qdev: unplug blocker for devices

Add blocker to prevent hot-unplug of devices

TYPE_VFIO_USER_SERVER, which is introduced shortly, attaches itself to a
PCIDevice on which it depends. If the attached PCIDevice gets removed
while the server in use, it could cause it crash. To prevent this,
TYPE_VFIO_USER_SERVER adds an unplug blocker for the PCIDevice.

Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: c41ef80b7cc063314d629737bed2159e5713f2e0.1655151679.git.jag.raman@oracle.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 84f3019..0806d8f 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -468,6 +468,28 @@ char *qdev_get_dev_path(DeviceState *dev)
     return NULL;
 }
 
+void qdev_add_unplug_blocker(DeviceState *dev, Error *reason)
+{
+    dev->unplug_blockers = g_slist_prepend(dev->unplug_blockers, reason);
+}
+
+void qdev_del_unplug_blocker(DeviceState *dev, Error *reason)
+{
+    dev->unplug_blockers = g_slist_remove(dev->unplug_blockers, reason);
+}
+
+bool qdev_unplug_blocked(DeviceState *dev, Error **errp)
+{
+    ERRP_GUARD();
+
+    if (dev->unplug_blockers) {
+        error_propagate(errp, error_copy(dev->unplug_blockers->data));
+        return true;
+    }
+
+    return false;
+}
+
 static bool device_get_realized(Object *obj, Error **errp)
 {
     DeviceState *dev = DEVICE(obj);
@@ -704,6 +726,8 @@ static void device_finalize(Object *obj)
 
     DeviceState *dev = DEVICE(obj);
 
+    g_assert(!dev->unplug_blockers);
+
     QLIST_FOREACH_SAFE(ngl, &dev->gpios, node, next) {
         QLIST_REMOVE(ngl, node);
         qemu_free_irqs(ngl->in, ngl->num_in);