Re: [Qemu-devel] [PATCH v3 2/2] s390x/pci: Unplug remaining devices on pcihost reset

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 23 Jan 2019 12:05:39 +0100
Cornelia Huck <cohuck@redhat.com> wrote:

> On Mon, 21 Jan 2019 14:42:49 +0100
> David Hildenbrand <david@redhat.com> wrote:
> 
> > When resetting the guest we should unplug and remove all devices that
> > are still pending. Otherwise the fresh guest will see devices that will
> > suddenly vanish.
> > 
> > Can be triggered e.g. via
> > (hmp) device_add virtio-mouse-pci,id=test
> > (hmp) stop
> > (hmp) device_del test
> > (hmp) system_reset
> > (hmp) c
> > 
> > The device will vanish after roughly 5 minutes. With this patch, the
> > device will vanish on reboot (S390_RESET_EXTERNAL and S390_RESET_REIPL,
> > which reset the pcihost bridge via qemu_devices_reset()). If we want
> > these devices to vanish directly on any reset (S390_RESET_MODIFIED_CLEAR
> > and S390_RESET_LOAD_NORMAL), we have to modify s390_machine_reset(). But
> > I have the feeling that this should not be done for all reset types.
> > 
> > This approach is similar to what's done for acpi PCI hotplug in
> > acpi_pcihp_reset() -> acpi_pcihp_update() ->
> > acpi_pcihp_update_hotplug_bus() -> acpi_pcihp_eject_slot().
> > 
> > s390_pci_generate_plug_event()'s will still be generated, I guess this
> > is not an issue (same thing could happen right now if the timer expires
> > just after reset).  
> 
> I'm wondering what the architecture says regarding those events -- can
> someone with access to the documentation comment?

Ping. Any comments from the IBM folks?

> 
> > 
> > Signed-off-by: David Hildenbrand <david@redhat.com>
> > ---
> >  hw/s390x/s390-pci-bus.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
> > index bc17a8cf65..b70ae25533 100644
> > --- a/hw/s390x/s390-pci-bus.c
> > +++ b/hw/s390x/s390-pci-bus.c
> > @@ -1102,6 +1102,14 @@ static void s390_pcihost_reset(DeviceState *dev)
> >  {
> >      S390pciState *s = S390_PCI_HOST_BRIDGE(dev);
> >      PCIBus *bus = s->parent_obj.bus;
> > +    S390PCIBusDevice *pbdev, *next;
> > +
> > +    /* Unplug all pending devices that were requested to be released */
> > +    QTAILQ_FOREACH_SAFE(pbdev, &s->zpci_devs, link, next) {
> > +        if (pbdev->release_timer) {
> > +            s390_pcihost_timer_cb(pbdev);
> > +        }
> > +    }
> >  
> >      s->bus_no = 0;
> >      pci_for_each_device(bus, pci_bus_num(bus), s390_pci_enumerate_bridge, s);  
>