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Re: [Qemu-devel] [PATCH] ACPI: call acpi_set_pci_info when only acpi ena

From: Bruce Rogers
Subject: Re: [Qemu-devel] [PATCH] ACPI: call acpi_set_pci_info when only acpi enabled
Date: Thu, 27 Apr 2017 10:51:23 -0600

>>> On 4/27/2017 at 10:08 AM, Igor Mammedov <address@hidden> wrote: 
> On Thu, 27 Apr 2017 09:44:31 -0600
> "Bruce Rogers" <address@hidden> wrote:
>> >>> On 4/27/2017 at 03:11 AM, Igor Mammedov <address@hidden> wrote: 
>> > On Wed, 26 Apr 2017 13:07:02 -0600
>> > Bruce Rogers <address@hidden> wrote:
>> > 
>> >> Commit f0c9d64a exposed an issue with the code order in acpi_setup.
>> >> As of that commit, a xenfv machine type guest will no longer start
>> >> if using pci passthrough. Re-order the code in that function to
>> >> allow acpi_set_pci_info to be called before bailing on the other,
>> >> non-related conditions. With this change I can again use pci
>> >> passthrough and xenfv together.
>> >> 
>> >> Signed-off-by: Bruce Rogers <address@hidden>
>> > it doesn't look right,
>> > acpi_set_pci_info() is supposed to affect only ACPI based hotplug
>> > 
>> > could you elaborate more on what's going on and
>> > what error you see at startup?
>> I am using libvirt, driving the creation of the Xen HVM guest via
>> libxl. libxl dynamically attaches the pci device via QMP. In the
>> context of qmp_device_add(), we get a failure in hw/acpi/pcihp.c:
>> acpi_pcihp_device_plug_cb() when it checks for bsel, and errors
>> with the message: "Unsupported bus. Bus doesn't have property
>> 'acpi-pcihp-bsel' set". I guess it wasn't clear from my description
>> that hotplug was involved.
> is dev->hotplugged in acpi_pcihp_device_plug_cb() true at that time?
> the point is that bsel is needed only when there is supporting ACPI code
> and useless otherwise, so acpi_pcihp_device_plug_cb() probably shouldn't
> run under xenfv. I'd try to add compat prop to PIIX4_PM and disable
> acpi_pcihp_device_plug_cb() for xenfv via machine compat property.

So what would be wrong with simply conditionalizing the call to 
 acpi_pcihp_device_plug_cb() with a check for xen in piix4_device_plug_cb()
as follows:

     } else if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
-        acpi_pcihp_device_plug_cb(hotplug_dev, &s->acpi_pci_hotplug, dev, 
+        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);

Wouldn't that be the solution?


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