[PATCH v3] hw/acpi: add an assertion check for non-null return from acpi_get_i386_pci_host

[Ani Sinha]

All existing code using acpi_get_i386_pci_host() checks for a non-null
return value from this function call. Instead of returning early when the value
returned is NULL, assert instead. Since there are only two possible host buses
for i386 - q35 and i440fx, a null value return from the function does not make
sense in most cases and is likely an error situation.

Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug")

Signed-off-by: Ani Sinha <a...@anisinha.ca>
---
 hw/acpi/pcihp.c      |  8 ++++++++
 hw/i386/acpi-build.c | 15 ++++++---------
 2 files changed, 14 insertions(+), 9 deletions(-)

changelog:
v1: initial patch
v2: removed comment addition - that can be sent as a separate patch.
v3: added assertion for null host values for all cases except one.

diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c
index f4d706e47d..054ee8cbc5 100644
--- a/hw/acpi/pcihp.c
+++ b/hw/acpi/pcihp.c
@@ -116,6 +116,12 @@ static void acpi_set_pci_info(void)
     bsel_is_set = true;
 
     if (!host) {
+        /*
+         * This function can be eventually called from
+         * qemu_devices_reset() -> acpi_pcihp_reset() even
+         * for architectures other than i386. Hence, we need
+         * to ignore null values for host here.
+         */
         return;
     }
 
@@ -136,6 +142,8 @@ static void acpi_pcihp_disable_root_bus(void)
         return;
     }
 
+    assert(host);
+
     bus = PCI_HOST_BRIDGE(host)->bus;
     if (bus) {
         /* setting the hotplug handler to NULL makes the bus non-hotpluggable 
*/
diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 17836149fe..83fb1d55c0 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -321,9 +321,7 @@ static void acpi_get_pci_holes(Range *hole, Range *hole64)
 
     pci_host = acpi_get_i386_pci_host();
 
-    if (!pci_host) {
-        return;
-    }
+    assert(pci_host);
 
     range_set_bounds1(hole,
                       object_property_get_uint(pci_host,
@@ -1769,9 +1767,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
 
         pci_host = acpi_get_i386_pci_host();
 
-        if (pci_host) {
-            bus = PCI_HOST_BRIDGE(pci_host)->bus;
-        }
+        assert(pci_host);
+
+        bus = PCI_HOST_BRIDGE(pci_host)->bus;
 
         if (bus) {
             Aml *scope = aml_scope("PCI0");
@@ -2389,9 +2387,8 @@ static bool acpi_get_mcfg(AcpiMcfgInfo *mcfg)
     QObject *o;
 
     pci_host = acpi_get_i386_pci_host();
-    if (!pci_host) {
-        return false;
-    }
+
+    assert(pci_host);
 
     o = object_property_get_qobject(pci_host, PCIE_HOST_MCFG_BASE, NULL);
     if (!o) {
-- 
2.25.1