On Aug 29, 2020, 13:42 +0530, Ani Sinha <ani@anisinha.ca>, wrote:
When ACPI hotplug for the root bus is disabled, the bsel property for that
bus is not set. Please see the following commit:
3d7e78aa7777f ("Introduce a new flag for i440fx to disable PCI hotplug on the root bus").
As a result, when acpi_pcihp_find_hotplug_bus() is called
with bsel set to 0, it may return the root bus. This would be wrong since the
root bus is not hotpluggable. In general, this can potentially happen to other
buses as well.
In this patch, we fix the issue in this function by checking if the bus returned
by the function is actually hotpluggable. If not, we simply return NULL. This
avoids the scenario where we are actually returning a non-hotpluggable bus.
Signed-off-by: Ani Sinha <ani@anisinha.ca>
---
hw/acpi/pcihp.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c
index 39b1f74442..f148e73c89 100644
--- a/hw/acpi/pcihp.c
+++ b/hw/acpi/pcihp.c
@@ -147,6 +147,21 @@ static PCIBus *acpi_pcihp_find_hotplug_bus(AcpiPciHpState *s, int bsel)
if (!bsel && !find.bus) {
find.bus = s->root;
}
+
+ /*
+ * Check if find.bus is actually hotpluggable. If bsel is set to
+ * NULL for example on the root bus in order to make it
+ * non-hotpluggable, find.bus will match the root bus when bsel
+ * is 0. See acpi_pcihp_test_hotplug_bus() above. Since the
+ * bus is not hotpluggable however, we should not select the bus.
+ * Instead, we should set find.bus to NULL in that case. In the check
+ * below, we generalize this case for all buses, not just the root bus.
+ * The callers of this function check for a null return value and
+ * handle them appropriately.
+ */
+ if (!qbus_is_hotpluggable(BUS(find.bus))) {
+ find.bus = NULL;
+ }
return find.bus;
}
--
2.17.1