pci: acpi: ensure that acpi-index is unique

it helps to avoid device naming conflicts when guest OS is
configured to use acpi-index for naming.
Spec ialso says so:

PCI Firmware Specification Revision 3.2
4.6.7.  _DSM for Naming a PCI or PCI Express Device Under Operating Systems
"
Instance number must be unique under \_SB scope. This instance number does not have to
be sequential in a given system configuration.
"

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20210315180102.3008391-4-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/acpi/pcihp.c

@@ -52,6 +52,21 @@ typedef struct AcpiPciHpFind {
     PCIBus *bus;
 } AcpiPciHpFind;
 
+static gint g_cmp_uint32(gconstpointer a, gconstpointer b, gpointer user_data)
+{
+    return a - b;
+}
+
+static GSequence *pci_acpi_index_list(void)
+{
+    static GSequence *used_acpi_index_list;
+
+    if (!used_acpi_index_list) {
+        used_acpi_index_list = g_sequence_new(NULL);
+    }
+    return used_acpi_index_list;
+}
+
 static int acpi_pcihp_get_bsel(PCIBus *bus)
 {
     Error *local_err = NULL;
@@ -277,6 +292,23 @@ void acpi_pcihp_device_pre_plug_cb(HotplugHandler *hotplug_dev,
                    ONBOARD_INDEX_MAX);
         return;
     }
+
+    /*
+     * make sure that acpi-index is unique across all present PCI devices
+     */
+    if (pdev->acpi_index) {
+        GSequence *used_indexes = pci_acpi_index_list();
+
+        if (g_sequence_lookup(used_indexes, GINT_TO_POINTER(pdev->acpi_index),
+                              g_cmp_uint32, NULL)) {
+            error_setg(errp, "a PCI device with acpi-index = %" PRIu32
+                       " already exist", pdev->acpi_index);
+            return;
+        }
+        g_sequence_insert_sorted(used_indexes,
+                                 GINT_TO_POINTER(pdev->acpi_index),
+                                 g_cmp_uint32, NULL);
+    }
 }
 
 void acpi_pcihp_device_plug_cb(HotplugHandler *hotplug_dev, AcpiPciHpState *s,
@@ -315,8 +347,22 @@ void acpi_pcihp_device_plug_cb(HotplugHandler *hotplug_dev, AcpiPciHpState *s,
 void acpi_pcihp_device_unplug_cb(HotplugHandler *hotplug_dev, AcpiPciHpState *s,
                                  DeviceState *dev, Error **errp)
 {
+    PCIDevice *pdev = PCI_DEVICE(dev);
+
     trace_acpi_pci_unplug(PCI_SLOT(PCI_DEVICE(dev)->devfn),
                           acpi_pcihp_get_bsel(pci_get_bus(PCI_DEVICE(dev))));
+
+    /*
+     * clean up acpi-index so it could reused by another device
+     */
+    if (pdev->acpi_index) {
+        GSequence *used_indexes = pci_acpi_index_list();
+
+        g_sequence_remove(g_sequence_lookup(used_indexes,
+                          GINT_TO_POINTER(pdev->acpi_index),
+                          g_cmp_uint32, NULL));
+    }
+
     qdev_unrealize(dev);
 }