qdev: qdev_unplug(): use error_set()

It currently uses qerror_report(), but next commit will convert
the drive_del command to the QAPI and this requires using
error_set().

One particularity of qerror_report() is that it knows when it's
running on monitor context or command-line context and prints the
error message accordingly. error_set() doesn't do this, so we
have to be careful not to drop error messages.

qdev_unplug() has three kinds of usages:

 1. It's called when hot adding a device fails, to undo anything
    that has been done before hitting the error

 2. It's called by function monitor functions like device_del(),
    to unplug a device

 3. It's used by xen_platform.c in a way that doesn't _seem_ to
    be in monitor context

Only item 2 can print an error message to the user, this commit
maintains that.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

hw/pci-hotplug.c

@@ -32,6 +32,7 @@
 #include "virtio-blk.h"
 #include "qemu-config.h"
 #include "blockdev.h"
+#include "error.h"
 
 #if defined(TARGET_I386)
 static PCIDevice *qemu_pci_hot_add_nic(Monitor *mon,
@@ -191,7 +192,7 @@ static PCIDevice *qemu_pci_hot_add_storage(Monitor *mon,
             dev = NULL;
         if (dev && dinfo) {
             if (scsi_hot_add(mon, &dev->qdev, dinfo, 0) != 0) {
-                qdev_unplug(&dev->qdev);
+                qdev_unplug(&dev->qdev, NULL);
                 dev = NULL;
             }
         }
@@ -258,6 +259,7 @@ static int pci_device_hot_remove(Monitor *mon, const char *pci_addr)
     PCIDevice *d;
     int dom, bus;
     unsigned slot;
+    Error *local_err = NULL;
 
     if (pci_read_devaddr(mon, pci_addr, &dom, &bus, &slot)) {
         return -1;
@@ -268,7 +270,15 @@ static int pci_device_hot_remove(Monitor *mon, const char *pci_addr)
         monitor_printf(mon, "slot %d empty\n", slot);
         return -1;
     }
-    return qdev_unplug(&d->qdev);
+
+    qdev_unplug(&d->qdev, &local_err);
+    if (error_is_set(&local_err)) {
+        monitor_printf(mon, "%s\n", error_get_pretty(local_err));
+        error_free(local_err);
+        return -1;
+    }
+
+    return 0;
 }
 
 void do_pci_device_hot_remove(Monitor *mon, const QDict *qdict)

hw/qdev-monitor.c

@@ -573,6 +573,7 @@ int do_device_add(Monitor *mon, const QDict *qdict, QObject **ret_data)
 int do_device_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
 {
     const char *id = qdict_get_str(qdict, "id");
+    Error *local_err = NULL;
     DeviceState *dev;
 
     dev = qdev_find_recursive(sysbus_get_default(), id);
@@ -580,7 +581,15 @@ int do_device_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
         qerror_report(QERR_DEVICE_NOT_FOUND, id);
         return -1;
     }
-    return qdev_unplug(dev);
+
+    qdev_unplug(dev, &local_err);
+    if (error_is_set(&local_err)) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+        return -1;
+    }
+
+    return 0;
 }
 
 void qdev_machine_init(void)

hw/qdev.c

@@ -28,6 +28,7 @@
 #include "net.h"
 #include "qdev.h"
 #include "sysemu.h"
+#include "error.h"
 
 int qdev_hotplug = 0;
 static bool qdev_hot_added = false;
@@ -182,19 +183,22 @@ void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id,
     dev->alias_required_for_version = required_for_version;
 }
 
-int qdev_unplug(DeviceState *dev)
+void qdev_unplug(DeviceState *dev, Error **errp)
 {
     DeviceClass *dc = DEVICE_GET_CLASS(dev);
 
     if (!dev->parent_bus->allow_hotplug) {
-        qerror_report(QERR_BUS_NO_HOTPLUG, dev->parent_bus->name);
-        return -1;
+        error_set(errp, QERR_BUS_NO_HOTPLUG, dev->parent_bus->name);
+        return;
     }
     assert(dc->unplug != NULL);
 
     qdev_hot_removed = true;
 
-    return dc->unplug(dev);
+    if (dc->unplug(dev) < 0) {
+        error_set(errp, QERR_UNDEFINED_ERROR);
+        return;
+    }
 }
 
 static int qdev_reset_one(DeviceState *dev, void *opaque)

hw/qdev.h

@@ -7,6 +7,7 @@
 #include "qemu-option.h"
 #include "qapi/qapi-visit-core.h"
 #include "qemu/object.h"
+#include "error.h"
 
 typedef struct Property Property;
 
@@ -148,7 +149,7 @@ int qdev_init(DeviceState *dev) QEMU_WARN_UNUSED_RESULT;
 void qdev_init_nofail(DeviceState *dev);
 void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id,
                                  int required_for_version);
-int qdev_unplug(DeviceState *dev);
+void qdev_unplug(DeviceState *dev, Error **errp);
 void qdev_free(DeviceState *dev);
 int qdev_simple_unplug_cb(DeviceState *dev);
 void qdev_machine_creation_done(void);

hw/usb/dev-storage.c

@@ -499,7 +499,7 @@ static void usb_msd_password_cb(void *opaque, int err)
         err = usb_device_attach(&s->dev);
 
     if (err)
-        qdev_unplug(&s->dev.qdev);
+        qdev_unplug(&s->dev.qdev, NULL);
 }
 
 static const struct SCSIBusInfo usb_msd_scsi_info = {

hw/xen_platform.c

@@ -87,7 +87,7 @@ static void unplug_nic(PCIBus *b, PCIDevice *d)
 {
     if (pci_get_word(d->config + PCI_CLASS_DEVICE) ==
             PCI_CLASS_NETWORK_ETHERNET) {
-        qdev_unplug(&(d->qdev));
+        qdev_unplug(&(d->qdev), NULL);
     }
 }
 
@@ -100,7 +100,7 @@ static void unplug_disks(PCIBus *b, PCIDevice *d)
 {
     if (pci_get_word(d->config + PCI_CLASS_DEVICE) ==
             PCI_CLASS_STORAGE_IDE) {
-        qdev_unplug(&(d->qdev));
+        qdev_unplug(&(d->qdev), NULL);
     }
 }