Tue, Mar 08, 2016 at 02:18:14PM +0100, Igor Mammedov wrote:
> > > > > > Signed-off-by: Igor Mammedov <address@hidden>
> > > > > > ---
> > > > > > replaced link set check removed in previous patch
> > > > > > ---
> > > > > > hw/ppc/spapr.c | 26 ++++++++++++++++++++++----
> > > > > > 1 file changed, 22 insertions(+), 4 deletions(-)
> > > > > >
> > > > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > > > > index 6890a44..db33c29 100644
> > > > > > --- a/hw/ppc/spapr.c
> > > > > > +++ b/hw/ppc/spapr.c
> > > > > > @@ -2297,6 +2297,27 @@ void
> > > > > > *spapr_populate_hotplug_cpu_dt(DeviceState *dev, CPUState *cs,
> > > > > > return fdt;
> > > > > > }
> > > > > >
> > > > > > +static void spapr_machine_device_pre_plug(HotplugHandler
> > > > > > *hotplug_dev,
> > > > > > + DeviceState *dev, Error
> > > > > > **errp)
> > > > > > +{
> > > > > > + sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(hotplug_dev);
> > > > > > + sPAPRMachineState *spapr = SPAPR_MACHINE(hotplug_dev);
> > > > > > +
> > > > > > + if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_CPU_CORE)) {
> > > > > > + int core = object_property_get_int(OBJECT(dev),
> > > > > > CPU_CORE_ID_PROP,
> > > > > > + &error_abort);
> > > > > > +
> > > > > > + if (!smc->dr_cpu_enabled && dev->hotplugged) {
> > > > > > + error_setg(errp, "CPU hotplug not supported for this
> > > > > > machine");
> > > > > > + return;
> > > > > > + }
> > > > > > + if (spapr->cores[core]) {
> > > > > > + error_setg(errp, "core %d is already present", core);
> > > > > > + return;
> > > > > > + }
> > > > >
> > > > > Wondering why can't we do the above check from core's realizefn and
> > > > > fail
> > > > > the core hotplug from realizefn ?
> > > > that's rather simple, in ideal QOM world child shouldn't
> > > > poke into parents internal if it could be helped.
> > > > So hook provides responsibility separation where
> > > > board/or something else(HotplugHandler) can do a necessary
> > > > wiring of a component which is being hotplugged, without
> > > > forcing hotplugged device being aware about it.
> > >
> > > Oh.. yes. Sorry, somehow I got confused and thought you were
> > > suggesting a 'pre_realize()' method on the *object* rather than a
> > > pre_plug hotplughandler hook.
> > >
> > > > That's what HotplugHandler->plug callback is doing for
> > > > post realize and HotplugHandler->pre_plug will do similar
> > > > thing but allowing board to execute preliminary tasks
> > > > (like check/set properties, amend its internal state)
> > > > before object is realized.
> > >
> > > > That will make realize() cleaner as it won't have to hack
> > > > into data it shouldn't and would prevent us calling unrealize()
> > > > if we were to check it later at HotplugHandler->plug time.
> > > > (i.e. realize() won't even have a chance to introduce side
> > > > effects that should be undone with unlealize())
> > >
> > > Hmm.. how big a deal is it to roll back from the existing plug()
> > > handler?
> realize shouldn't complete without error if object properties are
> wrong /for ex: i.e. you create kvm vcpu thread, configure it
> as already existing vcpu and have a lot fun afterwards/.
>
> For example: now on x86 we do duplicate CPU check wrong way
> by checking for duplicate of apic property from CPU code by
> looping through existing CPUs. Instead it would be much cleaner
> to move that check to machine which owns apic id assignment
> and make it check for duplicate in pre_plug() handler.
>
>
> > Since plug() handler is post-realize, rolling back involves
> > deleting the threads of the core we created and finally deleting the core
> > itself.
> Even rolling back will leave some after effects, like created
> KVM VCPU thread which can't be deleted and who know what else.
>
> >We aleady do this kind of roll back when core hotplug is attemptedi
> > on machine type version that don't support hotplug.
> that's seems to be wrong, it shouldn't even come to cpu.realize()
> if hotplug is not supported.
Hmm that's how we dis-allowed memory hotplug on machine type versions
that don't support memory hotplug, i,e., we failed hotplug from
->plug() handler. So ->pre_plug() seems to be the ideal place for
such early failures ?
Regards,
Bharata.
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2 1/5] QMP: add query-hotpluggable-cpus, (continued)
- [Qemu-ppc] [PATCH v2 5/5] spapr: implement query-hotpluggable-cpus QMP command, Igor Mammedov, 2016/03/08
- [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present, Igor Mammedov, 2016/03/08
- Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present, Bharata B Rao, 2016/03/08
- Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present, Igor Mammedov, 2016/03/09
- Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present, David Gibson, 2016/03/10
- Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present, Bharata B Rao, 2016/03/10
- Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present, Igor Mammedov, 2016/03/10
- Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present,
Bharata B Rao <=
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2 4/5] spapr: check if cpu core is already present, Igor Mammedov, 2016/03/11
- Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present, David Gibson, 2016/03/15
- Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present, Igor Mammedov, 2016/03/15
- Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present, David Gibson, 2016/03/15
- Re: [Qemu-ppc] [PATCH v2 4/5] spapr: check if cpu core is already present, Igor Mammedov, 2016/03/16