From a6dae62ef051773c0198f8ebd47a79d8f1157000 Mon Sep 17 00:00:00 2001
From: Serhii Popovych <spopovyc@redhat.com>
Date: Thu, 9 Nov 2017 15:30:03 +0100
Subject: [PATCH 3/7] qdev: store DeviceState's canonical path to use when
 unparenting

RH-Author: Serhii Popovych <spopovyc@redhat.com>
Message-id: <1510241405-20597-2-git-send-email-spopovyc@redhat.com>
Patchwork-id: 77632
O-Subject: [RHV7.5 qemu-kvm-rhev PATCH 1/3] qdev: store DeviceState's canonical path to use when unparenting
Bugzilla: 1445460
RH-Acked-by: David Gibson <dgibson@redhat.com>
RH-Acked-by: Thomas Huth <thuth@redhat.com>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

From: Michael Roth <mdroth@linux.vnet.ibm.com>

device_unparent(dev, ...) is called when a device is unparented,
either directly, or as a result of a parent device being
finalized, and handles some final cleanup for the device. Part
of this includes emiting a DEVICE_DELETED QMP event to notify
management, which includes the device's path in the composition
tree as provided by object_get_canonical_path().

object_get_canonical_path() assumes the device is still connected
to the machine/root container, and will assert otherwise, but
in some situations this isn't the case:

If the parent is finalized as a result of object_unparent(), it
will still be attached to the composition tree at the time any
children are unparented as a result of that same call to
object_unparent(). However, in some cases, object_unparent()
will complete without finalizing the parent device, due to
lingering references that won't be released till some time later.
One such example is if the parent has MemoryRegion children (which
take a ref on their parent), who in turn have AddressSpace's (which
take a ref on their regions), since those AddressSpaces get cleaned
up asynchronously by the RCU thread.

In this case qdev:device_unparent() may be called for a child Device
that no longer has a path to the root/machine container, causing
object_get_canonical_path() to assert.

Fix this by storing the canonical path during realize() so the
information will still be available for device_unparent() in such
cases.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20171016222315.407-2-mdroth@linux.vnet.ibm.com>
[Clear dev->canonical_path at the post_realize_fail label, which is
 cleaner.  Suggested by David Gibson. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

(cherry picked from commit 04162f8f4bcf8c9ae2422def4357289b44208c8c)
Signed-off-by: Serhii Popovych <spopovyc@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/core/qdev.c         | 17 ++++++++++++++---
 include/hw/qdev-core.h |  1 +
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 606ab53..0019a49 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -928,6 +928,13 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
             goto post_realize_fail;
         }
 
+        /*
+         * always free/re-initialize here since the value cannot be cleaned up
+         * in device_unrealize due to its usage later on in the unplug path
+         */
+        g_free(dev->canonical_path);
+        dev->canonical_path = object_get_canonical_path(OBJECT(dev));
+
         if (qdev_get_vmsd(dev)) {
             if (vmstate_register_with_alias_id(dev, -1, qdev_get_vmsd(dev), dev,
                                                dev->instance_id_alias,
@@ -984,6 +991,8 @@ child_realize_fail:
     }
 
 post_realize_fail:
+    g_free(dev->canonical_path);
+    dev->canonical_path = NULL;
     if (dc->unrealize) {
         dc->unrealize(dev, NULL);
     }
@@ -1102,10 +1111,12 @@ static void device_unparent(Object *obj)
 
     /* Only send event if the device had been completely realized */
     if (dev->pending_deleted_event) {
-        gchar *path = object_get_canonical_path(OBJECT(dev));
+        g_assert(dev->canonical_path);
 
-        qapi_event_send_device_deleted(!!dev->id, dev->id, path, &error_abort);
-        g_free(path);
+        qapi_event_send_device_deleted(!!dev->id, dev->id, dev->canonical_path,
+                                       &error_abort);
+        g_free(dev->canonical_path);
+        dev->canonical_path = NULL;
     }
 
     qemu_opts_del(dev->opts);
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index ae31728..9237b68 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -153,6 +153,7 @@ struct DeviceState {
     /*< public >*/
 
     const char *id;
+    char *canonical_path;
     bool realized;
     bool pending_deleted_event;
     QemuOpts *opts;
-- 
1.8.3.1