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

[Stefano Stabellini]

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 <address@hidden>
> ---
>  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?

I realize that I should have suggested this earlier, sorry about that.