acpi: fix acpi_index migration

vmstate_acpi_pcihp_use_acpi_index() was expecting AcpiPciHpState
as state but it actually received PIIX4PMState, because
VMSTATE_PCI_HOTPLUG is a macro and not another struct.
So it ended up accessing random pointer, which resulted
in 'false' return value and acpi_index field wasn't ever
sent.

However in 7.0 that pointer de-references to value > 0, and
destination QEMU starts to expect the field which isn't
sent in migratioon stream from older QEMU (6.2 and older).
As result migration fails with:
  qemu-system-x86_64: Missing section footer for 0000:00:01.3/piix4_pm
  qemu-system-x86_64: load of migration failed: Invalid argument

In addition with QEMU-6.2, destination due to not expected
state, also never expects the acpi_index field in migration
stream.

Q35 is not affected as it always sends/expects the field as
long as acpi based PCI hotplug is enabled.

Fix issue by introducing compat knob to never send/expect
acpi_index in migration stream for 6.2 and older PC machine
types and always send it for 7.0 and newer PC machine types.

Diagnosed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Fixes: b32bd76 ("pci: introduce acpi-index property for PCI device")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/932
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/acpi/acpi-pci-hotplug-stub.c

@@ -41,7 +41,3 @@ void acpi_pcihp_reset(AcpiPciHpState *s, bool acpihp_root_off)
     return;
 }
 
-bool vmstate_acpi_pcihp_use_acpi_index(void *opaque, int version_id)
-{
-    return false;
-}

hw/acpi/pcihp.c

@@ -554,12 +554,6 @@ void acpi_pcihp_init(Object *owner, AcpiPciHpState *s, PCIBus *root_bus,
                                    OBJ_PROP_FLAG_READ);
 }
 
-bool vmstate_acpi_pcihp_use_acpi_index(void *opaque, int version_id)
-{
-     AcpiPciHpState *s = opaque;
-     return s->acpi_index;
-}
-
 const VMStateDescription vmstate_acpi_pcihp_pci_status = {
     .name = "acpi_pcihp_pci_status",
     .version_id = 1,

hw/acpi/piix4.c

@@ -82,6 +82,7 @@ struct PIIX4PMState {
     AcpiPciHpState acpi_pci_hotplug;
     bool use_acpi_hotplug_bridge;
     bool use_acpi_root_pci_hotplug;
+    bool not_migrate_acpi_index;
 
     uint8_t disable_s3;
     uint8_t disable_s4;
@@ -267,6 +268,16 @@ static bool piix4_vmstate_need_smbus(void *opaque, int version_id)
     return pm_smbus_vmstate_needed();
 }
 
+/*
+ * This is a fudge to turn off the acpi_index field,
+ * whose test was always broken on piix4 with 6.2 and older machine types.
+ */
+static bool vmstate_test_migrate_acpi_index(void *opaque, int version_id)
+{
+    PIIX4PMState *s = PIIX4_PM(opaque);
+    return s->use_acpi_hotplug_bridge && !s->not_migrate_acpi_index;
+}
+
 /* qemu-kvm 1.2 uses version 3 but advertised as 2
  * To support incoming qemu-kvm 1.2 migration, change version_id
  * and minimum_version_id to 2 below (which breaks migration from
@@ -297,7 +308,7 @@ static const VMStateDescription vmstate_acpi = {
             struct AcpiPciHpPciStatus),
         VMSTATE_PCI_HOTPLUG(acpi_pci_hotplug, PIIX4PMState,
                             vmstate_test_use_acpi_hotplug_bridge,
-                            vmstate_acpi_pcihp_use_acpi_index),
+                            vmstate_test_migrate_acpi_index),
         VMSTATE_END_OF_LIST()
     },
     .subsections = (const VMStateDescription*[]) {
@@ -652,6 +663,8 @@ static Property piix4_pm_properties[] = {
     DEFINE_PROP_BOOL("memory-hotplug-support", PIIX4PMState,
                      acpi_memory_hotplug.is_enabled, true),
     DEFINE_PROP_BOOL("smm-compat", PIIX4PMState, smm_compat, false),
+    DEFINE_PROP_BOOL("x-not-migrate-acpi-index", PIIX4PMState,
+                      not_migrate_acpi_index, false),
     DEFINE_PROP_END_OF_LIST(),
 };
 

hw/core/machine.c

@@ -37,7 +37,9 @@
 #include "hw/virtio/virtio.h"
 #include "hw/virtio/virtio-pci.h"
 
-GlobalProperty hw_compat_6_2[] = {};
+GlobalProperty hw_compat_6_2[] = {
+    { "PIIX4_PM", "x-not-migrate-acpi-index", "on"},
+};
 const size_t hw_compat_6_2_len = G_N_ELEMENTS(hw_compat_6_2);
 
 GlobalProperty hw_compat_6_1[] = {

include/hw/acpi/pcihp.h

@@ -73,8 +73,6 @@ void acpi_pcihp_reset(AcpiPciHpState *s, bool acpihp_root_off);
 
 extern const VMStateDescription vmstate_acpi_pcihp_pci_status;
 
-bool vmstate_acpi_pcihp_use_acpi_index(void *opaque, int version_id);
-
 #define VMSTATE_PCI_HOTPLUG(pcihp, state, test_pcihp, test_acpi_index) \
         VMSTATE_UINT32_TEST(pcihp.hotplug_select, state, \
                             test_pcihp), \