pci: do not respond config requests after PCI device eject

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2224964

In migration with VF failover, Windows guest and ACPI hot
unplug we do not need to satisfy config requests, otherwise
the guest immediately detects the device and brings up its
driver. Many network VF's are stuck on the guest PCI bus after
the migration.

Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
Message-Id: <20230728084049.191454-1-yuri.benditovich@daynix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/pci/pci_host.c

@@ -62,6 +62,17 @@ static void pci_adjust_config_limit(PCIBus *bus, uint32_t *limit)
     }
 }
 
+static bool is_pci_dev_ejected(PCIDevice *pci_dev)
+{
+    /*
+     * device unplug was requested and the guest acked it,
+     * so we stop responding config accesses even if the
+     * device is not deleted (failover flow)
+     */
+    return pci_dev && pci_dev->partially_hotplugged &&
+           !pci_dev->qdev.pending_deleted_event;
+}
+
 void pci_host_config_write_common(PCIDevice *pci_dev, uint32_t addr,
                                   uint32_t limit, uint32_t val, uint32_t len)
 {
@@ -75,7 +86,7 @@ void pci_host_config_write_common(PCIDevice *pci_dev, uint32_t addr,
      * allowing direct removal of unexposed functions.
      */
     if ((pci_dev->qdev.hotplugged && !pci_get_function_0(pci_dev)) ||
-        !pci_dev->has_power) {
+        !pci_dev->has_power || is_pci_dev_ejected(pci_dev)) {
         return;
     }
 
@@ -100,7 +111,7 @@ uint32_t pci_host_config_read_common(PCIDevice *pci_dev, uint32_t addr,
      * allowing direct removal of unexposed functions.
      */
     if ((pci_dev->qdev.hotplugged && !pci_get_function_0(pci_dev)) ||
-        !pci_dev->has_power) {
+        !pci_dev->has_power || is_pci_dev_ejected(pci_dev)) {
         return ~0x0;
     }