Re: [Qemu-devel] [PATCH] ACPI: don't call acpi_pcihp_device_plug_cb on xen

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 27 Apr 2017 14:09:11 -0700 (PDT)
Stefano Stabellini <sstabellini@kernel.org> wrote:

> On Thu, 27 Apr 2017, Bruce Rogers wrote:
> > Commit f0c9d64a exposed the issue that with a xenfv machine using
> > pci passthrough, acpi cpi hotplug code was being executed by mistake.
> > Guard calls to acpi_pcihp_device_plug_cb (and corresponding
> > acpi_pcihp_device_unplug_cb) with a check for xen_enabled(). Without
> > this check I am seeing an error that the bus doesn't have the
> > acpi-pcihp-bsel property set.
> > 
> > Signed-off-by: Bruce Rogers <brogers@suse.com>
> > ---
> >  hw/acpi/piix4.c | 11 ++++++++---
> >  1 file changed, 8 insertions(+), 3 deletions(-)
> > 
> > diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
> > index a553a7e..c409374 100644
> > --- a/hw/acpi/piix4.c
> > +++ b/hw/acpi/piix4.c
> > @@ -385,7 +385,10 @@ static void piix4_device_plug_cb(HotplugHandler *hotplug_dev,
> >                                  dev, errp);
> >          }
> >      } else if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
> > -        acpi_pcihp_device_plug_cb(hotplug_dev, &s->acpi_pci_hotplug, dev, errp);
> > +        if (!xen_enabled()) {
> > +            acpi_pcihp_device_plug_cb(hotplug_dev, &s->acpi_pci_hotplug, dev,
> > +                                      errp);
> > +        }
> >      } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
> >          if (s->cpu_hotplug_legacy) {
> >              legacy_acpi_cpu_plug_cb(hotplug_dev, &s->gpe_cpu, dev, errp);
> > @@ -408,8 +411,10 @@ static void piix4_device_unplug_request_cb(HotplugHandler *hotplug_dev,
> >          acpi_memory_unplug_request_cb(hotplug_dev, &s->acpi_memory_hotplug,
> >                                        dev, errp);
> >      } else if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
> > -        acpi_pcihp_device_unplug_cb(hotplug_dev, &s->acpi_pci_hotplug, dev,
> > -                                    errp);
> > +        if (!xen_enabled()) {
> > +            acpi_pcihp_device_unplug_cb(hotplug_dev, &s->acpi_pci_hotplug, dev,
> > +                                        errp);
> > +        }
> >      } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU) &&
> >                 !s->cpu_hotplug_legacy) {
> >          acpi_cpu_unplug_request_cb(hotplug_dev, &s->cpuhp_state, dev, errp);  
> 
> Wouldn't it be better to simply turn the error_setg("Unsupported bus...)
> in acpi_pcihp_device_plug_cb and acpi_pcihp_device_unplug_cb into debug
> printfs? After all, from this description it is clear that they are not
> an error conditions. PCI Passthough works correctly, right?
it's error condition if acpi hotplug is in use, so we should keep it