From: Igor Mammedov <imammedo@redhat.com>

piix4_pm_reset() is calling acpi_pcihp_reset() when ACPI PCI hotplug
is disabled, which leads to assigning BSEL properties to bridges on path
   acpi_set_bsel()
       ...
       if (qbus_is_hotpluggable(BUS(bus))) {
          // above happens to be true by default (though it's SHPC hotplug handler)
          // set BSEL
       }

At the moment the issue is masked by the fact that we use not only BSEL,
to decide if we should generated hoplug AML but also pcihp_bridge_en knob.
However the later patches will drop dependency on pcihp_bridge_en,
and use only BSEL exclusively to decide if hotplug AML for slots should be built,
which exposes issue.

We should not ever call acpi_pcihp_reset() if ACPI PCI hotplug is disabled,
make it so.

PS:
 * Q35 does the right thing (i.e. it calls acpi_pcihp_reset only when pcihp is enabled)
 * the issue also makes acpi_pcihp_update() logic run on SHPC enabled bridges,
   which seems to be harmless

Fixes: 3d7e78aa777 ("Introduce a new flag for i440fx to disable PCI hotplug on the root bus")
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20230112140312.3096331-11-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/acpi/piix4.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
index 2ab4930f11..724294b378 100644
--- a/hw/acpi/piix4.c
+++ b/hw/acpi/piix4.c
@@ -304,7 +304,9 @@ static void piix4_pm_reset(DeviceState *dev)
     acpi_update_sci(&s->ar, s->irq);
 
     pm_io_space_update(s);
-    acpi_pcihp_reset(&s->acpi_pci_hotplug, !s->use_acpi_root_pci_hotplug);
+    if (s->use_acpi_hotplug_bridge || s->use_acpi_root_pci_hotplug) {
+        acpi_pcihp_reset(&s->acpi_pci_hotplug, !s->use_acpi_root_pci_hotplug);
+    }
 }
 
 static void piix4_pm_powerdown_req(Notifier *n, void *opaque)
-- 
MST