On Mon, 23 Jul 2018 13:36:36 +0200
Cédric Le Goater <c...@kaod.org> wrote:
> On 07/12/2018 12:01 PM, Greg Kurz wrote:
> > Recent cleanup in commit a028dd423ee6 dropped the ICPStateClass::reset
> > handler. It is now up to child ICP classes to call the DeviceClass::reset
> > handler of the parent class, thanks to device_class_set_parent_reset().
> > This is a better object programming pattern,
>
> I think that the device_class_set_parent* routines just obfuscate a little
> more the object programming approach of QEMU.
>
Really ?
> > but unfortunately it causes QEMU to crash during CPU hotplug:
>
> I guess I did not try that :/ Would it be complex to add a spapr unit test
> for CPU hotplug ? It would be useful.
>
Actually, there's one in tests/cpu-plug-test.c but it runs with
accel=qtest, and thus it doesn't exercise the KVM ICP code.
I've patched it to use accel=kvm:tcg on pseries: it would have caught
the SEGV indeed. There's another problem though: QEMU sometimes stays
stuck in kvm_vcpu_ioctl() in 'disk sleep' state, causing the test
to hang until someone kills QEMU with SIGKILL.
Not sure yet what's happening...
> > (qemu) device_add host-spapr-cpu-core,id=core1,core-id=1
> > Segmentation fault (core dumped)
> >
> > When the hotplug path tries to reset the ICP device, we end up calling:
> >
> > static void icp_kvm_reset(DeviceState *dev)
> > {
> > ICPStateClass *icpc = ICP_GET_CLASS(dev);
> >
> > icpc->parent_reset(dev);
> >
> > but icpc->parent_reset is NULL... This happens because icp_kvm_class_init()
> > calls:
> >
> > device_class_set_parent_reset(dc, icp_kvm_reset,
> > &icpc->parent_reset);
> >
> > but dc->reset, ie, DeviceClass::reset for the TYPE_ICP type, is
> > itself NULL.>
> > This patch hence sets DeviceClass::reset for the TYPE_ICP type to
> > point to icp_reset(). It then registers a reset handler that calls
> > DeviceClass::reset. If the ICP subtype has configured its own reset
> > handler with device_class_set_parent_reset(), this ensures it will
> > be called first and it can then call ICPStateClass::parent_reset
> > safely. This fixes the reset path for the TYPE_KVM_ICP type, which
> > is the only subtype that defines its own reset function.
>
> So, now, isn't ICP reset called twice on KVM ?
>
No. We have one path for cold plugged CPUS:
#0 icp_reset (dev=0x113db100) at
/home/greg/Work/qemu/qemu-spapr/hw/intc/xics.c:296
#1 0x0000000010146d0c in icp_kvm_reset (dev=0x113db100) at
/home/greg/Work/qemu/qemu-spapr/hw/intc/xics_kvm.c:121
#2 0x00000000101434b0 in icp_reset_handler (dev=0x113db100) at
/home/greg/Work/qemu/qemu-spapr/hw/intc/xics.c:310
#3 0x00000000104c3744 in qemu_devices_reset () at
/home/greg/Work/qemu/qemu-spapr/hw/core/reset.c:69
#4 0x00000000101d61c8 in spapr_machine_reset () at
/home/greg/Work/qemu/qemu-spapr/hw/ppc/spapr.c:1639
#5 0x00000000103de654 in qemu_system_reset (reason=SHUTDOWN_CAUSE_NONE) at
/home/greg/Work/qemu/qemu-spapr/vl.c:1645
...
and one path for hot plugged CPUs:
#0 icp_reset (dev=0x11268e40) at
/home/greg/Work/qemu/qemu-spapr/hw/intc/xics.c:296
#1 0x0000000010146d0c in icp_kvm_reset (dev=0x11268e40) at
/home/greg/Work/qemu/qemu-spapr/hw/intc/xics_kvm.c:121
#2 0x00000000104be300 in device_reset (dev=0x11268e40) at
/home/greg/Work/qemu/qemu-spapr/hw/core/qdev.c:1082
#3 0x00000000104bd62c in device_set_realized (obj=0x11268e40, value=true,
errp=0x7fffffffcfa8) at /home/greg/Work/qemu/qemu-spapr/hw/core/qdev.c:867
...
> Anyway, we can sort that out if necessary.
>
> Thanks,
>
> C.
>
> > Reported-by: Satheesh Rajendran <sathn...@linux.vnet.ibm.com>
> > Suggested-by: David Gibson <da...@gibson.dropbear.id.au>
> > Fixes: a028dd423ee6dfd091a8c63028240832bf10f671
> > Signed-off-by: Greg Kurz <gr...@kaod.org>
> > ---
> > hw/intc/xics.c | 14 +++++++++++---
> > 1 file changed, 11 insertions(+), 3 deletions(-)
> >
> > diff --git a/hw/intc/xics.c b/hw/intc/xics.c
> > index b9f1a3c97214..c90c893228dc 100644
> > --- a/hw/intc/xics.c
> > +++ b/hw/intc/xics.c
> > @@ -291,7 +291,7 @@ static const VMStateDescription vmstate_icp_server = {
> > },
> > };
> >
> > -static void icp_reset(void *dev)
> > +static void icp_reset(DeviceState *dev)
> > {
> > ICPState *icp = ICP(dev);
> >
> > @@ -303,6 +303,13 @@ static void icp_reset(void *dev)
> > qemu_set_irq(icp->output, 0);
> > }
> >
> > +static void icp_reset_handler(void *dev)
> > +{
> > + DeviceClass *dc = DEVICE_GET_CLASS(dev);
> > +
> > + dc->reset(dev);
> > +}
> > +
> > static void icp_realize(DeviceState *dev, Error **errp)
> > {
> > ICPState *icp = ICP(dev);
> > @@ -345,7 +352,7 @@ static void icp_realize(DeviceState *dev, Error **errp)
> > return;
> > }
> >
> > - qemu_register_reset(icp_reset, dev);
> > + qemu_register_reset(icp_reset_handler, dev);
> > vmstate_register(NULL, icp->cs->cpu_index, &vmstate_icp_server, icp);
> > }
> >
> > @@ -354,7 +361,7 @@ static void icp_unrealize(DeviceState *dev, Error
> > **errp)
> > ICPState *icp = ICP(dev);
> >
> > vmstate_unregister(NULL, &vmstate_icp_server, icp);
> > - qemu_unregister_reset(icp_reset, dev);
> > + qemu_unregister_reset(icp_reset_handler, dev);
> > }
> >
> > static void icp_class_init(ObjectClass *klass, void *data)
> > @@ -363,6 +370,7 @@ static void icp_class_init(ObjectClass *klass, void
> > *data)
> >
> > dc->realize = icp_realize;
> > dc->unrealize = icp_unrealize;
> > + dc->reset = icp_reset;
> > }
> >
> > static const TypeInfo icp_info = {
> >
>
