s390x/pci: make hot-unplug handler smoother

The current implementation of hot-unplug handler is abrupt. Any pci
operation will be just rejected if pci device is unconfigured. Thus a
pci device can not be reset or destroyed in a right, smooth and safe
way.

Improve this as follows:
- Notify the guest via a HP_EVENT_DECONFIGURE_REQUEST(0x303) event in
  the unplug handler, giving it a chance to deconfigure the device via
  sclp and allowing us to continue hot-unplug afterwards.
- Set up a timer that will generate the HP_EVENT_CONFIGURE_TO_STBRES
  (0x304) event as before if the guest did not react after an adequate
  time.
Signed-off-by: NYi Min Zhao <zyimin@linux.vnet.ibm.com>
Reviewed-by: NPierre Morel <pmorel@linux.vnet.ibm.com>
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>

hw/s390x/s390-pci-bus.c

@@ -192,6 +192,10 @@ void s390_pci_sclp_deconfigure(SCCB *sccb)
         }
         pbdev->state = ZPCI_FS_STANDBY;
         rc = SCLP_RC_NORMAL_COMPLETION;
+
+        if (pbdev->release_timer) {
+            qdev_unplug(DEVICE(pbdev->pdev), NULL);
+        }
     }
 out:
     psccb->header.response_code = cpu_to_be16(rc);
@@ -679,6 +683,23 @@ static void s390_pcihost_hot_plug(HotplugHandler *hotplug_dev,
     }
 }
 
+static void s390_pcihost_timer_cb(void *opaque)
+{
+    S390PCIBusDevice *pbdev = opaque;
+
+    if (pbdev->summary_ind) {
+        pci_dereg_irqs(pbdev);
+    }
+    if (pbdev->iommu_enabled) {
+        pci_dereg_ioat(pbdev);
+    }
+
+    pbdev->state = ZPCI_FS_STANDBY;
+    s390_pci_generate_plug_event(HP_EVENT_CONFIGURED_TO_STBRES,
+                                 pbdev->fh, pbdev->fid);
+    qdev_unplug(DEVICE(pbdev), NULL);
+}
+
 static void s390_pcihost_hot_unplug(HotplugHandler *hotplug_dev,
                                     DeviceState *dev, Error **errp)
 {
@@ -712,8 +733,20 @@ static void s390_pcihost_hot_unplug(HotplugHandler *hotplug_dev,
     case ZPCI_FS_STANDBY:
         break;
     default:
-        s390_pci_generate_plug_event(HP_EVENT_CONFIGURED_TO_STBRES,
+        s390_pci_generate_plug_event(HP_EVENT_DECONFIGURE_REQUEST,
                                      pbdev->fh, pbdev->fid);
+        pbdev->release_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
+                                            s390_pcihost_timer_cb,
+                                            pbdev);
+        timer_mod(pbdev->release_timer,
+                  qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + HOT_UNPLUG_TIMEOUT);
+        return;
+    }
+
+    if (pbdev->release_timer && timer_pending(pbdev->release_timer)) {
+        timer_del(pbdev->release_timer);
+        timer_free(pbdev->release_timer);
+        pbdev->release_timer = NULL;
     }
 
     s390_pci_generate_plug_event(HP_EVENT_STANDBY_TO_RESERVED,

hw/s390x/s390-pci-bus.h

@@ -34,6 +34,7 @@
 #define ZPCI_MAX_UID 0xffff
 #define UID_UNDEFINED 0
 #define UID_CHECKING_ENABLED 0x01
+#define HOT_UNPLUG_TIMEOUT (NANOSECONDS_PER_SECOND * 60 * 5)
 
 #define S390_PCI_HOST_BRIDGE(obj) \
     OBJECT_CHECK(S390pciState, (obj), TYPE_S390_PCI_HOST_BRIDGE)
@@ -44,6 +45,7 @@
 
 #define HP_EVENT_TO_CONFIGURED        0x0301
 #define HP_EVENT_RESERVED_TO_STANDBY  0x0302
+#define HP_EVENT_DECONFIGURE_REQUEST  0x0303
 #define HP_EVENT_CONFIGURED_TO_STBRES 0x0304
 #define HP_EVENT_STANDBY_TO_RESERVED  0x0308
 
@@ -283,6 +285,7 @@ typedef struct S390PCIBusDevice {
     MemoryRegion iommu_mr;
     IndAddr *summary_ind;
     IndAddr *indicator;
+    QEMUTimer *release_timer;
 } S390PCIBusDevice;
 
 typedef struct S390PCIBus {